Sample records for albite

  1. In situ viscosity measurements of albite melt under high pressure

    CERN Document Server

    Funakoshi, K I; Terasaki, H


    The viscosities of albite (NaAlSi sub 3 O sub 8) melt under high pressures have been measured using an x-ray radiography falling sphere method with synchrotron radiation. This method has enabled us to determine the precise sinking velocity directly. Recent experiments of albite melt showed the presence of a viscosity minimum around 5 GPa (Poe et al 1997 Science 276 1245, Mori et al 2000 Earth Planet. Sci. Lett. 175 87). We present the results for albite melt up to 5.2 GPa at 1600 and 1700 deg. C. The viscosity minimum is clearly observed to be around 4.5 GPa, and it might be explained not by the change of the compression mechanism in albite melt but by change of the phase itself.

  2. Radioluminescence and thermoluminescence of albite at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Can, N., E-mail: [Physics Department, Faculty of Arts and Sciences, Celal Bayar University, 45140 Muradiye-Manisa (Turkey); Garcia-Guinea, J. [Museo Nacional Ciencias Naturales, Jose Gutierrez Abascal 2, Madrid 28006 (Spain); Kibar, R.; Cetin, A.; Ayvacikli, M. [Physics Department, Faculty of Arts and Sciences, Celal Bayar University, 45140 Muradiye-Manisa (Turkey); Townsend, P.D. [Science and Technology, University of Sussex, Brighton BN1 9QH, England (United Kingdom)


    Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi{sub 3}O{sub 8} and the plagioclases (NaAlSi{sub 3}O{sub 8}-CaAl{sub 2}Si{sub 2}O{sub 8}) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na{sup +}, Mn{sup 2+} or Fe{sup 3+} ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. - Highlights: > TL and RL spectra in albite were presented for different orientations. > There are 4 emission bands that are considered to arise from complexes of intrinsic. > RL data at low temperature for albite is distorted by contributions from TL sites. > This indicates the potential problem for analysis of low temperature RL.

  3. Radioluminescence and thermoluminescence of albite at low temperature

    International Nuclear Information System (INIS)

    Feldspar as an archaeological and geological natural material for dating and retrospective dosimetry is receiving more and more attention because of its useful luminescence properties. In this study, the 25-280 K thermoluminescence (TL) and radioluminescence (RL) spectra in albite, which is a component of the two main feldspar series, the alkali feldspar (Na, K)AlSi3O8 and the plagioclases (NaAlSi3O8-CaAl2Si2O8) have been presented for aliquots along (001) and (010) crystallographic orientations. There are four main emission bands that are considered to arise from complexes of intrinsic defects linked in larger complexes with impurities such as Na+, Mn2+ or Fe3+ ions. The consequence of their association is to produce different luminescence efficiencies that produce wavelength sensitive TL curves. Radioluminescence data at low temperature for albites is distorted by contributions from the TL sites, even when the RL is run in a cooling cycle. This indicates the potential for a far more general problem for analysis of low temperature RL in insulating materials. - Highlights: → TL and RL spectra in albite were presented for different orientations. → There are 4 emission bands that are considered to arise from complexes of intrinsic. → RL data at low temperature for albite is distorted by contributions from TL sites. → This indicates the potential problem for analysis of low temperature RL.

  4. Crystal structure refinement of reedmergnerite, the boron analog of albite (United States)

    Clark, J.R.; Appleman, D.E.


    Ordering of boron in a feldspar crystallographic site T1(0) has been found in reedmergnerite, which has silicon-oxygen and sodium-oxygen distances comparable to those in isostructural low albite. If a simple ionic model is assumed, calculated bond strengths yield a considerable charge imbalance in reedmergnerite, an indication of the inadequacy of the model with respect to these complex structures and of the speculative nature of conclusions based on such a model.

  5. Electrical conductivity of albite melts at high pressures (United States)

    Ni, H.; Keppler, H.


    High electrical conductivity observed from magnetotelluric/geomagnetic depth sounding is probably associated with the presence of silicate melts. We investigated electrical conductivity of albite melts, both anhydrous and hydrous with 2.0-5.4 wt% H2O, at 300-1500°C and 0.9-1.8 GPa in a piston-cylinder apparatus. Anhydrous glass was synthesized by fusing oxides and carbonates in 1-bar furnace, and hydrous glasses were prepared by fusing the mixture of glass powder and water in a TZM vessel. A glass cylinder was enclosed between a platinum rod as inner electrode and a Pt-Rh capsule as outer electrode. Platinum wires were used to connect both electrodes to a Solartron 1260 impedance analyzer for conductivity measurements at 3M to 3 HZ. A type-S thermocouple, which was separated from the conductivity circuit, was used to monitor temperature. Furthermore, a Mo foil was employed to reduce the interference from heating circuit. Experimental results demonstrate that the electrical conductivity of albite melt follows an Arrhenius relationship in both glass (1100°C) region. In both cases, electrical conductivity increases with water content but decreases with pressure. In the glass region, electrical conductivity can be modelled as logσ = 3.5734 + 0.25534C - (4264+160.43P)/T, where σ is conductivity in S/m, C is water content in wt%, P is pressure in GPa, and T is temperature in K. The above expression implies an activation energy of 82 kJ/mol and an activation volume of 3.1 cc/mol. In the liquid region, electrical conductivity can be modelled as logσ = 2.6906 + 0.065915C - (2339+371.97P)/T, which implies an activation energy of 45 kJ/mol and an activation volume of 7.1 cc/mol. The dominating conduction mechanism in albite melts is suggested to be the motion of sodium cation.

  6. Effects of different UV exposures on the thermoluminescence of high albite


    Correcher, Virgilio; García Guinea, Javier; Delgado Peris, Antonio


    High albite can be used as a new UV dosimeter. Heated natural albite posseses a special property: it has strong thermoluminescence (TL) blue emissions under UV radiation. The TL glow curves of high albite after different times of UV exposure show PhotoTransferred ThermoLuminescence (PTTL) from deeps traps (345oC - 450oC) to shallow traps (150oC) which can be used to store UV damage. The point of inflexion of the process occurs after one hour under UV radiation, the low temperature peaks start...

  7. Authigenic albite formation due to water-rock interactions - Case study: Magnus oilfield (UK, Northern North Sea) (United States)

    Mu, Nana; Fu, Yunjiao; Schulz, Hans-Martin; van Berk, Wolfgang


    It is the aim of this contribution to test whether organic-inorganic interactions could induce the formation of authigenic albite. This concept and related results are being compared with modelling scenarios which are purely based on inorganic geochemical reactions. In order to unravel the pathway of authigenic albite formation, this paper presents results of a multidisciplinary study from imaging, geochemistry, mineralogy, and hydrogeochemical modelling. The Jurassic reservoir sandstones of the Magnus oilfield (UK, North Sea) were chosen as a test site. Albite occurs with 4-18 wt.% in the Magnus sandstones and its contents vary with depth. However, albite contents increase with increasing K-feldspar contents and decreasing grain size. It occurs in three forms: (1) as lamellae in perthite, (2) as overgrowth on/in corroded feldspar, and, (3) as cloudy replacing albite patches in K-feldspar. The albite overgrowth has the highest chemical purity (100% albite) whilst albite lamellae and replacing albite patches are slightly less pure (containing 1-4% anorthite). Albite appears non-altered, and has a euhedral morphology and dull cathodoluminescence. It commonly co-occurs with corroded K-feldspar grains. The precipitation of diagenetic albite in the Magnus sandstones is attributed to deep burial 80 Ma ago and may have continued until today at temperatures between 90-120 °C. The results of hydrogeochemical modelling offer two possible pathways for the authigenic albite formation: (1) Dissolution of unstable minerals (such as kaolinite and chalcedony) coupled to reduction of ferric iron minerals by products generated during oil generation, migration and degradation; (2) Dissolution of non-end member feldspar, such as K-feldspar with 10% albite, coupled to illite formation can account for trace amounts of albite due to an elevated Na+/K+ activity ratio in the pore water.

  8. Uranium deposits in the metamorphic basement of the Rouergue massif. Genesis and extension of related albitization processes

    International Nuclear Information System (INIS)

    Albitization processes in the Rouergue metamorphic basement, probably Permian aged is evidenced. Late development of uranium orebodies occured within albitized zones. The detection of the latter serves as a highly valuable indirect guide for prospecting this type of deposits in a metamorphic basement

  9. Influence of the amount containing spodumene or albite on the sintering of a triaxial ceramic

    International Nuclear Information System (INIS)

    In this study, we investigated the properties of porcelain stoneware, made with albite or spodumene. The amount of the feldspar in the compositions ranged from 15 to 30% by weight. Specimens were pressed and sintered at 1000, 1100, 1200 and 1280 °C with an isotherm of 1 hour at the maximum temperature. The samples were characterized by analysis of the fracture surface using scanning electron microscopy and the vitrification curves, showing both the linear shrinkage and porosity in relation to the sintering temperature. The best results were obtained for samples containing 30% spodumene sintered at 1280 °C, with a linear shrinkage of 9.97% and porosity of 13.28%, while the corresponding results of samples containing 30% albite were 10.13% and 12.17%, respectively. It is concluded that the use of spodumene in the production of porcelain stoneware is viable, resulting in comparable properties. (author)

  10. Preliminary studies on fluid inclusions in metasomatic albite grains from Lagoa Real, Caetite, Ba, Brazil

    International Nuclear Information System (INIS)

    Preliminary fluid inclusion studies in metasomatic albite grains from the Lagoa Real uranium deposit pointed out to mixing of strong brines (23 wt% NaCl equivalent) with low salinity fluids (2.3 wt% NaCl equivalent). Microthermometry and crushing tests indicated elevated pressures and the presence of hidrocarbons in larger amount than CO2. The remobilization of uranium as uranyl carbonate complexes and its precipitation, reducing U6+ to U4+ by CH4, is considered as a possibility. (Author)

  11. Analysis of the blue phosphorescence of X-irradiated albite using a TL-like presentation

    International Nuclear Information System (INIS)

    By analysing the isothermal decay of phosphorescence at various temperatures, the activation energy and pre-exponential factor of the relevant trap, as well as the kinetic order of the process, can be evaluated. Methods of analysis have been suggested, in which t x I(t) is plotted as function of In(t), where t is the time and I the intensity of the phosphorescence. For a single trap this is a peak-shaped curve, which resembles the corresponding thermoluminescence (TL) curve. Previous methods used some features of this peak, such as the maximum and the half intensity points. In practice, however, it might be difficult to evaluate these points accurately. An improved method is suggested, which seeks the best fit of the whole curve to the theoretical expression. This method is applied to the blue phosphorescence of X-irradiated albite. (author)

  12. Geomorphological stability of Permo-Triassic albitized profiles - case study of the Montseny-Guilleries High (NE Iberia) (United States)

    Parcerisa, D.; Casas, L.; Franke, C.; Gomez-Gras, D.; Lacasa, G.; Nunez, J. A.; Thiry, M.


    Massif paleoalteration profiles (≥ 200 m) occur in the upper parts of the Montseny-Guilleries High (NE Catalan Coastal Ranges). The profiles consist of hard albitized-chloritized-hematized facies in the lower part and softer kaolinized-hematized facies in the upper part of the section. Preliminary paleomagnetic data show Triassic ages for both, the albitized and the kaolinized parts, and point to a surficial formation altered under oxidising conditions. Similar paleoalteration profiles have already been described and dated to Triassic ages elsewhere in Europe [Schmitt, 1992; Ricordel et al., 2007; Parcerisa et al., 2009]. These Permian-Triassic alterations are following a succession of different mineral transformations from the top to the base of the profile: 1) Red facies are defined by an increase in the amount and size of haematite crystals leading to the red colour of the rocks. The increase on haematite content is pervasively affecting the whole rock and is accompanied by the kaolinitization of the feldspars. 2) Pink facies: here, the granite shows an uniform pink colouration, which is mainly due to the albitization of the primary Ca-bearing plagioclases, accompanied by a precipitation of minute haematite, sericite, and calcite crystals inside the albite. Additionally primary biotite is fully chloritized. The pink granites are much more resistant to the present-day weathering than the "unaltered" facies at the base of the profile. 3) Spotted facies is characterized by a partial alteration of the rock, which caused a pink-screened aspect to the rock. The alteration developed along the fractures and is less well developed or absent in the non-fractured zones. In the pink-screened facies, the plagioclases are partially albitized and contain numerous hematite inclusions. Biotites are usually almost entirely chloritized. 4) Unaltered facies: These granites are coloured white to greyish, containing plagioclase and K-feldspar that do not show any trace of

  13. Investigation of dodecylammonium adsorption on mica, albite and quartz surfaces by QM/MM simulation (United States)

    Liu, Zhen; Sun, Ze; Yu, Jian-Guo


    The absorption mechanisms of collector and mineral surface structures play important roles in studies of lepidolite flotation. In this work, quantum mechanics (QM) and hybrid quantum mechanics/molecular mechanics (MM) methods were implemented to investigate the flotation mechanisms of lepidolite from muscovite, quartz and albite. The crystal structures, electron density distributions, bonds and the densities of states of lepidolite were calculated and compared with those of muscovite. The adsorption structures and energies of monomer dodecylammonium (DDA) on the three different minerals were also calculated. The headgroup of the DDA cation was found to adsorb on the surface of minerals, with its hydrophobic tail stretching into the vacuum slab, approximately perpendicular to the surface. Simulation results indicate that the purity of fine lepidolite is limited by the existence of muscovite, due to their similarities in surficial structure and properties. Other gangues were found to be removed efficiently with the use of acidic conditions. The results are in good agreement with other experiments. Compared with simple MM simulations, the use of the QM/MM methods to investigate the adsorption on minerals without specific forcefield parameters was concluded to be a more accurate method to attain monomer surfactant-mineral adsorption energies.

  14. Albitization and the gold-bearing Roodepoort pluton, Pietersburg granite-greenstone terrane, South Africa

    International Nuclear Information System (INIS)

    The gold bearing Roodepoort pluton in the Pietersburg granite-greenstone terrane of South Africa consists primarily of undeformed albite with lesser amounts of quartz, ankerite, magnesite, and pyrite. The pluton intruded a major N-70 degrees trending shear zone, the Knight's Pietersburg line. The present mineralogy of the pluton and its gold content are essentially secondary, formed by open system hydrothermal alteration. However, relic minerals indicate that the pluton originally had a granodioritic composition. This composition, as well as its initial 87Sr/86Sr ratio, are similar to those of the 2 660 Ma Turfloop batholith and are consistent with the possibility that the Roodepoort pluton is an altered phase of the batholith. Sr isotopic data also suggest that hydrothermal alteration occured shortly after the magmatic crystallization of the pluton. Some alteration along the Knight's Pietersburg line occured about 2 680 Ma ago. It is proposed that the emplacement of the Roodepoort pluton, the hydrothermal alteration and the gold mineralization are related to the Limpopo Orogeny. A second phase of open system hydrothermal alteration occured in shear zones along the margins of and within the Roodepoort pluton, apparently about 2 320 Ma ago. 5 figs., 5 tabs., 27 refs

  15. The Black Pearl mine, Arizona - Wolframite veins and stockscheider pegmatite related to an albitic stock (United States)

    Schmitz, Christopher; Burt, Donald M.


    Wolframite-bearing quartz veins flanked by greisen alteration occur at and near the Black Pearl mine, Yavapai County, Arizona. The veins are genetically related to a small albitite stock, and cut a series of Proterozoic metasedimentary and intrusive rocks. The largest vein, the only one mined, is located at the apex of the stock. Field relations imply that this stock is a late-stage differentiate of time 1.4-Ga anorogenic Lawler Peak batholith, which crops out about 3 km to the south. The albitites are of igneous origin and have suffered only minor deuteric alteration. A thin (1 to 2 m) pegmatite unit ('stockscheider') occurs at the contact of the Black Pearl Albitite stock with the country rocks. Directional indicators and other evidence suggest that the pegmatite was formed in the presence of a volatile-rich fluid phase close to the time of magma emplacement. The sudden change from coarse-grained microcline-rich pegmatite to fine-grained, albite-rich albitite suggests pressure quenching, possibly due to escape of fluids up the Black Pearl vein. Stockscheider-like textures typically occur near the apical contacts of productive plutons. The presence or absence of this texture is a useful guide in prospecting for lithophile metal deposits.

  16. The combined effect of temperature and pH on albite dissolution rate under far-from-equilibrium conditions (United States)

    Gruber, Chen; Kutuzov, Ilya; Ganor, Jiwchar


    Two of the most studied aspects of albite dissolution kinetics are the effects of temperature and pH. Previous studies quantified the effect of pH on albite dissolution rate under constant temperature. These studies suggested that the effect of pH on dissolution rate can be attributed to three independent dissolution mechanisms that are dominant in different pH region: acidic - proton-promoted, neutral - water-promoted and alkaline - hydroxide-promoted. Based on experimental results, those studies developed a rate law to predict albite dissolution rate as a function of pH, assuming that the effect of pH is temperature independent. The effect of temperature was attributed either to the temperature dependency of the rate under constant pH or that of the rate law coefficients. Nevertheless no unified rate law that combines both effects was suggested. When applying the effects of temperature and pH assuming they are independent of each other in order to predict the dissolution rate at pH of about 5 and various temperatures, the predicted rate overestimate the rate by 0.5-1 order of magnitude. The current study develops and suggests the use of new rate law that is based on two fast adsorption reactions of protons and hydroxides on two different surface sites. The new rate law considers the effect of surface coverage of protons and hydroxides that is temperature dependent. The new rate law successfully describes the variation of albite dissolution rate (about 8 orders of magnitude) under wide temperature (3.6-300 °C) and pH (1.20-12.40) ranges. Under slightly acidic conditions (pH 5-7) the new rate law predicts a minimum rate zone that was not observed before. In order to confirm whether this minimum rate zone does exist, three SPBE (single-point-batch-experiment) of albite dissolution were conducted at pH 5 and temperatures of 3.6, 25 and 50 °C. The SPBE experiments confirm the existence of minimum rate zone predicted by the independent new rate law. The new rate law

  17. Albite feldspar dissolution kinetics as a function of the Gibbs free energy at high pCO_2

    CERN Document Server

    Hellmann, Roland; Tisserand, Delphine; Renard, François


    We are currently measuring the dissolution kinetics of albite feldspar at 100 deg C in the presence of high levels of dissolved CO_2 (pCO_2 = 9 MPa) as a function of the saturation state of the feldspar (Gibbs free energy of reaction, \\Delta G). The experiments are conducted using a flow through reactor, thereby allowing the dissolution reactions to occur at a fixed pH and at constant, but variable saturation states. Preliminary results indicate that at far-from-equilibrium conditions, the dissolution kinetics of albite are defined by a rate plateau, with R \\approx 5.0 x 10^{-10} mol m^{-2} s^{-1} at -70 -40 kJ mol^{-1}, the rates decrease sharply, revealing a strong inverse relation between the dissolution rate and free energy. Based on the experiments carried out to date, the dissolution rate-free energy data correspond to a highly non-linear and sigmoidal relation, in accord with recent studies.

  18. Upper-greenschist facies intragrain deformation of albite in mylonitic meta-pegmatite and the influence of crystallographic anisotropy on microstructure formation (United States)

    Eberlei, Tobias; Habler, Gerlinde; Grasemann, Bernhard; Abart, Rainer


    We studied the deformation behaviour of albite from Permian meta-pegmatite in Cretaceous upper-greenschist facies shear zones from the Austroalpine Matsch Unit in the Eastern Alps (Italy). Sodium-feldspars from these rocks provide excellent natural examples for studying mechanisms of intragranular deformation under mid-crustal conditions in grains with different angular relations between their (010) planes and the kinematic frame. The studied rocks were deformed at c. 500 °C in localized shear zones with well characterized top-W shear kinematics supposedly during the Cretaceous upper-greenschist facies tectonometamorphic event. Microstructural and chemical data suggest that crystallographic anisotropies in albite exert a strong control on microstructure formation and that albite primarily deformed by a combination of brittle fracturing, dissolution-precipitation and incipient crystal plasticity as a function of the orientation of the crystallographic anisotropy relative to the supposed shortening direction. Dissolution along discontinuities forming stylolites perpendicular to the shortening direction is associated with the precipitation of fine-grained albite with some compositional variability (Ab96-98 and Ab89-91) in cracks. New albite precipitates form aggregates with straight segments of high angle grain boundaries, nearly 120° dihedral angles and only a poor or no orientation relation to the hosting clast. Intragranular kinking is related to continuous lattice rotation of up to 15° by a misorientation axis close to albite [100] and the formation of subgrain boundaries with maximum misorientations of 7°. Synthetic microshear zones supposedly nucleated on pre-existing cracks, and are associated with formation of subgrain boundaries in shortening quadrants and cracks together with precipitates of potassium feldspar in extensional quadrants adjacent to the microshear zone. New microstructural and textural data from mylonitic Permian meta-pegmatites document

  19. Structural relaxation of vitreous albite near Tg and implications for transport properties of the supercooled liquid at high pressure (United States)

    Gaudio, S. J.; Lesher, C. E.


    We estimate the glass transition temperature, Tg, for vitreous/amorphous albite between 0 and 7.7 GPa by tracking the progress of densification following high-temperature annealing experiments with run durations equal to 5τ (when τ=100 s). Tg decreases by 54 K/GPa up to 2.6 GPa, and thereafter shows a weak negative pressure dependence. This behavior mimics the negative pressure dependence of viscosity of albite liquid shown by [1]; however, we do not find a change in the sign of ∂Tg/∂P at least up to 7.7 GPa as reported in some isothermal ∂η/∂P, and ∂DO/∂P data sets. Our high field (21.8 T) 27Al MAS NMR measurements of recovered glasses rapidly quenched from super-Tg conditions possess trace amounts of high coordinated Al at 2.6 GPa and only ˜17% by 5.5 GPa. This suggests that the decrease in Tg (and viscosity at low temperature) results dominantly from topological rearrangement of the supercooled melt structure and not changes to Al or Si coordination number and connectivity of the network. In fact, at Tg from 0 to 8 GPa, the XNBO, or network connectivity, is unchanged [2] and at 7.7 GPa, we find the proportion of high coordinated Al is still ˜35%. Convergence in the timescales of relaxation at Tg(P) and the onset of Na mobility to 6 GPa documented by high-pressure electrical conductivity measurements [3] implies that the fragility of albite melt increases with pressure up to ˜4-5 GPa, without changing the effective polymerization of the melt. In contrast, fragility appears to decrease with pressure in partially depolymerized silicate melts. Such differences in fragility can be used for extrapolation of activation energy based models for viscous flow to high pressure. [1] Kushiro, 1978, EPSL, 41; Brearley et al., 1986, GCA, 50; Brearley and Montana, 1989, GCA, 53; Poe et al., 1997, Science, 276; Suzuki et al., 2002, Phys. Chem. Miner., 29; Funakoshi et al., 2002, J. Phys.: Condens. Matter., 14; Behrens and Schulze, 2003, Am. Min., 88. [2] Lee et

  20. Silicon isotope fractionation in silicate minerals: Insights from first-principles models of phyllosilicates, albite and pyrope (United States)

    Méheut, Merlin; Schauble, Edwin A.


    Isotopic fractionation factors for oxygen and silicon in phyllosilicates (pyrophyllite, talc), albite and pyrope have been calculated using first-principles methods based on density functional theory. Based on exhaustive analysis of numerical convergence, we also update our previous calculations on enstatite and forsterite silicon fractionation properties. Calculated oxygen isotope fractionations agree well with existing estimates for talc and albite. In the case of silicon, qualitative agreement is found with natural data. For phyllosilicates (kaolinite, lizardite, pyrophyllite, talc), Si isotope fractionation properties appear to be correlated with stoichiometry: 1000 ln α30Si={aMg(T)·Mg+aAl(T)·Al}/{Si}, where Sieq. =#Si, Al={3}/{4}#Al and Mg={1}/{2}#Mg (cation equivalents) are the charge-weighed stoichiometric coefficients of each cation, normalized to the charge of the silicon atom, and aX(T) are proportionality coefficients depending on temperature. It is suggested that the effect of cation X on Si isotope fractionation (i.e. aX(T)) will increase with decreasing electronegativity of X. Si isotope fractionation is further correlated with Si-O distances, suggesting a crystal chemical explanation for relation (1) in terms of electron donation effects. This relationship appears valid for quartz, pyrope and enstatite (R2=0.99, n=7), but forsterite is strongly anomalous (error of 0.7‰ at 600 °C). These models indicate that attention should be given to chemical compositions in Si isotope studies. Relation (1) would explain the enrichment in heavy silicon isotopes accompanying magmatic differentiation.

  1. Preliminary notes about the processes of uranium albitization at Lagoa Real (Bahia) and its comparation with the Russian and Sweden processes

    International Nuclear Information System (INIS)

    A brief description and interpretation of the development of the processes of albitization in Russia, Sweden and Brazil, is presented. Based on the comparison of similar characteristics, interpreted and suggested, in the light of present knowledge, it is proposed to set a place in time and space for the uranium mineralization at Lagoa Real. A zoning of the Sn, Cu, Ba, Pb and Zn with respect to the uranium mineralization is suggested. (Author)

  2. New experimental constraints on liquidi, critical mixing, and the second critical end point in the system albite-H2O (United States)

    Makhluf, A. R.; Newton, R. C.; Manning, C. E.


    Supercritical fluids in rock-H2O systems have been proposed to be important agents of mass transfer in high-pressure environments such as subduction zones. We conducted new experimental studies of the important model system H2O-albite (NaAlSi3O8). Equilibrium phase relations were determined in isobaric T-XH2O binaries at 10.0, 12.5, 14.0, 16.0, and 17.0 kbar, at 600-1060 °C and H2O mole fractions (XH2O) of 0.35 to 0.99. All experiments were conducted in a piston-cylinder apparatus. Stabilities of hydrous albite liquid (L) and H2O-rich vapor (V) were determined from textural analysis of run products by binocular, petrographic and scanning electron microscopy. At each pressure, the experiments bracketed the liquidus curve, the topology of the L+V miscibility gap, and the temperature of critical mixing (TC). The bulk composition at critical mixing of L+V is ~50 wt% H2O at all pressures investigated. The P-T trace of the critical curve is described by the equation TC = -59.9P + 1650 (R2=0.998) where T is in °C and P is in kbar, and the equation is valid over the investigated P and T. The results indicate a critical endpoint on the hydrous melting curve at 16.3 kbar and 667 °C. Our results agree reasonably well with the work of Burnham and Jahns (1962, Am. Journal of Sci., 260, 721) and Shen and Keppler (1997, Nature, 385, 710). The constraints on the phase equilibria allow derivation of a thermodynamic model using a modified version of the Redlich-Kister method (1948, Indus. and Eng. Chem., 40b, 345) which allows quantification of the NaAlSi3O8 activity, aAb, and H2O activity, aH2O, over the entire composition range at each of the above listed pressures, between the solidus temperatures and critical temperatures. The results provide fundamental constraints on the physical chemical controls on the generation and solution properties of supercritical and subcritical fluids in the albite-H2O system.

  3. Cretaceous ongonites (topaz-bearing albite-rich microleucogranites) from Ongon Khairkhan, Central Mongolia: Products of extreme magmatic fractionation and pervasive metasomatic fluid: rock interaction (United States)

    Dostal, Jaroslav; Kontak, Daniel J.; Gerel, Ochir; Gregory Shellnutt, J.; Fayek, Mostafa


    Ongonites were defined at their type locality at Ongon Khairkhan, central Mongolia, as pristine magmatic topaz-bearing albite-quartz-keratophyres with up to 4 wt. % F and containing phenocrysts of albite, K-feldspar, quartz and rare mica and topaz hosted in a groundmass composed of the same minerals. However, detailed petrographic and SEM-EDS studies indicate that these rocks underwent considerable subsolidus exchange with deuteric fluids, as evidenced by the presence of albitic plagioclase (Ab~ 100) and end-member orthoclase (Or~ 100), secondary Li-Fe-rich mica (zinnwaldite) enriched in rare metals (Sn, W, Ta, Nb), pitted feldspars containing fluid inclusions, and disseminated fluorite. The ~ 120 Ma old dyke rocks, emplaced at a high structural level in the crust, are strongly peraluminous leucogranites characterized by high Al and alkalis that are also enriched in Rb, Cs, Ga and Ta, depleted in Mg, Ca, Zr, Ba, Sr and Eu, and have anomalous K/Rb, Rb/Sr, Zr/Hf and Nb/Ta ratios compared to the average continental crust. However, the suite has Nd isotopic ratios (ɛNd(120) ~- 1) similar to those of contemporaneous A-type granites of the Mongolian-Transbaikalian igneous province of the Central Asian Orogenic Belt. The inferred primary δ18O (~+ 6 to + 7‰) and Pb isotopic values are consistent with a granitic parent magma and interaction with orthomagmatic fluids. The ongonites and constituent minerals record (1) an extensive and protracted crystal fractionation history, in part due to the presence of volatiles (particularly F) which depressed the solidus temperature of the felsic rocks and extended its duration of crystallization and (2) subsolidus exchange with fluids which includes late flux of heated meteoric water as indicated by modified whole rock δ18O values (+ 0.5 to +2.7‰). The interaction of the ongonites with internally derived orthomagmatic fluids is considered to result in enrichment and/or redistribution of several incompatible elements, but not to

  4. 40Ar-39Ar Dating of Albite and Phlogopite from Porphyry Iron Deposits in the Ningwu Basin in East-Central China and Its Significance

    Institute of Scientific and Technical Information of China (English)

    YU Jinjie; MAO Jingwen


    40Ar-39Ar dating of albite from the Meishan and Taocun iron deposits yields plateau ages of 122.90±0.16 Ma and 124.89±0.30 Ma, and isochron ages of 122.60±0.16 Ma and 124.90±0.29 Ma, respectively. Phlogopite from the Zhongshan-Gushan ore field has a plateau age of 126.7±0.17 Ma and an isochron age of 127.21±1.63 Ma. Analysis of regional geodynamic evolution of the middle-lower Yangtze River region suggests that the porphyry iron deposits were formed as a result of large-scale lithosphere delamination and strong sinistral strike-slip movement of the TanchengLujiang fault zone. The copper, molybdenum and gold deposit system in the middle-lower Yangtze River region was formed during the stress transition period of the eastern China continent.

  5. The albite-water system: Part III. Characterization of leached and hydrogen-enriched layers formed at 300°C using MeV ion beam techniques (United States)

    Hellmann, Roland; Dran, Jean-Claude; Della Mea, Gianantonio


    Samples of albite feldspar were dissolved at 300C and 170 bars for periods up to 24 h in flow-through reactors at acid, neutral, and basic pH conditions. Three MeV ion beam techniques, Resonant Nuclear Reaction Analysis (RNRA), Rutherford Backscattering Spectrometry (RBS), and Elastic Recoil Detection Analysis (ERDA) were employed to obtain elemental depth profiles and information on the composition of the near-surface region after dissolution. Based on the anti-correlative trends of the H and Na profiles obtained by RNRA, Na loss and H permeation are coupled by an ion exchange process in acidic and neutral pH solutions. At basic pH conditions, the evidence is ambiguous as to whether there is a limited degree of ion exchange between aqueous cations and Na, as based on RBS spectra and Na RNRA profiles. The recorded depths of H permeation and Na leaching range from a maximum at acid pH (H permeation exceeding ˜10,000Å, Na leaching ˜20,000Å) to a minimum at basic pH (no H enrichment, Na leaching depths of several hundredÅ). The composition of the leached/H-enriched region is a function of pH. This is postulated to be primarily a function of two factors: the H ion concentration gradient between the solution and the solid, which directly controls the pH-dependence of the ion exchange couple H + (or H 3O +) ← Na + and secondly, the speciation of sbnd Al sbnd -OH and t.sbnd; Si sbnd -OH groups created by hydrolysis reactions and the subsequent preferential release of Al within the leached/H-enriched zone. Based on the ratios of H uptake to Na loss at acid and neutral pH, which range between 0.7 and 2.5, it is not possible to distinguish between H +, H 2O, and H 3O + species permeating into the structure. Free water may be created within the leached/ H-enriched structure via recondensation (repolymerization) reactions of adjacent sbnd Si&-OH groups. Excess H concentration profiles potentially provide indirect evidence for recondensation reactions at depths <700

  6. U-Pb dating of the Madeira Suite and structural control of the albite-enriched granite at Pitinga (Amazonia, Brazil): Evolution of the A-type magmatism and implications for the genesis of the Madeira Sn-Ta-Nb (REE, cryolite) world-class deposit


    Bastos Neto, Artur C.; Ferron, T.M.M.; Chauvet, Alain; Chemale, Farid; De Lima, Evandro F.; Barbanson, Luc; Costa, Clovis F.M.


    The Madeira Sn-Nb-Ta deposit corresponds to the albite-enriched facies of Madeira granite (Madeira Suite) that is part of a NE-SW alignment of three granitic bodies. Structural analyses suggest that the albite-enriched granite emplacement and development of related structures occurred in a different tectonic setting than earlier facies of the granitic bodies in the NE-SW alignment and that the structure was dominated by a N-NE-trending shortening related to a left-lateral motion along a NE-SW...

  7. Determination of chlorite, muscovite, albite and quartz in claystones and clay shales by infrared spectroscopy and partial least-squares regression

    Czech Academy of Sciences Publication Activity Database

    Ritz, M.; Vaculíková, Lenka; Plevová, Eva; Matýsek, D.; Mališ, J.


    Roč. 9, č. 4 (2012), s. 511-520. ISSN 1214-9705 R&D Projects: GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : claystone and clay shale * infrared spectroscopy * chemometrics * chlorite * muscovite Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.530, year: 2011

  8. Hydrothermal Alteration Zoning and Kinetic Process of Mineral-Water Interactions

    Institute of Scientific and Technical Information of China (English)

    张荣华; 胡书敏; 苏艳丰


    This study reports the kinetic experimental results of albite in water and in KCl solution at 22 MPa in the temperature range of 25 to 400(C. Kinetic experiments have been carried out in an open flow-through reaction system (packed bed reactor). Albite dissolution is always incongruent in water at most temperatures, but becomes congruent at 300(C (close to the critical point 374(C). At temperatures from 25 to 300(C, the incongruent dissolution of albite is reflected by the fact that sodium and aluminum are easily dissolved into water; from 300 to 400(C it is reflected by silicon being more easily dissolved in water than Al and Na. Maximum albite dissolution rates in the flow hydrothermal systems have been repeatedly observed at 300(C, independent of flow rates.The kinetic experiments of albite dissolution in a KCl aqueous solution (0.1 mol KCl) indicate that the dissolution rate of albite increases with increasing temperature. Maximum silicon release rates of albite have been observed at 400(C, while maximum aluminum release rates of albite at 374(C. The reaction rates of albite also depend on the potassium concentration in the aqueous solution.These results can be used to interpret the mechanism for forming hydrothermal alteration. The kinetic experiments of mineral-aqueous solutions interactions in the hydrothermal system from 25 to 400(C and at 22 MPa indicate that the formation of the feldspar-mica-kaolinite zoning occurring in some ore deposits may depend not only on the mineral stability but also on the kinetics of feldspar hydration, which is affected by the water property variation when crossing the critical point.

  9. Hydrothermal alteration studies of gabbros from northern central Indian ridge and their geodynamic implications

    Digital Repository Service at National Institute of Oceanography (India)

    Ray; Mevel, C.; Banerjee, R.

    assemblages: chlorite, albite, quartz and locally magnesio hornblende. Crystal plastic deformation resulted in mylonite formation and often porphyroclasts of plagioclase and clinopyroxene grains, while altered gabbro locally exhibits cataclastic texture...

  10. Plagioclase twin laws in lunar highland rocks - Possible petrogenetic significance (United States)

    Dowty, E.; Keil, K.; Prinz, M.


    Plagioclases in different types of lunar highland rocks (all highly feldspathic) are twinned according to different laws and in different styles. Carlsbad and Carlsbad-albite twins, presumed to be growth twins, occur mainly in rocks which show igneous texture, and which have not been severely brecciated. These two twin laws appear to be absent from cataclastic rocks, including cataclastic anorthosite, possibly because the original twins were preferentially broken up in cataclasis (the composition plane being a plane of weakness). Pericline and lamellar albite twins, presumed to be deformation twins (except for some albite growth twins) occur in all types of rocks, and obvious deformation features, such as bending of lamellae, are well shown in many cataclastic rocks. Surprisingly, some Carlsbad and Carlsbad-albite twins are found in rocks with granoblastic texture, which presumably recrystallized in the solid state.

  11. Thermo-optical properties of optically stimulated luminescence in feldspars

    DEFF Research Database (Denmark)

    Poolton, N.R.J.; Bøtter-Jensen, L.; Johnsen, O.


    Optically stimulated luminescence processes in feldspars are subject to competing thermal enhancement and quenching processes: this article describes the thermal enhancement effects for orthoclase, albite and plagioclase feldspars. It is demonstrated that certain lattice vibrational modes can...

  12. A physicochemical study on isotope abundance ratio of lithium contained in a few minerals of pegmatite

    International Nuclear Information System (INIS)

    Lithium samples for mass spectrometric measurement were prepared from biotite, quartz, albite, and microcline which were separated each other from pegmatite in Naegi, Nakatsugawa, Gifu Prefecture, Japan. Lithium isotope abundance ratio (7Li/6Li) of the lithium samples were measured by mass spectrometry using surface ionization ion source. Significant difference has been found among the (7Li/6Li) values of biotite, quartz, albite, and microcline samples. The results have been briefly discussed from physicochemical and geological viewpoint. (author)

  13. Petrological Characterization of the Triassic Paleosurface in the Northern Bohemian Massif (United States)

    Yao, Kouakou; Thiry, Medard; Szuszkiewicz, Adam; Turniak, Krzysztof


    Albitization' is a widespread alteration process affecting sedimentary, igneous and metamorphic rocks. Albitized facies usually show a pinkish to red colour, depending on the degree of alteration. The main mineralogical process of this phenomenon is the pseudomorphic replacement of the primary Ca-Na plagioclases by secondary albite (Na). During this replacement biotite is often transformed to chlorite and inclusions of hematite, apatite, titanite, and calcite develop. So far, albitization has been systematically regarded as caused by magmatic derived hydrothermal brines, alkaline metasomatism reactions (Cathelineau, 1986; Petersson and Eliasson, 1997), or as a low grade metamorphic facies (Boles and Coombs, 1977). Recent studies in the Morvan Massif granites (Ricordel et al., 2007; Parcerisa et al., 2009) showed that the albitization there is related to the Triassic paleosurface. The decrease of this alteration with depth and its paleomagnetic age support the link of the albitization to the Triassic paleosurface. Furthermore, the petrographic data suggest the import of sodium by weathering solutions. The enrichement in Na+ of the fluids that triggered this alteration is probably linked to the Triassic salt deposits. Albitised pinkish facies have been recognized in the northern part of the Bohemian Massif (Polish Sudetes). Typical igneous and metamorphic rocks of the Klodzko area (southern Poland) are granites, granodiorites, schists, amphibolite, and gneisses, mostly of Paleozoic age. Three sites in the Klodzko area were sampled in detail from N to S: (1) Laski quarry, (2) Laski village, and (3) Chwalislaw. Here, the occurrence of the albitization is well developed and specific in its mineralogical paragenesis. Throughout the sample sites different albitization stages can be observed. The most albitized and therefore reddish facies can be found at the Laski village granite that consists of primary quartz and K-feldspar, biotite, and development of secondary

  14. Evolved granitic systems as a source of rare-element deposits: The Ponte Segade case (Galicia, NW Spain) (United States)

    Canosa, Francisco; Martin-Izard, Agustín; Fuertes-Fuente, Mercedes


    In the Ponte Segade area (Galicia, NW Spain) strongly differentiated granites, often associated with rare-element mineralization (Sn-Ta-Nb-Li-Be-Cs) that could be of economic interest, have recently been discovered. These granites appear in the northern sector of the Ollo de Sapo Antiform (Central Iberian Zone, Variscan Orogen). Three different muscovite-rich synkinematic and peraluminous types of leucogranite (leucogranites s.s., albite-rich leucogranites I and albite-rich leucogranites II) and two pegmatite types associated with the albite-rich leucogranites (zoned and banded) have been identified in the studied area. The geochemistry of whole rock leucogranites indicates an enrichment in incompatible elements (lithium, rubidium, beryllium, cesium and hafnium), Al2O3 and Na2O, and an impoverishment in barium, strontium, zirconium, cerium, yttrium and SiO2. Geochemical studies of zircon, muscovite, K-feldspar and tourmaline in the different types of granites and pegmatites indicate the grade of evolution of the granitic system. With differentiation of the system, the zircon is enriched in hafnium and uranium and is impoverished in zirconium. In muscovite and K-feldspar there is an increase in cesium and rubidium. The opposite behavior is observed with regards to the Mg, Fe and Ti contents. In the case of tourmaline, the increase in Li is the best indicator of the grade of evolution. By contrast, Fe and Mg decrease. The sequence of evolution of the granitic system obtained from the geochemical studies indicates that the leucogranites s.s. are the least differentiated, evolving gradually, in accordance with field relationships, to albite-rich leucogranites I. The albite-rich leucogranites II are the most evolved, but no direct relationship between them and leucogranites s.s. has been found. The banded pegmatites associated with the albite-rich leucogranites II are more differentiated than the zoned pegmatites associated with the albite-rich leucogranites I, but are

  15. Integration of geophysical and geological data for delimitation of mineralized zones in Um Naggat area, Central Eastern Desert, Egypt (United States)

    Gaafar, Ibrahim


    An integrated approach for geophysical, geological and mineralogical data was followed for Um Naggat area, Central Eastern Desert, Egypt, in order to delineate its mineralized zones. The albitized granites are well-defined on the Th- and U-channel images, by their anomalous shapes, reaching 150 ppm and 90 ppm respectively, beside low K content. Interpretations of the aeromagnetic maps delineated four regional structural trends oriented due NNW, NW, ENE and E-W directions. They are identified as strike-slip faults, which coincide well with field observations, where NW-trending faults cut and displace right laterally ENE-trending older ones. The interaction between these two strike-slip fault systems confining the albite granite is easily identified on the regional data presenting longer wavelength anomalies, implying deep-seated structures. They could represent potential pathways for migration of enriched mineralized fluids. Geochemically, albite granites of peraluminous characteristics that had suffered extensive post-magmatic metasomatic reworking, resulted into development of (Zr, Hf, Nb, Ta, U, Th, Sn) and albite-enriched and greisenized granite body of about 600 m thick, and more than 3 km in strike length. The albite granite is characterized by sharp increase in average rare metal content: Zr (830 ppm), Hf (51 ppm), Nb (340 ppm), Ta (44 ppm), and U (90 ppm). Thorite, uranothorite, uraninite and zircon are the main uranium-bearing minerals of magmatic origin within the enclosing granite. However, with respect to Zr, Nb, and Ta, the albitized granite can be categorized as rare metal granite. The integration of airborne geophysical (magnetic and γ-ray spectrometric), geological, geochemical and mineralogical data succeeded in assigning the albite granite of Um Naggat pluton as a mineralized zone. This zone is characterized by its high thorium and uranium of hydrothermal origin as indicated by its low Th/U ratio, with rare metals mineralization controlled by two

  16. Sodium storage in deep paleoweathering profiles beneath the Paleozoic-Triassic unconformity (United States)

    Thiry, M.; Parcerisa, D.; Ricordel-Prognon, C.; Schmitt, J.-M.


    A major sodium accumulation has been recognized for long and by numerous authors in the Permo-Triassic salt deposits (Hay et al., 2006). Beside these basinal deposits, important masses of sodium were stored on the continents within deep palaeoweathering profiles in form of albite. Indeed, wide surfaces and huge volumes of granito-gneissic basements of the Hercynian massifs are albitized from North-Africa up to Scandinavia. These albitized rocks have usually been considered as related to tardi-magmatic metasomatic processes (Cathelineau 1986; Petersson and Eliasson 1997). Geometrical arrangement and dating of these alterations point out that these albitizations, or at least a part of them, developed under low temperature subsurface conditions in relation with the Triassic palaeosurface (Ricordel et al., 2007; Parcerisa et al., 2009). Petrology The albitized igneous rocks show a strong alteration with pseudomorphic replacement of the primary plagioclases into albite, replacement of primary biotite by chlorite and minor precipitation of neogenic minerals like albite, chlorite, apatite, haematite, calcite and titanite. Albitized rocks are characterized by their pink coloration due to the presence of minute haematite inclusions in the albite. The development and distribution of the albitization and related alterations above the unaltered basement occurs in three steps that define a vertical profile, up to 100-150 m depth. 1) In the lower part of the profile, albitization occurs within pink-colored patches in the unaltered rock, giving a pink-spotted aspect to the rock. 2) In the middle part of the profile, rocks have an overall pink coloration due to the albitization of the primary Ca-bearing igneous plagioclases. Usually, this facies develops in a pervasive manner, affecting the whole rock, but it may also be restricted to joints, giving a sharp-pink coloration to the fracture wall. 3) Finally, the top of the profile is defined by the same mineral paragenesis as in the

  17. Three-dimensional cooling pattern of a granitic pluton I. The study of exsolution sub-solidus reactions in the Toki granite, Central Japan

    International Nuclear Information System (INIS)

    This paper presents the results of petrographical studies carried out to examine the development and variation of sub-solidus reactions occurring in the Toki granite, Central Japan. The results reveal the three-dimensional cooling pattern of this zoned pluton. Samples collected from 19 boreholes in the Toki granite indicate a spatial variation in the extent of sub-solidus reactions. Exsolution coarsening produced microperthite textures with albite-rich lamellae in this pluton, whereas deuteric coarsening resulted in patchperthite with albite-rich patches. The width and spacing of the albite-rich lamella in microperthite increase systematically and prominently with elevation in the pluton. This indicates that the Toki granite effectively cooled from the roof during the exsolution coarsening stage. Measurements obtained using the hornblende-plagioclase and ternary feldspar thermometers indicate that volume diffusion took place in the temperature range 780-690°C; this diffusion was associated with exsolution coarsening. (author)

  18. Uruguay geology contributions no. 4

    International Nuclear Information System (INIS)

    Sedimentary facies: the metasiltites and mela sandstones develop granoblastic textures. The present lepidoblastic textures in flexured bands of seri cite and/or chlorite, a fine qranoblastic matrix made by quartz-feldespaths. The carbonates develop mosaic textures with big crystals of calcites and dolomite, generally elongated following metamorphic foliation (seri cite/chlorite). The quartzites develop qranoblastic textures, with few minerals. Volcanics facies: the basic volcanics presents doleritic intersect al textural, that exist saussuritized plagioclase and albitic diabasa with diopside-augite beaches. Usually the pyroxenes develop poiquilitic textural. Present amphiboles of the acti note series and frequently sphene. Others basic rocks are microlitio porfiric, in intersect al or fluidal matrix, with albite microliters in epi dote-chlorite-acti note criploerislalline ground.The stability relationships of the diferents types of basic metavulcanites show low metamorphic facies, with temperatures under 530-550 grades C, being the most Irequenl association: albite+actinote+chlorite+epidote+opaques- opaques.The clastic faciest are integrated by monogenic breccia with elements of varied vulcanites and porfiric rnicrolitic texture. The matrix is made of line quartz and epidote aggregate. The basic volcanism present hyalo-porfiric textures with saussuritized plagiodase pheno crystals, and quartz in a micro lo criptocrystalline ground. Were also defined rocks with porfiric texture in a piromeritic ground as well as rocks with vacuolar microlitic texture.The clastic facies are made by breccias with sharp elements, with rare cement, integrated by pyroclastic products, The volcanics rocks present retrometamorphism of the phenocrystals and devitrification. The plagioclase are traslormated in fine aggregates of albite epidote. The regional metamorphism minerals are represented by the para genesis: quartz+albite+chlorite+epidote+(seri cite-actinole), subfacies quartz albite

  19. (Na, Sr)-Feldspars: an experimental study

    International Nuclear Information System (INIS)

    The distribution of Na and Sr between feldspar (albite-Sr-celsian series) and a salt-bearing fluid at 700 deg C and 2 kbar was studied experimentally. The distribution of the elements between feldspar and the fluid is not ideal. Strontium enriches feldspar relative to the fluid over the entire compositional range. The unit cell parameters of the albite-Sr-celsian solid solutions were refined. The experimental data are used to calculate the excess volumes and energies of mixing of the solid solutions of (Na, Sr)-feldspars, which are approximated by a two-parameter Margules model. 28 refs., 6 figs., 6 tabs

  20. Thermo-optical properties of optically stimulated luminescence in feldspars

    DEFF Research Database (Denmark)

    Poolton, N.R.J.; Bøtter-Jensen, L.; Johnsen, O.


    Optically stimulated luminescence processes in feldspars are subject to competing thermal enhancement and quenching processes: this article describes the thermal enhancement effects for orthoclase, albite and plagioclase feldspars. It is demonstrated that certain lattice vibrational modes can be...... selectively probed at specific optical excitation energies. The results are described in terms of the Bohr hydrogen model of the OSL donor defects....

  1. Minerals from Macedonia. XX. Geological Setting, Lithologies, and Identification of the Minerals from Ržanovo Fe-Ni Deposit


    BOEV, BLAZO; Jovanovski, Gligor; MAKRESKI, * & PETRE


    The Ržanovo deposit lies within the western ophiolite belt of the Vardar zone. Its main geological units are discussed in terms of their mineralogy, petrology and petrological evolution. Minerals observed include: magnetite, hematite, clinochlore, talc, sepiolite, magnesioriebeckite, lizardite, dolomite, phlogopite, stilpnomelane, quartz, albite, pyrite, maghemite, pyrrhotine, digenite and millerite. Some minerals had non-distinct morphologies and ambiguous characteristics, preventing iden...

  2. Minerals From Macedonia. XX. Geological Setting, Lithologies, and Identification of the Minerals from Rzanovo Fe-Ni Deposit


    BOEV, BLAZO; Jovanovski, Gligor; MAKRESKI, * & PETRE


    The Rzanovo deposit lies within the western ophiolite belt of the Vardar zone. Its main geological units are discussed in terms of their mineralogy, petrology and petrological evolution. Minerals observed include: magnetite, hematite, clinochlore, talc, sepiolite, magnesioriebeckite, lizardite, dolomite, phlogopite, stilpnomelane, quartz, albite, pyrite, maghemite, pyrrhotine, digenite and millerite. Some minerals had non-distinct morphologies and ambiguous characteristics, preventing identif...

  3. Report on the vitrification and devitrification of Hanford, Washington soil. Final report

    International Nuclear Information System (INIS)

    This study as focused principally on the effects of melting or vitrification and recrystallization or devitrification on soil from the Hanford Reservation in Washington State. The fusion properties of soil are important because the containment of nuclear material in in-situ vitrified soil is a possible requirement. An understanding of the physical and chemical properties of the soil is important in determinaing how the soil can contain the nuclear material. The soil itself is composed of a plagioclastic feldspar, quartz, and hematite. The feldspar is made up of albite and anorthite. When the soil is heated, the first mineral to melt is the albite between 11000C and 12000C. The mineral anorthite melts above 13100C and hematite below 17000C. The quartz does not melt until the temperature exceeds 17150C. The albite in the glass is sodium aluminosilicate. When the albite melts, microscopic spheres of non-crystalline, low-melting sodium silicate form. This indicates that the aluminosilicate matrix decomposes when heated. When crystals, which were previously fused, are heated: crystals begin to reform above 9000C. The minerals which crystallize are feldspar and magnetite, an iron oxide. Recrystallization should begin at a temperature 2500C below the liquidus point. The leaching of sodium, copper, calcium, and aluminum decreased with increasing fusion temperature, while the leaching of iron and barium increased with increasing fusion temperature

  4. Implications from Paleomagnetic Age Constrains and Petrology Analyses on the Reconstruction of the Triassic Paleosurface in Europe - Examples from Catalonia and the Polish Sudetes (Invited) (United States)

    Parcerisa, D.; Franke, C.; Fabrega, C.; Yao, K.; Thiry, M.


    The crystalline basement rocks (such as granites and rhyolithes) of European Variscan massifs often show Permo-Triassic paleomagnetic remagnetizations resulting in underestimated age determinations. These rejuvenated ages are attributed to an alteration of the primary paleomagnetic signal recently carried by the neo-formation of secondary hematite. Hematite forms under oxic conditions. Thus, one may deduce that the remagnetization of the Paleozoic crystalline rocks occurs once the basement rocks are exposed at the Permo-Triassic (paleo)surface. Permo-Triassic remagnetizations are ubiquitous, affecting many emerged Paleozoic rocks in Europe (and beyond) and suggesting a major weathering event under oxic conditions. The extent of the altered zone (> 100 m in depth) points to a sodium enriched groundwater environment. The Na+ enrichment is likely related to the Triassic environment characterized by widespread salt deposits, such as leaching of salt, marine aerosols, periodic/episodic contribution of seawater or evaporative solutions. Under these uncommon shallow conditions the basement rocks containing feldspars (mainly granites and gneisses) suffered an ubiquitous process of alteration consisting in the albitization of feldspars (fsp). The most visible feature of this alteration at outcrop scale is the pervasive red staining of the rock due to the presence of associated Fe-oxide inclusions, which are responsible for the penetrative red colour of the rock. Examination by petrographical microscopy shows that the fsp replacement by albite is pseudomorphic and the shape and optical properties of the parent fsp are preserved in the daughter grain. The composition of the albitized fsp is very constant and close to the albite end-member, displaying values of Ab96-97 in all studied massifs. In cathodoluminescence microscopy, the albitized fsp display a noticeable lack of luminescence, whereas the primary fsp usually show luminescence. The SEM images revealed that secondary

  5. Susceptibility of Granite Rock to scCO2/Water at 200 degrees C and 250 degrees C

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T.; Gill, S., Ecker, L., Butcher, T., Warren, J.


    Granite rock comprising anorthoclase-type albite and quartz as its major phases and biotite mica as the minor one was exposed to supercritical carbon dioxide (scCO{sub 2})/water at 250 C and 13.78 MPa pressure for 104 hours. For comparison purpose, four other rocks, albite, hornblende, diorite, and quartz, also were exposed. During the exposure of granite, ionic carbonic acid, known as the wet carbonation reactant, preferentially reacted with anorthoclase-type albite and biotite, rather than with quartz. The susceptibility of biotite to wet carbonation was higher than that of anorthoclase-type albite. All the carbonation by-products of anorthoclase-type albite were amorphous phases including Na- and K-carbonates, a kaolinite clay-like compound, and silicon dioxide, while wet carbonation converted biotite into potassium aluminum silicate, siderite, and magnesite in crystalline phases and hydrogen fluoride (HF). Three of these reaction by-products, Na- and K-carbonates and HF, were highly soluble in water. Correspondingly, the carbonated top surface layer, about 1.27 mm thick as carbonation depth, developed porous microstructure with numerous large voids, some of which have a size of {>=} 10 {mu}m, reflecting the erosion of granite by the leaching of these water-soluble reaction by-products. Comparing with this carbonation depth, its depth of other minerals was considerable lower, particularly, for hornblende and diorite with 0.07 and 0.02 mm, while no carbonate compound was detected in quartz. The major factor governing these low carbonation depths in these rocks was the formation of water-insensitive scale-like carbonate by-products such as calcite (CaCO{sub 3}), siderite (FeCO{sub 3}), and magnesite (MgCO{sub 3}). Their formation within the superficial layer of these minerals served as protective barrier layer that inhibits and retards further carbonation of fresh underlying minerals, even if the exposure time was extended. Thus, the coverage by this barrier layer

  6. Fluid inclusions in minerals associated to uranium mineralization in Jazida do Engenho (anomaly 09), Lagoa Real uranium province - Bahia, Brazil; Inclusoes fluidas nos minerais associados a mineralizacao uranifera da Jazida do Engenho (Anomalia 09), provincia uranifera de Lagoa Real, BA

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Aurelio da Silva de


    The Engenho deposit (anomaly 09) is south-eastern from Cachoeira Mine (anomaly 13), in the northern part of the Province. The uranium mineralization is associated to 'albitites' (over 70% of albite/oligoclase). Epidosites with uranium may also occur. The 'albitite' main minerals are pyroxene, gamet, albite/oligoclase feldspar, amphibole and biotite. Pyroxene, gamet, plagioclase, titanite and epidote are the minerals associated to the uranium mineralization. The fluids related to pyroxene, gamet and epidote are aqueous-saline, primary and with no carbonic phases and are constant, with small variations. They all present medium to high salinity (14 to 18wt% NaCl eq.), the higher values being related to pyroxene and the lower ones related to gamet and epidote. The fluids associated to albite/oligoclase, although aqua-saline and with no carbonic phases, show salinities much lower than in pyroxene, gamet and epidote, suggesting a intense dilution process indicating dilution toward the later minerals phases. The data suggest the pyroxene formation process occurring under a 3,5 kbar pressure condition which corresponds to approximately 10km depth. The dispersion on Th in albites, due probably to the overheating and non elastic increase in volume, precluded a reliable pressure calculation. The IF's microscopy m plagioclase gneiss (albitites host-rocks) suggests the probability of primary carbonic fluids associated to these minerals. The fluids with CO{sub 2} showed in the gneiss maybe also be present in the albitites, probably as late or intergranular fluids. This assumption is based on the fact that signs of carbonic gases were shown during crushing tests. These tendencies suggest the occurrence of two albitization phases in this Lagoa Real area: one associated to a fluid composed by H{sub 2}O + CO{sub 2} + salts (in the gneiss host) and another (in the albitite) formed by an aqueous-saline phase. The data indicate the Brasiliano event as a thermal

  7. Fluid inclusions in minerals associated to uranium mineralization in Jazida do Engenho (anomaly 09), Lagoa Real uranium province - Bahia, Brazil

    International Nuclear Information System (INIS)

    The Engenho deposit (anomaly 09) is south-eastern from Cachoeira Mine (anomaly 13), in the northern part of the Province. The uranium mineralization is associated to 'albitites' (over 70% of albite/oligoclase). Epidosites with uranium may also occur. The 'albitite' main minerals are pyroxene, gamet, albite/oligoclase feldspar, amphibole and biotite. Pyroxene, gamet, plagioclase, titanite and epidote are the minerals associated to the uranium mineralization. The fluids related to pyroxene, gamet and epidote are aqueous-saline, primary and with no carbonic phases and are constant, with small variations. They all present medium to high salinity (14 to 18wt% NaCl eq.), the higher values being related to pyroxene and the lower ones related to gamet and epidote. The fluids associated to albite/oligoclase, although aqua-saline and with no carbonic phases, show salinities much lower than in pyroxene, gamet and epidote, suggesting a intense dilution process indicating dilution toward the later minerals phases. The data suggest the pyroxene formation process occurring under a 3,5 kbar pressure condition which corresponds to approximately 10km depth. The dispersion on Th in albites, due probably to the overheating and non elastic increase in volume, precluded a reliable pressure calculation. The IF's microscopy m plagioclase gneiss (albitites host-rocks) suggests the probability of primary carbonic fluids associated to these minerals. The fluids with CO2 showed in the gneiss maybe also be present in the albitites, probably as late or intergranular fluids. This assumption is based on the fact that signs of carbonic gases were shown during crushing tests. These tendencies suggest the occurrence of two albitization phases in this Lagoa Real area: one associated to a fluid composed by H2O + CO2 + salts (in the gneiss host) and another (in the albitite) formed by an aqueous-saline phase. The data indicate the Brasiliano event as a thermal event without a predominant fluid

  8. Structural controls and evolution of gold-, silver-, and REE-bearing copper-cobalt ore deposits, Blackbird district, east-central Idaho: Epigenetic origins (United States)

    Lund, K.; Tysdal, R.G.; Evans, K.V.; Kunk, M.J.; Pillers, R.M.


    The Cu-Co ± Au (± Ag ± Ni ± REE) ore deposits of the Blackbird district, east-central Idaho, have previously been classified as Besshi-type VMS, sedex, and IOCG deposits within an intact stratigraphic section. New studies indicate that, across the district, mineralization was introduced into the country rocks as a series of structurally controlled vein and alteration systems. Quartz-rich and biotite-rich veins (and alteration zones) and minor albite and siderite veinlets maintain consistent order and sulfide mineral associations across the district. Both early and late quartz veins contain chalcopyrite and pyrite, whereas intermediate-stage tourmaline-biotite veins host the cobaltite. Barren early and late albite and late carbonate (generally siderite) form veins or are included in the quartz veins. REE minerals, principally monazite, allanite, and xenotime, are associated with both tourmaline-biotite and late quartz veins. The veins are in mineralized intervals along axial planar cleavage, intrafolial foliation, and shears.

  9. Utilization of plastic detectors in autoradiographic studies of radioactive minerals from the Lagoa Real uranium Province, state of Bahia, Brazil

    International Nuclear Information System (INIS)

    A short account on an autoradiographic technique using plastic detectors, it's methodology, application and results is presented. With this technique the distribution of radioactive minerals in rocks can be studied in detail. As radioactive source for this study, samples mineralized in uraninite and/or pitchblende were used. The utilized detectors were the CR-39 (a polymer plate) and films of celulose nitrate: CA-80-15 and CN-85. The mineralization is associated to mafics (amphibole, pyroxene, biotite, garnet, etc.) and to plagioclase (albite or albite-oligoclase), occurring as small inclusions and also in microfractures, cleavages and grain boundaries, mainly among plagioclase crystals which occur close to or practically touching mafic minerals. (Author)

  10. Uranium distribution in dikes of alkaline and ultrabasic rocks

    International Nuclear Information System (INIS)

    Peculiarities of uraium distribution in dikes of alkaline and ultrabasic rocks of the Ukranian crystalline shield have been considered. Its behaviour in the processes of crystallization and postmagmatic change is shown on the basis of studying the substance composition and uranium distribution peculiarities in dikes. To study the uranium distribution in dikes the fragment radiography method was used. Evolution of rock structure and forms of uranium presence in the course of crystallization of subvolcanic dikes of alkaline and ultrabasic compositions has been established. At the early crystallization stage uranium concentrated in main glassy mass. With the crystallization the uranium redistribution and increase of amount of fixed uranium take place. A main part of uranium is fixed in accessories at the end crystallization stage in holocrystalline structures. Subvolcanic dikes bear traces of superimposed albitization. Uranium enrichment of albitized dikes and the character of superimposed uranium distribution testify to an earlier dike formation as compared with the sodium metasomatism process

  11. A-thermal elastic behavior of silicate glasses. (United States)

    Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique


    Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties. PMID:26815634

  12. UV-induced blue thermoluminescence of annealed Na-rich aluminosilicates

    International Nuclear Information System (INIS)

    The luminescence properties of gemstones (silicates, carbonates, phosphates, etc.), are of interest since could be potentially employed as personal dosimeters not only in case of radiation accident or radiological terrorism where conventional monitoring was not established, but also as a UV personal dosimeter. We, herein, report on preliminary results of the UV-induced 480 nm-thermoluminescence (TL) response of a well-characterised natural albite (NaAlSi3O8) from Minas Gerais (Brazil) that, due to its high transparency, is used as gemstone. Different annealing on several aliquots (from 480 to 960 °C) induces several changes in the sensitivity of the sample probably associated with (i) dehydration and dehydroxylation processes and (ii) changes in the lattice structure increasing the Al/Si disorder giving rise to ionic self-diffusion of alkali atoms, thermal stress into atomic positions and variation in the concentration of alkali ions in planar defects. The complex structure of albite has several planar defects (twinning and exsolution interphases which contain hydroxyl groups, water molecules, etc.) that can act as luminescence centres. When the thermal preannealed samples are exposed to 1 h at 254.7 nm under lab conditions one can appreciate changes in the TL behaviour that allows us to think in the albite as a potential UV dosimeter. ©2006 Elsevier Ltd. All rights reserved. -- Highlights: •UV-induced blue TL of annealed albite is studied. •Different annealing on several aliquots (from 480 to 960 °C) induces several changes in the TL sensitivity. •Such changes are linked to dehydration, dehydroxylation processes and changes in the lattice structure. •The Al/Si disorder gives rise to alkali self-diffusion and thermal stresses

  13. Iron-rich fragments in the Yamansu iron deposit, Xinjiang, NW China: Constraints on metallogenesis (United States)

    Li, Hou-Min; Ding, Jian-Hua; Zhang, Zhao-Chong; Li, Li-Xing; Chen, Jing; Yao, Tong


    Volcanic rock-hosted iron deposits are among the important iron ores in China. However, the nature of primary magma and petrogenesis associated with these iron ores remains controversial. Here, we report iron-rich fragments (IRF) from the Yamansu iron deposit in Eastern Tianshan Mountains, NW China, which occurs in association with volcanic breccia, submarine volcanic breccia and ignimbrite. The IRF is composed of five types including oligoclase-iron oxide type (OIO), oligoclase-albite-iron oxide type (OAIO), albite-iron oxide type (AIO), albite-K-feldspar-iron oxide type (AKIO) and K-feldspar-iron oxide type (KIO). These fragments display typical volcanic fabric features, such as porphyritic texture, hyalopilitic texture of the groundmass and vesicles filled by minerals to form amygdales. The feldspar phenocrysts of IRF are dominantly albite. The groundmass of IRF consists of magnetite and feldspar. The magnetite is distributed in between the feldspar laths, and together display hyalopilitic texture which could be observed only in volcanic rocks. The vesicles are filled with magnetite, feldspar, chlorite and calcite from the margin to the interior. The IRF has high Si, Al, Fe, Ca, Ti, Na and K contents and low Mg content. The average total Fe is 26 wt.%. The magnetite is mostly titanium-vanadium magnetite, with the TiO2 content ranging up to 4.86 wt.% and V2O3 content up to 3.20 wt.%. The IRF probably came from iron-rich melts and represent the products of the Fenner magma evolution. The basaltic magma evolved into the Fe-Na-rich residual melts by crystallization under low oxygen fugacity condition in a closed magma chamber after intruding into the shallow crust. The Fe-Na-rich residual melts were emplaced in hypabyssal environments or erupted generating the orebodies or providing the material source for the generation of the high-grade iron ores which were subsequently enriched by the late-stage hydrothermal fluids.

  14. Origen de arcillas alumínicas en horizontes de alteración de materiales graníticos del borde sur de la sierra de Guadarrama


    Martín Patino, M. T.; Guijarro, J.; Casas, J; Martín de Vidales, J. L.


    Three weathering profiles of granitic rocks and two arkoses in the NW of Madrid Province have been studied. Rocks are granodiorites and adamellites with albites showing variable degrees of sericitization, and no-weathered potassic feldspars. Clay fraction in the weathered horizons from these rocks displays high content in beidellite, and minor amounts of illite and 7 Ǻ-halloysite. On the other hand, beidellite, illite and well crystallized kaolinite are clay minerals in the arkosic...

  15. Blueschist metamorphism and its tectonic implication of Late Paleozoic-Early Mesozoic metabasites in the mélange zones, central Inner Mongolia, China (United States)

    Zhang, Jinrui; Wei, Chunjing; Chu, Hang


    Blueschists in central Inner Mongolia are distributed as layers and blocks in mélanges including the southern zone in Ondor Sum area and the northern zone in Manghete and Naomuhunni areas. They have been attributed to the subduction of Early Paleozoic oceanic crust. Blueschists from Ondor Sum and Naomuhunni are characterized by occurrence of sodic amphibole coexisting with epidote, albite, chlorite, calcic amphibole (in Ondor Sum) and muscovite (in Naomuhunni). Blueschists in Manghete contain porphyroblastic albite with inclusions of garnet and epidote in a matrix dominated by calcic-sodic amphibole, epidote, chlorite, albite and muscovite. Phase equilibria modeling for three blueschist samples using pseudosection suggest that the AlM2 contents in sodic amphibole can be used as a good barometer in the limited assemblage involving sodic amphibole + actinolite + epidote + chlorite + albite + quartz under pressures 7-10 kbar. In the sodic amphibole-bearing assemblages, the NaM4 contents in sodic amphibole mainly decrease as temperature rises, being a potential thermometry. The calculated pseudosections constrain the P-T conditions of blueschists to be 3.2-4.2 kbar/355-415 °C in Ondor Sum, 8.2-9.0 kbar/455 °C-495 °C in Manghete and 6.6-8.1 kbar/420-470 °C in Naomuhunni. These P-T estimates indicate a rather high geothermal gradient of 18-25 °C/km for the blueschist metamorphism, being of intermediate P/T facies series. Available zircon U-Pb age data suggests that the protoliths of blueschists were formed later than Late Paleozoic-Early Mesozoic and metamorphosed soon afterwards. An alternative interpretation for the tectonic implication of blueschists in central Inner Mongolia is that they may be a new type attributed to closure of limited ocean basins and do not represent a tectonic regime occurred in conventional subduction setting.

  16. Clay mineralogy of the Boda Claystone Formation (Mecsek Mts., SW Hungary

    Directory of Open Access Journals (Sweden)

    Németh Tibor


    Full Text Available Boda Claystone Formation (BCF is the host rock of the planned site for high level nuclear waste repository inHungary. Samples representing the dominant rock types of BCF were studied: albitic claystone, claystone with high illite content, and analcime bearing claystone. Clay minerals in these three rock types were characterized by Xray powder diffraction (XRD, transmission electron microscopy (TEM and thermal analysis (DTA-TG, and the results were discussed from the point of view of the radionuclide sorption properties being studied in the future. Mineral compositions of bulk BCF samples vary in wide ranges. In the albitic sample, besides the dominant illite, few percent of chlorite represents the layer silicates in the clay fraction. Illite is the dominating phase in the illitic sample, with a few percent of chlorite. HRTEM study revealed that the thickness of illite particles rarely reaches 10 layers, usually are of 5-6 TOT layer thick. Illite crystals are generally thicker in the albitic sample than in the illitic one. The significant difference between the clay mineral characterisitics of the analcimous and the other two samples is that the former contains regularly interstratified chlorite/smectite beside the dominant illite.

  17. Characterization of some clay deposits in South West Nigeria

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE


    Full Text Available Clay minerals are the most important industrial minerals whose application is dependent on its structure and chemical composition. Mineralogical, chemical compositions, phase constitutions, and microstructural morphology of certain clay minerals from three different deposits in south western Nigeria were investigated using state-of-the-art equipment. These were done with the intention of determining the appropriate application for the clay minerals. It was observed that the major phases in the clay samples from the three different deposits are kaolinite, microcline, muscovite/illite, plagioclase/albite and quartz. These phases were observed in varied percentages. It was concluded that sample A (Ifon clay which contains very low kaolinite (5.63%; could not use for making high temperature caliber refractories. But due to its high content of feldspar, it could be processed for the production of feldspar for glass and iron making industries. Sample B is considered to be appropriate for the production the refractory composite due to its most appropriate content of both kaolinite (23.74% kaolinite and feldspars (26.12% microcline and 11.28% plagioclase/albite which is necessary for producing mullite fibers in ceramic matrix at a temperature of around 1400oC. Sample C (Iseyin clay, which contains very low feldspars (3.00% microcline and 3.08% plagioclase/albite and high content of kaolinite was considered suitable for further processing for making high temperature caliber refractories.

  18. Influence of feldspar containing lithium in the sintering of triaxial ceramics; Sinterizacao de uma massa ceramica triaxial com feldspato contendo litio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Camila Felippe de; Strecker, Kurt, E-mail: [Universidade Federal de Sao Joao del-Rei (UFSJ), MG (Brazil)


    In this work, the properties of a ceramic material based on a triaxial mass composed of clay, quartz and 15 to 30% feldspar, albite or spodumene, has been investigated. Specimen were prepared by uniaxial pressing under 28.5MPa and sintering at temperatures of 1000, 1100 and 1200 deg C, for 1h. The samples were characterized by their linear shrinkage, apparent porosity, apparent density and flexural strength, as well as analysis of the microstructure. The best results were obtained for samples prepared with 30% spodumene and sintered at 1200 deg C, with a shrinkage of 6.4%, density of 2.01g/cm{sup 3}, porosity of 14.3% and flexural strength of 13.4MPa, while samples prepared with albite exhibited shrinkage of 5.8%, density of 1.9g/cm{sup 3}, porosity of 18.9% and strength of 9.8MPa. Therefore, by the substitution of albite by spodumene in the ceramic triaxial mass, lower sintering temperatures may be employed, thus reducing production costs by the lesser energy consumption. (author)(.

  19. Influence of feldspar containing lithium in the sintering of triaxial ceramics

    International Nuclear Information System (INIS)

    In this work, the properties of a ceramic material based on a triaxial mass composed of clay, quartz and 15 to 30% feldspar, albite or spodumene, has been investigated. Specimen were prepared by uniaxial pressing under 28.5MPa and sintering at temperatures of 1000, 1100 and 1200 deg C, for 1h. The samples were characterized by their linear shrinkage, apparent porosity, apparent density and flexural strength, as well as analysis of the microstructure. The best results were obtained for samples prepared with 30% spodumene and sintered at 1200 deg C, with a shrinkage of 6.4%, density of 2.01g/cm3, porosity of 14.3% and flexural strength of 13.4MPa, while samples prepared with albite exhibited shrinkage of 5.8%, density of 1.9g/cm3, porosity of 18.9% and strength of 9.8MPa. Therefore, by the substitution of albite by spodumene in the ceramic triaxial mass, lower sintering temperatures may be employed, thus reducing production costs by the lesser energy consumption. (author)(

  20. Emerald mineralization and metasomatism of amphibolite, khaltaro granitic pegmatite - Hydrothermal vein system, Haramosh Mountains, Northern Pakistan (United States)

    Laurs, B.M.; Dilles, J.H.; Snee, L.W.


    Emerald mineralization is found within 0.1- to 1-m-thick hydrothermal veins and granitic pegmatites cutting amphibolite within the Nanga Parbat - Haramosh massif, in northern Pakistan. The amphibolite forms a sill-like body within garnet-mica schist, and both are part of a regional layered gneiss unit of Proterozoic (?) age. The 40Ar/39Ar data for muscovite from a pegmatite yield a plateau age of 9.13 ?? 0.04 Ma. Muscovite from mica schist and hornblende from amphibolite yield disturbed spectra with interpreted ages of 9 to 10 Ma and more than 225 Ma, respectively, which indicate that peak Tertiary metamorphism reached 325 to 550??C prior to 10 Ma. Pegmatites were emplaced after peak metamorphism during this interval and are older than pegmatites farther south in the massif. At Khaltaro, simply zoned albite-rich miarolitic pegmatites and hydrothermal veins containing various proportions of quartz, albite, tourmaline, muscovite, and beryl are associated with a 1- to 3-m-thick heterogeneous leucogranite sill, that is locally albitized. The pegmatites likely crystallized at 650 to 600??C at pressures of less than 2 kbar. Crystals of emerald form within thin (0.20, 0.54-0.89 wt%), to pale blue beryl (emerald results from introduction of HF-rich magmatic-hydrothermal fluids into the amphibolite, which caused hydrogen ion metasomatism and released Cr and Fe into the pegmatite-vein system.

  1. Mineralogy and chemistry of a pegmatic feldspar from hafafit eastern desert, Egypt

    International Nuclear Information System (INIS)

    This pegmatitic feldspar is a perthite composed of microcline and low albite roughly in the ratio of 2:1. The microline is of high triclinicity (0.84). Chemically this alkali feldspar contains 10.58% K2O, 3.37% Na2O and 0.25% CaO. These are equivalent to 62.6% microcline, 28.5% albite and 1.2% anorthite. The plagioclase intergrown with microcline is albite with 4% anorthite. The feldspar in question shows enrichment in Rb and Y with depletion in Sr, Ba and Zr; these characterise strongly fractionated rocks. The enclosing pegmatite is shown to be most probably one of the latest residues of a fractionally crystallising magma directly formed at low temperature range. The present pegmatite is to be contrasted, on mineralogical and geochemical grounds, with the garnetiferous pegmatite of W. Gemal area. Thus two distintive types of pegmatites are recognised, among others, in the south Eastern Desert of Egypt

  2. Effects of fluid-assisted diffusion on texture strength in a mylonitised metagabbro (United States)

    Gardner, Joseph; Wheeler, John; Mariani, Elisabetta


    Most rocks are polyphase materials yet many studies of rock texture tend to isolate the behaviour of individual phases. Characterisation of interaction between phases can yield useful information about the deformation behaviour of real rocks. Our work focuses on a broadly two phase mixture of albite and clinozoisite in mylonitised metagabbros, and how these two phases may have interacted to create, maintain and/or weaken the variable strength CPOs observed in each phase. Intriguingly, the rocks have deformed primarily by diffusion-accommodated processes, which are traditionally thought to weaken or destroy an existing CPO. Our data suggest that diffusion can preserve strong textures. Plagioclase in metamorphosed gabbros from a km-scale extensional shear zone in the NW Italian Alps (Gressoney Shear Zone) has undergone (to a first order) breakdown to albite (Ab) + clinozoiste (Cz) at greenschist facies. Grain size reduction via nucleation of product grains, plus the effects of Zener pinning, lead to an average grain size of parent grains and subsequently modified by fluid assisted diffusion plus grain boundary sliding. Albite precipitates in pressure shadows and fractures show it was the more mobile phase and deformed by pressure solution. Clinozoisite grains are new so their strong CPOs cannot have been inherited; instead they are thought to have behaved as rigid bodies and rotated into parallelism due to their relatively high aspect ratios (generally ~3-4). The Cz grains form strain caps around Cpx porphyroclasts showing they were (largely) insoluble during pressure solution. Albite grain morphology becomes more interstitial closest to porphyroclasts suggesting local high stresses around the clasts drove dissolution. Precipitate that fills pressure shadows may thus be locally derived. Pressure shadows have tails that streak through the matrix as single phase albitic layers; grain size in these layers is commonly >100 μm, which suggests grain growth elsewhere in

  3. Origen de arcillas alumínicas en horizontes de alteración de materiales graníticos del borde sur de la sierra de Guadarrama

    Directory of Open Access Journals (Sweden)

    Martín Patino, M. T.


    Full Text Available Three weathering profiles of granitic rocks and two arkoses in the NW of Madrid Province have been studied. Rocks are granodiorites and adamellites with albites showing variable degrees of sericitization, and no-weathered potassic feldspars. Clay fraction in the weathered horizons from these rocks displays high content in beidellite, and minor amounts of illite and 7 Ǻ-halloysite. On the other hand, beidellite, illite and well crystallized kaolinite are clay minerals in the arkosic rocks. Microfabric characteristics from SEM studies show abundant weathered albites with clean surfaces and formation of beidellite in all areas of the samples. Moreover, spatial relations between albite and beidellite are not observed. In pedochemical weathering of albite, sodium from this mineral should be exchanged with protons from soil solution with very quick kinetics. This initial alkalinization produces an increase in the silica solubility released from albite network. In these environments, a continued contact between weathering solution and albite causes a silica and alumina enrichment and beidellite or 7 Ǻ-halloysite precipitation. Microclimatic variations in weathering environment may cause fluctuations in silica and alumina activities with resultant pH changes. So, when silica activities are high, beidellite neoformation is favoured; on the contrary, 7 Ǻ-halloysite is precipitated.Se han estudiado tres perfiles de alteración de rocas graníticas y dos muestras de arcosas en la zona NO de la provincia de Madrid. Las rocas, clasificadas como granodioritas y adamellitas, presentan albitas con sericitización variable, y escasos feldespatos potásicos muy poco alterados. La fracción arcilla de los horizontes de alteración de estas rocas presenta un alto contenido en beidellita, así como porcentajes menores de ilita y haloisita-7Ǻ. Por otra parte, los minerales de la arcilla presentes en las arcosas son ilita, beidellita y caolinita bien

  4. Geochemical and Mineralogical Characteristics of Pleistocene Lignites and Associated Sediments of Marathousa Coal Field,Central Peloponnese,Greece

    Institute of Scientific and Technical Information of China (English)



    The mineralogy and geochemistry data are presented for thirty-seven shales,four concretions,two carbonate sediments and seven lignites from the Marathousa coal field of the Megalopolis Basin in Greece.The argillaceous rocks consist of chlorite,illite,kaolinte,albite,quartz.opal-A,calcite and dolomite;the concretions of aragonite,gypsum and pyrite;and the carbonate rocks of calcite,quartz and illite.The mineral matter in the lignites consists of gypsum,quartz,albite,chlorite,illite,opal-A,dolomite,pyrite,and rarely calcite and kaolinite Athree-factor model explains the total variaition of major and trace elements in the argillaceous sediments.The first factor is an aluminosilicate factor and involves the following elements:Al,Si,Mg,Na,K,Ti,Mn,Nb,Y,Rb,Zn,Cu,Ni,Cr,Nband V,associated with chlorite,albite and illite.The second factor involves the elements Ca,Sr,Ba,Znand Sc and is related to carbonate lithology and mainly the carbonate concretions with gypsum.The third factor involves Fe and Ce with a weak association with Mn.The diagenesis of the Marathousa sediments and lignites was not very advanced as indicated by (a) the total thickness of the sequence (500m),(b) the presence of biogenic silica(opal-A) and (c) the age of the deposit(Pleistocene).FOr these reasons the rpresence of chlorite,illite and kaolinite in the sediments and lignite is due not to diagenetic reactions but to weathering of the flysch and metamorphic rocks at the edges of the Megalopolis Basin and transport of the weathering products(illite,chlorite,kaolinite)into the basin of deposition.The diagenetic minerals of the Marathousa sequence include pyrite,gypsum,dolomite and aragonite.

  5. Clay mineralogy of the Boda Claystone Formation (Mecsek Mts., SW Hungary) (United States)

    Németh, Tibor; Máthé, Zoltán; Pekker, Péter; Dódony, István; Kovács-Kis, Viktória; Sipos, Péter; Cora, Ildikó; Kovács, Ivett


    Boda Claystone Formation (BCF) is the host rock of the planned site for high level nuclear waste repository inHungary. Samples representing the dominant rock types of BCF were studied: albitic claystone, claystone with high illite content, and analcime bearing claystone. Clay minerals in these three rock types were characterized by Xray powder diffraction (XRD), transmission electron microscopy (TEM) and thermal analysis (DTA-TG), and the results were discussed from the point of view of the radionuclide sorption properties being studied in the future. Mineral compositions of bulk BCF samples vary in wide ranges. In the albitic sample, besides the dominant illite, few percent of chlorite represents the layer silicates in the clay fraction. Illite is the dominating phase in the illitic sample, with a few percent of chlorite. HRTEM study revealed that the thickness of illite particles rarely reaches 10 layers, usually are of 5-6 TOT layer thick. Illite crystals are generally thicker in the albitic sample than in the illitic one. The significant difference between the clay mineral characterisitics of the analcimous and the other two samples is that the former contains regularly interstratified chlorite/smectite beside the dominant illite. Based on the structural and chemical data two illite type minerals are present in the BCF samples: 1M polytype containing octahedral Fe and Mg besides Al, 2M polytype illite generally is free of Fe andMg. Close association of very thin illite plates and nanosized hematite crystals is typical textural feature for BCF. The goal of this study is to provide solid mineralogical basis for further studies focusing on radionuclide sorption properties.

  6. Genesis and solvus relations of submicroscopically intergrown paragonite and phengite in a blueschist from northern California (United States)

    Shau, Yen-Hong; Feather, Melanie E.; Essene, Eric J.; Peacor, Donald R.


    Electron microbeam techniques have been used to examine submicroscopically intergrown paragonite, phengite and chlorite from the South Fork Mountain Schist of the Franciscan Terrane of northern California, which was subjected to blueschist facies metamorphism. The sample also contains quartz, albite, lawsonite, and rutile. The subassemblage albite-lawsonite-rutile requires metamorphic conditions on the low-temperature side of the equilibrium albite+lawsonite+rutile=paragonite+sphene+quartz+H2O (T<200° C and P<7.4 kbars based on thermodynamic data of Holland and Powell 1990). The white micas appear to be optically homogeneous, but back-scattered electron images can distinguish two different micas by their slight difference in contrast. Electron microprobe analyses (EMPA) of micas show Na/(Na+K) ranging from 0.2 to 0.8. The two micas are resolved by transmission electron microscopy (TEM) as packets of phengite and paragonite that range from 20 to several hundred nm in thickness. The compositions, determined by analytical electron microscopy (AEM), constrain the limbs of the phengite-paragonite solvus to values of Na/(Na+K)=<0.02 and 0.97, representing less mutual solid solution than ever reported by EMPA. The textural relations imply that the sheet silicates were derived from reactions between fluids and detrital clays and that they are in an intermediate stage of textural development. We caution that microprobe analyses of apparently homogeneous sheet silicates may yield erroneous data and lead to faulty conclusions using phengite barometry and paragonite-muscovite thermometry, especially in fine-grained rocks that formed at relatively low temperatures.

  7. Elasticity of plagioclase feldspars (United States)

    Brown, J. Michael; Angel, Ross J.; Ross, Nancy L.


    Elastic properties are reported for eight plagioclase feldspars that span compositions from albite (NaSi3AlO8) to anorthite (CaSi2Al2O8). Surface acoustic wave velocities measured using Impulsive Stimulated Light Scattering and compliance sums from high-pressure X-ray compression studies accurately determine all 21 components of the elasticity tensor for these triclinic minerals. The overall pattern of elasticity and the changes in individual elastic components with composition can be rationalized on the basis of the evolution of crystal structures and chemistry across this solid-solution join. All plagioclase feldspars have high elastic anisotropy; a* (the direction perpendicular to the b and c axes) is the softest direction by a factor of 3 in albite. From albite to anorthite the stiffness of this direction undergoes the greatest change, increasing twofold. Small discontinuities in the elastic components, inferred to occur between the three plagioclase phases with distinct symmetry (C1>¯, I1>¯, and P1>¯), appear consistent with the nature of the underlying conformation of the framework-linked tetrahedra and the associated structural changes. Measured body wave velocities of plagioclase-rich rocks, reported over the last five decades, are consistent with calculated Hill-averaged velocities using the current moduli. This confirms long-standing speculation that previously reported elastic moduli for plagioclase feldspars are systematically in error. The current results provide greater assurance that the seismic structure of the middle and lower crusts can be accurately estimated on the basis of specified mineral modes, chemistry, and fabric.

  8. Geologic relationships and mineralization of peralkaline/alkaline granite-syenite of the Zargat Na'am ring complex, Southeastern Desert, Egypt

    Institute of Scientific and Technical Information of China (English)

    Gehad M. Saleh


    The Zargat Na'am ring complex crops out 90 km NW of Shalatin City in the Southeastern Desert of Egypt. The ring complex forms a prominent ridge standing high above the surrounding mafic-ultramafic hills. It is cut by two sets of joints and faults which strike predominantly NNW-SSE and E-W,and is injected by dikes, porphyritic alkaline syenites, and felsite porphyries. It consists of alkali syenites, alkali quartz syenites, and peralkaline arfvedsonite-bearing granitic and pegmatitic dikes and sills.The complex is characterized locally by extreme enrichments in REEs, wolframite and rare, high field strength metals (HFSM), such as Zr and Nb. The highest concentrations ( 1.5 wt% Zr, 0.25 wt% Nb,0.6 wt% ∑REEs) occur in aegirine-albite aplites that formed around arfvedsonite pegmatites. Quartzhosted melt inclusions in arfvedsonite granite and pegmatite provide unequivocal evidence that the peralkaline compositions and rare metal enrichments are primary magmatic features. Glass inclusions in quartz crystals also have high concentrations of incompatible trace elements including Nb (750 × 10-6), Zr (2500 × 10-6) and REEs (1450 × 10-6). The REEs, Nb and Zr compositions of the aegirine-albite aplites plot along the same linear enrichment trends as the melt inclusions, and Y/Ho ratios mostly display unfractionated, near-chondritic values. The chemical and textural features of the aegirine-albite aplites are apparently resultant from rapid crystallization after volatile loss from a residual peralkaline granitic melt similar in composition to the melt inclusions.

  9. Rare earth element and yttrium geochemistry applied to the genetic study of cryolite ore at the Pitinga Mine (Amazon, Brazil)


    Orlando R.R. Minuzzi; Bastos Neto, Artur C.; Milton L.L. Formoso; Sandra Andrade; Valcir A. Janasi; Juan A Flores


    This work aims at the geochemical study of Pitinga cryolite mineralization through REE and Y analyses in disseminated and massive cryolite ore deposits, as well as in fluorite occurrences. REE signatures in fluorite and cryolite are similar to those in the Madeira albite granite. The highest ΣREE values are found in magmatic cryolite (677 to 1345 ppm); ΣREE is lower in massive cryolite. Average values for the different cryolite types are 10.3 ppm, 6.66 ppm and 8.38 ppm (for nucleate...

  10. Thermoluminescence as a palaeothermometer (United States)

    Guimon, R. K.; Weeks, K. S.; Keck, B. D.; Sears, D. W. G.


    The results of annealing experiments on a little-metamorphosed (type 3.5) ordinary chondrite are reported. The thermoluminescence (TL) emission characteristics of the annealed samples show trends very similar to those observed in meteorites which have been naturally metamorphosed in various degrees. The trends are also similar to those observed in annealing experiments on terrestrial albite, where the changes are associated with the low-to-high temperature transformation. These results suggest that the TL phosphor in meteorites is feldspar and that TL can be used to estimate paleotemperatures for little-metamorphosed and highly unequilibrated meteorites.

  11. Diagenesis of Oligocene continental sandstones in salt-walled mini-basins-Sivas Basin, Turkey (United States)

    Pichat, Alexandre; Hoareau, Guilhem; Callot, Jean-Paul; Ringenbach, Jean-Claude


    The recent discovery of Oligo-Miocene salt-walled continental mini-basins in the Sivas Basin (central Anatolia, Turkey) provides the opportunity to unravel the influence of halokinesis on the diagenesis of continental mini-basin infilling. In this study, petrographic and geochemical analyses are used to define the diagenetic sequences recorded by two mini-basins filled mainly by fluvial clastic sediments of the upper Oligocene Karayün Formation. The initial diagenetic features are those commonly encountered in arid to semi-arid continental environments, i.e. clay infiltration, hematite precipitation and vadose calcite cement. Other early cements were strongly controlled by sandstone detrital composition in the presence of saline/alkaline pore water. In feldspathic litharenites and lithic arkoses, near-surface alterations were characterized by the precipitation of analcime (up to 10%), albite and quartz overgrowths (cementation (up to 30%) during shallow burial diagenesis which prevented further mesogenetic alteration phenomena such as compaction. In feldsarenites, early diagenesis differs by (i) the absence of analcime, (ii) better developed albite cements, (iii) thin smectite-illite coatings forming pore linings and (iv) patchy calcite cementation (cement allowed mesogenetic alterations to occur, such as late quartz overgrowths, albitization of feldspar grains and chemical compaction. All these phases are responsible for the low porosity of feldsarenites (cement in feldspathic litharenites and lithic arkoses is related to a greater proportion of detrital limestone in these sandstones. Early precipitation of analcime, albite, smectite-illite and quartz was likely triggered by the alteration of reactive grains by near-surface saline/alkaline brines originating from the dissolution of adjacent diapiric structures. Mini-basin confinement resulting from halokinesis was probably an important factor influencing surface and subsurface saline/alkaline fluid flow and

  12. Thermodynamic conditions of framework grain dissolution of clastic rocks and its application in Kela 2 gas field

    Institute of Scientific and Technical Information of China (English)

    LAI; Xingyun; YU; Bingsong; CHEN; Junyuan; CHEN; Xiaolin


    Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+ and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid, lower Na out of both the mineral and fluid, easier dissolution of the mineral. Similarly, lower-K fluid is more powerful to dissolve K-feldspar than the higher. The anorthite component of plagioclase is most easily dissolved in ground water-rock system, the albite is the secondary, and K-feldspar is the most stable. Selective dissolution of plagioclase occurs in diagenesis because of the plagioclase solid solution that is mainly composed of albite and anorthite end-members, Ca-rich part of which is preferentially dissolved by the pore water, in contrast to the Na-rich parts. Based on investigation of reservoir quality, secondary pore, dissolution structures of feldspar, clay minerals and ground water chemistry of the Kela 2 gas field of Kuqa Depression in the Tarim basin of Western China, we discovered that the secondary pore is very well developed in the highest quality section of the reservoir, and the plagioclase of which was obviously selectively dissolved, in

  13. Favourable environments for uranium occurences in Brazil

    International Nuclear Information System (INIS)

    Based on the present knowledge of Brazilian Precambrian geology, an attempt is made to divide Precambrian rocks into different regions according to their favourability criteria for uranium concentrations. Paleozoic and Mesozoic occurrences are also mentioned. They are mainly associated with large sedimentary basins. Brazilian uranium occurrences can be grouped into the following environments: (1) Metaconglomerates; (2) Metasomatic rocks (associated with albitization); (3) Vein type; (4) Sandstone type and (5) Intrusive alkalic rock. Upper Proterozoicas folding regions related to mobile belts and large Precambrian unconformities are good targets for uranium exploration in Brazil. (Author)

  14. Low pressure experiments in piston cylinder apparatus: calibration of newly designed 25 mm furnace assemblies to P = 150 MPa


    Masotta, M.; Sapienza Università Roma; Freda, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Paul, T. A.; Depths of the Earth co; Moore, G.; Arizona State University; Gaeta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; TROLL, V.R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia


    We present new pressure calibration experiments demons trating that the piston cylinder apparatus is suit-able for experiments at pressure as low as 150 MPa. Two newly designed 25 mm furnace assembly have been developed and calibrated using two differe nt calibration methods: the NaC l melting curve and the sol-ubility of H2 O in albitic and rhyolitic melts. The NaCl calibration experiments performed in the pressure range 150 –500 MPa yield the pressure correction that has to be applied...

  15. Uraniferous mineralizations in the Kuusamo Schist Belt, northeastern Finland

    International Nuclear Information System (INIS)

    The Kouveraara Co-Cu-Au mineralization was found in 1982 with the aid of a geophysical ground survey. This survey was connected with research on the Kouvervaara uranium mineralization in the Early Proterozoic Kuusamo Schist Belt, located just south of the Arctic Circle. In further work, using the Kouvervaara sulphide mineralization as a reference, six Co and Au bearing sulphide mineralizations were discovered, with the help of low altitude aerial geophysical techniques. The Co-Au mineralizations, hosted by the Sericite Quartzite Formation, occur within the hydrothermally altered zones. These zones consist of chloritization, carbonatization, sulphidization, sericitization and albitization, the latter being the most extensive. Excluding the Juomasuo mineralization, uranium is only a trace element in these mineralizations. Other characteristic trace elements are molybdenum and tungsten. The Sivakkaharju and Konttiaho Co-Au-U-Mo mineralizations were found by radiometric ground surveys carried out in 1985 and 1986. These hydrothermal mineralizations occur within brecciated quartz-albite-carbonate rocks and are good manifestations of the positive correlation between uranium and gold in the Kuusamo area. Compared with the other sulphide mineralizations, the Au, U, and Mo contents are remarkably high. Genetically, the mineralizations in the Kuusamo area are associated with deep seated fracture and fault zones, controlled by ancient intracontinental hot spot activity and continental rifting. (author). 31 refs, 6 figs, 2 tabs

  16. Mineralogical study on volcanic ash of the eruption on September 27, 2014 at Ontake volcano, central Japan: correlation with porphyry copper systems (United States)

    Minami, Yusuke; Imura, Takumi; Hayashi, Shintaro; Ohba, Tsukasa


    The volcanic ash of the eruption on September 27, 2014 at Ontake volcano consists mostly of altered rock fragments. The ash contains partly altered volcanic rock fragments consisting of primary igneous minerals (plagioclase, orthopyroxene, titanomagnetite, and feldspars) and volcanic glass accompanied by alteration minerals to some extents, and contains no juvenile fragments. These features indicate that the eruption was a non-juvenile hydrothermal eruption that was derived from the hydrothermal system developed under the crater. The major minerals derived from hydrothermal alteration zones are silica mineral, kaolin-group mineral, smectite, pyrophyllite, muscovite, alunite, anhydrite, gypsum, pyrite, K-feldspar, albite, and rutile. Minor chlorite, biotite, and garnet are accompanied. Five types of alteration mineral associations are identified from observations on individual ash particles: silica-pyrite, silica-pyrite ± alunite ± kaolin, silica-pyrophyllite-pyrite, silica-muscovite ± chlorite, and silica-K-feldspar ± albite ± garnet ± biotite. The associations indicate development of advanced argillic, sericite, and potassic alteration zones under the crater. Occurrence of anhydrite veinlet and the set of alteration zones indicate hydrothermal alteration zones similar to late-stage porphyry copper systems. Comparing the mineral associations with the geologic model of the late-stage porphyry copper systems, the source depths of mineral associations are estimated to range from near surface to >2 km. The depths of advanced argillic alteration, sericite, and potassic zones are 0 to ~2, ~1.5 to ~2, and >2 km, respectively.

  17. The mineral composition and the ore types of the uranium-vanadium deposit Srednaya Padma (Onega region, Russian Federation)

    International Nuclear Information System (INIS)

    The deposit Srednaya Padma is the largest and best prospected of the uranium-vanadium deposits of the Onega region. There are abnormally high concentrations of gold, palladium, platinum, copper and molybdenum in the ores. The ore mineralization is located in the albite-mica-carbonate metasomatites upon the proterozoic aleorolites and schists. The ores are generally composed of albite, dolomite and micas. The main vanadium mineral is vanadian flogopite, the main uranium mineral is pitchblende. The proportions of the ore and ore-forming minerals are determined. The noble metal mineralization (which associates with selenides of lead, silver and bismuth) and the copper-molybdenum mineralization (represented by chalcopyrite and molybdenite) are spread extremely irregularly in the orebodies. The ores can be classified as carbonaceous by their compositions. Four mineral ore types, with regard to the mineralization composition of the ore, are determined: pitchblende-flogopite, noble metal-pitchblende-flogopite, sulphide-flogopite and hypergene. The ores are classified in three technological ore types (uranium-vanadium; uranium-vanadium with Au, Pd, Pt; vanadium with Cu, Mo) and two technological ore sorts (by the acid inventory in processing). The correlation between the composition of the ore and the technological processing parameters are determined. The specifics of the various ore types distribution in the orebodies are discovered. A comparison with the other U-V deposits of the Onega region is made. (author). 4 refs, 3 figs, 2 tabs

  18. Three-dimensional thermoluminescence spectra of feldspars

    International Nuclear Information System (INIS)

    The paper describes a systematic study of the thermoluminescence emission spectra of thirty feldspars covering the whole composition range from high potassium (orthoclase) through high sodium (albite) to high calcium (anorthite). The study was simulated by the need to understand the properties of feldspars in connection with the application of thermoluminescence to the dating of sediments. The data were obtained with a high-sensitivity Fourier transform spectrometer, which allows measurements at the low light levels found in natural samples. Three-dimensional displays in which intensity is plotted as a function of photon energy and temperature assist identification of a wide range of spectral features. A number of common features are found: an emission at 3.1 eV is strong in alkali feldspars with more than 80 mole % orthoclase and occurs with lower intensity in most other alkali feldspars and some plagioclases; a broad band with a flat maximum near 2.6 eV is found in all alkali feldspars at temperatures near 200oC when artificially irradiated, and at higher temperatures in some natural samples. Emission at 2.2 and 4.4 eV is characteristic of plagioclases with more than 75 mole % of albite. Plagioclases with more than 50 mole % anorthite, and alkali feldspars with less than 50 mole % orthoclase, emit mainly in the range 1.5-2 eV. These features can be identified with luminescence centres suggested by previous workers. The application to practical thermoluminescence dating is discussed. (Author)

  19. Formation of sulfide deposits and its relation to sodic and potassic alteration of Proterozoic metabasites in the Sax» rift basin, Bergslagen, Sweden (United States)

    Hellingwerf, R. H.


    A number of Cu-Zn-Fe-Pb-As sulfide mineralizations spatially associated with metabasic sills, dikes, and flows of originally continental tholeiitic composition occur in the 1.9 1.8-Ga-old metavolcano-sedimentary sequence in the Sax» sedimentary rift basin. In higher stratigraphic levels weak sulfide mineralizations occur just below Narich, albite-chlorite-calcite-quartz-actinolite-bearing metabasic flows; in the lower stratigraphic levels sulfide mineralizations occur (a) spatially associated with potassiumrich, microcline-scapolite- or biotite/phlogopite-rich metabasic sills and dikes, and (b) below metabasic flows in which albite and calcite are replaced by microcline and scapolite. The sodium- and potassium-rich metabasites are demonstrated to represent products of spilitization and potassic alteration, respectively. During spilitization Fe, Cu, Co, and HREE are leached from the basic flows, whereas during potassic alteration Fe, Cu, Y, and possibly Zn and Zr are leached from the basic rocks, indicating a genetic relationship between the metabasites and the Cu-Fe-sulfide mineralizations. Spilitization probably took place due to interaction of the flows with descending, sea-water-dominated fluids in a subseafloor hydrothermal system with temperatures roughly between 250° and 400°C. Potassic alteration probably took place by ascending fluids at higher temperatures than for spilitization.

  20. Mineralogy and phase transition of oil sands coke ash

    Energy Technology Data Exchange (ETDEWEB)

    Heemun Jang; Thomas H. Etsell [University of Alberta, Edmonton, AB (Canada). Department of Chemical and Materials Engineering


    Coke obtained from Syncrude and Suncor was investigated to characterize the metals and minerals by ashing it at various temperatures. Samples were collected by high temperature ashing at 100{sup o}C intervals from 400 to 1200{sup o}C. Samples were also obtained from low temperature ashing (LTA) which gives little effect on the mineral assemblage compared to HTA samples. X-ray diffraction patterns of Suncor and Syncrude coke ash were analyzed qualitatively and quantitatively to characterize the mineral phases in the sample and their thermal transition behavior. In Suncor ash, kaolinite, illite, gypsum, anhydrite, microcline, anorthite, hematite, sillimanite and quartz were dominant phases in ash from the LTA temperature up to 700{sup o}C, and mullite, cristobalite, hercynite, albite, anorthite, pseudobrookite and other iron-titanium oxides were dominant mineral phases from 700 to 1200{sup o}C. In Syncrude ash, illite, anhydrite, quartz, anorthite, microcline, sillimanite and hematite were dominant up to 700{sup o}C, and hercynite, anorthite, albite, pseudobrookite and other iron-titanium oxides were dominant up to 1200{sup o}C. The higher quantities of Ca, K and Na, and the lower quantities of V, Fe and Ni in Syncrude ash resulted in higher amorphocity and the different mineral phases. 32 refs., 3 figs., 5 tabs.

  1. Fenitization of metabasic rocks by ferrocarbonatites at Haast River, New Zealand (United States)

    Cooper, Alan F.; Palin, J. Michael; Collins, Alice K.


    Dolomite-ankerite-siderite ferrocarbonatite dykes of the Alpine Dyke swarm, Westland, New Zealand, intrude greenschist facies metabasites and produce carbonate-albite-muscovite-hematite-Nb-rutile and cancrinite-aegirine-carbonate fenites. The protolith foliation and metamorphic segregations are retained during fenitization despite complete mineralogical reconstitution. Quartz veins in metabasite are reconstituted to albite-aegirine-arfvedsonite/riebeckite assemblages. Geochemically the metabasites have been enriched in Na, C, Sr, Ba, Nb, Th and middle REE, and depleted in Fe, Ca, Mg, V, Cr, Ni, Zr and Hf, light- and heavy-REE. Si and Al show variable behaviour, with Si being consistently depleted in the generation of cancrinite fenite. The process approximates to an equal volume replacement. Field relationships of these dykes suggest that the carbonatites are the sole source of alkaline fenitizing fluids and that ferrocarbonatite magma was, therefore, considerably more sodic than the observed crystalline composition. Sr isotope ratios of fenite and carbonatite minerals indicate they have been partially modified by interaction with carbonatite-derived and schist-derived fluids respectively, and that fenitization, therefore, represents a two-way fluid infiltration. Carbonate minerals in fenite and carbonatite have been subsequently partially recrystallized during oxidation, highlighting the complex emplacement history involving carbonatite crystallization, fenitization and late-stage hydrothermal/carbothermal processes.

  2. Southern complex: geology, geochemistry, mineralogy, and mineral chemistry of selected uranium- and thorium-rich granites

    International Nuclear Information System (INIS)

    Four major rock groups are defined in the Southern Complex: the Bell Creek Granite (BCG), the Clotted Granitoids (CGR), the Albite Granite (AGR), and the Migmatite Complex. Metatexites of the Migmatite Complex are the oldest rocks and include paleosome of a metasedimentary and metavolcanic protolith represented by Banded Iron Formation, Banded Amphibolite, and Banded Gneisses, and interlayered or crosscutting leucogranites. The CGR span the range from metatexite to diatexite and represent in-situ partial melting of metapelitic layers in the protolith during intrusion of the BCG. The BCG cuts the migmatites, is locally cut by the CGR, and was derived by partial melting of a dominantly metasedimentary protolith at some depth below the presently exposed migmatites during a regional tectonothermal event. The Albite Granite is a 2km diameter, muscovite-fluorite-columbite-bearing intrusive stock that cuts all other major units. The thorium history of the BCG is a function of the history of monazite. The thorium history of the CGR is also dominated by monazite but the thorium content of this unit cannot be entirely accounted for by original restite monazite. The uranium history of the BCG and CGR was dominated by magmatic differentiation and post magmatic, metamorphic and supergene redistributions and is largely independent of the thorium history. The thorium and uranium history of the AGR was dominated by magmatic/deuteric processes unlike the BCG and CGR

  3. In situ radiation measurement and estimation of U/Th ratio to reflect on the uranium bearing potential zone in metamorphic rocks of Mahendragarh District, Haryana

    International Nuclear Information System (INIS)

    Gross gamma radiation survey was carried out using NaI(Tl) scintillator based portable gamma ray spectrometer (PGRS) around areas of Gaonri, Dholera, Pachnota and Meghot in Mahendragarh district, Haryana. Geologically the area forms part of north Delhi fold belt comprising calc-silicate, quartz biotite schist, impure marble, quartzite and pegmatite rocks. Equivalent uranium (eU3O8) concentration in ppm was estimated in situ on a regular grid pattern of 500 m (E-W) x 1000 m (N-S) and grab samples were collected at grid locations for analyzing in the laboratory for estimating the contents of eU3O8 Raeq, ThO2 and %K. A comparison with the laboratory analysed grab samples for eU3O8 data and in situ radiation measurements shows a good match of the two sets of data. The in situ measurements indicate higher concentration of eU3O8 in Chapra Bibipur in northeastern most corners, Maghot area in central part, Gaonri in western part and Pachnota in southwestern part of the study area. As index to uranium favorability, U(Raeq)/Th contour map (prepared using Surfer software with Krieging interpolation method for this grid size) based on the data on grab samples was generated which show three major clusters of relatively high U/Th ratio. The blocks delineated are enriched in sodic minerals albite which support albite hosted uranium mineralization potential in metamorphic rocks in Haryana. (author)

  4. Metamorphism, metasomatism and mineralization at Lagoa Real, Bahia, Brazil

    International Nuclear Information System (INIS)

    Uranium deposits cumulatively in the 100,000 tonne U3 O8 range occur within ductile shear zones transecting Archean basement gneisses of the Sao Francisco Craton, at the Lagoa Real region of south-central Bahia, Brasil. The gneisses, dated at 2.6-3.0Ga, are at amphibolite and granulite facies and overlie to the west, the Proterozoic Espinhaco metasedimentary sequence along a thrust fault. Petrography and mineral chemistry show that in the zones of alteration/mineralization, the original K-feldspar + quartz + albite/oligoclase + hastingsite assemblage, is replaced by albite + aegirine - angite + andradite + hematite assemblages, with or without uraninite. This information along with oxygen isotope, whole rock geochemistry and fluid inclusion studies indicate that the alteration process involves removal of Si, K, Rb, Ba and addition of Na under oxidizing conditions. V, Pb and Sr were introduced along with U via interaction with saline SO2 - rich, isotopically light fluids under varying water/rock ratios and at temperatures of 500 - 5500C. 87Sr/86Sr systematics suggest that it is unlikely that Sr, and by extension uranium, were introduced by fluids originating from the basement gneisses. Geological constraints and the general alteration pattern are consistent with the release of the mineralizing fluids in response to the overloading of the basement rocks onto the Sedimentary Espinhaco via a thrust mechanism. (Author)

  5. Three-dimensional cooling pattern of a granitic pluton 2. The study of deuteric sub-solidus reactions in the Toki granite, Central Japan

    International Nuclear Information System (INIS)

    Petrographical studies examining the development and variations of sub-solidus reactions recorded in the Toki granite represent the three-dimensional cooling pattern of this zoned pluton in Central Japan. Samples collected from 19 boreholes in the Toki granite show characteristics indicative of spatial variations in the extent of the sub-solidus reactions. Exsolution coarsening has produced microperthite, including albite-rich lamellae, in this pluton, while deuteric coarsening has resulted in the formation of patchperthite, myrmekite, and the reaction rim. The extent of the deuteric coarsening reactions can be evaluated from the width and spacing of the albite-rich patch in patchperthite and from the thickness of myrmekite and the reaction rim. The width, spacing, and thickness of these textural features increase systematically with elevation; they also increase gradually in the horizontal inward direction in the western part of the pluton but not in the eastern part of the pluton. The systematic variations in textural development indicate that the Toki granite cooled effectively from the roof and from the western margin during the deuteric coarsening stage. The deuteric coarsening may have occurred at temperatures below 500°C, as indicated by ternary feldspar thermometry. (author)


    Directory of Open Access Journals (Sweden)

    Akintola O. F


    Full Text Available Pegmatites in Nasarawa area of Central Nigeria lie within a fracture-controlled east-north-east trending rare metal pegmatite belt closely associatedwith late PanAfrican peraluminous granites inNigeria. Trace elements of feldspars andmuscovites of pegmatites inNasarawa area of CentralNigeriawere analyzed to determine the raremetalsmineralization potentials of the pegmatites. The minerals show fractionation even within units of complex mineralizedpegmatites as indicated by the wide ranges of K/Rb in Na-feldspars (albites, muscovites and K-feldspars and the wide range of K/Tl in the latter two minerals. Cs, Rb and Tl and the rare earth elements (REEs Ce, La, Pr and Y are enriched in the K-bearing muscovites and K-feldspars; K-feldspars have the highest average values of Tl, Ce, La, Pr and Y while the muscovites have the highest average values of Sn, Nb, Ga, F and Zn. Average values of Ta, Sr, Ba,Wand Zr are highest in the albites,which also have the lowest averageNb/Ta ratio. This is an indication that these elementsare enriched along lateNa-rich raremetalmineralizing fluids. The rare alkalisRb and Cs and Tl are positively correlated with the rare lithophile elements (Ta, REEs, Pb, Bi and Y, in both the pegmatite K-feldspars and muscovites, strongly positively correlated with Sn in the muscovites but negatively correlated with Nb in the minerals. Inthe pegmatitic albites, Nb has very strong positive correlations with Ta (0.868 and Zr (0.847, which is indicative of the incorporations/substitution of these elements in the crystal lattice of the ore minerals. There is a general enrichment of the rare elements towards themiddle and inner zones of the complexmineralized pegmatites. Fluorine, phosphorus and boron-rich fluids played significant roles in the magmatic complexation/fractionation and concentration of Sn-Ta-Li-Cs-Be in the albitized zones of the highly evolved pagmatites.K/Rb versusCs in theK-feldspars classify the pegmatites into

  7. The hydrothermal alteration and contact metamorphism on the tonalite and volcanics of the Komahashi-Daini Seamount, northern Kyushu-Palau Ridge (United States)

    Haraguchi, S.; Ishii, T.; Li, Y.; Kato, Y.


    At the Komahashi-Daini Seamount (KDS) in the northern Kyushu-Palau Ridge (KPR), acidic plutonic rocks (tonalite) were recovered by research cruises of Japanese Geodynamics Project (GDP) during 1970's and R/V Tansei-Maru, Ocean Research institute, during 1990's. Haraguchi et al. (2003) considered that this tonalite was produced by fractional crystallization of the basaltic magma during the arc volcanism before spreading of the Shikoku backarc basin. This study was selected flesh samples. However, many altered plutonic rocks and volcanics were recovered by these cruises. These volcanics show highly alteration. In this study, we research these highly altered plutonics and volcanics by petrographical, geochemical and mineralogical processes using chemical analysis by electron microprobe analyses (EPMA) and identification by X-ray diffraction (XRD). And we consider alteration processes during intrusion of acidic plutonic body. Alteration of tonalites is prominent in colored minerals. Many colored minerals are replaced into chlorite identified by EPMA and XRD analyses. Fresh tonalites not altered of colored mineral are about 1/10 amount of all recovered plutonic rocks. Plagioclase resist from alteration compared to colored mineral, however, albitization is observed in some high-altered tonalites. K-feldspar is rare in altered tonalites. Many volcanics show completely replacement into secondary phases and some rocks display relic igneous textures. Plagioclase phenocrysts exhibit albitization, and albite and chlorite are identified by XRF and EPMA, similar to plutonic rocks. Quartz is also identified. Altered colored minerals are identified into epidote by XRD and EPMA analyses. Fine secondary phases are difficult to identify by microscope observation, and minor secondary phase are difficult to identify by XRD. We considered that the analyses of mineral composition by EPMA are the effective tools of identification of fine mineral phases. The mineral assemblage of chlorite

  8. Phase Equilibria and Thermobarometry of Lawsonite and Pumpellyite-Bearing Metabasalts From Crete (United States)

    Manon, M. R.; Essene, E. J.


    High-pressure, blueschist facies rocks associated with the subduction and subsequent exhumation of sedimentary rocks along the Hellenic subduction zone now outcrop over a large portion of the Greek island of Crete. They host the rare pelitic index mineral, carpholite, and has one of the few occurrences of metamorphic aragonite in marbles. Though largely composed of pelites, many small pods of metabasalts contain index minerals such as lawsonite and glaucophane. The assemblage lawsonite + pumpellyite has been found, providing an excellent opportunity to unravel the pressures and temperatures to which these rocks were subjected during subduction. Blueschists from the central part of Crete are typically glaucophane-bearing, with plentiful epidote, sphene and chlorite. Millimeter scale domains within some of the rocks contain the assemblage, quartz + lawsonite + albite + chlorite + epidote ± pumpellyite ± glaucophane. The presence of lawsonite and epidote roughly locates the rocks between the lawsonite and epidote blueschist facies as defined by Evans (1990). Chemically the lawsonite is fairly pure, with only small amounts of Fe (less than 0.4 wt %). Although some pumpellyite has almost no iron, when in equilibrium with the lawsonite it typically contains subequal amounts of Fe and Mg, (Fe/(Fe+Mg) is on average ~0.45). Chlorite is also roughly halfway between clinochlore and chamosite. The glaucophane is crossitic in composition. Clinozoisite has around 4 weight percent Fe2O3 (0.25 atoms Fe per formula unit). The albite and quartz are pure. The reaction albite + pumpellyite + lawsonite = glaucophane + clinozoisite + quartz + fluid has a somewhat steep slope (74 bar/°C) and can be used to constrain temperatures. Another reaction between lawsonite and pumpellyite is glaucophane + lawsonite = pumpellyite + chlorite + albite + quartz + fluid. The slope of this reaction is (24 bar/°C) and so the intersection of the two provides a reasonable estimate of the P

  9. Paragenesis of sodic pyroxene-bearing quartz schists: implications for the P-T history of the Sanbagawa belt (United States)

    Enami, Masaki; Wallis, Simon R.; Banno, Yasuyuki


    Sodic pyroxene (jadeite content X jd=0.1 0.3) occurs locally as small inclusions within, albite porphyroblasts and in the matrix of hematite-bearing quartz schists in the Sanbagawa (Sambagawa) metamorphic belt, central Shikoku, Japan. The sodic, pyroxene-bearing samples are characteristically free from chlorite and their typical mineral assemblage is sodic pyroxene+subcalcic (or sodic) amphibole+phengitic mica+albite+quartz+hematite+titanite±epidote. Spessartine-rich garnet occurs in Mn-rich samples. Sodic pyroxene in epidote-bearing samples tends to be poorer in acmite content (average X Acm=0.26 0.50) than that in the epidote-free samples ( X Acm=0.45 0.47). X Jd shows no systematic relationship to metamorphic grade, and is different among the three sampling regions [Saruta-gawa, Asemi-gawa and Bessi (Besshi)]. The average X Jd of the Saruta-gawa samples (0.21 0.29) is higher than that of the Asemi-gawa (0.13 0.17) and Bessi (0.14 0.23). The P-T conditions of the Asemi-gawa and Bessi regions are estimated at 5.5 6.5 kbar, >360°C in the chlorite zone, 7 8.5 kbar, 440±15°C in the garnet zone and 8 9.5 kbar, 520±25°C in the albite-biotite zone. Metamorphic pressure of the Saruta-gawa region is systematically 1 1.5 kbar higher than that of the Asemi-gawa and Bessi regions, and materials of the Saruta-gawa region have been subducted to a level 3 5 km deeper than materials that underwent metamorphism at equivalent temperatures and are now exposed in the Asemi-gawa and Bessi regions. Pressure slightly increases toward the north (structurally high levels) through the Sanbagawa belt of central shikoku. Two types of zonal structure were observed in relatively coarse-grained sodic pyroxenes in the matrix. One type is characterized by increasing X Jd from core to rim, the other type by decreasing X Jd from core to rim. Both types of zoned pyroxenes show an increase in X Fe 2+[=Fe2+/(Fe2++Mg)] from core to rim. The first type of zoning was observed in a sample from the

  10. Propiedades termoluminiscentes de una albita de minas Geraes (Brasil

    Directory of Open Access Journals (Sweden)

    García-Guinea, J.


    Full Text Available Albite sodium feldspar is studied by thermoluminescent methods using the blue region of the spectra (circa 400nm and the possible uses as a dosimeter are explored. The light emission of the spectra bands of natural and irradiated albite under X and gamma rays are determined using automated RISØ thermoluminescence equipment. Albite is a potential material to be used as retrospective dosimeter due to its good blue thermoluminescence characteristics in good agreement with the dosimetric requirements. It is sensitive to radiation, possesses a good linearity (0.06-8Gy, shows an acceptable stability in time, it is highly reproducible and can detect low levels of dose (60mGy. The TL glow curves emission exhibit a very complex structure associated to a continuous trap distribution. This behaviour could be explained as a consequence of a dynamic creation-annihilation of a [AlO4/alkali]+ and [AlO4]o centres.

    Se estudian las posibilidades dosimétricas de la albita (feldespato sódico por métodos termoluminiscentes utilizando la región espectral del azul (alrededor de los 400nm. Se registran las posiciones espectrales de emisión de luz de este material irradiado con rayos X y con radiación gamma en un equipo automático de termoluminiscencia Risø. La albita puede ser empleada potencialmente en el campo de la reconstrucción de dosis post-accidental ya que sus propiedades termoluminiscentes en la región espectral del azul presentan buenas características dosimétricas. Se observa que la albita es muy sensible a la radiación, presenta una excelente linealidad con la dosis (0.06-8Gy, muestra una gran estabilidad con el tiempo, tiene reproducibilidad aceptable y puede detectar bajos rangos de dosis (60mGy. Sus curvas de termoluminiscencia tienen una estructura compleja asociada a una distribución continua de trampas en todo el rango de temperaturas. Este comportamiento podría explicarse como consecuencia de la formación-aniquilación din

  11. Eclogite-High-Pressure Granulite Belt in Northern Edge of the Archean North China Craton

    Institute of Scientific and Technical Information of China (English)


    The discovery of retrograded eclogites and high-pressure basic granulites in the joining region of Hebei-Shanxi-Inner Mongolia (HSIM) abandon the old thoughts that Archean granulites in the North China craton are of middle or low pressure facies and promote the reconsideration of Early Precambrian cratonization tectonic process, and reveal the geological fact that the scale, rigid behavior and geological structure of Archean cratonic blocks have strong similarities to the present fundamental plate tectonics, which suggest new tectonic mechanism to understand the early continental evolution of the North China craton. (1) The retrograded eclogites and high-pressure granulites constitute a ENE-NE-striking structure-rock zone termed as the Sanggan structural belt. (2) The retrograded eclogites are closely associated with high-pressure granulites. We can call this belt a transitional eclogite-granulite facies metamorphic belt. Petrographically three metamorphic stages, at least, in the retrograded eclogite can be distinguished. ① The main mineral assemblage is composed of garnet+clinopyroxene+quartz+rutile. The mineral inclusions in garnet are fine-grained quartz, rutile and small inclusions of fine-grained second stage mineral aggregate. This aggregate consists of hypersthene+albite, and has the typical texture of small hypersthene core surrounded by albite micro-grained grains. ② The second mineral assemblage is represented by corona of garnet and symplectite of clinopyroxene. The corona of garnet is composed of hypersthene+plagioclase+clinopyroxene+a minor amount of quartz and magnetite. The symplectite of clinopyroxene is composed of hypersthene + albite+clinopyroxene. The secondary mineral assemblage along boundaries between quartz and garnet (or clinopyroxene) is fine-grained aggregate of hypersthene and clinopyroxene. ③ The third retrograded metamorphic minerals are mainly amphiboles replacing pyroxenes and plagioclases replacing garnets. The estimated

  12. Metamorphic evolution of the high-pressure metamorphic rocks from the Kemer area (Biga Peninsula, NW Turkey): Implications for the accretionary continental growth and closure of the Intra-Pontide Ocean (United States)

    Aygül, M.; Topuz, G.; Satır, M.


    The northwestern part of the Biga Peninsula, NW Turkey, corresponds to the so-called Intra-Pontide suture, separating the Rhodope-Strandja zone to the north and Sakarya zone to the south. This suture zone is marked by the exposures of high-pressure metamorphics, oceanic accretionary complexes and ophiolites, which are widely covered by Eocene to Miocene volcanics and volcano-clastics, and crosscut by Eocene to Miocene granites. The Kemer area is one of the key-areas where high-pressure metamorphics and an ophiolitic mélange were widely exposed. This contribution deals with the metamorphic evolution of the Kemer high-pressure rocks, and their implications for the geodynamic evolution. The Kemer high-pressure rocks comprise predominantly micaschist, calcschist, marble and minor metabasite and serpentinite. The micaschists contain mineral assemblages involving garnet, phengite (3,30-3,44 c.p.f.u.), paragonite, epidote, chlorite, albite and titanite, and the metabasites consists of garnet, barrosite, albite, chlorite, epidote, albite and titanite. The equilibrium conditions are poorly constrained as 550 ± 50 °C temperature and >8-10 kbar pressure by Fe-Mg partitioning between garnet and phengite, and phengite-barometry, respectively. Timing of the high-pressure metamorphism is constrained as 84-64 Ma by Rb-Sr phengite-whole rock dating on four samples. Although the obtained age values display a wide scatter, they are consistent with geochronological data from the neighboring high-pressure areas: 86 ± 2 Ma from the Şarköy blueschists (Topuz et al. 2008) and 65-69 Ma from the Çamlıca garnet-micaschists (Okay and Satır, 2000). These data in conjunction with those from the literature suggest that Late Cretaceous represent a time of substantional accretionary continental growth related to the northward subduction of the Intra-Pontide Ocean. The closure of the Intra-Pontide Ocean is constrained between Late Cretaceous and Eocene, because Eocene volcanics and volcano

  13. LCT pegmatites from the Wodgina pegmatite district, Western Australia (United States)

    Richter, Lisa; Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard


    The lithium-cesium-tantalum (LCT) pegmatites from the Mt. Tinstone and Mt. Cassiterite open pits are located within the Wodgina pegmatite district, about 130 km south of Port Hedland, Western Australia. The albite-spodumene and albite-type pegmatites of the Wodgina pegmatite district are currently mined for tin, tantalum and niobium. The pegmatites are hosted within the Archean East-Pilbara Granite-Greenstone Terrane linked to the fertile Numbana monzogranite that forms part of the Yule Granitoid Complex. Granitic melt intruded into metasedimentary rocks (~2.8 Ga) and formed a series of pegmatite sheets, dikes and irregular structures. These pegmatites are characterized by a high melt fractionation that led to the formation of pegmatitic minerals, containing high concentrations of rare elements, such as Ta, Nb, Li, Rb and Cs. The pegmatites from the Mt. Tinstone sheet open pit, which were investigated within this study, comprises four internal zones consisting of six mineral assemblages, dominated by quartz, albite and white mica, with K-feldspar and spodumene as major or minor constituents. Distribution patterns of cassiterite and Ta-Nb-Sn-oxide minerals (ixiolite/wodginite, tantalite/columbite and microlite) can be observed within the four different pegmatite zones. The contact zones are enriched in cassiterite, ixiolite and microlite; border zones reveal high concentrations of cassiterite, ixiolite and tantalite; the intermediate units are characterized by a moderate enrichment of the ore minerals; whereby core zones host almost no significant contents of the minerals mentioned above. Distribution of Ta-Nb-Sn-oxides within the zones and Mn/(Mn+Fe) and Ta/(Ta+Nb) ratios are indicators for melt fractionation, and change from the core zones to the outermost contact zones, as well as from north to south. Electron microprobe analyses on white mica show the existence of fractionation trends from more primitive white mica of the core zones (zinnwaldite) to higher

  14. Juvenile Japan. Hydrothermal activity of the Hida-Gaien belt indicating initiation of subduction of proto-pacific plate in ca. 520 Ma

    International Nuclear Information System (INIS)

    This paper examines the early stage of the geotectonic history of the Japanese Islands on the basis of finding hydrothermal jadeitite including zircons of ca. 520 Ma in serpentinite melange of the Itoigawa-Omi area of the Hida-Gaien belt, Central Japan. Hydrothermal jadeitite contains euhedral jadeite in natrolite veins and patches, and consists of jadeite-albite and jadeite-natrolite without quartz. These minerals were crystallized from an aqueous fluid phase at the low-pressure and high-temperature side of the reaction boundary of albite=jadeite + quartz in the system NaAlSiO4-SiO2-H2O. The occurrence of rounded relict hornblende mantled by omphacite rimmed by fine-grained aggregates of jadeite in the matrix of jadeite and albite suggests a pervasive hydrothermal fluid flow, through which metabasite was extensively replaced by jadeitite. This rather high-temperature hydrothermal activity of ca. 520 Ma did not occur in an ordinary subduction zone but in a newly-formed mantle wedge suffering severe hydration from a subducting slab. Recently accumulated U-Pb ages of zircon of ca. 450-500 Ma from paleozoic sediments and granitic rocks of the Hida-Gaien belt were due to initiation of subduction followed by subduction zone magmatism. Protolith of serpentinite in the Hida-Gaien belt includes highly depleted harzburgite, thus requiring tectonic setting of a high-temperature-rift zone rather than a low-temperature-slow spreading ridge. Subduction was initiated at ca. 520 Ma along the boundary between low-density harzburgitic rift zone peridotite and lherzolitic spreading ridge peridotite with a slightly higher density, resulting in the common occurrence of harzburgitic serpentinite in the oldest part of the accretionary complex of Southwest Japan. An area including the Japanese Islands was born around the Yangtze block by the breaking up of the Rodinia supercontinent, because the oldest K-Ar age of biotite actinolit rock of 672 Ma (Matsumoto et al., 1981) and the

  15. Rare earth element geochemistry and petrogenesis of miles (IIE) silicate inclusions (United States)

    Hsu, Weibiao


    An ion probe study of rare earth element (REE) geochemistry of silicate inclusions in the Miles IIE iron meteorite was carried out. Individual mineral phases among inclusions have distinct REE patterns and abundances. Most silicate grains have homogeneous REE abundances but show considerable intergrain variations between inclusions. A few pyroxene grains display normal igneous REE zoning. Phosphates (whitlockite and apatite) are highly enriched in REEs (50 to 2000 × CI) with a relatively light rare earth element (LREE)-enriched REE pattern. They usually occurred near the interfaces between inclusions and Fe host. In Miles, albitic glasses exhibit two distinctive REE patterns: a highly fractionated LREE-enriched (CI normalized La/Sm ˜15) pattern with a large positive Eu anomaly and a relatively heavy rare earth element (HREE)-enriched pattern (CI-normalized Lu/Gd ˜4) with a positive Eu anomaly and a negative Yb anomaly. The glass is generally depleted in REEs relative to CI chondrites. The bulk REE abundances for each inclusion, calculated from modal abundances, vary widely, from relatively depleted in REEs (0.1 to 3 × CI) with a fractionated HREE-enriched pattern to highly enriched in REEs (10 to 100 × CI) with a relatively LREE-enriched pattern. The estimated whole rock REE abundances for Miles are at ˜ 10 × CI with a relatively LREE-enriched pattern. This implies that Miles silicates could represent the product of a low degree (˜10%) partial melting of a chondritic source. Phenocrysts of pyroxene in pyroxene-glassy inclusions were not in equilibrium with coexisting albitic glass and they could have crystallized from a parental melt with REEs of ˜ 10 × CI. Albitic glass appears to have formed by remelting of preexisting feldspar + pyroxene + tridymite assemblage. Yb anomaly played an important role in differentiation processes of Miles silicate inclusions; however, its origin remains unsolved. The REE data from this study suggest that Miles, like

  16. Numerical Simulation of Plagioclase Growth During Magma Storage and Ascent (United States)

    Melnik, O. E.; Gorokhova, N. V.; Plechov, P.


    A mathematical model of plagioclase growth from a magmatic melt is developed. Plagioclase is one of the main rock-forming minerals. Plagioclase is composed of molecules of two types: anorthite and albite. Crystallization occurs as a result of component (albite and anorthite) diffusion to the boundary of the growing crystal and opposite diffusion of residual melt components. The model is based on multicomponent diffusion equations with the real dependencies between crystal and melt compositions, pressure and temperature. Mass conservation is applied as a boundary condition on a crystal-melt interface. Crystal growth rate depends on local magma undercooling in the vicinity of the crystal. We assume that the growth is in 1D and that the crystal is located in a cell with symmetry (no mass flux) conditions on the cell boundaries. Diffusion of components within the crystal is negligibly slow. Based on this model variation of plagioclase composition with respect of monotonic cooling or pressure drop is studied. It is shown that due to interplay between diffusion of melt components to crystal-melt interface and crystal growth rate crystal composition can vary in a non-monotonic way in response to linear decrease in temperature. A condition of presence of plagioclase zonation is obtained as a result of parametric studies. A growth of rims on plagioclase crystals related to magma ascent during dome building eruptions on Bezymianny volcano (Kamchatka) is simulated. Bezymianny Volcano supplies material to the Earth surface about every half a year. Eruptions of 2000, 2006 and 2007 were selected to determine the magma ascent conditions as the most typical for the last activity cycle. The role of initial conditions, crystal growth rate, the ratio between anorthite and albite diffusion rates and ascent conditions on the rim composition is investigated. The ascent conditions of magma for Bezymianny Volcano eruptions were reconstructed. Simulations suggest ascent from a pressure of

  17. Genesis of jadeite-quartz rocks in the Yorii area of the Kanto Mountains, Japan (United States)

    Fukuyama, Mayuko; Ogasawara, Masatsugu; Horie, Kenji; Lee, Der-Chuen


    This paper reports the results of U-Pb dating and REE (rare earth element) analysis of zircons separated from jadeite-quartz rocks within serpentinite mélanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain jadeite, albite, and quartz, with minor aegirine-augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a jadeite + quartz = albite reaction during formation of these jadeite-quartz rocks. Zircon crystals separated from the jadeite-quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the jadeite-quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U-Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino-Tanba-Chichibu accretionary complex in Japan. The age data indicate that the jadeite-quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The jadeite-quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be

  18. Particle velocity experiments in anorthosite and gabbro (United States)

    Boslough, M. B.; Ahrens, T. J.

    Shock wave experiments were conducted in San Gabriel anorthosite and San Marcos gabbra 10 11 GPa using a 40 mm-borne propellant gun. Particle velocities were measured directly at several points in each target by means of electromagnetic gauges. Hugoniot states were calculated by determining shock-transit time from the gauge records. Sound speeds indicate a loss of shear strength upon sock compression for both rocks, with the strength loss persisting upon release to zero stress om the anorthosite. Stress-density release paths in the anorthosite indicate possible transformation of albite to jadeite + (quartz or coesite), with the amount of material transformed increasing as a function of shock stress. Electrical interferene effects in the gabbro precluded the determination of accurate release paths for the rock.

  19. Can we recognize magmatic fluid inclusions in fossil sytems based on room-temperature phase relations and microthermometric bahavior

    Energy Technology Data Exchange (ETDEWEB)

    Bodnar, R. (Virginia Polytechnic Institute and State University, VA (USA))


    If the density and composition of magmatic fluid and how these properties vary as the system evolves are known, the room temperature phase relations and microthermometric behavior of fluid inclusions which have trapped these magmatic fluids are considered to be predictable. Using available experimental and theoretical data for the model system albite-H2O-NaCl, the salinity of the aqueous phase exsolving from melts crystallizing at various depths (pressures) in the crust were calculated. Consequently, the results of the analysis of the characteristics of fluid inclusions trapped during crystallization of a silicic melt indicated that great care should be exercised in the selection of fluid inclusions to investigate magmatic fluids. Furthermore, late hydrothermal inclusions and similar magmatic inclusions are considered to be distinguishable from one another based on mode of occurrence, presence of tiny opaque daughter phases in magmatic inclusions, and relative ages. 5 figs.

  20. Enhanced dissolution of silicate minerals by bacteria at near-neutral pH. (United States)

    Vandevivere, P; Welch, S A; Ullman, W J; Kirchman, D L


    Previous studies have shown that various microorganisms can enhance the dissolution of silicate minerals at low (8) pH. However, it was not known if they can have an effect at near-neutral pH. Almost half of 17 isolates examined in this study stimulated bytownite dissolution at near-neutral pH while in a resting state in buffered glucose. Most of the isolates found to stimulate dissolution also oxidized glucose to gluconic acid. More detailed analysis with one of these isolates suggested that this partial oxidation was the predominant, if not sole, mechanism of enhanced dissolution. Enhanced dissolution did not require direct contact between the dissolving mineral and the bacteria. Gluconate-promoted dissolution was also observed with other silicate minerals such as albite, quartz, and kaolinite. PMID:24190338

  1. Analysis by Sem, EDS and XRD of mineral and soil belonging to a Colonial oven from Jalenton Chiapas

    International Nuclear Information System (INIS)

    Analytical techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) have been applied in the study of ancient materials. The results from the study of several samples belonging to a colonial oven are present in this work. There were found sets of slides, acicular and tubular shapes as well as porous surfaces and rose-like structures. EDS revealed high concentrations of O, C, Pb, Ca, Fe and Al, and minor quantities of Si, Zn, Mg, Na, S, K, Ti and Ni. Were identified the crystalline phases such as calcite, aragonite, albite; as well some phases associated with iron and lead compounds like: iron oxides, magnetite, hematite, goethite, kirschtanite, lead oxides, litargite, wititte, and cerusite. According to the obtained results that it is considered a kiln of oxygenated mineral to lead smelting. (Author)

  2. Analysis by Sem, EDS and XRD of mineral and soil belonging to a Colonial oven from Jalenton Chiapas

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza A, D.; Carapia M, L.; Rodriguez L, V. [Instituto Nacional de Investigaciones Nucleares, Salazar, Estado de Mexico C.P. 52045 (Mexico); Torres, L.; Lee, T. [Instituto de Investigaciones Antropologicas, Ciudad Universitaria C.P. 04500 Mexico D.F. (Mexico); Franco, F. [Departamento de Materiales. Area de Materiales. UAM Azcapotzalco, Mexico D.F. (Mexico)


    Analytical techniques such as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) have been applied in the study of ancient materials. The results from the study of several samples belonging to a colonial oven are present in this work. There were found sets of slides, acicular and tubular shapes as well as porous surfaces and rose-likestructures. EDS revealed high concentrations of O, C, Pb, Ca, Fe and Al, and minor quantities of Si, Zn, Mg, Na, S, K, Ti and Ni. Were identified the crystalline phases such as calcite, aragonite, albite; as well some phases associated with iron and lead compounds like: iron oxides, magnetite, hematite, goethite, kirschtanite, lead oxides, litargite, wititte, and cerusite. According to the obtained results that it is considered a kiln of oxygenated mineral to lead smelting. (Author)

  3. Petrology of plagiogranite from Sjenica, Dinaridic Ophiolite Belt (southwestern Serbia) (United States)

    Milovanović, Dragan; Srećković-Batoćanin, Danica; Savić, Marija; Popovic, Dana


    The Sjenica plagiogranite occurs in the southern part of the Dinaridic Ophiolite Belt, 5 km northwest of Sjenica. The main minerals are albite with strongly altered biotite (replaced with chlorite), with occasional amphibole (magnesio hornblende to tschermakite) and quartz. An enclave of fine-grained granitic rocks with garnet grains was noted too. Secondary minerals are calcite and chlorite (daphnite). Major, trace and REE geochemistry coupled with field observations support a model by which the Sjenica plagiogranite could be formed by fractional crystallization of mantle origin mafic magma in a supra-subduction zone setting. Occurrences of calcite and chlorite nests in the Sjenica plagiogranites revealed that these rocks underwent hydrothermal alteration due to intensive sea water circulation in a sub-sea-floor environment.

  4. Physicochemical study of ceramics from Pre classic of Cuicuilco 'C' Mexico, methodology to define origin of raw material; Estudio fisico-quimico de ceramica del Preclasico de Cuicuilco 'C' Mexico. Metodologia para definir procedencia de materia prima

    Energy Technology Data Exchange (ETDEWEB)

    Badillo S, A.; Sanchez P, S. [Escuela Nacional de Antropologia e Historia INAH, Periferico Sur y Zapote s/n, Col. Isidro Fabela, Delegacion Tlalpan, Mexico D.F. (Mexico); Perez C, M.A. [Proyecto Arqueologico de Cuicuilco, DEA-INAH, Lic. Verdad 3, Col. Centro (Mexico); Jimenez D, G. [Instituto de Investigaciones Antropologicas de la UNAM, Ciudad Universitaria, 04510 Mexico D.F. (Mexico); Aguilar F, M.; Zorrilla C, C.; Arenas A, J.A. [IFUNAM, Circuito de la Investigacion Cientifica s/n, Ciudad Universitaria, 04510, Mexico D.F. (Mexico)]. e-mail:


    Cuicuilco has been considered one of the most important centers during the Formative Period (1000 - 0 b. C.) in the south of Mexico Basin, mainly, due its dimensions. Because of the Xitle volcano eruption, its occupation decreases around 200 b. C. This paper presents the results of a multidisciplinary investigation about ceramic material from Cuicuilco 'C', located in the south of Mexico City, and sediments from different places near to it. The analysis was done by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X- Ray Diffraction (XRD). Its results show the presence of Si, O, Fe and Al as majority elements, and crystalline phases as albite, hematite, quartz, maghemite and cristobalite. Chemical elements identified at ceramic samples has been submitted to an statistical analysis in order to be compared with the results of analyzed sediments, to determinate the raw material origin. (Author)


    Directory of Open Access Journals (Sweden)

    Vladimir Majer


    Full Text Available Metharyolites of Vranica mountain are roks of emphasized porphyritic texture containing phenocrysts of quartz, K.feldspar and very rarely albite. The groundmass is microcrystallinic, characterized by finegrained phengite, biotite and area consisting of granophyric intergrowths of quartz and feldspar. Accessory minerals are ilmenite, rutila, apatite, zircon and chlorite. Metarhyolites are peraulminous rocks (PI=1.-4.1 having dominantly potassium character (K2O/Na2O=1,3-13,8. Incompatible elements are enriched relative to the normalizing chondrite composition, pointing to the crustal origin of metarhyolite magma. Although phengites typically occur in high pressure rocks, it seems that phengites of metarhyolites of Vranica mountain belong to the seldom group of phengites occurring in the low to medium pressure rocks (the paper is published in Croatian.

  6. Characterization of Mesoamerican jade

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, R.L.; Sayre, E.V.; van Zelst, L.


    Jadeite occurring in the Motague River Valley of Guatemala has been characterized by neutron activation analysis and forms two district, phase-related groups. Comparison of the compositional profiles of Mayan jadeite artifacts reveals many specimens having profiles matching those of the Montagua source. Of particular interest are the large number of jadeite artifacts which show internal similarity yet have compositional patterns which are significantly different from the Montagua samples and Montagua-related artifacts. A few of the analyzed Costa Rican artifacts show patterns similar to those of the Motagua yet the vast majority fall within one of the two Costa Rican compositional groups. When considering the non-Motagua related Mayan artifacts, the analytical approach appears to be sufficiently sensitive so as to distinguish differences between the Chrome-green and Chichen-green material. Even two Honduran site specific groups of albite - cultural jade - form distinct groups.

  7. Mineral characterization of soil type ranker formed on serpentines occurring in southern Belgrade environs Bubanj Potok

    Directory of Open Access Journals (Sweden)

    Cekić Božidar Đ.


    Full Text Available The paper addresses the issue of health risk associated with the presence of chrysotile in the soil type ranker formed on massive serpentines occurring in the area of Bubanj Potok, a settlement located in the southern Belgrade environs, Serbia. Characterization of the ranker soil was conducted by scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and transmission 57Fe Mössbauer spectroscopy. Scanning electron microscopy figures showed regular shaped smectite (montmorillonite particles, aggregates of chlorite, and elongated sheets of serpentines minerals antigorite. X-ray diffraction analysis confirmed the presence of detrital mineral quartz polymorph as well as minor amounts of other mineral species. Micro-Raman spectroscopy identified the presence of dominant minerals, such as montmorillonite, kaolinite, muscovite, gypsum, calcite, albite, amphiboles (hornblende/kaersutite and orthoclase. Important polymorph silica modifications of quartz, olivine (forsterite, pyroxene (enstatite/ferrosilite, diopside/hedenbergite, and serpentine (antigorite/lizardite/chrysotile were identified.

  8. Time-temperature evolution of microtextures and contained fluids in a plutonic alkali feldspar during heating (United States)

    Parsons, Ian; Fitz Gerald, John D.; Lee, James K. W.; Ivanic, Tim; Golla-Schindler, Ute


    Microtextural changes brought about by heating alkali feldspar crystals from the Shap granite, northern England, at atmospheric pressure, have been studied using transmission and scanning electron microscopy. A typical unheated phenocryst from Shap is composed of about 70 vol% of tweed orthoclase with strain-controlled coherent or semicoherent micro- and crypto-perthitic albite lamellae, with maximum lamellar thicknesses 700°C, and after >48 h at 700°C, all such regions were essentially compositionally homogeneous, as indicated by X-ray analyses at fine scale in the transmission electron microscope. Changes in lamellar thickness with time at different T point to an activation energy of ~350 kJmol-1. A lamella which homogenised after 6,800 h at 600°C, therefore, would have required only 0.6 s to do so in the melting interval at 1,100°C. Subgrains in patch perthite homogenised more slowly than coherent lamellae and chemical gradients in patches persisted for >5,000 h at 700°C. Homogenisation T is in agreement with experimentally determined solvi for coherent ordered intergrowths, when a 50-100°C increase in T for An1 is applied. Homogenisation of lamellae appears to proceed in an unexpected manner: two smooth interfaces, microstructurally sharp, advance from the original interfaces toward the mid-line of each twinned, semicoherent lamella. In places, the homogenisation interfaces have shapes reflecting the local arrangements of nanotunnels or pull-aparts. Analyses confirm that the change in alkali composition is also relatively sharp at these interfaces. Si-Al disordering is far slower than alkali homogenisation so that tweed texture in orthoclase, tartan twinning in irregular microcline, and Albite twins in albite lamellae and patches persisted in all our experiments, including 5,478 h at 700°C, 148 h at 1,000°C and 5 h at 1,100°C, even though the ensemble in each case was chemically homogeneous. Nanotunnels and pull-aparts were modified after only 50 min

  9. Origin of peak and retrograde assemblages during Grenvillian orogeny from garnet-staurolite bearing mica schist of Bhilwara Supergroup, NW India: constraints from pseudosection modelling (United States)

    Prakash, Abhishek; Saha, Lopamudra; Sarkar, Saheli


    Fractionation of components due to formation of garnet porphyroblasts during prograde metamorphism, have been constrained from pseudosection analyses. Such fractionation process leads to changes in the effective bulk composition within the rock, which can be modelled with well-preserved growth zonation patterns in garnet porphyroblasts. On the contrary, textures and mineralogy in metamorphic rocks can be far more complex with different textural domains within a single rock preserving assemblages formed along different segments of the P-T paths or during different metamorphic events. Examples of such textures include pseudomorphs, reaction rims or coronae, symplectites formed by breakdown of both cores and rims of porphyroblasts. Apart from pressure and temperature, availability of fluids during metamorphic reactions plays important roles in defining mineral assemblages and textures. In this study we have constrained formation of garnet porphyroblasts and paragonite-albite-sillimanite-quartz-staurolite bearing domains within the mica schist from the Rajpura-Dariba sequence of the Bhilwara Supergroup in NW India. The mica schist is inter-layered with calc-silicates and quartzite and together the units form a NE-SW trending Grenvillian orogenic belt in southern part of Bhilwara Supergroup sequence. Within the mica schist, three distinct textural domains have been observed: (i) muscovite-biotite-quartz-feldspar bearing matrix foliation, (ii) garnet porphyroblasts within the matrix foliation, (iii) staurolite-paragonite-albite-staurolite-sillimanite-quartz bearing domains. Paragonite, albite and sillimanite occur exclusively in the pseudomorph domains. Garnet porphyroblasts show variation in compositions from cores (Spessartine0.14 Grossular0.10 Pyrope0.12 Almandine0.72) to rims (Spessartine0.09Grossular0.15Pyrope0.12Almandine0.75). The average XMg contents of staurolite and matrix biotite are 0.21 and 0.57 respectively. Pseudosections have been constructed from the

  10. International Uranium Resources Evaluation Project (IUREP) orientation phase mission summary report: Cameroon

    International Nuclear Information System (INIS)

    A report has recently been published which describes the findings of the International Uranium Resources Evaluation Project (IUREP) Mission to Cameroon. The IUREP Orientation Phase Mission to Cameroon estimates the Speculative Resources of that country to be in the order of 10 000 tonnes uranium for syenite-associated U-deposits in southern Cameroon, and in the order of 5 000 tonnes uranium for uranium deposits associated with albitized and desilicified late tectonic Panafrican granites (episyenite) and Paleozoic volcanics in northern Cameroon. No specific tonnage is given for Francevillian equivalents (DJA-Series) and for Mesozoic and Cenozoic sedimentary basins, which are thought to hold limited potential for sandstone hosted uranium. However the Douala basin, consisting of mixed marine and continental sequences merits some attention. No specific budget and programme for uranium exploration are proposed for Cameroon. Instead specific recommendations concerning specific potential environments and general recommendation concerning the methodology of exploration are made. (author)

  11. Geology and age of the Lac a la Perdrix fenite, southern Gatineau district, Quebec

    International Nuclear Information System (INIS)

    The Lac a Ia Perdrix fenite lies in the Central Metasedimentary Belt of the Grenville Province. This 30 m wide fenite, adjacent to a narrow calciocarbonatite sill, replaces diopside-oligoclase gneiss and is composed of magnesio-arfvedsonite, aegirine, microcline, albite, and fluorapatite. Near the contact with carbonatite, it contains appreciable monazite and barite whereas aegirine virtually disappears. Fenitization probably took place early in the igneous stage of carbonatite development. A Pb/U monazite age of 1026 ± 2 Ma is thought to date fenite formation. Together with published data, this age shows that carbonatite intruded metamorphic rocks near the close of the Grenville Orogeny. (author). 33 refs., 4 tabs., 5 figs

  12. The mechanism of myrmekite formation deduced from steady-diffusion modeling based on petrography: Case study of the Okueyama granitic body, Kyushu, Japan (United States)

    Yuguchi, Takashi; Nishiyama, Tadao


    Myrmekite is an intergrowth texture consisting of vermicular quartz and albitic plagioclase (Ab 93An 7 in this study), typically occurring between K-feldspar and plagioclase. It occurs ubiquitously in both metamorphic and granitic rocks; however, its genesis has been an enigma. This paper describes myrmekite's petrography and discusses its genesis from the Okueyama granitic body (OKG), which is a young (14 Ma) granite in Southwest Japan with no evidence of deformation after solidification. The genesis of a newly observed texture, the 'reaction rim', will be also discussed in relation to myrmekite. The reaction rim is an albite layer (Ab 95An 5) with no vermicular quartz between K-feldspar and plagioclase, and it occasionally makes a composite texture with myrmekite. Both myrmekite and the reaction rim are accompanied by a diffusive boundary layer (Olg-layer) with a mean composition of oligoclase (Ab 75An 25) in the rim of neighboring plagioclase rim. The overall reactions in an open system for the formation of myrmekite and that for the reaction rim are derived based on the following two models: 1) one based on the assumption of conservation of solid volume with arbitrarily specified closure components, and 2) the other based on the assumption of closure of AlO 3/2 together with an arbitrarily specified volume factor. Steady diffusion modeling in an open system based on the overall reaction thus derived defines the stability field of myrmekite and of the reaction rim in terms of the ratios of phenomenological coefficients ( L-ratios). The steady diffusion models for the above two models have essentially the same features. Myrmekite is stable for large values (> 10) of LAlAl/ LCaCa, for moderate values of LAlAl/ LSiSi, and for only small values (vs. LAlAl/ LNaNa, and its dependence on LAlAl/ LSiSi is stronger than that of myrmekite. The reaction rim is stable only for large values of LAlAl/ LCaCa, which is consistent with the case of myrmekite. Exchange cycles for

  13. Le volcanisme cambrien du Maroc central : implications géodynamiquesThe Central Morocco Cambrian volcanism: geodynamic implications (United States)

    Ouali, Houssa; Briand, Bernard; Bouchardon, Jean-Luc; Capiez, Paul


    In southeastern Central Morocco, the Bou-Acila volcanic complex is considered of Cambrian age. In spite of low-grade metamorphic effect, initial volcanic texture and mineralogy can be recognized and volcanic rocks are dominated by dolerites and porphyric dolerites. The initial mineralogy is composed of plagioclases, pyroxenes and dark minerals. A secondary mineral assemblage is composed of albite, epidote, chlorite and calcite. According to their immobile elements compositions, the southeastern central Morocco metavolcanites are of within-plate continental tholeiites. This volcanism and those recognized in many other areas in Morocco confirm a Cambrian extensive episode within the Gondwana supercontinent. To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).

  14. Postvolcanic alteration and mobilization of uranium in the late jurassic volcanic rocks in northwest of Zhejiang province, China

    International Nuclear Information System (INIS)

    Calc-alkaline volcanic rocks of Jiande formation in the northwest of Zhejiang Province were formed by four cycles of volcanic acivities and underwent many times of thermal events. There were two types of hydrothermal metasomatic alterations of the rocks in volcanic terrain, one developed in postvolcanic period and another in mineralization period. In the terrain of acid rocks, postvolcanic hydrotermal metasomatic alteration is mainly characterized by albitization and sericitization. It was this post-diagenetic plane type of metasomatic alteration that ought about the mobilization of uranium which originally existed in volcanic rocks in varied forms. Afterwards, the activated uranium was extracted from rocks by flowing hydrothermal solution, and therefore, the uranium concentration in the hydrothermal solution was increasing. In the alteration environment along the rift, the uranium was deposited from the hydrothermal solution

  15. Mineralogy, geochemistry, porosity and redox properties of rocks from Forsmark. Compilation of data from the regional model volume for SR-Site

    International Nuclear Information System (INIS)

    This report is a compilation of the data acquired during the Forsmark site investigation programme on the mineralogy, geochemistry, redox properties and porosity of different rock types at Forsmark. The aim is to provide a final summary of the available data for use during the SR-Site modelling work. Data presented in this report represent the regional model volume and have previously been published in various SKB reports. The data have been extracted from the SKB database Sicada and are presented as calculated median values, data range and lower/upper quartile. The representativity of all samples used for the calculations have been evaluated and data from samples where there is insufficient control on the rock type have been omitted. Rock samples affected by alteration have been omitted from the unaltered samples and are presented separately based on type of alteration (e.g. oxidised or albitized rock)

  16. Secondary mineral-fluid equilibria in the Krafla and Namafjall geothermal systems, Iceland

    International Nuclear Information System (INIS)

    Aquifer fluid compositions and aqueous species distribution have been calculated for 22 samples collected from producing wells in the Krafla and Namafjall geothermal areas, Iceland. Overall mineral-solution equilibrium is rather closely approached in the aquifer beyond the depressurization zone around wells for all major components entering hydrothermal minerals. The minerals involved are in alphabetical order: albite, calcite, chlorite, epidote, K-feldspar (adularia), prehnite, pyrite, pyrrhotite, quartz and wairakite. Calculated saturation indices for OH-bearing Al-silicates show more scatter than for minerals of simpler composition. A large scatter is also observed for pyrite and pyrrhotite. The main uncertainty involved in calculating mineral saturation indices, particularly in the case of 'excess' enthalpy well discharges, lies in the model adopted to calculate the aquifer water composition and its aqueous species distribution and not in the quality of the thermodynamic data on the aqueous species and the minerals with the possible exception of epidote and Fe2+

  17. Mineralogy, geochemistry, porosity and redox properties of rocks from Forsmark. Compilation of data from the regional model volume for SR-Site

    Energy Technology Data Exchange (ETDEWEB)

    Sandstroem, Bjoern (WSP Sverige AB, Stockholm (Sweden)); Stephens, Michael B. (Geological Survey of Sweden, Uppsala (Sweden))


    This report is a compilation of the data acquired during the Forsmark site investigation programme on the mineralogy, geochemistry, redox properties and porosity of different rock types at Forsmark. The aim is to provide a final summary of the available data for use during the SR-Site modelling work. Data presented in this report represent the regional model volume and have previously been published in various SKB reports. The data have been extracted from the SKB database Sicada and are presented as calculated median values, data range and lower/upper quartile. The representativity of all samples used for the calculations have been evaluated and data from samples where there is insufficient control on the rock type have been omitted. Rock samples affected by alteration have been omitted from the unaltered samples and are presented separately based on type of alteration (e.g. oxidised or albitized rock)

  18. Boromuscovite, a new member of the mica group, from the Little Three mine pegmatite, Ramona district, San Diego County, California (United States)

    Foord, E.E.; Martin, R.F.; Fitzpatrick, J.J.; Taggart, J.E., Jr.; Crock, J.G.


    Boromuscovite, ideally KAl2(Si3B)O10(OH,F)2, in which [4]Al is replaced by B relative to muscovite, occurs as a late-stage, postpocket rupture mineral within the New Spaulding Pocket, main Little Three pegmatite dike. The mineral is white to cream colored and occurs as a porcelaneous veneer and coating on primary minerals. The average grain size is less than 3-4 ??m, but the coatings may be as much as 1 cm or more thick. Fragments of topaz, albite, elbaite, and other pocket minerals are included in the coating. The boromuscovite precipitated from a late-stage hydothermal fluid; it occurs only as a snowlike coating. Chemical composition, unit-cell parameters, Mohs hardness, cleavage, fracture, and optical properties are reported. -from Authors

  19. Contributions to the mineralogy, petrography and metallogeny of the Itataia phosphorus-uranium deposit, state of Ceara, Brazil

    International Nuclear Information System (INIS)

    The phosphorus-uranium mineralization of the Itataia deposit is unique. Most of the uranium is contained in the collophane (uraniferous fluorapatite) obtained through the transformation of metamorphic apatite of the country rocks (Itataia Group). A graphite-rich pelitic metasediment origin for the uranium and phosphorus is suggested. Initially, the rocks were subjected to isoclinal and homoclinal folding associated with overthrusting and regional metamorphism of the high amphibolite facies with some migmatization. The mineralization is epigenetic and dominated by sodium-rich metasomatic fluids. The mobilized quartz-feldspathic migmatites were transformed into collophane-albite-episyenites. The considerably thick markbles provided the conditions favoring an increase in the fluids pH which caused the precipitation of collophane concentrated in pockets and stockworks. (Author)

  20. Thermoluminescence properties of Chile Guajillo (paprika) Mexicano

    International Nuclear Information System (INIS)

    The thermoluminescence properties of the inorganic dust extracted from the Chile Guajillo (paprika) Mexicano, were studied in order to verify the possibility of using the TL technique to discriminate between irradiated and non irradiated peppers. The inorganic dust was found to consist of quartz 60%, albite (NaAlSi3O8) 30%, and ortose (KAlSi3O8) 10%. Its thermoluminescence dose response covers the wide dose range of 1Gy-10kGy, which was attributed mainly to feldspars. Its high sensitivity and its stability over 10 irradiation-readout cycles allow the application of a single grain-single aliquot regeneration dosimetry in Chile Guajillo (paprika). Evaluations based on trapping parameters show that thermal fading at room temperature for glow-peaks above 180 deg.. C, is not a problem in the dosimetry of paprika

  1. Dacite – siltstone peperite from Trlično at Rogatec, Eastern Slovenia

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    Polona Kralj


    Full Text Available Dacitic glassy lava flow at Trlično is surrounded by a dacite – siltstone peperite and peperitic breccia that underwent alteration, recognised in two, only a few metres thick zones. In the higher-temperature alteration zone, albite extensively replaces volcanic glass and primary plagioclases. The siltstone components are altered to microcrystalline quartz, iron oxides and interlayered illite/smectite clay minerals. This zone developed upon thermalmetamorphosis related to the transfer of heat from the cooling lava. In the lower temperature alteration zone, analcime occurs as the replacement of volcanic glass and pore- and fissure-filling, while the primary plagioclases and poorly lithified siltstone remained fairly unchanged. This zone developed under hydrothermal conditions related to the heating, circulation and reactions of pore waters in the sediment surrounding the lava flow.

  2. Micro-Raman and FT-IR spectroscopic studies of ceramic shards excavated from ancient Stratonikeia city at Eskihisar village in West-South Turkey (United States)

    Bahçeli, Semiha; Güleç, Gamze; Erdoğan, Hasan; Söğüt, Bilal


    In this study, micro-Raman and Fourier transformed infrared (FT-IR) spectroscopies, X-ray diffraction (XRD) and scanning electron microscope with energy dispersive X-ray (SEM-EDX) were used to characterize the mineralogical structures of pigments of four ceramic fragments in which one of them belongs to Hellenistic period (1st - IVth century BC) and other three ceramic shards belong to Early Rome (IVth century BC- 1st century AD) excavated from Stratonikeia ancient city. In the results of investigations on these four ceramic fragments, the various phases were identified: quartz, kaolinite, albit (or Na-feldspar), calcite, anastase, hematite and magnetite. Furthermore, the obtained findings indicate that firing temperature is about 800-850 °C for all the shards.

  3. MINERALOGIA E QUÍMICA DE SOLO DE VÁRZEA E SUAS SUSCEPTIBILIDADES NO PROCESSO DE TERRAS CAÍDAS NA COMUNIDADE DO DIVINO ESPÍRITO SANTO-AM / Mineralogy and chemistry of the lowland soil and its sensibilities in the process of lands falls in community Divino Espírito Santo (Amazonas, Brazil.

    Directory of Open Access Journals (Sweden)

    Regiane Campos Magalhães


    Full Text Available The study about the mineralogical and chemical lowland soils generate information to compose a current survey about the susceptibility of lowland soil to process Fallen Lands. With this purpose we studied five profiles the banks of the Solimões River, located in the municipality of Iranduba (AM. The information obtained allowed to determine the Neosoil Fluvic the study area has favorable conditions for cultivation with an average pH of 6.2, with high levels of Ca, Mg, K, P, micronutrients and zero Al content, with high levels of C and M. O. in the first layer and a decrease in depth. Thus, Neosoil Fluvic was characterized as Tb eutrophic, with base saturation above 50%, with good CTC. The mineralogy was homogeneous in all profiles, with a predominance of primary minerals: Quartz, Albite and rutile, with low proportions of clay minerals Muscovite, Kaolinite, Muscovite-Illite interstratified and Illite.

  4. Microstructural analysis from archaeological sculptures of the Olmeca culture

    International Nuclear Information System (INIS)

    This work presents the results obtained from the characterization of a series of samples belonging to different monuments of the Olmec culture. These monuments are exhibited in the archaeological site of La Venta, Tabasco, Mexico. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to determine the crystalline phases that characterise the samples, these phases are associated to different morphology. The elemental analysis exhibits the presence mainly of such elements as C, Si, O, Al, Na, Ca and in less abundance Ti, K, Cr, Ni and Mn were determined. The morphology is characterized by the presence of plane tabular structures, schists, extended slates and clusters of irregular grain. Such crystal phases as anorthite, albite, sanidine, zinnwaldite and clinochlore were identified. These phases are associated with such type of materials as feldspars and mica. All the identified phases are noted for presenting near perfect exfoliation. (Author)

  5. The Polumir granite: Addititional data on its origin

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    Vukov Milenko S.


    Full Text Available The Polumir granite is exposed on several localities due to erosion, and its chemical and mineral composition is presented in this paper. It is built of K-feldspar, plagioclase, myrmekite, metasomatic albite, biotite, muscovite and quartz, while apatite, magnetite, monazite, allanite and zircon are present as accessory minerals. According to its chemical and mineral composition and rock chemistry (trace and REE elements the Polumir granite is leucocratic, sin-collisional, with S-type characteristics. It crystallized at temperature of about 650°C and under pressure of 2-4 kbar. Results of isotope analyses (K-Ar method on biotites indicate that the Polumir granite was formed during the Miocene (14-19 Ma and it has undergone subsequent weak remobilization afterwards.

  6. Late sodic metasomatism evidences in bimodal volcanic rocks of the Acampamento Velho Alloformation, Neoproterozoic III, southern Brazil

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    Delia Del Pilar M. de Almeida


    Full Text Available A mineralogical study was carried out in mafic and felsic volcanic rocks of the Acampamento Velho Alloformation at Cerro do Bugio, Perau and Serra de Santa Bárbara areas (Camaquã Basin in southern Brazil. The Acampamento Velho bimodal event consists of two associations: lower mafic at the base and upper felsic at the top. Plagioclase and alkali-feldspar were studied using an electronic microprobe, and magnetite, ilmenite, rutile, illite and alkali-feldspar were investigated through scanning electron microscopy. The rocks were affected by a process of late sodic autometasomatism. In mafic rocks, Ca-plagioclase was transformed to albite and pyroxenes were altered. In felsic rocks, sanidine was partially pseudomorphosed, generating heterogeneous alkali-feldspar. In this association, unstable Ti-rich magnetite was replaced by rutile and ilmenite. In mafic rocks, the crystallization sequence was: (1 Ti-rich magnetite (?, (2 pyroxene and Ca-plagioclase, (3 albite (alteration to Ca-plagioclase, (4 sericite, chlorite and calcite (alteration to pyroxene, and kaolinite (alteration to plagioclase/albite. In felsic rocks: (1 zircon, (2 Ti-rich magnetite, (3 sanidine, (4 quartz. The introduction of late Na-rich fluids, generated the formation of (5 heterogeneous alkali-feldspar, (6 ilmenite and rutile from the Ti-rich magnetite, (7 albite in the spherulites. Finally, alteration of sanidine, vitroclasts and pumice to (8 illite.Um estudo mineralógico de detalhe foi realizado nas rochas vulcânicas da Aloformação Acampamento Velho nos Cerros do Bugio, Perau e Serra de Santa Bárbara (Bacia do Camaquã, sudeste do Brasil. Este evento bimodal é constituído por duas associações: máfica inferior na base e félsica superior no topo. Foram estudados grãos de plagioclásio e feldspato alcalino com o uso de microssonda eletrônica, sendo que, magnetita,ilmenita, rutilo e ilita além de feldspato alcalino foram pesquisados através do microscópio eletr

  7. Environmental radiation dosimetry using red infrared-stimulated luminescence (R-IRSL) from feldspar

    International Nuclear Information System (INIS)

    New observations of red infrared stimulated luminescence from feldspar were investigated. Sliced granite samples showed over 600 nm (far-red) IRSL emission in addition to yellow and green emissions. The thermally annealed feldspar samples evidently increased their sensitivity of red-IRSL (R-IRSL). Particularly the oxidative annealing treatment offered higher sensitivity of R-IRSL than the reductive annealing treatment. The properties of R-IRSL such as dose-response and preheat temperature dependency were examined for the purpose of use of new luminescence dosimetry and dating. Microcline grains showed higher R-IRSL emission and more rapid dose saturation over 200 Gy dose of X-ray irradiation than albite grains. (author)

  8. Physicochemical study of ceramics from Pre classic of Cuicuilco 'C' Mexico, methodology to define origin of raw material

    International Nuclear Information System (INIS)

    Cuicuilco has been considered one of the most important centers during the Formative Period (1000 - 0 b. C.) in the south of Mexico Basin, mainly, due its dimensions. Because of the Xitle volcano eruption, its occupation decreases around 200 b. C. This paper presents the results of a multidisciplinary investigation about ceramic material from Cuicuilco 'C', located in the south of Mexico City, and sediments from different places near to it. The analysis was done by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X- Ray Diffraction (XRD). Its results show the presence of Si, O, Fe and Al as majority elements, and crystalline phases as albite, hematite, quartz, maghemite and cristobalite. Chemical elements identified at ceramic samples has been submitted to an statistical analysis in order to be compared with the results of analyzed sediments, to determinate the raw material origin. (Author)

  9. Crystallization, flow and thermal histories of lunar and terrestrial compositions (United States)

    Uhlmann, D. R.


    Contents: a kinetic treatment of glass formation; effects of nucleating heterogeneities on glass formation; glass formation under continuous cooling conditions; crystallization statistics; kinetics of crystal nucleation; diffusion controlled crystal growth; crystallization of lunar compositions; crystallization between solidus and liquidus; crystallization on reheating a glass; temperature distributions during crystallization; crystallization of anorthite and anorthite-albite compositions; effect of oxidation state on viscosity; diffusive creep and viscous flow; high temperature flow behavior of glass-forming liquids, a free volume interpretation; viscous flow behavior of lunar compositions; thermal history of orange soil material; breccias formation by viscous sintering; viscous sintering; thermal histories of breccias; solute partitioning and thermal history of lunar rocks; heat flow in impact melts; and thermal histories of olivines.

  10. Geochemical characterization and comparative study of plagiogranites from the South portuguese and Ossa-Morena Zones (SW Iberian Massif, Spain); Caracterizacion geoquimica y estudio comparativo de plagiogranitos de las Zonas Surportuguesa y Ossa-Morena (SO del Macizo Iberico, Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Bellido, F.; Diez-Montes, A.; Sanchez-Garcia, T.


    Plagiogranites and albitic rocks belonging to contrasted magmatic associations of different ages and geo dynamic environments outcrop in Ossa-Morena (OMZ) and Sur portuguese (SPZ) Zones. OMZ plagiogranites are related with Cambrian-Ordovician rifting and represent a part of the felsic members of a bimodal magmatic suite and show oceanic plagiogranites affinities. SPZ plagiogranites are related with a Carboniferous volcano-plutonic calc-alkaline suite related with Variscan Orogeny. Both plagiogranites show many similar petrological and geochemical characteristics but display some different immobile elements ratios as La/Nb, Th/Nb, Th/La that are unaltered by metamorphism, magmatic differentiation and alteration processes and prove differences in their sources. SPZ plagiogranites show a more compositional homogeneity than OMZ ones. This is interpreted as a proof of cogenetic origin for SPZ plagiogranites and heterogeneous origin for OMZ plagiogranites, derived from the mix of different sources (astenospheric, lithospheric and crustal). (Author) 23 refs.

  11. Zeolitización de rocas andesíticas

    Directory of Open Access Journals (Sweden)

    Plana, F.


    Full Text Available The study of some andesites from King George Island (South Shetland Islands, Anctartica has pointed out the existence of a hydrothermal alteration process going rise to a zeolitic secondary minerals of low-temperature assemblages. Two paragenesis have been identified (Smectite-Bytownite-Mordenite, Smectite-Albite-Laumontite which reflecting different conditions durign the hydrothermal alteration of these andesitic rocksEl estudio de rocas andesíticas de la Isla King George (Archipiélago de las Shetland del Sur, Antártida pone de manifiesto la existencia de procesos de alteración hidrotermal con la formación de minerales zeolíticos secundarios pertenecientes a asociaciones de baja temperatura. Se han identificado dos paragénesis (Esmectitas-Bytownita-Mordenita, Esmectitas-AlbitaLaumontita que reflejan distintas condiciones durante la alteración hidrotermal de dichas rocas andesíticas.

  12. Geochemical modeling of groundwater in southern plain area of Pengyang County, Ningxia, China

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    Pei-yue LI


    Full Text Available The purpose of the paper is to study the evolution mechanism of hydrochemical field and to promote unpredictable benefits to the living standards of local people and to the local economy in the southern plain area of Pengyang County, Ningxia, China. Based on the understanding of the hydrogeological conditions in Pengyang County, the chemical evolution characters of groundwater in the plain area were analyzed. PHREEQC geochemical modeling software was used to perform a hydrochemical modeling for water-rock interaction and to analyze quantitatively the evolution processes and the forming mechanism of the local groundwater. Geochemical modeling results showed that along path ①, Na+ adsorption played the leading role in the precipitation process and its amount was the largest, up to 6.08 mmol/L, cation exchange was obvious on path ①, while on simulated path ② albite took up the largest amount of dissolution, reaching 9.06 mmol/L, the cation exchange was not obvious along path ②. Some conclusions were summarized according to the modeling results that along the groundwater flow path, calcite and dolomite in the whole simulation showed oversaturated status with a precipitation trend, while the fluorite and gypsum throughout the simulated path were not saturated and showed a dissolution trend. Total dissolved solids (TDS increased and water quality become worse along the flow path. Dissolution reactions of albite, CO2 and halite, exchange adsorption reaction of Na+ as well as precipitation action of sodium montmorillonite and calcite are the primary hydrogeochemical reactions which resulted in changes of hydrochemical ingredients.

  13. Feldspar-fluid interactions in braid microperthites: pleated rims and vein microperthites (United States)

    Lee, Martin R.; Waldron, Kim A.; Parsons, I.; Brown, William L.

    Braid microperthitic alkali feldspars in the Klokken, South Greenland and Coldwell, Ontario syenite intrusions have bulk-compositional variations along grain boundaries called pleated rims. These, together with vein microperthites in aplites which cross-cut the syenites, have been investigated by SEM and TEM. We distinguish two main types of pleated rims, ``arched '' and ``parallel-sided '', consisting of alternating Ab- and Or-rich areas on (001), which are 0.5-300 μm in length normal to (010) and 0.2-20 μm in width along (010). The smallest pleats, which occur on intracrystalline boundaries in Klokken feldspars, are fully coherent and composed of low albite and low microcline. Above the heads of some of the coarser pleats, braid microperthite grades into a film crypto- and micro-perthite and antiperthite microtexture called a ``transitional zone'' containing roughly planar lamellae of low albite and tweed orthoclase. During pleat development, local alternating volumes form in which the proportions of the phases differ ( phase separation) and the morphology of the intergrowths changes from braided to straight in response to this change in local bulk composition. Straightening is also accompanied by transformation of low microcline to tweed orthoclase. The coarsest pleats, which occur along grain boundaries in feldspars from the Coldwell syenite, are semi- or in-coherent and have a thick coherent and semicoherent transitional zone. Coarsening of pleats and development of the transitional zone has been facilitated by diffusion of ``water'' into grain interiors. In many cases, pleated rims have suffered deuteric alteration, by dissolution-reprecipitation processes, through the action of a water-rich fluid from the grain boundary, in which tweed orthoclase was transformed into irregular microcline and micropores developed. Vein microperthites in aplites from Klokken, and by extension the vein microperthites almost universal in most alkali granites, are interpreted

  14. Effects of fluid-assisted diffusion on texture strength in a mylonitised metagabbro (United States)

    Gardner, Joseph; Wheeler, John; Mariani, Elisabetta


    Most rocks are polyphase materials yet many studies of rock texture tend to isolate the behaviour of individual phases. Characterisation of interaction between phases can yield useful information about the deformation behaviour of real rocks. Our work focuses on a broadly two phase mixture of albite and clinozoisite in mylonitised metagabbros, and how these two phases may have interacted to create, maintain and/or weaken the variable strength CPOs observed in each phase. Intriguingly, the rocks have deformed primarily by diffusion-accommodated processes, which are traditionally thought to weaken or destroy an existing CPO. Our data suggest that diffusion can preserve strong textures. Plagioclase in metamorphosed gabbros from a km-scale extensional shear zone in the NW Italian Alps (Gressoney Shear Zone) has undergone (to a first order) breakdown to albite (Ab) + clinozoiste (Cz) at greenschist facies. Grain size reduction via nucleation of product grains, plus the effects of Zener pinning, lead to an average grain size of 100 μm, which suggests grain growth elsewhere in the matrix was indeed inhibited by the presence of a second phase. Discrete CPO bands vary in size. Variations in grain and grain boundary characteristics between domains are being quantified to investigate whether the way an inherited orientation relates to L-S sample geometry may have had any control over degree of dissolution (implied from grain morphology) within domains. Whether volume fraction of Cz in (what remains of) each domain has influenced dissolution will also be characterised by quantifying grain shape, orientation and distribution of phases in individual domains.

  15. Visible/near-infrared spectra of experimentally shocked plagioclase feldspars (United States)

    Johnson, Jeffrey R.; Hörz, Friedrich


    High shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales, the formation of diaplectic glass (maskelynite), and genuine melting. Past studies of visible/near-infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250-1300 nm and an overall decrease in reflectance. New visible/near-infrared spectra (400-2500 nm) of experimentally shocked (17-56 GPa) albite- and anorthite-rich rock powders demonstrate similar trends, including the loss of minor hydrated mineral bands near 1410, 1930, 2250, and 2350 nm. However, the most interesting new observations are increases in reflectance at intermediate pressures, followed by subsequent decreases in reflectance at higher pressures. The amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro-fractures, submicron grains, diaplectic glass, and melts formed during shock metamorphism. We interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass. The ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases. The pressure regimes over which these reflectance variations occur differ between albite and anorthite, consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars. These types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible/near-infrared remotely sensed spectra of planetary and asteroidal surfaces.

  16. Geochemical Processes in the Interaction Between a Marly Shale and a CO2-Rich Sulfate Solution Under Supercritical CO2 Conditions (United States)

    Davila, G.; Luquot, L.; Cama, J.; Soler Matamala, J. M.


    Geological CO2 sequestration at a pilot-plant scale is going to be performed at Hontomín (Spain). The Hontomín caprock is made up of marly shale, with an average composition (wt. %) of 71.2% calcite, 9.7% quartz, 7.1% illite, 6.5% albite, 2.8% clinochlore and trace amounts of gypsum, anhydrite and pyrite. The reservoir solution is rich in NaCl and sulfate (I = 0.6 M), being in equilibrium with respect to calcite and gypsum. The present study aims at evaluating the interaction between the shale and the CO2-rich solution of Hontomín under in situ conditions (pTotal = 150 bar, pCO2 = 61 bar and T = 60 °C). In particular, we focused on (i) the role of injected solution composition (S-free and S-rich solutions), (ii) the importance of mineral dissolution and precipitation processes and (iii) the effect of flow rate (0.2, 1 and 60 mL min-1) on the rock hydrodynamic properties. Under the experimental conditions, in both types of solution, dissolution of calcite, clinochlore and albite and precipitation of clays occurred, whereas precipitation of gypsum only took place in S-rich solution. In the S-free solution experiments, face and uniform dissolution was observed at low and high flow rate, respectively, but fracture permeability remained fairly constant independently of the flow rate. In the S-rich solution experiments, the fracture permeability decreased remarkably at the lower flow rates (kfinal/kinitial ≤ 0.03) due to precipitation of gypsum and clay minerals. However, at the highest flow rate, uniform dissolution occurred and the fracture permeability increased slightly (kfinal/kinitial = 4) as dissolution of calcite predominated over gypsum precipitation.

  17. Thermoluminescence response of the poly mineral fraction from hibiscus sabdariffa L foodstuffs

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Z, E.; Guzman, S. [UNAM, Instituto de Ciencias Nucleares, Apdo. Postal 70-543, 04510 Mexico D. F. (Mexico); Brown, F. [Universidad de Sonora, Departamento de Investigacion en Polimeros y Materiales, Apdo. Postal 130, 83000 Hermosillo, Sonora (Mexico); Chernov, V.; Barboza F, M., E-mail: ecruz@nucleares.unam.m [Universidad de Sonora, Departamento de Investigacion en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico)


    Food processed by ionizing irradiation is a safe technology and has been recognized by the FAO/Who Codes Alimentarius Commission. It is an excellent method to prevent food spoilage and food borne diseases by inhibiting the growth of microorganisms and slowing down ripening. The widespread use of food irradiation treatments that include spices, dry vegetables, grains and fruits make relevant the developing of methods for identification and analyses of foodstuffs processed by irradiation. The present work focuses on the thermoluminescence property of Mexican Roselle flower previously irradiated for detection purposes. The poly mineral content of irradiated commercial Roselle flower (Hibiscus sabdariffa L.) was extracted and analyzed by thermoluminescence (Tl). The X-ray diffraction analyses showed that quartz and albite composition for the poly mineral fraction. Different grain sizes; 10, 53, 74 and 149 {mu}m, were selected for the Tl analyses. The Tl glow curves depended on the grain sizes. The glow curves depicted two peaks around 92 and 120 C. The first peak was ascribed to quartz and the broad part of the glow curves (120-250 C) seems to correspond to the albite. Because the complex structure of the Tl glow curves from poly minerals the kinetic parameters were calculated by a fitting process using a deconvolution method based on a non-linear least-squares Levenberg-Ma quart. The values of the activation energy were found to be at 0.79-1.05 eV and 0.79-1.04 for 53 {mu}m and 250 {mu}m, respectively. The Tl properties of the samples were determined including dose response, reproducibly, fading and UV light bleaching. (Author)

  18. Thermoluminescence response of the poly mineral fraction from hibiscus sabdariffa L foodstuffs

    International Nuclear Information System (INIS)

    Food processed by ionizing irradiation is a safe technology and has been recognized by the FAO/Who Codes Alimentarius Commission. It is an excellent method to prevent food spoilage and food borne diseases by inhibiting the growth of microorganisms and slowing down ripening. The widespread use of food irradiation treatments that include spices, dry vegetables, grains and fruits make relevant the developing of methods for identification and analyses of foodstuffs processed by irradiation. The present work focuses on the thermoluminescence property of Mexican Roselle flower previously irradiated for detection purposes. The poly mineral content of irradiated commercial Roselle flower (Hibiscus sabdariffa L.) was extracted and analyzed by thermoluminescence (Tl). The X-ray diffraction analyses showed that quartz and albite composition for the poly mineral fraction. Different grain sizes; 10, 53, 74 and 149 μm, were selected for the Tl analyses. The Tl glow curves depended on the grain sizes. The glow curves depicted two peaks around 92 and 120 C. The first peak was ascribed to quartz and the broad part of the glow curves (120-250 C) seems to correspond to the albite. Because the complex structure of the Tl glow curves from poly minerals the kinetic parameters were calculated by a fitting process using a deconvolution method based on a non-linear least-squares Levenberg-Ma quart. The values of the activation energy were found to be at 0.79-1.05 eV and 0.79-1.04 for 53 μm and 250 μm, respectively. The Tl properties of the samples were determined including dose response, reproducibly, fading and UV light bleaching. (Author)

  19. The compositions of minerals within high pressure tectonic blocks from Horse Mountain, Northern California

    Energy Technology Data Exchange (ETDEWEB)

    Gilliam, C.E. (Mount Holyoke College, South Hadley, MA (United States). Geology Dept.)


    High pressure metamorphic blocks occur within serpentinite between the South Fork Mountain Schist and the Coast Range Fault, Humboldt Co., Northern California. Samples from three of these blocks were studied by petrographic techniques and quantitatively analyzed using the energy dispersive spectrometer on out scanning electron microscope. The mineral assemblages for three samples are as follows: WC86-7-3 contains omphacite (jd53, di36, hd11), pumpellyite, and relic igneous clinopyroxene. WC86-9-3 contains titanite, epidote chlorite, pumpellyite, and relic clinopyroxene. WC86-18-3 contains garnet, lawsonite, glaucophane, albite, chlorite, pumpellyite, minor quartz, and relic clinopyroxene. All samples contain relic clinopyroxene that, in the case of SC86-7-3, acts as a nucleus for omphacite growth. When present in cross cutting veins, omphacite has both radiating fibrous and blocky textures. Some epidote, titanite, clinopyroxene and pumpellyite were too fine to identify optically as well, but occur in the ground mass. Large grains of euhedral glaucophane, (Na[sub 2.0] Ca[sub .2])(Mg[sub 1.3] Fe[sub 2.0] Al[sub 1.7])Si[sub 8.0] O[sub 22] (OH)[sub 2], and garnet, (alm 33, pyO, sp30, gr37), containing relic ( ) clinopyroxene, glaucophane, and albite inclusions, were present in WC86-18-3. The high SiO[sub 2] and low TiO[sub 2] relative to Al[sub 2]O[sub 3] in relic clinopyroxene indicates a non-alkaline tholeiitic protolith. Omphacite compositions correspond to the type IV blueschist typical of the Franciscan Complex and constrain the pressures of metamorphism to be approximately 9 kb while lawsonite in WC86-18-3 implies a temperature below 450C. These observations indicate that the blocks are derived from subducted material that underwent metamorphism in a low temperature, high pressure setting. The process of their exhumation remains a mystery.

  20. The role of diffusion-controlled oscillatory nucleation in the formation of line rock in pegmatite-aplite dikes (United States)

    Webber, K.L.; Falster, A.U.; Simmons, W.B.; Foord, E.E.


    The George Ashley Block (GAB), located in the Pala Pegmatite District, San Diego County, California, is a composite pegmatite-aplite dike of 8 m thickness displaying striking mineralogical layering in the aphte portion of the dike, referred to as line rock. Rhythmic layering is characterized by garnet-rich bands alternating with albite-quartz-muscovite-rich bands. Cumulus textures are notably absent from the layered portion of the dike. Elongated quartz, megacrysts are oriented perpendicular to the garnet-rich layers and poikilitically include garnet, albite, and muscovite. Calculated crystal-free magma viscosity with 3% H2O is 106.2 Pa s and the calculated settling velocity for garnet is 0??51 cm/year. Conductive cooling calculations based on emplacement of a 650??C dike into 150?? C fractured gabbroic country rock at 1??5 kbar, and accounting for latent heat of crystallization, demonstrate that the line rock portion of the dike cools to 550?? C in about 1 year. Crystal size distribution studies also suggest very rapid nucleation and crystallization. Diffusion-controlled gel crystallization experiments yield textures virtually identical to those observed in the layered aplite, including rhythmic banding, colloform layering, and band discontinuities. Thus, observed textures and calculated magmatic parameters suggest that mineralogical layering in the GAB results from an in situ diffusion-controlled process of oscillatory nucleation and crystallization. We propose that any event that promotes strong undercooling has the potential to initiate rapid heterogeneous nucleation and oscillatory crystal growth, leading to the development of a layer of excluded components in front of the crystallization front, and the formation of line rock.

  1. Rubidium-rich feldspars and associated minerals from the Luolamäki pegmatite, Somero, Finland

    Directory of Open Access Journals (Sweden)

    Teerstra, D.K.


    Full Text Available Rubidium feldspar occurs near the core zone of the highly fractionated petalite-subtype Luolamäki granitic pegmatite in intimate intergrowth with other feldspars which are part of a characteristic sequence of alteration of pollucite. Pods of pollucite are cut by 5-20 cm-wide veins of albite, petalite, non-perthitic microcline, lepidolite and quartz, by thinner veins of fine-grained micas and spodumene, and are replaced by metasomatic adularia. Grains of rubidium feldspar occur as a potentially ordered phase in the vein microcline in association with earlier-exsolved albite, and also as late thin (< 5 μm veinlets. Rubidium feldspar also occurs as a potentially disordered phase which crystallized along with metasomatic adularia. Both generations of (Rb,K-feldspar have a similar compositional range, close to the join KAlSi3O8-RbAlSi3O8, typically with up to ~21 wt.% Rb2O (~70 mol.% Rbf and with minor Cs, but neglible Na, Ca, Fe or P. Extreme compositions have 26.0 wt.% Rb2O (89.0 mol.% Rbf and 1.26 wt.% Cs2O (2.8 mol.% Csf. The diffuse compositional gradients from microcline to rubicline are consistent with a solid-state exsolution origin, followed by fluid-assisted textural coarsening which generates distinct phase boundaries. In contrast, metasomatic adularian (Rb,K-feldspar was precipitated at low temperature (250-150°C and fine-scale zoning with variable K/Rb is preserved as a growth feature.

  2. Three-Dimensional Modeling of the Reactive Transport of CO2 and Its Impact on Geomechanical Properties of Reservoir Rocks and Seals

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Ba Nghiep; Hou, Zhangshuan; Bacon, Diana H.; Murray, Christopher J.; White, Mark D.


    This article develops a novel multiscale modeling approach to analyze CO2 reservoirs using Pacific Northwest National Laboratory’s STOMP-CO2-R code that is interfaced with the ABAQUS® finite element package. The STOMP-CO2-R/ABAQUS® sequentially coupled simulator accounts for the reactive transport of CO2 causing mineral composition changes that modify the geomechanical properties of reservoir rocks and seals. Formation rocks’ elastic properties that vary during CO2 injection and govern the poroelastic behavior of rocks are modeled by an Eshelby-Mori-Tanka approach (EMTA) implemented in ABAQUS® via user-subroutines. The computational tool incorporates the change in rock permeability due to both geochemistry and geomechanics. A three-dimensional (3D) STOMP-CO2-R model for a model CO2 reservoir containing a vertical fault is built to analyze a formation containing a realistic geochemical reaction network with 5 minerals: albite, anorthite, calcite, kaolinite and quartz. A 3D ABAQUS® model that maps the above STOMP-CO2-R model is built for the analysis using STOMP-CO2-R/ABAQUS®. The results show that the changes in volume fraction of minerals include dissolution of anorthite, precipitation of calcite and kaolinite, with little change in the albite volume fraction. After a long period of CO2 injection the mineralogical and geomechanical changes significantly reduced the permeability and elastic modulus of the reservoir (between the base and caprock) in front of the fault leading to a reduction of the pressure margin to fracture at and beyond the injection location. The impact of reactive transport of CO2 on the geomechanical properties of reservoir rocks and seals are studied in terms of mineral composition changes that directly affect the rock stiffness, stress and strain distributions as well as the pressure margin to fracture.

  3. Radionuclide sorption in Yucca Mountain tuffs with J-13 well water: Neptunium, uranium, and plutonium. Yucca Mountain site characterization program milestone 3338

    International Nuclear Information System (INIS)

    We studied the retardation of actinides (neptunium, uranium, and plutonium) by sorption as a function of radionuclide concentration in water from Well J-13 and of tuffs from Yucca Mountain. Three major tuff types were examined: devitrified, vitric, and zeolitic. To identify the sorbing minerals in the tuffs, we conducted batch sorption experiments with pure mineral separates. These experiments were performed with water from Well J-13 (a sodium bicarbonate groundwater) under oxidizing conditions in the pH range from 7 to 8.5. The results indicate that all actinides studied sorb strongly to synthetic hematite and also that Np(V) and U(VI) do not sorb appreciably to devitrified or vitric tuffs, albite, or quartz. The sorption of neptunium onto clinoptilolite-rich tuffs and pure clinoptilolite can be fitted with a sorption distribution coefficient in the concentration range from 1 X 10-7 to 3 X 10-5 M. The sorption of uranium onto clinoptilolite-rich tuffs and pure clinoptilolite is not linear in the concentration range from 8 X 10-8 to 1 X 10-4 M, and it can be fitted with nonlinear isotherm models (such as the Langmuir or the Freundlich Isotherms). The sorption of neptunium and uranium onto clinoptilolite in J-13 well water increases with decreasing pH in the range from 7 to 8.5. The sorption of plutonium (initially in the Pu(V) oxidation state) onto tuffs and pure mineral separates in J-13 well water at pH 7 is significant. Plutonium sorption decreases as a function of tuff type in the order: zeolitic > vitric > devitrified; and as a function of mineralogy in the order: hematite > clinoptilolite > albite > quartz

  4. Porphyry Cu-Au and associated polymetallic Fe-Cu-Au deposits in the Beiya Area, western Yunnan Province, south China (United States)

    Xu, X.-W.; Cai, X.-P.; Xiao, Q.-B.; Peters, S.G.


    The Alkaline porphyries in the Beiya area are located east of the Jinshajiang suture, as part of a Cenozoic alkali-rich porphyry belt in western Yunnan. The main rock types include quartz-albite porphyry, quartz-K-feldspar porphyry and biotite-K-feldspar porphyry. These porphyries are characterised by high alkalinity [(K2O + Na2O)% > 10%], high silica (SiO2% > 65%), high Sr (> 400??ppm) and 87Sr/86Sr (> 0.706)] ratio and were intruded at 65.5??Ma, between 25.5 to 32.5??Ma, and about 3.8??Ma, respectively. There are five main types of mineral deposits in the Beiya area: (1) porphyry Cu-Au deposits, (2) magmatic Fe-Au deposits, (3) sedimentary polymetallic deposits, (4) polymetallic skarn deposits, and (5) palaeoplacers associated with karsts. The porphyry Cu-Au and polymetallic skarn deposits are associated with quartz-albite porphyry bodies. The Fe-Au and polymetallic sedimentary deposits are part of an ore-forming system that produced considerable Au in the Beiya area, and are characterised by low concentrations of La, Ti, and Co, and high concentrations of Y, Yb, and Sc. The Cenozoic porphyries in western Yunnan display increased alkalinity away from the Triassic Jinshajiang suture. Distribution of both the porphyries and sedimentary deposits in the Beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the Yangtze Plate and Gondwana continent, and lie within a shear zone between buried Palaeo-Tethyan oceanic lithosphere and upper mantle lithosphere, caused by the subduction and collision of India and Asia. ?? 2006 Elsevier B.V. All rights reserved.

  5. Supra-subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics (United States)

    Kim, J.; Coish, R.; Evans, M.; Dick, G.


    Metadiabasic intrusions of the Mount Norris Intrusive Suite occur in fault-bounded lithotectonic packages containing Stowe, Moretown, and Cram Hill Formation lithologies in the northern Vermont Rowe-Hawley belt, a proposed Ordovician arc-trench gap above an east-dipping subduction zone. Rocks of the Mount Norris Intrusive Suite are characteristically massive and weakly foliated, have chilled margins, contain xenoliths, and have sharp contacts that both crosscut and are parallel to early structural fabrics in the host metasedimentary rocks. Although the mineral assemblage of the Mount Norris Intrusive Suite is albite + actinolite + epidote + chlorite + calcite + quartz, intergrowths of albite + actinolite are probably pseudomorphs after plagioclase + clinopyroxene. The metadiabases are subalkaline, tholeiitic, hypabyssal basalts with preserved ophitic texture. A backarc-basin tectonic setting for the intrusive suite is suggested by its LREE (light rare earth element) enrichment, negative Nb-Ta anomalies, and Ta/Yb vs. Th/Yb trends. Although no direct isotopic age data are available, the intrusions are broadly Ordovician because their contacts are clearly folded by the earliest Acadian (Silurian-Devonian) folds. Field evidence and geochemical data suggest compelling along-strike correlations with the Coburn Hill Volcanics of northern Vermont and the Bolton Igneous Group of southern Quebec. Isotopic and stratigraphic age constraints for the Bolton Igneous Group bracket these backarc magmas to the 477-458 Ma interval. A tectonic model that begins with east-dipping subduction and progresses to outboard west-dipping subduction after a syncollisional polarity reversal best explains the intrusion of deformed metamorphosed metasedimentary rocks by backarc magmas.

  6. The Lagoa Real subalkaline granitic complex (south Bahia, Brazil): a source for uranium mineralizations associated with Na-Ca metasomatism

    International Nuclear Information System (INIS)

    In the central zone of the Sao Francisco Craton (South Bahia), the lower Proterozoic Lagoa Real granites and orthogneisses overthrust to the West the younger Urandi and Espinhaco metamorphic series, probably a late Brazilian event. This thrust is related to the regional metamorphism (amphibolite facies) of the Lagoa Real granites and induces a reverse HP metamorphism in the over thrusted series. Undeformed granites (sao Timoeto type) present two feldspars, perthitic orthoclase largely predominant over plagioclase (oligoclase ≥ albite), blue quartz, Fe-rich amphibole and biotite ± clinopyroxene assemblages, ilmenite ≥ magnetite, zircon, apatite, allanite and Nb ± Ti-REE oxides and silicates. The crystallization of the granites begins at high temperature and under low fO2 and PH2O conditions. Fractional crystallization of pyroxene and plagioclase leads to silica enrichment during magmatic differentiation. Increasing fO2 and PH2O are observed during this evolution. Orthogneisses show strongly recrystallized paragenesis: equal abundance of non-perthitic microcline and plagioclase (oligoclase ≤ albite), quartz, more Al-rich amphibole and biotite, magnetite, sphene, zircon, allanite, Nb ± Ti-REE oxides and silicates, and ± apatite. HT Na and Ca metasomatism occurs 330 Ma later than granite emplacement and is synchronous with important uranium mineralizations. Major elements and trace-elements geochemistry of the granites and orthogneisses indicate subalkaline to alkaline typology. Incompatible behaviour of Th, REE, Y, Zr, Nb, and F points out a convergence with alkaline magmatism. CI, F, Th, Y, REE, NB enrichments and Ba, Sr depletions are also related to a late magmatic stage. U-Th-rich and metamict accessory minerals of the granites represent a favorabl source for the Lagoa Real uranium ore-deposits

  7. Further description of the petrology of the Topopah Spring member of the paintbrush tuff in drill holes UE25A-1 and USW-G1 and of the lithic-rich tuff in USW-G1, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    The Topopah Spring Member of the Paintbrush Tuff and the Lithic-rich tuff and two Tertiary volcanic units that occur in cores from drill holes UE25a-1 and USW-G1 at Yucca Mountain, Nevada. Recently they have been suggested as possibly suitable for the permanent storage of high-level radioactive waste. Earlier petrologic characterization of these units is augmented here. The Topopah Spring Member (approximately 350 m thick) has two compound cooling units. The upper, thinner unit is densely welded to vitrophyric. The lower unit ranges from nonwelded to vitrophyric, and its nonwelded base is extensively zeolitized to clinoptilolite and mordenite. Heulandite occurs as fracture fill in the overlying vitrophyric part, but zeolites are absent above that vitrophyre. Here primary devitrification plus vapor-phase crystallization dominate the mineralogy. Vapor-phase effects are especially prominent between the two vitrophyres in both cores and include numerous large lithophysal cavities throughout most of this moderately to densely welded tuff. The Lithic-rich tuff extends from 1203 to 1506 m in the USW-G1 drill core. It is nonwelded to partly welded but is well indurated due to pervasive intergrowths of authigenic minerals. These phases are analcime, albite, alkali feldspar, sericite, chlorite and quartz. The transition from analcime to secondary albite corresponds to Iijima's zeolite Zone IV boundary, and this boundary appears in USW-G1 at 1326 m. However, analcime remains as a prominent phase through most of the Lithic-rich tuff. Further work is necessary to assess the suitability of either of these horizons for a waste repository. In the Topopah Spring Member, both mechanical and hydrologic properties of thick lithophysal zone must be studied, as well as the complete sequence of fracture fill. For both units, zeolite and clay mineral stabilities need to be investigated

  8. Rare earth element and yttrium geochemistry applied to the genetic study of cryolite ore at the Pitinga Mine (Amazon, Brazil

    Directory of Open Access Journals (Sweden)

    Orlando R.R. Minuzzi


    Full Text Available This work aims at the geochemical study of Pitinga cryolite mineralization through REE and Y analyses in disseminated and massive cryolite ore deposits, as well as in fluorite occurrences. REE signatures in fluorite and cryolite are similar to those in the Madeira albite granite. The highest ΣREE values are found in magmatic cryolite (677 to 1345 ppm; ΣREE is lower in massive cryolite. Average values for the different cryolite types are 10.3 ppm, 6.66 ppm and 8.38 ppm (for nucleated, caramel and white types, respectively. Disseminated fluorite displays higher ΣREE values (1708 and 1526ppm than fluorite in late veins(34.81ppm. Yttrium concentration is higher in disseminated fluorite and in magmatic cryolite. The evolution of several parameters (REEtotal, LREE/HREE, Y was followed throughout successive stages of evolution in albite granites and associated mineralization. At the end of the process, late cryolite was formed with low REEtotal content. REE data indicate that the MCD was formed by, and the disseminated ore enriched by (additional formation of hydrothermal disseminated cryolite, hydrothermal fluids, residual from albite granite. The presence of tetrads is poorly defined, although nucleated, caramel and white cryolite types show evidence for tetrad effect.Este trabalho enfoca a geoquímica de elementos terras raras (ETR e de Y no minério criolítico disseminado, no depósito criolítico maciço e na fluorita associada na mina Pitinga. As assinaturas de ETR na criolita e fluorita são similares àquelas do granito Madeira. Os maiores valores de SETR são encontrados na criolita magmática disseminada (677 a 1.345 ppm; SETR é menor na criolita maciça, com valores médios de 10,3 ppm, 6,66 ppm e 8,38 ppm, respectivamente, nos tipos de criolita nucleada, caramelo e branca. A fluorita magmática disseminada apresenta os valores mais altos de SETR (1.708 e 1.526 ppm, contrastando com a fluorita de veio tardio(34,81 ppm. A concentra

  9. The blueschits from the Kopina Mt., West Sudetes, Poland - what do they tell us about accretion of the Variscides? (United States)

    Majka, Jarosław; Mazur, Stanisław; Kośmińska, Karolina; Dudek, Krzysztof


    Blueschists are tracers of sutures, thus marking fossil subduction zones at convergent plate boundaries and providing important constraints on plate tectonic reconstructions. Their occurrences are scarce in the Variscan belt owing to a strong collisional overprint but just because of that each locality deserves particular attention. The Variscan blueschists must have formed during the early stage of the Variscan Orogeny and may represent a vestige of missing marginal basins fringing the Rheic Ocean at the onset of subduction. The studied rocks from the Kopina Mt. consist mainly of garnet, glaucophane, clinozoisite-epidote, chlorite-I, titanite, hematite and quartz. The original high-pressure assemblage is overprinted by later, lower pressure paragenesis, which comprises mostly Ca-amphiboles, chlorite-II, albite and K-feldspar. The latter occurs in polymineral inclusions in other phases together with albite and chlorite that are interpreted as phengite breakdown products. Garnet shows chemical compositional variation from Alm54Prp3Grs30Sps13 in the cores to Alm66Prp4Grs29Sps1 in the rims. The almandine zoning is bowl-shaped, whereas spessartine profiles show bell-shaped trends. The grossular and pyrope contents are generally constant throughout the grain. Rather gradual changes in the chemical zoning suggest a progressive, one-step garnet growth pattern. Glaucophane, although commonly well preserved, in some cases disintegrates to the albite-chlorite assemblage. The pressure-temperature (P-T) conditions were estimated using the phase equilibrium modelling in the NCKFMMnASHTO system using the PerpleX software. The compositional isopleths cross cut in the stability field of Grt+Gln+Ep+Chl+Pheng+Ttn+Hem+Q. P-T estimates indicate that the peak conditions occur at c. 14-17 kbar and 470-500°C, which corresponds to quite a low geothermal gradient in the range of 8-10°C/km. The P-T conditions estimated lie on a low temperature geotherm that is typical for a relatively

  10. Archean high-Mg monzodiorite-syenite, epidote skarn, and biotite-sericite gold lodes in the Granny Smith-Wallaby district, Australia: U-Pb and Re-Os chronometry of two intrusion-related hydrothermal systems (United States)

    Mueller, Andreas G.; Hall, Gregory C.; Nemchin, Alexander A.; Stein, Holly J.; Creaser, Robert A.; Mason, Douglas R.


    The Granny Smith (37 t Au production) and Wallaby deposits (38 t out of a 180 t Au resource) are located northeast of Kalgoorlie, in 2.7 Ga greenstones of the Eastern Goldfields Province, the youngest orogenic belt of the Yilgarn craton, Western Australia. At Granny Smith, a zoned monzodiorite-granodiorite stock, dated by a concordant titanite-zircon U-Pb age of 2,665 ± 3 Ma, cuts across east-dipping thrust faults. The stock is fractured but not displaced and sets a minimum age for large-scale (1 km) thrust faulting (D2), regional folding (D1), and dynamothermal metamorphism in the mining district. The local gold-pyrite mineralization, controlled by fractured fault zones, is younger than 2,665 ± 3 Ma. In augite-hornblende monzodiorite, alteration progressed from a hematite-stained alkali feldspar-quartz-calcite assemblage and quartz-molybdenite-pyrite veins to a late reduced sericite-dolomite-albite assemblage. Gold-related monazite and xenotime define a U-Pb age of 2,660 ± 5 Ma, and molybdenite from veins a Re-Os isochron age of 2,661 ± 6 Ma, indicating that mineralization took place shortly after the emplacement of the main stock, perhaps coincident with the intrusion of late alkali granite dikes. At Wallaby, a NE-trending swarm of porphyry dikes comprising augite monzonite, monzodiorite, and minor kersantite intrudes folded and thrust-faulted molasse. The conglomerate and the dikes are overprinted by barren (1,600-m-long replacement pipe, which is intruded by a younger ring dike of syenite porphyry pervasively altered to muscovite + calcite + pyrite. Skarn and syenite are cut by pink biotite-calcite veins, containing magnetite + pyrite and subeconomic gold-silver mineralization (Au/Ag = 0.2). The veins are associated with red biotite-sericite-calcite-albite alteration in adjacent monzonite dikes. Structural relations and the concordant titanite U-Pb age of the skarn constrain intrusion-related mineralization to 2,662 ± 3 Ma. The main-stage gold-pyrite ore

  11. Experimental Studies on the Interaction of scCO2 and scCO2-SO2 With Rock Forming Minerals at Conditions of Geologic Carbon Storages - First Results (United States)

    Erzinger, J.; Wilke, F.; Wiersberg, T.; Vasquez Parra, M.


    Co-injection of SO2 (plus possibly NOx and O2) during CO2 storage in deep saline aquifers may cause stronger brine acidification than CO2 alone. Because of that, we investigate chemical corrosion of rocks and rock-forming minerals with impure supercritical CO2 (scCO2) at possible storage conditions of >73.7 bar and >31°C. Contaminates were chosen with respect to the composition of CO2 captured industrially from coal-fired power plants using the oxyfuel technology. The resulting data should build a base for the long-term prediction of the behavior of CO2 in geologic storage reservoirs. Experiments of up to 1000 hrs duration have been performed with 10 natural mineral concentrates (calcite, dolomite, siderite, anhydrite, hematite, albite, microcline, kaolinite, muscovite, biotite) in 3n NaCl solution and pure scCO2 or scCO2+SO2 (99.5+0.5 vol%). The NaCl reaction fluid resembles the average salinity of deep formation waters of the North German Basin and is not free of oxygen. To increase reaction rates all minerals were ground and the reagents agitated either by stirring or shaking in autoclaves of about one liter in volume. The autoclaves consist of Hastelloy™ or ferromagnetic stainless steel fully coated with PTFE. We used in average 15 g of solids, 700 ml liquid, and the vessels were pressurized up to 100 bars with CO2 or CO2-SO2 mixture. Experiments were run at temperatures up to 90°C. Before, during and after the experiments small amounts fluids were sampled and analyzed for dissolved constituents and pH. Solid phases were characterized by XRF, XRD, and EMPA before and after the experiments. Pure scCO2 corrodes all carbonates, reacts only slightly with anhydrite, albite, and microcline at a minimum pH of 4, and does not recognizably interact with the others. After the experiment, albite has gained in a, not yet fully identified, carbonate phase which might be dawsonite. Reaction fluids of the experiments with scCO2+SO2 have mostly lower pH than using scCO2

  12. Mineralogy of silicate inclusions of the Colomera IIE iron and crystallization of Cr-diopside and alkali feldspar from a partial melt (United States)

    Takeda, Hiroshi; Hsu, Weibiao; Huss, Gary R.


    We studied the mineralogy, mineral chemistry, and compositions of 48 interior silicate inclusions and a large K-rich surface inclusion from the Colomera IIE iron meteorite. Common minerals in the interior silicate inclusions are Cr diopside and Na plagioclase (albite). They are often enclosed by or coexist with albitic glasses with excess silica and minor Fe-Mg components. This mineral assemblage is similar to the "andesitic" material found in the Caddo County IAB iron meteorite for which a partial melt origin has been proposed. The fairly uniform compositions of Cr diopside (Ca 44Mg 46Fe 10) and Na plagioclase (Or 2.5Ab 90.0An 7.5 to Or 3.5Ab 96.1An 0.4) in Colomera interior inclusions and the angular boundaries between minerals and metal suggest that diopside and plagioclase partially crystallized under near-equilibrium conditions from a common melt before emplacement into molten metal. The melt-crystal assemblage has been called "crystal mush." The bulk compositions of the individual composite inclusions form an array between the most diopside-rich inclusion and plagioclase. This is consistent only with a simple mechanical mixing relationship, not a magmatic evolution series. We propose a model in which partly molten metal and crystal mush were mixed together by impact on the IIE parent body. Other models involving impact melting of the chondritic source material followed by growth of diopside and plagioclase do not easily explain near equilibrium growth of diopside and Na plagioclase, followed by rapid cooling. In the K-rich surface inclusion, K feldspar, orthopyroxene, and olivine were found together with diopside for the first time. K feldspar (sanidine, Or 92.7Ab 7.2An 0.1 to Or 87.3Ab 11.0An 1.7) occurs in an irregular veinlike region in contact with large orthopyroxene crystals of nearly uniform composition (Ca 1.3Mg 80.5Fe 17.8 to Ca 3.1Mg 78.1Fe 18.9) and intruding into a relict olivine with deformed-oval shape. Silica and subrounded Cr diopside are

  13. Origin of solutes in surface waters from high Alpine catchments, Zermatt area (Swiss Alps) (United States)

    Zhou, Wei; Bucher, Kurt


    summarized as: 1) Meteoric water + CO2 + O2 + pyrite + epidote + chlorite + albite + phengite + "halite" = "quartz" + goethite + kaolinite + Ca-HCO3 water and 2) Meteoric water + CO2 + O2 + calcite + pyrite + albite + phengite + chlorite ± "halite" = ±"quartz" + goethite + kaolinite + Ca-HCO3 water. Magnesium-rich Mg-HCO3 water is produced from reaction of precipitation with serpentinite: 3) Meteoric water + CO2 + O2 + antigorite + diopside + phengite + pyrite = magnesite + talc + goethite + Mg-HCO3 water. Sulphate-rich Ca-SO4 water occur mainly in gneiss and granite catchments, where the precipitation interacted with pyrite-baring rocks according to the reaction: 4) Initial water ± CO2 + O2 + pyrite + plagioclase + K-feldspar + chlorite ± halite = goethite + kaolinite + albite ± quartz + Ca-SO4 water.

  14. Petrology and textural evolution of granites associated with tin and rare-metals mineralization at the Pitinga mine, Amazonas, Brazil (United States)

    Lenharo, Sara Lais Rahal; Pollard, Peter J.; Born, Helmut


    The Água Boa and Madeira igneous complexes at the Pitinga mine were emplaced into acid volcanic rocks of the Paleoproterozoic Iricoumé Group, and host major tin, rare-metal (Zr, Nb, Ta, Y, REE) and cryolite mineralization. The igneous complexes are elongate NE-SW and each is composed of three major facies that, in order of emplacement, include porphyritic and equigranular rapakivi granite and biotite granite in both igneous complexes, followed by topaz granite in the Água Boa igneous complex (ABIC) and albite granite in the Madeira igneous complex (MIC). Rapakivi, porphyritic and granophyric textures observed in the granites are interpreted to reflect multiple stages of crystallization at different pressures (depths). Decompression during ascent shifted the magmas into the plagioclase stability field, causing partial resorption of quartz, with subsequent growth at lower pressure. Fluid saturation and separation probably occurred after final emplacement at shallow levels. Temperature and pressure estimates based on phase relations and zircon concentrations range from a maximum of 930 °C and 5 kbar for the rapakivi granites to below 650 °C and 1 kbar for the peralkaline albite granite. This suggests initial crystallization of early intrusive phases at around 15 km depth, with final emplacement of more volatile-rich crystal-mush at a depth of 0.5-1 km. Accessory minerals, including zircon, thorite, monazite, columbite-tantalite, cassiterite, bastnaesite and xenotime are present in almost all facies of the Água Boa and Madeira igneous complexes, attesting to the highly evolved character of the magmas. The presence of magnetite and/or primary cassiterite indicate crystallization under oxidizing conditions above the NNO buffer. The evolutionary sequence and Nd isotope characteristics ( TDM=2.2-2.4 Ga) of the Pitinga granites are similar to those of other Proterozoic rapakivi granites. However, petrographic, geochemical and Nd isotopic data ( ɛNd initial=-2.1 to +0

  15. REE, Y, Nb, U, and Th contents and tetrad effect in zircon from a magmatic-hydrothermal F-rich system of Sn-rare metal-cryolite mineralized granites from the Pitinga Mine, Amazonia, Brazil (United States)

    Nardi, Lauro V. S.; Formoso, Milton L. L.; Jarvis, Kym; Oliveira, Leondres; Bastos Neto, Artur C.; Fontana, Eduardo


    The geochemistry of zircon from the granites that host the Sn-Rare-Metal-cryolite deposit of Pitinga Mine in northern Brazil, Amazonia, is discussed based on data obtained by LA-ICP-MS. The ore deposit is one of the largest in the world and is related with F-rich A-type granite intrusions of 1822 ± 2 Ma. REE, Y, U, Th, Nb, Ta, Pb, and Hf contents were determined in zircon grains from the albite-bearing facies that contains the ore deposit and from less evolved facies composed of amphibole-biotite and biotite granites. The trace-element contents of zircon were compared to those of their host rocks and the calculated zircon/rock ratios are like the values of zircon/melt partition coefficients for natural granitic compositions. The concentrations found for all analysed elements are highly variable, even for determinations made in the same grain. However, the average contents and patterns are like those of typical magmatic zircon and can indicate the composition of the melts from which they were crystallized. The interpretation of trace element contents in the zircon grains suggests that: (i) in the albite-bearing facies, zircon crystallized after the volatile phase exsolution and shows typical geochemical features such as: Th/U ratios from 1 to 10, Y/Ho is lower than 20, Sm/Nd ratios are generally higher than 0.5, Nb/Y is higher than 0.08, and Hf is over 2 wt%; (ii) M-type tetrad effects were produced in the REE patterns of most differentiated melts by F-complex stabilization, and were preserved in some zircon grains; (iii) ore deposition in the Pitinga mine initiated in the late stages of magmatic crystallization mainly following resurgent boiling. The trace element contents of zircon are particularly relevant for provenance studies if mineral/melt partition coefficients are taken into account, so that the approximate trace element pattern of their igneous source can be estimated. The geochemistry of trace elements in zircon, in spite of the wide range of contents

  16. Infiltration of dilute groundwaters and resulting groundwater compositions at repository depth

    International Nuclear Information System (INIS)

    The purpose of this study has been to simulate the hydrochemical evolution of dilute water, typical of melt-water in a glaciation scenario, infiltrating into bedrock. The focus is on the alkali and alkaline earth cation compositions because these might affect the performance of bentonite buffer. A geochemical model of batch reactions between dilute water and rock minerals has been constructed. Two approaches to simulating these hydrogeochemical reactions have been implemented using the PHREEQC program. The first approach has simulated the dissolution reactions of various aluminosilicate minerals in terms of the rates of each reaction. The potential for continued dissolution is governed by the calculated state of thermodynamic equilibrium for each mineral phase, but the progress of dissolution is calculated using empirical kinetics expressions. The second approach has assumed that local equilibria are achieved rapidly between water and reactive minerals so that hydrochemical evolution is governed by equilibria with different assemblages of minerals. Sequential equilibria with various permutations of mineral assemblages have simulated how the resulting groundwater compositions, specifically the pH and the [Ca2++Mg2+]/[Na+] ratio, depend on the selected mineral assemblages. The equilibrating secondary minerals for both modelling approaches are calcite, chalcedony, kaolinite, illite and chlorite, plus montmorillonite in the local equilibrium model. The minerals selected for kinetic dissolution reactions are albite, anorthite, K-feldspar and biotite. The minerals selected for dissolution-only equilibration are laumontite, saponite, prehnite, albite, anorthite and K-feldspar. Model runs were constructed to represent various combinations of these minerals in three stages of local equilibrium. The main conclusions to be drawn from this modelling study are: (i) The realistic and most likely scenarios for hydrogeochemical evolution would result in divalent cation

  17. Stable isotope systematics and fluid inclusion studies in the Cu-Au Visconde deposit, Carajás Mineral Province, Brazil: implications for fluid source generation (United States)

    da Costa Silva, Antonia Railine; Villas, Raimundo Netuno Nobre; Lafon, Jean-Michel; Craveiro, Gustavo Souza; Ferreira, Valderez Pinto


    The Cu-Au Visconde deposit is located in the Carajás Mineral Province (CMP), northern Brazil, near the contact between the ca. 2.76 Ga metavolcano-sedimentary rocks of the Itacaiunas Supergroup rocks and the ~3.0 Ga granitic-gneissic basement. It is hosted by mylonitized Archean rocks, mainly metadacites, the Serra Dourada granite, and gabbros/diorites, which have been successively altered by sodic, sodic-calcic-magnesian, potassic, and calcic-magnesian hydrothermal processes, producing diverse mineralogical associations (albite-scapolite; albite-actinolite-scapolite-epidote; K-feldspar-biotite; chlorite-actinolite-epidote-calcite, etc.). Chalcopyrite is the dominant ore mineral and occurs principally in breccias and veins/veinlets. The aqueous fluids responsible for the alteration/mineralization were initially hot (>460 °C) and very saline (up to 58 wt.% equivalent (equiv.) NaCl), but as the system evolved, they experienced successive dilution processes. Mineral oxygen and hydrogen isotope data show that 18O-rich ( to +9.4 ‰) fluids prevailed in the earlier alteration (including magnetitites) and reached temperatures as high as 410-355 °C. Metamorphic/formation waters, most likely derived from the Carajás Basin rocks, appear to have contributed a major component to the fluid composition, although some magmatic input cannot be discounted. In turn, the later alterations and the mineralization involved cooler (<230 °C), 18O-depleted ( to +3.7 ‰) and less saline (7-30 wt.% equiv. NaCl) fluids, indicating the influx of meteoric water. Fluid dilution and cooling might have caused abundant precipitation of sulfides, especially as breccia cement. Ore δ 34 S values (+0.5 to +3.4 ‰) suggest a magmatic source for sulfur (from sulfide dissolution in pre-existing igneous rocks). The chalcopyrite Pb-Pb ages (2.73 ± 0.15 and 2.74 ± 0.10 Ga) indicate that the Visconde mineralization is Neoarchean, rather than Paleoproterozoic as previously considered. If so, the

  18. Formation of parting in quartz (United States)

    Jørgen Kjøll, Hans; Eske Sørensen, Bjørn


    This paper presents hydrothermal quartz with macroscopic planar parting from the Mesoproterozoic Modum complex in southern Norway. Similar macroscopic parting in hydrothermal quartz with macroscopic planar structures has only been described from two localities in the world; Madagascar (Flörke et al., 1981) and Southern California (Murdoch et al., 1938). The study area consists of well foliated and banded sillimanite- garnet- amphibolite- mica gneiss that is cut at high angle by hydrothermal veins containing albite, chlinoclore, hornblende, hydroxyl apatite and quartz. The rim of the veins is generally made up of almost pure end-member euhedral albite. Then there is vugs with euhedral hornblende (10-25cm long) and euhedral hydroxyl apatite with size ranging from mm scale to several cm. Some places the quartz encloses apatite and hornblende. The quartz is anhedral, inequigranular with undulose extinction bordering sub grain rotation. It has large planar penetrative parting faces with pearly luster; however this is not consistent throughout the outcrop and some places the penetrative faces disappears and the quartz has a conchoidal fracture. The planar faces continue throughout the specimens with a few mm spacing. Thin sections oriented perpendicular to the most pronounced planar structure show lamellas that extinguishes at small angles (2 degrees) to each other. EBSD mapping of the planar faces shows two orientations {0-111} and {1-101}, corresponding to the r- and z-faces respectively, separated by irregular boundaries. The misorientation between these two crystallographic orientations on the parting is a 60 degree rotation on [0 0 1] in correspondence to the dauphiné twin law. Investigations conducted on thin sections cut orthogonal to the parting shows that the parting cuts and offsets the dauphiné twins, indicating a late genesis of the parting. However some internal stress induced movement of the twins are visible. SEM-CL documents three generations of quartz

  19. Brines in Crustal Processes: Important Roles Inferred From Experimental Studies (Invited) (United States)

    Newton, R. C.; Manning, C. E.


    Concentrated salt solutions are increasingly implicated as active agents in many fluid-mediated deep- and mid-crust processes, including rock-melting, charnockitic alteration, trace-element depletion and enrichment, regional metasomatism including dehydration and rehydration, albitization, deep-crustal oxidation, and formation of economic mineral deposits. Unique properties of saline aqueous fluids at high P and T, recently revealed by experimental work, provide new explanations for these metasomatic features and encourage further search for a brine connection in other outstanding problems of metamorphism. Specific properties of high P-T NaCl solutions favorable for deep-crustal metasomatism are high solubility for some rock-forming components, especially CaO and FeO, even at high salt concentration, very low H2O activity as a consequence of pressure-induced dissociation, allowing compatibility with anhydrous (granulite facies) mineral assemblages, and high ability to infiltrate mineral grain boundaries. The high affinity of alkali chloride brines for CaO can explain trace element mobility in high grade metamorphism, by virtue of the high solubility of apatite, and the puzzling phenomenon of subsolidus charnockitic alteration, as in South India, in which orthopyroxene is formed from the incongruent dissolution of calcic amphibole. The great pressure effect on lowering H2O activity in concentrated pore-fluid brines causes fluid-present melting points of crustal rocks to swerve sharply to higher temperatures with increasing depth, in contrast to the behavior in the presence of pure H2O. This fact could account for the formation of swarms of granite intrusions in shear-zone-related settings, such as the Caledonide granites of Scotland and northern Ireland. It is postulated that salty solutions of deep-seated origin inhibit melting as they rise through the lower crust, but induce large-scale melting at mid-crust levels because of increase of H2O activity by release of

  20. Thermoluminescent dependence with the particle size in ionized foods by radiation; Dependencia termoluminiscente con el tamano de particula en alimentos ionizados por radiacion

    Energy Technology Data Exchange (ETDEWEB)

    Teuffer Z, C.A


    The influence of the particle size of poly minerals in the signals of the thermally stimulated luminescence (TL) is analysed. The poly minerals were extracted of Mexican spices such as Origanum vulgare L. (origanum) and Capsicum annum (Chilli guajillo), these underwent to an homogenization process to obtain four different particle sizes corresponding to 149, 74, 53 and 10 {mu} m, and later on to expose them to gamma radiation in an interval of 0.5- 45 kGy in the Gamma beam 651 PT of {sup 60} Co irradiator of the Nuclear Sciences Institute, UNAM. The glow curves show a maximum of TL intensity for Capsicum annum to dose of 0.5- 10 kGy with particle size selected by means of a mesh of opening of 53 {mu} m, while for Origanum vulgare L., the more intense emission is observed with 149 {mu} m. In the interval of dose 12- 45 kGy the maximum in intensity emission it was presented in 53 {mu} m in both cases. For the case of 10 {mu} m, the TL emissions were of smaller intensity, and were achieved glow curves in a clear, defined way and an overlapping that allows to center the maximum of TL emission, in a defined temperature 126 C for Origanum vulgare L., and 166 C for Capsicum annum. The behavior before described is related with the composition of the samples. For Capsicum annum it was found Quartz (60%), Albite (30%) and Ortosa (10%), while Origanum vulgare stops L., Quartz (50%), Calcite (20%), Albite (20%) and Clay (10%). The homogenization of the samples is an important factor because exists high probability of avoiding as much as possible rests of organic matter traces that can contribute to the total signal of the glow curves. Likewise the defects that pollute from a natural way to each one of the minerals found in the samples, they play an outstanding role in the TL emissions. Although to the interacting the gamma radiation with the poly minerals of different particle sizes, there is a certain energy transfer that will be translated in the absorbed dose and this it

  1. Shear-hosted base metal mineralisation at the Dana Peaks, Murchison Mountains, Fiordland, New Zealand

    International Nuclear Information System (INIS)

    Darran Suite dioritic, tonalitic and granodioritic plutonic rocks and schistose Loch Burn Formation volcaniclastic rocks in the central Murchison Mountains at the Dana Peaks have been affected by widespread biotite-sericite-chlorite-albite-quartz-pyrite ± carbonate ± epidote/clinozoisite ± titanite/rutile ± actinolite alteration. More intense, paler coloured sericite-albite-quartz-pyrite ± carbonate alteration is concentrated along orange weathered shear zones. Alteration assemblages are transitional between those commonly referred to as propylitic, potassic and phyllic. Altered rocks contain anomalous concentrations of copper, lead, zinc and silver over an area of c. 2.56 km. Metal concentrations 2-5 times those typical of Darran Suite plutonic rocks and the Loch Burn Formation are commonly associated with more extensive weak to moderate intensity alteration. Higher metal grades up to c. 0.5% copper, 1% zinc, 1.3% lead and 30 ppm silver are concentrated in or adjacent to the 1-5 m wide, more intensely altered shear zones which contain entrained lenses of pyritised country rock, breccias and quartz ± K-feldspar ± chlorite ± carbonate ± hematite ± tourmaline veins. Some mineralised rocks also contain traces of tungsten (2-7 ppm), arsenic (<5-35 ppm) and tellurium (0.2-5.4 ppm). Most samples lack detectable molybdenum (<3 ppm), gold (<0.004 ppm) or bismuth (<0.2 ppm), with atypical higher values (40, 0.03 and 50 ppm, respectively) generally restricted to the most intensely altered and/or deformed rocks. The mineralised rocks show a close spatial and temporal relationship with several narrow ductile shear zones that probably developed in the Early Cretaceous between c. 128 and 110 Ma. Mineralised shear zones form minor splays off larger shear zones that are part of a major intra-arc fault system, active along or near the boundary between inboard and outboard parts of the Median Batholith at this time. Traces of similar lead mineralisation are present at the

  2. Retrograde metasomatic effects on phase assemblages in an interlayered blueschist-greenschist sequence (Coastal Cordillera, Chile) (United States)

    Halama, Ralf; Konrad-Schmolke, Matthias


    Interlayered blueschists and greenschists of the Coastal Cordillera (Chile) are part of a Late Palaeozoic accretionary complex. They represent metavolcanic rocks with oceanic affinities based on predominantly OIB-type REE patterns and immobile trace element ratios. Both rock types have similar mineralogies, albeit with different mineral modal abundances. Amphibole is the major mafic mineral and varies compositionally from glaucophane to actinolite. The presence of glaucophane relicts as cores in zoned amphiboles in both blueschists and greenschists is evidence for a pervasive high-pressure metamorphic stage, indicating that tectonic juxtaposition is an unlikely explanation for the cm-dm scale interlayering. During exhumation, a retrograde greenschist-facies overprint stabilized chlorite + albite + winchitic/actinolitic amphibole + phengitic white mica ± epidote ± K-feldspar at 0.4 ± 0.1 GPa. Geochemical variability can be partly ascribed to primary magmatic and partly to secondary metasomatic processes that occurred under greenschist-facies conditions. Isocon diagrams of several adjacent blueschist-greenschist pairs with similar protolith geochemistry were used to evaluate metasomatic changes due to retrograde fluid-rock interaction. The most important geochemical changes are depletion of Si and Na and addition of water in the greenschists compared to the blueschists. Transition metals and LILE are mobilized to varying degrees. The unsystematic deviations from magmatic fractionation trends suggest open system conditions and influx of an external fluid. Pseudosection and water isopleth calculations show that the rocks were dehydrating during most of their exhumation history and remained at water-saturated conditions. The mineralogical changes, in particular breakdown of blue amphibole and replacement by chlorite, albite and calcic/sodic-calcic amphibole, are the prime cause for the distinct coloring. Pseudo-binary phase diagrams were used as a means to link bulk

  3. Pegmatite geology of the Shelby district, North Carolina (United States)

    Griffitts, Wallace R.


    The Shelby district is divided into a northwestern and a southeastern province. The rocks in the southeastern province include various units in the Battleground schist formation and the Yorkville granodiorite. Those in the northwestern province include the Carolina gneiss, with its Shelby gneiss member, and the Toluca quartz monzonite. The Cherryville quartz monzonite forms a batholith that is just west of the boundary between the two provinces. Pegmatites related to both the Toluca and the Cherryville quartz monzonites lie in the Carolina gneiss and many dikes of pegmatite that are related to the Cherryville quartz monzonite are in the tin-spodumene belt that lies along the boundary between provinces. The rocks of the southeastern province have been bent into steep isoclinal folds; those of the northwestern province were bent into open folds and gently-dipping isoclinal folds. The rocks to the southeast have been metamorphosed in the epidote-amphibolite facies whereas the rocks to the northwest represent the amphibolite or granulite facies. The pegmatites related to the Toluca quartz monzonite form sills, dikes, and concordant lenses in the Carolina gneiss, as well as dikes in the Toluca quartz monzonite. The bodies are unzoned and consist mainly of gneissic microcline-plagioclase-quartz pegmatite. The pegmatites related to the Cherryville quartz monzonite form dikes and disconformable lenses in the Carolina gneiss and the Toluca quartz monzonite. These pegmatites range widely in composition and many are zoned. The dikes west of the Cherryville batholith are rich in muscovite and plagioclase and may contain no microcline or only a moderate amount of microcline. Quartz cores and microcline-rich intermediate zones are common. Similar pegmatite forms dikes along the west edge of the tin-spodumene belt. The tin-spodumene belt containes albite-microcline-spodumene-quartz pegmatite. These dikes of albitic pegmatite are largest and most nearly parallel to one another

  4. Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation (United States)

    Behrens, Harald; Zhang, Youxue


    The effect of dissolved water on the diffusivity of Ar in glasses and melts of rhyolitic and albitic compositions was investigated experimentally at pressures up to 1500 MPa and water contents of 0.1-5 wt%. The data for water-poor rhyolitic composition at 500 MPa can be described in the whole temperature range of 480-1102°C by a simple Arrhenius relationship DAr=2.14×10 -6 m 2/s exp(-18 883/ T). A 4.0 wt% increase in water content increases the Ar diffusivity by approximately one order of magnitude in both rhyolitic and albitic melts at 1000°C. In contrast to viscosity and total water diffusion, an exponential dependence of Ar diffusivity on water content was observed for the rhyolitic composition in the whole range of water contents. For water-poor rhyolite, Ar diffusivity depends on pressure with an apparent activation volume of 13-15 cm 3/mol at pressures up to 800 MPa. For water-rich rhyolite (˜5 wt% water), there is no significant pressure effect at 1000°C in the range 500-1500 MPa. Combining our data with previous data from Carroll [M.R. Carroll, Earth Planet. Sci. Lett. 103 (1991) 156-168], Ar diffusivity (in 10 -12 m 2/s) in rhyolitic melts can be expressed as: D Ar= exp[( 14.627- 17 913/T- 2.569P/T)+( 35 936/T+ 27.42P/T)X water] where T is in K, P in MPa, and Xwater is the mol fraction of water on a single oxygen basis. Except for two outlier points, error of estimates is ≤0.455 in terms of ln D for all data, covering a wide range of temperatures (480-1200°C), pressures (0.1-1500 MPa), and water contents (0.1-5 wt%). The new Ar diffusion data support the assumption that molecular H 2O diffusivity exponentially increases with water content [Y. Zhang, H. Behrens, Chem. Geol. 169 (2000) 243-262].

  5. Alkali element enrichments on the BABBs at the IODP Expedition 333 Site C0012 in the northern Shikoku Basin (United States)

    Haraguchi, S.; Nakamura, K.; Fujinaga, K.


    The Shikoku Basin is a back arc basin located westside of the Izu-Ogasawara (Bonin) arc, spreading was from 25 to 15 Ma. The drilling of the DSDP, ODP and IODP recovered the backarc basin basalt (BABB) of the Shikoku Basin. Site C0012, south of the Kii Peninsula, was operated during the IODP Exp 333, and BABB was recovered 100m thickness under the 520m of sediment. This BABB is divided into upper aphyric pillow (Unit 1) and lower massive flow (Unit 2) divided at the 560 mbsf, and show variable degree of alteration, clay mineral and zeolite depositions. SiO2 and MgO contents of these basalts are 47-55 and 5-8 wt%. These basalts show wide variation of enrichment of alkali elements, 2.3-7.5 and 0.4-4.2 wt% of Na2O and K2O. Na2O+K2O contents show 3.2-8.0 wt%, and 2 wt% higher trends than other BABBs in the Shikoku Basin at the same SiO2 contents. Na2O and K2O show proportional and anti-proportional trends with increasing LOI. Therefore, both alkali element enrichments in these rocks are caused by secondary mineralization, and host phase of Na2O is hydrous and that of K2O is anhydrous minerals. Secondary mineral phases was mainly identified by XRD. The identified host phases of Na are analcime and thomsonite. Analcime is observed in rocks of more than 4 wt% of Na2O. Chlorite and smectite are identified to clay minerals. This mineral assemblage indicates the high-temperature zeolite facies alteration. The host phases of K are mainly identified into K-feldspar. We assume that secondary mineralization of K-fd is associated with low-temperature albitization. Compared to the lithostratigraphy, the Na enrichment is prominent in the Unit 1 and upper 20 m of the Unit 2, and the K enrichment is prominent in lower part of the Unit 2. We consider that the Na enrichment associated with zeolite depositions occurred under high water/rock ratio with active hydrothermal circulation because of high water permeability of pillow lava, and K enrichment associated with albitization occurred

  6. Nanoscale transient porosity controls large-scale metamorphic fluid flow (United States)

    Plümper, Oliver; Botan, Alexandru; Los, Catharina; Malthe-Sørenssen, Anders; Jamtveit, Bjørn


    The reaction of fluids with rocks is fundamental for Earth's dynamics as they facilitate heat/mass transfer and induce volume changes, weaknesses and instabilities in rock masses that localize deformation enabling tectonic responses to plate motion. During these fluid-rock interactions it is the ability of a rock to transmit fluid, its permeability, that controls the rates of metamorphic reactions. However, although some geological environments (e.g., sediments) are open to fluids, the majority of solid rocks (e.g., granites, elcogites, peridotites, etc.) are nearly impermeable. Surprisingly though, even in rocks that are nominally impermeable widespread fluid-rock interactions are observed leading to the question: How can fluids migrate through vast amounts of nominally impermeable rocks? Here we investigate one of the most wide-spread fluid-mediated metamorphic processes in the Earth's crust, the albitization of feldspatic rocks. We show that fluid flow and element mobilization during albitization is controlled by an interaction between grain boundary diffusion and reaction front migration through an interface-coupled dissolution-precipitation process. Using a combination of focused ion beam scanning electron microscopy (FIB-SEM)-assisted nanotomography combined with transmission electron microscopy (TEM) reveals that the porosity is dictated by pore channels with a pore diameter ranging between 10 to 100 nm. Three-dimensional visualization of the feldspar pore network reveals that the pore channels must have been connected during the replacement reaction. Analysis of the pore aspect ratios suggests that a Rayleigh-Taylor-type instability associated to surface energy minimization caused the disconnection of the pore channels. Fluid transport in nanometer-sized objects with at least one characteristic dimension below 100 nm enables the occurrence of physical phenomena that are impossible at bigger length scales. Thus, on the basis of our microstructural

  7. Experimental Study of Cement - Sandstone/Shale - Brine - CO2 Interactions

    Directory of Open Access Journals (Sweden)

    Carroll Susan A


    Full Text Available Abstract Background Reactive-transport simulation is a tool that is being used to estimate long-term trapping of CO2, and wellbore and cap rock integrity for geologic CO2 storage. We reacted end member components of a heterolithic sandstone and shale unit that forms the upper section of the In Salah Gas Project carbon storage reservoir in Krechba, Algeria with supercritical CO2, brine, and with/without cement at reservoir conditions to develop experimentally constrained geochemical models for use in reactive transport simulations. Results We observe marked changes in solution composition when CO2 reacted with cement, sandstone, and shale components at reservoir conditions. The geochemical model for the reaction of sandstone and shale with CO2 and brine is a simple one in which albite, chlorite, illite and carbonate minerals partially dissolve and boehmite, smectite, and amorphous silica precipitate. The geochemical model for the wellbore environment is also fairly simple, in which alkaline cements and rock react with CO2-rich brines to form an Fe containing calcite, amorphous silica, smectite and boehmite or amorphous Al(OH3. Conclusions Our research shows that relatively simple geochemical models can describe the dominant reactions that are likely to occur when CO2 is stored in deep saline aquifers sealed with overlying shale cap rocks, as well as the dominant reactions for cement carbonation at the wellbore interface.

  8. A Petrographic and Mineralogical Study of Volcanic Rocks from the Mayaxueshan Area, North Qilian Fold Belt, NW China

    Institute of Scientific and Technical Information of China (English)

    徐达伟; 萧炎宏


    The Ordovician volcanic rocks in the Mayaxueshan area have been pervasively altered or metamorphosedand contain abundant secondary minerals such as albite, chlorite, epidote, prehnite, pumpellyite, actinolite, titanite, quartz,and/or calcite. They were denoted as spilites or spilitic rocks in terms of their petrographic features and mineral assem-blages. The metamorphic grades of the volcanic rocks are equivalent to that of the intercalated metaclastic rocks. Thisindicates that both the spilitic volcanic rocks and metaclastic rocks in the Mayaxueshan area have formed as a result ofCaledonian regional metamorphism. We suggest that the previously denoted spilitic rocks or altered volcanic rocks shouldbe re-denoted as metabasalts or metabasaltic rocks. The metamorphic grade of the volcanic rocks increases with their age:prehnite-pumpellyite facies for the upper part of the Middle Ordovician volcanic rocks, prehnite-pumpellyite to lowergreenschist facies for the lower part of the Middle Ordovician volcanic rocks, and lower greenschist facies for the LowerOrdovician volcanic rocks. The P-T conditions are estimated as T = 240 - 290C and P = 1.5 - 4.5 kbar for the lower partof the Middle Ordovician rocks, and T = ~ 300~C for the Lower Ordovician rocks. The variations of mineral assemblagesoccurring at different domains of the volcanic rocks were controlled by the variations of the effective bulk composition inthose domains during metamorphism. The geochemical characteristics of Mg-Al chromite in the Mayaxueshan volcanicrocks are consistent with an origin of island arc environment.

  9. The use of natural radiation for prospecting valuable resources

    International Nuclear Information System (INIS)

    Full text: The uranium trapped by minerals during its formation gives the possibility of determining their age of creation, or the age of their last heating event. Uranium atoms in the mineral naturally decay by spontaneous fission creating tracks whose number is proportional to the mineral age. The results of two minerals are presented: Apatite and Zircon. Apatite from the Cerro de Mercado, Durango, Mexico is internationally considered as a standard. Apatite is also used to determine the thermal history of mineral and oil deposits. Another mineral, Epidote is considered as a geothermic-chronometer in geothermal fields whose presence and crystalline degree provides information, along with other parameters, on the genesis and thermal evolution of the reservoir. X-ray diffraction, scanning electron microscopy and neutron activation analysis identified in Los Azufres field the presence of epidote species (clinozoisite and piamontite) in most of the cases at depths deeper than 1100 mosl. Isothermal curves are matched in a three-dimensional graph were other minerals (quartz, albite, clinoclhore, calcite and anorthite) are also located. The presence of these minerals reflects thermo dynamical and chemical processes in the reservoir. The energy source in geothermal fields is associated to the faults produced by the enormous activity of geothermal fields escaping from the reservoir. The locations of those geological structures define areas for closer prospecting through radon mapping, as it shown in the paper. (orig.)

  10. Reaction-path calculations of groundwater chemistry and mineral formation at Rainier Mesa, Nevada

    International Nuclear Information System (INIS)

    Reaction-patch calculations of groundwater chemistry and mineral formation at Rainier Mesa, Nevada, have been done using a model of volcanic-glass dissolution by water that is initially saturated with CO2. In the reaction-path calculation, rate processes control the availability of species through dissolution of volcanic glass, and equilibrium processes distribute the species between the aqueous phase and mineral phases in equilibrium at each step in the reaction path. The EQ3/6 chemical-equilibrium programs were used for the calculation. Formation constants were estimated for three zeolites (clinoptilolite, mordenite, and heulandite), so they could be considered as possible mineral precipitates. The first stage of mineral evolution, from volcanic glass to a cristobalite, smectite clay, and zeolite mixture, was modeled quite well. Predicted aqueous-phase compositions and precipitates agree with observations at Rainier Mesa and other Nevada Test Site areas. Further mineral evolution, to quartz, clay, analcime, and albite mixtures, was also modeled. Decreasing aqueous silica activity from the first stage, where cristobalite precipitates, to later stages, where quartz is present, was the controlling variable in the mineral evolution. 30 references, 20 figures, 4 tables

  11. Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil

    International Nuclear Information System (INIS)

    U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on an amphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 ± 9 Ma and 2006 ± 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 ± 18 Ma and 2031 ± 40 Ma). However, protolith ages for the granodiorite (2366 ± 8 Ma) and the granulite (2489 ± 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites. (author)

  12. Aqueous Chemistry of Typical Geothermal Springs with Deep Faults in Xinyi and Fengshun in Guangdong Province, China

    Institute of Scientific and Technical Information of China (English)

    Guoping Lu; Runfang Liu


    This paper investigated aqueous chemistry for two geothermal spring groups responsive and sensitive to flow fluctuations induced by earthquakes. Quake monitorings are favored for their be-ing in residential areas with well-preserved natural flow systems in Xinyi City’s Xijiang Hot Springs and Fengshun County’s Shihu Hot Spring. The hot springs are typical in temperatures and flow rates in southern China’s Guangdong Province. Physical and chemical conditions deep down in the heat sources are important constraints on earthquake, fluid flow, reactive solute transport and heat transfer, but re-main challenging to address via field observations and numerical experiments. In this paper, we made daily and annual observations on flow rates, temperature, and/or aqueous chemistry. We employed strontium isotopes as tracers for the water sources, equilibrium phase diagram for K-feldspar and albite stability, and Na-K-Mg diagram for heat reservoir temperatures. The abundant sulfite content in Xi-jiang Hot Springs is discussed. Our main finding are that the deep fault springs are characterized by low reduction-oxidation potential at around-200–-150 mV and relatively large daily flow variations. The re-sults provide scientific background features on the field sites regarding earthquake monitoring and pre-dictions and geothermal reservoir.

  13. Uranium occurrences of the Thunder Bay-Nipigon-Marathon area

    International Nuclear Information System (INIS)

    During the 1981, 1982 and 1983 field seasons an inventory of all known uranium occurrences in the North Central Region of Ontario was undertaken. Three major categories of uranium occurrences were identified: uranium associated with the rocks of the Quetico Subprovince; uranium associated with the Proterozoic/Archean unconformity; and uranium associated with alkalic and carbonatite rocks of Late Precambrian age. Occurrences associated with the Quetico Belt are in white, albite-quartz-muscovite pegmatites. Occurrences associated with the Proterozoic/Archean unconformity are usually of high gradee (up to 12% U3O8), nearly always hematized and are related to fault or shear zones proximal to the unconformity. Although of high grade, many of the unconformity related occurrences are very narrow (<1 m). Alkalic and carbonatite rocks of Late Precambrian age are an important source of uranium but possible metallurgical problems might downgrade their potential. The Quetico Subprovince is anomalously high in background uranium, and therefore contains important source rocks for uranium. Areas that have the highest potential for uranium deposits in the North Central Region are the Nipigon Basin area, and the areas underlain by the Gunflint and Rove Formations. All the high grade vein-type uranium deposits related to the unconformity are found within the Nipigon Basin. 126 refs

  14. Edingtonite from the Shiromaru mine, Tokyo, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Matsubara, S.; Kato, A. (National Science Museum, Tokyo (Japan))


    Edingtonite from the bedded Mn ore deposit of the Shiromaru mine, Tokyo, Japan was found as the subordinate constituent of a thin fissure dominantly filled with celsian. It cut a low grade Mn ore composed of braunite, hematite, cymrite, celsian and albite. Its empirical formula was Ba{sub 1.00}Al{sub 2.00}Si{sub 3.00}O{sub 10} {center dot}4H{sub 2}O by microprobe analysis, and its X-ray powder pattern was indexed on an orthorhombic cell. It was a later product than celsian in the fissure where the aggregate of compositionally varied grains occupied wall side portions probably reserving the original texture. The fissure showed a co-existence example of feldspars and zeolites featured by the same elements, and it was probably the first co-existence example with Ba element. Both tectosilicates were featured by the four-membered ring composed of (Si,Al)O{sub 4} as basic units of a tectosilicate framework. The edingtonite was probably a hydrothermally altered mineral under a condition relatively poor in silicate. 10 refs., 1 fig., 2 tabs.

  15. Thermoluminescent characteristics of oregano and paprika

    International Nuclear Information System (INIS)

    The poly minerals from oregano and paprika were selected according to different sizes, i.e 10, 53, 74, 149 μm, and they were exposed to ionizing gamma radiation in the range of doses 0.5-45 kGy. The glow curves from these spices show an abroad TL band, centered around 150 C and by XRD analysis shows a mono mineral composition mainly quartz and feldspar, including albite, ortose and clay. The fading behavior was related to the quartz, feldspar and calcite TL properties and shown the stability of the traps associated to the defects generated by irradiation in the samples. The tendency of the TL integrated was increased with the grain size for oregano and can be related to the different energy values associated to the activation energy of the traps in the monominerals. The glow curve TL from poly minerals was analyzed and it is possible to use the dosimetric property of the poly minerals from spices for detect irradiated foodstuffs. (Author)

  16. Assessment of Suspended Sediments Concentration in Surface Waters, Using Modis Images

    Directory of Open Access Journals (Sweden)

    Mobasheri M. Reza


    Full Text Available Remote sensing from air-borne and space-borne sensors have proved to be a useful method for Suspended Sediment Concentration (SSC estimation as it provides an instantaneous and synoptic view of suspended sediments that would otherwise be unavailable. The reason for the success of remote sensing in such surveys is the strong positive relationship that exists between SSC and remotely sensed water leaving radiance. To find an algorithm relating SSC to spectral radiance over Bahmansheer River Estuary at the North-West of Persian Gulf, a three-month field expedition (April to June 2003 was conducted while the MODIS sensor on board Terra simultaneously flew over the scene. Fifty seven samples in fifteen trips were collected. The collected samples were analyzed by measuring concentration, diameters of the sediment particles and by determining the sediment constituents. Total concentration ranged between 30 and 500 mg, the range of particle diameter was from less than a micrometer to more than 20 micrometers and finally it was found that the sediment was composed of Quartz, Kaolinite, Orthoclase, Chlorite, Calcite, Gypsum, Muscovite, Halite, Anhydrite, Apatite, Biotite and a low amount of Albite. It is found that the spectral characteristics of these compositions are partly responsible for the reflected and/or scattered energy in different bands while the correlation between larger suspended particle concentration and spectral radiance was profound.

  17. Oregano and Paprika Spices: Their Thermoluminescent Characteristics for Food Irradiation Dose Assessment

    Directory of Open Access Journals (Sweden)

    E. Cruz-Zaragoza


    Full Text Available The polyminerals content from commercial dust oregano and paprika were extracted and selected by sizes of < 10, 10-53, 53-74 and 74-149 µm and exposed to gamma radiation at different doses in the range 0.5-45 kGy. The glow curves from these polyminerals show an abroad TL band, centered around 450 K and composed of 9-10 glow peaks as calculated by a deconvolution procedure. The XRD analysis shows a composition of mainly quartz and feldspar, including albite, ortose and clay. The fading behavior can be mainly related to the low temperature peaks of the various minerals contained in the spices. The intensity the TL emission increases as the grain size increases for both spices. The TL properties of the polymineral contain of the spices were analyzed and it is possible to conclude that the polymineral content of both oregano and paprika can be used as efficient and practical way to determine the thermoluminescence dose assessment in herbs and spices exposed to ionizing radiation.

  18. Characterization of rock samples localized in some sites of the Mexican Pacific coast; Caracterizacion de muestras de rocas localizadas en algunos sitios de la costa del Pacifico Mexicano

    Energy Technology Data Exchange (ETDEWEB)

    Pena, P.; Torre, J. de la; Falcon, T.; Segovia, N. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico); Azorin, J. [Universidad Autonoma Metropolitana-Iztapalapa C.P. 09340 Mexico D.F. (Mexico)


    Geophysical studies in zones of high seismicity have showed differences in the content of radioactive material that is used in the study of the geochemical behavior of the subsoil. In an emanometric mapping of radon in soil realized in the Mexican Pacific coast were finding distinct levels in zones with different lithology. With the finality to know the mineralization types in two zones of study which are localized in the Guerrero coast and they belonging to terrains named Guerrero and Xolapa it was determined the mineralogic characteristics in two types of rocks. The identification of the rocks was realized by X-ray diffraction and was determined the elemental chemical composition using a scanning electron microscope. It was indicated in the results obtained that in the two types of rocks were found minerals such as: quartz, albite, microcline anortite, ferroactinolite and biotite. However, it was found differences between them by the presence of their mineralogic compounds because in the rock belonging to Xolapa terrain were presented whereas in the rock localized in the Guerrero terrain were presented sodic and potassic feldspars. The analysis by the Elemental Chemical Composition technique (Energy Dispersive Spectroscopy) corroborated the results obtained by the X-ray diffraction technique. (Author)

  19. Hydrothermal alteration studies of gabbros from Northern Central Indian Ridge and their geodynamic implications (United States)

    Ray, Dwijesh; Mevel, Catherine; Banerjee, Ranadip


    Mylonitic gabbro and altered gabbro were recovered from off-axis high and corner high locations at ridge-transform intersection, adjacent to Vityaz transform fault of the slow spreading (32-35 mm/yr, full spreading) Northern Central Indian Ridge. Both the varieties show signatures of extensive alteration caused due to interaction with sea water. Mylonitic gabbro represents high temperature metamorphism (˜700-800°C) and comprised of hornblende mineral which exhibits well defined foliation/gneissic appearance along with dynamically recrystallised plagioclase grains frequently intercalated with magnetite-ilmenite. Altered gabbro from corner high generally includes low temperature greenschist grade (˜300°C) mineralogical assemblages: chlorite, albite, quartz and locally magnesio hornblende. Crystal plastic deformation resulted in mylonite formation and often porphyroclasts of plagioclase and clinopyroxene grains, while altered gabbro locally exhibits cataclastic texture. Presence of Vityaz transform fault and adjacent megamullion at the weakly magmatic ridge-transform intersection and off-axis high locations prompted the present scenario very much conducive for hydrothermal circulation and further facilitate the exhumation of present suite of gabbro.

  20. Clay minerals in uraniferous deposit of Imouraren (Tim Mersoi basin, Niger): implications on genesis of deposit and on ore treatment process

    International Nuclear Information System (INIS)

    Nigerian uraniferous deposits are located in carboniferous and Jurassic formations of Tim Mersoi basin. AREVA is shareholder of 3 mine sites in this area: SOMAIR and COMINAK, both in exploitation since 1960's and IMOURAREN, 80 km further South, whose exploitation is planned for 2015. Mineralization of Imouraren deposit is included in the fluvial formation of Tchirezrine 2 (Jurassic), composed of channels and flood plains. Facies of channel in-fillings range from coarse sandstones to siltstones, while overflow facies are composed of analcimolites. Secondary mineralogy was acquired during 2 stages: 1- diagenesis, with formation of clay minerals, analcime, secondary quartz and albites, and 2- stage of fluids circulations, which induced alteration of detrital and diagenetic minerals, formation of new phases and uranium deposition. A mineralogical zoning, at the scale of deposit resulted from this alteration. The heterogeneity of Tchirezrine 2, at the level of both facies and mineralogy, is also evidenced during ore treatment, as ore reacts differently depending on its source, with sometimes problems of U recovery. Ore treatment tests showed that analcimes and chlorites were both penalizing minerals, because of 1- the sequestration of U-bearing minerals into analcimes, 2- their dissolution which trends to move away from U solubilization conditions (pH and Eh) and to form numerous sulfates, and 3- problems of percolation. A detection method of analcime-rich ores, based on infrared spectroscopy, was developed in order to optimize ore blending and so to reduce negative effects during ore treatment process. (author)

  1. A preliminary comparative study of environmental air born particulate pollution in Lahore and Faisalabad

    International Nuclear Information System (INIS)

    Suspended particulate matter (SPM) collected from Lahore and Faisalabad, two big industrial cities of Punjab (Pakistan), were subjected to quantities phase analysis by x-ray powder diffraction method using the matrix flushing technique. The experimental results show that quartz was the major SPM constituent with wt. percentage 33.5% for Faisalabad and 28.7% for Lahore. The second compound was found to be illite with wt. percentage 21.3% for Faisalabad and 28.1% for Lahore. The third and fourth compounds in order of decrease wt. percentage were chlorite 14.6% for Faisalabad and 19.1% Lahore and albite 15.7% for Faisalabad and 12.3 for Lahore respectively. The Faisalabad SPM samples were found on the average to contain more amounts of quartz as compared to Lahore SPM samples. This shows that Faisalabad is more polluted that Lahore, as quartz is not utilized in micro physical processes in the atmosphere and its fine particles stay long in the air. The spread of diseases like bronchitis in the cities is probably due to this pollutant as its fine particles go deep into lungs and have no way to escape. (author)

  2. Determination of the mineral stability field of evolving groundwater in the Lake Bosumtwi impact crater and surrounding areas (United States)

    Loh, Yvonne Sena Akosua; Yidana, Sandow Mark; Banoeng-Yakubo, Bruce; Sakyi, Patrick Asamoah; Addai, Millicent Obeng; Asiedu, Daniel Kwadwo


    Conventional graphical techniques, mass balance geochemical modelling, and multivariate statistical methods were jointly applied to hydrogeochemical data of groundwater from the fractured rock aquifer system, and surface water in the Bosumtwi and surrounding areas to reveal evolutionary trends and the characteristics of evolving groundwater in the area. Four clusters distinguished from the Q-mode hierarchical cluster analysis (HCA) comprised three main groundwater associations and one surface water group (lake water). Although both water resources are of low mineralization (TDS < 1000 mg/l), it was observed that the groundwater from the upper catchment with hydrochemical facies dominated by Nasbnd Mgsbnd HCO3-, evolves to Casbnd Mgsbnd and mixed cations HCO3- water types at the lower reaches. The lake water on the other hand is Nasbnd HCO3- water type. Results from principal component analyses (PCA) and other geochemical interpretations distinguished three sources of variations in the hydrochemistry. Saturation indices of possible reactive mineral phases show groundwater undersaturation relative to albite, anorthite, aragonite, barite, calcite, chlorite, chrysotile, dolomite, gypsum, k-felspar and talc, and supersaturation with respect to gibbsite, kaolinite, Ca-montmorillonite and k-mica in the area. The PCA and other geochemical interpretation identify weathering of feldspars and carbonate mineral dissolution as predominantly influencing the hydrochemistry of the groundwater. Hydrolysis of the aluminosilicates causes the groundwater to reach equilibrium with kaolinite. In addition to dissolution of silicates, the chemical composition of the lake water has been influenced by evaporation and consequent carbonate saturation.

  3. Mineralogical characterization of a meteorite impact in Carancas, Puno

    International Nuclear Information System (INIS)

    We report the results of the study of a meteorite that impacted an inhabited zone in the neighborhood of the town of Carancas, Puno Region, about 1,300 km south of Lima. The analysis carried out by X ray diffractometry, transmission Moessbauer spectroscopy (at room temperature and at 4,2 K), and by energy dispersive X ray fluorescence reveal the presence in the meteorite simple of magnetic sites assigned to the Fe-Ni and troilite (Fe,S) phases, and of 3 paramagnetic doublets, two of them assigned to Fe2+, one associated to olivine and the other to pyroxene, and the third one due to a site occupied by Fe3+, which can be associated to oxides in a superparamagnetic state and/or by an Fe hydroxide. The soil samples from the crater reveal a composition that consists mainly of quartz, albite and impactites such as coesite and stishovite (SiO2). The occurrence of these phases with a high content of SiO2 in the crater soils strengthens the hypothesis of their origin induced by impact; we observe also the presence of the Fe oxide hematite, of aluminum silicates such as illite and montmorillonite, and an unassigned phase of Fe3+. In general, the results obtained by these techniques complement each other rather well and allow the verification of the origin of the studied simples. (author).

  4. Mössbauer spectroscopy and X-ray diffraction analyses of clayey samples used as ceramic sourcing materials, in Peru

    International Nuclear Information System (INIS)

    The ceramic industry is an important area of economic activity in the Ayacucho Region, in particular in the District of Quinua. As a consequence, there is a huge demand for clay to produce ceramic pastes in that region. This paper reports on results concerning the mineralogical characterization of four clayey samples, which were collected MAA and SPQA from the area Pampa de La Quinua with geographic coordinates 13° 02′ 49″ S 74° 08′ 03″ W, CE1M and CE2M from the Quinua locality 13° 03′ 07″ S 74° 08′ 31″ W, both in the District of Quinua, Province of Huamanga, Ayacucho, Peru. The chemical and mineralogical characterization of these samples was carried out with powder X-ray diffraction detecting quartz, albite, montmorillonite, kaolinite and glauconite mineral phases, Mössbauer spectroscopy detected iron in kaolinite, glauconite and montmorillonite minerals. Chemical analysis was performed through scanning electron microscopy and energy dispersive X-ray spectroscopy. Data obtained from the combination of these techniques provided relevant information about the morphology, chemical composition, and the mineralogy of samples.

  5. Comparative adsorption of sup 90 Sr on soil sediments, pure clay phases and feldspar minerals

    International Nuclear Information System (INIS)

    Laboratory batch experiments were conducted to determine the adsorption of 90 Sr by a soil sediment, mineralogically pure clay phases (vermiculites, smectites and illites) and feldspar minerals (adesine, albite, microcline and oligoclase) as a function of ionic composition. The clay minerals were present at different proportion in the soil sediment. The important adsorbing phases and the adsorption mechanism(s) can be determined from the studies. Twenty two stock solutions were prepared with concentrations of the major cations Ca, Mg and Na and were varied from 0.0 to 0.00312 M, 0.0 to 0.00165 M, and 0.0 to 0.00312 M, respectively. The experiments yielded adsorption coefficient values K sub d that could be described by equations. Theoretical slope value -1 for pure ion-exchange mechanism of strontium adsorption onto Ca-saturated clay was described. The slopes obtained in the experiments represented an average of adsorption on several different mineral surfaces having different relative affinities for strontium, calcium and magnesium. Experiment results showed that strontium was adsorbed to ion-exchange sites and that calcium and magnesium cations were effective competitors for these sites. Pure clay minerals yielded adsorption coefficients that could be described by equations slopes -1.0 similar to the theoretical value. The feldspar minerals yielded slope ranges from -072 to -1.13, and the sediments slope value of -0.81. These suggest that ion-exchange was the dominant adsorption mechanism for strontium

  6. Bohemian circular structure, Czechoslovakia: Search for the impact evidence (United States)

    Rajlich, Petr


    Test of the impact hypothesis for the origin of the circular, 260-km-diameter structure of the Bohemian Massif led to the discovery of glasses and breccias in the Upper Proterozoic sequence that can be compared to autogeneous breccias of larger craters. The black recrystallized glass contains small exsolution crystals of albite-oligoclase and biotite, regularly dispersed in the matrix recrystallized to quartz. The occurrence of these rocks is limited to a 1-sq-km area. It is directly underlain by the breccia of the pelitic and silty rocks cemented by the melted matrix, found on several tens of square kilometers. The melt has the same chemistry as rock fragments in major and in trace elements. It is slightly impoverished in water. The proportion of melted rocks to fragments varies from 1:5 to 10:1. The mineralogy of melt viens is the function of later, mostly contact metamorphism. On the contact of granitic plutons it abounds on sillimanite, cordierite, and small bullets of ilmenite. Immediately on the contact with syenodiorites it contains garnets. The metamorphism of the impact rock melt seems the most probable explanation of the mineralogy and the dry total fusion of rocks accompanied by the strong fragmentation. Other aspects of this investigation are discussed.

  7. Moessbauer spectroscopy and X-ray diffraction analyses of clayey samples used as ceramic sourcing materials, in Peru

    Energy Technology Data Exchange (ETDEWEB)

    Quille, Ruben, E-mail:; Bustamante, Angel [San Marcos National University, Laboratory of Ceramics and Nanomaterials, Faculty of Physical Sciences (Peru); Palomino, Ybar [National University of San Cristobal de Huamanga, Experimental Center of Ceramics (Peru)


    The ceramic industry is an important area of economic activity in the Ayacucho Region, in particular in the District of Quinua. As a consequence, there is a huge demand for clay to produce ceramic pastes in that region. This paper reports on results concerning the mineralogical characterization of four clayey samples, which were collected MAA and SPQA from the area Pampa de La Quinua with geographic coordinates 13 Degree-Sign 02 Prime 49 Double-Prime S 74 Degree-Sign 08 Prime 03 Double-Prime W, CE1M and CE2M from the Quinua locality 13 Degree-Sign 03 Prime 07 Double-Prime S 74 Degree-Sign 08 Prime 31 Double-Prime W, both in the District of Quinua, Province of Huamanga, Ayacucho, Peru. The chemical and mineralogical characterization of these samples was carried out with powder X-ray diffraction detecting quartz, albite, montmorillonite, kaolinite and glauconite mineral phases, Moessbauer spectroscopy detected iron in kaolinite, glauconite and montmorillonite minerals. Chemical analysis was performed through scanning electron microscopy and energy dispersive X-ray spectroscopy. Data obtained from the combination of these techniques provided relevant information about the morphology, chemical composition, and the mineralogy of samples.

  8. Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer

    Directory of Open Access Journals (Sweden)

    Rafiza Abdul Razak


    Full Text Available This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA using LUSI (Sidoarjo mud and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced.

  9. Use of a cranium-vessel determined by means of compound analysis

    International Nuclear Information System (INIS)

    Many human remains as bones, skin, teeth and others, were used in pre-hispanic cultures as tools or ritual objects. A human cranial vault filed in the Direccion de Antropologia Fisica presented particular and interesting cultural modifications. There are twelve drills used to restore by sewing the crane, in this way the piece resembles a pot. It has been established that it comes from North Mexico where such restoration work has been reported (Aveleyra, 1956) for containers made of vegetables (guaje). As the utilization of this kind of archaeological remain is unknown, the study of dust samples from the inside and the outside of the crane should provide hints on the products stored into it. In this study we present the X-ray diffraction results which show that the outer dusts are mainly constituted by albite, andesite and quartz, whereas in the inside the substances were mainly aluminosilicates and magnesium compounds. Hence, most probably, this crane was not used as a conventional container and it is linked to the concoction of magnesium and aluminosilicates containing products. This conclusion has to be correlated to that even nowadays, in both alternative and conventional medicine. (Author) 7 refs., 7 figs

  10. Use of a cranium-vessel determined by means of compound analysis; Uso de una vasija-craneo determinada por medio de analisis de compuesto

    Energy Technology Data Exchange (ETDEWEB)

    Leboreiro, I.; Pijoan, C.M.; Mansilla, J. [Direccion de Antropologia Fisica, INAH, Gandhi s/n, Polanco, 11560 Mexico D. F. (Mexico); Bosch, P. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)


    Many human remains as bones, skin, teeth and others, were used in pre-hispanic cultures as tools or ritual objects. A human cranial vault filed in the Direccion de Antropologia Fisica presented particular and interesting cultural modifications. There are twelve drills used to restore by sewing the crane, in this way the piece resembles a pot. It has been established that it comes from North Mexico where such restoration work has been reported (Aveleyra, 1956) for containers made of vegetables (guaje). As the utilization of this kind of archaeological remain is unknown, the study of dust samples from the inside and the outside of the crane should provide hints on the products stored into it. In this study we present the X-ray diffraction results which show that the outer dusts are mainly constituted by albite, andesite and quartz, whereas in the inside the substances were mainly aluminosilicates and magnesium compounds. Hence, most probably, this crane was not used as a conventional container and it is linked to the concoction of magnesium and aluminosilicates containing products. This conclusion has to be correlated to that even nowadays, in both alternative and conventional medicine. (Author) 7 refs., 7 figs.

  11. A common high-pressure metamorphic evolution of interlayered eclogites and metasediments from the 'ultrahigh-pressure unit' of the Tianshan metamorphic belt in China (United States)

    Li, Ji-Lei; Klemd, Reiner; Gao, Jun; Jiang, Tuo; Song, Yun-Hui


    Petrological and mineralogical data of interlayered eclogite, marble and quartz-mica schist from a drill core are used to constrain the metamorphic evolution of metavolcanics and intercalated metasediments in the Tianshan (ultra-)high-pressure/low-temperature [(U)HP/LT] metamorphic belt, NW China. The eclogite mainly consists of varying amounts of garnet, omphacite, quartz and zoisite, the marble of calcite (> 95 vol.%) with minor zoisite and phengite, and the schist of quartz and mica with minor calcite, chlorite, albite and garnet. Using garnet isopleth thermobarometry, pseudosection calculations for the eclogite and quartz-mica schist reveal a common metamorphic evolution under HP condition of both rock types that is also consistent with the temperature estimates for the marble using conventional thermometry. The uniform P-T paths of the interlayered eclogite and quartz-mica schist, as well as compatible temperature data of the marble, document that the whole rock suite constitutes a coherent HP unit during peak metamorphic conditions and exhumation. Thus protoliths of eclogite and associated sediments are believed to have undergone the same metamorphic evolution. In addition, the data gained by the present study of the HP rocks, which were collected in the northern part of the Chinese Tianshan (U)HP/LT belt, do not support the recently proposed tectonic scheme that this metamorphic terrane consists of a northern "coherent UHP unit" and a southern "coherent HP unit".

  12. Zircon Uranium-Lead dating, petrography and geochemistry for sub volcanic bodies in southwest of Birjand (Rich area)

    International Nuclear Information System (INIS)

    Rich area's sub volcanic bodies in southwest of Birjand have intruded into Upper Cretaceous ophiolite melange. These rocks are in diorite porphyry to monzonite porphyry range and their main texture is porphyry with micro granular groudmass. Plagioclase and green hornblende phenocrysts are made about 70% of these rocks. Plagioclases are andesine with albitic and carlsbad twining and distinct zoning which altered to calcium carbonate in central parts. Hornblende phenocrysts have altered partly to biotite so show a weakly potassic alteration. The average ratio of Ce/Yb in these rocks are 25.40 and shows they belong to enrich magmatic arc. There is a negative anomaly in high field strength elements such as P, Nb and Ti in these rocks which is a geochemical characteristic of continental margin magmatic arc. High ratio of LREE / HREE, Sr/Y (average is 38.14,) and the amount of SiO2, with the absent of Eu negative anomaly show that these rocks are very similar to high SiO2 adakites. High ratio of Sr/Y can be interpreted as high depth melting in plagioclase unstability and garnet stability field. The source of this magma can be an eclogite or garnet amphibolites which is derived from subducted metamorphosed oceanic plate in east of Iran. Dating with zircon uranium - lead show that this magmatic event occurred about 39.1 ± 0.7 Ma (Late Eocene).

  13. Hydrothermal alteration studies of gabbros from Northern Central Indian Ridge and their geodynamic implications

    Indian Academy of Sciences (India)

    Dwijesh Ray; Catherine Mevel; Ranadip Banerjee


    Mylonitic gabbro and altered gabbro were recovered from off-axis high and corner high locations at ridge-transform intersection, adjacent to Vityaz transform fault of the slow spreading (32–35mm/yr, full spreading) Northern Central Indian Ridge. Both the varieties show signatures of extensive alteration caused due to interaction with sea water. Mylonitic gabbro represents high temperature metamorphism (∼700–800° C) and comprised of hornblende mineral which exhibits well defined foliation/gneissic appearance along with dynamically recrystallised plagioclase grains frequently intercalated with magnetite-ilmenite. Altered gabbro from corner high generally includes low temperature greenschist grade (∼300° C) mineralogical assemblages: chlorite, albite, quartz and locally magnesio hornblende. Crystal plastic deformation resulted in mylonite formation and often porphyroclasts of plagioclase and clinopyroxene grains, while altered gabbro locally exhibits cataclastic texture. Presence of Vityaz transform fault and adjacent megamullion at the weakly magmatic ridge-transform intersection and off-axis high locations prompted the present scenario very much conducive for hydrothermal circulation and further facilitate the exhumation of present suite of gabbro.

  14. Luminescence characterization of a sodium rich feldspar

    International Nuclear Information System (INIS)

    This paper reports on the radioluminescence (RL) and thermoluminescence (TL) properties of a sodium rich feldspar ((Na,K)[AlSi3O8]) with a mean molecular composition of orthoclase (Or) and albite (Ab) of Or1Ab99. Despite the complexity of the luminescence signals of the sample, it is possible to determine six different emission bands at about 300, 380, 420, 460, 550 and 680 nm. The 300 nm emission can be associated to structural defects related to the recombination process in which the Na+ ion diffusion-limited is involved. The UV-blue emission band at (i) 380 nm is characteristic of mineral phases containing SiO4 tetrahedral and could be related to intrinsic defects in the lattice, (ii) the 420 nm band could be associated to the presence of Cu (II) ions placed next to the hole traps or the recombination on a centre formed from a hole-oxygen atom adjacent to two Al atoms (Al-O-Al) and (iii) the 460 nm waveband could be due to the presence of Ti4+. The green and red emissions are respectively associated to the presence of Mn2+ and Fe3+ ions. The ratio between the relative intensities, peaked at 290 (the more intense waveband) and 550 nm is about 10:1 in both TL and RL; this fact indicates that the efficiency of recombination centres does no changes regardless on the type of the process. (Author)

  15. Experimental determination of chlorite dissolution rates

    International Nuclear Information System (INIS)

    Current concepts of the geological disposal of low- and intermediate-level radioactive wastes in the UK envisage the construction of a mined facility (incorporating cementitious engineered barriers) in chlorite-bearing rocks. To model accurately the fluid-rock reactions within the disturbed zone surrounding a repository requires functions that describe mineral dissolution kinetics under pH conditions that vary from near neutral to highly alkaline. Therefore, an experimental study to determine the dissolution rates of Fe-rich chlorite has been undertaken as part of the Nirex Safety Assessment Research Program. Four experiments have been carried out at 25 C and four at 70 C, both sets using a range of NaCl/NaOH solutions of differing pH (of nominal pH 9.0, 10.3, 11.6 and 13.0 [at 25 C]). Dissolution rates have been calculated and were found to increase with increasing pH and temperature. However, increased pH resulted in non-stoichiometric dissolution possibly due to preferential dissolution of part of the chlorite structure relative to another, or reprecipitation of some elements as thin hydroxide or oxyhydroxide surface coatings on the chlorite. These results also show that chlorite dissolution is appreciably slower than that of albite and quartz at both 25 and 70 C, but slightly faster than that of muscovite at 70 C

  16. Insights on Structural, Petrographical, Mineralogical and Geochemical Approach on the Grahamstown Kaolin Deposit Genesis in the Eastern Cape, South Africa

    Directory of Open Access Journals (Sweden)

    Kakaba Madi


    Full Text Available The town of Grahamstown is known on the geological and mineralogical point of view mainly because of its kaolin deposit, which derived from the intense weathering of the Dwyka tillite of the Karoo Supergroup. The weathering is favoured by the occurrence of brittle structures and breccias of granites that contains considerable amount of feldspar. The purpose of this study is to examine the importance of structural control in the weathering process leading to the formation of kaolin, to check the petrographical data by comparing breccias found in the fresh tillite and those in the kaolin, to highlight the mineralogical composition in some samples. The methods used in this study include: a comprehensive literature review, field observations, fault and fracture measurements to produce a general orientation, microscopic study, XRD and XRF analysis. Muscovite, albite, orthoclase, plagioclase, smectite, illite and quartz are some of the minerals present; smectization and illitization precede kaolinization in the Grahamstown area from k-feldspar and feldspar by leaching of elements such as K, Na and Ca and concentration of Al that later combines with Si to produce kaolin. A fresh tillite has higher intensity in peak diffraction analysis than a less and more weathered rock at a certain angle 2 theta. It is concluded that the primary source rock that is the parent rock in the genesis of kaolin is the Dwyka tillite, this tillite comprises breccias of granite and quartzite having microfractures that contribute to the alteration of feldspathic materials into kaolin.

  17. Thermoluminescent characteristics of oregano and paprika

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Z, E.; Furetta, C.; Teuffer Z, C. [ICN-UNAM, A.P. 70-543, 04510 Mexico D.F. (Mexico); Melendrez, R.; Barboza F, M. [Universidad de Sonora, A.P. 5-88, Hermosillo, Sonora (Mexico); Kitis, G. [Nuclear Physics Laboratory, Aristotle University of Thessaloniki, 54006 Thessaloniki (Greece)


    The poly minerals from oregano and paprika were selected according to different sizes, i.e 10, 53, 74, 149 {mu}m, and they were exposed to ionizing gamma radiation in the range of doses 0.5-45 kGy. The glow curves from these spices show an abroad TL band, centered around 150 C and by XRD analysis shows a mono mineral composition mainly quartz and feldspar, including albite, ortose and clay. The fading behavior was related to the quartz, feldspar and calcite TL properties and shown the stability of the traps associated to the defects generated by irradiation in the samples. The tendency of the TL integrated was increased with the grain size for oregano and can be related to the different energy values associated to the activation energy of the traps in the monominerals. The glow curve TL from poly minerals was analyzed and it is possible to use the dosimetric property of the poly minerals from spices for detect irradiated foodstuffs. (Author)

  18. Determination of Optimum Process Conditions for Sulfuric Acid Dissolution of Zarigan Thorium-Uranium Ore Using Taguchi Method

    International Nuclear Information System (INIS)

    This paper deals with the study of digestion and leaching process effectiveness in thorium minerals processing, and determining the optimum process conditions for acidic leaching of thorium- uranium ores in Zarigan region to dissolve thorium. To do this, some samples from Zarigan region were studied mineralogically in laboratory. The sample containing minerals such as Anorthite, Quartz, Sanidine, Vermiculite, Albite, Gypsum, Muscovite, Anatase and Magnetite were ground in specified dimensions and then mixed with concentrated sulfuric acid. Then the mixture was heated to a high temperature. After diluting the mixture with water, it was dissolved by means of agitation leaching. The effects of different parameters such as particle size, temperature and time of digestion, concentration of sulfuric acid, and acid to ore ratio, with the aim of determining their optimum value, were studied which resulted in the following optimum values for the above-mentioned parameters: particle size of 250 μm, temperature of 180degreeC, time of 5h, concentration of sulfuric acid of 10.8 mol/lit, and acid to ore ratio of 3. Under these conditions, maximum recovery of thorium was 92%. Nitric acid (oxidant) concentration effect on the recovery of thorium in the optimum conditions was studied, and for the 2M of nitric acid concentration, thorium recovery of 97% was obtained.

  19. Metallogenetic modeling for uranium exploration in rocks of the Abaira-Jussiape Anticlinal nucleus, Chapada Diamantina, Bahia; Modelagem metalogenetica para prospeccao de uranio nas rochas do nucleo da Anticlinal Abaira-Jussiape, Chapada Diamantina, Bahia

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Jocilene dos Santos; Cruz, Simone Cerqueira Pereira; Barbosa, Johildo Salomao Figueiredo [Universidade Federal da Bahia (PPGG/UFBA), Salvador, BA (Brazil); Abram, Maisa Bastos; Martins, Adriano Alberto Marques, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Companhia de Pesquisas de Recursos Minerais (CPRM), Salvador, BA (Brazil). Superintendencia Regional de Salvador. Servico Geologico do Brasil


    The NNW-SSE-trending Abaira-Jussiape Anticlinal is an antiformal culmination of folding and shearing in the Paramirim Corridor of the Western Chapada Diamantina. In its core paleoproterozoic, mylonitized Caraguatai Suite, tonalites-granodiorites, alkali-feldspar granites, syenites to quartz-syenites and Jussiape Suite granites crop out. Compressional and distensional stresses mark the structural geology of the area. The compressional structures are related to two distinct deformation phases, named D1a and D1b. The main compressional phase is ductile D1a, which is related to the nucleation of dextral to dextral-reverse shearing zones. Deformation and syn-D1a recrystallization involving plagioclase and the K-feldspar suggest deformation temperature conditions above 550 deg C. The following phase D2 is of ductilebrittle nature and culminates in reverse shearing zones. The distensional structures correspond to the D3 phase and are represented by frontal shear zones with normal movement. The petrographic study helped identify a pre-D1a hydrothermal alteration process related to albitization and potassification, syn-D1 oxidation process, and hydration and saussuritization related to phases D2 and D3. The integration of lithological, petrographic, structural and geophysical data by means of the logic Fuzzy, plus the existing information regarding structural and lithologic controls of the known uranium mineralization in the Paramirim Corridor, led us to identify two promising areas for radioactive element exploration in the nucleus of Abaira-Jussiape Anticlinal. (author)

  20. On the geology of the uranium mineralization in the Swiss Alps

    International Nuclear Information System (INIS)

    Numerous radiometric anomalies and several uranium occurrences were found in the Swiss Alps by systematic prospecting of selected areas carried out between 1957 and 1984. Most of the uranium indications lie in a rather narrow belt that follows roughly the valleys of the Rhone und of the Rhine Anterior, from Martigny onto Ilanz and extending northwards towards the Lake of Walenstadt. The uranium occurrences were found in the following geological environments: - permocarboniferous continental, variably metamorphosed series, belonging either to the formation of the 'Verrucano' or to the Penninic St. Bernhard nappe; - muscovite-chlorite-albite gneisses belonging to the pre-Westphalian basement of the St. Bernhard nappe; - muscovite-chlorite gneisses and phyllites of the Hercynian Tavetsch massiv; - muscovite-biotite gneisses within the southern border of the Aar massif; - Vallorcine granite of the Auguilles-Rouges massiv and polymetamorphic biotite gneisses along its northwestern contact zone. The possible geological (or 'in situ') resources are estimated to be 50-250 tonnes uranium in each one of the investigated mineralization zones of some importance; the respective estimated grades are 50-250 ppm U. Therefore the occurrences are actually of no economic value. (author) 25 figs., 1 tab., refs

  1. Characterization of rock samples localized in some sites of the Mexican Pacific coast

    International Nuclear Information System (INIS)

    Geophysical studies in zones of high seismicity have showed differences in the content of radioactive material that is used in the study of the geochemical behavior of the subsoil. In an emanometric mapping of radon in soil realized in the Mexican Pacific coast were finding distinct levels in zones with different lithology. With the finality to know the mineralization types in two zones of study which are localized in the Guerrero coast and they belonging to terrains named Guerrero and Xolapa it was determined the mineralogic characteristics in two types of rocks. The identification of the rocks was realized by X-ray diffraction and was determined the elemental chemical composition using a scanning electron microscope. It was indicated in the results obtained that in the two types of rocks were found minerals such as: quartz, albite, microcline anortite, ferroactinolite and biotite. However, it was found differences between them by the presence of their mineralogic compounds because in the rock belonging to Xolapa terrain were presented whereas in the rock localized in the Guerrero terrain were presented sodic and potassic feldspars. The analysis by the Elemental Chemical Composition technique (Energy Dispersive Spectroscopy) corroborated the results obtained by the X-ray diffraction technique. (Author)

  2. Geothermal System as the Cause of the 1979 Landslide Tsunami in Lembata Island, Indonesia

    Directory of Open Access Journals (Sweden)

    Yudhicara Yudhicara


    Full Text Available DOI:10.17014/ijog.2.2.91-99A tsunami landslide which caused hundreds casualties and lots of damage took place on Lembata Island in 1979. In order to understand the characteristics of the landslide mechanism, a field survey was conducted in 2013 which sampled both the origin soil and landslide material, and the water from hotspring around the landslide site. The physical properties of the soil obtained show that the original soil has dominantly coarser grain than the landslide material (80.5% coarser grain compared to 11.8% coarse grain respectively which indicates that the soil has become finer and softer. Hot spring analysis indicated that the mineral content of the water was 99.48% SO4. This shows that magmatism processes are involved which caused the soil to become acidic and may have fragilised the system. Results of X-ray Diffraction Mineralogy Analysis (XRD show that the original soil is composed of minerals of cristobalite, quartz, and albite, while the landslide material consists of clay minerals such as quartz, saponite, chabazite, silicon oxide, and coesite which are typical minerals in a hydrothermal environment. Based on these results, it can be concluded that the area was influenced by an active geothermal system that could be the main source mechanism behind this disastrous event. 

  3. Process optimization of reaction of acid leaching residue of asbestos tailing and sodium hydroxide aqueous solution

    Institute of Scientific and Technical Information of China (English)


    Silica is the major component of the acid leaching residue of asbestos tailing. The waterglass solution can be prepared by the reaction of the residue with sodium hydroxide aqueous solution. Compared to the high temperature reaction method, this process is environmental friendly and low cost. In this paper, the reaction process of the residue and the sodium hydroxide aqueous solution is optimized. The optimum reaction process parameters are as follows: the usage of sodium hydroxide is 26.4 g/100 g acid leaching residue, the reaction temperature is 90℃, the reaction time is 1 h, and the ratio of the liquid/solid is 2.0. The significance sequence of the process parameters to the alkali leaching reaction effect is the usage of sodium hydroxide > the ratio of the liquid/solid > the reaction time > the reaction temperature. The significance sequence to the leaching ratio of SiO2 is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. The significance sequence to the modulus of the sodium silicate is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. Under the optimum conditions, the leaching ratio of the SiO2 is 77.5%, and the modulus of the sodium silicate is 3.15. The XRD analysis result indicates that the major components of the alkali leaching residue are serpentine, talc, quartz and some albite.

  4. A Preliminary Study on the Evolutionary Characteristics of Rare Earth Elements (REE)in Granitoid Rocks and Their Formation Mechanisms in Xianghualing Region,Hunan Province,China

    Institute of Scientific and Technical Information of China (English)

    杜绍华; 邱瑞照


    Recognized in the Xianghualing region,South Hunan are three major types of granitoids,i.e.,biotite granite,zinnwaldite-albite granite and xianghuagite,which evolved form the same granitic magma,but were formed at different stages.These granitoid rocks constitute a complete magmatic evolutionary series.With the evolution of magma,REE contents and negative Eu anomalies tend to decrease progressively,and LREE become more and more enriched relative to HREE .The facts mentioned above show that the tendency of REE evolution in granitoid rocks in the region studied is different from that in other regions.Evidence indicates that the granitic magma system became more and more depleted in Si(K+Na),but richer and richer in Al,Li,F and H2O+ during the process of its evolution,re-sulting in relatively weak acidity and strong alkalinity .It may be the most important factor leading to a specific REE evolutionary trend for the granitoid rocks in this region.In addition,the changing oxidation-reduction environments at different evolutionary stages of this magma system may be anoth-er important factor which should be taken into consideration.

  5. Hydrogeochemical tracing of mineral water in Jingyu County, Northeast China. (United States)

    Yan, Baizhong; Xiao, Changlai; Liang, Xiujuan; Wu, Shili


    The east Jilin Province in China, Jingyu County has been explored as a potential for enriching mineral water. In order to assess the water quality and quantity, it is of crucial importance to investigate the origin of the mineral water and its flow paths. In this study, eighteen mineral springs were sampled in May and September of 2012, May and September of 2013, and May 2014 and the environment, evolvement, and reaction mechanism of mineral water formation were analysed by hydrochemical data analysis, geochemical modelling and multivariate statistical analysis. The results showed that the investigated mineral water was rich in calcium, magnesium, potassium, sodium, bicarbonate, chloride, sulphate, fluoride, nitrate, total iron, silicate, and strontium, and mineral water ages ranged from 11.0 to more than 61.0 years. The U-shape contours of the mineral ages indicate a local and discrete recharge. The mineral compositions of the rocks were olivine, potassium feldspar, pyroxene, albite, and anorthite and were under-saturated in the mineral water. The origin of mineral water was from the hydrolysis of basalt minerals under a neutral to slightly alkaline and CO2-rich environment. PMID:26040975

  6. A survey of lunar rock types and comparison of the crusts of earth and moon (United States)

    Wood, J. A.


    The principal known types of lunar rocks are briefly reviewed, and their chemical relationships discussed. In the suite of low-KREEP highland rocks, Fe/(Fe + Mg) in the normative mafic minerals increases and the albite content of normative plagio-clase decreases as the total amount of normative plagioclase increases, the opposite of the trend predicted by the Bowen reaction principle. The distribution of compositions of rocks from terrestrial layered mafic intrusives is substantially different: here the analyses fall in several discrete clusters (anorthositic rocks, norites, granophyres and ferrogabbros, ultramafics), and the chemical trends noted above are not reproduced. It is suggested that the observed trends in lunar highland rocks could be produced by crystal fractionation in a deep global surface magma system if (1) plagiociase tended to float, upon crystallization, and (2) the magma was kept agitated and well mixed (probably by thermal convection) until crystallization was far advanced and relatively little residual liquid was left. After the crustal system solidified, but before extensive cooling had developed a thick, strong lithosphere, mantle convection was able to draw portions of the lunar anorthositic crust down into the mantle.

  7. The geomicrobiology of bauxite deposits

    Institute of Scientific and Technical Information of China (English)

    Xiluo Hao; Kwunlun Leung; Rucheng Wang; Weidong Sun; Yiliang Li


    Bauxite deposits are studied because of their economic value and because they play an important role in the study of paleoclimate and paleogeography of continents. They provide a rare record of the weathering and evolution of continental surfaces. Geomicrobiological analysis makes it possible to verify that microorganisms have played a critical role during the formation of bauxite with the possibility already intimated in previous studies. Ambient temperature, abundance of water, organic carbon and bioavailable iron and other metal substrates provide a suitable environment for microbes to inhabit. Thiobacillus, Leptospirilum, Thermophilic bacteria and Heterotrophs have been shown to be able to oxidize ferrous iron and to reduce sulfate-generating sulfuric acid, which can accelerate the weathering of aluminosilicates and precipitation of iron oxyhydroxides. Microorganisms referred to the genus Bacillus can mediate the release of alkaline metals. Although the dissimilatory iron-reducing and sulfate-reducing bacteria in bauxites have not yet been identified, some recorded authigenic carbonates and "bacteriopyrites" that appear to be unique in morphology and grain size might record microbial activity. Typical bauxite minerals such as gibbsite, kaolinite, covellite, galena, pyrite, zircon, calcium ptagioclase, orthoclase, and albite have been investigated as part of an analysis of microbial mediation. The paleoecologyof such bauxitic microorganisms inhabiting continental (sub) surfaces, revealed through geomicrobiological analysis, will add a further dimension to paleoclimatic and paleoenvironmental studies.

  8. Properties of ceramics prepared using dry discharged waste to energy bottom ash dust. (United States)

    Bourtsalas, Athanasios; Vandeperre, Luc; Grimes, Sue; Themelis, Nicolas; Koralewska, Ralf; Cheeseman, Chris


    The fine dust of incinerator bottom ash generated from dry discharge systems can be transformed into an inert material suitable for the production of hard, dense ceramics. Processing involves the addition of glass, ball milling and calcining to remove volatile components from the incinerator bottom ash. This transforms the major crystalline phases present in fine incinerator bottom ash dust from quartz (SiO(2)), calcite (CaCO(3)), gehlenite (Ca(2)Al(2)SiO(7)) and hematite (Fe(2)O(3)), to the pyroxene group minerals diopside (CaMgSi(2)O(6)), clinoenstatite (MgSi(2)O(6)), wollastonite (CaSiO(3)) together with some albite (NaAlSi(3)O(8)) and andradite (Ca(3)Fe(2)Si(3)O(12)). Processed powders show minimal leaching and can be pressed and sintered to form dense (>2.5 g cm(-3)), hard ceramics that exhibit low firing shrinkage (zero water absorption. The research demonstrates the potential to beneficially up-cycle the fine incinerator bottom ash dust from dry discharge technology into a raw material suitable for the production of ceramic tiles that have potential for use in a range of industrial applications. PMID:26060195

  9. Sludge granulation and efficiency of phase separator in UASB reactor treating combined industrial effluent

    Institute of Scientific and Technical Information of China (English)

    Abdullah Yasar; Nasir Ahmad; Muhammad Nawaz Chaudhry; Aamir Amanat Ali Khan


    Sludge granulation and the effect of gas-liquid-solid separator (GLSS) design on the efficiency of upflow anaerobic sludge blanket (UASB) and upflow anaerobic sludge filter (UASF) reactors, operating at HRTs ranging from 3 to 12 h was investigated. VSS/TS ratio gradually increased in both the reactors with increasing sludge age (from 0.5 to more than 0.7 for UASB reactor and 0.012 to 0.043 for UASF reactor). X-Ray diffraction analysis of the UASF sludge showed the presence of expanding clays revealing its additional absorption capability. Fuoraphyllite and albite precipitation related to excellular polymers of the microbial shell structure, showed the extended growth of microorganisms during sludge granulation. A gradual decrease (82%-69%) in COD removal with decreasing HRT was apparent in UASF reactor. In case of UASB reactor, this decrease was marginal because addition of GLSS device significantly improved (14%-20%) the overall efficiency of the UASB reactor. GLSS enhanced the efficiency of the UASB reactor by increasing the settleability of suspended particles and accelerating the coagulation of colloidal particles due to the velocity gradient.

  10. Trace elements in feldspars and micas in granite pegmatites from northern Minas Gerais

    International Nuclear Information System (INIS)

    A contribution to the geochemistry of granite pegmatites in Minas Gerais, Brazil is presented. Special emphasis is given to trace element contents in feldspars and muscovites of 25 different pegmatites and their geochemical significance. 180 potassium feldspars 110 albites and 64 muscovites have been analized. It could be demonstrated, that the trace element distributions in feldspars taken along cross-sections through some pegmatite bodies, show some regularities in those, which have a relatively simple mineralization. Other ones with a more complex composition are more characterize by a lack of these conformities. Potassium feldspars from pegmatites with a significant phosphate compound, on the average include more than 0.30% P2O5. Those of pegmatites with an extend Li-admixture contain more than 90 ppm Li. These observations may be useful to help classificate little known pegmatites in respect to economical purposes. Late formed muscovites from highly differenciated pegmatites contain beyond others - increased contents of Zn and Ga. This, too, may be a useful indicator to the further discovery of these kind of pegmatites, mostly enriched in minerals of economic interest. (Author)

  11. Early Paleozoic blueschist from the schist of Skookum Gulch, eastern Klamath Mountains, northern California

    Energy Technology Data Exchange (ETDEWEB)

    Cotkin, S.J. (Univ. of Arkansas, Fayetteville (United States)); Cotkin, M.L. (Univ. of Wisconsin, Madison (United States)); Armstrong, R.L. (Univ. of British Columbia, Vancouver (Canada))


    Late Ordovician blueschist from the schist of Skookum Gulch, eastern Klamath Mountains, California, is the oldest known blueschist in California and one of the oldest in North America. Lawsonite-bearing glaucophane schist occurs as lenses intimately interlayered with chlorite schist, quartz-albite schist, and dolomite marble. Detailed investigation of a portion of the Skookum Gulch schist demonstrates that these rock types share a common deformational and metamorphic history. The first deformation occurred during blueschist metamorphism and produced similar-style isoclinal folds and an axial-planar foliation. During subsequent deformations, parallel-style open to tight folds and local kink bands deformed foliation but produced no recognizable recrystallization. A phengite Rb-Sr date of 447 {plus minus} 9 Ma (Late Ordovician) is statistically indistinguishable from previously published K-Ar dates and is interpreted as the time of blueschist-facies metamorphism. Mineral separates from one rock yield a date of 353 {plus minus} 18 Ma, suggesting resetting during a Devonian to Early Mississippian thermal event. The schist of Skookum Gulch is a critical component of the Middle Ordovician to Early Silurian Callahan event, which included volcanism, plutonism, metamorphism, deformation, and sedimentation and occurred in response to collisional tectonics. Paleontological and provenance information indicate that the Callahan event occurred relatively close to the North American continental margin. In this regard, features produced by the Callahan event record the earliest period of Phanerozoic plate convergence recognized within the US Cordillera.

  12. Inherited igneous zircons in jadeitite predate high-pressure metamorphism and jadeitite formation in the Jagua Clara serpentinite mélange of the Rio San Juan Complex (Dominican Republic) (United States)

    Hertwig, Andreas; McClelland, William C.; Kitajima, Kouki; Schertl, Hans-Peter; Maresch, Walter V.; Stanek, Klaus; Valley, John W.; Sergeev, Sergey A.


    This study utilizes zircon SIMS U-Pb dating, REE and trace-element analysis as well as oxygen isotope ratios of zircon to distinguish jadeite-rich rocks that formed by direct crystallization from a hydrous fluid from those that represent products of a metasomatic replacement process. Zircon was separated from a concordant jadeitite layer and its blueschist host, as well as from loose blocks of albite-jadeite rock and jadeitite that were all collected from the Jagua Clara serpentinite-matrix mélange in the northern Dominican Republic. In the concordant jadeitite layer, three groups of zircon domains were distinguished based on both age as well as geochemical and oxygen isotope values: age groups old (117.1 ± 0.9 Ma), intermediate (three dates: 90.6, 97.3, 106.0 Ma) and young (77.6 ± 1.3 Ma). Zircon populations from the blueschist host as well as the other three jadeite-rich samples generally match zircon domains of the old age group in age as well as geochemistry and oxygen isotope ratios. Moreover, these older zircon populations are indistinguishable from zircon typical of igneous oceanic crust and hence are probably inherited from igneous protoliths of the jadeite-rich rocks. Therefore, the results suggest that all investigated jadeite-rich rocks were formed by a metasomatic replacement process. The younger domains might signal actual ages of jadeitite formation, but there is no unequivocal proof for coeval zircon-jadeite growth.

  13. Mineralogy and paragenesis of the McAllister Sn-Ta-bearing pegmatite, Coosa County, Alabama (United States)

    Foord, Eugene E.; Cook, Robert B.


    The McAllister Sn-Ta deposit (Alabama) is localized in a complex pegmatite that contains large zones of mineralized late-stage replacement-type saccharoidal albite and nearly monomineralic muscovite 'greisen-like' pipes. The dyke is at least 450 m long and averages approximately 9 m in thickness. At least two 'greisen-like' pipes, as much as 7.6 m by 4.5 m in cross-section and extending at least 76 m down a steep easterly pitch, occur near the center of the dyke. The dyke is hosted by an approximately 300-Ma-old pluton of a group referred to as the Rockford Granite, a mesozonal to epizonal two-mica, peraluminous tin-bearing granite. The pluton is genetically affiliated with a well-defined sequence of simple to complex pegmatite dykes and quartz-casiterite veins that occur near its margin and within the immediately adjacent metasedimentary rocks of the Wedowee Group.

  14. A tin-mineralized topaz rhyolite dike with coeval topaz granite enclaves at Qiguling in the Qitianling tin district, southern China (United States)

    Xie, Lei; Wang, Rucheng; Chen, Jun; Zhu, Jinchu; Zhang, Wenlan; Lu, Jianjun; Zhang, Rongqing


    The Qiguling topaz rhyolite is present as a dike within the Qitianling biotite granite batholith of the Nanling Range of southern China. Here, the rhyolitic dike, 4.5 m wide and 500 m long, contains enclaves of topaz granite. These rhyolites contain up to 72 wt.% SiO2, have alumina saturation index (ASI) > 1.1, and have groundmasses with estimated fluorine contents of approximately 1.5 wt.%. Textural relationships provide evidence of a quenched silicate melt that contains quartz, K-feldspar, albite, and zinnwaldite phenocrysts in a groundmass containing abundant topaz. The rhyolites in the study area are also strongly enriched in tin (90-2700 ppm), and generally have a close association between cassiterite and zinnwaldite, although cassiterite is also present as sponge-textured fills between rock-forming minerals. Granite enclaves and their hosted rhyolite have similar major geochemical compositions and mineralogies to each other. Zircon U-Pb dating indicates that the topaz rhyolite (147-150 Ma) and topaz granite enclaves (154 Ma) were formed contemporaneously, with ages that overlap within analytical uncertainty. In addition, the major and trace element compositions of the rhyolite and their granite enclaves are dissimilar to those of the hosting Qitianling biotite granite. This discovery of granite enclaves within rhyolite dikes suggests the presence of a topaz-bearing granite body at depth that may host tin mineralization. The expected hidden tin granite may be of great interest in the further exploration.

  15. Geochemical features of the geothermal fluids from the Mapamyum non-volcanic geothermal system (Western Tibet, China) (United States)

    Wang, Peng; Chen, Xiaohong; Shen, Licheng; Wu, Kunyu; Huang, Mingzhi; Xiao, Qiong


    Mapamyum geothermal field (MGF) in western Tibet is one of largest geothermal areas characterized by the occurrence of hydrothermal explosions on the Tibetan Plateau. The geochemical properties of hydrothermal water in the MGF system were investigated to trace the origin of the solutes and to determine the equilibrium temperatures of the feeding reservoir. The study results show that the geochemistry of hydrothermal waters in the MGF system is mainly of the Na-HCO3 type. The chemical components of hydrothermal waters are mainly derived from the minerals in the host rocks (e.g., K-feldspar, albite, Ca-montmorillonite, and Mg-montmorillonite). The hydrothermal waters are slightly supersaturated or undersaturated with respect to aragonite, calcite, dolomite, chalcedony and quartz (saturation indices close to 0), but are highly undersaturated with respect to gypsum and anhydrite (saturation indices acts as the water source of the geothermal waters. An ~ 220 °C equilibrated reservoir temperature of hydrothermal spring waters was calculated via both the Na-K-Mg ternary diagrams and the cationic chemical geothermometers. The logpCO2 of hydrothermal waters in the MGF system ranges from - 2.59 to - 0.57 and δ13C of the total dissolved inorganic carbon ranges from - 5.53‰ to - 0.94‰, suggesting that the carrier CO2 in hydrothermal water are mainly of a magmatic or metamorphic CO2 origin.

  16. Copper-gold endoskarns and high-Mg monzodiorite-tonalite intrusions at Mt. Shea, Kalgoorlie, Australia: implications for the origin of gold-pyrite-tennantite mineralization in the Golden Mile (United States)

    Mueller, Andreas G.


    Five Cu-Au epidote skarns are associated with the Mt. Shea intrusive complex, located in the 2.7-2.6 Ga Eastern Goldfields Province of the Archean Yilgarn craton, in greenstones bounded by the Boulder Lefroy and Golden Mile strike-slip faults, which control the Golden Mile (1,435 t Au) at Kalgoorlie and smaller “orogenic” gold deposits at Kambalda. The Cu-Au deposits studied are oxidized endoskarns replacing faulted and fractured quartz monzodiorite-granodiorite. The orebodies are up to 140 m long and 40 m thick. Typical grades are 0.5% Cu and 0.3 g/t Au although parts are richer in gold (1.5-4.5 g/t). At the Hannan South mine, the skarns consist of epidote, calcite, chlorite, magnetite (5-15%), and minor quartz, muscovite, and microcline. Gangue and magnetite are in equilibrium contact with pyrite and chalcopyrite. The As-Co-Ni-bearing pyrite contains inclusions of hematite, gold, and electrum and is intergrown with cobaltite and Cu-Pb-Bi sulfides. At the Shea prospect, massive, net-textured, and breccia skarns are composed of multistage epidote, actinolite, albite, magnetite (5%), and minor biotite, calcite, and quartz. Gangue and magnetite are in equilibrium with Co-Ni pyrite and chalcopyrite. Mineral-pair thermometry, mass-balance calculations, and stable-isotope data (pyrite δ34SCDT = 2.5‰, calcite δ13CPDB = -5.3‰, and δ18OSMOW = 12.9‰) indicate that the Cu-Au skarns formed at 500 ± 50°C by intense Ca-Fe-CO2-S metasomatism from fluids marked by an igneous isotope signature. The Mt. Shea stock-dike-sill complex postdates the regional D1 folding and metamorphism and the main phase of D2 strike-slip faulting. The suite is calc-akaline and comprises hornblende-plagioclase monzodiorite, quartz monzodiorite, granodiorite, and quartz-plagioclase tonalite porphyry. The intrusions display a wide range in silica content (53-73 wt% SiO2), in {{{Mg}}} {{{Mg}} + {{Fe}}_{{{{TOTAL}}}} } ratio (0.37-0.89), and in {{K}} {{{K}} + {{Na}}} )}} ratio (0

  17. Groundwater in granitic rocks

    International Nuclear Information System (INIS)

    A comparison of published chemical analyses of ground waters found in granitic rocks from a variety of locations shows that their compositions fall into two distinct classes. Ground waters from shallow wells and springs have a high bicarbonate/chloride ratio resulting from the neutralization of carbonic acid (dissolved CO2) by weathering reactions. The sodium, potassium, and silica released by weathering reactions drive the solutions away from equilibrium with the dominant minerals in the granites (i.e., quartz, muscovite, potassium feldspar, and albite). On the other hand, ground waters from deep wells and excavations are rich in chloride relative to bicarbonate. Their Na, K, H, and silica activities indicate that they are nearly equilibrated with the granite minerals suggesting a very long residence time in the host rock. These observations furnish the basis for a powerful tool to aid in selecting sites for radioactive waste disposal in granitic rocks. When water-bearing fractures are encountered in these rocks, a chemical analysis of the solutions contained within the fracture can determine whether the water came from the surface, i.e., is bicarbonate rich and not equilibrated, or whether it is some sort of connate water that has resided in the rock for a long period, i.e., chloride rich and equilibrated. This technique should allow immediate recognition of fracture systems in granitic radioactive waste repositories that would allow radionuclides to escape to the surface

  18. Towards a Model for Albitite-Type Uranium

    Directory of Open Access Journals (Sweden)

    Andy Wilde


    Full Text Available Albitite-type uranium deposits are widely distributed, usually of low grade (<1% U3O8, but are often large and collectively contain over 1 million tonnes of U3O8. Uranium is hosted in a wide range of metamorphic lithologies, whose only common characteristic is that they have been extensively mylonitised. Ore minerals are disseminated and rarely in megascopic veins, within and adjacent to albitised mylonites. Grain size is uniformly fine, generally less than 50 microns. Scanning electron microscopy reveals that spatial association between uranium and various Ti-bearing phases is common. Gangue minerals include albite, carbonates (calcite and dolomite, and sodic pyroxene and amphibole. The ore rarely contains economic metals apart from uranium, phosphorous at Itataia being an exception. There is widespread evidence of hydrothermal zirconium mobility and hydrothermal zircon and other Zr phases are frequent and in some cases abundant gangue minerals. Positive correlations are noted between uranium and various high field strength elements. The group remains poorly described and understood, but a link to iron-oxide copper-gold (IOCG deposits and/or carbonatite and/or alkaline magmatism is plausible.

  19. Study on the enhancement of hydrocarbon recovery by characterization of the reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Tae-Jin; Kwak, Young-Hoon; Huh, Dae-Gee [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)


    The reservoir geochemistry is to understand the origin of these heterogeneities and distributions of the bitumens within the reservoir and to use them not only for exploration but for the development of the petroleums. Methods and principles of the reservoir geochemistry, which are applicable to the petroleum exploration and development, are reviewed in the study. In addition, a case study was carried out on the gas, condensate, water and bitumen samples in the reservoir, taken from the Haenam, Pohang areas and the Ulleung Basin offshore Korea. Mineral geothermometers were studied to estimate the thermal history in sedimentary basins and successfully applied to the Korean onshore and offshore basins. The opal silica-to-quartz transformation was investigated in the Pohang basin as a geothermometer. In Korean basins, the smectite-to-illite changes indicate that smectite and illite can act as the geothermometer to estimate the thermal history of the basins. The albitization reaction was also considered as a temperature indicator. Naturally fractured reservoir is an important source of oil and gas throughout the world. The properties of matrix and fracture are the key parameters in predicting the performances of naturally fractured reservoirs. A new laboratory equipment has been designed and constructed by pressure pulse method to determine the properties, which are (1) the porosity of matrix, (2) the permeability of matrix, (3) the effective width of the fractures, and the permeability of the fractures. (author). 97 refs.

  20. Silicate-salt(sulfate) liquid immiscibility: a study of melt inclusions in minerals of the Mushugai-Khuduk carbonatite-bearing complex ( southern Mongolia )%硅酸盐-盐(硫酸盐)流体不混溶:蒙古南部Mushugai-Khuduk含火成碳酸岩杂岩体矿物中的熔体包裹体研究

    Institute of Scientific and Technical Information of China (English)

    Irina A.Andreeva; Vyacheslav I.Kovalenko; Vladimir B.Naumov


    Crystalline and melt inclusions were studied in garnet, diopside, potassium feldspar, and sphene from the garnet syenite porphyry of the carbonatite-bearing complex Mushugai-Khuduk, southern Mongolia. Phlogopite, clinopyroxene, albite, potassium feldspar, sphene, wollastonite, magnetite, Ca and Sr sulfates, fluorite, and apatite were identified among the crystalline inclusions.The melt inclusions were homogenized at 1010 ~ 1080℃ and analyzed on an electron microprobe. Silicate, salt, and combined silicatesalt melt inclusions were found. Silicate melts show considerable variations in SiO2 concentration (56 to 66wt% ), high Na2O + K2O(up to 17wt% ), and elevated Zr, F, and Cl contents. In terms of bulk rock chemistry, the silicate melts are alkali syenites. During thermometric experiments, salt melt inclusions quenched into homogeneous glasses of predominantly sulfate compositions containing no more than 1.3wt% SiO2. These melts are enriched in alkalis, Ba, Sr, P, F, and Cl. The investigation of the silicate and salt melt inclusions in minerals of the garnet syenite porphyries indicate that these rocks were formed under influence of the processes of crystallization differentiation and magma separation into immiscible silicate and salt (sulfate)liquids.

  1. Minerals of a soil developed in the meteoritic crater of Carancas, Peru, and evidences of phase changes on the impact event (United States)

    Loayza, María L. Cerón; Cabrejos, Jorge A. Bravo


    We report studies about the phase transformations in the soil of the Carancas meteoritic crater located in an inhabited area near the town of Carancas, in the Region of Puno, about 1,300 km southeast of Lima, Peru. The studies by energy dispersive X-ray fluorescence, X-ray diffractometry and transmission Mössbauer spectroscopy (at RT and 77 K) reveal that the sample consists mainly of quartz, albite and impactites such as coesite and stishovite (SiO2) that have experienced phase metamorphism or alterations, related to high pressures and temperatures, forming their corresponding polymorphs. The occurrence of these phases, with high content of SiO2, in the soil of the crater strengthens the hypothesis of its origin by metamorphism induced by impact; we observed also a magnetic sextet on the Mössbauer pattern, assigned to the Fe3 + in hematite, and three paramagnetic doublets, two of them associated with structural Fe3 + and Fe2 + cations, respectively, in illite and/or montmorillonite, and a third one due to an unidentified Fe3 + site.

  2. A test of the 40Ar/39Ar age spectrum technique on some terrestrial materials (United States)

    Lanphere, M.A.; Brent, Dalrymple G.


    40Ar/39Ar age spectra were determined for 10 terrestrial rock and mineral samples whose geologic history is known from independent evidence. The spectra for six mineral and whole rock samples, including biotite, feldspar, hornblende, muscovite, and granodiorite, that have experienced post-crystallization heating did not reveal the age of crystallization in any obvious way. Minima in the spectra, however, give reasonable maximum ages for reheating and high-temperature maxima can be interpreted as minimum crystallization ages. High-temperature ages of microcline and albite that have not been reheated are approximately 10% younger than the known crystallization age. Apparently there are no domains in these feldspars that have retained radiogenic 40Ar quantitatively. Spectra from two diabase samples that contain significant quantities of excess argon might mistakenly be interpreted as spectra from reheated samples and do not give the age of emplacement. The 40Ar/39Ar age spectrum technique may be a potentially valuable tool for the study of geologic areas with complex histories, but the interpretation of age spectra from terrestrial samples seems to be more difficult than suggested by some previous studies. ?? 1971.

  3. Using presence of calcite cap rock in shales to predict occurrence of reservoirs composed of leached secondary porosity in the geopressured zone. Annual report, June 1, 1980-October 31, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, W.R.; Magara, K.; Milliken, K.L.; Richmann, D.L.


    The distribution of high-resistivity shale in the Frio Formation between hydropressured and geopressured strata has been mapped along the Texas Gulf Coast. Two high-resistivity intervals more than 1000 ft thick have been mapped, one in Brazoria and Galveston Counties and the other in Kenedy County. They coincide with Frio delta systems and may be related to extraordinary quantities of CO/sub 2/ produced by deltaic sediments rich in woody and herbaceous matter. Beyond being calcareous, the nature of the high-resistivity interval is enigmatic and its relationship to deep secondary porosity problematic. Most of the contained carbonate is microscopically and isotopically skeletal in origin, revealing no evidence of diagenetic modification. Minor rhombs of iron-bearing carbonate tens of microns in size were identified. Detrital feldspar compositions are being established to test subsequent changes in feldspar composition resulting from progressive burial and albitization. Hydrolysis reactions for authigenic minerals and reactions between key pairs of minerals have been written. Thermodynamic functions for complex phyllosilicates at temperatures up to 200/sup 0/C have been calculated. From thermodynamic calculations it was predicted that ferroan calcite would be the favored authigenic carbonate in shales.

  4. Rock-Forming feldspars of the Khibiny alkaline pluton, Kola Peninsula, Russia (United States)

    Ivanyuk, G. Yu.; Pakhomovsky, Ya. A.; Konopleva, N. G.; Kalashnikov, A. O.; Korchak, Yu. A.; Selivanova, E. A.; Yakovenchuk, V. N.


    This paper describes the structural-compositional zoning of the well-known Khibiny pluton in regard to rock-forming feldspars. The content of K-Na-feldspars increases inward and outward from the Main foidolite ring. The degree of coorientation of tabular K-Na-feldspar crystals sharply increases in the Main ring zone, and microcline-dominant foyaite turns into orthoclase-dominant foyaite. The composition of K-Na-feldspars in the center of the pluton and the Main ring zone is characterized by an enrichment in Al. This shift is compensated by a substitution of some K and Na with Ba (the Main ring zone) or by an addition of K and Na cations to the initially cation-deficient microcline (the central part of the pluton). Feldspars of volcanosedimentary rocks occurring as xenoliths in foyaite primarily corresponded to plagioclase An15-40, but high-temperature fenitization and formation of hornfels in the Main ring zone gave rise to the crystallization of anorthoclase subsequently transformed into orthoclase and albite due to cooling and further fenitization. Such a zoning is the result of filling the Main ring fault zone within the homogeneous foyaite pluton with a foidolite melt, which provided the heating and potassium metasomatism of foyaite and xenoliths of volcanosedimentary rocks therein. The process eventually led to the transformation of foyaite into rischorrite-lyavochorrite, while xenoliths were transformed into aluminum hornfels with anorthoclase, annite, andalusite, topaz, and sekaninaite.

  5. Phosphor plasters of CaSO4:Dy on the courtyard wall of Djehuty's tomb (Luxor, Egypt)

    International Nuclear Information System (INIS)

    The X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) analyses of plasters collected from the courtyard walls of Djehuty's tomb show anhydrite, calcite, dolomite, quartz, alkali feldspars and accessorial amounts of halite and illite. The external outer bed is mainly composed by anhydrite, since the original hydrous phases of gypsum plaster were desiccated during thirty centuries in the dry land environment of the Luxor area, under low relative humidity and high temperatures. The luminescence analyses by thermoluminescence (TL) and cathodoluminescence (CL) demonstrate as one plaster sample (m8), i.e., 95% anhydrite, displays a gigantic TL emission of 33 555 a.u. and a SEM/CL emission of 2319 a.u. maxima peak. The spectra CL also exhibits a 484 nm peak attributable to the classic 4F9/2→6H15/2 transition circa 490 nm of Dy3+ and a 573 nm emission of Dy3+ masked in a broad emission band centered at 620 nm. The common presence of sodium minerals such as halite or albite together with the probable presence of sodium in waters points to Na+ ions acting as compensators of Dy3+ to maintain the electrical neutrality of the CaSO4:Dy phosphor lattice. Further analyses of more plaster CaSO4 micro-samples could demonstrate if this observation is just an isolated mineralogical chance or an intentional archaeological handling

  6. Compositional controls on spinel clouding and garnet formation in plagioclase of olivine metagabbros, Adirondack Mountains, New York (United States)

    McLelland, J.M.; Whitney, P.R.


    Olivine metagabbros from the Adirondacks usually contain both clear and spinel-clouded plagioclase, as well as garnet. The latter occurs primarily as the outer rim of coronas surrounding olivine and pyroxene, and less commonly as lamellae or isolated grains within plagioclase. The formation of garnet and metamorphic spinel is dependent upon the anorthite content of the plagioclase. Plagioclase more sodic than An38??2 does not exhibit spinel clouding, and garnet rarely occurs in contact with plagioclase more albitic than An36??4. As a result of these compositional controls, the distribution of spinel and garnet mimics and visually enhances original igneous zoning in plagioclase. Most features of the arrangement of clear (unclouded) plagioclase, including the shells or moats of clear plagioclase which frequently occur inside the garnet rims of coronas, can be explained on the basis of igneous zoning. The form and distribution of the clear zones may also be affected by the metamorphic reactions which have produced the coronas, and by redistribution of plagioclase in response to local volume changes during metamorphism. ?? 1980 Springer-Verlag.

  7. Mössbauer spectroscopy and X-ray diffraction analyses of clayey samples used as ceramic sourcing materials, in Peru (United States)

    Quille, Rubén; Bustamante, Ángel; Palomino, Ybar


    The ceramic industry is an important area of economic activity in the Ayacucho Region, in particular in the District of Quinua. As a consequence, there is a huge demand for clay to produce ceramic pastes in that region. This paper reports on results concerning the mineralogical characterization of four clayey samples, which were collected MAA and SPQA from the area Pampa de La Quinua with geographic coordinates 13° 02' 49″ S 74° 08' 03″ W, CE1M and CE2M from the Quinua locality 13° 03' 07″ S 74° 08' 31″ W, both in the District of Quinua, Province of Huamanga, Ayacucho, Peru. The chemical and mineralogical characterization of these samples was carried out with powder X-ray diffraction detecting quartz, albite, montmorillonite, kaolinite and glauconite mineral phases, Mössbauer spectroscopy detected iron in kaolinite, glauconite and montmorillonite minerals. Chemical analysis was performed through scanning electron microscopy and energy dispersive X-ray spectroscopy. Data obtained from the combination of these techniques provided relevant information about the morphology, chemical composition, and the mineralogy of samples.

  8. Impact of depositional facies on the distribution of diagenetic alterations in the Devonian shoreface sandstone reservoirs, Southern Ghadamis Basin, Libya (United States)

    Khalifa, Muftah Ahmid; Morad, Sadoon


    The middle Devonian, shoreface quartz arenites (present-day burial depths 2833-2786 m) are important oil and gas reservoirs in the Ghadamis Basin, western Libya. This integrated petrographic and geochemical study aims to unravel the impact of depositional facies on distribution of diagenetic alterations and, consequently, related reservoir quality and heterogeneity of the sandstones. Eogenetic alterations include the formation of kaolinite, pseudomatrix, and pyrite. The mesogenetic alterations include cementation by quartz overgrowths, Fe-dolomite/ankerite, and illite, transformation of kaolinite to dickite, illitization of smectite, intergranular quartz dissolution, and stylolitization, and albitization of feldspar. The higher energy of deposition of the coarser-grained upper shoreface sandstones combined with less extensive chemical compaction and smaller amounts of quartz overgrowths account for their better primary reservoir quality compared to the finer-grained, middle-lower shoreface sandstones. The formation of kaolin in the upper and middle shoreface sandstones is attributed to a greater flux of meteoric water. More abundant quartz overgrowths in the middle and lower shoreface is attributed to a greater extent of stylolitization, which was promoted by more abundant illitic clays. This study demonstrated that linking the distribution of diagenetic alterations to depositional facies of shoreface sandstones leads to a better understanding of the impact of these alterations on the spatial and temporal variation in quality and heterogeneity of the reservoirs.

  9. Relationships among Preparative Technique,Phase Composition and Bending Strength of Bauxite Porcelain

    Institute of Scientific and Technical Information of China (English)

    REN Qiang; WU Xiu-Lan; HE Xuan-Meng; ZHU Zhen-Feng


    Bauxite porcelain can be sintered to make its bending strength reach 179Mpa by using sintered bauxite,clay and potash feldspar and albite as the main raw materials in oxidation atmosphere under the normal pressure.XRD,SEM and so on are utilized to study the relationships between factors like the composition of ingot,reduction particle size and heat insulating time at sintering temperature and the phase composition,microstructure and bending strength of ceramic body.The results show that the main phases in bauxite porcelain are corundum,mullite and glass,and the mullite is composed of two parts:primary mullite formed by clay conversion and secondary mullite whiskers precipitating from high temperature melt.The bending strength of ceramic body can be improved by enhancing the content of sintered bauxite in the formula:the smaller the particle size of the ceramic body is,the higher the bending strength will be.The high-temperature heat insulating technique is beneficial to the precipitation of certain quantitative secondary mullite whiskers so as to remarkably improve the strength of glass phase and ceramic body.

  10. Propagation of a hyperalkaline plume into the geological barrier surrounding a radioactive waste repository

    International Nuclear Information System (INIS)

    A coupled geochemical transport model (MPATH) which includes chemical reaction kinetics is used to evaluate the alteration of Swiss argillaceous sediments in a high-pH environment and to predict the spatial propagation of the hyperalkaline plume with time. The calculations predict dissolution of quartz, clay minerals and chlorite, and precipitation of zeolite minerals such as analcime and natrolite as well as he feldspars K-feldspar and albite. In addition, Portland cement-hydrates such as calcium silicate and aluminate hydrates, ettringite and friedel-salt are also predicted to form, depending on the composition of the inlet fluid and the host rock. The dissolution of clay minerals reduces the pH of the hyperalkaline plume to levels between approximately 8 and 10, depending on the composition of the inlet fluid and the host rock. For pure advective transport through porous medium, neglecting changes in porosity and permeability, the migration velocity of the high-pH front is calculated to be approximately one to two orders of magnitude less than that of the infiltrating groundwater. However, due to precipitation of secondary phases, in the present model concept a rapid decrease in porosity of the marl occurs several meters from the repository. At the interface between the marl host rock and cement the porosity increases as a consequence of the low silica concentration of the cement pore fluid. (author) 10 figs., 7 tabs., refs

  11. Studies of mineralogy and geochemistry of Rare Earth Elements in permo-Triassic Bauxite deposit, Northeast of Bukan, North West of Iran

    International Nuclear Information System (INIS)

    Bauxite deposit of Permo-Triassic age in northeast of Bukan was developed stratiformly along the boundary between Ruteh and Elika formations, and includes four distinct rock units. This deposit was affected by tectonic and morphological processes. Mineralogical and geochemical investigations showed that during weathering processes, two mechanisms of ferrugenization and deferrugenization played crucial role in formation of minerals such as Diaspora, boehmite, hematite, goethite, kaolinite, pyrophyllite, clinochlore, illite, montmorillonite, anatase, rutile, albite, sanidine, quartz, and calcite in this deposit. By taking notice of field evidence and of mineralogical and geochemical data, the basalts (whose remnants are still present along the contact of this deposit with carbonate bedrock) are the potential parent rock of this deposit. The distribution pattern of rare earth elements (normalized to chondrite and basaltic parent rock) along with anomaly variations of Eu, Ce, and (La/Yb)N indicates differentiation of LREEs from HREEs during bauxitization processes. Further geochemical considerations indicate that the concentrations of LREEs were occurred by hematite, goethite, manganese oxides, cerianite, and secondary phosphates (rhabdophane, vitusite, gorceixite, monazite) and of HREEs by clay minerals; rutile, anatase, zircon, euxenite, and fergusonite. Incorporation of the results obtained from mineralogical and geochemical investigations suggests that in addition to factors such as p H of weathering solutions, ionic potential, composition of the parent rock, and fixation by residual minerals, adsorption processes also played crucial role in enrichment of rare earth elements during moderate to intense lateritization in the study area

  12. A preliminary study of the phycological degradation of natural stone masonry. (United States)

    Welton, Ryan G; Cuthbert, Simon J; Mclean, Roger; Hursthouse, Andrew; Hughes, John


    For many years it has been realised that the weathering of stone is not merely determined by physical and chemical factors but also by biological agents. When the stone in question is a historic building or monument, the damage done constitutes an irretrievable loss of our heritage and history. Laboratory studies have commenced in Paisley to study the effect of photoautotrophs on the major sedimentary rock forming minerals, with a view to expanding this work to study the overall effect of these micro-organisms on heritage masonry. Tests were carried out on Albite, Calcite, Dolomite, Orthoclase, Siderite and Quartz, using axenic cultures of the following: Chlorella vulgaris, Chlorococcum tetrasporum, Scenedesmus obliquus, Oocystis marsonii, Stichococcus bacillaris. The rock chips were immersed in either water or bolds basal media and exposed to a mix of the micro-organisms listed above and then tested weekly for their pH, fortnightly for the waters chemical composition using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and visually utilising the university's SEM facilities. Work so far has revealed biologically mediated etching of minerals, a well-defined pH profile over a period of 90 days, as well as a variety of elemental release patterns for the different minerals. PMID:12901089

  13. Crystal dissolution kinetics and Gibbs free energy

    Energy Technology Data Exchange (ETDEWEB)

    Luettge, Andreas [Department of Earth Science and the Department of Chemistry, Center for Biological and Environmental Nanotechnology, Rice University, 6100 Main Street, Houston, TX 77005 (United States)]. E-mail:


    The dependence of dissolution rates on the difference of Gibbs free energy is of critical importance for our understanding of crystal dissolution, reactive flow models and their applications to a variety of environmentally related problems. Here, we review experimental data generated with mineral powders and single crystals to develop a better understanding of apparent inconsistencies between otherwise internally consistent data sets. Additional information from direct surface observations and measurements with vertical scanning interferometry (VSI) and atomic force microscopy (AFM) of albite dissolution at 25, 150 and 185 deg. C may shed new light on this old but unsolved question. Our discussion is based on the importance of etch pit development, its {delta}G dependence, and the pits' role as a source for steps and step movement in the dissolution process. Results indicate that reaction history may be of critical importance in determining the overall reaction mechanism and its rate. Different rates are observed for systems having otherwise identical {delta}G {sub r} acquired from increasing versus decreasing disequilibrium positions. In this context, we finally discuss the validity of the common application of transition state theory (TST) to elementary and overall reactions governing the dissolution process. In this discussion of crystal dissolution, we contrast TST applications with a stochastic, many-body treatment that has led to the development of a stepwave model. This discussion also focuses on the controversy caused by the rivalry between surface adsorption models and a probabilistic model that seeks to incorporate the full three-dimensional crystal structure.

  14. Assessment of geochemical evolution of groundwater in a mountainous area under agricultural land (United States)

    Ledesma-Ruiz, Rogelio; Pasten-Zapata, Ernesto; Parra, Roberto; Harter, Thomas; Mahlknecht, Jürgen


    Zona Citricola is an important area to Mexico for its citriculture. Situated in a sub-humid to humid climate adjacent to Sierra Madre Occidental, this mountainouos valley hosts an aquifer system which represents sequences of shales, marls, conglomerates, and alluvial deposits. Groundwater flows from mountainous recharge areas to the basin-fill deposits and provides base flow to supply drinking water to an adjacent metropolitan area. The objective of this study was to characterize groundwater chemistry of this area and to assess the evolution. Correlation and principal component analysis were used to decipher various underlying natural and anthropogenic processes creating distinct water classes: (1) dissolution of evaporates, (2) surface organic waste or wastewater, and (3) silicate weathering and clay formation. Hierarchical cluster analysis was employed for partitioning the water samples into four hydrochemical groups: recharge waters (Ca-HCO3), transition zone waters (Ca-HCO3-SO4 to Ca-SO4-HCO3) and discharge waters (Ca-SO4). Inverse geochemical models of these groups were developed using PHREEQC to elucidate the chemical reactions controlling water chemistry between an initial (recharge) and final water. The main responsible reactions were: (1) dissolution of rock salts, (2) release of soil gas carbon dioxide, (3) dedolomitization,(4) albite weathering reactions with corresponding precipitation of silica and clay minerals, and (5) input from animal/human waste and manure, accompanied by denitrification processes. The hydrochemical groups could be related to lithological formations.

  15. Mineralization Zoning in Yindongzi—Daxigou Barite—Siderite,Silver—Polymetallic Deposits in the Qinling Orogen,China

    Institute of Scientific and Technical Information of China (English)

    方维萱; 胡瑞忠; 等


    The Yindongzi-Daxigou strata-bound barite-siderite,silver-polymetallic deposits discovered in the Qinling orogen are hosted within flysch facies in a deep-water fault-controlled basin on the passive northern margin of the Qinling microplate.The orebodies occur in a series of hydrothermal depositonal rocks.Mineralization zoning is characterized by Fe-Ba←Ba-Cu←Pb-Ab→Cu-Ag→Pb→Au.This is obviously a gradational transition mineralization from ventproximal mineralization to more distal mineralization.In this gradational transition between Chefanggou and Yindongzi,vent-proximal mineralization consists of silver-polymetallic orebodies(Pb-Ag),which is the center of hydrothermal mineralization.The Chefanggou Ba-Cu ore district in the west and the Yindongzi Cu-Ag ore district in the east represent vent lateral mineralization.Distal mineralization in the west is represented by the Daxigou Fe-Ba ore district while distal mineralization in te east is represented by the Pb ore district.Thick massive,laminated barren albite chert and jasperite,sometimes with minor silver-ploymetallic mineralization of commercial importance,and pyritization in rocks feature more distal mineralization.Geochemical anomalies of Au-As associations are found in ankerite phyllite and muddy sandstone.Actually,Au deposits are dominantly controlled by the late brittle-ductile shear zone.

  16. Mineralization Zoning in Yindongzi-Daxigou Barite-Siderite, Silver-Polymetallic Deposits in the Qinling Orogen, China

    Institute of Scientific and Technical Information of China (English)

    方维萱; 胡瑞忠; 黄转莹


    The Yindongzi-Daxigou strata-bound barite-siderite, silver-polymetallic deposits discovered in the Qinling orogen are hosted within flysch facies in a deep-water fault-controlled basin on the passive northern margin of the Qinling microplate. The orebodies occur in a series of hydrothermal depositional rocks. Mineralization zoning is characterized by Fe-Ba←Ba-Cu←Pb-Ag→Cu-Ag→Pb→Au. This is obviously a gradational transition mineralization from ventproximal mineralization to more distal mineralization. In this gradational transition between Chefanggou and Yindongzi, vent-proximal mineralization consists of silver-polymetallic orebodies (Pb-Ag), which is the center of hydrothermal mineralization. The Chefanggou Ba-Cu ore district in the west and the Yindongzi Cu-Ag ore district in the east represent vent lateral mineralization. Distal mineralization in the west is represented by the Daxigou Fe-Ba ore district while distal mineralization in the east is represented by the Pb ore district. Thick massive, laminated barren albite chert and jasperite, sometimes with minor silver-ploymetallic mineralization of commercial importance, and pyritization in rocks feature more distal mineralization. Geochemical anomalies of Au-As associations are found in ankerite phyllite and muddy sandstone.Actually, Au deposits are dominantly controlled by the late brittle-ductile shear zone.


    Institute of Scientific and Technical Information of China (English)

    洪东良; 侯丹丹; 王竞秀


    三官塘铁矿位于安徽省马鞍山市,地处宁芜火山岩盆地中段,矿床成因类型为玢岩铁矿--中高温热液充填型矿床。文章通过对其成矿地质特征的分析研究认为:岩浆沿基底断裂上侵,在结晶末期发生了钠长石化、磁铁矿化等作用形成了早期的含矿热液,沿岩石裂隙和矿物颗粒间隙向岩体顶部运移,形成以浸染状为主的现今三官塘铁矿。%The Sanguantang Iron ore deposit in Ma‘anshan City, Anhui Province, in the middle part of Ningwu volcano-sedimentary basin. The Mineral genesis is porphyrite iron ore--medium-high temperature hydrothermal deposits. this paper found that Iron mineralization is control ed by diorite-porphyrite, the Magma intrusion along the basement fault,the ore-forming hydrothermal solution of the early stage migrates mainly in the form of Albite, magnetite etc In the crystal ization stage,Going to Top of the Rock Along the rock fissure and mineral particles clearance,formation main Disseminated of present-day Sanguantang Iron.

  18. Mineralogical-geochemical characteristics of the neogene sediments at the coal mine of Zhivojno in the Pelagonija depression

    International Nuclear Information System (INIS)

    This study gives a first-time detailed analysis of the mineralogical and geochemical characteristics of the Neogene sediments found at the coal mine of Zhivojno in the Pelagonija depression based on tested samples of cores recovered in the investigation of the coal series from this region. For the determination of the mineralogical composition we used the x-ray diffraction method while for the determination of the detailed geochemical characteristics we tested the presence of trace elements with the ICP-MS method. The presence of the following main mineral stages was recorded: muscovite/illite, chlorite, quartz, albite, orthoclase and epidote. The presence of these rare elements ranges from (in ppm): Mn (1684); Sr (250); Ba (598); Zn (121); Pb (36); Cr (34); Co (22); Ni (39); Cd (0.65); Cu (55); As (9.7); Li (32); V (121); Mo (2.1); Sb (1.2); Be (3); Bi (1); Ge (0.38); Sn (2.97); Ag (3.3); Ti (1.41); Rb (157); Cs (8.5); Th (15.9); U (3.93)

  19. Raman microscopy of hand stencils rock art from the Yabrai Mountain, Inner Mongolia Autonomous Region, China (United States)

    Hernanz, Antonio; Chang, Jinlong; Iriarte, Mercedes; Gavira-Vallejo, Jose M.; de Balbín-Behrmann, Rodrigo; Bueno-Ramírez, Primitiva; Maroto-Valiente, Angel


    A series of rock art pictographs in the form of hand stencils discovered in two sites of the Yabrai Mountain, Inner Mongolia Autonomous Region (China) has been studied by micro-Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X-ray spectroscopy for the first time. These studies have made possible to characterise the materials present. The minerals α-quartz, phlogopite, albite and microcline have been identified in the granitic rocks supporting the paintings. Calcite and dolomite micro-particles detected on the rock surface have been attributed to desert dust. Accretions of gypsum, anhydrite and whewellite have also been identified on the rock surface. Haematite is the pigment used in the red pictographs, whereas well-crystallised graphite has been used in the black ones. The use of crystalline graphite instead of amorphous carbon (charcoal, soot or bone black) as a black pigment in rock art is an interesting novelty. Overlapped hands are proposed as a new type of hand stencils to make an unusual pictorial symbol in rock art that has been found in these sites.

  20. Geochemistry of Rare Earth Elements (REE) in the Weathered Crusts from the Granitic Rocks in Sulawesi Island, Indonesia

    Institute of Scientific and Technical Information of China (English)

    Adi Maulana; Kotaro Yonezu; Koichiro Watanabe


    We report for the first time the geochemistry of rare earth elements (REE) in the weath-ered crusts of I-type and calc-alkaline to high-K (shoshonitic) granitic rocks at Mamasa and Palu re-gion, Sulawesi Island, Indonesia. The weathered crusts can be divided into horizon A (lateritic profile) and B (weathered horizon). Quartz, albite, kaolinite, halloysite and montmorrilonite prevail in the weathered crust. Both weathered profiles show that the total REE increased from the parent rocks to the horizon B but significantly decrease toward the upper part (horizon A). LREE are enriched toward the upper part of the profile as shown by La/YbN value. However, HREE concentrations are high in horizon B1 in Palu profile. The total REE content of the weathered crust are relatively elevated com-pared to the parent rocks, particularly in the lower part of horizon B in Mamasa profile and in horizon B2 in Palu profile. This suggests that REE-bearing accessory minerals may be resistant against weath-ering and may remain as residual phase in the weathered crusts. The normalized isocon diagram shows that the mass balance of major and REE components between each horizon in Mamasa and Palu weathering profile are different. The positive Ce anomaly in the horizon A of Mamasa profile indicated that Ce is rapidly precipitated during weathering and retain at the upper soil horizon.

  1. A room-temperature phase transition in maximum microcline - Heat capacity measurements (United States)

    Openshaw, R.E.; Hemingway, B.S.; Robie, R.A.; Krupka, K.M.


    The thermal hysteresis in heat capacity measurements recently reported (Openshaw et al., 1976) for a maximum microcline prepared from Amelia albite by fused-salt ion-exchange is described in detail. The hysteresis is characterized by two limiting and reproducible curves which differ by 1% of the measured heat capacities. The lower curve, denoted curve B, represents the values obtained before the sample had been cooled below 300 K. Measurements made immediately after cooling the sample below 250 K followed a second parallel curve, curve A, to at least 370 K. Values intermediate to the two limiting curves were also obtained. The transitions from the B to the A curve were rapid and observed to occur three times. The time required to complete the transition from the A to the B curve increased from 39 h to 102 h in the two times it was observed to occur. The hysteresis is interpreted as evidence of a phase change in microcline at 300??10 K The heat effect associated with the phase change has not been evaluated. ?? 1979 Springer-Verlag.

  2. Zircon syenite pegmatites in the Finero peridotite (Ivrea zone): evidence for a syenite from a mantle source

    International Nuclear Information System (INIS)

    Zircon syenite pegmatite dikes in the phlogopite peridotite of Finero are rich in volatiles, incompatible elements and in rare earths with (La/Yb)N ratios in the range of 14-15. The main mineral constituents in the alkaline dikes (Na>K) are albite and magnesium-rich biotites whereas nepheline, cancrinite, sodalite, zircon and apatite are minor or accessory. With their initial 87Sr/86Sr ratio of 0.70371 the non-contaminated syenite pegmatites originate from partial melts of the upper mantle. The magma is derived from a depleted mantle source with isotopic signatures (εNd(T)=5.7 and 5.1) of ocean island basalts (OIB). The ascent of the syenite pegmatites and the marginal uplift of the granulitic crust in the northern Ivrea zone may be correlated with the intrusion of alkaline melts at depth. The Triassic zircon age of 225±13 Ma is interpreted as the time of the dikes' emplacement. From geochemistry and setting it is concluded, that the syenites are related to a rift magmatic stage at the early Mesozoic in the southern Alps. (orig.)

  3. Ore-controlling Structure Characteristic and the Sources of Ore Forming Material in the Jinchangyu Gold Deposit, Hebei Province%河北金厂峪金矿控矿构造特征与成矿物质来源

    Institute of Scientific and Technical Information of China (English)

    宋扬; 王瑞江; 胡建中; 谭应佳; 石成龙; 王涛


    Jinchangyu Gold Mine is one of the largest gold deposits on the northern margin of North China Plate and occurs in the Late Archean greenstone fold belt. Two kinds of ores have been recognized: gold-bearing albite vein and gold-bearing quartz vein. tudies of ore-controlling structures show that the Jinchangyu anticlinorium and related NNE trending compressed schistosity zone, both of which resulted from two-stage regional foldings, are the main ore-controlling structure of Jinchangyu Gold Mine. In the course of schistosity and alteration, Fe2 O3, CaO, and MgO were clearly brought out from amphibolite in surrounding rocks. Albite dykes and quartz vein penetrate along the surfaces of extruding schistosity, both of which are roughly same in width, gold grade, occurrence and material source. They are probably the products of the same mineralization at different mineralization stages. Characteristics of rare earth elements, sulfur and lead isotopes show that the mineralization was related to deep magmatism and the strata remelted due to the magmatism provided part of mineralized materials. Therefore, it is concluded that the Jinchangyu Gold Mine is a magmatic and thermal-fluid-type deposit with mineralized materials collectively from remelting mantle, lower crust and partial surrounding rocks (i. e. Archaeozoic greenstone belt) under the influence of Yanshanian intracontinental orogeny during the early Mesozoic.%金厂峪金矿是我国华北板块北缘大型金矿床之一,矿床产在晚太古宙褶皱绿岩带中,矿石类型主要包括含金钠长石脉和含金石英脉两种.控矿构造研究表明,在两期区域性褶皱作用下,形成的金厂峪复背斜及与之相关的北北东向挤压片理化带是金厂峪金矿的主要控矿构造.在片理化和蚀变过程中围岩斜长角闪岩的Fe2O3、CaO、MgO等成分被明显带出,钠长石脉和石英脉沿挤压片理面贯入,二者宽度、金品位、产状、物质来源基本一致,是同一成

  4. Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, clark county, Nevada (United States)

    Vikre, P.; Browne, Q.J.; Fleck, R.; Hofstra, A.; Wooden, J.


    ore breccias and relatively low S and Pb isotope values (??34S values vary from 0-??4%; 206Pb/204Pb Pb from 1.7 Ga crystalline basement or from Late Proterozoic siliciclastic sedimentary rocks derived from 1.7 Ga crystalline basement. Four texturally and modally distinctive porphyritic intrusions are exposed largely in the central part of the district: feldspar quartz porphyry, plagioclase quartz porphyry, feldspar biotite quartz porphyry, and feldspar porphyry. Intrusions consist of 64 to 70 percent SiO2 and variable K2O/Na2O (0.14-5.33) that reflect proportions of K-feldspar and albite phenocrysts and megacrysts as well as partial alteration to K-mica; quartz and biotite phenocrysts are present in several subtypes. Albite may have formed during emplacement of magma in brine-saturated basinal strata, whereas hydrothermal alteration of matrix, phenocrystic, and megacrystic feldspar and biotite to K-mica, pyrite, and other hydrothermal minerals occurred during and after intrusion emplacement. Small volumes of garnet-diopside-quartz and retrograde epidote-mica-amphibole skarn have replaced carbonate rocks adjacent to one intrusion subtype (feldspar-quartz porphyry), but alteration of carbonate rocks at intrusion contacts elsewhere is inconsp. Uranium-lead ages of igneous zircons vary inconsistently from ?? 180 to 230

  5. Mineral chemistry and geochemistry of the Late Neoproterozoic Gabal Abu Diab granitoids, Central Eastern Dessert, Egypt: Implications for the origin of rare metal post-orogenic A-type granites (United States)

    Sami, Mabrouk; Ntaflos, Theodoros; Farahat, Esam S.; Ahmed, Awaad F.; Mohamed, Haroun A.


    The Neoproterozoic Gabal Abu Diab pluton is a part of the Arabian Nubian shield (ANS) continental crust and located in the Central Eastern Desert (CED) of Egypt. It constitutes multiphase granitic pluton intruded into granodiorite and metagabbro-diorite rocks with sharp and nonreactive contacts. Based on field observations, colors, structural variations and petrographic investigations, this granitic outcrop consists of an inner core of two-mica granite (TMG) followed outward by garnet bearing muscovite granite (GBMG) and albite granite (AG). Petrographical study indicated that medium to coarse-grained TMG is dominated by K-feldspar (Or88-98), quartz, plagioclase (albite, An0-7), muscovite and biotite with hypidiomorphic texture. With exception the appearance of garnet and the disappearance of biotite the GBMG resembles the TGM, while AG is leucocratic without any mafic mineral. The main accessories are zircon, Nb and Ta-bearing rutile, columbite, ilmenorutile, ilmenite, magnetite and apatite. This mineralogical similarity and the existence of columbite group minerals (CGM) in all granitoids, indicates a cogenetic relationship. Microprobe analyses reveal that, besides the CGM, rutile and ilmenite are the main repository phases for Nb-Ta-Ti. Columbite-(Mn) exists as individual subhedral crystals (up to 100μm in size) or intimate intergrowth with Nb-bearing rutile and/or ilmenite. The CGM are represented mostly by columbite-(Mn) with Ta/(Ta+Nb) and Mn/(Mn+Fe) ratio ranging from 0.02-0.08 and 0.4-0.9, respectively suggesting extreme degree of magmatic fractionation. Rutile contains significant amounts of Ta (up to 4 wt.% Ta2O5) and Nb (up to 22 wt.% Nb2O5). Biotites are phlogopite-annite in composition (Ann47-60Phlog40-53,on average) and are enriched with AlIV that characterize peraluminous granites. Garnets contain 60-69 mol.% spessartine and 28-36 mol.% almandine where, the ratio of spessartine and almandine together exceeds 95 mole percent, similar to garnet occur

  6. Thermodynamics and phase equilibria of the silicate-fluoride-water systems: Implications for fluorine-bearing granites (United States)

    Dolejs, David

    The progressive enrichment in volatiles and light incompatible elements observed during upper-crustal differentiation of granitic and rhyolitic magmas leads to significant changes in melt physical-chemical properties and has important implications for ore deposition and volcanic devolatization. Thermodynamic calculations and experimental studies of melting equilibria in the Na 2O-K2O-Al2O3-SiO2-F 2O-1-H2O system are used to evaluate mineral stabilities, fluid compositions, the extent of fluoride-silicate liquid-liquid immiscibility, fluorine and water solubility limits and differentiation paths of natural fluorine-bearing silicic magmas. The interaction of fluorine with rock-forming aluminosilicates corresponds to progressive fluorination by the thermodynamic component F2O-1. Formation of fluorine-bearing minerals first occurs in peralkaline and silica-undersaturated systems that buffer fluorine concentrations at very low levels (villiaumite, fluorite). The highest concentrations of fluorine are achieved in peraluminous silica-oversaturated systems, saturated with fluorite or topaz. Thermodynamic models of fluorosilicate melts indicate clustering of silicate tetrahedra in the Na2O-SiO 2-F2O-1 system, whereas initial NaAl-F short-range order evolves into partial O-F disorder in the albite-cryolite system. Experiments performed at 520-1100°C and 0.1-100 MPa completely describe liquidus relations and differentiation paths of fluorine-bearing felsic magmas. Coordination differences and short-range order effects between [NaAl]-F, Na-F vs. Si-O lead to the fluoride-silicate liquid immiscibility, which extends from the silica-cryolite binary through the peralkaline albite-silica-cryolite ternary and closes in multicomponent, topaz-bearing systems owing to the destabilizing effect of increasing peraluminosity. Liquidus relations indicate that fluoride-silicate liquid-liquid immiscibility is inaccessible to quartz-feldspar-saturated granitic melts. Differentiation paths of

  7. Caracterización hidroquímica y análisis de los estados de equilibrio termodinámico en aguas termominerales de Alhama de Murcia (Murcia, Espana

    Directory of Open Access Journals (Sweden)

    Padilla Benítez, A.


    Full Text Available The principal physico-chemical characteristics of sorne thermomineral waters of Alhama de Murcia detrital aquifer are studied. The waters show a temperature between 26-41 °C and they are calcium-magnesium chloride-sulphate type. The origin of ions has a direct relationship with the dissolution of evaporitic sulphate-chloride salts, carbonatic and silica rocks, agricultural contamination processes and possibly ore-deposits. Mixing processes with cold waters possibly also occur. By SOLMINEQ.88 program the thermodinamic equilibrium conditions in surface are studied; the samples are saturated in quartz, chalcedony and albite. A great part of the waters are also saturated in calcite, aragonite, dolomite, gypsum, barite and magnesite. Finally, the waters are undersaturated in cristobalite, anhydrite and fluorite. Conventional chemical geothermometers yield a broad range of temperatures. Both, calcite-dolomite and anhydrite-fluorite geothermometers was applied to two samples with anomalous results. The saturation index modeling, at a series of growing temperatures, shows an approach equilibrium with quartz, chalcedony, albite, sanidine, gipsum, anhydrite, gibbsite and halloisite between 80-110 °C. A spread in the apparent equilibration temperatures deduced from two metodology, should be a consequence of dilution by surface waters, effects of re-equilibration of minerals with waters and CO2 loss. Temperature and chemical composition of the waters shows a thermal anomaly directly related with the tectonic activity in the area.Se estudian las principales características físico-químicas de algunas aguas termominerales del acuífero detrítico de Alhama de Murcia cuya temperatura está comprendida entre 26 y 41 °C y son de facies clorurada-sulfatada cálcico-magnésica. El origen de los iones encontrados está relacionado con la disolución de materiales evaporíticos, sales sulfatadas y cloruradas, carbonatados y silicatados, procesos de

  8. Calculation of the 13C NMR shieldings of the C0 2 complexes of aluminosilicates (United States)

    Tossell, J. A.


    complexation are much smaller. Complexation with CO 2 greatly increases the electric field gradient at the bridging oxygen of H 3AlOAlH 3-2, raising it to a value similar to that found for SiOSi linkages. Comparison of these results with the experimental 13C NMR spectra support the formation of CO 2-like complexes at SiOSi bridges in albite glasses and CO 3-like complexes at SiOAl and AlOAl bridges in albite and nepheline glasses. Changes in the calculated shieldings as Na + ions are added to the complexes suggest that some of the observed complexes may be similar in their CO 2-aluminosilicate interactions, but different with respect to the positions of the charge-compensating Na + ions.

  9. Plagioclase deformation in upper-greenschist facies meta-pegmatite mylonites from the Austroalpine Matsch Unit (Eastern Alps, Italy) (United States)

    Eberlei, Tobias; Habler, Gerlinde; Abart, Rainer; Grasemann, Bernhard


    Feldspars are common rock forming minerals as they are stable over a wide range of bulk rock compositions and metamorphic conditions within the Earth's crust. The deformation mechanisms of feldspar play an important role in rheological models for the crust and therefore have received considerable attention in studies on natural rocks and in experimental studies. The interaction of frictional and viscous deformation mechanisms and the onset of crystal plastic deformation in feldspars occur over a broad range of pressures and temperatures. In this work, we present new microstructural, textural and mineral chemical data of plagioclase from Permian metapegmatites within the Austroalpine Matsch Unit in Southern Tyrol (Italy). These crystalline basement rocks were deformed and metamorphosed at conditions close to the greenschist/amphibolites facies transition at 480±26°C during the Cretaceous (Habler et al., 2009). The investigated samples have been collected from meter-scale shear zones which typically occur at boundaries of lithological subunits. The southern tectonic boundary of this unit is commonly referred to as the "Vinschgau Shear Zone" (Schmid & Haas, 1989). We applied the Electron Backscatter Diffraction method to investigate the grain- and subgrain-boundaries and the nature of effective deformation mechanisms in plagioclase. Large albite porphyroclasts in the mylonitic Permian metapegmatites show grain internal traces of dissolution surfaces and the formation of new, strain-free grains with straight grain boundary segments and partly 120° grain boundary triple junctions in dilatant sites. The aggregates of new grains neither have a lattice preferred orientation nor a crystallographic orientation relation with the adjacent clast, and are characterized by the lack of grain internal deformation, suggesting that these are new precipitates rather than clast-fragments or recrystallized subgrains. Furthermore, the porphyroclasts show cracks and kinks, associated

  10. Identification of secondary minerals crystallized by low and high temperature alteration in the Northern Kyushu-Palau Ridge volcanic rocks (United States)

    Haraguchi, S.


    characteristics of bulk composition of the Nichinan Seamount rocks are assumed similarity to primary signature. On the other hand, the Komahashi-Daini Seamount samples show completely re-crystallization, and igneous textures are observed to pseudomorph. These are identified by XRD to be quartz, clinochlore (one of chlorite), and albite. Secondary mineral assemblage is homogeneous in these rocks. The temperature of replacement by chlorite accompanied by enrichment in MgO is estimated to be more than 150°C on the basis of experimental studies (e.g. Mottle 1983). And interpreted two types of albitization, low temperature ( 100°C), are identified on the basis of study of ODP Leg 123 Site 765 igneous rocks (Gillis et al. 1992). Therefore, it is considered that volcanic rocks from the Komahashi-Daini Seamount were under effect of hydrothermal alteration more than 150°C. Many elements show significant movement under high temperature hydrothermal alteration (e.g. Laverne et al. 1996). That is, re-crystallization of chlorite under high temperature hydrothermal alteration accompanied addition of magnesium from seawater and remarkable bulk MgO enrichment (e.g. Nakamura, 2001). Therefore, it is considered that the Komahashi-Daini Seamount rocks show significant MgO-enrichment because of secondary mineralization of chlorite, and assumed to significant movement of other elements. These observations suggest that geochemical investigation of highly altered rocks must be made with caution.

  11. Anotaciones Geoquímicas para Exploración de Esmeraldas en la Región Muzo-Coscuez con Base en la Relación Na/K y Elementos Traza Anotaciones Geoquímicas para Exploración de Esmeraldas en la Región Muzo-Coscuez con Base en la Relación Na/K y Elementos Traza

    Directory of Open Access Journals (Sweden)

    Mendoza Parada Jaime E.


    Full Text Available This study covers the northwestern area of the emerald belt in the Muzo-Coscuez District located in the western edge of the Eastern Cordillera of Colombia, Departamento de Boyacá. The study area includes sediments of Lower Cretaceous age, affected by fault systems and fractures which were accompanied by mineralizing events produced from fluid migration reacting with cromophores of the including rock, providing the esmeralds origin.  The emerald mineralization is stratigraphically restricted to the shaly level of the carbonaceouscalcareous facies locked toward the top of Calcareous Shale member and base of the Carbonaceous Shale unit of Paja Formation. This shaly unit is mineralogically associated whith rhombohedral calcite, pyrite, albite and pyrophyllite, which are minerals formed at low temperature conditions, as a result of post-magmatic hydrothermal-neumatholithic processes and fluids provided by the including rock. Geochemically it is established that the albitization processes favor the emerald formation, meanwhile the potassic metasomatism related to regional metamorphism and dynamic tectonism inhibit the emerald mineralization as high temperatures are generated. The best indicators at local and regional considerations to conduct the geochemical exploration for emeralds are the behavior of chemical elements present in the water, active sediments, soil and rocks where the anomalous concentration of Na/K are higher than 1.The high anomalous concentrations of sodium and some elements in rare earths constitute also excellent indicators to conduit geochemical exploration.Este estudio comprende el área noroccidental del cinturón esmeraldífero en la región Muzo-Coscuez, estribaciones occidentales de la Cordillera Oriental de Colombia en el Departamento de Boyacá, conformado por sedimentitas de edad Cretáceo Inferior, afectadas estructuralmente por sistemas de fallas, fracturas acompañadas de eventos mineralizantes por migración de

  12. The rare-metal ore potential of the Proterozoic alkaline ultramafic massifs from eastern part of the Baltic Shield in the Kola alkaline province. (United States)

    Sorokhtina, Natalia; Kogarko, Lia


    The Kola Alkaline Province consists of intrusions of two main stages of the intraplate alkaline magmatism. The early stage of igneous activity occurred in Proterozoic 1.9 billion years ago, the next in Paleozoic at 380 million years. The Proterozoic alkaline magmatism produced Gremyakha-Vyrmes and Elet'ozero large alkaline-ultrabasic massifs, Tiksheozero carbonatite massif and numerous small syenite complexes. Paleozoic magmatism on Baltic Shield exhibited more widely, than Proterozoic. The world largest Khibiny and Lovozero alkaline intrusions, numerous alkaline-ultrabasic massifs with carbonanites, alkaline dike swarms and diatremes were formed. It is well known that carbonatites of Paleozoic alkaline-ultrabasic massifs contain large-scale deposits of rare-metal ores (Afanasiev et al., 1998). The metasomatic rocks on foidolites and carbonatites of Gremyakha-Vyrmes are final products of differentiation of Proterozoic alkaline-ultrabasic magma enriched in incompatible elements, including Nb and Zr similar to Paleozoic carbonatites. The massif Gremyakha-Vyrmes is one of the largest titanomagnetite-ilmenite deposits in Russia associated with ultrabasites. Our investigation showed that albite-microcline and aegirine-albite metasomatites formed rich rare-metal ores consisting of 3.2 wt. % Nb2O5 and 0.7 ZrO2. Zircon and pyrochlore-group minerals represent the main minerals of rare-metal ores. The following evolutionary sequences of pyrochlore group minerals has been observed: betafite or U pyrochlore - Na-Ca pyrochlore - Ba-Sr pyrochlore - "silicified" pyrochlore - Fe-Nb, Al-Nb silicates. Such evolution from primary Nb oxides to secondary silicates under low temperature hydrothermal conditions is similar to the evolution of rare metal phases in Paleozoic alkaline massifs analogous to Lovozero syenites and in carbonatites. The rare metal minerals of Gremyakha-Vyrmes crystallized in high alkaline hydrothermal environment at increased activity of Nb, Ta, Zr, U, Th and at

  13. The mechanisms of water diffusion in polymerized silicate melts (United States)

    Behrens, Harald; Nowak, M.


    Diffusion of water was experimentally investigated for melts of albitic (Ab) and quartz-orthoclasic (Qz29Or71, in wt %) compositions with water contents in the range of 0 to 8.5 wt % at temperatures of 1100 to 1200 °C and at pressures of 1.0 and 5.0 kbar. Apparent chemical diffusion coefficients of water ( D water) were determined from concentration-distance profiles measured by FTIR microspectroscopy. Under the same P- T condition and water content the diffusivity of water in albitic, quartz-orthoclasic and haplogranitic (Qz28Ab38 Or34, Nowak and Behrens, this issue) melts is identical within experimental error. Comparison to data published in literature indicates that anhydrous composition only has little influence on the mobility of water in polymerized melts but that the degree of polymerization has a large effect. For instance, Dwater is almost identical for haplogranitic and rhyolitic melts with 0.5-3.5 wt % water at 850 °C but it is two orders of magnitude higher in basaltic than in haplogranitic melts with 0.2-0.5 wt % water at 1300 °C. Based on the new water diffusivity data, recently published in situ near-infrared spectroscopic data (Nowak 1995; Nowak and Behrens 1995), and viscosity data (Schulze et al. 1996) for hydrous haplogranitic melts current models for water diffusion in silicate melts are critically reviewed. The NIR spectroscopy has indicated isolated OH groups, pairs of OH groups and H2O molecules as hydrous species in polymerized silicate melts. A significant contribution of isolated OH groups to the transport of water is excluded for water contents above 10 ppm by comparison of viscosity and water diffusion data and by inspection of concentration profiles from trace water diffusion. Spectroscopic measurements have indicated that the interconversion of H2O molecules and OH pairs is relatively fast in silicate glasses and melts even at low temperature and it is inferred that this reaction is an active step for migration of water. However

  14. Petrogenesis of pillow basalts from Baolai in southwestern Taiwan (United States)

    Liu, Chih-Chun; Yang, Huai-Jen


    The pillow basalts from Baolai in southwestern Taiwan have been inferred to bear Dupal signautres based on their Th/Ce ratio, linking the Baolai basalts to the South China Sea (SCS) seamounts that are characterized by Dupal Pb isotope signatures (Smith and Lewis, 2007). In this study, thirty-two Baolai basalt samples were analyzed for abundances of major and trace elements as well as Pb and Nd isotope ratios to verify their Dupal characters and to constrain their petrogenesis significance. The Baolai basalts contain 4-10 % L.O.I.. Three stages of alteration are inferred from plots of L.O.I. abundance versus concentrations major oxides as well as mineral textures and compositions. The first alteration stage was characterized by albitization that converted Ca-rich plagioclase to albite. The second alteration stage was dominated by chloritization of olivine and augite, resulting in increases in L.O.I. abundance. The last alteration stage is represented by formation of secondary calcite in vesicles and cracks. These alteration processes reflect interaction with seawater and apparently did not affect the magmatic Pb isotope composition for the low Pb concentration in seawater. Relative to the North Hemisphere Reference Line (NHRL), the Baolai pillow basalts have higher 208Pb/204Pb ratios at a given 206Pb/204Pb value, showing Dupal anomaly. For their relatively higher 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios, the Baolai basalts are distinct from majority of the Cenozoic basalts in the Hainan-Leizhou peninsula, the Indochina peninsula, and the SCS seamounts, for which derivation from the Hainan mantle plume has been recently proposed (Wang et al., 2013). In contrast, the Baolai basalts and the Cenozoic basalts from eastern Guangdong at southeastern China have similar Pb and Nd isotope compositions, indicating derivation from similar mantle sources. However, the Baolai basalts have lower abundance ratios of Zr/Hf (40.3-45.6 versus 46.5-50.5), La/Yb (12

  15. Inverse Geochemical Reaction Path Modelling and the Impact of Climate Change on Hydrologic Structure in Snowmelt-Dominated Catchments in the Southwestern USA (United States)

    Driscoll, J. M.; Meixner, T.; Molotch, N. P.; Sickman, J. O.; Williams, M. W.; McIntosh, J. C.; Brooks, P. D.


    Snowmelt from alpine catchments provides 70-80% of the American Southwest's water resources. Climate change threatens to alter the timing and duration of snowmelt in high elevation catchments, which may also impact the quantity and the quality of these water resources. Modelling of these systems provides a robust theoretical framework to process the information extracted from the sparse physical measurement available in these sites due to their remote locations. Mass-balance inverse geochemical models (via PHREEQC, developed by the USGS) were applied to two snowmelt-dominated catchments; Green Lake 4 (GL4) in the Rockies and Emerald Lake (EMD) in the Sierra Nevada. Both catchments primarily consist of granite and granodiorite with a similar bulk geochemistry. The inputs for the models were the initial (snowpack) and final (catchment output) hydrochemistry and a catchment-specific suite of mineral weathering reactions. Models were run for wet and dry snow years, for early and late time periods (defined hydrologically as 1/2 of the total volume for the year). Multiple model solutions were reduced to a representative suite of reactions by choosing the model solution with the fewest phases and least overall phase change. The dominant weathering reactions (those which contributed the most solutes) were plagioclase for GL4 and albite for EMD. Results for GL4 show overall more plagioclase weathering during the dry year (214.2g) than wet year (89.9g). Both wet and dry years show more weathering in the early time periods (63% and 56%, respectively). These results show that the snowpack and outlet are chemically more similar during wet years than dry years. A possible hypothesis to explain this difference is a change in contribution from subsurface storage; during the wet year the saturated catchment reduces contact with surface materials that would result in mineral weathering reactions by some combination of reduced infiltration and decreased subsurface transit time. By

  16. ⁵³Mn-⁵³Cr and ²⁶Al-²⁶Mg ages of a feldspathic lithology in polymict ureilites

    Energy Technology Data Exchange (ETDEWEB)

    Goodrich, Cyrena Anne [Planetary Science Institute. Tucson, AZ (United States); Hutcheon, Ian D. [Glenn T. Seaborg Institute. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kita, Noriko T. [Dept. of Geoscience. Univ. of Wisconsin, Madison, WI (United States); Huss, Gary R. [NASA Marshall Space Flight Center (MSFC), Huntsville, AL (United States); Cohen, Barbara Anne [Hawaii Institute of Geophysics and Planetology. Univ. of Hawaii, Honolulu, HI (United States); Keil, Klaus


    We report 53Mn–53Cr and 26Al–26Mg isotopic data, obtained by in-situ SIMS analysis, for feldspathic clasts in polymict ureilites DaG 319 and DaG 165. The analyzed clasts belong to the “albitic lithology,” the most abundant population of indigenous feldspathic materials in polymict ureilites, and are highly fractionated igneous assemblages of albitic plagioclase, Fe-rich pyroxenes, phosphates, ilmenite, silica, and Fe(Mn, K, P, Ti)-enriched glass. Glass in DaG 165 clast 19 has extremely high and variable 55Mn/52Cr ratios (500–58,000) and shows correlated 53Cr excesses up to ~ 1500‰, clearly indicating the presence of live 53Mn at the time of formation. The slope of the well-correlated isochron defined by glass and pyroxenes from this clast corresponds to (53Mn/55Mn) = (2.84 ± 0.10) × 10-6 (2σ). Data for less 55Mn/52Cr-enriched glasses from DaG 319 clast B1, as well as phosphates from several other clasts, are consistent with this isochron. The 53Mn/55Mn ratio obtained from the isochron implies that these clasts are 0.70 ± 0.18 Ma younger than the D'Orbigny angrite, corresponding to the absolute age of 4563.72 ± 0.22 Ma. Plagioclase in DaG 319 clast B1 has a fairly constant 27Al/24Mg ratio of ~ 900 and shows resolvable 26Mg excesses of ~ 2‰. The slope of the isochron defined by pyroxene and plagioclase in this clast is (3.0 ± 1.1) × 10-7 (2σ), corresponding to a time difference of 5.4 (-0.3/+0.5) Ma after CAI (assuming the canonical initial 26Al/27Al ratio of 5 × 10-5) and an age 0.5 (-0.3/+0.5) Ma younger than D'Orbigny. Its absolute age (relative to D'Orbigny) is 4563.9 (+ 0.4/-0.5) Ma, in agreement with the 53Mn–53Cr age from clast 19. These data provide the first

  17. Intensive low-temperature tectono-hydrothermal overprint of peraluminous rare-metal granite: a case study from the Dlhá dolina valley (Gemericum, Slovakia

    Directory of Open Access Journals (Sweden)

    Breiter Karel


    Full Text Available A unique case of low-temperature metamorphic (hydrothermal overprint of peraluminous, highly evolved rare-metal S-type granite is described. The hidden Dlhá dolina granite pluton of Permian age (Western Carpathians, eastern Slovakia is composed of barren biotite granite, mineralized Li-mica granite and albitite. Based on whole-rock chemical data and evaluation of compositional variations of rock-forming and accessory minerals (Rb-P-enriched K-feldspar and albite; biotite, zinnwaldite and di-octahedral micas; Hf-(Sc-rich zircon, fluorapatite, topaz, schorlitic tourmaline, the following evolutionary scenario is proposed: (1 Intrusion of evolved peraluminous melt enriched in Li, B, P, F, Sn, Nb, Ta, and W took place followed by intrusion of a large body of biotite granites into Paleozoic metapelites and metarhyolite tuffs; (2 The highly evolved melt differentiated in situ forming tourmaline-bearing Li-biotite granite at the bottom, topaz-zinnwaldite granite in the middle, and quartz albitite to albitite at the top of the cupola. The main part of the Sn, Nb, and Ta crystallized from the melt as disseminated cassiterite and Nb-Ta oxide minerals within the albitite, while disseminated wolframite appears mainly within the topaz-zinnwaldite granite. The fluid separated from the last portion of crystallized magma caused small scale greisenization of the albitite; (3 Alpine (Cretaceous thrusting strongly tectonized and mylonitized the upper part of the pluton. Hydrothermal low-temperature fluids enriched in Ca, Mg, and CO2 unfiltered mechanically damaged granite. This fluid-driven overprint caused formation of carbonate veinlets, alteration and release of phosphorus from crystal lattice of feldspars and Li from micas, precipitating secondary Sr-enriched apatite and Mg-rich micas. Consequently, all bulk-rock and mineral markers were reset and now represent the P-T conditions of the Alpine overprint.

  18. Effects of Al/Si ordering on feldspar dissolution: Part II. The pH dependence of plagioclases' dissolution rates (United States)

    Yang, Yi; Min, Yujia; Jun, Young-Shin


    The rate of mineral dissolution in an aquatic environment is sensitive to the pH of the contacting solution. The pH dependence of mineral dissolution rate has been interpreted by the Transition State Theory-Surface Complexation Model (TST-SCM) formalism in terms of pH-sensitive variability in surface chemistry. In this study, we provide an alternative interpretation for the experimentally observed nonlinear pH dependence of feldspar dissolution rates. The interpretation is based on a new formalism for feldspar dissolution which, while compatible with the TST-SCM formalism, incorporates the effects of both surface chemistry and bulk chemistry on feldspar dissolution into the quantification of dissolution rate. The pH dependence of dissolution rate varies from one feldspar specimen to another because different TOT linkages within one solid matrix can respond differently to the attack of proton. Our results suggest that the pH dependence of feldspar dissolution rate is not a constant in general, and could be affected by pH, substitutional Al/Si ordering, chemical composition of the specimen, and the relative rapidness of linkage hydrolysis according to different mechanisms. The rate law proposed in this study is able to capture the experimentally observed pH dependence of the dissolution rates of a series of plagioclases, including albite, andesine, labradorite, bytownite, and anorthite. The effectiveness of the newly proposed formalism for feldspar dissolution, hence, suggests that dissolution reactions of minerals are combinations of surface renewal and heterogeneous chemical reactions. The currently widely used TST-SCM-based rate laws can be further improved by taking into account the effects of bulk chemistry and surface renewal in the prediction of mineral dissolution rates. An improved formalism for mineral dissolution will be mineral-specific, and will reflect the effects of the temporal decay in the availability of reactive surface sites as well as the

  19. Significance of "stretched" mineral inclusions for reconstructing P- T exhumation history (United States)

    Ashley, Kyle T.; Darling, Robert S.; Bodnar, Robert J.; Law, Richard D.


    Analysis of mineral inclusions in chemically and physically resistant hosts has proven to be valuable for reconstructing the P- T exhumation history of high-grade metamorphic rocks. The occurrence of cristobalite-bearing inclusions in garnets from Gore Mountain, New York, is unexpected because the peak metamorphic conditions reached are well removed (>600 °C too cold) from the stability field of this low-density silica polymorph that typically forms in high temperature volcanic environments. A previous study of samples from this area interpreted polymineralic inclusions consisting of cristobalite, albite and ilmenite as representing crystallized droplets of melt generated during a garnet-in reaction, followed by water loss from the inclusion to explain the reduction in inclusion pressure that drove the transformation of quartz to cristobalite. However, the recent discovery of monomineralic inclusions of cristobalite from the nearby Hooper Mine cannot be explained by this process. For these inclusions, we propose that the volume response to pressure and temperature changes during exhumation to Earth's surface resulted in large tensile stresses within the silica phase that would be sufficient to cause transformation to the low-density (low-pressure) form. Elastic modeling of other common inclusion-host systems suggests that this quartz-to-cristobalite example may not be a unique case. The aluminosilicate polymorph kyanite also has the capacity to retain tensile stresses if exhumed to Earth's surface after being trapped as an inclusion in plagioclase at P- T conditions within the kyanite stability field, with the stresses developed during exhumation sufficient to produce a transformation to andalusite. These results highlight the elastic environment that may arise during exhumation and provide a potential explanation of observed inclusions whose stability fields are well removed from P- T paths followed during exhumation.

  20. Status of geochemical modeling of groundwater evolution at the Tono in-situ tests site, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Sasamoto, Hiroshi; Yui, Mikazu [Japan Nuclear Cycle Development Inst., Tokai Works, Tokai, Ibaraki (Japan); Arthur, R.C. [Monitor Scientific, L.L.C., Denver, Colorado (United States)


    Hydrochemical investigation of Tertiary sedimentary rocks at JNC's Tono in-situ tests site indicate the groundwaters are: meteoric in origin, chemically reducing at depths greater than a few tens of meters in the sedimentary rock, relatively old [carbon-14 ages of groundwaters collected from the lower part of the sedimentary sequence range from 13,000 to 15,000 years BP (before present)]. Ca-Na-HCO{sub 3} type solutions near the surface, changing to Na-HCO{sub 3} type groundwaters with increasing depth. The chemical evolution of the groundwaters is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the 'real' groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, Al, carbonate and sulfate) if the following assumptions are adopted: CO{sub 2} concentration in the gas phase contacting pore solutions in the overlying soil zone=10{sup -1} bar, minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), muscovite (K) and pyrite (Eh and sulfate). It is noted, however, that the available field data may not be sufficient to adequately constrain parameters in the groundwater evolution model. In particular, more detailed information characterizing certain site properties (e.g., the actual mineralogy of 'plagioclase', 'clay' and 'zeolite') are needed to improve the model. Alternative conceptual models of key reactions may also be necessary. For this reason, a model that accounts for ion-exchange reactions among clay minerals, and which is based on the results of laboratory experiments, has also been evaluated in the present study. Further improvements of model considering ion-exchange reactions are needed in future, however. (author)

  1. Preliminary stratigraphic and petrologic characterization of core samples from USW-G1, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Tuffs of the Nevada Test Site are currently under investigation to determine their potential for long-term storage of radioactive waste. As part of this program, hole USW-G1 was drilled to a depth of 6000 ft below the surface, in the central part of the Yucca Mountain area, Nevada Test Site, Nevada. Petrographic study of the USW-G1 core is presented in this report and shows the tuffs (which generally were variably welded ash flows) are partly recrystallized to a variety of secondary minerals. The important alteration products are zeolites (heulandite, clinoptilolite, mordenite and analcime), smectite clays with minor interstratified illite, albite, micas, potassium feldspar, and various forms of silica. Iijima's zeolite zones I through IV of burial metamorphism can be recognized in the core. Zeolites are first observed at about the 1300-ft depth, and the high-temperature boundary of zeolite stability in this core occurs at about 4350 ft. Analcime persists, either metastably or as a retrograde mineral, deeper in the core. The oxidation state of Fe-Ti oxide minerals, through most of the core, increases as the degree of welding decreases, but towards the bottom of the hole, reducing conditions generally prevail. Four stratigraphic units transected by the core may be potentially favorable sites for a waste repository. These four units, in order of increasing depth in the core, are (1) the lower cooling unit of the Topopah Spring Member, (2) cooling unit II of the Bullfrog Member, (3) the upper part of the Tram tuff, and (4) the Lithic-rich tuff

  2. Allanite from the El Muerto Pegmatite, Oaxaca, Mexico: A Potential New Standard for 232Th-208Pb Dating by LA-ICP-MS (United States)

    Price, J.; Crowley, J. L.; Solari, L.; Prol-Ledesma, R.


    Allanite dating may be important to studies addressing tectonomagmatic evolution, provenance of monocyclic sediment, and mineral weathering. Obtaining accurate allanite ages by SIMS has been challenging and time-consuming due to the mineral's extreme chemical variability which often prevents finding adequately matrix-matched standards. Isotopic measurements by LA-ICP-MS minimize the need for standards of nearly identical composition to the unknown allanite being analyzed, and it is done relatively rapidly. Dating by LA-ICP-MS requires high quality standards for isotopic fractionation corrections. However, readily accessible and well characterized allanite standards are scarce. We investigated gemstone allanite from the El Muerto pegmatite, Oaxaca, Mexico, as a potential new geochronology standard for 232Th-208Pb allanite dating by LA-ICP-MS. Compositional homogeneity was thoroughly investigated by scanning and backscatter electron microscopy, cathodoluminescence, quantitative and qualitative energy dispersive x-ray spectroscopy, electron microprobe, and LA-ICP-MS. The possibility of metamictization was investigated by extensive X-ray diffraction analyses. The El Muerto allanite was U-Pb dated by ID-TIMS, with common Pb ratios determined from cogenetic K-feldspar by ID-TIMS and LA-MC-ICP-MS. Future work includes Th-Pb dating by ID-TIMS. The samples investigated are homogeneous with respect to major and trace elements. Major element compositional results are generally in agreement with published values, and no metamictization was identified despite the allanite being nearly 1 Ga. The only limitation of the El Muerto allanite is that it contains small, generally <100 μm, scarce inclusions of quartz, calciothorite, albite, calcite, and biotite. However, these grains are easily recognized and avoided during LA-ICP-MS analyses. Based on these results, the El Muerto allanite has the potential to serve as a standard for LA-ICP-MS dating.

  3. Metasomatic silicate chemistry at the Bayan Obo Fe REE Nb deposit, Inner Mongolia, China: Contrasting chemistry and evolution of fenitising and mineralising fluids (United States)

    Smith, M. P.


    Fenite aureoles around carbonatite dykes, and alteration associated with Fe-REE-Nb ore bodies at Bayan Obo, Inner Mongolia, China, show alkali silicate assemblages containing aegirine-augite, (magnesio-)riebeckite, (magnesio-)arfvedsonite, and phlogopite, accompanied by varying amounts of apatite, albite and quartz. In both fenites and orebodies simple thermodynamic constraints indicate mineral parageneses are consistent with rock buffered cooling accompanied by the infiltration of a range of externally buffered hydrothermal fluids. Statistical analysis of amphibole chemistry indicates that even in apparently texturally well constrained paragenetic stages wide variations in chemistry occur in both the ore bodies and fenites. Much of this variation is attributable to the Mg and F content of amphibole, and is therefore interpreted as a result of variation in externally controlled variables ( P, T, initial fluid composition) rather than internally controlled variables such as protolith composition. Similarities in chemistry exist between fenite and some ore body amphiboles. Thermodynamic analysis of the composition of biotite and apatite allows constraints to be placed on the F-content of hydrothermal fluids, and indicates relatively consistent compositions in fenites and orebodies (log aHF/ aH 2O = - 3.8 to - 3.6 at 300 °C and 1 kbar). Amphibole and biotite associated with niobate mineralization are both enriched in fluorine relative to the rest of the paragenesis, and biotite compositions indicate significantly higher HF activities in the hydrothermal fluid (log aHF/ aH 2O = - 2.6 at 300 °C and 1 kbar). The data presented here reinforce previous interpretations of the complex, multistage nature of mineralisation at Bayan Obo, but are still consistent with a direct involvement of carbonatite derived fluids during ore genesis.

  4. Geochemistry and age of metamorphosed felsic igneous rocks with A-type affinities in the Willyama Supergroup, Olary Block, South Australia, and implications for mineral exploration (United States)

    Ashley, P. M.; Cook, N. D. J.; Fanning, C. M.


    Leucocratic quartzofeldspathic gneisses form a significant proportion of the lower part of the Palaeoproterozoic Willyama Supergroup sequence in the Olary Block, South Australia and have correlatives in the adjacent Broken Hill Block. Field and geochemical data demonstrate that these rocks were originally rhyolitic volcanics and granite, with A-type affinities consistent with magma production during intracratonic rifting, supporting tectonic models proposed for the Willyama Supergroup in the Broken Hill Block. Although the rocks have characteristic high-field-strength element enrichment, many have undergone extensive pervasive pre- or syn-metamorphic sodic alteration and are typically rich in albite. Sensitive high resolution ion microprobe (SHRIMP) U-Pb zircon data tightly constrain the depositional and early intrusive history. Zircons from an interpreted metavolcanic rock containing relict quartz phenocrysts yield an age of 1699 ± 10 Ma, whereas a metagranitoid sample has an age of 1703 ± 6 Ma. These results are compatible with recent geochronological data on felsic metavolcanic rocks from the Broken Hill Block (Page and Laing, 1992) and are indicative of widespread magmatism during deposition of the Willyama Supergroup. Nd signatures for the two Olary Block samples imply the presence of a significant component from a depleted mantle source. The A-type metavolcanic rocks are locally associated with small iron formations, some of which grade into stratiform barite-rich horizons. Although potentially favourable for sediment-hosted exhalative PbZn mineralisation, the Fe- and Ba-rich units, along with transgressive vein and breccia occurrences of Fe oxides ± quartz ± pyrite cutting both the metavolcanic and metagranitoid rocks, may be more prospective for epigenetic Cu-Au mineralisation related to later metamorphic and/or magmatic events. Partial melting of the A-type suite during high grade regional metamorphism at ~ 1600 ± 20 Ma led to the formation of local

  5. Delineating Spatial Patterns in the Yellowstone Hydrothermal System using Geothermometry (United States)

    King, J.; Hurwitz, S.; Lowenstern, J. B.


    Yellowstone National Park is unmatched with regard to its quantity of active hydrothermal features. Origins of thermal waters in its geyser basins have been traced to mixing of a deep parent water with meteoric waters in shallow local reservoirs (Fournier, 1989). A mineral-solution equilibrium model was developed to calculate water-rock chemical re-equilibration temperatures in these shallow reservoirs. We use the GeoT program, which uses water composition data as input to calculate saturation indices of selected minerals; the "best-clustering" minerals are then statistically determined to infer reservoir temperatures (Spycher et al., 2013). We develop the method using water composition data from Heart Lake Geyser Basin (HLGB), for which both chemical and isotopic geothermometers predict a reservoir water temperature of 205°C ± 10°C (Lowenstern et al., 2012), and minerals found in drill cores in Yellowstone's geyser basins. We test the model for sensitivity to major element composition, pH, Total Inorganic Carbon (TIC) and selected minerals to optimize model parameters. Calculated temperatures are most accurate at pH values below 9.0, and closely match the equilibrium saturation indices of quartz, stilbite, microcline, and albite. The model is optimized with a TIC concentration that is consistent with the mass of diffuse CO2 flux in HLGB (Lowenstern et al., 2012). We then use water compositions from other thermal basins in Yellowstone in search of spatial variations in reservoir temperatures. We then compare the calculated temperatures with various SiO2 and cation geothermometers.

  6. Petrography and geochemical study of Nezam-Abad area, Southwest of Shazand, Arak

    Directory of Open Access Journals (Sweden)

    Robabeh Jafari


    Full Text Available Nezam-Abad area is located in southwest of Shazand (Arak which is a part of Sanandaj-Sirjan zone. Major intrusive rocks of Nezam-Abad are quartz diorite and minor amount of granodiorite. Leucogranitic, pegmatite dykes and quartz-tourmaline veins were intruded the quartz diorite. Quartz diorites are mainly composed of plagioclase, hornblende, biotite, quartz and pyroxene as major minerals. Major minerals of leucogranite are microcline, orthoclase, albite, quartz, biotite and muscovite. Accessory minerals consist of apatite, zircon, sphene, epidote, allanite, tourmaline and opaque. The presence of hydrous minerals like hornblende and biotite in these rocks indicate that the corresponding magma initially contained >3 wt% H2O (wet magma. The occurrences of garnet and andalusite minerals suggest assimilation process. Primary textures in these rocks are granular, granophyre, and poikilitic. Secondary textures are perthite, myrmekite, sericitization, chloritization and kaolinitization. Later hydrothermal activities and tectonic strains are factors for presence of perthite texture in leucogranite. K amount for sericitization of feldspars come from the K-feldspars and chloritization of biotite. Transformation of biotite to muscovite indicates the act of K rich fluid in later stages. On the basis of chemical analysis on the intrusive rocks, it is shown that the magma was calc-alkaline, metaluminous-peraluminous and medium-K to high-K. Study of major elements in Harker diagrams indicates Al2O3, FeO, Fe2O3 and CaO decrease with increasing of SiO2 and K2O and Na2O increase indicating that fractional crystallization may have played an important role in the formation of granitoid rocks from Nezam-Abad.

  7. Environmental effect and genetic influence: a regional cancer predisposition survey in the Zonguldak region of Northwest Turkey (United States)

    Kadir, Selahattin; Önen-Hall, A. Piril; Aydin, S. Nihal; Yakicier, Cengiz; Akarsu, Nurten; Tuncer, Murat


    The Cretaceous-Eocene volcano-sedimentary units of the Zonguldak region of the western Black Sea consist of subalkaline andesite and tuff, and sandstone dominated by smectite, kaolinite, accessory chlorite, illite, mordenite, and analcime associated with feldspar, quartz, opal-CT, amphibole, and calcite. Kaolinization, chloritization, sericitization, albitization, Fe-Ti-oxidation, and the presence of zeolite, epidote, and illite in andesitic rocks and tuffaceous materials developed as a result of the degradation of a glass shards matrix, enclosed feldspar, and clinopyroxene-type phenocrysts, due to alteration processes. The association of feldspar and glass with smectite and kaolinite, and the suborientation of feldspar-edged, subparallel kaolinite plates to fracture axes may exhibit an authigenic smectite or kaolinite. Increased alteration degree upward in which Al, Fe, and Ti are gained, and Si, Na, K, and Ca are depleted, is due to the alteration following possible diagenesis and hydrothermal activities. Micromorphologically, fibrous mordenite in the altered units and the presence of needle-type chrysotile in the residential buildings in which cancer cases lived were detected. In addition, the segregation pattern of cancer susceptibility in the region strongly suggested an environmental effect and a genetic influence on the increased cancer incidence in the region. The most likely diagnosis was Li-Fraumeni syndrome, which is one of the hereditary cancer predisposition syndromes; however, no mutations were observed in the p53 gene, which is the major cause of Li-Fraumeni syndrome. The micromorphology observed in the altered units in which cancer cases were detected may have a role in the expression of an unidentified gene, but does not explain alone the occurrence of cancer as a primary cause in the region.

  8. Biochemical distributions (amino acids, neutral sugars, and lignin phenols) among size-classes of modern marine sediments from the Washington coast (United States)

    Keil, Richard G.; Tsamakis, Elizabeth; Giddings, J. Calvin; Hedges, John I.


    In order to examine relationships of organic matter source, composition, and diagenesis with particle size and mineralogy in modern marine depositional regimes, sediments from the continental shelf and slope along the Northwest Pacific rim (Washington coast, USA) were sorted into hydrodynamic size fractions (sand: >250, 63-250 μm; silt: 35-63, 17-35, 8-17, 3-8 μm; and clay-sized: 1-3, 0.5-1, fucose and rhamnose. Organic matter in the silt fractions, though degraded, is not as diagenetically altered as in the clay fractions. Enrichment of pollen grains in the silt-size material is reflected by high cinnamic acid to ferulic acid lignin phenol ratios. The highest pollen biochemical signal is observed in the silt fractions of the deepest station (1835 m), where pollen abundances are also highest. Organic matter tightly bound in the silt and sand-sized fractions are enriched in aldoses and show indications of enhanced microbial biomass as reflected by high weight percentages of ribose. Distinct organic debris was composed of relatively unaltered vascular plant remains as reflected by high lignin phenol yields and low acid/aldehyde ratios. Clay-size fractions are enriched in nitrogenous components, as reflected by elevated yields of total and basic amino acids (especially lysine). Silt- and sand-size fractions rich in quartz and albite show slightly higher yields of neutral amino acids. Consistent trends across all size classes and among the different depositional settings illustrates that only a small portion of the organic matter is present as distinct organic debris (e.g. pollen, vascular plant tissues, etc.), but that this debris can be isolated in specific size classes. The data for surface-associated organic matter are consistent with, but not conclusive of, selective partitioning of some organic matter to specific mineral surfaces. The dominant size class-specific trends in organic matter composition are due to changes in both source and diagenetic alteration.

  9. Nanomineralogy as a new dimension in understanding elusive geochemical processes in soils: The case of low-solubility-index elements

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Michael; Hochella, Michael F.


    Nanomineralogy is a new dimension in understanding chemical processes in soils. These processes are revealed at the nanoscale within the structures and compositions of phases that heretofore were not even known to exist in the soils in which they are found. The discovery and understanding of soil chemistry in this way is best accessible via a combination of focused ion beam technology (for sample preparation) and high resolution, analytical transmission electron microscopy (for phase identification). We have used this scientific framework and these techniques to decipher past and present chemical processes in a soil in Sudbury, Ontario, Canada that has been impacted by both smelter contamination (acidification) and subsequent remediation within the past century. In this study, we use these methods to investigate mobilization and sequestration of the relatively immobile elements Al, Ti and Zr. In a micrometer-thick alteration layer on an albite grain, a first generation of clay minerals represents weathering of the underlying mineral prior to the acidification of the soils. Complex assemblages of Ti- and Zr-bearing nanophases occur on the surfaces of Fe-(hydr)oxide crystals and are the result of the dissolution of silicates and oxides and the mobilization of Ti- and Zr-bearing colloids under acidic conditions. These phases include anatase (TiO2), kleberite (Fe3+Ti6O11(OH)5) Ti4O7, baddelyite (ZrO2), a structural analogue to kelyshite (NaZr[Si2O6(OH)]) and authigenic zircon (ZrSiO4). Subsequent remediation of the acidic soils has resulted in the sequestration of Al and in the neoformation of the clay minerals kaolinite, smectite and illite. These complex mineral assemblages form a porous layer that controls the interaction of the underlying mineral with the environment.

  10. The mineral chemistry of hydrothermally altered and metamorphosed wall-rocks at the Stollberg Fe-Pb-Zn-Mn(-Ag) deposit, Bergslagen, Sweden (United States)

    Ripa, M.


    The c. 1.9 Ga old Stollberg sulphide and Mnrich skarn iron ores and sulphide ores in Bergslagen, south-central Sweden are hosted by hydrothermally altered and metamorphosed felsic volcanic and volcaniclastic rocks. The ores are underlain by comformable alteration zones characterized by albite-gedrite-quartz and biotite-muscovite-plagioclase-K-feldspar-quartz +/- garnet assemblages. The present mineralogies are interpreted as medium-grade metamorphic equivalents to the original alteration mineral assemblages. PT-conditions during prograde regional metamorphism are semiquantatively determined to be 510 to 560 °C at approximately 3 kbar. With increasing modal content of gedrite and biotite in the alteration zones, the Mg/Fe ratios and XMg's in octahedral positions of these minerals also increase. In the gedrite-bearing strata, whole-rock Mg/Fe ratios remain constant, whereas in the biotite-rich unit the wholerock Mg/Fe trend is parallel to that of the biotites. The trends in the metamorphic mineral composition are interpreted to be a product of original changes in fluid composition during the evolution of a sub-seafloor hydrothermal system. During the initial stage of alteration, Fe-Mn-rich fluids altered the rocks, and during a later stage, the fluids became more Mg-rich, possibly due to entrainment of fresh seawater, and the alteration zones became relatively more Mg-rich. Sulphide precipitation was contemperaneous with Mg metasomatism, suggesting base metal precipitation was a function of the mixing of cool seawater with hydrothermal fluid. It is proposed that early hydrothermal alteration was associated with the deposition of areally extensive Fe-oxide formation, and that Mg metasomatism defines a second stage of hydrothermal activity during which sulphide mineralization overprinted the earlier formed Fe-oxide deposit.

  11. Influence of ash composition on the sintering behavior during pressurized combustion and gasification process

    Institute of Scientific and Technical Information of China (English)

    Ni-jie JING; Qin-hui WANG; Yu-kun YANG; Le-ming CHENG; Zhong-yang LUO; Ke-fa CEN


    To determine the ash characteristics during fluidized bed combustion and gasification purposes,the investigation of the impacts of chemical composition of Jincheng coal ash on the sintering temperature was conducted.A series of experiments on the sintering behavior at 0.5 MPa was performed using the pressurized pressure-drop technique in the combustion and gasification atmospheres.Meanwhile,the mineral transformations of sintered ash pellets were observed using X-ray diffractometer (XRD) analyzer to better understand the experimental results.In addition,quantitative XRD and field emission scanning electron microscope/energy dispersive X-ray spectrometer (FE-SEM/EDS) analyses of ash samples were used for clarifying the detailed ash melting mechanism.These results show that the addition of Fe2O3 can obviously reduce the sintering temperatures under gasification atmospheres,and only affect a little the sintering temperature under combustion atmosphere.This may be due to the presence of iron-bearing minerals,which will react with other ash compositions to produce low-melting-point eutectics.The FE-SEM/EDS analyses of ash samples with Fe2O3 additive show consistent results with the XRD measurements.The CaO and Na2O can reduce the sintering temperatures under both the combustion and gasification atmospheres.This can be also contributed to the formation of low-melting-point eutectics,decreasing the sintering temperature.Moreover,the fluxing minerals,such as magnetite,anhydrite,muscovite,albite and nepheline,contribute mostly to the reduction of the sintering temperature while the feldspar minerals,such as anorthite,gehlenite and sanidine,can react with other minerals to produce low-melting-point eutectics,and thereby reduce the sintering temperatures.

  12. Potentially toxic elements in lignite and its combustion residues from a power plant. (United States)

    Ram, L C; Masto, R E; Srivastava, N K; George, J; Selvi, V A; Das, T B; Pal, S K; Maity, S; Mohanty, D


    The presence of potentially toxic elements in lignite and coal is a matter of global concern during energy extraction from them. Accordingly, Barsingsar lignite from Rajasthan (India), a newly identified and currently exploited commercial source of energy, was evaluated for the presence of these elements and their fate during its combustion. Mobility of these elements in Barsingsar lignite and its ashes from a power plant (Bikaner-Nagaur region of Thar Desert, India) is presented in this paper. Kaolinite, quartz, and gypsum are the main minerals in lignite. Both the fly ash and bottom ash of lignite belong to class-F with SiO₂ > Al₂O₃ > CaO > MgO. Both the ashes contain quartz, mullite, anhydrite, and albite. As, In, and Sr have higher concentration in the feed than the ashes. Compared to the feed lignite, Ba, Co, U, Cu, Cd, and Ni are enriched (10-5 times) in fly ash and Co, Pb, Li, Ga, Cd, and U in bottom ash (9-5 times). Earth crust-normalization pattern showed enrichment of Ga, U, B, Ag, Cd, and Se in the lignite; Li, Ba, Ga, B, Cu, Ag, Cd, Hg, Pb, and Se, in fly ash; and Li, Sr, Ga, U, B, Cu, Ag, Cd, Pb, and Se in bottom ash. Hg, Ag, Zn, Ni, Ba, and Se are possibly associated with pyrite. Leaching test by toxicity characteristic leaching procedure (TCLP) showed that except B all the elements are within the safe limits prescribed by Indian Standards. PMID:25446718

  13. The post-collisional volcanism of northern Tunisia: Petrology and evolution through time (United States)

    Halloul, Néji; Gourgaud, Alain


    The Neogene volcanism of Tunisia is bimodal, comprising both mafic lavas and rhyolites. The rhyolites occur as domes and related breccias, and as dykes in the Nefza area, associated with an albite granite. The rhyolites volcanics are 12.9-8.2 Ma. Mafic lavas occur in the Nefza and Mogods areas, as dykes and sills, and are younger than the felsic lavas at 8.4-5 Ma. The rhyolites exhibit phenocrysts of quartz, plagioclase (An 25-55), alkali feldspar (Or 63-91), biotite, Fe-Ti oxides and rare cordierite and tourmaline. A study of the cordierite shows it to be magmatic in character, in equilibrium with glass and other minerals, and with a large range of compositions (Fe * 34-64). Magmatic cordierite in rhyolites is exceptional and cordierite/liquid partition coefficients were determined for rare earth elements. According to mineralogical and geochemical data, including Sr isotopes, there are two groups of rhyolites. The first group is the cordierite bearing-rhyolites, which have Fe-rich biotite, and is related to localised crustal melting. The second group, which lack cordierite, but has Mg-rich biotite, is related to AFC processes. The mafic magma is represented by moderately Na-alkaline silica undersaturated hawaites and mugearites, with phenocrysts of olivine (Fo 69-85), plagioclase (An 49-67), clinopyroxene (augite) and ulvöspinel. Geochemical data suggest that they are transitional in nature, between calc-alkaline and alkaline magmas, as also found in Algeria and Morocco. These magmas evolved by fractional crystallization and crustal contamination. The magmatic change through time from calk-alkaline to transitional, as also found for Algeria and Morocco at the same point in time, is consistent with a slab breakoff process. The more recent mafic magmas are related to an extensional post-collisional environment.

  14. Isotope geochemistry of drainage from an acid mine impaired watershed, Oakland, California

    International Nuclear Information System (INIS)

    Oxidation of sulfides at the Leona Heights Sulfur Mine has resulted in the liberation of acid, SO4 and metals to Leona Creek. Previous research at the site has indicated Fe(II) oxidation at rates faster than would be predicted by abiotic oxidation alone, particularly in the segment of stream between the Adit and Leona Street sample stations. In order to assess the mechanisms responsible for sulfide oxidation, samples were collected for isotopic analysis of water and SO4, the results of which were used to develop a stoichiometric isotope-balance model. This exercise indicated that the percentage of water-derived oxygen in SO4 increased spatially from between 56% and 64% at the Adit to between 71% and 72% at Leona Street, illustrating that increased sulfide oxidation via Fe(III) was occurring within, or as water flows over, the waste rock, relative to water emanating directly from the former mine. The incorporation of water-derived oxygen in SO4 during pyrite oxidation is a process controlled by Fe oxidizing bacteria such as A. ferrooxidans at low pH. The role of bacteria was further supported by estimates of the rate constant for Fe oxidation between sampling stations, yielding values that were approximately 106 faster than abiotic Fe oxidation alone. Stable isotopic analysis of water further indicates a close correlation of adit spring water to the local meteoric water line, while 3H data indicate a groundwater apparent age, or time of travel from its primary zone of recharge, of 34S data, in conjunction with reported albitized feldspars within the Leona Rhyolite host rock, indicate a magmatic origin of ore sulfur, contrary to previous interpretations at the site

  15. Process optimization of reaction of acid leaching residue of asbestos tailing and sodium hydroxide aqueous solution

    Institute of Scientific and Technical Information of China (English)

    DU GaoXiang; ZHENG ShuiLin; DING Hao


    Silica is the major component of the acid leaching residue of asbestos tailing. The waterglass solution can be prepared by the reaction of the residue with sodium hydroxide aqueous solution. Compared to the high temperature reaction method, this process is environmental friendly and low cost. In this paper, the reaction process of the residue and the sodium hydroxide aqueous solution is optimized. The op-timum reaction process parameters are as follows: the usage of sodium hydroxide is 26.4 g/100 g acid leaching residue, the reaction temperature is 90℃, the reaction time is 1 h, and the ratio of the liq-uid/solid is 2.0. The significance sequence of the process parameters to the alkali leaching reaction effect is the usage of sodium hydroxide > the ratio of the liquid/solid > the reaction time > the reaction temperature. The significance sequence to the leaching ratio of SiO2 is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. The significance sequence to the modulus of the sodium silicate is the ratio of the liquid/solid > the usage of sodium hydroxide > the reaction time > the reaction temperature. Under the optimum conditions, the leaching ratio of the SiO2 is 77.5%, and the modulus of the sodium silicate is 3.15. The XRD analysis result indicates that the major components of the alkali leaching residue are serpentine, talc, quartz and some albite.

  16. Microtectonic-assisted P-T determination on low-grade Alpine metamorphic rocks from the "Tisia Mega-Unit" of the Slavonian Mountains in Croatia (United States)

    Balen, Dražen; Lihter, Iva; Massonne, Hans-Joachim


    The internal structure of the Tisia (Tisza) Mega-Unit in the Alpine-Carpathian-Dinaridic orogenic system encompasses large Alpine nappe systems brought to its present-day position by complex regional-scale movements. The Slavonian Mountains are part of the Bihor nappe system which is below the Codru and above the Mecsek nappe systems. The low-grade metamorphic schist unit of the Slavonian Mountains includes numerous rocks which were previously related to Precambrian and/or Lower Paleozoic orogeneses. However, recent studies (e.g. Balen, 2014, European Geosciences Union General Assembly, EGU 2014-6122) show that the metapelites of this unit should be attributed to the Alpine orogeny and the poorly known P-T conditions, which they experienced, should be refined. Although metapelites can be sensitive to changes of metamorphic conditions and, therefore, be suitable for the P-T estimation of metamorphic event(s), the extraction of mineral assemblages, being in equilibrium, and associated microtectonic data for particular low-grade metamorphic rocks is not straightforward. On the contrary, due to lack of suitable minerals and complex mictotectonic features, one can be faced with a severe problem concerning (dis)equilibrium. To avoid this, the observation scale in the research was set to the sub-mm level taking into account microtectonic positions of minerals. The investigated samples from the Slavonian Mountains are fine-grained schists consisting of chlorite (15-30 vol. %), white mica (15-25 vol. %), quartz (10-25 vol. %), feldspars (albite 10-15 vol. %; some K-feldspar), biotite (Financial support by the Croatian Science Foundation (IP-2014-09-9541) and T. Theye's help during microprobe work is greatly acknowledged.

  17. Gold mineralisation near the Main Divide, upper Wilberforce valley, Southern Alps, New Zealand

    International Nuclear Information System (INIS)

    Veins up to 8 m wide fill extensional fractures in Torlesse Terrane metasediments near the Main Divide in the upper Wilberforce valley, Canterbury, New Zealand. The upper Wilberforce veins are part of a prominent 40 km long, NNE-trending swarm of gold-bearing veins formed across the Main Divide during the Late Cenozoic rise of the Southern Alps. The veins occur within, and near, a prominent set of faults which constitute the Main Divide Fault Zone. The veins are irregular in shape due to contrasting host rock properties, and have been only weakly sheared and deformed. Veins cut across greywacke beds and follow irregularly along argillite beds, on the 1-10 m scale. Quartz dominates vein mineralogy, but albite forms up to 45% of some veins, and minor chlorite, pyrite, arsenopyrite, chalcopyrite, and gold occur sporadically, especially in breccias near vein margins. Fluid inclusions in vein quartz homogenise at 180-253 degrees C, and arsenopyrite composition (28.3-30.8 at.% As) suggest formation temperatures of 250-350 degrees C. Elevated arsenic levels (up to 200 ppm above a background of 10 ppm) in some host greywackes and argellites suggest that hydrothermal activity pervaded host rocks as well as forming veins, but there is no textural evidence for this fluid flow. Late-stage carbonates in faults adjacent to the quartz veins, but which postdate the quartz veins, have δ18O ranging from 11.1 to 25.6 per thousand, and δ13C ranging from -12.5 to -1.1 per thousand. These carbonates were deposited by a mixture of meteoric and crustally isotopically exchanged fluid as a shallow-level manifestation of the same hydrothermal system which deposited the quartz veins. The upper Wilberforce veins structurally and mineralogically resemble some Late Cenozoic gold-bearing vein systems in the Mt Cook area, 100 km to the southwest along the Southern Alps. (author). 52 refs., 9 figs., 3 tabs

  18. Structure and geochemistry of the Rise and Shine Shear Zone mesothermal gold system, Otago Schist, New Zealand

    International Nuclear Information System (INIS)

    The Rise and Shine Shear Zone is a late metamorphic deformation zone developed in biotite zone Textural Zone 4 schist in Central Otago. The shear zone has been hydrothermally altered, with addition of gold associated with replacement of schist minerals by pyrite and arsenopyrite. Hydrothermal alteration of schist during mineralisation involved replacement of titanite by rutile, recrystallisation of metamorphic quartz, muscovite and chlorite, and addition of ankerite. Mineralised schist has abundant microshears that have developed parallel and subparallel to the pervasive schist foliation, and these microshears contain much of the hydrothermal sulfides and gold. Microshears have been deformed locally by upright syn-mineralisation brittle reverse faults and angular folds that have a southerly axial trend. These more brittle deformation zones are confined to the Rise and Shine Shear Zone. Gold-bearing veins and mineralised breccias, made up of quartz, albite, pyrite, arsenopyrite, calcite, and chlorite, fill extensional sites associated with upright fold zones. Calcite delta18OVSMOW from these late-stage mineralised veins ranges from +7 to +15 per mille and δ13CPDB from -5.3 to -6.6 per mille, are similar to many other gold-bearing vein systems in Otago, but are distinctly different from the Macraes deposit. Mineralisation occurred near to the brittle/ductile transition, at 200-400 degrees C. The upper part of the shear zone was truncated by a shallow northeast-dipping normal fault, the Thomsons Gorge Fault, which juxtaposed shear zone rocks against unmineralised Textural Zone 3 chlorite zone rocks in the middle Cretaceous. The Rise and Shine Shear Zone has some structural and geochemical features in common with the Hyde-Macraes Shear Zone, but also some important differences, and is not a simple strike-extension of that structure. (author). 46 refs., 9 figs., 3 tabs

  19. A modeling study of the long-term mineral trapping in deep saline marine sands aquifers (Invited) (United States)

    Aagaard, P.; Pham, V.; Hellevang, H.


    Simulation of geochemical processes due to CO2 injection and storage are dependent on sediment petrography and the kinetics of mineral fluid reactions. Mineral trapping of CO2 in the Utsira sand and similar marine sand reservoirs have been revisited based on critical review of rate data and geochemical constraints on formation waters. Reaction paths calculations were done with the PHREEQC modeling software at relevant reservoir conditions covering a temperature range of 30-100 °C and corresponding reservoir pressures. Initial CO2 saturation was determined by the fluid fugacity corresponding with reservoir conditions. The mineral dissolution kinetics was expressed with a chemical affinity term (Aagaard & Helgeson,1982) while a critical super-saturation for mineral growth was included in the precipitation rate expression. The redox conditions and the H2S fugacity in the simulations were constrained by the acetic/propionic acid buffer trend and the magnetite-pyrite buffer (Aagaard et al. 2001) respectively. We used a revised mineralogical composition for the Utsira sand also performed a sensitivity analyses with respect to mineral content. The simulations were run over a period of 10000 years. The main simulation results included dissolution of glauconite, smectite, pyrite, muscovite and albite, with precipitation of the carbonates siderite, ankerite, and minor dawsonite, as well as kaolinite, silica (either chalcedony or quartz), and K-feldspar. The uncertainties in the simulations are specially connected with initial mineral abundances. The effect of critical super-saturation and reactive surface area for precipitation needs to be further evaluated and tested. Aagaard, P. and H.C. Helgeson (1982). Thermodynamic and Kinetic Constraints on Reaction Rates among Minerals and Aqueous Solutions. I. Theoretical Considerations. Am. J. Sci., v. 282, p. 257-285. P. Aagaard, J. Jahren & S.N. Ehrenberg (2001) H2S controling reactions in clastic hydrocarbon reservoirs from the

  20. Leaching kinetics in cyanide media of Ag contained in the industrial mining-metallurgical wastes in the state of Hidalgo, Mexico

    Institute of Scientific and Technical Information of China (English)

    Juan Hernandez⇑; Francisco Patino; Isauro Rivera; Iván Alejandro Reyes; Misrael Uriel Flores; Julio Cesar Juarez; Martín Reyes


    The leaching kinetics in cyanide media of the silver contained in the Dos Carlos waste tailings at the City of Pachuca de Soto, Hidalgo State, Mexico were carried out. The used material contained the following chemical composition: 56 ? 10-6 of Ag, 0.6 ? 10?6 of Au and 70.43% (by weight) of SiO2; 7.032% (by weight) of Al2O3; 2.69% (by weight) of Fe; 0.46% (by weight) of Mn; 3.98% (by weight) of K2O; 3.34%(by weight) of CaO;2.50% (by weight) of Na2O;0.04% (by weight) of Zn;0.026%(by weight) of Pb. The mineralogical phases present were the following:Silica, albite, argentite, berlinite, orthoclase, potassium jarosite, and natrojarosite. In the leaching kinetics in cyanide media, and under the studied conditions, the effect of the CN? concentration on the reaction rate has no effect on the whole process of alkaline cyanidation, of which the reaction order is n ? 0. Temperature has an effect on the cyanidation rate of the reaction, with an activation energy of 47.9 KJ/mol. At the same time, when the particle size decreases there is an increase in the reaction rate, which is inversely proportional to the particle diameter;when increasing the NaOH concentration there is an increase in the reaction rate Kexp, with a reaction order (n) of 0.215 under the studied ranges.

  1. Subsolidus alkali metasomatism in the metamorphosed Ordovician acid volcanics and volcaniclastics of the Gelnica Group (Gemeric Superunit, Western Carpathians

    Directory of Open Access Journals (Sweden)

    Mária Šimurková


    Full Text Available The Early Paleozoic Gelnica Group (Gemeric Superunit, Western Carpathians is composed of low-grade metamorphosed flysch-like sedimentary complexes alternated with volcanogenic complexes built up mostly by acid volcaniclastic rocks. Volcaniclastic rocks and small rhyolite bodies Ordovician in age underwent subsolidus alkali metasomatism locally overprinted by multiple stages of younger metamorphic and hydrothermal alterations. The observed variability in chemical compositions indicates that the most of acid volcanic and volcaniclastic rocks experienced potassic or sodium metasomatic alteration, the unaltered or Mg-metasomatised rocks occur less frequently. The dominating K-metasomatism is related mainly to the K-feldspar, partly also biotite and muscovite/sericite formation at the expense of matrix or original feldspar phenocrysts. The Na-metasomatism is connected with albite formation. The highest concentrations of alkalies (up to 13.52 wt. % K2O and 7.08 wt. % Na2O respectively have been found in rocks originally represented by glassy dacites. The elements like Al, Ti and Zr remain immobile in alkaline metasomatic processes in contrast to Rb or metals. Based on the results from areas with analogical geological structure and evolution, especially the Bergslagen area in Sweden, we suppose that alkali metasomatism in the Gelnica Group is a product of hydrothermal system caused by the infiltration and circulation of sea water. The areas with K-, Na- or Mg-metasomatism represent different parts of the original hydrothermal system, where the K-metasomatism was probably its lower temperature section. This hydrothermal system probably mobilised some metals (Cu, Pb, Zn, Fe, Mn for the formation of stratiform sulfide and oxide mineralizations or served as the metal pre-concentrator for younger siderite-sulfide vein deposits.

  2. Recuperation of infrared stimulated luminescence of feldspars

    International Nuclear Information System (INIS)

    After bleaching the optically stimulated luminescence (OSL) signal to a low residual level, the signal has been found to increase during subsequent storage or preheating. This effect is well known in quartz as ''recuperation of OSL after bleaching'' (Aitken, M.J., Smith, B.W., 1988. Optical dating: recuperation after bleaching. Quat. Sci. Rev. 7. 387-393.). A better understanding of recuperation in feldspars could help the dating specialist, because this process might be different from the recuperation observed in quartz. This paper highlights a few examples of a larger study, which cannot be shown here in complete detail. We carried out a recuperation study of infrared-stimulated luminescence (IRSL) of different feldspars from a mineral collection, mainly alkali feldspars and one albite. The samples were irradiated with doses of 200, 1000 and 2500 Gy in a 60Co gamma cell. Subsequently, the samples were stored in the dark at room temperature (3 weeks up to 6 months, depending on the applied dose), so that the very intense irradiation-induced phosphorescence can decrease for many orders of magnitude. The emitted OSL was measured through detection filters also used in dating (Schott UG 11, Hoya U 340 for detection of near UV-emissions and Schott BG 39 for detection in the visible range). Recuperation times up to 100 days were used. The recuperated-OSL emissions were measured either with the optical filters mentioned above or with a modified experimental set-up using a variable interference filter with a continuous detection range from 400 to 700 nm. In some feldspars very intense recuperation signals (up to 100% and more of the initial signal) were observed when optical stimulation was performed with IR and broadband detection using the BG 39 or when detection was carried out in the near ultraviolet region. The IRSL emissions at 410 and 560 nm, measured with the interference filter, showed no recuperation despite a clearly detectable first shine-down

  3. Gold-quartz vein deposition in an uplifted blueschist terrane, Seward Peninsula, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Read, J.J.


    The Big Hurrah mine, located on the Seward Peninsula, Alaska, consists of gold-quartz-carbonate veins which cut sheared carbonaceous metasedimentary and metavolcanic rocks. The rocks underwent regional syn-kinematic blueschist facies metamorphism in the Jurassic. Glaucophane in metabasite and mafic and pelitic schists has been reported from the central Seward Peninsula. Chlorite+/-epidote+/-albite+/-paragonite pseudomorphs after lawsonite and glaucophane have also been reported. The replacement of these blueschist facies minerals probably occurred during uplift and retrogradation of the terrane. The veins at Big Hurrah range from early, concordant metamorphic quartz lenses to discordant tension veins to discontinuous quartz-Au lodes which occur in sheared zones cross-cutting the foliation. The veins are thought to have formed during the late stages of shearing and uplift. Fluid inclusions in the veins are similar to those found in metamorphic rocks in that they are small, most are secondary, and may contain CO/sub 2/ and CH/sub 4/. The is evidence for CO/sub 2/-CH/sub 4//H/sub 2/O liquid immiscibility. Pressure estimates of 0.8 kbar were calculated from coexisting CO/sub 2/-CH/sub 4/ and aqueous inclusions. Pressure corrected homogenization temperatures for quartz deposition are in the range 300-400/sup 0/C. Hence, the veins were deposited at lower pressures and temperatures than those of the blueschist facies event. It is thought that the veins at Big Hurrah were formed during uplift by a fluid phase derived by metamorphic dehydration and channeled into conduits depositing quartz, carbonate and gold.

  4. Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California (United States)

    Moore, Diane E.; Liou, J.G.; King, B.-S.


    As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

  5. Structural and metamorphic evidence for the mechanism of exhumation of the schist belt, south-central Brooks Range, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Dinklage, W.S.; Patrick, B.E. (Univ. of California, Santa Barbara, CA (United States). Dept. of Geologic Sciences)


    The mid to late mesozoic Brookian orogeny involved southward subduction underneath an island arc and subsequent burial of a passive continental margin. Field mapping, petrography, and geochronology of blueschist-bearing metasedimentary rocks in the Walker Lake region of the southern Brooks Range enables correlation of fabrics with crustal movements that are responsible for their burial and exhumation. Observed early ductile fabrics in the schist belt are consistent with north-vergent transport. These fabrics include (1) S[sub D] (dominant foliation), a south-dipping transposed crenulation cleavage which formed under blueschist facies conditions; (2) outcrop-scale north-vergent folds and an associated mesoscopic south-dipping crenulation cleavage, S[sub D+1]; (3) kilometer-scale gentle warps and north-vergent, open monoclinal folds. Small north-vergent folds (fabric 2) fold an earlier mineral stretching lineation associated with S[sub D]. The similarity of orientation of the three fabrics and their evolution in time from small and isoclinal to large and open suggests that they are the product of progressive deformation. S[sub D] is likely a burial fabric; later fabrics may be related to uplift along a regionally penetrative system of ductile, north-vergent south-dipping thrusts. A metamorphic overprint, dated at 105--110 Ma, increases to amphibolite facies toward the north and outlasts north-vergent fabrics. Retrograde helicitic albite is commonly rotated by later minor extensional crenulation cleavages. Discrete, narrow zones of ductile deformation in the southernmost schist belt, parallel to S[sub D] but postdating blueschist facies conditions, locally exhibit top-to-the-south sense of shear. This evidence suggest that north-vergent contraction continued during exhumation of the schist belt from deep to mid-crustal levels and that extension may have been responsible for exhumation from middle to shallow crustal levels.

  6. Petrology and structure of greenstone blocks encased in mud-matrix melange of the Franciscan complex near San Simeon, California

    Energy Technology Data Exchange (ETDEWEB)

    Davidsen, R.K.; Cloos, M.


    Greenstones comprise about 20% of all mappable (>1 m) blocks encased in blueschist-block-bearing mud-matrix melange exposed in a 10 km-length of sea cliffs near San Simeon. Field and petrographic analysis of 25 blocks show they vary from finely crystalline (<1 mm) locally porphyritic or amygdaloidal, volcanics to coarsely crystalline (1 to 5 mm) diabase. Some are in contact with bedded chert and two have relict pillows. However, most blocks are intensely deformed. Pinch-and-swell and boundinage are recognized on scales from cm to about 10 m. Distortion was accommodated by cataclasis to an aggregate of pieces from mm to m across. Generally, m-sized blocks are pervasively cataclastic whereas larger blocks are crosscut by cataclastic zones that emanate from pervasively cataclastic margins or necked regions of boudins. Discontinuous, cm-thick veins and cavities that are lined by quartz and clacite and rarely, laumontite, prehnite and aragonite locally crosscut all other structures. Relict igneous textures show the primary minerals are plagioclase and clinopyroxene. Abundant secondary minerals, particularly in cataclastic zones, are albite, chlorite, pumpellyite (some have high Al), and calcite. The metamorphic parageneses indicate relatively minor greenschist-facies, sea-floor-type alterations under static conditions followed by lower-temperature alterations synchronous with cataclasis and the development of boudinage. If the blocks are fragments of disrupted ophiolites, only the uppermost section of the suite are present within the mud-matrix melange near San Simeon. The simplest explanation for their crystallization, metamorphism and incorporation into the melange is that they are fragments of seamounts dismembered during subduction.

  7. Geochronology of blueschists from west-central Baja California and the timing of uplift in subduction complexes

    Energy Technology Data Exchange (ETDEWEB)

    Baldwin, S.L.; Harrison, T.M. (Dept. of Geol. Sciences, Albany, NY (USA))


    A geochronologic study of blueschists from west-central Baja California has provided constraints on the timing of high-pressure, low-temperature metamorphism and the subsequent uplift of this subduction complex. Mineral separates from coherent blueschists and blueschist blocks enclosed in serpentinite melange were analyzed by {sup 40}Ar/{sup 39}Ar, fission track, and Rb/Sr methods. {sup 40}Ar/{sup 39}Ar age spectra for white mica separated from four blueschist blocks and an overprinted eclogite block in serpentinite-matrix melange show slow cooling gradients between 115-95 Ma. Rb/Sr apparent ages for one block are concordant with these results. {sup 40}Ar/{sup 39}Ar ages of blue amphibole are primarily the result of the degassing of white mica intergrowths as confirmed by microprobe analyses. Apatite fission track ages indicate a blueschist block and an eclogite block cooled to a temperature below {approximately}100 C at 22 Ma and 32 Ma, respectively. Subduction-related metamorphism of the coherent blueschists occurred in late Early Cretaceous time, based on a {sup 40}Ar/{sup 39}Ar age or 109 Ma for metamorphic white mica from a metasandstone. {sup 40}Ar/{sup 39}Ar analysis of partially albitized K-feldspar from a plutonic clast in a metaconglomerate indicates this sample cooled to a temperature of {approximately} 145 C at approximately 20 Ma. Geochronologic and petrologic data for coherent blueschists indicate an average uplift rate of 0.1 mm/yr for one portion of the subduction complex. The relatively slow uplift rate and lack of any higher temperature overprinting assemblages in the coherent blueschists suggest that synsubduction uplift was gradual and proceeded through a dynamic accretionary wedge characterized by low geothermal gradients. An increase in uplift rate (to 1.0 mm/yr) during post-Miocene time coincides with a change from a convergent to a transform plate boundary.

  8. Fluid-metapelite interaction in an ultramafic mélange: implications for mass transfer along the slab-mantle interface in subduction zones (United States)

    Mori, Yasushi; Shigeno, Miki; Nishiyama, Tadao


    The slab-mantle interface in subduction zones is a site of tectonic mixing of crustal and mantle rocks. It is the interface for fluid flow of slab-derived components into the mantle wedge. To assess the fluid-rock interaction along the slab-mantle interface, we studied the bleaching of pelitic schist in an ultramafic mélange. The Nishisonogi metamorphic rocks in Kyushu, Japan, comprise ultramafic mélanges intercalated with epidote-blueschist facies schists. The ultramafic mélange consists of tectonic blocks of various lithologies and a matrix of chlorite-actinolite schist and serpentinite. Along the contact with the mélange matrix, pelitic schist blocks are bleached mainly due to the modal increase of albite and the consumption of carbonaceous material. The bleaching is probably attributed to infiltration of Na-rich external fluid from the mélange matrix. Mass balance analysis indicates losses of C, Rb, K2O, Ba, Pb, and SiO2 from the bleached pelitic schist, although Al2O3, TiO2, Sc, Y, Zr, Nb, La, Ce, and Nd remain immobile. This suggests fractionation of large-ion lithophile elements (LILE) and Pb from the high-field-strength elements and rare earth elements during the bleaching. If this ultramafic mélange is analogous to the slab-mantle interface, similar infiltration metasomatism will promote liberation of C, Si, LILE, and Pb from subducting metapelites and enhance metasomatism of the mantle wedge.

  9. Age, protoliths and tectonic implications of the Toudaoqiao blueschist, Inner Mongolia, China (United States)

    Miao, Laicheng; Zhang, Fochin; Jiao, Shujuan


    The Toudaoqiao blueschist is located in the northern Great Xing'an Range of China, part of the eastern Central Asian Orogenic Belt, and was discovered in the 1980s, but the age of its formation and metamorphism and the nature of its protolith, have long remained uncertain. Thin-section examination and microprobe analyses show that the Toudaoqiao blueschist has a mineral assemblage of sodic amphibole + chlorite + epidote + albite + phengite ± apatite ± quartz. Electron microprobe analyses attest that sodic amphibole is magnesioriebeckite in composition. The blueschist-facies metamorphism occurred under metamorphic P-T conditions of ∼7 kbar and 450-480 °C, estimated from pseudosection as well as the compositions of the Na-amphibole and phengite. The protolith of the blueschist is mainly composed of alkali basalt, with a minor amount of tholeiitic basalt. The alkali basalt shows similarities in chemical composition to oceanic island basalt (OIB), suggesting derivation from an OIB-like asthenospheric mantle source in a within-plate setting. The tholeiitic basalt has geochemical features transitional between mid-ocean ridge basalt and island arc tholeiite, which implies an origin from a depleted mantle source that would have been selectively metasomatized in a supra-subduction setting. Sensitive high resolution ion microprobe (SHRIMP) zircon dating confirms that the protolith of the Toudaoqiao blueschist formed at 516 ± 11 Ma, in the middle Cambrian, and experienced blueschist facies metamorphism during the Silurian at ca. 436 Ma. The juxtaposition of the two distinct rock types and the association of the blueschist with mélange suggest that the origin of the Toudaoqiao blueschist belt involve collision-accretionary processes. Based on these new results and regional data, we propose that the Toudaoqiao blueschist belt represents the suture zone between the Erguna and Xing'an terranes and that suturing took place during the Early Silurian period. The southwestern

  10. Geochronology and geochemistry of the Yilan blueschists in the Heilongjiang Complex, northeastern China and tectonic implications (United States)

    Zhu, Chloe Yanlin; Zhao, Guochun; Sun, Min; Liu, Qian; Han, Yigui; Hou, Wenzhu; Zhang, Xiaoran; Eizenhofer, Paul R.


    The geological attraction of the Heilongjiang Complex, extending along a suture zone between the Jiamusi and Songliao blocks in Northeast China, resides in excellent exposures of blueschists, which occur in association with granitic gneisses, marbles, meta-ultramafic rocks, greenschists, quartzites, muscovite-albite schists and two-mica schists from the complex. However, controversy has long surrounded the ages and tectonic settings of mafic protoliths of the blueschists from the complex. The lithological association and major and trace element compositions indicate that the ultramafic-mafic protoliths of the Yilan blueschists can be subdivided into the tholeiitic and alkali groups, both of which were derived from partial melting of garnet-facies peridotites, but at different degrees of melting. Magmatic zircons from a tholeiitic blueschist sample yield a 206Pb/238U age of 275 ± 2 Ma, interpreted as its protolithic age. The sample also contains large amounts of older inherited zircons up to 1200 Ma, which, together with the geochemical features of the sample, indicate that the tholeiitic basalts were generated in a continental rift. The further development of the rift led to the formation of an ocean between the Jiamusi and Songliao blocks, in which some ocean islands developed, represented by the alkali mafic protoliths of the Yilan blueschists, as supported by geochemical data. Magmatic zircons from an alkaline mafic blueschist sample yield a 206Pb/238U age of 141.8 ± 1 Ma, indicating that the ocean between the Jiamusi and Songliao blocks had not been closed by ~ 141 Ma, not at 210-180 Ma as previously considered.

  11. Rocha com espodumênio como fundente para massas cerâmicas tradicionais Spodumene rock as a flux for traditional ceramic bodies

    Directory of Open Access Journals (Sweden)

    S. R. Bragança


    Full Text Available Investigou-se a atuação de uma rocha com espodumênio como fundente em massas cerâmicas, analisando-se sua reatividade com outras matérias-primas, como quartzo e caulim. Primeiramente, caracterizou-se petrograficamente o pegmatito de onde se extrai esse fundente. Posteriormente avaliou-se o comportamento de moabilidade, fundência e deformação piroplástica da rocha com espodumênio. Analisou-se então sua influência nas propriedades tecnológicas finais das peças, principalmente em relação à temperatura de queima, às fases e à microestrutura. Comparou-se a gresificação com outros fundentes comerciais como a albita e o feldspato. O espodumênio mostrou maior capacidade de reduzir a temperatura de gresificação das peças que os fundentes tradicionais, promovendo a densificação por fluxo viscoso.A spodumene rock was used as a flux in ceramic bodies, analyzing its reactivity to other raw materials such as quartz and kaolin. The petrology properties of the pegmatite (parent rock from which the flux is extracted was characterized. The grindability, fluxing strength and pyroplastic deformation of the spodumene rock were investigated. The influence on technological properties of the final pieces, mainly in relation to the firing temperature, phases formation and microstructure were also further analyzed. The firing behavior to other commercial flux such as albite and feldspar were then compared. The spodumene rock was considered an effective flux, capable of reducing the firing temperatures of the tested bodies by viscous flow.

  12. Cooling rates and crystallization dynamics of shallow level pegmatite-aplite dikes, San Diego County, California (United States)

    Webber, Karen L.; Simmons, William B.; Falster, Alexander U.; Foord, Eugene E.


    Pegmatites of the Pala and Mesa Grande Pegmatite Districts, San Diego County, California are typically thin, sheet-like composite pegmatite-aplite dikes. Aplitic portions of many dikes display pronounced mineralogical layering referred to as "line rock," characterized by fine-grained, garnet-rich bands alternating with albite- and quartz-rich bands. Thermal modeling was performed for four dikes in San Diego County including the 1 m thick Himalaya dike, the 2 m thick Mission dike, the 8 m thick George Ashley dike, and the 25 m thick Stewart dike. Calculations were based on conductive cooling equations accounting for latent heat of crystallization, a melt emplacement temperature of 650 °C into 150 °C fractured, gabbroic country rock at a depth of 5 km, and an estimated 3 wt% initial H2O content in the melt. Cooling to -5 cm/s. Crystal size distribution (CSD) studies of garnet from layered aplites suggest growth rates of about 10-6 cm/s. These results indicate that the dikes cooled and crystallized rapidly, with variable nucleation rates but high overall crystal-growth rates. Initial high nucleation rates coincident with emplacement and strong undercooling can account for the millimeter-size aplite grains. Lower nucleation rates coupled with high growth rates can explain the decimeter-size minerals in the hanging walls, cores, and miarolitic cavities of the pegmatites. The presence of tourmaline and/or lepidolite throughout these dikes suggests that although the melts were initially H2O-undersaturated, high melt concentrations of incompatible (or fluxing) components such as B, F, and Li (±H2O), aided in the development of large pegmatitic crystals that grew rapidly in the short times suggested by the conductive cooling models.

  13. Rare-element granitic pegmatite of Miocene age emplaced in UHP rocks from Visole, Pohorje Mountains (Eastern Alps, Slovenia): accessory minerals, monazite and uraninite chemical dating (United States)

    Uher, Pavel; Janák, Marian; Konečný, Patrik; Vrabec, Mirijam


    The granitic pegmatite dike intruded the Cretaceous UHP rocks at Visole, near Slovenska Bistrica, in the Pohorje Mountains (Slovenia). The rock consists mainly of K-feldspar, albite and quartz, subordinate muscovite and biotite, while the accessory minerals include spessartine-almandine, zircon, ferrocolumbite, fluorapatite, monazite- (Ce), uraninite, and magnetite. Compositions of garnet (Sps48-49Alm45-46Grs + And3-4 Prp1.5-2), metamict zircon with 3.5 to 7.8 wt. % HfO2 [atom. 100Hf/(Hf + Zr) = 3.3-7.7] and ferrocolumbite [atom. Mn/(Mn + Fe) = 0.27-0.43, Ta/(Ta + Nb) = 0.03-0.46] indicate a relatively low to medium degree of magmatic fractionation, characteristic of the muscovite - rare-element class or beryl-columbite subtype of the rare-element class pegmatites. Monazite-(Ce) reveals elevated Th and U contents (≤11 wt. % ThO2, ≤5 wt. % UO2). The monazite-garnet geothermometer shows a possible precipitation temperature of ~495 ± 30 °C at P~4 to 5 kbar. Chemical U-Th-Pb dating of the monazite yielded a Miocene age (17.2 ± 1.8 Ma), whereas uraninite gave a younger (~14 Ma) age. These ages are comtemporaneous with the main crystallization and emplacement of the Pohorje pluton and adjacent volcanic rocks (20 to 15 Ma), providing the first documented evidence of Neogene granitic pegmatites in the Eastern Alps. Consequently, the Visole pegmatite belongs to the youngest rare-element granitic pegmatite populations in Europe, together with the Paleogene pegmatite occurrences along the Periadriatic (Insubric) Fault System in the Alps and in the Rhodope Massif, as well as the Late Miocene to Pliocene pegmatites in the Tuscany magmatic province (mainly on the Island of Elba).

  14. Water management of the uranium production facility in Brazil (Caetite, BA): potential impacts over groundwater quality

    International Nuclear Information System (INIS)

    The uranium unit of Caetite - in charge of all the 'yellow cake' produced in Brazil - is located in the semi-arid Northeast region at Bahia State. The geological uranium content of the ore is 3000 ppm, which is mainly associated with albite (NaAlSi8O8), and its extraction is achieved by means of a Heap-Leach process. This process has a low water demand, which is supplied by a network of wells, but can contribute to change the groundwater quality and in some cases the extinguishing of wells was observed. The managing of liquid mining wastes formed by drainage waters from mine pit and solid waste piles is not enough to avoid unwarranted releases in the environment, which turn necessary the waste treatment through passing them into the industrial plant in order to reduce radionuclide concentrations. The groundwater is Na-HCO3 type water and relative high concentration of Cl are observed in some groundwater. It seems that levels of uranium in groundwaters are mainly a consequence of the complexation of the metal by carbonates (or other anions) and not by any sort of the contamination of these waters by the drainage accumulated in the open pit. The speciation modelling allows identifying some areas where the replenishment of the aquifer is more active, but in general the recharge is a fast process run by direct infiltration. The stable isotope data (δ2H and δ18O) showed that evaporation plays a role during the infiltration, causing the groundwater salinization. These data discard the possibility that groundwater salinization was caused by discharge of deeper saline groundwater through faults associated to a regional groundwater flow system. The presence of an active shallow groundwater flow system offers better possibility for sustainable use of the groundwater resources in this semi-arid region of Brazil. (author)

  15. Geochemical characteristics of pyrite in Duolanasayi gold deposit, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    CHEN Guodong; XIAO Huiliang; WANG Henian; ZHOU Jiyuan


    The Duolanasayi gold deposit, 60 km NW of Habahe County, Xinjiang Uygur Autonomous Region, is a mid-large-scale gold deposit controlled by brittle-ductile shearing, and superimposed by albitite veins and late-stage magma hydrothermal solutions. There are four types of pyrite, which are contained in the light metamorphosed rocks (limestone, siltstone), altered-mineralized rocks (chlorite-schist, altered albite-granite, mineralized phyllite), quartz veins and carbonatite veinlets. The pyrite is the most common ore mineral. The Au-barren pyrite is present mainly in a simple form and gold-bearing pyrite is present mainly in a composite form. From the top downwards, the pyrite varies in crystal form from {100} and {210}+{100} to {210}+{100}+{111} to {100}+{111}. Geochemical studies indicate that the molecular contents of pyrite range from Fe1.057S2 to Fe0.941S2. Gold positively correlates with Mn, Sr, Zn, Te, Pb, Ba and Ag. There are four groups of trace elements: Fe-Cu-Sr-Ag, Au-Te-Co, As-Pb-Zn and Mn-V-Ti-Ba-Ni-Cr in pyrite. The REE characteristics show that the total amount of REE (ΣREE) ranges from 32.35×10 -6 to 132.18×10 -6; LREE/HREE, 4.466-9.142; (La/Yb)N, 3.719-11.133; (Eu/Sm)N, 0.553-1.656; (Sm/Nd)N, 0.602-0.717; La/Yb, 6.26-18.75; δEu, 0.628-2.309; δCe, 0.308-0.816. Sulfur isotopic compositions (δ 34S=-2.46‰--7.02‰) suggest that the sulfur associated with gold mineralization was derived from the upper mantle or lower crust.

  16. Preferential Treatment: Interaction Between Amino Acids and Minerals (United States)

    Crapster-Pregont, E. J.; Cleaves, H. J.; Hazen, R. M.


    Amino acids are the building blocks of proteins and are important for some models of the origin of life. Polymerization of amino acids from dilute solution is unlikely without a scaffold or catalyst. The surfaces of early Earth minerals are the most likely candidates for this role. The surface adsorption behavior of 12 amino acids (L-alanine, L-serine, L-aspartic acid, L-proline, L- phenylalanine, L-valine, L-arginine, d-amino valeric acid, glycine, L-lysine, L-isoleucine, and B-alanine) on 21 minerals (quartz, calcite, enstatite, illite, olivine, pyrrhotite, pyrite, alkali basalt, albite, analcime, chlorite, barite, hydroxyl apatite, hematite, magnetite, aluminum hydroxide, kaolin, silica gel, corundum, rutile, and montmorillonite) was determined via batch adsorption experiments. Absorption was determined for concentrations between 10-4M and 10-6M in the presence of 0.1M NaCl, and between pH values of 3 and 9 at 25 degrees C. The equilibrated solutions were centrifuged, filtered, derivatized using a fluorescent amino group tag (dansyl-chloride) and analyzed by HPLC. Adsorption was standardized using BET surface area measurements for each mineral to give the number of mols of each amino acid adsorbed per square meter for each mineral. The results indicate an enormous difference in the adsorption of amino acids between minerals, along with major differences in the adsorption of individual amino acids on the same mineral surface. There is also a change in the absorbance of amino acids as the pH changes. Many previous studies of amino acid concentration and catalysis by minerals have used clay minerals because of their high surface areas, however, this data suggests that the surfaces of minerals such as calcite, quartz and pyrite have even higher affinities for amino acids. The results suggest mineral surfaces that could be optimal locations for the polymerization of molecules linked to the origin of life.

  17. Influence of moisture content on shearing strength of unsaturated undisturbed quaternary system middle pleistocene

    Institute of Scientific and Technical Information of China (English)

    钟祖良; 刘元雪; 刘新荣; 李小勇; 王睢


    The unsaturated undisturbed quaternary system middle pleistocene loess, a typical unsaturated soil, often occurs in the implementation of western development strategy. To obtain the shearing strength characteristics of this unsaturated undisturbed loess, based on the analysis of mineral composition, the triaxial shear test of undisturbed quaternary system middle pleistocene loess under different moisture contents is conducted with the specialized triaxial instrument for unsaturated soil. The test results show that the mainly mineral composition of undisturbed quaternary system middle pleistocene loess is quartz and albite. Under the same confining pressure, the matric suction increases with the decrease of moisture content. The smaller the moisture content, the larger the matric suction; the higher the moisture content, the lower the matric suction. Under the same moisture content, the matric suction increases with the confining pressure and reaches a maximum when the confining pressure is 100 kPa, and then decreases with the increase of confining pressure. This phenomenon is closely related to the grain contact tightness of soil mass under high confining pressure. According to the triaxial test of loess, the sample of loess experiences 4 stages from loading to failure: 1) compaction stage; 2) compression stage; 3) microcrack developing stage; 4) shear failure stage. The test sample is of brittle failure (weak softening) under low moisture content and confining pressure. With the decrease of matric suction and the increase of consolidated confining pressure, the stress−strain curve changes from softening type to ideal plastic type. In the shearing strength parameters of unsaturated undisturbed loess, the influence of moisture content on internal friction angle is small, but that on cohesive force is obvious. Therefore, the shearing strength of unsaturated undisturbed loess is higher than that of saturated undisturbed loess and varies with the moisture content.

  18. Influence of spectral interferences on the results of quartz determination by infrared spectrometry

    Directory of Open Access Journals (Sweden)

    Aleksandra Maciejewska


    Full Text Available Background: Determination of quartz by Fourier transform infrared spectrometry (FTIR is not specific: the obtained results are influenced by matrix components, some of which cause spectral interference. The aim of the study was to evaluate the effect of dust components responsible for spectral interference with quartz on the results of its determinations, and to develop methods to minimize the effects of interferences. Material and Methods: Investigation of interferent effects were conducted using respirable dusts: quartz SRM 1878a, cristobalite SRM 1879a, synthetic amorphous silica (Zeosil and feldspar, albite and kaolinite. For the study 17 mixtures with quartz and interferents at concentrations from 10 to 90% were prepared. Determinations of quartz were carried out by the KBr disc method. Results: In mixtures of quartz with interferents, the results based on bands 798–779 cm–1 were overestimated by 10–55%, while those based on band 695 cm–1 were closer to the true content of quartz. It was found that the best methods able to decrease the impact of spectral interference are: scaled subtraction of IR spectra of feldspar or kaolinite analysed in nonashed samples, correction curve for kaolinite also investigated in nonashed samples with quartz-content calculation based on band 695 cm–1 in mixtures with cristobalite, amorphous silica or kaolinite in ashed samples. Conclusions: The study indicates the need to identify spectral interferences in dust when determining crystalline silica by FT-IR and to take actions to minimize their impact on the obtained results. Med Pr 2015;66(4:497–509

  19. Preliminary stratigraphic and petrologic characterization of core samples from USW-G1, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Waters, A.C.; Carroll, P.R. (eds.)


    Tuffs of the Nevada Test Site are currently under investigation to determine their potential for long-term storage of radioactive waste. As part of this program, hole USW-G1 was drilled to a depth of 6000 ft below the surface, in the central part of the Yucca Mountain area, Nevada Test Site, Nevada. Petrographic study of the USW-G1 core is presented in this report and shows the tuffs (which generally were variably welded ash flows) are partly recrystallized to a variety of secondary minerals. The important alteration products are zeolites (heulandite, clinoptilolite, mordenite and analcime), smectite clays with minor interstratified illite, albite, micas, potassium feldspar, and various forms of silica. Iijima`s zeolite zones I through IV of burial metamorphism can be recognized in the core. Zeolites are first observed at about the 1300-ft depth, and the high-temperature boundary of zeolite stability in this core occurs at about 4350 ft. Analcime persists, either metastably or as a retrograde mineral, deeper in the core. The oxidation state of Fe-Ti oxide minerals, through most of the core, increases as the degree of welding decreases, but towards the bottom of the hole, reducing conditions generally prevail. Four stratigraphic units transected by the core may be potentially favorable sites for a waste repository. These four units, in order of increasing depth in the core, are (1) the lower cooling unit of the Topopah Spring Member, (2) cooling unit II of the Bullfrog Member, (3) the upper part of the Tram tuff, and (4) the Lithic-rich tuff.

  20. 深处岩浆分异与某地花岗伟晶岩的形成

    Institute of Scientific and Technical Information of China (English)



    Two stages of intrusion have been recognized for Paleozoic pegmatites in this district. The pegmatites occur as several thousands of dikes, with 84 per cent of them distributed within three “thickly concentrated areas”. Similar horizontal zoning, i.e.,from the parental granite outwards the pegmatites vary from type K through type Na to type Li, is observed within these “thickly concentrated areas”, which consist of pegmatites of different stages. Temporally, the pegmatites also evolve in the same sequence of types K-Na-Li, with a series of mineralized dikes produced during this process. The occurrence of this phenomenan is not accidental but a strong indication of deepseated magmatic differentiation. In nature, not all granitic magmatism can bring about pegatite emplacement,nor all the pegmatite dikes are of the same petrological character. These differences indicate that deep-seated magmatic differentiation must be controlled by some factors.It's development is believed to be dependent largely on the amounts of both parental and residual magmas and on the extent to which the pressure at their source region has been lowered by the intrusion of granite. The constant movement of the crust results in the continuous upward migration of differentiated magma, so as to promote the differentiation to a greater extent, thereby providing new source materials for subsequent intrusive activity. Such a continuous movement of opposites leads to the formation of a complete series of pegmatites, i.e., from biotite-microcline pegmatite to lepidolite-albite pegmatite, giving rise to the “thickly concentrated areas” as well as a series of mineralized veins.

  1. Geochemical characteristics of phenocryst feldspar in alkaline basalts from site Hajnacka

    International Nuclear Information System (INIS)

    Current research of the feldspar megacrysts was aimed to obtain a new knowledge about the geochemical properties of these crystals, their classification and by using of oxygen isotopes to get a rough idea about the source region, the origin of their occurrence. The basic chemical composition of the crystals was measured at the University of Vienna by EMP - WDS method in a scale of silicate analysis with extra detection of BaO and SrO. Oxygen isotopes (δ18O) were obtained by ICP-MS, the mass spectrometer at George-Auguste University at Goettingen. SiO2 contents were determined for all samples > 60.0 wt. % Al2O3 content of about 20 wt . % in average. Inter-resting contents were CaO (SrO) - Na2O - K2O (BaO), which also defined classification into the feldspar groups - plagioclase ( albite ) with the transition into the K - feldspar (orthoclase ). There was also a documentation of the substitution between K ↔ Na (± Ca ). Oxygen isotope values for all three samples ranged from 4.8 after 6.2 o/oo - SMOW . These values are within tolerance of +5.5 o/oo δ18O defined in average for mantle materials . On the basis of these data, we can conclude that feldspar crystallized under the chemical composition exchanging of the melt of the source, that means in an environment with a control mechanism of fractional crystallization, while the conservation of the isotopic composition of the crystals rested in limits of the primary magmatic reservoir. (authors)

  2. Metamorphic Evolution of Garnet-bearing Epidote-Barroisite Schist from the Meratus Complex in South Kalimantan, Indonesia

    Directory of Open Access Journals (Sweden)

    Nugroho Imam Setiawan


    Full Text Available This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristics by using polarization microscope and electron probe micro analyzer (EPMA. Furthermore, the pressure-temperature path of garnet-bearing epidote-barroisite schist was estimated by using mineral parageneses, reaction textures, and mineral chemistries to assess the metamorphic history. The primary stage of this rock might be represented by the assemblage of glaucophane + epidote + titanite ± paragonite. The assemblage yields 1.7 - 1.0 GPa in assumed temperature of 300 - 550 °C, which is interpreted as maximum pressure limit of prograde stage. The peak P-T condition estimated on the basis of the equilibrium of garnet rim, barroisite, phengite, epidote, and quartz, yields 547 - 690 °C and 1.1 - 1.5 GPa on the albite epidote amphibolite-facies that correspond to the depth of 38 - 50 km. The retrograde stage was presented by changing mineral compositions of amphiboles from the Si-rich barroisite to the actinolite, which lies near 0.5 GPa at 350 °C. It could be concluded that metamorphic rocks from the Meratus Complex experienced low-temperature and high-pressure conditions (blueschist-facies prior to the peak metamorphism of the epidote amphibolite-facies. The subduction environments in Meratus Complex during Cretaceous should be responsible for this metamorphic condition.

  3. Fundamental study of CO2-H2O-mineral interactions for carbon sequestration, with emphasis on the nature of the supercritical fluid-mineral interface.

    Energy Technology Data Exchange (ETDEWEB)

    Bryan, Charles R.; Dewers, Thomas A.; Heath, Jason E.; Wang, Yifeng; Matteo, Edward N.; Meserole, Stephen P.; Tallant, David Robert


    In the supercritical CO2-water-mineral systems relevant to subsurface CO2 sequestration, interfacial processes at the supercritical fluid-mineral interface will strongly affect core- and reservoir-scale hydrologic properties. Experimental and theoretical studies have shown that water films will form on mineral surfaces in supercritical CO2, but will be thinner than those that form in vadose zone environments at any given matric potential. The theoretical model presented here allows assessment of water saturation as a function of matric potential, a critical step for evaluating relative permeabilities the CO2 sequestration environment. The experimental water adsorption studies, using Quartz Crystal Microbalance and Fourier Transform Infrared Spectroscopy methods, confirm the major conclusions of the adsorption/condensation model. Additional data provided by the FTIR study is that CO2 intercalation into clays, if it occurs, does not involve carbonate or bicarbonate formation, or significant restriction of CO2 mobility. We have shown that the water film that forms in supercritical CO2 is reactive with common rock-forming minerals, including albite, orthoclase, labradorite, and muscovite. The experimental data indicate that reactivity is a function of water film thickness; at an activity of water of 0.9, the greatest extent of reaction in scCO2 occurred in areas (step edges, surface pits) where capillary condensation thickened the water films. This suggests that dissolution/precipitation reactions may occur preferentially in small pores and pore throats, where it may have a disproportionately large effect on rock hydrologic properties. Finally, a theoretical model is presented here that describes the formation and movement of CO2 ganglia in porous media, allowing assessment of the effect of pore size and structural heterogeneity on capillary trapping efficiency. The model results also suggest possible engineering approaches for optimizing trapping capacity and for

  4. Lithological nature of the subduction channel: Insights from the Karabakh suture zone (Lesser Caucasus) and general comparisons (United States)

    Hässig, Marc; Rolland, Yann; Sosson, Marc; Avagyan, Ara


    The lithological nature of major interplate boundaries is estimated by a field analysis of a well preserved exhumed subduction channel in the Caucasus Karabakh region. From this field example the subduction channel is a narrow geological object of about 500 m width formed at approximate depth of 10 km along an Andean-type subduction zone. It is comprised by an upper 'sedimentary' channel formed by an upper section of detrital and volcanic rocks thrusted on top of pelagic sediments scrapped off the oceanic floor. This sedimentary mélange is thrusted on top of an intensely deformed tectonic mélange. The tectonic mélange comprises blocks of basalt from the oceanic floor and a focussed deformation zone 50-100 m in width. This zone is mainly formed by mud-supported conglomerates exhibiting a chlorite + carbonate matrix with blocks of basalt, cross-cut by numerous chlorite-carbonate-epidote-albite veins. It overlies an undeformed ocean floor section. Superposed chlorite- and calcite-bearing veins in the mélange evidence high fluid:rock ratios of 0.3-2.3, with varied δ18O and δ13C isotopic ratios (+17 reservoirs along the subduction interface. These data show that the several fluid reservoirs situated along the interplate boundary could have been connected by high-magnitude co-seismic displacements along the subduction zone. These subduction channel features are confronted to other similar fossil examples and current settings, such as the Andes accretionary prism to propose a reconstructed geometry of the interplate contact zone from the surface to the base of the crust.

  5. Water management of the uranium production facility in Brazil (Caetite, BA). Potential impacts over groundwater quality

    International Nuclear Information System (INIS)

    The uranium unit of Caetite - in charge of all the 'yellow cake' produced in Brazil - is located in the semi-arid Northeast region at Bahia State. The geological uranium content of the ore is 3000 ppm, which is mainly associated with albites (NaAlSi8O8), and its extraction is achieved by means of a Heap-Leach process. This process has a low water demand, which is supplied by a network of wells, but can contribute to change the groundwater quality and in some cases the extinguishing of wells was observed. The managing of liquid mining wastes formed by drainage waters from mine pit and solid waste piles is not enough to avoid unwarranted releases in the environment, which turn necessary the waste treatment through passing them into the industrial plant in order to reduce radionuclide concentrations. The groundwater is Na-HCO3 type water and relative high concentration of Cl are observed in some groundwater. It seems that levels of uranium in groundwaters are mainly a consequence of the complexation of the metal by carbonates (or other anions) and not by any sort of the contamination of these waters by the drainage accumulated in the open pit. The speciation modelling allows identifying some areas where the replenishment of the aquifer is more active, but in general the recharge is a fast process run by direct infiltration. The stable isotope data (δ 2H and δ 18O) showed that evaporation plays a role during the infiltration, causing the groundwater salinization. These data discard the possibility that groundwater salinization was caused by discharge of deeper saline groundwater through faults associated to a regional groundwater flow system. The presence of an active shallow groundwater flow system offers better possibility for sustainable use of the groundwater resources in this semi-arid region of Brazil. (author)

  6. The origin and age of the metamorphic sole from the Rogozna Mts., Western Vardar Belt: New evidence for the one-ocean model for the Balkan ophiolites (United States)

    Borojević Šoštarić, S.; Palinkaš, A. L.; Neubauer, F.; Cvetković, V.; Bernroider, M.; Genser, J.


    This study brings new geochronological and petrochemical data from the metamorphic sole beneath the Rogozna Mts., Western Vardar ophiolite belt. The Rogozna metamorphic sole is located at the base of a serpentinite nappe and consists of amphibolites and talc-chlorite schists. The Rogozna amphibolites are medium- to fine-grained rocks with nematoblastic texture and pronounced foliation. They consist of green amphibole (~ 70 vol.%) with variable silica contents (6.4 to 7.8 Si apfu), as well as Mg# (molMg/[Mg + Fetot]; 0.53 to 0.77) and variably albitized plagioclase (~ 30 vol.%; Ab24-Ab98). Amphibolites are overprinted by a retrograde assemblage containing actinolite, epidote, clinoclore, sericite, chlorite, and magnetite. The amphibolites formed due to metamorphism of two basaltic suites: subalkaline/tholeiitic and alkaline. Subalkaline/tholeiitic amphibolites possess low Zr, Nb, Y, Th, Hf, TiO2, and P2O5 values and a LREE-depleted pattern, typical for the N-MORB (normal mid ocean ridge basalt) to BAB (back-arc basalt) origin. Alkaline amphibolites show elevated concentrations of Zr, Nb, Y, Th, Hf, TiO2, and P2O5 with a LREE-enriched pattern typically displayed by OIB (ocean island basalt). Amphibolites were crystallized during intra-oceanic thrusting at temperatures between 685 °C and 765 °C and at a depth of 12-17 km. 40Ar/39Ar cooling ages of amphibole, ranging from 165 to 170 Ma, slightly postdate the sole formation. Talc-chlorite schists are related to retrograde greenschist-facies metamorphism. They consist of Fe-rich talc and Cr-rich chlorite (peninite-diabantite) pseudomorphs after amphibole and MORB-type Cr-Al spinel, surrounded by Al- and Mg-poor ferrit chromite. The occurrence of ferrit chromite is related to earlier, amphibolite facies metamorphism. Chlorite pseudomorphs after amphibole were formed at 300-410 °C.

  7. Status of geochemical modeling of groundwater evolution at the Tono in-situ tests site, Japan

    International Nuclear Information System (INIS)

    Hydrochemical investigation of Tertiary sedimentary rocks at JNC's Tono in-situ tests site indicate the groundwaters are: meteoric in origin, chemically reducing at depths greater than a few tens of meters in the sedimentary rock, relatively old [carbon-14 ages of groundwaters collected from the lower part of the sedimentary sequence range from 13,000 to 15,000 years BP (before present)]. Ca-Na-HCO3 type solutions near the surface, changing to Na-HCO3 type groundwaters with increasing depth. The chemical evolution of the groundwaters is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the 'real' groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, Al, carbonate and sulfate) if the following assumptions are adopted: CO2 concentration in the gas phase contacting pore solutions in the overlying soil zone=10-1 bar, minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), muscovite (K) and pyrite (Eh and sulfate). It is noted, however, that the available field data may not be sufficient to adequately constrain parameters in the groundwater evolution model. In particular, more detailed information characterizing certain site properties (e.g., the actual mineralogy of 'plagioclase', 'clay' and 'zeolite') are needed to improve the model. Alternative conceptual models of key reactions may also be necessary. For this reason, a model that accounts for ion-exchange reactions among clay minerals, and which is based on the results of laboratory experiments, has also been evaluated in the present study. Further improvements of model considering ion-exchange reactions are needed in future, however. (author)

  8. A study on the groundwater flow and hydrogeochemical interaction in fractured rock masses

    International Nuclear Information System (INIS)

    Since the major transport mechanism of radionuclides leaching from a repository is by flowing groundwater, the flow paths, volume and travel time of groundwater in rock mass should be evaluated and convincingly predicted. Hence, the main objectives of this study include: 1) Characterization of the subsurface fracture system developed in rock mass, 2) Evaluation rocks with regard to the retardation mechanism of geological media. A groundwater flow study has been carried out for granitic porphyry occurred in the 2nd Yeonhwa mine which is located in Samchuck, Kangwondo. The fracture system in granitic porphyry has been studied on the basis of the existing surface geologic map and the sketch cards for tunnel geology, and accompanying field investigation. The groundwater system was analyzed by a numerical model of MODIFIED TRAFRAP WT for this study. Results are: 1) The groundwater flow system in fractured rock mass is governed by geological structure and fracture systems. 2) In the mountaineous region, a common feature in the study site, the local flow system is controlled by the amount of precipitation and topographic effects. 3) Jeekyung Dong volcanic rocks consist of tuff, qtz trachyte, rhyolite, andesite and tuffaceous andesite with major minerals of chlorite, smectite illite, chabazite, pyroxene, pl, K-feldspar, hematite, calcite. 4) Pl phenocrysts in tuffs underwent the albitization. Calcite filled partly the secondary pores in pl phenocryst. The porous pumices and glassy materials are partially altered to clay minerals. 5) The phenocrysts in tuff are strongly fractured. Bubbles, dissolved pores and welded textures are observed in tuff. Other volcanic rocks, however, show welded and dense textures. (author)

  9. Geochemical behavior of rare earth elements of the hydrothermal alterations within the Tepeoba porphyry Cu-Mo-Au deposits at Balikesir, NW Turkey (United States)

    Doner, Zeynep; Abdelnasser, Amr; Kiran Yildirim, Demet; Kumral, Mustafa


    This work reports the geochemical characteristics and behavior of the rare earth elements (REE) of the hydrothermal alteration of the Tepeoba porphyry Cu-Mo-Au deposit located in the Anatolian tectonic belt at Biga peninsula (Locally Balikesir province), NW Turkey. The Cu-Mo-Au mineralization at this deposit hosted in the hornfels rocks and related to the silicic to intermediate intrusion of Eybek pluton. It locally formed with brecciated zones and quartz vein stockworks, as well as the brittle fracture zones associated with intense hydrothermal alteration. Three main alteration zones with gradual boundaries formed in the mine area in the hornfels rock that represents the host rock, along that contact the Eybek pluton; potassic, propylitic and phyllic alteration zones. The potassic alteration zone that formed at the center having high amount of Cu-sulfide minerals contains biotite, muscovite, and sericite with less amount of K-feldspar and associated with tourmalinization alteration. The propylitic alteration surrounds the potassic alteration having high amount of Mo and Au and contains chlorite, albite, epidote, calcite and pyrite. The phyllic alteration zone also surrounds the potassic alteration containing quartz, sericite and pyrite minerals. Based on the REE characteristics and content and when we correlate the Alteration index (AI) with the light REEs and heavy REEs of each alteration zone, it concluded that the light REEs decrease and heavy REEs increase during the alteration processes. The relationships between K2O index with Eu/Eu* and Sr/Sr* reveals a positive correlation in the potassic and phyllic alteration zones and a negative correlation in the propylitic alteration zone. This refers to the hydrothermal solution which is responsible for the studied porphyry deposits and associated potassic and phyllic alterations has a positive Eu and Sr anomaly as well as these elements were added to the altered rock from the hydrothermal solution. Keywords: Rare

  10. Alteration and petrology of Intrusive Rocks associated with Gold Mineralization at Kuh-E-Zar Gold Deposit, Torbat-e-Heydaryeh

    Directory of Open Access Journals (Sweden)

    Alireza Mazloumi Bajestani


    Full Text Available Kuh- e -Zar gold deposit located 35 km west of Torbat-e-Heydaryeh, (Khorassan e- Razavi province, East of Iran. This deposit is a specularite-rich Iron oxide type (IOCG. This mine is situated within Khaf-Bardascan volcanic plutonic belt. Based on recent exploration along this belt, several IOCG type system plus Kuh-e-Zar deposit are discovered. In the study area, several type of tuff and lava having acid to intermediate composition are identified (upper Eocene. Oligo-Miocene granite, granodiorite, synogranite and monzonite intruded upper Eocene andesite-dacite-rhyolite. Intrusive rocks are meta-aluminous, medium to high-K series I-type. Based on spider diagram, intrusive rocks show enrichment in LILE = K, Th, Rb and depletion in HFSE = Nb, Sr, Ti. Based geochemistry of igneous rock, they formed in continental margin subduction zone. Propylitic (chlorite alteration is dominated and covers large area. Silicification is restricted only to mineralized zones. Argillic and albitization is found in certain location and cover small areas. The style of mineralization was controlled by the type and geometry of fault zones. Mineralization is found as vein, stockwork and breccias. Hypogene mineral Paragenesis include: specularite-quartz-gold-chlorite ± chalcopyrite ± pyrite ± galena ± barite. Secondary minerals formed due to oxidation are: goethite, limonite, lepidocrucite, Malachite, Azurite, Covelite, Cerucite, hydrocerucite, Pyrolusite and Smitsonite. In a few localities, chalcopyrite and minor pyrite and galena are found. Based on SEM analysis gold is present as electrum. Mineralization appeared in different type such as vein, stockwork and Hydrothermal breccia in strike sleep fault zone which are hidden inside volcano plutonic rocks. The average gold grade is between 3.02 ppm and ore reserve is estimated more than 3 million tons (cut off grade = 0.7 ppm.

  11. Geologic and ground spectrometric prospecting of the Abu Rusheid-Sikeit Shear Zones, South Eastern desert, Egypt

    International Nuclear Information System (INIS)

    Abu Rusheid-Sikeit granitic rocks (ASG) crop out in a belt elongated N W-S E (6.0 km long and 2.5 km width). The southern part of the pluton is surrounded by layered meta gabbros thrust ed over ophiolitic melange taking capital letter U- shaped. On the N W end of the pluton, more thinning is common giving rise to reverse V-shaped. The granitic rocks are classified based on the textures and presence of micas: porphyritic biotite granite; biotite granite; two-mica granite and muscovite granite. Two nearly perpendicular profiles (N W-S E and N E-S W) were constructed with 200 m spacing intervals and are discussed in detail. Cataclastic rocks (3.0 km2) occupy the core of the granitic pluton and enclose a roof pendant of mafic-ultramafic rocks. The concave side of the U-shaped points toward the muscovite granite, whereas the reverse V-shaped points toward porphyritic biotite granite at the end of W.Sikeit followed by biotite granite and two mica granite with gradational contacts. Sharp intrusive contacts are present between cataclastic rocks and two mica granites. Cataclastic rocks are dissected by two breccia ted, discontinuous shear zones (BSZ) in relatively perpendicular directions (Ene - WSW and NNE - SSW). Basic dykes (chemical traps for uranium) are common along the BSZ, and are completely altered to clay minerals. Humanization, argillization, greisenization, silicification, albitization, fluoritization and pyritization are the main alteration processes. The BSZ are enriched in U, Cu, V, Sn, Zn, W and Rees. Abu Rusheid cataclastic rocks represent an important target for economic grade resources. (authors)

  12. Kinetics of CO2–fluid–rock reactions in a basalt aquifer, Soda Springs, Idaho

    International Nuclear Information System (INIS)

    Highlights: • We model reaction progress in a basalt aquifer by using changes in groundwater. • We use U-series isotope ratios to determine the surface area of plagioclase. • Calculated dissolution rates for plagioclase compare to other CO2-charged systems. - Abstract: The dissolution of silicate minerals by CO2-rich fluids and the subsequent precipitation of CO2 as carbonate minerals represent a means of permanently storing anthropogenic CO2 waste products in a solid and secure form. Modelling the progression of these reactions is hindered by our poor understanding of the rates of mineral dissolution–precipitation reactions and mineral surface properties in natural systems. This study evaluates the chemical evolution of groundwater flowing through a basalt aquifer, which forms part of the leaking CO2-charged system of the Blackfoot Volcanic Field in south-eastern Idaho, USA. Reaction progress is modelled using changes in groundwater chemistry by inverse mass balance techniques. The CO2-promoted fluid–mineral reactions include the dissolution of primary plagioclase, orthoclase, pyroxene and gypsum which is balanced by the precipitation of secondary albite, calcite, zeolite, kaolinite and silica. Mineral mole transfers and groundwater flow rates estimated from hydraulic head data are used to determine the kinetics of plagioclase and orthoclase feldspar dissolution. Plagioclase surface area measurements were determined using the evolution of the U-series isotope ratios in the groundwater and are compared to published surface area measurements. Calculated rates of dissolution for plagioclase range from 2.4 × 10−12 to 4.6 × 10−16 mol/m2/s and orthoclase from 2.0 × 10−13 to 6.8 × 10−16 mol/m2/s respectively. These feldspar reaction rates, correlate with the degree of mineral–fluid disequilibrium and are similar to the dissolution rates for these mineral measured in other natural CO2-charged groundwater systems

  13. Luminescence properties of feldspars from the Northeast region of Brazil (United States)

    Santana, S. T.; Khoury, H. J.; Sullasi, H. L.; Guzzo, P. L.


    The aim of this study is to investigate the thermoluminescence (TL) and infrared-stimulated luminescence (IRSL) properties of three types of feldspars from the districts of Solonópole and Parelhas located in the Northeast region of Brazil in order to propose a preheat procedure to minimize the anomalous fading effect in these materials. The feldspar samples were characterized by X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF). The XRD analysis showed that the feldspar from Solonópole and one of the samples from the Parelhas district were classified as microcline (K-feldspar). The other sample from Parelhas was classified as albite (Na-feldspar) mixed with low concentration of muscovite and quartz. Studies of the fading effects in TL and IRSL signals for 30 days and preheating effects from 50 to 250°C for 10 minutes were carried out with these samples. The results show that preheating at 125°C is sufficient to avoid the 30 days fading. The TL and IRSL dose responses for 60Co gamma radiation were studied in the range of 1 to 400 Gy. The results showed a linear response in the range of 1 to 100 Gy for the two types of Parelhas feldspars and from 50 to 400 Gy for the Solonópole feldspar. The low sensitivity showed by the feldspar from Solonópole is discussed in relation to its mineralogical composition. It is concluded that the TL and IRSL sensitivities are not associated with K- and Na- types of feldspar. The results of this paper will contribute to a standardized moderate annealing treatment for retrospective dosimetry and dating.

  14. Luminescence properties of feldspars from the Northeast region of Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Santana, S T; Khoury, H J; Sullasi, H L; Guzzo, P L, E-mail:


    The aim of this study is to investigate the thermoluminescence (TL) and infrared-stimulated luminescence (IRSL) properties of three types of feldspars from the districts of Solonopole and Parelhas located in the Northeast region of Brazil in order to propose a preheat procedure to minimize the anomalous fading effect in these materials. The feldspar samples were characterized by X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF). The XRD analysis showed that the feldspar from Solonopole and one of the samples from the Parelhas district were classified as microcline (K-feldspar). The other sample from Parelhas was classified as albite (Na-feldspar) mixed with low concentration of muscovite and quartz. Studies of the fading effects in TL and IRSL signals for 30 days and preheating effects from 50 to 250{sup 0}C for 10 minutes were carried out with these samples. The results show that preheating at 125{sup 0}C is sufficient to avoid the 30 days fading. The TL and IRSL dose responses for {sup 60}Co gamma radiation were studied in the range of 1 to 400 Gy. The results showed a linear response in the range of 1 to 100 Gy for the two types of Parelhas feldspars and from 50 to 400 Gy for the Solonopole feldspar. The low sensitivity showed by the feldspar from Solonopole is discussed in relation to its mineralogical composition. It is concluded that the TL and IRSL sensitivities are not associated with K- and Na- types of feldspar. The results of this paper will contribute to a standardized moderate annealing treatment for retrospective dosimetry and dating.

  15. Emplacement kinematics of nepheline syenites from the Terrane Boundary Shear Zone of the Eastern Ghats Mobile Belt, west of Khariar, NW Orissa: Evidence from meso- and microstructures

    Indian Academy of Sciences (India)

    T K Biswal; Harish Ahuja; Himansu Sekhar Sahu


    Nepheline syenite plutons emplaced within the Terrane Boundary Shear Zone of the Eastern Ghats Mobile Belt west of Khariar in northwestern Orissa are marked by a well-developed magmatic fabric including magmatic foliation, mineral lineations, folds and S-C fabrics. The minerals in the plutons, namely microcline, orthoclase, albite, nepheline, hornblende, biotite and aegirine show, by and large, well-developed crystal faces and lack undulose extinction and dynamic recrystallization, suggesting a magmatic origin. The magmatic fabric of the plutons is concordant with a solid-state strain fabric of the surrounding mylonites that developed due to noncoaxial strain along the Terrane Boundary Shear Zone during thrusting of the Eastern Ghats Mobile Belt over the Bastar Craton. However, a small fraction of the minerals, more commonly from the periphery of the plutons, is overprinted by a solid state strain fabric similar to that of the host rock. This fabric is manifested by discrete shear fractures, along which the feldspars are deformed into ribbons, have undergone dynamic recrystallization and show undulose extinction and myrmekitic growth. The shear fractures and the magmatic foliations are mutually parallel to the C-fabric of the host mylonites. Coexistence of concordant solid state strain fabric and magmatic fabric has been interpreted as a transitional feature from magmatic state to subsolidus deformation of the plutons, while the nepheline syenite magma was solidifying from a crystal-melt mush state under a noncoaxial strain. This suggests the emplacement of the plutons synkinematic to thrusting along the Terrane Boundary Shear Zone. The isotopic data by earlier workers suggest emplacement of nepheline syenite at 1500 + 3/− 4Ma, lending support for thrusting of the mobile belt over the craton around that time.

  16. On the interaction of pure and impure supercritical CO2 with rock forming minerals in saline aquifers: An experimental geochemical approach

    International Nuclear Information System (INIS)

    The aim of this experimental study was to evaluate and compare the geochemical impact of pure and impure CO2 on rock forming minerals of possible CO2 storage reservoirs. This geochemical approach takes into account the incomplete purification of industrial captured CO2 and the related effects during injection, and provides relevant data for long-term storage simulations of this specific greenhouse gas. Batch experiments were conducted to investigate the interactions of supercritical CO2, brine and rock-forming mineral concentrates (albite, microcline, kaolinite, biotite, muscovite, calcite, dolomite and anhydrite) using a newly developed experimental setup. After up to 42 day (1000 h) experiments using pure and impure supercritical CO2 the dissolution and solution characteristics were examined by XRD, XRF, SEM and EDS for the solid, and ICP–MS and IC for the fluid reactants, respectively. Experiments with mixtures of supercritical CO2 (99.5 vol.%) and SO2 or NO2 impurities (0.5 vol.%) suggest the formation of H2SO4 and HNO3, reflected in pH values between 1 and 4 for experiments with silicates and anhydrite and between 5 and 6 for experiments with carbonates. These acids should be responsible for the general larger amount of cations dissolved from the mineral phases compared to experiments using pure CO2. For pure CO2 a pH of around 4 was obtained using silicates and anhydrite, and 7–8 for carbonates. Dissolution of carbonates was observed after both pure and impure CO2 experiments. Anhydrite was corroded by approximately 50 wt.% and gypsum precipitated during experiments with supercritical CO2 + NO2. Silicates do not exhibit visible alterations during all experiments but released an increasing amount of cations in the reaction fluid during experiments with impure CO2. Nonetheless, precipitated secondary carbonates could not be identified.

  17. Why is Dawsonite Absent in CO2 Charged Reservoirs?

    International Nuclear Information System (INIS)

    Growth of the sodium-aluminium-hydroxy carbonate dawsonite (NaAl(OH)2CO3) after charging saline aquifers with CO2 has been assumed in a plethora of numerical simulations at different mineralogies, aqueous solutions, pressures and temperatures. It appears however that dawsonite is less abundant than expected in natural CO2 storage analogues if we take into account the thermodynamic stability alone. We have mapped the thermodynamic stability of dawsonite relative to mineral phases like albite, kaolinite and analcime from 37 to 200 C and performed closed-system batch kinetic simulations using a new kinetic expression including a nucleation term based on classical nucleation theory, and a growth term that was based on BCF growth theory. Using this rate equation, we have performed a sensitivity study on dawsonite growth on mineralogy, temperature, CO2 pressure, nucleation rate and its dependencies on temperature and affinity, and on the dawsonite precipitation rate coefficient. Simulations with dawsonite growth disabled showed that the maximum over-saturation reached for dawsonite for seawater-like solutions never exceeded 3-4 times over-saturation. The positive effect on dawsonite growth of increasing the CO2 pressure was mostly neutralized by higher acidity. Decreasing the precipitation rate coefficient by 5 orders of magnitude had a limited effect on the onset of significant growth, but the amount of dawsonite formed at the end of the 1 000 years simulated time was only 37% below the high-rate case. Reducing the nucleation rates had similar effects leading to postponed dawsonite growth. Finally, based on thermodynamic considerations and numerical simulations, we suggest that the potential of dawsonite growth is limited to a medium-temperature window framed by a high thermodynamic stability relative to competing mineral phases at low temperatures, but with rapidly diminishing nucleation and growth rates at lower temperatures constrained by energy barriers. (authors)

  18. New geological model of the Lagoa Real uraniferous albitites from Bahia (Brazil) (United States)

    Oliveira Chaves, Alexandre


    New evidence supported by petrography (including mineral chemistry), lithogeochemistry, U-Pb geochronology by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and physicochemical study of fluid and melt inclusions by LA-ICP-MS and microthermometry, point to an orogenic setting of Lagoa Real (Bahia-Brazil) involving uraniferous mineralization. Unlike the previous models in which uraniferous albitites represent Na-metasomatised 1.75 Ga anorogenic granitic rocks, it is understood here that they correspond to metamorphosed sodium-rich and quartz-free 1.9 Ga late-orogenic syenitic rocks (Na-metasyenites). These syenitic rocks are rich not only in albite, but also in U-rich titanite (source of uranium). The interpretation of geochemical data points to a petrogenetic connection between alkali-diorite (local amphibolite protolith) and sodic syenite by fractional crystallization through a transalkaline series. This magmatic differentiation occurred either before or during shear processes, which in turn led to albitite and amphibolite formation. The metamorphic reactions, which include intense recrystallization of magmatic minerals, led uraninite to precipitate at 1.87 Ga under Oxidation/Reduction control. A second population of uraninites was also generated by the reactivation of shear zones during the 0.6 Ga Brasiliano Orogeny. The geotectonic implications include the importance of the Orosirian event in the Paramirim Block during paleoproterozoic Săo Francisco Craton edification and the influence of the Brasiliano event in the Paramirim Block during the West-Gondwana assembly processes. The regional microcline-gneiss, whose protolith is a 2.0 Ga syn-collisional potassic granite, represents the albitite host rock. The microcilne-gneiss has no petrogenetic association to the syenite (albitite protolith) in magmatic evolutionary terms.

  19. Radiometric, SEM and XRD investigation of black sands at Chituc placer deposit North of the City of Navodari, Romania (United States)

    Duliu, Octavian G.; Blebea-Apostu, Ana-Maria; Gomoiu, Claudia; Margineanu, Romul M.; Costea, Constantin; Dumitras, Delia; Ion, Adriana


    The black sand of the Chituc marine sandbank situated northern of the city of Navodari (Romania), displayed anomalous high ambient dose rates. Field measurements performed during 2013 Summer campaign recorded in some places dose rate up to 200 nSv/h, significantly overpassing the average value of 44 ± 20 nSv/h recorded along the entire Southern sector of Romanian Black Sea shore. Here, the sand presented a black-brownish hue, different by the usual white yellowish colour. Gamma ray spectrometry performed on both Slanic-Prahove Underground Low Background Laboratory and Gological Institute Radiometric Facilities showed with clarity the dominance of 228-Ac radioisotope in the 50 microns fraction together with the 226-Ra and traces of 40-K. No significant amount of anthropogenic 137-Cs were identified. The other granulometric fractions, i.e. 315, 200 as well 100 microns presented a significant lower level of radioactivity. X-ray diffraction (XRD) as well as Scanning Electron Microsopy (SEM) data attested the presence of monazite, zircon, magnetite, ilmenite, andradite, quartz, aragonite and albite in different proportions, the monazite and zircon being preponderant in the 50 microns, the most radioactive fraction. Based on both radiometric and XRD determinations we come to the conclusion that the evidenced radioactivity could be attributed to both uranium and thorium series in the zircon and monazite fractions and to a lesser extent in the garnet fraction. By its position with respect to Danube Delta, the Chituc marine sandbank could be regarded as a placer where heavy minerals discharged in the Black Sea by the Danube River and transported southward by the Great Black Sea Rim are deposited by gravity separation during sedimentary processes. The implications of the Chituc levee radioactive anomaly for any further human activity are analysed and discussed. Acknowledgement: Work done within the BS ERA NET 041 project in the frame of BS-ERA.NET Pilot Joint CAll 2010-2011.

  20. Petrology of the Sams Creek peralkaline granite dike, Takaka, New Zealand

    International Nuclear Information System (INIS)

    The Sams Creek peralkaline granite is a discontinuous dike, 7 km long and up to 60 m thick, with an 'outlier' a further 12 km along strike. It cuts lower Paleozoic metasedimentary rocks of the Takaka Terrane. Isotopic data suggest a Late Triassic age (226 ± 1.1 Ma), which in turn suggests only minor displacement on the Devil River Thrust since this time, and a Mesozoic age for at least some of the regional deformation/metamorphism which produced north-south-trending fold axes in Nelson. Where fresh, the fine-grained (av. 0.2 mm) dike comprises quartz (32%), mesoperthitic alkali feldspar (50%), aegirine (3%), arfvedsonite and riebeckite (13%), and traces of zincian-ilmenite, zircon, and fluorite. The bulk of the dike has been altered by late and postmagmatic F-rich fluids to assemblages rich in albite, quartz ± sericite-rutile-biotite (annite?)-magnetite-fluorite-pyrite-arsenopyrite. The altered rocks host significant Au mineralisation. Very low Al2O3 renders the dike distinctly peralkaline. This feature, together with high values for the high field strength elements Zr, Nb, Ga and Y, suggests, by analogy with similar rocks elsewhere, emplacement into an extensional tectonic environment. The east-west orientation of the dike is consistent with localised foreland extension parallel to the Gondwana margin during Triassic subduction/collision of the Rakaia Terrane to the east. Only one other peralkaline granite has been reported from the Western Province of New Zealand and both are shown to be similar to classic peralkaline granites of Nigeria and a rare occurrence in the Lachlan Fold Belt of Australia. (author). 32 refs., 3 figs., 4 tabs

  1. Omphacite and aragonite-bearing metapelites from the Sambagawa belt in central Shikoku, Japan and their implications (United States)

    Kouketsu, Y.; Enami, M.


    Omphacite and aragonite-bearing metapelites occur in the epidote-amphibolite facies grade area of the Besshi region, Sambagawa metamorphic belt, central Shikoku, Japan. Omphacite in the Sambagawa metapelite is very rare and aragonite is the first report from the high-grade region of the Sambagawa belt. Omphacite (Xjd = 0.37-0.62) and aragonite (SrCO3 garnet. Major matrix phases of the metapelites are garnet, phengite, chlorite, epidote, titanite, calcite, albite, and quartz. The inclusion assemblage of omphacite, phengite and quartz in garnet indicate equilibrium conditions of P=1.7-1.9 GPa and T=470-530 °C employing thermobarometry calibrated by Krogh Ravna and Terry (2004). The quartz Raman barometry (Enami et al., 2007) was also applied to the quartz grains sealed in garnet of the omphacite and aragonite-bearing samples and the surrounding metapelites. The quartz inclusions in these samples usually preserve a high residual pressure that is equivalent to the Sambagawa eclogite samples. These metapelites with high pressure quartz inclusions, however, mostly contain no eclogite facies mineral such as omphacite. On the other hand, paragonite commonly occurs as inclusions in garnet in these metapelites, and was probably a main sodic phase in the Sambagawa metapelites during the eclogite facies stage instead of sodic pyroxene. The omphacite and aragonite-bearing metapelites and the surrounding lithologies have probably experienced the eclogite facies metamorphism and the eclogite facies metamorphism covered the Sambagawa belt extends further than previously recognized. Metamorphic zonation map of the Besshi region and the position of the metapelite containing high pressure evidence.

  2. Infrared microspectroscopy analysis of water distribution in deformed and metamorphosed rocks (United States)

    Nakashima, Satoru; Matayoshi, Hiromi; Yuko, Takako; Michibayashi, Katsuyoshi; Masuda, Toshiaki; Kuroki, Noriko; Yamagishi, Hiraku; Ito, Yuki; Nakamura, Akira


    Infrared microspectroscopy has been applied to thin sections of various deformed and metamorphosed rocks in order to investigate water content of quartz in these rocks. The broad IR band absorbance around 3400 cm -1 probably due to fluid-inclusion molecular water (H 2O) was used to calculate water contents. Deformed granitic rocks from the Yanazawa-Kamimura area near the Median Tectonic Line (MTL) showed an increase of water content in quartz from about 300 ppm to 2500 ppm toward the MTL with increasing degree of deformation. Metacherts from Sambagawa metamorphic rocks (Asemigawa route) showed a systematic decrease of water content in quartz from about 1000 ppm to 200 ppm with increasing metamorphic degree from chlorite, garnet, albite-biotite to oligoclase-biotite zones. An Archaean metachert from the Napier Complex (granulite facies) has only 40 ppm water. Comparing this with an Inuyama unmetamorphosed chert sample having water contents of 3500 to 7000 ppm (a starting point of metamorphism), the systematic decrease of water in quartz with increasing metamorphic grade may extend from unmetamorphosed cherts to the highest-grade metacherts. Water contents in high-pressure metamorphic rocks in Japan are mostly of the order of 500 ppm (300-700 ppm), except for those from Kurosegawa with a water content as high as 1700 ppm. These results represent an exploratory analysis of intragranular water contents in quartz in various deformed and metamorphosed rocks. Further micro FT-IR studies of the distribution of water in crustal rocks will provide a quantitative basis for examining the geochemical cycle of water in the earth's crust.

  3. Site investigation SFR. Fracture mineralogy and geochemistry of borehole sections sampled for groundwater chemistry and Eh. Results from boreholes KFR01, KFR08, KFR10, KFR19, KFR7A and KFR105

    Energy Technology Data Exchange (ETDEWEB)

    Sandstroem, Bjoern (WSP Sverige AB (Sweden)); Tullborg, Eva-Lena (Terralogica AB, Grabo (Sweden))


    This report is part of the complementary site investigations for the future expansion of SFR. The report presents the results obtained during a detailed mineralogical and geochemical study of fracture minerals in drill cores from borehole section sampled for groundwater chemistry and where downhole Eh measurements have been performed. The groundwater redox system comprises not only the water, but also the bedrock/fracture mineral system in contact with this water. It is thus important to gain knowledge of the solid phases in contact with the groundwater, i.e. the fracture minerals. The samples studied for mineralogy and geochemistry, here reported, were selected to represent the fracture surfaces in contact with the groundwater in the sampled borehole sections and will give input to the hydrogeochemical model (SFR SDM). The mineralogy was determined using SEM-EDS and XRD and the geochemistry of fracture filling material was analysed by ICP-AES and ICP-QMS. The most common fracture minerals in the samples are mixed layer clay (smectite-illite), illite, chlorite, calcite, quartz, adularia and albite. Other minerals identified in the borehole sections include laumontite, pyrite, barite, chalcopyrite, hematite, Fe-oxyhydroxide, muscovite, REE-carbonate, allanite, biotite, asphaltite, galena, sphalerite, arsenopyrite, uranium phosphate, uranium silicate, Y-Ca silicate, monazite, xenotime, harmotome and fluorite. There are no major differences between the fracture mineralogy of the investigated borehole sections from SFR and the fracture mineralogy of the Forsmark site investigation area. The four fracture mineral generations distinguished within the Forsmark site investigation are also found at SFR. However, some differences have been observed: 1) Barite and uranium minerals are more common in the SFR fractures, 2) clay minerals like mixed layer illite-smectite and illite dominates in contrast to Forsmark where corrensite is by far the most common clay mineral and, 3

  4. Modeling of the interaction between an engineered clay barrier and concrete structures in a deep storage vault

    International Nuclear Information System (INIS)

    The degradation of concrete structures in a storage vault will release an alkaline plume influencing the geochemical evolution of clay engineered barriers or plugs. The studied configuration has a representative scale and is composed of a rectangular clay barrier interfaced on one side with a cement block and on the other side with an external granitic field. A clay model including major and accessory minerals is used; cement material is supposed to be made of portlandite and CSH minerals. The clay barrier and the cement block are assumed to be initially saturated and in equilibrium with their respective interstitial water. Diffusive transport of aqueous species coupled to chemistry is simulated in a one dimension space up to 10,000 y. The feed-back of the porosity evolution on the transport properties is not taken into account. The temperature is supposed to be constant (25 C). calculations are performed with the TRIO-EF coupled transport-chemistry code. The main results deal with the evolution of the pH profile across the clay barrier, the dissolution of clay minerals and the precipitation of new solid phases in the clay such as albite, gibbsite and CSH. These simulations show that the pH excursion includes only a minor part of the clay barrier at 10,000 y and that the CSH precipitation retards the alkaline plume progression. The appearance of local accumulations of newly precipitated minerals might strongly reduce the porosity. Future developments of this work include: (1) the completion of the geochemical model by introducing other minerals in concrete (other CSH phases and sulfo-aluminates) and ion exchange sites within the clay, (2) the implementation of a precipitation/dissolution model in order to describe on a realistic way the porosity profile evolution and possible clogging phenomena

  5. Trace elements and mineral composition of waste produced in the process of combustion of solid fuels in individual household furnaces in the Upper Silesian Industrial Region (Poland

    Directory of Open Access Journals (Sweden)

    Smołka-Danielowska Danuta


    Full Text Available This study presents preliminary research results, with regard to the concentration of chosen trace elements (Mn, Cr, Tl, Ni, Cu, Zn, As, Cd, Ba, Pb in waste, which was produced in the process of combustion of solid fuels (hard coal and flotation concentrate of bituminous coal in individual household furnaces in Poland (in the Upper Silesian Industrial Region. 27 samples of ash, 4 samples of hard coal and 2 samples of flotation concentrate of bituminous coal were prepared for the research. Methods such as: ICP-MS, X-ray diffraction by means of the powder method and scanning electron microscopy were used during the research. In the ash samples obtained from the combustion of hard coal, the highest average concentrations were: Mn (1477.7 ppm, Ba (1336.4 ppm and Zn (599.7 ppm. In the samples obtained from the combustion of flotation concentrate of bituminous coal, the highest average concentrations was stated for: Zn (762.4 ppm, Mn (668.5 ppm, Pb (552.1 ppm and Ba (211.7 ppm. Crystalline components were determined by used the X-ray diffraction method and the samples of ash obtained from the combustion of hard coal contained: anhydrite, gypsum, hematite, magnetite, quartz, calcite, mullite, periclase, kaolinite, dolomite, pyrite, sphalerite, galena and feldspars (albite-anorthite. The samples of ash obtained from the combustion of flotation concentrate of bituminous coal contain: pyrite, quartz, potassium feldspar, muscovite and kaolinite. The scanning electron microscope analysis enabled the identification of the chemical composition of single ash grains and determined their morphology (aluminosilicate forms, substance PbS and ZnS, oxides of Ni, Cu and Mn, monazite, xenotime.

  6. Geological and geochemical characteristics of the Weilasito Sn-Zn deposit, Inner Mongolia%内蒙古赤峰维拉斯托大型锡多金属矿的地质地球化学特征

    Institute of Scientific and Technical Information of China (English)

    祝新友; 张志辉; 付旭; 李柏阳; 王艳丽; 焦守涛; 孙雅琳


    The Weilasito Sn-Zn-Cu deposit is located in Keshiketen, Inner Mongolia, at latitude 44°5'5"N,longitude 117°29'53"E. The mineralization styles include granite-type Sn-Zn at the top of the granite, quartz vein type Sn-Zn ore near the granite, Cu-Zn sulfide vein and Pb-Zn-Ag sulfide vein distal from the granite. Based on petrology, geology and geochemistry of elements and chronology, the authors recognized the granite magma revolution, the origin of the deposit and the relations between the mineralization styles. LA-ICP-MS zircon U-Pb dating yielded a weighted mean 206Pb/238U age of 139.5±1.2Ma(MSWD=3.3)for the alkali feldspar granite pluton. There are multilevel phenocrysts in the pluton, and the crystallization sequence is albite-quartz-K-feldspar-albite-quartz, topaz, cassiterite, and sphalerite. The granite rich in SiO2 and Rb, Cs, Nb, Ta, W, Mo, Bi, Cu, Zn, In etc., poor in Al2O3, TiO2, TFe2O3, CaO and Sr, Ba etc., the An value of the albite is lower than 0.3, similar to data of the granite of Sn-W deposits in the Nanling belt. Late magma experienced magmatic-hydrothermal transitional stage as well as gradual continuous evolution to hydrothermal stage. The Si rich, F rich and S rich fluid phases were separated from the magma to form the droplets (pocket) of quartz, topaz, cassiterite-sphalerite respectively in the granite-type Sn-Zn ore. The fluid inclusions are melt, melt-fluid and liquid respectively. The granite-type Sn-Zn ore formed at the top of pluton at the magma-hydrothermal transitional stage, the quartz vein-type Sn-Zn ore occurs at the outer part and the sulfide-vein Cu-Zn, Pb-Zn-Ag ore of the hydrothermal stage occurs distal from the rock body. All of the ores and the plutons comprise the magmatic hydrothermal tin polymetallic metallogenic system. In Xilin Gol-Chifeng area, there are some Pb-Zn-Ag veins (deposits and/or mineralization) related to the acidic intrusive rocks. There probably exsit large-sized hydrothermal tin (tungsten) polymetallic

  7. Petrology of blueschist and meta-greywacke along the Turkmeni-Ordib fault (Turkmeni area, SE of Anarak

    Directory of Open Access Journals (Sweden)

    Fereshteh Bayat


    Full Text Available Introduction The occurrence of blueschist metamorphic facies is believed to mark the existence of former subduction zones. This facies is represented in the main constituents of subduction-accretion complexes, where it occurs in separate tectonic sheets, imbricated slices, lenses, or exotic blocks within a serpentinite mélange (Volkova et al., 2011. The evidence of the presence and maturity of Paleo- Tethys oceanic crust in the CEIM (define this in Paleo-Tethys branches, subduction and collision has been studied by various authors (Bagheri, 2007; Zanchi et al., 2009; Bayat and Torabi, 2011; Torabi 2011. Late Paleozoic blueschists have recognized in the western part of the CEIM (e. g. Anarak, Chupanan and Turkmeni in linear trends. Metamorphic rocks of the Turkmeni area (SE of Anarak are composed of blueschist and meta-greywacke and are situated along the Turkmeni-Ordib fault associated with Paleozoic rock units and serpentinized peridotite bodies. Turkmeni blueschist and meta-greywackes have not been studied by previous workers. The Turkmeni blueschists consist of albite, winchite, actinolite and epidote. Granoblastic, nematoblastic and lepidoblastic are main textures in these rocks. Winchite is found in the matrix and around epidote grains. This sodic-calcic amphibole serves as an index mineral in blueschist facies. Actinolite and epidote formed during retrograde metamorphism of blueschists in the greenschist facies. The mineral assemblage of albite, epidote, chlorite and phengite ± garnet is present in meta-greywackes in the Turkmeni blueschists. Veins of garnet, muscovite, quartz and opaque minerals are extensive in these rocks. Epidote and chlorite formed in meta-greywackes by retrograde metamorphism in the greenschist facies. The aim of the present study is to determine the petrological and geochemical characteristics, P-T condition of blueschists and meta-greywackes, as well as the geotectonic setting of primary basaltic rocks of the

  8. Procesos de formación de paragénesis ceolíticas en el metamorfismo de muy bajo grado de las volcanitas paleógenas al sur de Confluencia, Neuquén, República Argentina Formation of zeolitic assemblages during very low grade metamorphism of Paleogene volcanic rocks, south of Confluencia, Neuquén, Argentina

    Directory of Open Access Journals (Sweden)

    María E. Vattuone


    edad miocena inferior; posteriormente, un fracturamiento tensional (Mioceno Superior? favoreció la acción de nuevos fluidosA metamorphic assemblage of very low grade metamorphism in Paleogene volcanic rocks from the Andesitic Formation, Confluencia, Neuquén Province, is studied. The protolith is basaltic and andesitic. The secondary minerals are calcic, calcosodic and sodic zeolites. Wairakite is the first zeolite to crystallize, together with other minerals like albite, adularia, pumpellyite, titanite, pectolite, pyrite, native copper, hematite, smectite and quartz in the matrix and in phenocrysts. They were followed by laumontite, yugawaralite, and sodic wairakite in the matrix and in amygdales. Later on, only in amygdales, sodic wairakite was replaced by scolecite and mesolite, whereas laumontite and yugawaralite were replaced by heulandite and calcic clinoptilolite. Then barrerite, tetranatrolite and paranatrolite replaced albite and adularia was replaced by illite. These assemblages are in accordance with a pervasive geothermal field type, very low grade metamorphism in the zeolite facies. The equilibrium assemblage wairakite-yugawaralite-albite indicates P-T conditions of <0,5kb and <220°C. At temperatures lower than 200°C in the zeolite facies heulandite group minerals, scolecite and mesolite formed replacing the first association. In a second event, at temperature lower than 150°C, barrerite, paranatrolite and tetranatrolite precipitated in joints together with stilbite and stellerite. Other process, formed analcime by replacement of barrerite. Then, an increase in X CO2 favoured the precipitation of calcite in joints. The thermal waters were neutral to slightly alkaline, the ƒO2 conditions were in the hematite - pyrite stability field, the P H2O / Ptotal ratio was high and then, decrases in the joints, at the same time that X C2O was increasing; it was low during the main process. The geothermal system was heated by Early Miocene magmatic intrusions

  9. Modelización del proceso de episienitización (decuarcificación-albitización: formulación cinética y transporte advectivo en medio continuo

    Directory of Open Access Journals (Sweden)

    Caballero, J. M.


    Full Text Available The development of episyenites from Sierra de Guadarrama has been modelized. The process mainly consists in a coupled process of dequartztification-albitization. The model is based on pure advective mass transport in a continuum medium, where the reactive process is formulated from a kinetic point of view. It is demonstrated the possibility of its formation through the action of low-salinity fluids (2,32 wt % NaCl equiv., partially equilibrated with a biotite monzogranite, linked to isobaric reaction paths across negative geothermal gradients, intersecting the quartz retrograde solubility field, and associated to a quick fluid-resident mobilisation due to the environment tectonic opening. The model explains the albitic nature of the alteration against former models. These predict microcline formation from the gradient relations ∂logKmic/∂T > ∂logKab/∂T (0.05739 and 0.05735 and ∂logKKCl/∂T NaCl/∂T (-0.038 and -0.036. Albite formation arises from the anortite component presence, because ∂logKan/∂T =0,1293 ≻ ∂logKmic/∂T. Non-equilibrium relations are very small, which implies that alteration intensity arises from the circulation of huge fluid volumes. This process feature together the kinetic rate constants result in a small change, spatial and temporal, of the fluid composition, being practically null for its main components (Na, K and, subordinately to these, the pH. The model also shows the necessity of handling geochemical systems as complex as possible. In this way, the proposed aqueous speciation proves that pH evolution along decreasing temperature is not necessarily acid, but inlet fluid pH dependent due to the calculated concentrations show that its behaviour mainly depends as much from Hel as from the NaOH base dissociation.Se modeliza teóricamente la formación de las episienitas de la Sierra de Guadarrama, consistente básicamente en un proceso acoplado de decuarcificaci

  10. Varena suite in the crystalline crust of the Southern Lithuania: implication to the genesis and mineralization (United States)

    Kirkliauskaite, Vaida; Motuza, Gediminas; Skipityte, Raminta


    Keywords: Lithuania, Proterozoic, Varena suite, rare earth elements, metasomatosis. Crystalline crust in Southern Lithuania is covered by 200-500 m thick sedimentary cover and is investigated by potential field mapping and drilling. It is composed by amphibolites (metabasalts), biotite-quartz-plagioclase gneisses (metapsammites and porphyry metadacite and metaandesite) of Orosirian period. Each lithology is predominant in alternating bands extended NNE-SSW. Supracrustals are metamorphosed on the level of amphibolite facies and migmatized. Intrusive rocks are represented by coeval rare bodies of gabbro, peridotite and widespread Calymmian granitic plutons. Varena suite comprises olivine, enstatite, diopside, olivine-magnetite, magnetite, apatite-bearing, and presumably also dolomite rocks. They form integrated bodies few sq. km large, concentrated in the ˜300 km2area extended in N-S direction.Bodies of particular rocks from Varena suite fixed in the boreholes are few tenths up to few hundred meters thick, except apatite-bearing rocks, forming decimeter up to meter scale lenses and veins. Rocks of Varena suite are affected by strong metasomatic alteration. Olivine is substituted by serpentine, and phlogopite, pyroxenes with amphibols (hornblende, actinolite, tremolite, rarely richterite). The country rocks (amphibolites, metaporphyres) also affected by alkaline (mainly sodic) metasomatosis manifested by formation of scapolite, albite, clynopyroxene (often sodic), phlogopite, carbonates. The mineralization of REE (up to 2759-3100 ppm of La and Ce respectively), Th, U, P hosted by monazite, apatite, allanite is spatially related to the Varena suite and some metasomatized supracrustals. The views on the genesis of Varena suite are contradicting. By various authors they are regarded as skarns, presuming metasomatic origin, as layered intrusions or products of alkaline and carbonatitic magmatism. In this presentation the genetic model is reviewed based on

  11. Fluorapatite in carbonatite-related phosphate deposits: the case of the Matongo carbonatite (Burundi) (United States)

    Decrée, Sophie; Boulvais, Philippe; Tack, Luc; André, Luc; Baele, Jean-Marc


    The Matongo carbonatite intrusive body in the Neoproterozoic Upper Ruvubu alkaline plutonic complex (URAPC) in Burundi is overlain by an economic phosphate ore deposit that is present as breccia lenses. The ore exhibits evidence of supergene enrichment but also preserves textures related to the concentration of fluorapatite in the carbonatitic system. Magmatic fluorapatite is abundant in the ore and commonly occurs as millimeter-sized aggregates. It is enriched in light rare earth elements (LREE), which is especially apparent in the final generation of magmatic fluorapatite (up to 1.32 wt% LREE2O3). After an episode of metasomatism (fenitization), which led to the formation of K-feldspar and albite, the fluorapatite-rich rocks were partly brecciated. Oxygen and carbon isotope compositions obtained on the calcite forming the breccia matrix (δ18O = 22.1 ‰ and δ13C = -1.5 ‰) are consistent with the involvement of a fluid resulting from the mixing of magmatic-derived fluids with a metamorphic fluid originating from the country rocks. In a subsequent postmagmatic event, the carbonates hosting fluorapatite were dissolved, leading to intense brecciation of the fluorapatite-rich rocks. Secondary carbonate-fluorapatite (less enriched in LREE with 0.07-0.24 wt% LREE2O3 but locally associated with monazite) and coeval siderite constitute the matrix of these breccias. Siderite has δ18O values between 25.4 and 27.7 ‰ and very low δ13C values (from -12.4 to -9.2 ‰), which are consistent with the contribution of organic-derived low δ13C carbon from groundwater. These signatures emphasize supergene alteration. Finally, the remaining voids were filled with a LREE-poor fibrous fluorapatite (0.01 wt% LREE2O3), forming hardened phosphorite, still under supergene conditions. Pyrochlore and vanadiferous magnetite are other minerals accumulated in the eluvial horizons. As a consequence of the supergene processes and fluorapatite accumulation, the phosphate ore, which

  12. The Saint Martin de Belleville syncline and its uraniferous permian sandstone

    International Nuclear Information System (INIS)

    This dissertation (these de specialite) is a study of the geology of the St.Martin d.B. syncline and the uranium prospect 'le Cochet' in the Carboniferous Brianconnais Zone of Savoy. Stratigraphy and sedimentology: This syncline presents continental detrital sediments ranging from U.Carboniferous to L.Triassic. In the U.Carboniferous, magmatic activity begins with the Moriaz Layers acid volcanics that are considered as a lateral equivalent of the Stephanian Courchevel Conglomerates. In Permian times, parts of an alluvial fan seem to occupy the north of the study area (gray and green conglomeratic sandstone). Southwards these inter-finger with flood plain sediments (red slate) including a locally oolitic limestone. Volcanic detritus is important in the Permian. Tourmalinite pebbles are frequent and seem to be related to the regional Permian magmatism. Albitization of feldspars is general in the Carboniferous and the Permian. The Permo-triassic typically shows microcline bearing dolomitic sandstones. In the Scythian quartzites orthoclase is the dominant feldspar. The quartzites are overlain by L.Triassic evaporites identified by the sulfur isotope ratio of their gypsum. The morphology of the zircons in the sandstones has been investigated using the typological method of J.P. Pupin. Regional Permian magmatism apparently produces volcanics of the calc-alkalic and tholeiitic series as well as a high level granitic intrusion of anatectic origin. The uranium occurrences are strata-bound on a kilometric and hecto-metric scale. They are developed almost exclusively in the gray variety of the Permian sandstones whose gray and red varieties are always barren. Within this unit, the mineralization impregnates irregularly distributed lenses and pods of coal material. Uranium is accompanied by vanadium occurring as roscoelite. The association U-V, of bio-philic character, reflects the concentration in the sedimentary environment and argues for a quite indirect relation with the

  13. Enigmatic diamonds in Archean calc-alkaline lamprophyres of Wawa, southern Ontario, Canada (United States)

    de Stefano, Andrea; Lefebvre, Nathalie; Kopylova, Maya


    A suite of 80 macrodiamonds recovered from volcaniclastic breccia of Wawa (southern Ontario) was characterized on the basis of morphology, nitrogen content and aggregation, cathodoluminescence (CL), and mineral inclusions. The host calc-alkaline lamprophyric breccias were emplaced at 2.68-2.74 Ga, contemporaneously with voluminous bimodal volcanism of the Michipicoten greenstone belt. The studied suite of diamonds differs from the vast majority of diamond suites found worldwide. First, the suite is hosted by calc-alkaline lamprophyric volcanics rather than by kimberlite or lamproite. Second, the host volcanic rock is amongst the oldest known diamondiferous rocks on Earth, and has experienced regional metamorphism and deformation. Finally, most diamonds show yellow-orange-red CL and contain mineral inclusions not in equilibrium with each other or their host diamond. The majority of the diamonds in the Wawa suite are colorless, weakly resorbed, octahedral single crystals and aggregates. The diamonds contain 0-740 ppm N and show two modes of N aggregation at 0-30 and 60-95% B-centers suggesting mantle storage at 1,100-1,170°C. Cathodoluminescence and FTIR spectroscopy shows that emission peaks present in orange CL stones do not likely result from irradiation or single substitutional N, in contrast to other diamonds with red CL. The diamonds contain primary inclusions of olivine (Fo92 and Fo89), omphacite, orthopyroxene (En93), pentlandite, albite, and An-rich plagioclase. These peridotitic and eclogitic minerals are commonly found within single diamonds in a mixed paragenesis which also combines shallow and deep phases. This apparent disequilibrium can be explained by effective small-scale mixing of subducted oceanic crust and mantle rocks in fast “cold” plumes ascending from the top of the slabs in convergent margins. Alternatively, the diamonds could have formed in the pre-2.7-2.9 Ga cratonic mantle and experienced subsequent alteration of syngenetic inclusions

  14. Geotectonic significance of Neoproterozoic amphibolites from the Central Eastern Desert of Egypt: A possible dismembered sub-ophiolitic metamorphic sole (United States)

    Farahat, E. S.


    Supra-subduction zone ophiolites in the Egyptian Central Eastern Desert (CED) occur as clusters in its northern (NCEDO) and southern (SCEDO) parts, displaying abundant island arc-boninitic and MORB/island-arc geochemical affinities, respectively. An amphibolite belt, including the investigated massive to slightly foliated Wadi Um Gheig (WUG) amphibolites, is exposed in the southeast most of the NCEDO thrusting over the El Sibai gneissic association and intruded by late- to post-orogenic granitoids and gabbros. The WUG rocks are metamorphosed under epidote amphibolite to common amphibolite facies. The amphiboles are calcic and represented by actinolitic hornblende to magnesio-hornblende in the epidote amphibolites and magnesio- to ferro-hornblende in the amphibolites. Plagioclase composition varies from pure albite (An3-8) in the epidote amphibolites to andesine and labradorite (An36-65) in the amphibolites. The estimated P-T conditions are in favor of their metamorphism under epidote amphibolite (c. 550-600 °C and 2-3 ± 1.5 kbar) and amphibolite (c. 618-720 °C and 3-6 ± 1.5 kbar) facies. The peak metamorphic conditions point to a burial depth of c.15-20 km. Geochemically, the WUG amphibolites show basaltic to andesitic compositions of tholeiitic affinity. They display LILE-enriched MORB-normalized patterns with negative Nb anomalies characteristic of the subduction-related rocks. However, their chondrite-normalized rare-earth element (REE) patterns vary from LREE-depleted (LaN/YbN = 0.29 to 0.49) to LREE-enriched (LaN/YbN = 2.97 to 3.74). Few samples show major and trace element contents typical of boninitic rocks, including U-shaped REE pattern. On the standard tectonic discrimination diagrams the WUG amphibolites plot mostly in the island-arc fields with some samples of MORB and boninitic affinities. Greenschist facies metamorphosed NCEDO obviously share these geochemical characteristics, implying formation in the same tectonic environment, i.e. forearc basin

  15. Crystallization conditions and petrogenesis of the lava dome from the ˜900 years BP eruption of Cerro Machín Volcano, Colombia (United States)

    Laeger, Kathrin; Halama, Ralf; Hansteen, Thor; Savov, Ivan P.; Murcia, Hugo F.; Cortés, Gloria P.; Garbe-Schönberg, Dieter


    The last known eruption at Cerro Machín Volcano (CMV) in the Central Cordillera of Colombia occurred ˜900 years BP and ended with the formation of a dacitic lava dome. The dome rocks contain both normally and reversely zoned plagioclase (An24-54), unzoned and reversely zoned amphiboles of dominantly tschermakite and pargasite/magnesio-hastingsite composition and olivine xenocrysts (Fo = 85-88) with amphibole/clinopyroxene overgrowth, all suggesting interaction with mafic magma at depth. Plagioclase additionally exhibits complex oscillatory zoning patterns reflecting repeated replenishment, fractionation and changes in intrinsic conditions in the magma reservoir. Unzoned amphiboles and cores of the reversely zoned amphiboles give identical crystallization conditions of 910 ± 30 °C and 360 ± 70 MPa, corresponding to a depth of about 13 ± 2 km, at moderately oxidized conditions (f = +0.5 ± 0.2 ΔNNO). The water content in the melt, calculated based on amphibole chemistry, is 7.1 ± 0.4 wt.%. Rims of the reversely zoned amphiboles are relatively enriched in MgO and yield higher crystallization temperatures (T = 970 ± 25 °C), slightly lower melt H2O contents (6.1 ± 0.7 wt.%) and overlapping pressures (410 ± 100 MPa). We suggest that these rims crystallized following an influx of mafic melt into a resident magma reservoir at mid-crustal depths, further supported by the occurrence of xenocrystic olivine. Crystallization of biotite, albite-rich plagioclase and quartz occurred at comparatively low temperatures (probably <800 °C) during early stages of ascent or storage at shallower levels. Based on amphibole mineral chemistry, the felsic resident melt had a rhyolitic composition (71 ± 2 wt.% SiO2), whereas the hybrid magma, from which the amphibole rims crystallized, was dacitic (64 ± 3 wt.% SiO2). The bulk rock chemistry of the CMV lava dome dacites is homogenous. They have elevated (La/Nb)N ratios of 3.8-4.5, typical for convergent margin magmas, and display

  16. Geochemistry and mineralogy of the Late Permian coals from the Songzao Coalfield, Chongqing,southwestern China

    Institute of Scientific and Technical Information of China (English)


    Mineralogy and geochemistry of the four main workable coal seams (No.6, No.7, No.8, and No.11) of Late Permian age from the Songzao Coalfield, Chongqing, Southwest China, were examined using in- ductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), cold-vapor absorption spectrometry (CV-AAS), ion-selective electrode (ISE), scanning electron mi- croscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDX), and X-ray diffraction analysis (XRD). The results showed that the main workable No.8 Coal that accounts for about 60% of the total coal reserves in the Songzao Coalfield was not enriched in hazardous trace elements. The No.11 Coal has high concentrations of alkaline elements, Be (9.14 μg/g), Sc (12.9 μg/g), Ti (9508 μg/g), Mn (397 μg/g), Co (23.7 μg/g), Cu (108 μg/g), Zn (123 μg/g), Ga (32 μg/g), Zr (1304 μg/g), Nb (169 μg/g), Hf (32.7 μg/g), Ta (11.4 μg/g), W (24.8 μg/g), Hg (0.28 μg/g), Pb (28.1 μg/g), Th (24.1 μg/g), and rare earth elements (509.62 μg/g). The concentration of Nb and Ta in the No. 11 Coal is higher than the industrial grade, and their potential utilization should be further studied. Besides pyrite, quartz, calcite, and clay minerals, trace minerals including chalcopyrite, marcasite, siderite, albite, mixed-layer clay minerals of illite and smectite, monazite, apatite, anatase, chlorite, and gypsum were found in the No.11 Coal. It should be noted that alabandite of hydrothermal origin and anatase occurring as cement were identi- fied in coal. In addition, the clayey microbands derived from alkaline volcanic ashes were identified in the coal. The dominant compositions of these clayey microbands were mixed-layer clay minerals of illite and smectite, which were interlayered with organic bands. The modes of occurrence of alkaline volcanic ash bands indicate that the volcanic activities were characterized by the multiple eruptions, short time interval and small scale for each eruption

  17. Petrology and geochemistry of eclogites from the Kechros Metamorphic Complex in eastern Rhodope (NE Greece) (United States)

    Mposkos, Evripides; Baziotis, Ioannis; Asimow, Paul


    The Rhodope Metamorphic Province (RMP) is one of the major tectonic units in northern Greece. It consists of different tectonometamorphic complexes involved in the Alpine collisional history between the Eurasian and African plates. In eastern Rhodope a Jurassic UHP metamorphism is documented in the uppermost Kimi Complex by the presence of microdiamond inclusions in garnets from pelitic gneisses (Mposkos and Kostopoulos 2001). Partially or completely amphibolitized eclogites are common recording P-T conditions >1.8 GPa and 7500C for the eclogitic stage and 1.5 GPa and 8200C for an early stage of exhumation (Bauer et al. 2007). In the underlying Kechros Complex lenses of kyanite eclogites in orthogneisses with Permian ages of their gabbroic protoliths and of common eclogites within metapelites associated with serpentinized peridotites occur. The mineral assemblage of the kyanite eclogites is Grt+Omp(Jd35-55)+Ky+sodic-Tr+Hbl+Zo/Czo+Phg+Qtz+Rt. Garnet shows growth zoning with core composition Grs0.19Prp0.15Alm0.63Sps0.03 and rim composition Grs0.20Prp0.27Alm0.52Sps0.01. Matrix omphacite is in textural equilibrium with kyanite, but commonly it is replaced by Ca-amphibole. A decrease in jadeite component from the core to the rim indicates a re-equilibration tendency during exhumation. Temperatures of 550-6000C and minimum pressure of 1.5 GPa are obtained with Grt-Cpx geothermometry and the jadeite component (Jd55) in omphacite. However, the coexistence of matrix omphacite with kyanite constrains the minimum pressure to 2.1 GPa assuming H2O activity equal to unity. In the common eclogites the HP mineral assemblage is Grt+Omp+Czo+Gln+Ca-Amph. Glaucophane is present only as inclusions in garnet. In retrogressed samples Ca-amphibole replaces garnet and omphacite. It shows compositional zoning with increasing Al2O3 content from 5.0 wt% in the core up to 20.0 wt% in the rim. In the eclogites subjected to extensive retrogression, margarite associated with zoisite and albite

  18. Bald Friar Metabasalt and Kennett Square Amphibolite: Two Iapetan Ocean Floor Basalts (United States)

    Smith, R.C., II


    The Bald Friar Metabasalt (BFM) and Kennett Square Amphibolite (KSA) are basaltic units found in the Piedmont of southeastern Pennsylvania. The BFM is also recognized in northern Maryland. Both are believed to represent fragments of the floor of the Iapetus Ocean, but are not known occur in direct association with one another. The BFM typically occurs as small fragments having typical stratigraphic thicknesses of 2.5 m, and composed of greenish, fine-grained chlorite-epidote-actinolite-albite metabasalt in ophiolite me??lange. One bed of pillow basalt has been found at the type locality, Bald Friar, Cecil County, Maryland. Even though outcrops of BFM are highly discontinuous, they have a remarkable chemical uniformity over a strike length of 143 km and appear to be equivalent to the Caldwell Group 1b metabasalt of the Thetford, Quebec, area. The BFM is typically associated with ultramafic fragments and may be affiliated with the Baltimore Mafic Complex (BMC), from which a baddeleyite date of 442 +/- 7 Ma (Silurian) has been obtained. The BFM is probably a back arc basin basalt (BABB). Pod and schlieren chromite compositions suggest an island arc environment for the BMC itself. The poorly defined, informal "Conowingo Creek metabasalt" of Lancaster County, Pennsylvania, occurs on the north margin of the BMC and appears to be a fore arc boninite. The BFM and associated ultramafic fragments serve as a field-mappable marker for the structural equivalent of the Baie Verte-Brompton line in southeastern Pennsylvania and northern Maryland. Steatization of the associated ultramafic fragments has produced zones of extremely low competence that facilitated and localized thrusts of presumed Silurian age and later Alleghanian folding. The KSA typically occurs as much larger bodies having lengths of 3 km and composed of dark, medium-grained hornblende-plagioclase-clinopyroxene gneiss. No ultramafic rocks or me??lange have been recognized with the KSA. In Pennsylvania, the KSA

  19. Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt (United States)

    Benson, Thomas R.; Mahood, Gail A.


    The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at ~ 15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of low-temperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre- and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single ~ 20 × 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins ~ 300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are

  20. Wall-rock metasomatism of carbonaceous terrigenous rocks in the Lena gold district (United States)

    Rusinov, V. L.; Rusinova, O. V.; Kryazhev, S. G.; Shchegol'Kov, Yu. V.; Alysheva, E. I.; Borisovsky, S. E.


    The Lena gold district is situated in the fold-and-shear belt of the southern framework of the Siberian Platform. The gold deposits are hosted in the Riphean-Vendian Khomolkho and Aunakit formations, revealing the strict control of ore mineralization by folding and shearing. The microstructure of metasomatically altered ore-bearing carbonaceous sedimentary rocks at the Sukhoi Log, Golets Vysochaishy, and Verninsky deposits (the latter includes the Pervenets vein zone) testifies to parallelism in the development of shearing, foliation, and ore-forming metasomatism. The local pressure gradients are marked by removal of silica from pressured zones into opened cleavage fractures and pockets. Two metasomatic stages are recognized: (1) early sodic metasomatism, which is characterized by the assemblage of magnesian siderite and paragonite, and (2) late potassic metasomatism, with formation of muscovite in association with sideroplesite and ankerite. The rocks altered at the early stage are distinguished by elevated Ni, Cr, and probably PGE contents. The second stage, close in age to the emplacement of Hercynian granitic plutons, was accompanied by the gain of chalcophile metals and deposition of the bulk of gold. In mineral composition, the metasomatic rocks are close to beresites, but the alteration differed in somewhat elevated alkalinity, so that microveinlets of albite and potassium feldspar occur in the ore zone together with muscovite. The ratio of modal muscovite to paragonite contents in orebodies is substantially higher than in the surrounding metasomatized rocks. This ratio directly depends on the degree of rock permeability and the intensity of the flow of ore-forming solutions. Carbonaceous matter (CM) in the ore zone underwent reworking and redeposition. CM is graphitized to a lesser extent than in the rocks affected by regional metamorphism. The spatial distribution of CM containing nitro and amino groups indicates more oxidizing conditions in the zone of

  1. Brittle deformation in Southern Granulite Terrane (SGT): A study of pseudotachylyte bearing fractures along Gangavalli Shear Zone (GSZ), Tamil Nadu, India. (United States)

    mohan Behera, Bhuban; Thirukumaran, Venugopal; Biswal, Tapas kumar


    High grade metamorphism and intense deformation have given a well recognition to the Southern Granulite Terrane (SGT) in India. TTG-Charnockite and basic granulites constitute the dominant lithoassociation of the area. Dunite-peridotite-anorthosite-shonkinite and syenites are the intrusives. TTG-charnockite-basic granulite have undergone F1 (isoclinal recumbent), F2 (NE-SW) and F3 (NW-SE) folds producing several interference pattern. E-W trending Neoarchean and Palaeoproterozoic Salem-Attur Shear Zone exhibits a low angle ductile thrust as well as some foot print of late stage brittle deformation near Gangavalli area of Tamil Nadu. The thrust causes exhumation of basic granulites to upper crust. Thrusting along the decollement has retrograded the granulite into amphibolite rock. Subsequently, deformation pattern of Gangavalli area has distinctly marked by numerous vertical to sub-vertical fractures mostly dominating along 0-15 and 270-300 degree within charnockite hills that creates a maximum stress (σ1) along NNW and minimum stress (σ3) along ENE. However, emplacement of pseudotachylyte vein along N-S dominating fracture indicates a post deformational seismic event. Extensive fractures produce anastomose vein with varying thickness from few millimeters to 10 centimeters on the outcrop. ICP-AES study results an isochemical composition of pseudotachylyte vein that derived from the host charnockitic rock where it occurs. But still some noticeable variation in FeO-MgO and Na2O-CaO are obtained from different parts within the single vein showing heterogeneity melt. Electron probe micro analysis of thin sections reveals the existence of melt immiscibility during its solidification. Under dry melting condition, albitic rich melts are considered to be the most favorable composition for microlites (e.g. sheaf and acicular micro crystal) re-crystallization. Especially, acicular microlites preserved tachylite texture that suggest its formation before the final coagulation

  2. Geological Characteristics and Genesis of the Spodumene Deposit in Dangba, Barkam, Sichuan Province%四川省马尔康党坝锂辉石矿床地质特征及成因研究

    Institute of Scientific and Technical Information of China (English)

    庞博; 古城会; 李良波; 罗伟; 李剑


    马尔康党坝锂辉石矿位于松潘-甘孜造山带、巴颜喀拉造山带之马尔康复式向斜之南端.矿区出露三叠系地层,断裂、褶皱构造较发育,岩浆岩以燕山晚期二云二长花岗岩为主,是花岗伟晶岩脉的母岩.锂辉石矿体呈大脉状产出,矿石矿物有锂辉石、钽铌铁矿、锰锂矿等,脉石矿物有石英、微斜长石、钠-更长石.矿石结构为细粒-中粒结构,次为交代结构、熔蚀结构.矿石构造以块状构造为主,次为似斑状、浸染状和条带状构造.围岩蚀变主要为锂云母化、白云母化和黑云母化,成因类型为伟晶岩矿床.%Barkam county Dangba spodumene deposit is located in Songpan-Ganzi orogenic belt, the southern tip of the Barkam of the Bayan Har orogenic belt. The mining area outcrops of Triassic strata. Fractures and fold structures are developed. Magmatic rocks contains mostly the late Yanshanian the dimicaceous adamellite, that is parent rocks of granitic pegmatite veins. The orebodies are the large vein outputs. The ore minerals are spodumene, tantalum-niobium-iron ore, lithium manganese ore, and so on. Gangue minerals are quartz, feldspar, albite-oligoclase. The ore structures have fine-grained-medium-grained structure, and then account structure, corrosion structure. Ore constructed to massive structure based, and then porphyritic, disseminated and banded structure. Wall rocks alteration mainly includes lepidolitization, muscovitization and biotitization. Genetic type is pegmatite deposits.

  3. Deep Water Compositions From the Los Angeles Basin and the Origin of Formation Water Salinity (United States)

    Boles, J.; Giles, G.; Lockman, D.


    elevated Ca/Na ratios and K/Na ratios which we attribute to dissolution and albitization of feldspar, mainly plagioclase, at the elevated burial temperatures. As is typical of most formation waters, Mg, Fe, and sulfate ions are highly depleted due to early formed pyrite, Fe-Mg siderite, and dolomite.

  4. Petrogenesis of Garnet-bearing Rocks in the Grandfather Mountain Window, Blue Ridge Province, Western North Carolina (United States)

    Frushour, A. M.; Abbott, R. N.


    The Grandfather Mountain Window in western North Carolina exposes the lowest structural level in the Blue Ridge Province. Rocks in the window constitute a Late Proterozoic basement-cover sequence. The basement consists mainly of Blowing Rock Gneiss (sic, porphyroblastic schist) and Wilson Creek Gneiss, both overlain unconformably by the Grandfather Mountain Formation. All of these rocks have been pervasively overprinted by greenschist facies metamorphism. The typical greenschist mineral assemblage involves combinations of chlorite, muscovite, biotite, actinolite, epidote, calcite, quartz, albite and K-feldspar. Garnet discovered in basement rock calls into question the metamorphic grade. The average garnet (core-rim) is (Fe1.63-1.71Mn0.64-0.77Ca0.52-0.37Mg0.10-0.12)Al1.98-1.96Si3.06-3.04O12; the average biotite is (K0.96Na0.06Ca0.02)(Fe1.73Mg0.87Mn0.02Ti0.04Al0.23)(Si2.83Al1.17)O10(OH)2; the average muscovite is (K1.03Na0.02Ca0.02)(Al1.57Fe0.26Mg0.16Ti0.01)(Si3.31Al0.69)O10(OH)2. Thermometry involving Fe-Mn-Mg components in these minerals gives 766°C (+/- 91°C) at 13.6 kbars (+/- 1.4 kbar), respectively. There are at least four explanations for garnet in these rocks: (1) Garnet may have been stabilized in the greenschist facies by non-AFM components (esp. Mn), but the compositions are not unusual for metamorphic garnet, biotite and muscovite, and the calculated temperatures are too high for greenschist facies. (2) The garnet may be relict from earlier contact metamorphism, but the garnet is not spatially related to otherwise common metamorphosed (greenschist facies) mafic dikes. (3) The garnet is a product of heating during mylonitization. Finally, and most likely, (4) the garnet may be relict from an earlier episode of regional metamorphism. Samples of porphyroblastic schist and greenstone from the same outcrop give low temperature, greenschist facies conditions.

  5. Experimental study of the hydrogeochemical properties of the Hontomin cap rock under CO2 supercritical conditions (United States)

    Cama, Jordi; Soler, Josep M.; Davila, Gabriela; Luquot, Linda


    Gabriela Dávila, Linda Luquot, Jordi Cama and Josep M. Soler Departament de Geociències, Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA), CSIC, Barcelona 08034. The main cap rock for CO2 injection at the PDT Hontomin site (Spain) is a marly shale made up of calcite (56 %), quartz (21%), illite (17%) clinochlore (3%) and others (albite, gypsum, anhydrite, pyrite) (~3%). Contact with CO2-rich acid brines may induce the dissolution of these minerals. Since the brine contains sulfate, gypsum (or anhydrite at depth) may precipitate, which may coat the surface of the dissolving calcite grains and cause their passivation. These mineral reactions will also induce changes in porosity and permeability. Percolation laboratory experiments with Hontomin shale rock cores under controlled pCO2 (8 MPa) are being performed to quantify these processes. In mechanically fractured cores (7.5 mm in diameter and 18 mm in length), two synthetic brines (a sulfate-free solution and a version of the Hontomin formation brine (sulfate solution)) were injected into the rock at constant flow rates (0.2, 1 and 60 mL/h) under CO2 supercritical conditions (pCO2 = 8 MPa and T = 60 °C). As the pH of the injecting brines in equilibrium with a pCO2 of 8 MPa is acidic (~3), it was observed that in the case of the sulfate-free brine experiments, the main processes that yield variation in the hydrodynamic behavior of the fractured rock was the dissolution of calcite, Si-bearing minerals, clinochlore and pyrite. In the sulfate-rich brine experiments, the dissolution of calcite and Si-bearing minerals also occurred, together with gypsum precipitation in the experiments run at low flow rates. As a result, initial fracture permeability tends (i) to stabilize or increase when the cap rock interacts with the sulfate-free brine and (ii) to decrease as the rock interacts with the sulfate-rich brine. The interpretation (reactive transport modeling) of the changes in mineralogy and solution

  6. What Are the Time Scales for Carbonate Mineral Sequestration in the Subsurface? (United States)

    Steefel, C. I.; Landrot, G.; Bolton, E. W.; Pride, S. R.


    Mineral trapping of CO2 in the subsurface is acknowledged to be the most secure form of sequestration, but some studies have suggested that the process is extremely slow, perhaps on the order of 10,000 years or more. But what are the arguments for these long time scales based on? Certainly part of it has to do with the slow dissolution rates of silicates needed to provide a source of cations (Ca2+, Mg2+, and Fe2+) and alkalinity for carbonate precipitation. Rates of dissolution for many silicates are very slow (e.g., albitic plagioclase and chlorite), while other silicate minerals (anorthitic feldspar, olivine) dissolve appreciably faster. Determining which mineral is rate-limiting in the case of the faster dissolving silicates (is it the dissolving silicate or precipitating carbonate?), however, is not always straightforward without a careful analysis of dissolution and precipitation as a coupled process. We use micro-continuum modeling to address the issue of time scales for carbonate mineral trapping of CO2. Two sets of simulations have been carried out: 1) largely generic simulations at the centimeter scale that include heterogeneous distributions of both residually trapped scCO2 and reactive mineral phases (Ca-bearing plagioclase and chlorite), and 2) flow plus diffusion and pure diffusion simulations of the reactivity of a reservoir sandstone from a scCO2 pilot injection site at Cranfield, Mississippi. The first set of simulations are designed specifically to examine the assumption that the reservoir within which carbonate mineral precipitation might occur is well-mixed and therefore characterized everywhere by the low pH values typical of brine in equilibrium with supercritical CO2. Our analysis of physically and chemically heterogeneous subsurface materials, especially during the residual trapping stage, suggest that local chemical microenvironments can develop in which pH, alkalinity, and cation concentrations rise sufficiently high that substantial

  7. Solid oxide electrolyser cell

    Energy Technology Data Exchange (ETDEWEB)

    Hoejgaard Jensen, S.


    Solid oxide fuel cells (SOFCs) produced at Riso National Laboratory was tested as steam electrolysers under various current densities, operating temperatures and steam partial pressures. At 950 deg. C and a cell voltage of 1.48V the current density was -3.6 A/cm{sup 2} with app. 30% H{sub 2} + 70% H{sub 2}O in the inlet gas and a H{sub 2}O utilization of app. 40%. The tested SOECs were also used for CO{sub 2} electrolysis. Economy studies of CO and H2 production show that especially H{sub 2} production can be competitive in areas with cheap electricity. Assuming the above described initial performance and a lifetime of 10 years it is possible to achieve a production price of 0.7 US dollar/kg H{sub 2} with an electricity price of 1.3 US cent/kWh. The cell voltage was measured as function of time. In test of about two month of duration a long-term degradation was observed. At 850 deg. C, -0.5 A/cm{sup 2} with 50 vol% H{sub 2} the degradation rate was app. 20 mV/1000h. It was shown that the degradation happens at Ni/YSZ-electrode. The long term degradation is probably caused by coarsening of the Ni-particles. After onset of electrolysis operation a transient passivation/reactivation phenomena with duration of several days was observed. It was shown that the phenomenon is attributed to the SiO{sub 2} contamination at the Ni/YSZ electrode-electrolyte interface. The SiO{sub 2} arises from the albite glass sealing (NaAlSi{sub 3}O{sub 8}) that surrounds the electrode. Si may enter the Ni/YSZ electrode via the reaction Si(OH){sub 4}(g) {r_reversible} SiO{sub 2}(l)+H{sub 2}O(g). At the active sites of the Ni/YSZ electrode steam is reduced via the reaction H{sub 2}O - 2e {yields} H{sub 2}+O{sup 2-} . This shifts the equilibrium of the first reaction to form SiO{sub 2}(l) at the active sites. After a certain time the sealing crystallizes and the SiO{sub 2}(l) evaporates from the active sites and the cell reactivates. The passivation is shown to relate to a build up of a

  8. 西安碑林博物馆库房降尘的检测分析

    Institute of Scientific and Technical Information of China (English)

    牟炜; 金普军; 南普恒


    With the environment scanning electron microscope (SEM), EDAX energy dispersive spectrometer and X-ray diffractometer (XRD), the dust falls of the new and old storehouses of the Beilin (Stele Forest) Museum are tested. The results show that the compositions of the new and old storehouses of the Beilin Museum are rather complicated:the distributions of the main elements are roughly the same;the dust fall in the old storehouses has low proportion of organic compounds, but that in the new storehouses has rather high proportion;the main ingredients of the dust are quartz (SiO2), calcium carbonate (CaCO3), gypsum (CaSO4•2H2O) and albite (NaAlSi3O8), which bear certain acidity. The characteristics of the compositions of the dust falls in the storehouses show that dust-prooifng processes should be applied to the paper artifacts such as the calligraphy and painting artworks stored in these storehouses to prevent the fungi and acidic materials in the dust from damaging the ifber structures of the paper artifacts.%本文利用了环境电子显微镜/能谱仪(SEM/EDAX),X-射线衍射仪(XRD)等方法对碑林博物馆新旧库房中的降尘进行了检测分析。结果发现:碑林新旧库房中的灰尘成分复杂,主要元素分布特征基本一致;老库房灰尘有机物含量显著下降,新灰尘中则存在着大量的有机物;灰尘中主要物质为石英(SiO 2),碳酸钙(CaCO 3),石膏(CaSO4·2H 2 O)和钠长石(NaAlSi 3 O8),具有一定的酸性。库房降尘的组成结构特点说明对其中保存的字画类文物需要开展必要的防尘处理,以避免灰尘中霉菌和酸性物质对纸张纤维结构的破坏作用。

  9. Abiotic degradation rates for carbon tetrachloride and chloroform: Final report.

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Humphrys, Daniel R.; Wietsma, Thomas W.; Truex, Michael J.


    This report documents the objectives, technical approach, and progress made through FY 2012 on a project initiated in FY 2006 to help address uncertainties related to the rates of hydrolysis in groundwater for carbon tetrachloride (CT) and chloroform (CF). The project also sought to explore the possible effects of contact with minerals and sediment (i.e., heterogeneous hydrolysis) on these rates. We conducted 114 hydrolysis rate experiments in sealed vessels across a temperature range of 20-93 °C for periods as long as 6 years, and used the Arrhenius equation to estimate activation energies and calculate half-lives for typical Hanford groundwater conditions (temperature of 16 °C and pH of 7.75). We calculated a half-life of 630 years for hydrolysis for CT under these conditions and found that CT hydrolysis was unaffected by contact with sterilized, oxidized minerals or Hanford sediment within the sensitivity of our experiments. In contrast to CT, hydrolysis of CF was generally slower and very sensitive to pH due to the presence of both neutral and base-catalyzed hydrolysis pathways. We calculated a half-life of 3400 years for hydrolysis of CF in homogeneous solution at 16 °C and pH 7.75. Experiments in suspensions of Hanford sediment or smectite, the dominant clay mineral in Hanford sediment, equilibrated to an initial pH of 7.2, yielded calculated half-lives of 1700 years and 190 years, respectively, at 16 °C. Experiments with three other mineral phases at the same pH (muscovite mica, albite feldspar, and kaolinite) showed no change from the homogeneous solution results (i.e., a half-life of 3400 years). The strong influence of Hanford sediment on CF hydrolysis was attributed to the presence of smectite and its ability to adsorb protons, thereby buffering the solution pH at a higher level than would otherwise occur. The project also determined liquid-vapor partition coefficients for CT under the temperatures and pressures encountered in the sealed vessels that

  10. Origin and evolution of ore-forming fluids in the Hemushan magnetite-apatite deposit, Anhui Province, Eastern China, and their metallogenic significance (United States)

    Luo, Gan; Zhang, Zhiyu; Du, Yangsong; Pang, Zhenshan; Zhang, Yanwen; Jiang, Yongwei


    The Middle-Lower Yangtze River Metallogenic Belt in the northern Yangtze Block is one of the most important economic mineral districts in China. The Hemushan deposit is a medium-class Fe deposit located in the southern part of the Ningwu iron ore district of the Middle-Lower Yangtze River Metallogenic Belt. The Fe-orebodies are mainly hosted in the contact zone between diorite and Triassic marble. The actinolite-phlogopite-apatite-magnetite ore shows metasomatic/filling textures and disseminated/mesh-vein structures. Based on evidences and petrographic observations, the ore-forming process can be divided into three distinct periods-the early metallogenic period (albite-diopside stage), the middle metallogenic period (magnetite stage and hematite stage), and the late metallogenic period (quartz-pyrite stage and carbonate stage). Fluid inclusion studies show four types of inclusions: type I daughter mineral-bearing three-phase inclusions (L + V + S), type II vapor-rich two-phase inclusions (L + V), type III liquid-rich two phase inclusions (L + V), and minor type IV liquid-phase inclusions (L). Apatites from the magnetite stage contain type I, type II and type III inclusions; anhydrites from the hematite stage mainly contain abundant type II inclusions and relatively less type I inclusions; quartz and calcite from the late metallogenic stage are mainly characterized by type III inclusions. Laser Raman spectroscopy and microthermometry of fluid inclusions show that the ore-forming fluids broadly correspond to unsaturated NaCl-H2O system. From the magnetite stage to the carbonate stage, the ore-forming fluids evolved from moderate-high temperature (average 414 °C), moderate salinity (average 25.01 wt.% NaCl equiv.) conditions to low temperature (average 168 °C), low salinity (average 6.18 wt.% NaCl equiv.) conditions. Hydrogen and oxygen isotopic studies indicate that the ore-forming fluid during the early stage of middle metallogenic period was mainly of magmatic

  11. Mineralogical, IR-spectral and geochemical monitoring of hydrothermal alteration in a deformed and metamorphosed Jurassic VMS deposit at Arroyo Rojo, Tierra del Fuego, Argentina (United States)

    Biel, C.; Subías, I.; Acevedo, R. D.; Yusta, I.; Velasco, F.


    The Arroyo Rojo Zn-Pb-Cu volcanogenic massive sulfide deposit is the main deposit of the Fin del Mundo District in the Fuegian Andes, Argentina. This deposit is hosted by a Middle Jurassic volcanic and volcanoclastic sequence forming the Lemaire Formation. The latter consists, from the base up, of the following: rhyolitic and dacitic porphyritic rocks, ignimbrite, tuff, and flow. It is underlain by a pre-Jurassic basement and overlain by the hyaloclastic andesites of the Yahgán Formation. The Arroyo Rojo consists of stacked lenticular lenses that are associated with disseminated mineralization in both the footwall and the hanging wall. The internal structure of the ore lenses is marked by the occurrence of massive, semi-massive and banded facies, along with stringer and brecciated zones and minor ore disseminations. The mineral assemblage comprises mainly pyrite and sphalerite, with minor amounts of galena and chalcopyrite and rare pyrrhotite, arsenopyrite, tetrahedrite and bournonite. The ores and the volcanic host rocks have metamorphosed to greenschist facies and were overprinted by a penetrative tectonic foliation, which led to the development of mylonitic, and cataclastic textures, recrystallization and remobilization. Primary depositional characteristics and regional and hydrothermal alteration patterns were preserved despite deformation and metamorphism. Therefore, primary banding was preserved between facies boundaries. In addition, some remnants of magmatic origin are recognizable in preserved phenocrysts and volcaniclastic phenoclasts. Most of the volcanic and volcaniclastic rocks of the host sequence show a rhyolitic to rhyo-dacitic composition. Regional seafloor alteration, characterized by the presence of clinozoisite, Fe-chlorite and titanite, along with quartz and albite, is partially obliterated by hydrothermal alteration. The hydrothermal alteration is stratabound with the following assemblages, which developed from the base to top: (1) Quartz

  12. CO2-rich geothermal areas in Iceland as natural analogues for geologic carbon sequestration (United States)

    Thomas, D.; Maher, K.; Bird, D. K.; Brown, G. E.; Arnorsson, S.


    -temperature and late stage low-temperature alteration. Imaging results from scanning electron microscopy show that calcite has replaced hydrothermally altered silicate minerals, such as albitic plagioclase. CO2-rich low-temperature fluids are not in equilibrium with correlative high-temperature hydrothermal mineral assemblages, indicating that the kinetics of mineral dissolution and secondary mineral precipitation, along with fluid residence times, are important controls on CO2 alteration and mineral formation at low temperatures. Our results have implications for predicting mineral product formation and trace element release during geologic carbon sequestration into hydrothermally altered basalts.

  13. Integrated Numerical Simulation of Thermo-Hydro-Chemical Phenomena Associated with Geologic Disposal of High-Level Radioactive Waste (United States)

    Park, Sang-Uk; Kim, Jun-Mo; Kihm, Jung-Hwi


    A series of numerical simulations was performed using a multiphase thermo-hydro-chemical numerical model to predict integratedly and evaluate quantitatively thermo-hydro-chemical phenomena due to heat generation associated with geologic disposal of high-level radioactive waste. The average mineralogical composition of the fifteen unweathered igneous rock bodies, which were classified as granite, in Republic of Korea was adopted as an initial (primary) mineralogical composition of the host rock of the repository of high-level radioactive waste in the numerical simulations. The numerical simulation results show that temperature rises and thus convective groundwater flow occurs near the repository due to heat generation associated with geologic disposal of high-level radioactive waste. Under these circumstances, a series of water-rock interactions take place. As a result, among the primary minerals, quartz, plagioclase (albite), biotite (annite), and muscovite are dissolved. However, orthoclase is initially precipitated and is then dissolved, whereas microcline is initially dissolved and is then precipitated. On the other hand, the secondary minerals such as kaolinite, Na-smectite, chlorite, and hematite are precipitated and are then partly dissolved. In addition, such dissolution and precipitation of the primary and secondary minerals change groundwater chemistry (quality) and induce reactive chemical transport. As a result, in groundwater, Na+, Fe2+, and HCO3- concentrations initially decrease, whereas K+, AlO2-, and aqueous SiO2 concentrations initially increase. On the other hand, H+ concentration initially increases and thus pH initially decreases due to dissociation of groundwater in order to provide OH-, which is essential in precipitation of Na-smectite and chlorite. Thus, the above-mentioned numerical simulation results suggest that thermo-hydro-chemical numerical simulation can provide a better understanding of heat transport, groundwater flow, and reactive

  14. Management of city aquifers from anthropogenic activities: Example of the Windhoek aquifer, Namibia (United States)

    Mapani, Benjamin S.; Schreiber, Ute

    As the city of Windhoek is growing rapidly, it has become increasingly obvious that dangers to the underlying groundwater aquifer have become imminent, and need addressing immediately. Water infiltration and the transportation of contaminants from anthropogenic activities through soils into the bedrock and hence the aquifer involve soil maturity, chemical and microbial processes and the climate of a particular area. The thin immature soil horizon (circa 5-20 cm) over the Windhoek schist implies that most areas of the city are built directly on bedrock, making the aquifer vulnerable. Anthropogenic activities from the use of pesticides for weed control, oil spills, toxic chemical spills, dumping of undesired substances by residents and high fertilizer application rates for lawns can lead to the contamination of groundwater. The result of our study show that the soil composition in Windhoek lacks mature clay minerals and is enriched in micas, quartz and albite. Some areas in the northern and southern industrial areas show contamination in heavy metals Pb, Zn, Cu and Ni. To the west of the city, close to the textile factory, soils are contaminated with ammonium compounds. The hydrochemistry of these pesticides and fertilizers can cause severe pollution to the groundwater if the practice is not carefully monitored. In addition, the rapid expansion of uncontrolled settlements without proper sanitation and reticulation has made the problems much more difficult. The geology of the city of Windhoek consists of the Kuiseb Schist, locally known as the “Windhoek Schist” and amphibolites. The Kuiseb schist possesses pervasive cleavage that renders the underlying lithology to be permeable to percolating water and fluids from the surface into the aquifer. The fissility and fracture density of the schist imply that leakage of surface waters, phenols, septic tank spills and industrial contaminants may reach the aquifer in unusually high rainfall years. Organic fuels and oils

  15. Reactive transport modeling of CO2 injection in the Farnsworth, Texas hydrocarbon field (United States)

    Ahmmed, B.; Appold, M. S.; McPherson, B. J. O. L.; Grigg, R.; White, M. D.


    The Farnsworth hydrocarbon field in northern Texas has been an experimental site for CO2 sequestration and enhanced oil recovery for the U.S. Department of Energy-sponsored Southwest Partnership (SWP) since April, 2013. CO2 is to be injected into the Pennsylvanian Morrow Sandstone at a rate of 200,000 tonnes per year for at least five years. The Morrow is a quartz-rich sandstone that lies at a depth of about 2400 m. Pore water in the Morrow has a total dissolved solids content of about 3600 mg/L dominated by Na, Cl, bicarbonate, and Ca. A reactive solute transport model was constructed for a 1700 × 1700 × 95 m volume using the TOUGHREACT software and the ECO2N equation of state for aqueous brine and CO2. Simulations were carried out to 100 years. The results showed immiscible CO2 gas to be concentrated in a lateral plume extending radially from the well screen, its ascent impeded by vigorous lateral groundwater flow in the more permeable upper Morrow. CO2 was much more widespread in aqueous solution, lowering pH throughout much of the model volume after 100 years, to a minimum of about 4.7. The low reactivity of the Morrow Sandstone due to its quartz-rich matrix and dilute pore fluid resulted in little mineral precipitation or dissolution, with net volume changes for any mineral no higher than order 10-4. The simulations predicted net dissolution of albite, calcite, and chlorite, and net precipitation of dawsonite, illite, and magnesite. The Morrow matrix was predicted to undergo slight net dissolution overall, resulting in porosity increases of up to 0.01%, suggesting that the Morrow would be resistant to significant changes in hydraulic properties as a result of the proposed amount of CO2 injection. For the 100 year simulation times calculated thus far, only a small fraction of the injected CO2 would be sequestered as carbonate minerals, with most of the injected CO2 dissolved in the aqueous phase.

  16. Pore Scale Heterogeneity in the Mineral Distribution and Surface Area of Porous Rocks (United States)

    Lai, Peter; Krevor, Sam


    An important control on rate of interfacial processes between minerals and aqueous solutions such as nucleation of solids, and mineral dissolution and growth is reactive surface area. In geochemical modelling, the continuum hypothesis is based on the assumption that the system can be represented by a sufficiently large number of representative elemental volumes. There has been recent interest in studying the impact of this assumption on reaction-transport coupled systems. In this study, the impact of pore-scale heterogeneity on the distribution of reactive surface area is discussed. 3D images obtained using x-ray micro-tomography were used to characterise the distribution of reactive surface area. The results were compared to independent observations. Mineral identification using x- ray diffraction and fluorescence suggested general agreement with CT analysis. Nitrogen BET surface areas were one to two orders of magnitude higher than measurements from x-ray imagery. Co- registered images of Berea sandstone from x-ray and energy dispersive spectroscopy imagery suggested that quartz, K-feldspar and most clays could be identified. However, minor minerals such as albite and illite did not exhibit enough contrast. In Berea sandstone, mineral surface area fraction was poorly correlated to the mineral volumetric fraction. Clay and feldspar minerals exhibited higher surface area fractions than bulk mineralogy suggested. In contrast, in the Edwards carbonate samples, modal mineral composition correlated with mineral-specific surface area. Berea sandstone revealed a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. Conversely, the carbonate samples suggested a continuous range of pore sizes across length scales. A comparison with pore network model simulations from the literature was made. First order estimates of mineral specific correlations between geometric area measured in the x-ray images were used to convert the CT

  17. Paleotethyan subduction process revealed from Triassic blueschists in the Lancang tectonic belt of Southwest China (United States)

    Fan, Weiming; Wang, Yuejun; Zhang, Yanhua; Zhang, Yuzhi; Jourdan, Fred; Zi, Jianwei; Liu, Huichuan


    The subduction of the Paleotethyan Ocean and subsequent continental collision along the Lancang tectonic belt of the southeastern Paleotethyan belt is a major tectonic event in Southwest China, but the event of the subduction preceding the final collision is still not well-constrained. The mafic blueschists exposed in the Lancang accretionary complex provide crucial records of the Paleotethyan subduction process. In this paper, we present a set of new petrologic, geochronological and geochemical data for the Suyi mafic blueschists in the Lancang metamorphic zone. The mineral assemblage of these blueschists consists of zoned sodic amphibole (25-30%), albite (15-20%), epidote (25-30%), phengite (5-10%), chlorite (~ 5-10%), and minor amounts of actinolite, apatite, sphene, zircon, ilmenite, quartz and secondary limonite. This suggests a prograde metamorphism from ~ 0.5 to ~ 0.9 GPa and retrograde metamorphic overprinting (back to ~ 0.6 GPa) within the temperature range of 300-450 °C. The Suyi blueschists give a zircon U-Pb age of 260 ± 4 Ma and glaucophane minerals formed during prograde metamorphism yield a 40Ar/39Ar plateau age of 242 ± 5 Ma (MSWD = 0.77; P = 0.54). The blueschists have geochemical compositions of subalkaline basalt and show typical OIB-type REE and multi-elemental patterns and εNd(t) values ranging from + 3.35 to + 4.85. Based on available data, it is inferred that the protolith formed at 260 Ma and originated from a basaltic seamount. The basaltic rocks subducted down to 30-35 km depths beneath the Lincang arc to form the epidote blueschists at ~ 242 Ma. The blueschists were subsequently transported to shallower crustal levels in response to the continuous underthrust of the subducted slab and the continent-continent collision in the middle-late Triassic. These results provide a systematic constraint on the tectonic evolution and temporal framework of the southeastern Paleotethyan belt in Southwest China.

  18. Chlorine Behavior in Metasedimentary Rocks during Subduction Zone Metamorphism (United States)

    Barnes, J.; Selverstone, J.; Bebout, G. E.; Penniston-Dorland, S.


    Chlorine concentrations and isotopic compositions were measured in two well-characterized metasedimentary suites from the Catalina Schist and the Western Alps to determine Cl behavior during prograde metamorphism. The Catalina Schist is a subduction zone metamorphic complex in California, USA containing lawsonite-albite (LA) to amphibolite grade rocks recording temperatures of 350 to 750°C and depths of 15 to 45 km. Previous work has shown a decrease in N, B, Cs, As, and Sb concentrations from the LA to the epidote-blueschist facies, with relatively little loss at higher metametamorphic grade [1], and limited Li loss across all grades [2]. Metapelitic rocks from the Western Alps (Schistes Lustres and Lago di Cignana) record temperatures of 350 to 550°C and depths up to 90 km. In contrast to Catalina, N, B, Cs, Ba, and Rb concentrations are relatively uniform across grade [3]. In the Catalina Schist, Cl concentration shows a pattern of loss similar to B and N, from ~100-500 ppm Cl in the LA facies to ~100 ppm in the lawsonite-blueschist facies to relatively uniform concentrations of ~10-25 ppm at higher grades. This loss is likely not due to the breakdown of apatite as P2O5 concentrations remain constant across grade. In the Alps, Cl concentrations are overall lower and show moderate loss from ~10 ppm in the lowest grade to <5 ppm in the highest grade. δ37Cl values range from -1 to +1.6‰ and -1.7 to -0.7‰ in Catalina and the Alps, respectively. Both suites show significant isotopic heterogeneities within a single metamorphic grade and no systematic change in δ37Cl value with increasing grade. We interpret these heterogeneities to be inherited from the protolith. Despite large Cl losses, limited Cl isotope fractionation at high temperatures minimizes variations in δ37Cl value with increasing metamorphic grade. [1] Bebout et al, 1999, EPSL, 171, 53-81 [2] Penniston-Dorland et al, 2012, GCA, 77, 530-545 [3] Bebout et al, 2013, Chem Geol, 342, 1-20

  19. Petrology of HP/LT metapelitic rocks of an accretionary wedge, the Central Pontides, Turkey: evidence for tectonic stacking and syn-subduction exhumation (United States)

    Aygül, Mesut; Okay, Aral; Oberhänsli, Roland


    Cretaceous HP/LT chloritoid-bearing metapelitic rocks crop out widely in the central part of the Pontides, northern Turkey. They are associated with eclogite to blueschist-facies metabasites and represent deep levels of an underplated subduction-accretion complex, which is tectonically overlain by low-grade HP phyllite/metasandstone intercalation along an extensional shear zone. Close to the shear zone, the footwall micaschists consist of quartz, phengite, paragonite, chlorite, rutile with syn-kinematic albite porphyroblast formed by pervasive shearing during exhumation. This type of micaschists is tourmaline-bearing and their retrograde nature suggests high-fluid flux along shear zones. Peak metamorphic assemblages are partly preserved in the chloritoid-micaschist farther away from the shear zone. Three peak metamorphic assemblages are identified and their PT conditions are constrained by pseudosections produced by Theriak-Domino and by Raman spectra of carbonaceous material: 1) garnet-chloritoid-glaucophane with lawsonite pseudomorphs (P: 17.5 ± 1 Kbar, T: 390-450 °C) 2) chloritoid with glaucophane pseudomorphs (P: 16-18 Kbar, T: 475 ± 40 °C) and 3) relatively high-Mg chloritoid (17%) with jadeite pseudomorphs (22-25 Kbar; T: 440 ± 30 °C) in addition to phengite, paragonite, quartz, chlorite, rutile. The last mineral assemblage is interpreted as transformation of the chloritoid + glaucophane assemblage to chloritoid + jadeite paragenesis with increasing pressure. Absence of tourmaline suggests that the chloritoid-micaschist did not interact with B-rich fluids during zero strain exhumation. Peak metamorphic assemblages and PT estimates suggest tectonic stacking within wedge with different depths of burial. 40Ar/39Ar phengite age of a pervasively sheared footwall micaschist is constrained to 100.6 ± 1.3 Ma and that of a chloritoid-micaschist is constrained to 91.8 ± 1.8 Ma suggesting exhumation during on-going subduction. Coupling and exhumation of the

  20. Magmatic origin of low-T mafic blueschist and greenstone blocks from the Franciscan mélange, San Simeon, California (United States)

    Ukar, Estibalitz; Cloos, Mark


    The Franciscan mélange exposure near San Simeon contains abundant greenstone and minor blueschist blocks that were tectonically boudinaged while encased in the shale-matrix. Tectonic deformation of the blueschists is evident from variable amounts of cataclastic flow along their margins and in pinched tails. Major, trace, and rare earth elemental analyses indicate that blueschist and greenstone blocks in this area of the mélange were derived from sources with MORB-like composition along with some having trace element and REE patterns similar to OIB compositions. Most blocks are low LREE basalts that probably formed in an open ocean ridge setting, but some blocks have high LREE contents similar to off-axis seamounts. Linear trends of incompatible elements for both blueschist and greenstone blocks indicate that both lithologies were probably derived from a similar, variably fractionated, tholeiitic magma. Blueschist blocks with sodic amphibole + lawsonite ± epidote were pervasively recrystallized at 300-350 °C and foliated during ductile deformation that included folding. Their protolith can only be identified as mafic. A few blocks contain very small amounts of metasedimentary materials indicating some were probably seafloor basalts, but some may have been diabase or even gabbro. Where interlayered sediment was present, the mafic protolith was enriched in K, Rb, and Na. Greenstones, on the other hand, contain abundant pseudomorphic evidence of magmatic textures. Alteration to albite, chlorite and pumpellyite at temperatures of 100-200 °C is intense, especially in cataclastic margins and pinched tails. Some of the basaltic greenstones have attached radiolarian chert, and a few have relict diabasic textures. The mafic blueschists and greenstones in the mélange near San Simeon are probably fragments from the uppermost part of the Farallon plate. The blueschists may be mostly mafic slabs uprooted from the subducting crust, underplated to the base of the North

  1. The natural radioactivity in the Serido Pegmatite Province - Rio Grande do Norte State (Brazil): assessment and monitoring of water's source

    International Nuclear Information System (INIS)

    Full text: This abstract show the preliminary considerations of a study accomplished on the radioactive minerals, primary and secondary uranium minerals that occur in the pegmatites of the Serido Region, State of Rio Grande do Norte, Brazil and their influence on the several sources of water provision and on population nuclei of the area from the municipal district of Parelhas and Ecuador. In general, the pegmatite from the area of Ecuador-Parelhas present high environmental radioactivity so much due to the dispersed uranium in the crystalline structure of minerals (columbite-tantalite, albite, microcline, quartz, phosphate minerals, tourmaline, lepidolite and apatite), as primary and secondary uranium minerals (uraninite, pitchblende, gummite, autunite, torbernite, and uranium-bearing opal, etc.). These uranium minerals appear associates to the fracture and voids in the pegmatite and in the tourmaline-bearing granite. These minerals were identified by petrography, X-Rays diffraction, ultraviolet fluorescence analysis, infrared spectroscopy, radioactivity (HPGe gamma spectrometry), thermal behavior and chemical analysis (ICP-MS and AAS, Microprobe). Geochemistry and hydrochemistry preliminary environmental studies on the pegmatites bodies from Serido Region show gamma radiation level which between 150 to 30.000 cps; uranium (U3O8) and thorium (ThO2) content in Columbite-Tantalite (and/or polycrase) varying between 0,3% - 3,0% and 0,1% - 0,5% respectively, and the coating existent in these minerals show uranium contents varying between 20% to 60%. While the soil samples gathered in Ecuador/Parelhas districts show an average activity of 226Ra, 232Th, and 40K of 27.1/39.1; 33.74/48.5; 260.1/234.8 (, dry-weight), respectively, and the corresponding kerma rate (l) in air are 50 and 67 nGyh-1], suggesting that the acid underground waters and others oxidizers attack and dissolve the radioactive minerals from pegmatite, generating solutions rich in U6+ ions (UO22

  2. Geochemical evolution of micas and Sn-, Nb-, Ta- mineralization associated with the rare metal pegmatite in Angwan Doka, central Nigeria (United States)

    Akoh, Juliet U.; Ogunleye, Paul O.; Ibrahim, Aliyu A.


    The pegmatites in Angwan Doka, north central Nigeria are genetically related to the basement granites formed during the Pan-African orogeny, 550-530 Ma ago. They occur as sharply discordant dykes in the granitic and metasedimentary basement rocks. The pegmatite population comprises of mineralogically simple and complexly zoned types that are characterized by LCT (Li, Cs and Ta) geochemical signature. The host granitoids range in composition from hornblende, titanite-bearing to biotite-muscovite granodiorites. Analysis of geochemical data of whole rock and muscovite from the different zones reveals compositional variations and evolution across the pegmatite body from border zone to the lepidolite-quartz core zone. Fractionation of Rb, Cs, Sr, Li, F, B, Be Sn, Zn, Ta, Nb and Mn which increases from host granitoids, through the border zone to the central core, with decrease in Fe, Mg, Ti, Ba content, is typical and marks the magmatic crystallization trend of the pegmatites. Other distinctive attribute of the pegmatites is occurrence of cassiterite believed to have formed as a consequence of greisenization, albitization and late-stage metasomatism, which led to enrichment in Sn (up to 886 ppm) in the intermediate zone. Chemical composition of muscovite from the different zones of the pegmatite reveals high concentration of primary magmatic columbite-Fe (ferrocolumbite and ferrotantalite) in the border zone and tantalite-Mn (manganocolumbite and manganotantalite) in the core zone. Ta predominates (352 ppm) in the most evolved lepidolite (Li- and F-rich) zone while Nb was enriched (up to 714 ppm) in the border zone. These geochemical features are ascribed to undercooling of the melt and crystallization in boundary layers accompanied with increased accumulation of incompatible and fluxing components. With increasing fractionation, Nb/Ta and Fe/Mn ratio decreased and is accompanied with increase in Rb, Cs, Li, F and Be typical of crystallization from magmatic process. The

  3. Comparative study of two pegmatitic field from Minas Gerais, Brazil, using the Rb and Cs contents of micas and feldspars

    International Nuclear Information System (INIS)

    The distribution of alkali elements and F was investigated in minerals of pegmatites and their contact aureole of metasomatism, in two groups of pegmatites from the State of Minas Gerais, southeast Brazil: the Transamazonian-cycle age (1,930 Ma) Volta Grande pegmatites near Sao Joao del Rei and the Brasiliano-cycle age (525 Ma) pegmatites of Itinga. The Volta Grande pegmatites are albite and spodumene bearing and their contact aureole of metasomatism, in the amphibolite host rock, are characterized by the presence of holmquistite and zinnwaldite. The Itinga pegmatites correspond to complex lepidolite and petalite-bearing pegmatites with tourmaline, zinnwaldite and muscovite in their contact aureole developed in quartz-biotite-muscovite-schists. The K-bearing minerals of the Volta Grande pegmatite are exceptionally rich in Rb. Using the experimentally determined partition coefficients between minerals and fluids, the atomic ratio K/Rb of the pegmatitic fluid may be evaluated. This ratio shows homogeneous values, around 4. Similar values are found in the metasomatic aureole, at the contact, which increase as a function of the distance from the contact, due to the crystallization of trioctahedral micas that deplete the fluid in Rb. The K/Rb ratios of the fluid could represent the ratio of the initial pegmatitic magma before differentiation. Rb content in the Itinga pegmatites is much lower and strongly differs from border to core. The presence of K-bearing minerals in the wall rocks contributes for the increasing the K/Rb ratios of the neoformed minerals at the contact zone. It is then more difficult to evaluate the K/Rb ratio of the initial magma. Considering the composition of the minerals at the border of each pegmatite, it varies from 25 at Urubu to 50 at Jose de Linto and Xuxa localities. The Itinga pegmatites are clearly poorer in Rb than the Volta Grande pegmatites. Geochemically, a relationship between the Rb and F contents in the micas is clearly demonstrated

  4. Site investigation SFR. Boremap mapping of core drilled borehole KFR106

    Energy Technology Data Exchange (ETDEWEB)

    Winell, Sofia (Geosigma AB (Sweden))


    This report presents the result from the Boremap mapping of the core drilled borehole KFR106, drilled from an islet ca 220 m southeast of the pier above SFR. The borehole has a length of 300.13 m, and a bearing and inclination of 195.1 deg and -69.9 deg, respectively. The purpose of the location and orientation of the borehole is to investigate the possible occurrence of gently dipping, water-bearing structures in the area. The geological mapping is based on simultaneous study of drill core and borehole image (BIPS). The two lowermost meters of the drill core was mapped in Boremap without access to complementary BIPS-image. The dominating rock type, which occupies 72% of KFR106, is fine- to medium-grained, metagranite granodiorite (rock code 101057), which is foliated with a medium to strong intensity. Pegmatite to pegmatitic granite (rock code 101061) is the second most common rock type and it occupies 16% of the mapped interval. It is also frequent as smaller rock occurrences (< 1 m) in other rock types throughout the borehole. Subordinate rock types are fine- to medium-grained granite (rock code 111058), felsic to intermediate meta volcanic rock (rock code 103076), fine- to medium-grained metagranitoid (rock code 101051) and amphibolite (rock code 102017). Totally 49% of the rock in KFR106 has been mapped as altered, where muscovitization and oxidation is the two most common. Additional shorter intervals of alterations are in decreasing order of abundance quartz dissolution, epidotization, argillization, albitization, chloritization, laumontization and carbonatization. A total number of 2801 fractures are registered in KFR106. Of these are 1059 open, 1742 sealed and 84 partly open. This result in the following fracture frequencies: 6.0 sealed fractures/m, 3.7 open fractures/m and 0.3 partly open fractures/m. In addition there are 5 narrow brecciated zones, and 20 sealed networks with a total length of 18 m. The most frequent fracture fillings in KFR106 are

  5. Mineralogical and geochemical characteristics of the Archaean LCT pegmatite deposit Cattlin Creek, Ravensthorpe, Western Australia (United States)

    Bauer, Matthias; Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard


    The LCT (lithium-cesium-tantalum) pegmatite Cattlin Creek is located about 550 km ESE of Perth, Western Australia. The complex-type, rare-element pegmatite is hosted in metamorphic rocks of the Archaean Ravensthorpe greenstone belt, which constitutes of the southern edge of the Southern Cross Terranes of the Yilgarn Craton. The deposit is currently mined for both lithium and tantalum by Galaxy Resources Limited since 2010. The pegmatitic melt intruded in a weak structural zone of crossing thrust faults and formed several pegmatite sills, of which the surface nearest mineralized pegmatite body is up to 21 m thick. The Cattlin Creek pegmatite is characterized by an extreme fractionation that resulted in the enrichment of rare elements like Li, Cs, Rb, Sn and Ta, as well as the formation of a vertical zonation expressed by distinct mineral assemblages. The border zone comprises a fine-grained mineral assemblage consisting of albite, quartz, muscovite that merges into a medium-grained wall zone and pegmatitic-textured intermediate zones. Those zones are manifested by the occurrence of megacrystic spodumene crystals with grain sizes ranging from a couple of centimeters up to several metres. The core zone represents the most fractionated part of the pegmatite and consists of lepidolite, cleavelandite, and quartz. It also exhibits the highest concentrations of Cs (0.5 wt.%), Li (0.4 wt.%), Rb (3 wt.%), Ta (0.3 wt.%) and F (4 wt.%). This zone was probably formed in the very last crystallization stage of the pegmatite and its minerals replaced earlier crystallized mineral assemblages. Moreover, the core zone hosts subordinate extremely Cs-enriched (up to 13 wt.% Cs2O) mineral species of beryl. The chemical composition of this beryl resamples that of the extreme rare beryl-variety pezzotaite. Other observed subordinate, minor and accessory minerals comprise tourmaline, garnet, cassiterite, apatite, (mangano-) columbite, tantalite, microlite (Bi-bearing), gahnite, fluorite

  6. Origin and evolution of formation water at the Jujo-Tecominoacan oil reservoir, Gulf of Mexico. Part 1: Chemical evolution and water-rock interaction

    Energy Technology Data Exchange (ETDEWEB)

    Birkle, Peter, E-mail: [Instituto de Investigaciones Electricas (IIE), Gerencia de Geotermia, Av. Reforma 113, Cuernavaca, Morelos 62490 (Mexico); Garcia, Bernardo Martinez; Milland Padron, Carlos M. [PEMEX Exploracion y Produccion, Region Sur, Activo Integral Bellota-Jujo, Diseno de Explotacion, Cardenas, Tabasco (Mexico)


    The origin and evolution of formation water from Upper Jurassic to Upper Cretaceous mudstone-packstone-dolomite host rocks at the Jujo-Tecominoacan oil reservoir, located onshore in SE-Mexico at a depth from 5200 to 6200 m.b.s.l., have been investigated, using detailed water geochemistry from 12 producer wells and six closed wells, and related host rock mineralogy. Saline waters of Cl-Na type with total dissolved solids from 10 to 23 g/L are chemically distinct from hypersaline Cl-Ca-Na and Cl-Na-Ca type waters with TDS between 181 and 385 g/L. Bromine/Cl and Br/Na ratios suggest the subaerial evaporation of seawater beyond halite precipitation to explain the extreme hypersaline components, while less saline samples were formed by mixing of high salinity end members with surface-derived, low salinity water components. The dissolution of evaporites from adjacent salt domes has little impact on present formation water composition. Geochemical simulations with Harvie-M{phi}ller-Weare and PHRQPITZ thermodynamic data sets suggest secondary fluid enrichment in Ca, HCO{sub 3} and Sr by water-rock interaction. The volumetric mass balance between Ca enrichment and Mg depletion confirms dolomitization as the major alteration process. Potassium/Cl ratios below evaporation trajectory are attributed to minor precipitation of K feldspar and illitization without evidence for albitization at the Jujo-Tecominoacan reservoir. The abundance of secondary dolomite, illite and pyrite in drilling cores from reservoir host rock reconfirms the observed water-rock exchange processes. Sulfate concentrations are controlled by anhydrite solubility as indicated by positive SI-values, although anhydrite deposition is limited throughout the lithological reservoir column. The chemical variety of produced water at the Jujo-Tecominoacan oil field is related to a sequence of primary and secondary processes, including infiltration of evaporated seawater and original meteoric fluids, the subsequent

  7. Características petrográficas y geoquímicas de rocas basálticas de la Península de Cabo Corrientes (Serranía de Baudó, Colombia Características petrográficas y geoquímicas de rocas basálticas de la Península de Cabo Corrientes (Serranía de Baudó, Colombia

    Directory of Open Access Journals (Sweden)

    Macia S. Carlos


    Full Text Available Petrographic and chemical analyses were perfomed on eight rock samples from the Cabo Corrientes Peninsula. Based on these analses the existence of an oceanic basaltic association which is represented by basalts, spilitic basalts, spilites and komatiitic basalts was stablished; these rocks suffered an intens sodic metasomatism clearly shown in the chemical analyses and in the mineralogical assemblage. It is not clear if these metasomatism has been produced by deep ocean hydrothermal metamorfism as sugested by the presence of albitization and zeolites. It is concluded that the basaltic rocks of the Peninsula on both sides of the Utria fault and specially the ones to the west of it, is tectonically uplifted oceanic crust. A similar origin can be assumed for the rocks of other peninsulas which, like the Cabo Corrientes, are western apophyses of the Baudo Sarrania (i.e. the peninsulas located North and South of Bahias Cupica and Solano. There is a great similarity with therocks of Gorgona Island.Mediante an��lisis petrográficos y químicos detallados de ocho muestras de roca provenientes de la península de Cabo Corrientes se establece la presencia de una asociación basáltica de tipo oceánico, representada por basaltos, basaltos espitilizados, espilitas y basaltos komatiíticos. Estas rocas presentan un intenso metasomatismo sódico, reconocible mineralógicamente y reflejado claramente en los análisis químicos. Sin embargo, no es claro si este metasomatismo es efecto de un metamorfismo hidrotermal de fondo oceánico como lo sugieren la albitización y las ceolitas presentes.Se concluye que: Las rocas basálticas de la península, situadas a ambos lados de la falla de Utria y especialmente al Oeste de esta, corresponden a rocas de fondo oceánico (corteza levantadas tectónicamente. Se asume una situación similar para otras penínsulas que como la de Cabo Corrientes, están a manera de "apéndices" occidentales de la Serranía de Baud

  8. Pressure-temperature evolution of eclogites from the Kechros complex in the Eastern Rhodope (NE Greece) (United States)

    Mposkos, E.; Baziotis, I.; Proyer, A.


    The Rhodope Domain in NE Greece consists of different tectonometamorphic complexes involved in the Alpine collisional history between the Eurasian and African plates. In the Kechros Complex, which is the lowermost tectonic unit in the East Rhodope, a lense of kyanite eclogite occurs within orthogneiss and common eclogites are found between serpentinized peridotite and underlying pelitic gneisses. In kyanite eclogite, the high-pressure (HP) mineral assemblage is Grt + Omp (Jd35-55) + Ky + Ph + Qz + Rt + (indirectly inferred Tlc + Law); a Na-rich tremolite and zoisite formed at or near peak metamorphic conditions. In common eclogites, the HP mineral assemblage is Grt + Omp (Jd29-41) + Rt and, with less certainty, Amp (Gln-rich + Brs + Wnc + Hbl) ± Czo. The inclusions in garnet are glaucophane, actinolite, barroisite, hornblende, omphacite, clinozoisite, titanite, rutile and rarely paragonite and albite. In kyanite eclogite, peak P- T conditions are constrained at 2.2 GPa and 615°C using garnet-omphacite-phengite geothermobarometry and very similar values of 585 ± 32°C and 2.17 ± 0.11 GPa with the average P- T method, by which conditions of formation could also be narrowed down for the common eclogite (619 ± 53°C and 1.69 ± 0.17 GPa) and for a retrogressed eclogite (534 ± 36°C and 0.77 ± 0.11 GPa). Ages for the HP metamorphism in the Kechros Complex are not yet available. A Rb-Sr white mica age of 37 Ma from orthogneiss records a stage of the exhumation. The HP event may be coeval with the Eocene HP metamorphism (49-55 Ma) recorded in the Nestos Shear Zone in Central Rhodope and in the Attic-Cycladic crystalline belt, where it is interpreted as the result of subduction and final closure of the Axios/Vardar ocean and subsequent subduction of the Apulian continental crust (a promontory of the Africa continent) under the southern margin of the European continent in the late Cretaceous and early Tertiary.

  9. Geochemical characteristics of the Shujiadian Cu deposit related intrusion in Tongling: Petrogenesis and implications for the formation of porphyry Cu systems in the Middle-Lower Yangtze River Valley metallogenic belt, eastern China (United States)

    Wang, Shiwei; Zhou, Taofa; Yuan, Feng; Fan, Yu; Cooke, David R.; Zhang, Lejun; Fu, Bin; White, Noel C.


    Porphyry Cu deposits can form in intracontinental or post-collision settings; however, both the genesis of fertile magmas and the mechanism of metal enrichment remain controversial. The Shujiadian porphyry Cu deposit is located in the Tongling area of the Middle-Lower Yangtze River Valley metallogenic belt. It is hosted by the Shujiadian complex, which mainly consists of quartz diorite porphyry (143.7 ± 1.7 Ma) and pyroxene diorite (139.8 ± 1.6 Ma). They both belong to the calc-alkaline series, with enrichment in large-ion lithophile elements (LILE) and light rare earth elements (LREE), depletion in high field-strength elements (HFSE) and heavy rare earth elements (HREE), and slightly negative Eu anomalies. Both quartz diorite porphyry and pyroxene diorite have geochemical affinities with adakite, and their low MgO (1.5-3.7 wt%), and Ni (3.7-6.9 ppm), Cr (2.0-44 ppm), and Th/Ce contents (0.06-0.11) indicate that the intrusive rocks have some characteristics of adakite-like rocks derived from thickened lower crust and melts from metabasaltic rocks and eclogites. Plagioclases from the quartz diorite porphyry are andesine (An value = 31.8-40.5) and from the pyroxene diorite are felsic albite and oligoclase with large-scale zones and variable An value (An value = 8.9-18.3), Fe and Sr contents, which indicate that mixing of mafic and felsic magma may have occurred in the shallow magma chamber. Compared to the barren quartz diorite porphyry, relatively lower SiO2 contents (49.5-55.2 wt.%), higher εNd(t) values (- 7.4 to - 6.9), εHf(t) values (- 11.0 to - 9.1) compositions, Ti-in-zircon temperatures (714-785 °C), and variations of HREE contents of the mineralization-related pyroxene diorite suggest mixing with high-temperature mafic magma. Calculated Ce4 +/Ce3 + values of pyroxene diorite plot between the Ni-NiO buffer (NNO) and magnetite-hematite buffer (MH), and barren quartz diorite porphyry samples plot below the Ni-NiO buffer (NNO). Geochemical features of

  10. U-Pb zircon and biostratigraphic data of high-pressure/low-temperature metamorphic rocks of the Talea Ori: tracking the Paleotethys suture in central Crete, Greece (United States)

    Zulauf, G.; Dörr, W.; Krahl, J.; Lahaye, Y.; Chatzaras, V.; Xypolias, P.


    Inherited deformation microfabrics of detrital quartz grains and U-Pb (Laser ablation (LA)-ICPMS and ID TIMS) ages of detrital zircons separated from the Phyllite-Quartzite Unit s.l. of the Talea Ori, central Crete, suggest strikingly different source rocks. Albite gneiss of the lower Rogdia Beds includes Cambrian and Neoproterozoic rounded zircons with main U-Pb age peaks at 628 and 988 Ma. These and minor Paleoproterozoic and Archean peaks, together with the lack of Variscan-aged and Mesoproterozoic zircons, are similar to the age spectra obtained from the Phyllite-Quartzite Unit s.str. of the Peloponnesus and eastern Crete and from the Taurides. All of these zircons should be derived from the northeastern passive margin of Gondwana (Cimmeria). Metatuffites of the uppermost Rogdia Beds and metasandstone of Bali beach, on the other hand, include euhedral detrital zircons displaying a Variscan U-Pb age spectra at ca. 300 Ma with concordia ages at 291 ± 3, 300 ± 1 Ma (Rogdia) and 286 ± 3, 300 ± 3, 313 ± 2 Ma (Bali). Both types of metasediments and their zircons are similar to those of the pre-Alpine basement and overlying Tyros Beds of eastern Crete, revealing a provenance at the southern active margin of Laurasia. Thus, in central Crete the Paleotethys suture should be situated inside the Rogdia Beds. Magmatic zircons separated from a rhyolite boulder of the lower Achlada Beds yielded a concordant U-Pb zircon age at 242 ± 2 Ma placing a maximum age for the deposition of the (meta)conglomerate from which the boulder was collected. This age is compatible with an Olenekian-early Anisian age of the underlying Vasilikon marble suggested by new findings of the foraminifera Meandrospira aff. pusilla. Both the Achlada Beds and the Vasilikon marble can be attributed to the lower Tyros Beds of eastern Crete. The Alpine deformation led to a pervasive mylonitic foliation, which is affecting most of the studied rocks. This foliation results from D2 top

  11. Tectonic record, magmatic history and hydrothermal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France (United States)

    Ballouard, C.; Boulvais, P.; Poujol, M.; Gapais, D.; Yamato, P.; Tartèse, R.; Cuney, M.


    The Guérande peraluminous leucogranite was emplaced at the end of the Carboniferous in the southern part of the Armorican Massif. At the scale of the intrusion, this granite displays structural heterogeneities with a weak deformation in the southwestern part, whereas the northwestern part is marked by the occurrence of S/C and mylonitic extensional fabrics. Quartz veins and pegmatite dykes orientations as well as lineations directions in the granite and its country rocks demonstrate both E-W and N-S stretching. Therefore, during its emplacement in an extensional tectonic regime, the syntectonic Guérande granite has probably experienced some partitioning of the deformation. The southwestern part is characterized by a muscovite-biotite assemblage, the presence of restites and migmatitic enclaves, and a low abundance of quartz veins compared to pegmatite dykes. In contrast, the northwestern part is characterized by a muscovite-tourmaline assemblage, evidence of albitization and gresenization and a larger amount of quartz veins. The southwestern part is thus interpreted as the feeding zone of the intrusion whereas the northwestern part corresponds to its apical zone. The granite samples display continuous compositional evolutions in the range of 69.8-75.3 wt.% SiO2. High initial 87Sr/86Sr ratios and low εNd(T) values suggest that the peraluminous Guérande granite (A/CNK > 1.1) was formed by partial melting of metasedimentary formations. Magmatic evolution was controlled primarily by fractional crystallization of K-feldspar, biotite and plagioclase (An20). The samples from the apical zone show evidence of secondary muscovitization. They are also characterized by a high content in incompatible elements such as Cs and Sn, as well as low Nb/Ta and K/Rb ratios. The apical zone of the Guérande granite underwent a pervasive hydrothermal alteration during or soon after its emplacement. U-Th-Pb dating on zircon and monazite revealed that the Guérande granite was emplaced

  12. Relative contributions of crust and mantle to the origin of the Bijli Rhyolite in a palaeoproterozoic bimodal volcanic sequence (Dongargarh Group), central India

    Indian Academy of Sciences (India)

    Sarajit Sensarma; S Hoernes; Dhruba Mukhopadhyay


    New mineralogical, bulk chemical and oxygen isotope data on the Palaeoproterozoic Bijli Rhyolite, the basal unit of a bimodal volcanic sequence (Dongargarh Group) in central India, and one of the most voluminous silicic volcanic expressions in the Indian Shield, are presented. The Bijli Rhyolite can be recognized as a poorly sorted pyroclastic deposit, and comprises of phenocrystic K-feldspar + albite ± anorthoclase set in fine-grained micro-fragmental matrix of quartz-feldsparsericite- chlorite-iron-oxide ± calcite. The rocks are largely metaluminous with high SiO2, Na2O+ KO, Fe/Mg, Ga/Al, Zr, Ta, Sn, Y, REE and low CaO, Ba, Sr contents; the composition points to an ‘A-type granite’ melt. The rocks show negative Cs-, Sr-, Eu- and Ti- anomalies with incompatible element concentrations 2–3 times more than the upper continental crust (UCC). LREE is high (La/Yb ∼20) and HREE 20-30 times chondritic. 18 Owhole-rock varies between 4.4 and 7.8‰(mean 5.87 ± 1.26‰). The Bijli melt is neither formed by fractionation of a basaltic magma, nor does it represent a fractionated crustal melt. It is shown that the mantle-derived high temperature basaltic komatiitic melts/high Mg basalts triggered crustal melting, and interacted predominantly with deep crust compositionally similar to the Average Archaean Granulite (AAG), and a shallower crustal component with low CaO and Al2O3 to give rise to the hybrid Bijli melts. Geochemical mass balance suggests that ∼30% partial melting of AAG under anhydrous condition, instead of the upper continental crust (UCC) including the Amgaon granitoid gneiss reported from the area, better matches the trace element concentrations in the rocks. The similar Ta/Th of the rhyolites (0.060) and average granulite (0.065) vs. UCC (0.13) also support a deep crustal protolith. Variable contributions of crust and mantle, and action of hydrothermal fluid are attributed for the spread in 18Owhole-rock values. The fast eruption of high

  13. Caracterización geoquímica y estudio comparativo de plagiogranitos de las Zonas Surportuguesa y Ossa-Morena (SO del Macizo Ibérico, España

    Directory of Open Access Journals (Sweden)

    Bellido, F.


    Full Text Available Plagiogranites and albitic rocks belonging to contrasted magmatic associations of different ages and geodynamic environments outcrop in Ossa-Morena (OMZ and Surportuguese (SPZ Zones. OMZ plagiogranites are related with Cambrian-Ordovician rifting and represent a part of the felsic members of a bimodal magmatic suite and show oceanic plagiogranites affinities. SPZ plagiogranites are related with a Carboniferous volcano-plutonic calc-alkaline suite related with Variscan Orogeny. Both plagiogranites show many similar petrological and geochemical characteristics but display some different immobile elements ratios as La/Nb, Th/Nb, Th/La that are unaltered by metamorphism, magmatic differentiation and alteration processes and prove differences in their sources. SPZ plagiogranites show a more compositional homogeneity than OMZ ones. This is interpreted as a proof of cogenetic origin for SPZ plagiogranites and heterogeneous origin for OMZ plagiogranites, derived from the mix of different sources (astenospheric, lithospheric and crustal.

    En la Zona de Ossa-Morena (ZOM y en la Zona Surportuguesa (ZSP se encuentran plagiogranitos pertenecientes a asociaciones magmáticas y ambientes geodinámicos muy contrastados. Los primeros pertenecen a una asociación bimodal máfica-félsica relacionada con el rifting cámbrico-ordovícico y presentan bastantes afinidades con plagiogranitos oceánicos. Los segundos forman parte de una asociación volcánico-plutónica calcoalcalina carbonífera relacionada con la Orogenia Varisca. Ambos plagio-granitos son semejantes en diversos aspectos petrológicos y geoquímicos pero muestran diferencias en algunas relaciones de elementos inmóviles tales como La/Nb, Th/Nb, Th/La poco sensibles a los procesos de evolución magmática, metamorfismo y alteración y que son reflejo de la composición de las fuentes. Los plagiogranitos de la ZSP presentan una mayor homogeneidad composicional que los de la ZOM. Esto se

  14. Precipitation, throughfall, soil solution and streamwater chemistry in a holm-oak ( Quercus ilex) forest (United States)

    Rodà, Ferran; Avila, Anna; Bonilla, David


    Bulk precipitation, throughfall, soil solution at 20 and 40 cm depths, and stream water were monitored for 2-4 years in a holm-oak forest on schists in the Montseny Mountains (NE Spain). Bulk precipitation was mildly acidic, with Ca 2+ and SO 2-4 as dominant ions. Canopy interactions produced a throughfall less acidic than bulk precipitation and enriched in all other ions. Large amounts of K + were leached from the canopy. Magnesium in net throughfall behaved similarly to K +, and it is concluded that leaching makes a major contribution to Mg 2+ enrichment beneath the canopy. Judging from the moderate increase of Na + and Ca 2+ in throughfall, dry deposition rates for both marine and continental aerosols were low in the studied stand, probably because of its sheltered topographic position within a well-vegetated massif, coupled with moderate tree height and low canopy roughness. Soil solution in the mineral soil was less acidic than throughfall. In common with most temperate forests, SO 2-4 was the dominant mobile anion in the soil water, being largely accompanied by Ca 2+. Potassium and NO -3 were depleted within the soil water with respect to throughfall, probably owing to biological uptake and cation exchange, and incorporation of K + into clay lattices. Subsurface flow dominated the hydrology of the small forested catchment studied. Stream water was basic and rich in bicarbonate. Its chemistry revealed fast rates of weathering of sodium- and magnesium-bearing silicates (mainly albite and chlorite, respectively). Soil respiration and silicate hydrolysis resulted in HCO -3 being the dominant mobile anion in stream water. Calcium to chloride ratios were similar in bulk precipitation and in stream water, indicating that Ca 2+ release from weathering has been counteracted by plant uptake. Nutrient uptake by this aggrading forest strongly influences the solution dynamics of K +, NO 3 and Ca 2+. It is concluded that: (1) this forest does not currently receive acidic

  15. Metamorphic evolution of eclogites at Qinglongshan: modeling in system Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3 (United States)

    Yan, R.; Yang, J.; Zhang, Z.


    Eclogite at Qinglongshan in NE Jiangsu province is one of the research objects which are investigated frequently and products are remarkable in ultra-high pressure (UHP) metamorphic petrology and geochemistry nearly twenty years. Though scholars in China and abroad have made abundant petrological work, there are opposite perspectives to some important petrological questions such as peak assemblage, crystalization time and condition of epidote porphyroblasts which contain coesite, peak assemblage contains talc or not, lawsonite has occurred in the rock or not. This paper choose eclogites in Qinglongshan. Besides traditional petrological work, we applied phase diagram modeling to mineral assemblage and chemical composition, quantitatively investigating the change with temperature and pressure. With the help of petrographic observation the petrological questiones can be solved. Eclogites in Qinglongshan can be divided into three categories: porphyroblastic foliated eclogites, granular massive eclogites and banded eclogites. The peak assemblage in three kinds of eclogites is garnet + omphacite + phengite + kyanite +rutile + coesite. The minerals in the peak assemblage show shape preferred orientation defining the rock foliation in porphyroblastic eclogites. The peak assemblage defined by garnet compositional isopleths in the calculated phase diagram is garnet +omphacite + phengite + kyanite + rutile + coesite + lawsonite + talc in porphyroblastic eclogites, and is garnet + omphacite + phengite + kyanite + rutile +coesite + lawsonite in banded eclogites, both inconsistent with the petrographic observation. This discrepancy probably resulted from the assumption of pure water as the ultrahigh-pressure (UHP) fluid phase. Three stages of metamorphism are established for Qinglongshan eclogites. Prograde inclusions such as amphibole, epidote, plagioclase, chlorite, muscovite, paragonite and albite coexist in the area of 620 and 2.9GPa in banded eclogites. Both petrography and

  16. Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania (United States)

    Bonin, Bernard; Tatu, Mihai


    The Guadalupian (Mid-Permian) Highiș massif (Apuseni Mountains, Romania) displays a bimodal igneous suite of mafic (gabbro, diorite) and A-type felsic (alkali feldspar granite, albite granite, and hybrid granodiorite) rocks. Amphibole is widespread throughout the suite, and yields markedly high chlorine contents. Three groups are identified: Cl-rich potassic hastingsite (2.60-3.40 wt% Cl) within A-type felsic rocks and diorite, mildly Cl-rich pargasite to hornblende (0.80-1.90 wt% Cl) within gabbro, and low F-Cl hornblende within gabbro and hybrid granodiorite. Coexisting biotite is either Cl-rich within diorite, or F-Cl-poor to F-rich within A-type felsic rocks. Chlorine and fluorine are distributed in both mafic phases, according to the F-Fe and Cl-Mg avoidance rules. The low-Ti contents suggest subsolidus compositions. Cl-rich amphibole within diorite and A-type felsic rocks yields a restricted temperature range - from 575 °C down to 400 °C, whereas mildly Cl-rich amphibole within gabbro displays the highest range - from 675 to 360 °C. Temperatures recorded by Cl-rich biotite within diorite range from 590 to 410 °C. Biotite within A-type felsic rocks yields higher temperatures than amphibole: the highest values- from 640 to 540 °C - are recorded in low-F-Cl varieties, whereas the lowest values- from 535 to 500 °C - are displayed by F-rich varieties. All data point to halogen-rich hydrothermal fluids at upper greenschist facies conditions percolating through fractures and shear zones and pervasively permeating the whole Highiș massif, with F precipitating as interstitial fluorite and Cl incorporating into amphibole, during one, or possibly several, hydrothermal episodes that would have occurred during a ~ 150 My-long period of time extending from the Guadalupian (Mid-Permian) to the Albian (Mid-Cretaceous).

  17. The Role of Reactivation and Fluid Pressure Cycling in The Development of Late Zeolite-bearing Faults and Fractures From The Adamello Batholith, Italy (United States)

    Dempsey, E. D.; Holdsworth, R. E.; Di Toro, G.


    Interconnected networks of faults and veins filled with zeolites and other minerals are a common feature of many crystalline rocks, including basaltic volcanics, deformed granitic plutons and regions of high grade continental basement. Typically the fracture fills formed late in the tectonic history and at relatively low temperatures (100-200°C) and in many cases appear to represent a final phase of fluid flow and mineralisation developed during the final stages of exhumation. In the northern part of the Adamello pluton in the Italian Alps, a geometrically complex and kinematically diverse set of zeolite bearing faults and veins is well exposed in the deformed tonalites associated with the Gole Larghe Fault Zone (GLFZ). These features post date all other deformation structures in the pluton, including cooling joints (formed at >550°C), ductile shear zones (550-450°C) and the well-known assemblage of faults, cataclasites and pseudotachylytes (300-250°C) associated with the GLFZ. Three main groups of zeolite-bearing fractures are recognised based on differences in orientation and kinematics of associated shear fracture displacements. These are: i) E-W sinistral reverse thrusts; ii) NNE-SSW sinistral normal faults; and iii) NNW-SSE normal faults. All three groups are associated with the development of white, yellow and red-orange zeolite-rich veins and fault gouge. Individual fault zones are rarely more than a few metres wide and fault offsets are generally small (mostly < 5m). Minor fractures associated with each group display mutually cross-cutting relationships consistent with them all being broadly contemporaneous features. This is confirmed by thin section and XRD analyses which reveal a fairly uniform set of mineral fills (including laumontite ± scolecite ± prehnite ± clinochlore ± stilbite ± stellerite ± quartz ± microcline ± albite). All three fracture groups are hard linked, locally forming spectacular mineralised fracture meshes. These features

  18. Geology and alteration zoning of the Nohwado pyrophyllite deposit, southwest Korea. 1. On the No. 1 deposit of the Nohwa mine

    International Nuclear Information System (INIS)

    quartz and illite with subordinate albite, kaolinite, chlorite, and biotite, occurs in the periphery of the ore body. Although the ore mineral assemblages of the zones are different, their chemical composition is similar. Ore texture and thermodynamic considerations suggest that the diaspore zone may have been secondarily formed by the alteration of the central pyrophyllite zone due to the ascent of steam. The high permeability of the sedimentary host rocks enabled the passage of the hydrothermal fluid, leading to the formation of the large sheet pyrophyllite deposit. Several illite veins are observed along fractures in the ore body. One illite sample from such a vein yielded a K-Ar age of 71.8±3.6 Ma. (author)

  19. Mineralogical controls on surface colonization by sulfur-metabolizing microbial communities (United States)

    Jones, A. A.; Bennett, P.


    When characterizing microbial diversity and the microbial ecosystem of the shallow subsurface the mineral matrix is generally assumed to be homogenous and unreactive. We report here experimental evidence that microorganisms colonize rock surfaces according to the rock's chemistry and the organism's metabolic requirements and tolerances. We investigated this phenomenon using laboratory biofilm reactors with both a pure culture of sulfur-oxidizing Thiothrix unzii and a mixed environmental sulfur-metabolizing community from Lower Kane, Cave, WY, USA. Reactors contained rock and mineral chips (calcite, albite, microcline, quartz, chert, Madison Limestone (ML), Madison Dolostone (MD), and basalt) amended with one of the two inoculants. Biomass of attached microorganisms on each mineral surface was quantified. The 16S rRNA of attached microbial communities were compared using Roche FLX and Titanium 454 next generation pyrosequencing. A primary controlling factor on taxonomy of attached microorganisms in both pure and mixed culture experiments was mineral buffering capacity. In mixed culture experiments acid-buffering carbonates were preferentially colonized by neutrophilic sulfur-oxidizing microorganisms (~18% to ~27% of microorganisms), while acidophilic sulfur-oxidizing microorganisms colonized non-buffering quartz exclusively (~46% of microorganisms). The nutrient content of the rock was a controlling factor on biomass accumulation, with neutrophilic organisms selecting between carbonate surfaces of equivalent buffer capacities according to the availability of phosphate. Dry biomass on ML was 17.8 ± 2.3 mg/cm2 and MD was 20.6 ± 6.8 mg/cm2; while nutrient poor calcite accumulated 2.4 ± 0.3 mg/cm2. Biomass accumulation was minimal on non-buffering nutrient-limited surfaces. These factors are countered by the competitive exclusion of some populations. A pure culture of T. unzii preferentially colonizes carbonates while a very closely related Thiothrix spp is excluded

  20. Origin and evolution of formation water at the Jujo-Tecominoacan oil reservoir, Gulf of Mexico. Part 1: Chemical evolution and water-rock interaction

    International Nuclear Information System (INIS)

    The origin and evolution of formation water from Upper Jurassic to Upper Cretaceous mudstone-packstone-dolomite host rocks at the Jujo-Tecominoacan oil reservoir, located onshore in SE-Mexico at a depth from 5200 to 6200 m.b.s.l., have been investigated, using detailed water geochemistry from 12 producer wells and six closed wells, and related host rock mineralogy. Saline waters of Cl-Na type with total dissolved solids from 10 to 23 g/L are chemically distinct from hypersaline Cl-Ca-Na and Cl-Na-Ca type waters with TDS between 181 and 385 g/L. Bromine/Cl and Br/Na ratios suggest the subaerial evaporation of seawater beyond halite precipitation to explain the extreme hypersaline components, while less saline samples were formed by mixing of high salinity end members with surface-derived, low salinity water components. The dissolution of evaporites from adjacent salt domes has little impact on present formation water composition. Geochemical simulations with Harvie-Mφller-Weare and PHRQPITZ thermodynamic data sets suggest secondary fluid enrichment in Ca, HCO3 and Sr by water-rock interaction. The volumetric mass balance between Ca enrichment and Mg depletion confirms dolomitization as the major alteration process. Potassium/Cl ratios below evaporation trajectory are attributed to minor precipitation of K feldspar and illitization without evidence for albitization at the Jujo-Tecominoacan reservoir. The abundance of secondary dolomite, illite and pyrite in drilling cores from reservoir host rock reconfirms the observed water-rock exchange processes. Sulfate concentrations are controlled by anhydrite solubility as indicated by positive SI-values, although anhydrite deposition is limited throughout the lithological reservoir column. The chemical variety of produced water at the Jujo-Tecominoacan oil field is related to a sequence of primary and secondary processes, including infiltration of evaporated seawater and original meteoric fluids, the subsequent mixing of

  1. Uranium mobility in mine areas: evaluation of the water-rock interaction

    International Nuclear Information System (INIS)

    Full text of publication follows: Toxicity and natural radioactivity of uranium are among the main environmental concerns for exploitation and processing of uranium ore. Weathering processes and potential contamination paths of these areas have to be identified to preserve the water resources. In this work, leaching experiments were carried out in flow-through reactors. Approximately 750 g of crushed rock of selected grain size between 0.35 and 0.80 mm were introduced into a Pyrex column. Distilled and deionized water, saturated with 5% CO2/95% air mixture, was introduced through a glass inlet fitted at the base of the column. Input solution pH was constantly equal to 4.2 while the low flow rate was obtained from a peristaltic pump. The output solution was sampled periodically for about 1 year. Three different rock samples were used: an untreated granite rock with high levels of uranium minerals, a rock with low uranium content and a rock rejected after the lixiviation process for uranium industrial extraction. For untreated rocks pH and silica decrease by 1-2 orders of magnitude while sodium decreases by 2-3 orders of magnitude. This indicates the strong albitite dissolution. Total dissolved uranium has a rather constant level indicating the constant dissolution rate of the uranium mineral assemblage. Thermodynamic modelling of the interacting output solutions indicates that 80% of the dissolved uranium content is under the form of two main carbonate complexes (i.e. UO2(CO3)22- and UO2(CO3)34-), while solutions are saturated on chalcedony, kaolinite and calcium clay minerals. Solutions are under saturated with respect to uraninite and low-temperature albite. In experiments where material was treated with sulphuric acid in the plant, pH is constantly equal to 4 indicating the lack of rock buffering properties. Na, Ca, and SO4 decrease by several orders of magnitude (from some initial mmol/kg) reaching after 1 year of interaction a level 2 orders of magnitude higher

  2. Gamma-spectrometric surveys in differentiated granites. II: the Joaquim Murtinho Granite in the Cunhaporanga Granitic Complex, Parana, SE Brazil; Levantamentos gamaespectrometricos em granitos diferenciados. II: O exemplo do Granito Joaquim Murtinho, Complexo Granitico Cunhaporanga, Parana

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Francisco Jose Fonseca [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia. Lab. de Pesquisas em Geofisica Aplicada; Fruchting, Allan [Votorantim Metais, Sao Paulo, SP (Brazil)], e-mail:; Guimaraes, Gilson Burigo [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Dept. de Geociencias], e-mail:; Alves, Luizemara Soares [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)], e-mail:; Martin, Victor Miguel Oliveira; Ulbrich, Horstpeter Herberto Gustavo Jose [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica], e-mail:, e-mail:


    Detailed mapping at the NW corner of the large Neo proterozoic Cunhaporanga Granitic Complex (CGC), Parana state, SE Brazil, redefined the Joaquim Murtinho Granite (JMG), a late intrusion in CGC with an exposed area of about 10 km{sup 2}, made up mainly by evolved 'alaskites' (alkali-feldspar leuco granites). This unit is in tectonic contact with the Neoproterozoic-Eocambrian volcano-sedimentary Castro Group, to the W, and is intrusive into other less evolved granitic units of the CGC to the E. Petrographically, JMG shows mainly mesoperthite and quartz, with subordinate amounts of altered micas and some accessory phases, mainly zircon. The equi to inequigranular granites are usually deformed with cataclastic textures, are often brecciated, and may have miarolitic structures. Formation of late albite, sericite, carbonate and hematite was caused by deuteric and hydrothermal alteration. A gamma-ray spectrometric survey at 231 stations which measured total counts (TC), Ueq K%, eU ppm and eTh ppm was used to construct several direct and derived maps. Compared to neighboring units the JMG has significant anomalies, especially in the TC, %K, eTh and eU maps, although the differences are less obvious in some derived maps. These evolved granites are enriched in these three elements. Geochemical behavior of K, Th and U is used to analyse the results observed in maps. Enhanced weathering under a subtropical climate with moderate to high average temperatures and heavy rainfall affects mainly feldspars and biotite, and may also destabilize most U and Th-bearing accessory phases. Th is most likely retained in restite minerals in soils, being relatively immobile, while part of U may migrate as uranyl ion in oxidizing media. K is especially affected by feldspar alteration to K-free clays (mainly kaolinite), and may be completely leached. Gamma-ray spectrometric methods are valid tools to study facies in granitic rocks, especially in those that are enriched in K, Th and U

  3. What iron minerals contribute to anaerobic respiration in peats differing in maturity on the Arctic Coastal Plain ? (United States)

    Masue-Slowey, Y.; Wagner, F. E.; Lipson, D.; Raab, T. K.


    Microbial Fe-reduction accounts for 30-60% of ecosystem respiration in drained thaw-lake tundra of the Arctic Coastal Plain. Near Barrow, we collected diffraction, Fe-XANES, Moessbauer spectra (RT and liqHe), and wet-chemical data on the Fe mineralogy of DTLB over an age gradient from 0 - 5500 y BP to delineate the important phases involved in microbial cycling of Fe. Soils were cored frozen in early June of 2010/ 2011, wrapped/ transported to CA by overnight express. Cores varying in age since formation were further sectioned, and transferred to an anaerobic hood for size-fractionation based on settling velocity, and subjected to bulk XRD at SSRL. Fe-XANES of both clay-separates and bulk soil were collected at BL 4-1. Subsamples were packed into anaerobic vials and sent for Moessbauer spectroscopy. Present in bulk soils of all ages by XRD were quartz, albite and vermiculite. Additional smectitic minerals, goethite and Fe-phosphates were evident in some basin classes, esp. Young and Medium. XANES confirmed wet-chem results of a highly-reduced state for Fe in bulk soils, and fits of XAFS indicated goethite as 20% of the reactive Fe-pool among basin-age classes. The most abundant Fe-containing minerals in clay fractions (Old and Young soils) were a ferrosmectite, or hornblende-derived mineral. (Fig.1) MB spectra from various depths of an Old Basin (300-2000 yrs BP) - the DTLB class of greatest areal extent -- revealed largely reduced Fe pools (50-60%), with goethite and a Fhd-like component visible (~23%). LHe spectra indicated the presence of goethite as ~ 20% of the MB-visible pool (Fig 2). Two prominent quadrupole doublets had QS=3.24 mm/s; IS = 1.10 mm/s and QS = 2.84; IS=1.05 mm/s, respectively, and upon oxidation, demonstrated divergent kinetics. We attribute the doublet with lower splitting to the ferrosmectite component visible by XAFS. Although previous sequential extractions of Barrow soil minerals suggested a sizeable component of siderites (indeed geochem

  4. The Parana River Subprovince (Goias State, Central Region Brazil): an application example of the U-Pb and Pb-Pb cassiterite dating methods

    International Nuclear Information System (INIS)

    The Parana River Subprovince is part of the Goias Tin province. It includes a basement composed mainly by orthogneisses and migmatites, named Granite-Gneiss Complex, predominantly Paleoproterozoic in age, overlaid by a metasedimentary sequence of the Ticcunzal Formation, both of which were intruded by pegmatites. These units are overlain by metasedimentary and minor metavolcanic rocks of the Arai Group. Alkalic granites intrude these rocks, previously subdivided into the g1 (∼ 1,770 Ma) and g2 (∼1,580 Ma) families, the later being responsible for the tin mineralization. Rhyolites of the Arai Group are contemporaneous to the alkaline granites. Primary tin mineralization occurs associated with the pegmatites and with late to post-magmatic alterations (greisenization, albitization) in the alkaline granites. Coarse-grained muscovite from Xupe and Riacho dos Cavalos pegmatites yielded K-Ar ages of 2,129 ± 26 Ma and 2,006 ± 24 Ma, respectively. A cassiterite sample from Riacho dos Cavalos Pegmatite was analyzed by U-Pb, confirming the age between 2,023 Ma and 2,277 Ma as the time of tin mineralization. Isochronic Pb-Pb cassiterite dating of the pegmatites yield Archean ages, indicating that the lead incorporated by the cassiterite and its inclusions and aggregate minerals is old, probably derived from the basement. K-Ar dating of muscovite concentrates from the alkaline granites of the Mangabeira Massif yielded ages of 567 ± 14 Ma and 553± 11 Ma, indicating overprinting of the Brasiliano Cycle in the pluton. U-Pb cassiterite dating yield an age of 1,535± Ma, which is concordant with the time of crystallization of the granite and indicates that cassiterite has not behaved as an open system in relation to the Brasiliano deformation. Isochronic Pb-Pb age of the same cassiterite sample (1,425±79 Ma) agrees with the U-Pb age within the analytical error. From these data it is possible to identify two events of tin mineralization in the Subprovince, the oldest of

  5. Prediction of Nanoparticle and Colloid Attachment on Unfavorable Mineral Surfaces Using Representative Discrete Heterogeneity. (United States)

    Trauscht, Jacob; Pazmino, Eddy; Johnson, William P


    Despite several decades of research there currently exists no mechanistic theory to predict colloid attachment in porous media under environmental conditions where colloid-collector repulsion exists (unfavorable conditions for attachment). It has long been inferred that nano- to microscale surface heterogeneity (herein called discrete heterogeneity) drives colloid attachment under unfavorable conditions. Incorporating discrete heterogeneity into colloid-collector interaction calculations in particle trajectory simulations predicts colloid attachment under unfavorable conditions. As yet, discrete heterogeneity cannot be independently measured by spectroscopic or other approaches in ways directly relevant to colloid-surface interaction. This, combined with the fact that a given discrete heterogeneity representation will interact differently with differently sized colloids as well as different ionic strengths for a given sized colloid, suggests a strategy to back out representative discrete heterogeneity by a comparison of simulations to experiments performed across a range of colloid size, solution IS, and fluid velocity. This has recently been performed for interaction of carboxylate-modified polystyrene latex (CML) microsphere attachment to soda lime glass at pH 6.7 with NaCl electrolyte. However, extension to other surfaces, pH values, and electrolytes is needed. For this reason, the attachment of CML (0.25, 1.1, and 2.0 μm diameters) from aqueous suspension onto a variety of unfavorable mineral surfaces (soda lime glass, muscovite, and albite) was examined for pH values of 6.7 and 8.0), fluid velocities (1.71 × 10(-3) and 5.94 × 10(-3) m s(-1)), IS (6.0 and 20 mM), and electrolytes (NaCl, CaSO4, and multivalent mixtures). The resulting representative heterogeneities (heterodomain size and surface coverage, where heterodomain refers to nano- to microscale attractive domains) yielded colloid attachment predictions that were compared to predictions from existing

  6. A hot spring in granite of the Western Tianshan, China

    International Nuclear Information System (INIS)

    solid inclusions in the granite, which have been introduced to quartz by ductile shearing and faulting related to ongoing orogenesis. The hot water remobilizes the salt that is continuously liberated by the tectonic deformation. Water-granite interaction contributes a thenardite-component (Na2SO4) to the major element composition by albite dissolution in H2SO4. The water-rock interaction along faults and fractures transforms and alters Muza granite to a low-temperature epigranite

  7. Mesozoic metamorphism and its tectonic implication along the Solonker suture zone in central Inner Mongolia, China (United States)

    Zhang, Jinrui; Wei, Chunjing; Chu, Hang; Chen, Yaping


    The Xing'an-Inner Mongolia Orogenic Belt (XIMOB) exposed in the eastern section of the Central Asian Orogenic Belt (CAOB) is generally thought to have resulted from closure of the Paleo-Asian Ocean. However, disputations still exist on the age and detailed tectonic processes involved in its final amalgamation. The Solonker suture zone in the central Inner Mongolia, once recognized as the major paleo-plate boundary recording the terminal collision of the XIMOB, is characterized by extensive regional low-temperature metamorphism of greenschist to epidote-amphibolite facies with local presence of blueschists, which lacks systematic study. Four metabasite and garnet-mica schist samples were studied for determination of metamorphic P-T evolution using pseudosection and conventional thermobarometry. The two metabasite samples from Wulangou and Daqing Pasture contain actinolite, albite, epidote, chlorite and hornblende (in Daqing Pasture) and are estimated to have peak P-T conditions of 5.2-5.9 kbar/415-450 °C in Wulangou and 7.0-7.9 kbar/470-475 °C in Daqing Pasture. Two garnet-mica schist samples from Shuangjing (or Shuangjing schist) contain garnet porphyroblasts, muscovite, quartz, plagioclase, chlorite with or without potassium feldspar, biotite, and calcite, and are modeled to record prograde P-T vectors respectively of 3.0 kbar/482 °C-3.3 kbar/495 °C and 4.2 kbar/478 °C-4.8 kbar/483 °C, followed by near-isothermal decompression. The zircon U-Pb dating analyses suggest that the metamorphism probably occurred soon afterwards in the Early Mesozoic. The peak P-T conditions for the metabasite and garnet-mica schist samples yield thermal gradients respectively of 18-22 °C/km and 26-33 °C/km, being intermediate and low P/T series, and the metamorphic evolution in these rocks characteristic of clockwise P-T paths may correspond to tectonic thickening and thinning processes. The extensive low-temperature metamorphism of intermediate to low P/T types along the

  8. Secondary electron emission from lunar soil by solar wind type ion impact: Laboratory measurements (United States)

    Dukes, Catherine; Bu, Caixia; Baragiola, Raul A.


    Introduction: The lunar surface potential is determined by time-varying fluxes of electrons and ions from the solar wind, photoelectrons ejected by UV photons, cosmic rays, and micrometeorite impacts. Solar wind ions have a dual role in the charging process, adding positive charge to the lunar regolith upon impact and ejecting negative secondary electrons (SE). Electron emission occurs when the energy from the impacting ion is transferred to the solid, ionizing and damaging the material; electrons with kinetic energy greater than the ionization potential (band gap + electron affinity) are ejected from the solid[1].Experiment: We investigate the energy distribution of secondary electrons ejected from Apollo soils of varying maturity and lunar analogs by 4 keV He+. Soils are placed into a shallow Al cup and compressed. In-situ low-energy oxygen plasma is used to clean atmospheric contaminants from the soil before analysis[2]. X-ray photoelectron spectroscopy ascertains that the sample surface is clean. Experiments are conducted in a PHI 560 system (<10-9 Torr), equipped with a double-pass, cylindrical-mirror electron energy analyzer (CMA) and μ-metal shield. The spectrometer is used to measure SE distributions, as well as for in situ surface characterization. A small negative bias (~5V) with respect to the grounded entrance grid of the CMA may be placed on the sample holder in order to expose the low energy cutoff.To measure SE energy distributions, primary ions rastered over a ~6 x 6 mm2 area are incident on the sample at ~40° relative to the surface normal, while SE emitted with an angle of 42.3°± 3.5° in a cone are analyzed.Results: The energy distribution of SE ejected from 4 keV He ion irradiation of albite with no bias applied shows positive charging of the surface. The general shape and distribution peak (~4 eV) are consistent with spectra for low energy ions on insulating material[1].Acknowledgements: We thank the NASA LASER program for support

  9. Copper Metallogenic Conditions and Prospecting Direction of Zoumadi Ore Block of Wuding County%武定县走马地矿段铜矿成矿条件及找矿方向

    Institute of Scientific and Technical Information of China (English)

    宋禹霖; 范柱国; 宋尚鑫


    武定地区区域矿产资源极丰富,矿区经过40多年的勘查,共发现各类矿点百余个,综合研究表明,武定县平地耀左所铜矿床类型以“东川式”铜矿最重要,分布在金钟罩、鸡冠山、油基田、周家箐、走马地、黄龙河、牛德庄等地;次为稀矿山式,主要在蒿枝地,走马地等地。“东川式”铜矿:落雪组底部过渡层,“稀矿山式”铁铜矿:因民组下部,同生断裂旁侧,古火山机构中的火山洼地,火山旋回的中上部,富含Na2O的细碧角斑岩系,硅质岩、萤石岩、钠长岩等喷流岩以及黑云母、绿泥石火山凝灰岩的分布区。%Regional mineral resources of Wuding region are extremely rich, after 40 years of mining exploration, all kinds of hundred mines were found. Comprehensive studies show that, "Dongchuan style" copper mine is the most important mine in Wuding Pingdi-Zuosuo copper deposits, which located in Jinzhongzhao, Jiguanshan, oil-based fields, Zhoujiaqing, Zoumadi, Huanglong River, Niudezhuang etc.;Dilute mine type is the second important, mainly in Artemisia sticks, Zoumadi and other places. "Dongchuan style" copper mine: bottom snow group buffer layer; "dilute mine type" iron-copper: due to the lower part of the public group, contemporaneous faults flanking the ancient volcano volcanic depressions institutions, volcanic cycles in the upper rich Na2O of spilite porphyry system, chert, fluorite rock, rock and other jet albite rock and biotite, chlorite volcanic tuff distribution.

  10. Physical volcanology, geochemistry and basin evolution of the Ediacaran volcano-sedimentary succession in the Bas Draâ inlier (Ouarzazate Supergroup, Western Anti-Atlas, Morocco) (United States)

    Karaoui, Brahim; Breitkreuz, Christoph; Mahmoudi, Abdelkader; Youbi, Nasrrddine


    New geologic mapping, lithofacies and granulometric analysis, and geochemistry from the volcano-sedimentary successions of the central part of the Bas Draâ inlier, Western Anti-Atlas, constrain the Ediacaran Ouarzazate Supergroup evolution during the post-collisional stage of the Pan-African orogeny. Volcanosedimentary facies analysis is the key aspect of the present contribution. We distinguished sixteen terrestrial volcanosedimentary lithofacies in the Bas Draâ succession (BDS), which reaches a total thickness of 2000 m. BDS evolution can be grouped into four units (Aouinet Aït Oussa I to IV, AO I-AO IV). The earliest volcanic activity produced rhyolitic ignimbrite sheets (AO I), which had been considered as lava flows by previous workers, and which were presumably related to caldera system(s). During AO II, a complex of high-silica andesitic and rhyolitic lavas formed, punctuated by the explosive eruption of a high-temperature silica-rich magma leading to the formation of parataxitic ignimbrite. AO III consists of basalt and andesite lava fields and small explosive, in parts phreatomagmatic volcanic vents. It is dissected by fluvial systems depositing external non-volcanic and local volcanic debris. BDS evolution terminated with the formation of a large SiO2-rich lava dome complex (AO IV), accompanied by small basalt effusive event. Volcanosedimentary facies analysis infers that the BDS evolved in a continental extensional setting developing in a low topography under humid paleoclimatic conditions. Alteration textures are dominated by a piemontite-calcite-albite-quartz (+ iron oxides) assemblage. Chemical analysis of BDS volcanic and subvolcanic rocks belongs to high-k calc-alkaline and alkali-calcic to alkaline magmatic trend typical for a post-collision setting. Trace elements spidergrams show a pattern typical for subduction-related suites of orogenic belts. REE patterns show moderate enrichment in LREE relative to flat HREE, with strong negative Eu

  11. Diagenesis and reservoir quality evolution of palaeocene deep-water, marine sandstones, the Shetland-Faroes Basin, British continental shelf

    Energy Technology Data Exchange (ETDEWEB)

    Mansurbeg, H. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Morad, S. [Department of Earth Sciences, Uppsala University, Villavaegen 16, SE 752 36 Uppsala (Sweden); Department of Petroleum Geosciences, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Salem, A. [Faculty of Education at Kafr El-Sheikh, Tanta University, Kafr El-Sheikh (Egypt); Marfil, R.; Caja, M.A. [Departmento Petrologia y Geoquimica, Facultad de Geologia, UCM, 28040 Madrid (Spain); El-ghali, M.A.K. (Geology Department, Al-Fateh University, P.O. Box 13696, Libya); Nystuen, J.P. [Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, NO-0316 Oslo (Norway); Amorosi, A. [Department of Earth Sciences, University of Bologna, Via Zamboni 67, 40127 Bologna (Italy); Garcia, D. [Centre SPIN, Department GENERIC, Ecole Nationale Superieure des Mines de Saint Etienne 158, Cours Fauriel 42023, Saint-Etienne (France); La Iglesia, A. [Instituto de Geologia Economica (CSIC-UCM), Facultad de Geologia, UCM, 28040 Madrid (Spain)


    eogenetic kaolinite, smectite and mesogenetic illite and chlorite. Kaolinite has been subjected to mesogenetic replacement by dickite. The K-feldspar and plagioclase grains have been albitized. Dissolution of calcite cement and of framework grain (feldspar, volcanic fragments and mud intraclasts) has resulted in a considerable enhancement of reservoir quality. (author)

  12. Quality Aspects of a Marine Aggregate Deposit off the SE Euboea Island, Greece, for its Exploitation - Preliminary Results (United States)

    Anastasatou, Marianthi; Kapsimalis, Vasilios; Stamatakis, Michael; Tsoutsia, Antonia; Poulos, Serafeim; Rousakis, Grigoris; Karditsa, Aikaterini; Petrakis, Stelios; Aspiotis, Konstantinos; Papavlasopoulou, Nafsika; Stamatakis, Giorgos


    % according to a semi-quantitative estimation) with minor trace minerals, such as albite and clay minerals. On the basis of the qualitative characteristics, sediments on the inner continental shelf of SE Euboea can be classified as siliceous and being considered appropriate for potential exploitation, that is related also to its quantitatively characteristics. The relatively shallow depths (Programme ''Education and lifelong learning, 2007-2013'' of the Ministry of Education and Religious Affairs, Culture and Sports.

  13. Evolution of fluid-rock interaction in the Reykjanes geothermal system, Iceland: Evidence from Iceland Deep Drilling Project core RN-17B (United States)

    Fowler, Andrew P. G.; Zierenberg, Robert A.; Schiffman, Peter; Marks, Naomi; Friðleifsson, Guðmundur Ómar


    We describe the lithology and present spatially resolved geochemical analyses of samples from the hydrothermally altered Iceland Deep Drilling Project (IDDP) drill core RN-17B. The 9.3 m long RN-17B core was collected from the seawater-dominated Reykjanes geothermal system, located on the Reykjanes Peninsula, Iceland. The nature of fluids and the location of the Reykjanes geothermal system make it a useful analog for seafloor hydrothermal processes, although there are important differences. The recovery of drill core from the Reykjanes geothermal system, as opposed to drill cuttings, has provided the opportunity to investigate evolving geothermal conditions by utilizing in-situ geochemical techniques in the context of observed paragenetic and spatial relationships of alteration minerals. The RN-17B core was returned from a vertical depth of ~ 2560 m and an in-situ temperature of ~ 345 °C. The primary lithologies are basaltic in composition and include hyaloclastite breccia, fine-grained volcanic sandstone, lithic breccia, and crystalline basalt. Primary igneous phases have been entirely pseudomorphed by calcic plagioclase + magnesium hornblende + chlorite + titanite + albitized plagioclase + vein epidote and sulfides. Despite the extensive hydrothermal metasomatism, original textures including hyaloclastite glass shards, lithic clasts, chilled margins, and shell-fragment molds are superbly preserved. Multi-collector LA-ICP-MS strontium isotope ratio (87Sr/86Sr) measurements of vein epidote from the core are consistent with seawater as the dominant recharge fluid. Epidote-hosted fluid inclusion homogenization temperature and freezing point depression measurements suggest that the RN-17B core records cooling through the two-phase boundary for seawater over time to current in-situ measured temperatures. Electron microprobe analyses of hydrothermal hornblende and hydrothermal plagioclase confirm that while alteration is of amphibolite-grade, it is in disequilibrium

  14. Influence of deformation mechanisms and metamorphic reactions during strain localization in the continental crust under lower amphibolite facies conditions: an example from the Gotthard massif (United States)

    Oliot, E.; Goncalves, P.; Schulmann, K.; Marquer, D.


    increasing strain, modal abundance of K-feldspars decreases from 28% to 16%, whereas both micas increase from 5% to 21%. Similarly, albite evolves from 25% to 8%, whereas oligoclase evolves from 5% to 25%. Deformation mechanisms responsible for these microstructures have been studied by combining a quantitative textural analysis (CSD, SPO, grain boundary frequency and orientation - PolyLX MatlabTM toolbox; Lexa, 2005) and a crystallographic study by EBSD. Deformation mechanisms of quartz, K-feldspar and plagioclase are a combination of SGR and GBM in the orthogneiss and in the mylonite, whereas GBS is active in the ultramylonite. CPO characteristic features are still a matter of debate. Because mass transfers occurred in this shear zone (gains of MnO, CaO, Fe2O3, P2O5 and TiO2) without volume change, thermodynamic modeling of phase relations in such open system must consider the variations of effective bulk rock composition during deformation. In this example, phase relations have been mapped using Perple_X'07 (Connolly, 2005) as a function of P, T, M(H2O) and X(bulk composition), in order to highlight the influence of subtle mass transfers on the syn-deformation stability of mineral assemblages at 500°C and 7.2 kbars. A particular attention has been paid to the role of water content on the stable assemblage and on compositions of metamorphic phyllosilicates. Water under-saturated conditions induce the stability of aluminosilicates, and should increase the Xmg in biotite and decrease the amount of tschermak substitution in phengite. P- and T-M(H20) diagram suggest that the Alpine ductile shear zones occurred under water-saturated conditions. This study reveals that strain localization is related to the metamorphic reactions (breakdowns of K-feldspars to phengites and magmatic plagioclase to albite and oligoclase), which induce a strong decrease in grain size reduction and a switch in deformation mechanism from SGR and GBM to GBS in the ultramylonite. The good agreement

  15. Why is Dawsonite Absent in CO2 Charged Reservoirs? Pourquoi la dawsonite est-elle absente des réservoirs chargés en CO2 ?

    Directory of Open Access Journals (Sweden)

    Hellevang H.


    Full Text Available Growth of the sodiumaluminium-hydroxy carbonate dawsonite (NaAl(OH2CO3 after charging saline aquifers with CO2 has been assumed in a plethora of numerical simulations at different mineralogies, aqueous solutions, pressures and temperatures. It appears however that dawsonite is less abundant than expected in natural CO2 storage analogues if we take into account the thermodynamic stability alone. We have mapped the thermodynamic stability of dawsonite relative to mineral phases like albite, kaolinite and analcime from 37° to 200°C and performed closed-system batch kinetic simulations using a new kinetic expression including a nucleation term based on classical nucleation theory, and a growth term that was based on BCF growth theory. Using this rate equation, we have performed a sensitivity study on dawsonite growth on mineralogy, temperature, CO2 pressure, nucleation rate and its dependencies on temperature and affinity, and on the dawsonite precipitation rate coefficient. Simulations with dawsonite growth disabled showed that the maximum oversaturation reached for dawsonite for seawater-like solutions never exceeded 3-4 times oversaturation. The positive effect on dawsonite growth of increasing the CO2 pressure was mostly neutralized by higher acidity. Decreasing the precipitation rate coefficient by 5 orders of magnitude had a limited effect on the onset of significant growth, but the amount of dawsonite formed at the end of the 1 000 years simulated time was only 37% below the high-rate case. Reducing the nucleation rates had similar effects leading to postponed dawsonite growth. Finally, based on thermodynamic considerations and numerical simulations, we suggest that the potential of dawsonite growth is limited to a medium-temperature window framed by a high thermodynamic stability relative to competing mineral phases at low temperatures, but with rapidly diminishing nucleation and growth rates at lower temperatures constrained by energy

  16. 内蒙古赵井沟大型铌钽矿床地质特征及成因%Geological features and origin of Zhaojinggou Nb-Ta deposit in Wuchuan County, Inner Mongolia

    Institute of Scientific and Technical Information of China (English)

    聂凤军; 王丰翔; 赵宇安; 孙艳; 柴华


    Located in the central-eastern section of the Yinshan Precambrian uplift in the western segment of the Inner Mongolian Axis of the Northern China craton,the newly discovered Zhaojinggou deposit is one of the largest Nb-Ta deposits in northern China.During the Hercynian orogeny,intense tectonic and igneous activities resultedin the large-scale granitoid magmatism in Zhaojinggou and its neighboring areas.The Zhaojinggou alkaline feldspar granitoid (AFG) intrusive complex was emplaced in the meta-sedimentary sequence of the Middle Carboniferous Shuanmazhuang Group,controlled by NE-,NNE-and NW-trending fault zones.The AGI complex has an outcrop area of 0.05 km2,and consists mainly of alkaline feldspar granite (AFG),AFG pegmatite and AFG aplite that have no difference in mineral assemblage.Rock-forming minerals are mainly quartz,amazonite and albite associated with minor biotite,muscovite and sericite.Accessory minerals are rutile,apatite,zircon,topaz,fluorite,allanite and columbite.The AFG intrusive complex is petrochemically characterized by relatively high Al2O3,SiO2,Na2O,Rb,Nb,Ta and Hf,obviously low CaO,Fe2O3,FeO,MgO,Sr,Ba,Zr and REE,belonging to silicon-high,sodium-rich rock of calc-alkaline series.Nb-and Tamineralization occurs entirely within the Zhaojinggou AFG intrusive complex as veinlets and disseminated blocks.Nb-and Ta-ores consist of parisite,columbotantalite,cassiterotantalite (ixiolite),monazite,bismuthinite,chevkinite,laplandite,rutile,topaz,apatite,amazonite,Li-Rb-bearing biotite,Li-Rb-bearing muscovite,epidote,fluorspar,hornblende,zircon,quarzt,barite,albite and calcite.As the most important economic Nb-and Taminerals,columbotantalite,cassiterotantalite (ixiolite) and parisite occur in the forms of impregnation,very fine grains,thin films,aggregated fine grains in the AFG intrusive complex.LA-ICP-MS U-Pb isotopic dating of the zircon separates from the AFG intrusive complex has given the ages varying from (277.14 ± 0.82) Ma to (276.6 ± 2.1) Ma

  17. 铌钽矿研究进展和攀西地区铌钽矿成因初探%Advances in study of Nb-Ta ore deposits in Panxi area and tentative discussion on genesis of these ore deposits

    Institute of Scientific and Technical Information of China (English)

    王汾连; 赵太平; 陈伟


    Niobium and tantalum ore deposits are mainly hosted in pegmatites, Li-F-rich granites, alkali intrusive rocks, carbonatites and alluvial sandstones. The first two types of ore deposits are dominated by tantalum and the other ore deposits by niobium. Niobium and tantalum are present mainly as independent minerals (such as columbite, tantalite, microlite and pyrochlore) disseminated in the host rocks and occasionally isomorphously in other minerals (such as mica, titanite, aegirine and ilmenite). Two main enrichment mechanisms for Nb-Ta ores are suggested: (1) fractional crystallization from granitic melt rich in F, Na and rare metals; (2) hydrother-mal metasomatism of granite after magmatism. The Nb-Ta ore deposits in Panxi area (Panzhihua-Xichang) are mostly distributed along the fracture belt, and the ore bodies are hosted in alkali pegmatite veins and alkali granites, closely related to adjacent syenites and granites widely spread in this area. The main ore minerals are pyrochlore and fergusenite. Studies show that the metallogenesis might have been an event related to Permian Emeishan mantle plume. The felsic rocks (syenites and granites), probably the parent rocks of the ore deposits, were products of Permian Emeishan mantle plume similar to widespread Emeishan basalts and gabbros. The alkali pegmatite veins (e. g., Luku and Baicao) were formed by fractional crystallization from alkali magma and ore-bearing alkali granites by differentiation of granitic magma. Besides, the hydrothermal metasomatism might have contributed to the concentration of niobium and tantalum, as evidenced by the fact that ore minerals are always present where albitization occurs. It is therefore considered that the formation of Nb-Ta ore deposits in Panxi area resulted from both fractional crystallization and hydrothermal metasomatism.Niobium and tantalum ore deposits are mainly hosted in pegmatites, Li-F-rich granites, alkali intrusive rocks, carbonatites and alluvial sandstones. The

  18. Interdisciplinary investigation of Boda clay-stone formation - preliminary results

    International Nuclear Information System (INIS)

    , Mecsekerc Plc, by the University of Kaposvar and colleagues of many companies. The first step of the project was to define on the basis of available information, the range of geophysical and petrophysical parameters for investigation, the analyses to be done and their temporal sequence. This was followed by the choice of core to be analyzed, being the primary requirement that the sample should be as undisturbed as possible (not too disturbed, comprehensive, stored adequately). The 598.04-608.58 m long section of Ib-4 borehole in the Gorica block, and the 480.9-481.81 m long section of the covering sandstone was chosen, to provide the completeness of investigation, and made available for the company by PURAM. The rock formation itself explored in the borehole cannot be considered as a typical BCF formation, because due to evolutionary deviations, there appear differences in cementation and compaction on the level of mineralogy, but it was matching the other sampling criteria.The chosen rock sequence is albite nest with clayey shale and clay-stone with shale, together with dolomite and clayey dolomite intercalations. After general geological characterization, dry and wet CT investigations were made on selected cores and the features of obtained data and available well-logs were compared with the results of core scanning on the whole core material and of the LIPS test, as well as with the results of mineralogical analyses. The aim of investigations made on the whole core is to appoint adequate ranges for forming rock samples on the basis of the available multi-levelled and diversified analysis results that would further the effectiveness of the assessment of later analyses. It is important that by considering the sedimentological, mineralogical, geochemical, geophysical reservoir character, sampling should be representative, according to the following aspects of investigation: - separation according to litho-facies, the basis of which is cyclicness, described on the basis of

  19. Climate dependence of feldspar weathering in shale soils along a latitudinal gradient (United States)

    Dere, Ashlee L.; White, Timothy S.; April, Richard H.; Reynolds, Brian; Miller, Thomas E.; Knapp, Elizabeth P.; McKay, Larry D.; Brantley, Susan L.


    weathering in the north. A calculated apparent Arrhenius-type temperature dependence across the transect (excluding NY) for the dissolution of feldspar (Na depletion) is 99 ± 15 kJ mol-1, a value similar to field-measured values of the activation energy (14-109 kJ mol-1) or laboratory-measured values of the enthalpy of the albite reaction (79.8 kJ mol-1). Observations from this transect document that weathering losses of Na from Silurian shale can be understood with models of regolith formation based on chemical and physical factors such that weathering progresses from kinetically limited sites (Wales to AL) to the transport-limited site in Puerto Rico. Significant advances in our ability to predict regolith formation will be made as we apply more quantitative models to such transect studies on shales and other rocks types.

  20. Solid oxide electrolysis cells - Performance and durability

    Energy Technology Data Exchange (ETDEWEB)

    Hauch, A.


    In this work H2 electrode supported solid oxide cells (SOC) produced at Risoe National Laboratory, DTU, have been used for steam electrolysis. Electrolysis tests have been performed at temperatures from 650AeC to 950AeC, p(H2O)/p(H2) from 0.99/0.01 to 0.30/0.70 and current densities from -0.25 A/cm2 to -2 A/cm2. The solid oxide electrolysis cells (SOEC) have been characterised by iV curves and electrochemical impedance spectroscopy (EIS) at start and end of tests and by EIS under current load during electrolysis testing. The tested SOCs have shown the best initial electrolysis performance reported in literature to date. Area specific resistances of 0.26 Oecm2 at 850AeC and 0.17 Oecm2 at 950AeC were obtained from electrolysis iV curves. The general trend for the SOEC tests was: 1) a short-term passivation in first few hundred hours, 2) then an activation and 3) a subsequent and underlying long-term degradation. The transient phenomenon (passivation/activation) was shown to be a set-up dependent artefact caused by the albite glass sealing with a p(Si(OH)4) of 1.10-7 atm, leading to silica contamination of the triple-phase boundaries (TPBs) of the electrode. The long-term degradation for the SOECs was more pronounced than for fuel cell testing of similar cells. Long-term degradation of 2%/1000 h was obtained at 850AeC, p(H2O)/p(H2) = 0.5/0.5 and -0.5 A/cm2, whereas the degradation rate increased to 6%/1000h at 950AeC, p(H2O)/p(H2) = 0.9/0.1 and -1.0 A/cm2. Both the short-term passivation and the long-term degradation appear mainly to be related to processes in the H2 electrode. Scanning electron microscopy micrographs show that only limited changes occur in the Ni particle size distribution and these are not the main degradation mechanism for the SOECs. Micro and nano analysis using energy dispersive spectroscopy in combination with transmission electron microscopy (TEM) and scanning TEM reveals that glassy phase impurities have accumulated at the TPBs as a result of

  1. Multistage metasomatism in ultrahigh-pressure mafic rocks from the North Dabie Complex (China) (United States)

    Malaspina, Nadia; Hermann, Jörg; Scambelluri, Marco; Compagnoni, Roberto


    Release of metamorphic fluids within the slab and/or from the slab to the mantle wedge in subduction environments can produce important metasomatic effects. Ultrahigh-pressure (UHP) metasomatised rocks represent ideal materials to study the element exchange at pressures corresponding to sub-arc depths in subduction zones. We present a petrologic and geochemical study of eclogites (s.l.) from the Dabie Mountains (China). The investigated samples were collected in the North Dabie Complex, where eclogite-facies rocks are significantly overprinted by granulite-facies metamorphism and partial melting. The studied eclogites are included in meta-lherzolitic bodies, which are in turn hosted by leucocratic gneisses. The textural relations among the various rock-forming minerals enabled us to identify several re-crystallisation stages. The peak (UHP) paragenesis consists of garnet, clinopyroxene and rutile. UHP garnet and clinopyroxene display oriented inclusions of polycrystalline rods of rutile + ilmenite and of albite, K-Ba-feldspar and quartz, respectively. Garnet and clinopyroxene are both rimmed by an inclusion free zone that formed after the peak, still at high-pressure conditions. Such optical zoning does not correspond to a difference in major element concentrations between garnet core and rim. This observation provides evidence that the major element composition of garnet was reset during exhumation, thus preventing thermobarometric determination of peak metamorphic conditions. Further decompression is documented by the formation of limited ilmenite + amphibole and granulite-facies coronas consisting of clinopyroxene, orthopyroxene, plagioclase and amphibole around garnet. In order to investigate the stability of observed mineral parageneses, a series of reconnaissance piston cylinder synthesis experiments were carried out in an identical bulk composition. The experimental study indicates that the peak metamorphic paragenesis is stable at P˜3.5 GPa and T ≥ 750

  2. Hydrothermal modification of host rock geochemistry within Mo-Cu porphyry deposits in the Galway Granite, western Ireland (United States)

    Tolometti, Gavin; McCarthy, Will


    Hydrothermal alteration of host rock is a process inherent to the formation of porphyry deposits and the required geochemical modification of these rocks is regularly used to indicate proximity to an economic target. The study involves examining the changes in major, minor and trace elements to understand how the quartz vein structures have influenced the chemistry within the Murvey Granite that forms part of the 380-425Ma Galway Granite Complex in western Ireland. Molybdenite mineralisation within the Galway Granite Complex occurred in close association with protracted magmatism at 423Ma, 410Ma, 407Ma, 397Ma and 383Ma and this continues to be of interest to active exploration. The aim of the project is to characterize hydrothermal alteration associated with Mo-Cu mineralisation and identify geochemical indicators that can guide future exploration work. The Murvey Granite intrudes metagabbros and gneiss that form part of the Connemara Metamorphic complex. The intrusion is composed of albite-rich pink granite, garnetiferous granite and phenocrytic orthoclase granite. Minor doleritic dykes post-date the Murvey Granite, found commonly along its margins. Field mapping shows that the granite is truncated to the east by a regional NW-SE fault and that several small subparallel structures host Mo-Cu bearing quartz veins. Petrographic observations show heavily sericitized feldspars and plagioclase and biotite which have undergone kaolinization and chloritisation. Chalcopyrite minerals are fine grained, heavily fractured found crystallized along the margins of the feldspars and 2mm pyrite crystals. Molybdenite are also seen along the margins of the feldspars, crystallized whilst the Murvey Granite cooled. Field and petrographic observations indicate that mineralisation is structurally controlled by NW-SE faults from the selected mineralization zones and conjugate NE-SW cross cutting the Murvey Granite. Both fault orientations exhibit quartz and disseminated molybdenite

  3. Mineralogy and geochemistry of the Late Neoproterozoic rare metal granitoids of Gabal El-Ineigi pluton, Northern Arabian-Nubian Shield, Egypt (United States)

    Sami, Mabrouk; Ntaflos, Theodoros; Mohamed, Haroun A.; Farahat, Esam S.; Ahmed, Awaad F.


    Gabal El-Ineigi granitoid pluton is situated in the Central Eastern Desert of Egypt and is considered as one of the good examples of the fluorite bearing rare metal granites in the Arabian Nubian Shield (ANS). It constitutes a multiphase pluton consists of porphyritic syenogranites (SG) and coarse to medium grained highly evolved alkali-feldspar granites (AFG) intruded into the older granodiorites and metagabbro-diorite rocks. Petrographic features indicate that quartz, K-feldspar (perthite, Or97‑99), plagioclase (albite, An0‑6) and biotite are the major mineral phases of both granitic types with subordinate muscovite that is observed only in the AFG. Columbite, rutile, fluorite, zircon and thorite are the significant accessory minerals in the AFG while, allanite is exclusively encountered in the SG. Mineral chemistry study reveals that Nb-Ta-Ti-bearing oxides [columbite-group minerals (CGM)] and Nb-bearing oxides (ilmenorutile) represent the most common Nb-Ta host in the AFG. The CGM are represented mostly by complex zoned columbite-(Fe) and rarely by yttrocolumbite-(Y), with Mn/(Mn+Fe) ratios ranging from 0.17 to 0.31. Xenomorphic fluorite (F=46-51 wt%) is commonly filling the spaces between the major mineral phases and sometimes host rare metal minerals, e.g. columbite and thorite. Euhedral zoned allanite (Ce-Nd) is the common REE bearing mineral encountered in the SG. Geochemically, Gabal El-Ineigi granitoids are metaluminous (A/CNK= 0.95-0.99) related to post-collosional A2-type granites. The late phase AFG have distinctive geochemical features typical of rare-metal granites. They are highly fractionated calc-alkaline granitoids characterized by high Rb, Nb, Y, U and many HFSE contents, and extremely low Sr and Ba contents (4-35 and 13-18 ppm, respectively). Moreover, their REE patterns show pronounced negative Eu anomalies (Eu/Eu*=0.03 - 0.05) and tetrad effect (TE1,3=1.16 and 1.42), implying extensive fractionation via fluid-rock interaction that

  4. Kinetics of feldspar and quartz dissolution at 70-80°C and near-neutral pH: effects of organic acids and NaCl (United States)

    Blake, R. E.; Waltera, L. M.


    Effects of the organic acid (OA) anions, oxalate and citrate, on the solubility and dissolution kinetics of feldspars (labradorite, orthoclase, and albite) at 80°C and of quartz at 70°C were investigated at pH 6 in separate batch experiments and in media with different ionic strength (0.02-2.2 M NaCl). Although it has been shown that OAs can increase rates of feldspar dissolution, prior experiments have focused primarily on dilute, highly undersaturated and acidic conditions where feldspar dissolution kinetics are dominated by H + adsorption and exchange reactions. Many natural waters, however, are only weakly acidic and have variable ionic strength and composition which would be expected to influence mineral surface properties and mechanisms of organic ligand-promoted reactions. Oxalate and citrate (2-20 mM) increased the rate of quartz dissolution by up to a factor of 2.5. Quartz solubility, however, was not increased appreciably by these OAs, suggesting that Si-OA complexation is not significant under these conditions. The lack of significant OA-SiO 2 interaction is important to understanding the effects of OAs on the release of both Si and Al from feldspars. In contrast to quartz, both the rates of dissolution and amounts of Si and Al released from the three feldspars studied increased regularly with increasing OA concentration. Feldspar dissolution was congruent at all but the lowest OA concentrations. Total dissolved Al concentrations increased by 1-2 orders of magnitude in the presence of oxalate and citrate, and reached values as high as 43 mg/l (1.6 mM). Si concentrations reached values up to 65 mg/l (2.3 mM) in feldspar-OA experiments. Precipitation of authigenic clays was observed only in experiments without or at very low concentrations of OAs. The high concentrations of dissolved Si attained during dissolution of feldspars in OA solutions, relative to Si concentrations in quartz-OA experiments, is attributed to concomitant release of Si driven by

  5. The Thermal Expansion Of Feldspars (United States)

    Hovis, G. L.; Medford, A.; Conlon, M.


    Hovis and others (1) investigated the thermal expansion of natural and synthetic AlSi3 feldspars and demonstrated that the coefficient of thermal expansion (α) decreases significantly, and linearly, with increasing room-temperature volume (VRT). In all such feldspars, therefore, chemical expansion limits thermal expansion. The scope of this work now has been broadened to include plagioclase and Ba-K feldspar crystalline solutions. X-ray powder diffraction data have been collected between room temperature and 925 °C on six plagioclase specimens ranging in composition from anorthite to oligoclase. When combined with thermal expansion data for albite (2,3,4) a steep linear trend of α as a function of VRT emerges, reflecting how small changes in composition dramatically affect expansion behavior. The thermal expansion data for five synthetic Ba-K feldspars ranging in composition from 20 to 100 mole percent celsian, combined with data for pure K-feldspar (3,4), show α-VRT relationships similar in nature to the plagioclase series, but with a slope and intercept different from the latter. Taken as a group all Al2Si2 feldspars, including anorthite and celsian from the present study along with Sr- (5) and Pb-feldspar (6) from other workers, show very limited thermal expansion that, unlike AlSi3 feldspars, has little dependence on the divalent-ion (or M-) site occupant. This apparently is due to the necessitated alternation of Al and Si in the tetrahedral sites of these minerals (7), which in turn locks the tetrahedral framework and makes the M-site occupant nearly irrelevant to expansion behavior. Indeed, in feldspar series with coupled chemical substitution it is the change away from a 1:1 Al:Si ratio that gives feldspars greater freedom to expand. Overall, the relationships among α, chemical composition, and room-temperature volume provide useful predictive tools for estimating feldspar thermal expansion and give insight into the controls of expansion behavior in

  6. 马朗凹陷哈尔加乌组火山岩储集层特征%Characteristics of Volcanic Reservoirs of Harjiawu Formation in Malang Sag in Santanghu Basin

    Institute of Scientific and Technical Information of China (English)

    柳成志; 刘红; 王翔飞; 何仁忠; 王昕; 于海山


    Based on the data of core,thin section,scanning electron microscopy and the petrophysical property,this paper presents the characteristics of Harjiawu volcanic reservoir of the Carboniferous in Malang sag,and obtains the following understandings.①The lithology is dominated by basalt,andesite and transitional lithology;②The main lithofacies is overflow facies,explosion and volcano-sedimentary facies are secondary;③The volcanic reservoir are of medium-low porosity and low-super low permeability;④Primary porosity is not developed because of its underwater eruption,however,the pores,vugs and fractures often superimposed on the original storage space after the transformation of the post-magmatic diagenesis and woven together form the effective storage spaces;⑤The phenomena such as albitization,arfvedsonitization and Sideritization prove existence of hydrocarbon alkali fluid in the Carboniferous volcanic rocks and the extensive development of alkali metasomatism;⑥Devitrification,weathering,tectonism,metasomatism and dissolution have significant effects on the volcanic reservoir modification,which are the main diageneses for forming secondary pores and the key factors for forming effective reservoirs of the Harjiawu formation.%利用岩心、薄片、扫描电镜及物性资料,通过对三塘湖盆地马朗凹陷石炭系哈尔加乌组火山岩储集层特征的研究,得到以下认识:以玄武岩、安山岩及其过渡岩性为主;以溢流相为主,爆发相和火山沉积相次之;为中低孔、低渗透-特低渗透火山岩储集层;主要为水下喷发,原生孔隙不发育,通过岩浆期后成岩作用的改造,形成叠加在原生储集空间之上的交织在一起的孔、洞、缝构成本区的有效储集空间;由钠长石化、钠铁闪石化和菱铁矿化等现象证明了火山岩中碱性流体的存在以及碱交代作用的广泛发育;脱玻化作用、风化作用、构造作用、交代作用和溶解作

  7. The role of reaction affinity and secondary minerals in regulating chemical weathering rates at the Santa Cruz Soil Chronosequence, California (United States)

    Maher, K.; Steefel, Carl; White, A.F.; Stonestrom, D.A.


    In order to explore the reasons for the apparent discrepancy between laboratory and field weathering rates and to determine the extent to which weathering rates are controlled by the approach to thermodynamic equilibrium, secondary mineral precipitation, and flow rates, a multicomponent reactive transport model (CrunchFlow) was used to interpret soil profile development and mineral precipitation and dissolution rates at the 226 ka Marine Terrace Chronosequence near Santa Cruz, CA. Aqueous compositions, fluid chemistry, transport, and mineral abundances are well characterized [White A. F., Schulz M. S., Vivit D. V., Blum A., Stonestrom D. A. and Anderson S. P. (2008) Chemical weathering of a Marine Terrace Chronosequence, Santa Cruz, California. I: interpreting the long-term controls on chemical weathering based on spatial and temporal element and mineral distributions. Geochim. Cosmochim. Acta 72 (1), 36-68] and were used to constrain the reaction rates for the weathering and precipitating minerals in the reactive transport modeling. When primary mineral weathering rates are calculated with either of two experimentally determined rate constants, the nonlinear, parallel rate law formulation of Hellmann and Tisserand [Hellmann R. and Tisserand D. (2006) Dissolution kinetics as a function of the Gibbs free energy of reaction: An experimental study based on albite feldspar. Geochim. Cosmochim. Acta 70 (2), 364-383] or the aluminum inhibition model proposed by Oelkers et al. [Oelkers E. H., Schott J. and Devidal J. L. (1994) The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions. Geochim. Cosmochim. Acta 58 (9), 2011-2024], modeling results are consistent with field-scale observations when independently constrained clay precipitation rates are accounted for. Experimental and field rates, therefore, can be reconciled at the Santa Cruz site. Additionally, observed maximum clay abundances in the argillic horizons occur at

  8. Characterization and modes of occurrence of elements in feed coal and coal combustion products from a power plant utilizing low-sulfur coal from the Powder River Basin, Wyoming (United States)

    Brownfield, Michael E.; Cathcart, James D.; Affolter, Ronald H.; Brownfield, Isabelle K.; Rice, Cynthia A.; O'Connor, Joseph T.; Zielinski, Robert A.; Bullock, John H., Jr.; Hower, James C.; Meeker, Gregory P.


    The U.S. Geological Survey and the University of Kentucky Center for Applied Energy Research are collaborating with an Indiana utility company to determine the physical and chemical properties of feed coal and coal combustion products from a coal-fired power plant. The Indiana power plant utilizes a low-sulfur (0.23 to 0.47 weight percent S) and lowash (4.9 to 6.3 weight percent ash) subbituminous coal from the Wyodak-Anderson coal zone in the Tongue River Member of the Paleocene Fort Union Formation, Powder River Basin, Wyoming. Based on scanning electron microscope and X-ray diffraction analyses of feed coal samples, two mineral suites were identified: (1) a primary or detrital suite consisting of quartz (including beta-form grains), biotite, feldspar, and minor zircon; and (2) a secondary authigenic mineral suite containing alumino-phosphates (crandallite and gorceixite), kaolinite, carbonates (calcite and dolomite), quartz, anatase, barite, and pyrite. The primary mineral suite is interpreted, in part, to be of volcanic origin, whereas the authigenic mineral suite is interpreted, in part, to be the result of the alteration of the volcanic minerals. The mineral suites have contributed to the higher amounts of barium, calcium, magnesium, phosphorus, sodium, strontium, and titanium in the Powder River Basin feed coals in comparison to eastern coals. X-ray diffraction analysis indicates that (1) fly ash is mostly aluminate glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals; and (2) bottom ash is predominantly quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite, and spinel group minerals. Microprobe and scanning electron microscope analyses of fly ash samples revealed quartz, zircon, and monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, wollastonite, and periclase. The abundant calcium and

  9. Discovery of double-peaking potassic volcanic rocks in Langshan Group of the Tanyaokou hydrothermal-sedimentary deposit, Inner Mongolia, and its indicating significance

    Institute of Scientific and Technical Information of China (English)

    PENG Runmin; ZHAI Yusheng; WANG Zhigang; HAN Xuefeng


    It is revealed that the protolith of gray-light brown potash-feldspar-leucogranulites and granulites in the 2nd formation of the LG in Tanyaokou deposit are quartz kerotophyre of synsedimentary eruption based on the following facts and features: (1) The rocks look compact and homogeneous without obvious crystals with naked eyes; (2) they contain blastoporphyritic or glomeroporphyritic and blasto-crystalloclastic crystals consisting of quartz with wavy extinction and albite with obvious alteration and deformation; (3) they also contain radiated and fibrous blasto-microspherulitic texture and swallow-tailed bifurcate and blasto-hollow-skeleton crystal texture, representing the rapid cooling characteristic of the magma during submarine volcanic eruption; (4) the major chemical compositions of the rocks are: SiO2 = 70.80%―76.00%, K2O (4.83%―6.22%)>Na2O(2.78%―3.80%), and K2O+Na2O = 8.63%―9.00%; and (5) their petrochemical diagrams indicate that they are volcanic rocks. Together with the characteristic that they occur in the same sequence with potassic spilite (SiO2 = 46.12%―50.68%, K2O = 4.23%―5.93%>Na2O = 2.15%―3.14%, K2O+Na2O = 6.51%―8.08%), it can be confirmed that the volcanics occurring in the 2nd Formation of the LG in Tanyaokou district are double-peaking potassic volcanic rocks. The discovery, together with the tuffs with ore minerals and the distribution of lead isotopic as well as the value of Co/Ni of pyrites >1 showing the obvious endogenic metalization, can prove that the Tanyaokou deposit is an untypical SEDEX-type deposit formed in the extension fault basin in the Mesoproterozonic aulacogen of the northern margin of the North China Platform, and its metallogenesis is related to the synsedimentary volcanic activities and the hydrothermal exhalation, and both the ore-forming material source and volcanics came from mantle or lower crust. These facts mentioned above, together with the meta-volcanic rocks (double-peaking) found in the

  10. Rapid sedimentation of iron oxyhydroxides in an active hydrothermal shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan (United States)

    Kiyokawa, Shoichi; Ueshiba, Takuya


    Hydrothermal activity is common in the fishing port of Nagahama Bay, a small semi-enclosed bay located on the southwest coast of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan). The bay contains red-brown iron oxyhydroxides and thick deposits of sediment. In this work, the high concentration and sedimentation rates of oxyhydroxide in this bay were studied and the sedimentary history was reconstructed. Since dredging work in 1998, a thickness of ~ 1.0-1.5 m of iron oxyhydroxide-rich sediments has accumulated on the floor of the bay. To estimate the volume of iron oxyhydroxide sediments and the amount discharged from hydrothermal vents, sediment traps were operated for several years and 13 sedimentary core samples were collected to reconstruct the 10-year sedimentary history of Nagahama Bay. To confirm the timing of sedimentary events, the core data were compared with meteorological records obtained on the island, and the ages of characteristic key beds were thus identified. The sedimentation rate of iron oxyhydroxide mud was calculated, after correcting for sediment input from other sources. The sediments in the 13 cores from Nagahama Bay consist mainly of iron oxyhydroxide mud, three thick tephra beds, and a topmost thick sandy mud bed. Heavy rainfall events in 2000, 2001, 2002, and 2004-2005 coincide with tephra beds, which were reworked from Iwo-Dake ash deposits to form tephra-rich sediment. Strong typhoon events with gigantic waves transported outer-ocean-floor sediments and supplied quartz, cristobalite, tridymite, and albite sands to Nagahama Bay. These materials were redeposited together with bay sediments as the sandy mud bed. Based on the results from the sediment traps and cores, it is estimated that the iron oxyhydroxide mud accumulated in the bay at the relatively rapid rate of 33.3 cm/year (from traps) and 2.8-4.9 cm/year (from cores). The pore water contents within the sediment trap and core sediments are 73%-82% and 47

  11. Effect of the background solution and material composition on the transport of silver nanoparticles in saturated aquifer materials (United States)

    Adrian, Yorck; Schneidewind, Uwe; Fernandez-Steeger, Tomas; Azzam, Rafig


    Engineered silver nanoparticles (AgNP) are used in various consumer products such as cloth or personal care products due to their antimicrobial properties (Benn et al., 2010). Their transport behavior in the environment is still under investigation. Previous studies have been focusing on the transport of AgNP in simple test systems with glass beads or soil materials (Braun et al., 2015), but studies investigating aquifer material are rare. However, the protection of fresh water resources in the subsurface is an important part in the protection of human health and the assurance of future economic activities. Therefore, expert knowledge regarding the transport and fate of engineered nanoparticles as potential contaminants in aquifers is essential. Within the scope of the research project NanoMobil funded by German Federal Ministry of Education and Research, the transport and retention behavior of AgNP in aquifer material was investigated under saturated conditions in laboratory columns for different flow velocities, ionic strengths (IS) and background solutions. The used aquifer material consisted mainly of quartz and albite. The quartz grains were partially coated with iron hydroxides and oxides. Furthermore, 1% hematite was present in the silicate dominated aquifer material. The experiments were conducted using NaNO3 and Ca(NO3)2 background solutions to examine the effects of monovalent and divalent cations on the transport of AgNP. Flow velocities in the columns were chosen to represent typical flow velocities of groundwater in the subsurface. For the experiments two mean grain sizes of 0.3 and 0.7 mm were used to investigate the effect of the grain size on the transport behavior. Particle concentration was measured using ICP-MS and particle size was determined using flow field-flow fractionation (FlFFF). HYDRUS-1D (Šimůnek et al., 2013) was used to elucidate the transport and retention processes of the AgNP in the aquifer material. The obtained results show

  12. Petrophysical, Lithological and Mineralogical Characteristics of the Shale Strata of the Volga- Ural Region (United States)

    Morozov, Vladimir P.; Plotnikova, Irina N.; Pronin, Nikita V.; Nosova, Fidania F.; Pronina, Nailya R.


    The objects of the study are Upper Devonian carbonate rocks in the territory of South-Tatar arch and Melekess basin in the Volga- Urals region. We studied core material of Domanicoid facies from the sediments of Mendymski and Domanik horizons of middle substage of Frasnian stage of the Upper Devonian. Basic analytical research methods included the following: study of the composition, structural and textural features of the rocks, the structure of their voids, filter and reservoir properties and composition of the fluid. The complex research consisted of macroscopic description of the core material, optical microscopy analysis, radiographical analysis, thermal analysis, x-ray tomography, electron microscopy, gas-liquid chromatography, chromate-mass spectrometry, light hydrocarbons analysis using paraphase assay, adsorbed gases analysis, and thermal vacuum degassing method. In addition, we performed isotopic studies of hydrocarbons saturating shale rocks. Shale strata are mainly represented by carbonate-chert rocks. They consist mainly of calcite and quartz. The ratio of these rock-forming minerals varies widely - from 25 to 75 percent. Pyrite, muscovite, albite, and microcline are the most common inclusions. Calcareous and ferruginous dolomite (ankerite), as well as magnesian calcite are tracked down as secondary minerals. While performing the tests we found out that the walls of open fractures filled with oil are stacked by secondary dolomite, which should be considered as an indication moveable oil presence in the open-cut. Electron microscopy data indicate that all the studied samples have porosity - both carbonates and carbonate-siliceous rocks. Idiomorphism of the rock-forming grains and pores that are visible under a microscope bring us to that conclusion. The analysis of the images indicates that the type of reservoir is either porous or granular. The pores are distributed evenly in the volume of rock. Their size is very unstable and varies from 0.5 microns

  13. Mineralogy and chemistry of the green stone artifacts (muiraquitãs of the museums of the Brazilian State of Pará Mineralogia e química de artefatos de pedra verde (muiraquitãs dos Museus do Estado do Pará

    Directory of Open Access Journals (Sweden)

    Anna Cristina Resque Meirelles


    Full Text Available Muiraquitãs, lithic artifacts found in the Amazon basin, have been considered to be Asian in origin, or to have been sculpted by the legendary female Amazon warriors. These pieces are now very rare, and are found mainly in museum collections. In the present study, the mineralogical and chemical content of 23 specimens from the collections of the Museu de Gemas (Gemstone Museum and Museu do Encontro (Meeting Museum in Belém, Brazil, were analyzed. Most of the pieces were made of minerals commonly found in Brazil - quartz, albite, microcline, variscite, anorthite, and tremolite (the equivalent of nephritic jade. However, four of the pieces were made of jadeite, that is, jadeitic jade, which is unknown in the Amazon basin or in other parts of Brazil. The confirmation of the presence of this mineral in some of the artifacts reopens the debate on the mineralogical origin of the muiraquitãs found in the Amazon basin. Before the present discovery, their origin was defended as Amazonian due to the absence of jadeite jade in the searched pieces and the fact that jadeite was not found in Brazil but in Central America and Asia.Os muiraquitãs foram considerados de proveniência asiática ou, também, como peças esculpidas pelas lendárias mulheres guerreiras, as Amazonas. São peças, hoje, muito raras, encontradas em alguns acervos de Museus. Estudos mineralógicos e químicos de 23 peças do acervo dos Museus de Gemas e do Encontro em Belém, Brasil, mostraram que os muiraquitãs podem ser constituídos, tanto de quartzo, como de albita, ou microclínio, pirofilita, variscita, anortita e tremolita (equivalente ao jade nefrítico, minerais frequentes em formações geológicas do Brasil. No entanto quatro peças são constituídas de jadeíta, ou seja, em jade jadeítico, raro e desconhecido na Amazônia e Brasil. A constatação da presença desse mineral reacende a discussão em torno da origem mineralógica dos muiraquitãs encontrados na Amaz

  14. Mineral chemistry and magnetic petrology of the Archean Planalto Suite, Carajás Province - Amazonian Craton: Implications for the evolution of ferroan Archean granites (United States)

    Cunha, Ingrid Roberta Viana da; Dall'Agnol, Roberto; Feio, Gilmara Regina Lima


    The Planalto Suite is located in the Canaã dos Carajás subdomain of the Carajás Province in the southeastern part of the Amazonian Craton. The suite is of Neoarchean age (∼2.73 Ga), ferroan character, and A-type affinity. Magnetic petrology studies allowed for the distinction of two groups: (1) ilmenite granites showing low magnetic susceptibility (MS) values between 0.6247×10-3 and 0.0102 × 10-3 SI and (2) magnetite-ilmenite-bearing granites with comparatively higher but still moderate MS values between 15.700×10-3 and 0.8036 × 10-3 SI. Textural evidence indicates that amphibole, ilmenite, titanite, and, in the rocks of Group 2, magnetite also formed during magmatic crystallization. However, compositional zoning suggests that titanite was partially re-equilibrated by subsolidus processes. The amphibole varies from potassian-hastingsite to chloro-potassian-hastingsite and shows Fe/(Fe + Mg) > 0.8. Biotite also shows high Fe/(Fe + Mg) ratios and is classified as annite. Plagioclase porphyroclasts are oligoclase (An25-10), and the grains of the recrystallized matrix show a similar composition or are albitic (An9-2). The dominant Group 1 granites of the Planalto Suite were formed under reduced conditions below the FMQ buffer. The Group 2 granites crystallized under more oxidizing conditions on or slightly above the FMQ buffer. Pressures of 900-700 MPa for the origin and of 500-300 MPa for the emplacement were estimated for the Planalto magmas. Geothermometers suggest initial crystallization temperatures between 900 °C and 830 °C, and the water content in the magma is estimated to be higher than 4 wt%. The Neoarchean Planalto Suite and the Estrela Granite of the Carajás Province reveal strong mineralogical analogies, and their amphibole and biotite compositions have high total Al contents. The latter characteristic is also observed in the same minerals of the Neoarchean Matok Pluton of the Limpopo Belt but not in those of the Proterozoic rapakivi A

  15. Strongly foliated garnetiferous amphibolite clasts in ophiolitic melanges, Yarlung Zangbo Suture Zone, Tibet; Early Cretaceous disruption of a back-arc basin? (United States)

    Guilmette, C.; Hebert, R.; Wang, C.; Indares, A. D.; Ullrich, T. D.; Dostal, J.; Bedard, E.


    Metre to decameter-size clasts of amphibolite are found embedded in ophiolitic melanges underlying the Yarlung Zangbo Suture Zone Ophiolites, South Tibet, China. These ophiolites and melanges occur at the limit between Indian and Tibetan-derived rocks and represent remnants of an Early Cretaceous intraoceanic supra-subduction zone domain, the Neo-Tethys. In the Saga-Dazuka segment (500 km along-strike), we discovered new occurrences of strongly foliated amphibolites found as clasts in the ophiolitic melange. In garnet-free samples, hornblende is green-blue magnesio-hornblende and cpx is low-Al diopside. In garnet- bearing samples, garnet is almandine with a strong pyrope component (up to 30 mol%) whereas coexisting hornblende is brown Ti-rich tschermakite and clinopyroxene is Al-diopside. Plagioclase composition was ubiquitously shifted to albite during a late metasomatic event. Geochemistry of these rocks indicates that their igneous protoliths crystallized from a slightly differentiated tholeiitic basaltic liquid that did not undergo major fractionation. Trace element patterns reveal geochemical characteristics identical to those of the overlying ophiolitic crust. These are 1) trace element abundances similar to that of N-MORBs or BABBs, 2) a slight depletion of LREE and 3) a moderate to strong Ta-Nb negative anomaly and a slight Ti anomaly. Such characteristics suggest genesis over a spreading center close to a subduction zone, possibly a back-arc basin. Step-heating Ar/Ar plateau ages were obtained from hornblende separates. All ages fall in the range of 123-128 Ma, overlapping the crystallization ages from the overlying ophiolite (126-131 Ma). Pseudosections were built with the THERMOCALC software in the system NCFMASH. Results indicate that the observed assemblage Hb+Pl+Gt+Cpx is stable over a wide range of P-T conditions, between 10-18 kbars and at more than 800°C. Measured mineral modes and solid solution compositions were successfully modeled, indicating

  16. Volcanic facies and mineral chemistry of Tertiary volcanics in the northern part of the Eastern Pontides, northeast Turkey: implications for pre-eruptive crystallization conditions and magma chamber processes (United States)

    Yücel, Cem; Arslan, Mehmet; Temizel, İrfan; Abdioğlu, Emel


    Tertiary volcanics in the northern zone of the Eastern Pontides are characterized by subaerial and shallow-subaqueous facieses, and are divided into three volcanic suites: Eocene aged (1) basalt-trachybasalt-basaltic trachyandesite (BTB) and (2) trachyte-trachyandesite (TT), and Miocene aged (3) basanite-tephrite (BT) suites. Clinopyroxene is a common phase in all three volcanic suites, and has different compositions with Mg# varying from 0.57 to 0.91 in BTB suite and 0.57-0.84 in TT suite to 0.65-0.90 in BT suite. Feldspars in all suites generally exhibit wide range of compositions from sanidine to albite or anorthite and have weak normal and reverse compositional zoning. Olivines in BTB and BT suites have Fo60-92. Hornblendes in BTB, TT and BT suites are commonly magnesio-hastingsite and rare pargasite in composition (Mg#: 0.67-0.90). Brown mica is mainly phlogopite with Mg# ranging from 0.56 to 0.92 in the BTB suite, 0.59-0.84 in the TT suite, and 0.75-0.93 in the BT suite. Analcime is present only in the BT suite rocks. Fe-Ti oxides in all suites are mainly composed of magnetite and titanomagnetite. Textural petrographic and mineral chemical data suggest that magmas had undergone hydrous and anhydrous crystallizations in deep-, mid-, and shallow-crustal magma chambers. Clinopyroxene thermobarometric calculations show that Eocene magma chambers were characterized by temperature ranging from 1,100 to 1,244 °C and pressure ranging from 1.84 to 5.39 kbar. Similarly, the Miocene magma chambers were characterized by temperature ranging from 1,119 to 1,146 °C and pressure ranging from 4.23 to 4.93 kbar. Hornblende thermobarometry, oxygen fugacity, and hygrometer reveal that the crystallization temperature of Eocene volcanics range from 956 to 959 °C at pressure ranging from 6.49 to 6.52 kbar. Eocene volcanics were characterized by water content ranging from 7.83 to 8.57 wt.% and oxygen fugacity of 10-9.36 to 10-9.46 (ΔNNO+2). Miocene volcanics had crystallization

  17. Mineral displacement and -dissolution processes and their relevance to rock porosity and permeability in Rotliegend sandstones of the Altmark natural gas field (central Germany) - results from CO2 laboratory batch experiments (United States)

    Pudlo, Dieter; Enzmann, Frieder; Heister, Katja; Werner, Lars; Ganzer, Leonhard; Reitenbach, Viktor; Henkel, Steven; Albrecht, Daniel; Gaupp, Reinhard


    The Rotliegend reservoir sandstones of the Altmark area (central Germany) comprise the second largest natural gas field of Europe. These sandstones were deposited on a playa-like continental platform with braided river systems, ephemeral lakes and aeolian dunes under semi-arid conditions. Some of the pristine, red coloured deposits suffered intensive late diagenetic alteration and are now preserved as bleached, high porous and permeable sandstones. To evaluate the relevance of distinct fluids and their fluid-rock alteration reactions on such bleaching processes we performed laboratory static batch experiments on the Altmark sandstones. These 4-6 week lasting runs were conducted with CO2 saturated synthetic brines under typical Altmark reservoir conditions (p= 20 MPa, T= 125°C). Thereby mineralogical, petrophysical and (hydro- and geo-) chemical rock features were maintained prior and after the experiments. Chemical data proved the dissolution of carbonate and sulphate minerals during the runs, whereas the variation in abundance of further elements was within the detection limit of analytical accuracy. However, FE-SEM investigations on used, evaporated brines reveal the presence of illite and chlorite minerals within a matrix of Ca-, Si-, Fe, Al-, Na- and S components (carbonate, anhydrite, albite and Fe-(hydr-) oxides ?). By porosity and relative permeability measurements an increase in both rock features was observed after the runs, indicating that mineral dissolution and/or (clay) fine migration/detachment occurred during the experiments. Mineral dissolution, especially of pore-filling cements (e.g. carbonate-, sulphate minerals) is also deduced by BET analysis, in determining the specific surface of the sandstones. The size of these reactive surfaces increased after the experiments, suggesting that after the dissolution of pore-filling cements, formerly armoured grain rimming clay cutans were exposed to potential migrating fluids. These findings are also

  18. Petrological cannibalism: the chemical and textural consequences of incremental magma body growth (United States)

    Cashman, Kathy; Blundy, Jon


    The textures of minerals in volcanic and plutonic rocks testify to a complexity of processes in their formation that is at odds with simple geochemical models of igneous differentiation. Zoning in plagioclase feldspar is a case in point. Very slow diffusion of the major components in plagioclase means that textural evidence for complex magmatic evolution is preserved, almost without modification. Consequently, plagioclase affords considerable insight into the processes by which magmas accumulate in the crust prior to their eventual eruption or solidification. Here, we use the example of the 1980-1986 eruptions of Mount St. Helens to explore the causes of textural complexity in plagioclase and associated trapped melt inclusions. Textures of individual crystals are consistent with multiple heating and cooling events; changes in total pressure ( P) or volatile pressure () are less easy to assess from textures alone. We show that by allying textural and chemical analyses of plagioclase and melt inclusions, including volatiles (H2O, CO2) and slow-diffusing trace elements (Sr, Ba), to published experimental studies of Mount St. Helens magmas, it is possible to disambiguate the roles of pressure and temperature to reconstruct magmatic evolutionary pathways through temperature-pressure-melt fraction ( T-- F) space. Our modeled crystals indicate that (1) crystallization starts at > 300 MPa, consistent with prior estimates from melt inclusion volatile contents, (2) crystal cores grow at = 200-280 MPa at F = 0.65-0.7, (3) crystals are transferred to = 100-130 MPa (often accompanied by 10-20 °C of heating), where they grow albitic rims of varying thicknesses, and (4) the last stage of crystallization occurs after minor heating at ~ 100 MPa to produce characteristic rim compositions of An50. We hypothesize that modeled decreases in excess of ~50 MPa most likely represent upward transport through the magmatic system. Small variations in modeled , in contrast, can be effected by

  19. Geología y metalogénesis de los yacimientos de wolframio del sector centro-este del Sistema de Famatina, Argentina Geology and metallogeny of tungsten-bearing ore deposits from central-eastern Famatina System, Argentina

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    Fernando G. Sardi


    geochemical studies demonstrate that the emplacement of quartz mineralized veins did not alter the Late Precambrian- early Cambrian metapelites. This can be attributed to their low permeability and little reactivity. The magmatism of the zone took place mainly during the Ordovician and in minor proportion during the Devonian. The granitoids related to the tungsten deposits vary from granodiorites to sienogranites. Geochemically, these range from metaluminous to peraluminous, are calc-alkaline and highly differentiated. The deposits consist of quartz-veins, where the main ore mineral is wolframite, with small amounts of scheelite. The gangue is constituted by quartz and other silicates. The hydrothermal alteration of the different deposits is muscovitization (-sericitization sometimes related to mineralization, albitization, chloritization, and silicification. The joints in the granitic copula and cleavage in the metamorphic host rocks channelized the W-bearing hydrothermal solutions. The transport of W was essentially as hydroxicomplexes, and fluorine and silica complexes in an acid environment. The precipitation of wolframite may have been caused by reactions of this fluid with ferromagnesian silicates in the granite, decrease of the temperature and/or increase of the alkalinity

  20. Geochemical and technological characterization of clays of Corumbataí Formation, Paraná Basin, in the state of São Paulo, Brazil for the application in the ceramic industry. (United States)

    Christofoletti, Sergio Ricardo; Torres Moreno, Maria Margarita; Batezelli, Alessandro; Zanardo, Antenor


    The Corumbataí Formation is a geological unit of the Paraná Basin comprises a range of predominantly argillaceous facies. These clays are important from an economic point of view, because they represent important mineral deposits suppliers of raw materials for the ceramic industry in the production of ceramic tiles.The study presents preliminary results of a research that aims to study the clays municipalities Tambaú, Ferreira and Santa Rosa of Viterbo in the State of São Paulo for their application and diversification of ceramic products. The methodology used was based on a detailed description of facies using the methodology in principles of analysis of Basin Miall (1984), followed by mineralogical identification by X-ray Diffraction, chemical analysis of major elements by X-ray Fluorescence and technological tests ceramic. According to the geological surveys of mines studied through columnar sections were identified the following lithofacies from base to top: Massive, Laminated, Intercalated and Altered. The mineralogy present on these lithofacies is composed by minerals: quartz, microclineo, albite, calcite, dolomite and hematite and by clay minerals illite, kaolinite and montmorillonite. The quartz represents the mineral more present in diffraction and occurs with d001 of 3.33Å in all lithofacies studied. The illite clay mineral represents the most frequent in studied samples presenting d 001 10Å in three conditions (natural, heated and treated with ethylene glycol) in which the blade was subjected to the analysis of X-ray diffraction, the presence of kaolinite or montmorillonite occurs or not in samples. It was observed a increased frequency of some minerals in the lithofacies studied, carbonates (calcite and dolomite), hematite and feldspar occurring in the intermediate portions of the profile with a predominance in lithofacies Intercalated. The illita clay mineral occurs throughout the profile, but with greater frequency in the lithofacies Massive and

  1. Fractional crystallization of high-K arc magmas: biotite- versus amphibole-dominated fractionation series in the Dariv Igneous Complex, Western Mongolia (United States)

    Bucholz, Claire E.; Jagoutz, Oliver; Schmidt, Max W.; Sambuu, Oyungerel


    Many studies have documented hydrous fractionation of calc-alkaline basalts producing tonalitic, granodioritic, and granitic melts, but the origin of more alkaline arc sequences dominated by high-K monzonitic suites has not been thoroughly investigated. This study presents results from a combined field, petrologic, and whole-rock geochemical study of a paleo-arc alkaline fractionation sequence from the Dariv Range of the Mongolian Altaids. The Dariv Igneous Complex of Western Mongolia is composed of a complete, moderately hydrous, alkaline fractionation sequence ranging from phlogopite-bearing ultramafic and mafic cumulates to quartz-monzonites to late-stage felsic (63-75 wt% SiO2) dikes. A volumetrically subordinate more hydrous, amphibole-dominated fractionation sequence is also present and comprises amphibole (±phlogopite) clinopyroxenites, gabbros, and diorites. We present 168 whole-rock analyses for the biotite- and amphibole-dominated series. First, we constrain the liquid line of descent (LLD) of a primitive, alkaline arc melt characterized by biotite as the dominant hydrous phase through a fractionation model that incorporates the stepwise subtraction of cumulates of a fixed composition. The modeled LLD reproduces the geochemical trends observed in the "liquid-like" intrusives of the biotite series (quartz-monzonites and felsic dikes) and follows the water-undersaturated albite-orthoclase cotectic (at 0.2-0.5 GPa). Second, as distinct biotite- and amphibole-dominated fractionation series are observed, we investigate the controls on high-temperature biotite versus amphibole crystallization from hydrous arc melts. Analysis of a compilation of hydrous experimental starting materials and high-Mg basalts saturated in biotite and/or amphibole suggests that the degree of K enrichment controls whether biotite will crystallize as an early high-T phase, whereas the degree of water saturation is the dominant control of amphibole crystallization. Therefore, if a melt

  2. Is there a geochemical link between volcanic and plutonic rocks in the Organ Mountains caldera? (United States)

    Memeti, V.; Davidson, J.


    determine within-crystal geochemical variations. Our current conclusions and working hypotheses are: 1) All igneous rocks from the Organ Mountains are crustal-mantle melt mixtures indicating two component mixing; 2) the caldera-forming ignimbrites are likely derived from a fractionating Organ Needle pluton; 3) pre- and post-caldera lavas are isotopically similar to the post-caldera Sugarloaf Peak quartz-monzonite; 4) K-feldspar cumulate textures in the structurally top 0.5-1 km of the Organ Needle pluton indicate that interstitial melt was lost from the magma mush, which likely fed the ignimbrite eruptions. 5) Plutonic feldspar textures are complex compared to rather simple zoned volcanic feldspars including K-feldspar rimmed plagioclase, plagioclase rimmed K-feldspar and unrimmed feldspars occurring over a range of grain sizes at thin section scale. Some volcanic feldspar phenocrysts have any previous zonation erased due to late stage albitization. Although the single mineral studies are still work in progress and details need resolving, our data so far suggest a geochemical link between volcanic and plutonic rocks of the Organ Mountains caldera, albeit a complex one; and greater complexity in plutonic versus volcanic minerals. [1] Seager (1980), NM Bureau of Mines and Min. Res. Memoir 36, 97 p. [2] Zimmerer & McIntosh (2013) Journal of Geophysical Research, v. 93, p. 4421-4433

  3. The origin of skarn beds, Ryllshyttan Zn-Pb-Ag + magnetite deposit, Bergslagen, Sweden (United States)

    Jansson, Nils F.; Allen, Rodney L.


    component. Subsequently, the calcareous Fe formations were subjected to post-depositional alteration by hydrothermal fluids, locally yielding more manganoan and magnesian assemblages. The Mn-alteration is manifested by lateral gradations from epidote-grandite-clinopyroxene±magnetite rocks into significantly more Mn-rich quartz-spessartine rocks and massive andradite rocks over distances of less than 10 cm within individual skarn beds. Magnesian alteration is manifested by the development of discordant zones of pargasite para-amphibolites and formation of stratiform pargasite rocks texturally similar to the interlaminated grandite-epidote-ferroan diopside rocks. The latter increase in abundance towards the Ryllshyttan deposit and are associated with pre-metamorphic/pre-tectonic K-Mg-Fe±Si alteration (now biotite-phlogopite-garnet-cordierite-pargasite rocks) that is related to base metal mineralization. The zone of Mn- and Mg-altered skarn beds extends beyond the zone of pervasive K-Mg-Fe±Si alteration around Ryllshyttan. This suggests that the skarn bed progenitors, or their sedimentary contacts against rhyolitic ash-siltstones, acted as conduits to outflowing hydrothermal fluids. The chemical and mineralogical imprint, imposed on affected beds by alteration, may serve as indicators of proximity to intense K-Mg-Fe±Si alteration envelopes around other base metal sulphide deposits in Bergslagen. The last recorded event comprised syn-tectonic veining of competent massive andradite skarn beds. The veins contain quartz-albite-epidote-ferroan diopside-actinolite assemblages.

  4. Main geological settings of uranium mineralization in the Baltic shield

    International Nuclear Information System (INIS)

    dislocations, widespread permeable zones of cracks, breccia, schistosity, uraniumspecialized rocks with abundant movable varieties, massive uranium-specialized granitoid, greizenized granite and host gneiss. Uranium mineralization is in the axial parts of the FFD zones close to the contact of the Yatulian dolomite with the Ludicovian aleurolite and shungite-bearing aleurolite. It is seen on either an east-west steeply dipped or overturned anticline limb, or in the core of the nearhinge synclines. The mineralization is controlled by an area of hydrothermal-metasomatic albite-carbonate- micaceous alteration. Uranium mineralization in the FFD zones is mainly concentrated in sulfide-carbonate-pitchblende veins. Ore-bearing areas containing complex deposits are 2 - 2.5 km long and 500 - 600 m wide. There are several ore deposits lying at the depth of 100 -180m in each area. The deposits are of a complicated shoestring or cigar shape ranging in length from 1100 to 1800 m, being 15 - 50m thick. The uranium mineralization is represented with brannerite, coffinite, pitchblende. The mineralization potential of this type is determined by the discovery of five uranium-associated deposits within the Onega depression FFD zones (Srednyaya Padma, Kosmozero and others). The Early Proterozoic Kuusamo -Pana - Kuolajarvi and Imandra - Varzuga troughs characterized with widely spread uraniumspecialized black schists are highly prospective for ore deposits of this type

  5. Effects of glacial/post-glacial weathering compared with hydrothermal alteration - implications for matrix diffusion. Results from drillcore studies in porphyritic quartz monzodiorite from Aespoe SE Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Landstroem, Ove [Studsvik Eco and Safety AB, Nykoeping (Sweden); Tullborg, Eva-Lena [Terralogica AB, Graabo (Sweden); Eriksson, Gunda; Sandell, Yvonne [Studsvik Nuclear AB, Nykoeping (Sweden)


    The effects of hydrothermal + subsequent low temperature alteration and glacial/post-glacial weathering have been studied in two cores of quartz monzodiorite. One core (YA 1192) was drilled into the hydrothermally altered wall rock of a water-conducting fracture exposed at 170 m depth in the access tunnel to the Aespoe Hard Rock Laboratory. The other one (Bas 1) was drilled from an outcrop with a glacially polished surface, 1 km north of the YA 1192 site. Both drill cores were sectioned into mm-thick slices perpendicular to the core axis. The fracture filling of the YA 1192 core, the weathered surface of the BAS 1 core and the different slices were analysed for major and trace elements and isotopes of U and Th. The altered zone of the YA 1192 core extends to approx. 2.5 cm from the fracture surface. The alteration (mainly plagioclase {yields} albite + sericite + epidote) has resulted in a higher porosity and formation of sorbing secondary minerals (e.g. sericite), favouring matrix diffusion. Increased Br concentrations in the altered zone are indicative of saline water in pores and micro fractures i.e. the presence of a diffusion medium. 234U/238U activity ratios > 1 and increased Cs in the altered zone are then interpreted as diffusion of U and Cs from fracture groundwater and subsequent sorption. The U migration is geologically recent (< 1 Ma). The 2.5 cm altered zone (corresponding to the zone of active matrix diffusion) significantly exceeds the visible red staining zone (0.5 cm) caused by hematite/FeOOH micrograins, emphasizing the need of microscopy to identify zones of alteration. The conspicuous weathering at the BAS 1 site is confined to a narrow rim of the bedrock surface (approx. 0.2-0.5 cm thick). Mass balance calculations for this rim (based on immobility of K) indicate that mechanical erosion has dominated over chemical dissolution processes (is roughly 10 times greater). The chemical weathering has affected mainly plagioclase and chlorite resulting

  6. The Friningen Garnet Peridotite (central Swedish Caledonides). A good example of the characteristic PTt path of a cold mantle wedge garnet peridotite (United States)

    Gilio, Mattia; Clos, Frediano; van Roermund, Herman L. M.


    We present pseudosections of Cr-bearing garnet peridotite that together with new mineral-chemical data allow quantification of the early PT conditions of the original lithospheric mantle assemblage (M1) of the Friningen Garnet Peridotite (FGP) located in the central/middle belt of the Seve Nappe Complex in central Sweden. Results indicate that the early, coarse grained, olivine + orthopyroxene + clinopyroxene + "high Cr" garnet assemblage (M1a) was formed at 1100 ± 100 °C and 5.0 ± 0.5 GPa. These metamorphic conditions were followed by an inferred late Proterozoic exhumation event down to 850-900 °C and 1.5 GPa (M1b). The latter PT estimate is based on the breakdown of high-Cr M1a garnet (Cr# = 0.065) + olivine into an orthopyroxene + clinopyroxene + spinel (Cr# = 0.15-0.25) ± pargasite kelyphite (M1b) and the exsolution of garnet from Al-rich orthopyroxene and clinopyroxene. The M1b kelyphite is overprinted by an early-Caledonian UHPM mineral assemblage (M2; T = 800 °C and P = 3.0 GPa), equivalent to the earlier discovered UHP assemblage within an eclogitic dyke that cross-cuts FGP. In the garnet peridotite M2 is displayed by low-Cr garnet (Cr# = 0.030) growing together with spinel (Cr# = 0.35-0.45), both these minerals form part of the olivine + orthopyroxene + clinopyroxene + garnet + spinel + pargasite M2 assemblage. The formation of plagioclase + diopside symplectites after omphacite and breakdown of kyanite to sapphirine + albite in internal eclogite and the breakdown of M2 olivine + garnet to amphibole + orthopyroxene + spinel assemblages (M3) in garnet peridotite indicate post-UHP isothermal decompression down to 750-800 °C and 0.8-1.0 GPa (= M3). Multiphase solid-and fluid inclusion assemblages composed of Sr-bearing magnesite, dolomite or carbon decorate linear defect structures within M1a-b minerals and/or form subordinate local assemblages together with M2 minerals. The latter are interpreted as evidence for infiltration of early-Caledonian COH

  7. Metasomatism-controlled nucleation and development of paired-shear zone: an example from the Neves area (Eastern Alps, Italy) (United States)

    Link, Gaétan; Goncalves, Philippe; Lanari, Pierre; Oliot, Emilien


    Ductile shear zones reflects the process of strain localization in the middle and the lower crust. Several studies have shown that shear zones are characterized by significant syn-kinematic changes in mineralogy and chemical composition linked to fluid circulation, little attention has been paid to the role of chemical processes on strain localization comparison to mechanical processes. In the Neves area (Tauern window, Eastern Alps, Italy), a Variscan granodiorite is affected by an Alpine deformation, under amphibolite facies conditions. This deformation is characterized by the nucleation of single shear zones on inherited brittle structures, and paired-shear zones flanking a bleached zone developed to either side of the fractures and aplitic dykes (Mancktelow and Pennacchioni 2005). In this contribution, we focus our attention on the paired-shear zones developed on metasomatic halos surrounding fractures, which can give insights into interactions between fluid transfer, metasomatism, mineral reactions and deformation. In the undeformated granodiorite, the mineralogical assemblage consists of quartz, K-felspar, saussuritized plagioclase and biotite. The metasomatic bleached zone consists of a mineralogical assemblage of quartz and feldspar (mainly albite). The central fracture is filled with epidote. The shear zone that nucleated on the wall of the bleached zone is characterized by the crystallization of new metamorphic phases at the expense of primary magmatic and secondary metasomatic phases: garnet on former plagioclase site, phengite in the foliation, epidote and Fe and Ti-oxydes. The P-T conditions of the ductile deformation stage, associated with metasomatism, are estimated at 520°C - 0,55 Gpa, based on growth chemical zonation of garnets. Garnet shows distinct morphology depending on its textural setting: euhedral garnet is characterized by a growth chemical zonation with an enriched-Mn core and an enriched-Fe rim, in the deformed metagranodiorite; atoll

  8. Structure, alteration, and geochemistry of the Charlotte quartz vein stockwork, Mt Charlotte gold mine, Kalgoorlie, Australia: time constraints, down-plunge zonation, and fluid source (United States)

    Mueller, Andreas G.


    The Kalgoorlie district in the Archean Yilgarn Craton, Western Australia, comprises two world-class gold deposits: Mt Charlotte (144 t Au produced to 2013) in the northwest and the Golden Mile (1,670 t Au) in the southeast. Both occur in a folded greenschist-facies gabbro sill adjacent to the Golden Mile Fault (D2) in propylitic alteration associated with porphyry dikes. At Mt Charlotte, a shear array of fault-fill veins within the Golden Mile Fault indicates sinistral strike-slip during Golden Mile-type pyrite-telluride mineralization. The pipe-shaped Charlotte quartz vein stockwork, mined in bulk more than 1 km down plunge, is separated in time by barren D3 thrusts from Golden Mile mineralization and alteration, and occurs between two dextral strike-slip faults (D4). Movement on these faults generated an organized network of extension and shear fractures opened during the subsequent infiltration of high-pressure H2S-rich fluid at 2,655 ± 13 Ma (U-Pb xenotime). Gold was deposited during wall rock sulphidation in overlapping vein selvages zoned from deep albite-pyrrhotite (3 g/t Au) to upper muscovite-pyrite assemblages (5 g/t Au bulk grade). Chlorite and fluid inclusion thermometry indicate that this kilometre-scale zonation is due to fluid cooling from 410-440 °C at the base to 350-360 °C at the top of the orebody, while the greenstone terrane remained at 250 °C ambient temperature and at 300 MPa lithostatic pressure. The opened fractures filled with barren quartz and scheelite during the retrograde stage (300 °C) of the hydrothermal event. During fracture sealing, fluid flux was periodically restricted at the lower D3 thrust. Cycles of high and low up-flow, represented by juvenile H2O-CO2 and evolved H2O-CO2-CH4 fluid, respectively, are recorded by the REE and Sr isotope compositions of scheelite oscillatory zones. The temperature gradient measured in the vein stockwork points to a hot (>600 °C) fluid source 2-4 km below the mine workings, and several

  9. Mass transfer and fluid evolution in late-metamorphic veins, Rhenish Massif (Germany): insight from alteration geochemistry and fluid-mineral equilibria modeling (United States)

    Marsala, Achille; Wagner, Thomas


    Element mobility and fluid-rock interaction related to the formation of late-metamorphic quartz veins have been studied by combination of mineral chemistry, whole-rock geochemistry, mass balance analysis and fluid-mineral equilibria modeling. The quartz veins are hosted by very low-grade metasedimentary rocks of the fold-and-thrust belt of the Rhenish Massif (Germany). The veins record two stages of evolution, a massive vein filling assemblage with elongate-blocky quartz, chlorite, apatite and albite, and a later open space filling assemblage with euhedral crystals of quartz, ankerite-dolomite and minor calcite and sulfides. Detailed mass balance analysis of an alteration profile adjacent to a representative quartz vein demonstrates that element mobility is restricted to the proximal zone. The most important element changes are gain of Ca, Fe, Mg, Mn, P and CO2, and loss of Si, K and Na. The data demonstrate that wall-rock carbonation is one of the main alteration features, whereas mobility of Si, K and Na are related to dissolution of quartz and destruction of detrital feldspar and muscovite. The whole-rock geochemical data, in conjunction with fluid composition data and pressure-temperature estimates, were used as input for fluid-mineral equilibria modeling in the system Si-Al-Fe-Mg-Ca-Na-K-C-S-O-H-B-F-Cl. Modeling involved calculation of rock-buffered fluid compositions over the temperature interval 100-500 °C, and reaction-path simulations where a rock-buffered high-temperature fluid reacts with fresh host-rocks at temperatures of 400, 300 and 200 °C. Calculated rock-buffered fluid compositions demonstrate that retrograde silica solubility is a strong driving force for quartz leaching in the temperature-pressure window of 380-450 °C and 0.5 kbar. These conditions overlap with the estimated temperatures for the initial stage of vein formation. Reaction-path models show that high-temperature alteration can produce the observed silica leaching, suggesting that

  10. Axial Belt Provenance: modern river sands from the core of collision orogens (United States)

    Resentini, A.; Vezzoli, G.; Paparella, P.; Padoan, M.; Andò, S.; Malusà, M.; Garzanti, E.


    Collision orogens have a complex structure, including diverse rock units assembled in various ways by geodynamic processes. Consequently, orogenic detritus embraces a varied range of signatures, and unravelling provenance of clastic wedges accumulated in adjacent foreland basins, foredeeps, or remnant-ocean basins is an arduous task. Dickinson and Suczek (1979) and Dickinson (1985) recognized the intrinsically composite nature of orogenic detritus, but did not attempt to establish clear conceptual and operational distinctions within their broad "Recycled Orogenic Provenance". In the Alpine and Himalayan belts, the bulk of the detritus is produced by focused erosion of the central backbone of the orogen, characterized by high topography and exhumation rates (Garzanti et al., 2004; Najman, 2006). Detritus derived from such axial nappe pile, including slivers of thinned continental-margin lithosphere metamorphosed at depth during early collisional stages, has diagnostic general features, which allows us to define an "Axial Belt Provenance" (Garzanti et al., 2007). In detail, "Axial Belt" detrital signatures are influenced by metamorphic grade of source rocks and relative abundance of continental versus oceanic protoliths, typifying distinct subprovenances. Metasedimentary cover nappes shed lithic to quartzolithic detritus, including metapelite, metapsammite, and metacarbonate grains of various ranks; only amphibolite-facies metasediments supply abundant heavy minerals (e.g., almandine garnet, staurolite, kyanite, sillimanite, diopsidic clinopyroxene). Continental-basement nappes shed hornblende-rich quartzofeldspathic detritus. Largely retrogressed blueschist to eclogite-facies metaophiolites supply albite, metabasite and foliated antigorite-serpentinite grains, along with abundant heavy minerals (epidote, zoisite, clinozoisite, lawsonite, actinolitic to barroisitic amphiboles, glaucophane, omphacitic clinopyroxene). Increasing metamorphic grade and deeper

  11. Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria (United States)

    Sverjensky, D.A.; Hemley, J.J.; d'Angelo, W. M.


    The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K2O- and Na2O-Al2O3-SiO2-H2O-HCl (e.g., K-fs - Ms - Qtz - K+ - H+). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies (Berman, 1988) with the properties of aqueous species calculated from a calibrated equation of state (Shock and Helgeson, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25??C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300??C and Psat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates (Berman, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 (??500) cal/mol to all the K- and Na-bearing silicates, respectively, in Berman (1988) are required. In all cases, the revised values are within ??0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from Helgeson et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600??C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance-derived dissociation

  12. La Hornblendita Ushuaia (Tierra del Fuego:: Petrografía, geoquímica y geocronología The Ushuaia Hornblendite (Tierra del Fuego: petrography, geochemistry and geochronology

    Directory of Open Access Journals (Sweden)

    R. D. Acevedo


    -piroxenites, diorites, gabbros, syenites and monzodiorites. The mineralogy of the most representative specimen shows that it is composed of hornblende and diopside as essential minerals, with biotite and potassic feldspar as minor constituents, and sphene, apatite, and opaque minerals (mainly magnetite, ilmenite, pyrite and chalcopyrite as accessories. Alteration processes include albitization, epidotization, chloritization and carbonatization, that represent substantial chemical changes that would affect any chemical classification of the rocks. Nevertheless, it is considered that the parental magma was of calc-alkaline Andean Type, related to the Andean Batholith, produced during regional subduction, and not in any way to an ophiolitic sequence. The calc-alkaline geochemistry is attributed to partial melting. In fact, the magma did not derive from primary mantle melts but came from evolved and contaminated mantle fluids that ascended toward crustal levels, thus favouring an assimilation process, in a magmatic arc setting. Potassium-argon whole-rock dating of one hornblendite sample gave an age of 113 ± 5 Ma

  13. Gneiss wastes as secondary raw material for the ceramic industry: an example from the Verbano Cusio Ossola district (Piedmont, north-western Alps, Italy) (United States)

    Cavallo, Alessandro


    -feldspathic rocks (i.e. Serizzo and Beola), are potential sources of secondary raw materials for the ceramic industry. To assess the feasibility of a reuse of these waste materials, an extensive sampling was performed on the main quarry dumps. The waste rocks were characterized by polarized light optical microscopy (OM) on thin sections, scanning electron microscopy (SEM), quantitative X-ray powder diffraction (XRD-QPA with the Rietveld method), electron microprobe (WDS and EDS) and whole-rock geochemistry (ICP-AES, ICP-MS and LECO®). The performed analyzes show a marked mineralogical and chemical heterogeneity (e.g. highly variable content of phyllosilicates, FeOtot content between 0.39 and 6.99 wt.%), as well as important textural and granulometric differences. On the other hand, the composition of feldspars is quite homogeneous, with the plagioclase ranging from almost pure albite to oligoclase (An 25 - 30%). Some varieties of Serizzo and Beola (Serizzo Sempione, Serizzo Formazza and Beola Bianca) are preferable because of their relatively low FeOtot content, but granulometric and textural factors should never be overlooked, as they have an important feedback in the efficiency and feasibility of the industrial treatments (e.g. magnetic separation). Specifically, some Beola varieties with particularly fine grain size and mylonitic texture, are poorly-suited to industrial ore treatments. On the contrary, the Serizzo varieties, although with a generally higher FeOtot content, have a coarser and homogeneous (and therefore preferable) grain size. Waste materials with different composition could be mixed properly until reaching the desired "ideal" compositions for the following industrial treatments. In any case, an accurate characterization of the waste materials from each of quarry dump is of fundamental importance.

  14. Experimental approach to form anorthositic melts: phase relations in the system CaAl2Si2O8 - CaMgSi2O6 - Mg2SiO4 at 6 wt.% H2O (United States)

    Zirner, Aurelia Lucretia Katharina; Ballhaus, Chris; Fonseca, Raúl; Müncker, Carsten


    Massive anorthosite dykes are documented for the first time from the Limassol Forest Complex (LFC) of Cyprus, the LFC being a deformed equivalent of the Troodos ultramafic massif. Both the Troodos and LFC complexes are part of the Tethyan realm consisting of Cretaceous oceanic crust that formed within a backarc basin 90 Ma ago and was obduced during late Miocene. From crosscutting relations with the sheeted dyke complex, it follows that the anorthosites belong to one of the latest magmatic events on Cyprus. In hand specimen, the rocks appear massive and unaltered, although in thin section magmatic plagioclase (An93) is partially replaced by albite and thomsonite (zeolite). Where magmatic textures are preserved, plagioclase forms cm-sized, acicular, radially arranged crystal aggregates that remind of spinifex textures. Six major types of anorthosite occurrences have previously been described, none of them matching with the above described anorthosite dykes [1]. The origin of these anorthosite dykes remains poorly understood. Even though they occur as intrusive dykes, it is evident that they cannot represent liquidus compositions, at least under dry conditions. Whole-sale melting of pure An93 would require temperatures in excess of 1450 °C, which is a quite unrealistic temperature of the modern Earth's crust. The working hypothesis is that boninitic melts with approximately 4 wt.% H2O, as found in the cyprian upper pillow lavas (UPL), could produce such rocks by olivine-pyroxene fractionation. Indeed, experiments indicate that such lithologies can be generated by medium-pressure fractional crystallization of hydrous basaltic melts followed by decompression-degassing. High pH2O stabilizes olivine but tends to suppress plagioclase as the highest polymerized phase. Hence the An component is accumulated in the (late-stage) melt. When such a system experiences sudden decompression, the aqueous phase will exsolve and will trigger massive precipitation of anorthite

  15. Abiotic Degradation Rates for Carbon Tetrachloride: and Chloroform: Progress in FY 2008

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Wietsma, Thomas W.; Truex, Michael J.


    20°C, which are most germane to the groundwater environment, will likely take two more years before they are complete. Second, due to the importance of heterogeneous effects, we recommend the continuation of sampling and analysis for a similar set of experiments looking at hydrolysis rates of CT and CF in contact with individual minerals (montmorillonite, kaolinite, albite, and muscovite) or Hanford-Site sediment, and, for CF, in homogeneous solutions. These experiments were set up under a separate project funded by a congressional earmark (EM-22) for which funding expired at the end of FY08. Third, we strongly recommend development of a 13C/12C isotope ratio mass spectrometry (IRMS) approach for determination of hydrolysis rates at groundwater temperatures and relevant CT and CF concentrations. The technique is sensitive enough that we expect to be able to shorten the time required for a rate-constant determination by 20-fold. Thus, a 5-year experiment conducted by the sealed-ampule approach could be shortened to 3 months by the IRMS approach. This sensitivity also would allow the IRMS technique to be used to follow hydrolysis rates at concentrations found in groundwater plumes at Hanford.

  16. Static and fault-related alteration in the lower ocean crust, IODP Expedition 345, Hess Deep (United States)

    McCaig, Andrew; Faak, Kathrin; Marks, Naomi; Nozaka, Toshio; Python, Marie; Wintsch, Robert; Harigane, Yumiko; Titarenko, Sofya


    IODP Expedition 345 drilled the first holes in the lower plutonic crust at a fast-spreading ridge, recovering primitive layered gabbros (Gillis et al 2014). Alteration can be subdivided into two series: 1) a largely static pseudomorphic alteration affecting predominantly olivine. This began in the amphibolite facies with minor secondary cinopyroxene and hornblendic amphibole replacing primary pyroxene, and sporadically developed corona textures with tremolite and chlorite replacing olivine and plagioclase respectively, but was predominantly in the greenschist and sub-greenschist facies with talc, serpentine, clay minerals,oxides andsulphides replacing olivine, and prehnite and locally other calcsilicates replacing plagioclase, commonly in micro-vein networks. Albitic plagioclase is sporadically developed, and locally zeolite and carbonate. 2) An overprinting metasomatic alteration under sub-greenschist or perhaps lowermost greenschist conditions(zeolite. This alteration is spatially related to cataclastic fault zones and macroscopic veins. Comminuted plagioclase in cataclasites is commonly completely replaced by prehnite, while chlorite may completely pseudomorph olivine, locally with textures suggesting replacement of previous secondary minerals such as talc and serpentine. Chlorite also ubiquitously occurs as patches replacing plagioclase along grain boundaries, locally associated with carbonate and amphibole needles. Metamorphosed dykes show chilled margins within the cataclasites, and are affected by cataclastic deformation. Faults, dykes and overprinting alteration are all inferred to be related to the westward propagation of Cocos-Nazca spreading that formed Hess Deep. Samples of different alteration and cataclastic domains were cut out of this section chips for isotopic analysis. 87Sr/86Sr ratios of cataclasites and dyke rocks are in the range 0.7037 - 0.7048, indicating alteration by seawater at moderate integrated fluxes. The highest values were in

  17. Los sistemas geotermales del Pirineo central. I. Caracteres geoquímicos y fisicoquímicos de los manantiales termales

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    Gómez, J.


    Full Text Available The compositional characters of selected hot springs from the Panticosa, Benasque, Arties, Caldas de Bohí, Luchon and Cauterets geothermal systems in the Central Pyrenees have been studied. All the springs have the same global geochemical features (high pH, low total dissolved solids, very low Mg concentrations, Na as the dominant cation, and absence of a dominant anion and belong to the same granite-related alkaline thermal waters group. Chemical composition of the springs is similar to each other, and to that found in other Pyrenean geothermal systems. A more detailed comparison shows, however, that Panticosa and Benasque systems have the lowest sodium and potassium concentrations found in any water belonging to the group of alkaline waters. Differences in pH values among the springs are related to emergence temperature as it occurs in the Pyrenean geothermal systems. According to the high pH of these waters, speciation calculations at emergence temperature show a very low CO2 partial pressure, dissolved silica partially ionized as H3Si04-, and Al(OH4- as the dominant aluminium species. Saturation indexes show that almost al1 the waters are highly oversaturated with quartz (close to equilibrium with chalcedony, potassium feldspar, and albite, which are the minerals equilibrated at depth with the solutions. Furthermore, all waters are in equilibrium with kaolinite and ca1cite at emergence conditions, showing the existence of a reequilibrium process during their ascent to the surface. This process happens to be one of the most important in the geochemical evo1ution of these alkaline systems.Las aguas de los sistemas geotermales de Panticosa, Benasque, Arties, Caldas de Bohí, Luchon y Cauterets en el Pirineo Central presentan rasgos geoquímicos similares (valores de pH elevados, bajo contenido de sólidos disueltos, muy bajas concentraciones de Mg, sodio como catión dominante y sin un anión en proporciones preponderantes sobre los dem

  18. 新疆南部祖母绿(绿柱石)成矿地质条件初探%Preliminary discussion of the the metailogenic conditions of emerald deposit, Southern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    禹秀艳; 李甲平; 汪立今; 罗卫东; 石玉君; 陈勇; 陈俊华


    The emeralds of Xinjiang are good in quality, and the deposit has enormous potential yields of excellent quality emerald. This paper is mainly to analyze the geological characteristics of this deposit, including the regional geological features; mining and geological characteristics of ore body; ore mineralogi-cal characteristics of micro. The formation and distribution of emerald ore bodies found in Xinjiang are controlled by regional stratigraphy, magmatic, tectonic and other factors. Emerald (Beryl) Produced in the carbonaceous limestone, shale, calcite, calcite-quartz veinlets. Veins mostly were shaped by oblique veins, bedding pulse. Based on this study, according to samples collected, carrying on microscopic order of mineral assemblages and the formation of micro-mineralogy, mineralization process will be divided into three periods, namely before mineralization, mineralization period, after forming, obtained in the main ore minerals of the formation of calcite, quartz, albite, beryl, etc.. Through this research, the area emerald (beryl) exploration of important guiding significance.%新疆南部首次发现质量好的祖母绿(绿柱石),其成矿地质条件研究意义重大.本文主要对新疆南部祖母绿(绿柱石)矿的成矿地质条件进行初步探讨,包括区域地质特征、矿区及矿体地质特征、矿石显微矿物学特征等.发现新疆祖母绿矿体的形成和分布,受区内地层、岩浆、构造等多种因素和条件限制.祖母绿(绿柱石)多产于含碳质灰岩、页岩的方解石、方解石-石英细脉中,含祖母绿(绿柱石)矿脉多以斜交脉、顺层脉产出.在此研究基础上,根据所采集的样品,进行了显微矿物组合特征和生成顺序的微观矿物学研究,将成矿作用过程划分为三个期次,即成矿前、成矿期、成矿后.得出在成矿期形成的主要矿物为方解石、石英、钠长石、绿柱石等.通过上述研究,对该区祖母绿(绿柱石)找矿具有重要的指导意义.

  19. Deep subduction of hot young oceanic slab required by the Syros eclogites (United States)

    Flemetakis, Stamatis; Moulas, Evangelos; Kostopoulos, Dimitrios; Chatzitheodoridis, Elias


    The Cycladic islands of Syros and Siphnos, Aegean Sea, Greece, represent subducted IAT and BABB remnants of the Neotethyan Pindos Ocean. Garnet porphyroblasts (Ø=1mm) in a glaucophane-zoisite eclogite from Kini locality on Syros are compositionally zoned and display a unique prograde heating path from a high-pressure greenschist-facies core with high XSps and low Mg# via a blueschist-facies mantle with moderate XSps and Mg# to an eclogite-facies rim with low XSps and high Mg#. The outermost 35 μm of the garnet rims show flat XSps with rapidly increasing outwards Mg#. Na-Act-Chl-Ph rimmed by Gln mark the greenschist-blueschist facies transition, whereas Pg rimmed by Omp and the incoming of Rt at the expense of Ttn signify the blueschist-eclogite facies transition. Raman barometry of quartz inclusions in the eclogitic garnet rims coupled with elastic modelling of the garnet host [1], and Zr-in-Rt and Grt-Cpx-Ph thermobarometry revealed near-UHP P-T conditions of the order of 2.6 GPa/660°C (maximum residual pressure was 0.8-0.9GPa). By contrast, the greenschist-blueschist transition lies at ~0.75 GPa/355°C. This pressure is in excellent agreement with the position of the albite = jadeite + quartz boundary calculated at 350°C using the observed omphacite composition corrected for jadeite activity (Koons & Thompson, 1985) [2]. As a result, Cpx inclusions in garnet core signify the early entrance of garnet in the subduction zone history of the slab. Furthermore, the early growth of garnet (in lower pressures) observed in eclogites from Syros lies in great agreement with published slab-geotherms that indicate hot subduction and show a precocious garnet growth (Baxter and Caddick, 2013) [3]. The complete absence of lawsonite and the great abundance of zoisite crystals, based on the stability fields of both minerals (Poli et al., 2009) [4], further constrain the P-T trajectory of the slab. Our new P-T estimates match published T distributions on the slab surface

  20. Chemical composition of gahnite and degree of pegmatitic fractionation in the Borborema Pegmatitic Province, northeastern Brazil

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    Dwight R. Soares


    Full Text Available Gahnite electron probe microanalyses from three pegmatites (Mirador, Capoeira and Quintos of the Borborema Pegmatitic Province in northeastern Brazil allowed to determine molar compositions ranging from 86.22 to 95.41 mol% gahnite (ZnAl2O4, 1.51 to 6.62 mol% hercynite (Fe2+Al2O4, 0.11 to 5.89 mol% spinel (MgAl2O4, 1.48 to 2.74 mol% galaxite (MnAl2O4, and Zn/FeTotal atomic ratios ranging from 11.53 to 60.87. These data compared with gahnite compositions from albite subtype pegmatites from Cap de Creus, Spain (Zn/FeTotal between 10 and 60 and from the source granite of the Separation Rapids pegmatite field, Ontario, Canada (Zn/FeTotal =3.5 indicate a high degree of fractionation of the studied pegmatites. This interpretation agrees with conclusions based on compositional data of tourmaline (vacancy in X-site 0.42 to 0.49, white mica (K/Rb between 8 and 33, feldspar (K/Rb between 8 and 109, garnet (Mn/(Mn+Fe2+between 0.93 and 0.97 and in Nb-Ta oxides (Mn/(Mn+Fe2+>0.5 in the same pegmatites.Análises via microssonda eletrônica de gahnita de três pegmatitos (Mirador, Capoeira e Quintos da Província Pegmatítica da Borborema, no Nordeste do Brasil, permitiram estabelecer uma composição molar variando entre 86,22 e 95,41 mol% de gahnita (ZnAl2O4, 1,51 e 6,62 mol% de hercinita (Fe2+Al2O4, 0,11 e 5,89 mol% de espinélio (MgAl2O4, 1,48 e 2,74 mol% de galaxita (MnAl2O4 e relação Zn/FeTotal variando entre 11,53 e 60,87. Estes dados comparados com os de gahnita dos pegmatitos subtipo albita de Cap de Creus, Espanha (Zn/FeTotal variando entre 10 e 60 e gahnita de fonte granítica do campo pegmatítico Separation Rapids, Ontário, Canadá (Zn/FeTotal = 3,5 indicam um alto grau de fracionamento dos pegmatitos estudados. Esta interpretação está de acordo com conclusões baseadas em dados de turmalina (vacância no sítio X variando entre 0,42 a 0,49, mica clara (K/Rb variando entre 8 e 33, feldspato (K/Rb variando entre 8 e 109, granada (Mn/(Mn+Fe2

  1. Geology, Mineralogy and Geochemistry of the Mount Deans Pegmatite Field, Eastern Yilgarn Craton/Australia (United States)

    Dittrich, Thomas; Seifert, Thomas; Schulz, Bernhard


    Lithium-Cesium-Tantal (LCT) pegmatites are an important source for the rare metals Li, Cs and Ta, commodities that are now consumed in a rapidly increasing amount in high technology applications. Despite that LCT pegmatites are characteristic features for the Archaean geology of Western Australia, only the Greenbushes, Cattlin Creek and Wodgina deposits are currently exploited for Li and Ta. Therefore, Western Australia still possesses a great potential for the identification of additional resources for Li, Ta and possibly also Cs. The present study presents an overview of the geology, mineralogy and geochemistry of the Mount Deans pegmatite field, located c. 13 km S of Norseman, in the Eastern Goldfields Terrane of the Yilgarn Craton. The Mount Deans pegmatite field is Meso- to Neo-Archaean in age and hosted in the N-S trending Dundas Hill greenstone belt. The pegmatite field covers an area of 6 km in N-S and 4 km in E-W extension and comprises several dozens of individual pegmatite sheets and lenses. Structurally the pegmatite bodies are subdivided into two distinct types. Type I occurs predominantly in the southern part, is gently dipping (5-10°) to various directions and has variable thicknesses (3-25 m). Type II occurs in the northern part of the pegmatite field, dips steeply (50-90°) with a general N-S striking and has only a limited thickness (10 cm to 5 m). A clear distinction can also be made through their internal structure and mineralogy. Type I pegmatites exhibit a distinct structural and mineralogical zoning, whereas type II pegmatites are unzoned. Also albite, zinnwaldite, lepidolite and quartz form the bulk of the pegmatite; lepidolite is considerably more common in type II. Based on its peraluminous and strongly calc-alkaline character, as well as its enrichment in rare elements (i.e., Li, Rb, Cs, Ta, Nb, F), the pegmatites at Mount Deans are interpreted as LCT-pegmatites. However, despite the occurrence of rare element minerals like cassiterite

  2. The ophiolite of the Eohellenic nappe in the island of Skyros, Greece: Geotectonic environment of formation and metamorphic conditions inferred by mineralogical and geochemical data (United States)

    Karkalis, Christos; Magganas, Andreas; Koutsovitis, Petros


    The island of Skyros is located in the Sporades-Aegean region. It includes an ophiolitic mélange sequence consisting of serpentinites, gabbroic and doleritic rocks, and also lavas which mostly appear in massive form, but in rare cases as deformed pillows. The ophiolitic mélange sequence also includes rodingites, ophicalcites, as well as radiolarites. This formation belongs to the Eohellenic tectonic nappe, which encompasses marbles, sandstones and schists and was emplaced onto the Pelagonian Zone during Early Cretaceous [1, 2]. Serpentinites were most likely formed after serpentinization of harzburgitic protoliths and consist of serpentine, bastite, spinel and magnetite. The chemistry of spinels (TiO2=0.14-0.25 wt.%, Al2O3=35.1-35.21 wt.%, Cr#=37.38-38.87), shows that the harzburgitic protoliths plausibly resemble back-arc basin peridotites [3]. Gabbros and dolerites present mostly subophitic textures, between the hornblende/clinopyroxene and plagioclase grains. Based upon their petrography and on their mineral chemistry hornblendes have been distinguished into magmatic and metamorphic hornblendes, with the first occurring mostly in gabbroic rocks. Magmatic hornblendes exhibit relatively high TiO2 (1.42-1.62 wt.%), Al2O3 (5.11-5.86 wt.%) and Na2O (1.01-1.09 wt.%) contents, with their presence implying that the magma was at least to some degree hydrous. Lavas are tholeiitic basalts with relatively high FeOt≡12 wt.% and low K2O and Th contents, consisting mostly albite, altered clinopyroxene and devitrified glass. Tectonomagmatic discrimination diagrams [4, 5] illustrate that the studied gabbros and lavas of Skyros are most likely associated with SSZ processes. Gabbroic rocks, subvolcanic dolerites and lavas have been subjected to greenschist/subgreenschist metamorphic processes, as confirmed by the presence of secondary amphiboles (metamorphic hornblende, actinolite/tremolite), epidote, pumpellyite and chlorite in all of the studied samples. On the other hand

  3. Multi-stage barites in partially melted UHP eclogite: implications for fluid/melt activities during deep continental subduction in the Sulu orogenic belt (United States)

    Wang, Songjie; Wang, Lu


    . Zr-in-rutile thermometry shows their formation temperature to be 586-664 oC at 1.5-2.5 GPa. Barite-bearing MS inclusions with Ba-bearing K-feldspar (type-II) connected by Kfs+Pl+Bt veinlets of in-situ phengite breakdown and thin barite veinlets along grain boundaries (type-III) are products of phengite breakdown and induced fluid flow during exhumation. These barites have witnessed the gradational separation process of melt/ fluid from miscibility on/above the second critical endpoint during UHP metamorphism, to immiscibility along the exhumation path of the subducted slab. Associated reactions from pyrite to hematite and goethite with the type-III barite ring surrounding the pyrite provide evidence for a local high oxygen fugacity environment during eclogite partial melting and subsequent melt/fluid crystallization processes. Moreover, large grain barite aggregations (type-IV) modified by amphibole+albite symplectite are most likely formed by release of molecular and hydroxyl water from anhydrous minerals of eclogite during high-grade amphibolite-facies retrogression. The growth of multi-stage barites in UHP eclogite further advances our understanding of fluid/melt transfer, crystallization processes along the subduction-exhumation path of the partially melted eclogite, broadening our knowledge of melt/fluid evolution within subduction-collision zones worldwide. REFERENCES Chen Y.X., et al., 2014, Lithos, 200, 1-21. Liu J.B., et al., 2000, Acta Petrologica Sinica 16(4), 482-484. Zeng L.S., et al., 2007, Chinese Science Bulletin, 52(21), 2995-3001. Gao X.Y., et al., 2012, Journal of Metamorphic Geology, 30(2), 193-212.

  4. Eclogite in West Papua (Wandamen Peninsula), petrological and geochemical characterization : geodynamical implications (United States)

    de Sigoyer, Julia; Pubellier, Manuel; Bailly, Vivien; Ringenbach, Jean-Claude


    The Lengguru accretionary wedge (West Papua) is located in a very active geodynamical context. It results from the oblique convergence between the Pacific plate and the Australian plate. All the wedge has been build between 11 and 2 Ma (Bailly et al., 09). Exceptional boulders of fresh eclogites were discovered in the internal part of the Lengguru wedge, in the so called Wandamen peninsula. The Wandamen peninsula displays an increasing metamorphic gradient from West to East. This metamorphic peninsula may also be regarded as the continuation of the inner part of the Central range of Papua New Guinea farther east. The eclogites area embedded in metasediments that present similarities with Mesozoic and Cenozoic sediments of the Australian margin in the continuation of Lengguru wedge. According to geochemical analysis of major and traces elements on the two freshest eclogites, their protolith has a Fe-Ti gabbroic composition. The CIPW norm of these rocks suggest a protolith, with 32% of pyroxenes, 47% of anorthite, less than 3% of olivine, with 7% of ilmenite and 7% of magnetite. Major elements show a tholeiitic characters. Traces elements suggest a T MORB signature with a high content of TiO2. The eclogites are medium to coarse grained. The metamorphic paragenesis consists of clinopyroxenes, garnets, amphiboles, rutiles, quartz and accessory minerals like apatites. Clinopyroxenes with omphacitic composition (XJd: 0.3-0.4) are poecilitic, rare textures of retrogression (symplectites) are observed. Symplectites are composed by diopside or Na-Ca-Fe pyroxene XJd (0.18) and albite, locally calcic amphiboles can replace the clinopyroxene. Garnet of several millimeters (3-4 mm) result from the aggregation of smaller euhedral crystals (500-700 µm). Some of them display atoll microstructure and exhibit a core filled by omphacite, slightly green amphibole, or by quartz. They contain minute inclusions of omphacite, amphibole, apatite, quartz. Many rutiles exsolutions are

  5. Pressure, temperature, and timing of mineralization of the sedimentary rock-hosted orogenic gold deposit at Klipwal, southeastern Kaapvaal Craton, South Africa (United States)

    Chinnasamy, Sakthi Saravanan; Uken, Ron; Reinhardt, Jürgen; Selby, David; Johnson, Spencer


    Gold mineralization in the Klipwal Shear Zone (KSZ) at the Klipwal Gold Mine is confined to laminated quartz-carbonate lodes, stringers, and associated alteration in sandstone and siltstone of the Delfkom Formation in the upper Mozaan Group of the Mesoarchaean Pongola Supergroup. The moderately dipping brittle-ductile KSZ strikes N-S with an oblique-reverse, sinistral sense of shear. The deformational events that are recognized include an early compressional phase that produced anastomosing shears defined by shear fabrics with numerous shear-parallel laminated quartz-carbonate fault-fill veins and, in places, extensional quartz vein stockworks, and a late brittle reactivation phase that produced fault breccias, displacing earlier extensional veins. Three closely spaced economic reefs (lodes) are developed: the main R-reef constitutes the KSZ, while the J- and H-reefs represent footwall splays. Alteration comprises chlorite, muscovite, epidote, feldspar, and carbonates along with pyrite, arsenopyrite, and chalcopyrite ± pyrrhotite. An inner alteration zone is dominated by laminated quartz-carbonate veins with alternating quartz-carbonate-rich and muscovite-chlorite-rich laminae, whereas the proximal zone is characterized by alteration halos of K-feldspar, albite, epidote, chlorite, and muscovite along with carbonates and associated quartz veins. Chlorite thermometry from the inner and proximal zones yielded temperatures of 267 to 312 °C. Arsenopyrite compositions provide temperatures in the same range, 255 to 318 °C. Fluid inclusion microthermometry and Raman spectrometry of quartz veins in the mineralized reefs reveal the presence of metamorphogenic aqueous-gaseous fluid with an average salinity of 6.5 wt% NaCl equiv. Fluid compositions and estimated pressure-temperature (P-T) range (1.1 to 2.5 kbar at 255 to 318 °C) are typical of orogenic gold deposits. Devolatilization during the regional facies metamorphism of the Pongola Supergroup is considered the likely

  6. Transmission Electron Microscopy of Itokawa Regolith Grains (United States)

    Keller, Lindsay P.; Berger, E. L.


    Introduction: In a remarkable engineering achievement, the JAXA space agency successfully recovered the Hayabusa space-craft in June 2010, following a non-optimal encounter and sur-face sampling mission to asteroid 25143 Itokawa. These are the first direct samples ever obtained and returned from the surface of an asteroid. The Hayabusa samples thus present a special op-portunity to directly investigate the evolution of asteroidal sur-faces, from the development of the regolith to the study of the effects of space weathering. Here we report on our preliminary TEM measurements on two Itokawa samples. Methods: We were allocated particles RA-QD02-0125 and RA-QD02-0211. Both particles were embedded in low viscosity epoxy and thin sections were prepared using ultramicrotomy. High resolution images and electron diffraction data were ob-tained using a JEOL 2500SE 200 kV field-emission scanning-transmission electron microscope. Quantitative maps and anal-yses were obtained using a Th