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Sample records for biotite

  1. Factors Influencing Biotite Weathering

    OpenAIRE

    Reed, Ryan R.

    2000-01-01

    Factors Influencing Biotite Weathering by Ryan Reed Lucian W. Zelazny, Chairman Crop and Soil Environmental Sciences (ABSTRACT) Weathering of biotite supplies nutrients such as K+ and weathers into vermiculite/montmorillonite or kaolinite, which have varying influences on soil properties and characteristics. This study was conducted to determine if the weathering mechanisms of biotite are controlled by temperature, or if other factors, such as vegetation or leaching inten...

  2. Sorption of Cs to biotite

    International Nuclear Information System (INIS)

    Full text of publication follows: Biotite is the dominant mineral that sorbs Cs in granitic bedrock. Experiments were performed on biotites separated from drill core material from Olkiluoto site. The biotites were characterised for grain size, surface area (BET), element composition (EDX micro-analyser) and mineral purity (XRD, point counting). Cation exchange capacities were determined using standard methods (AgTU, NH4Ac) and sorption capacities for Ca, Na and Cs using radioactive tracers. The sorption processes of Cs was studied in simple electrolyte solutions and groundwater simulants. Experiments with simple electrolyte solutions and groundwater simulants were performed to determine the mass balance of Cs sorption. Selectivity coefficients of sorption were calculated. The minerals were examined with SEM after the sorption experiments, and with XRD for possible changes in the lattice where applicable. Phreeqc is used for mechanistic modeling of batch experiments in groundwater simulants and for simulating of flow experiments. The data from batch experiments is verified for flow conditions in crushed mineral column experiments and the need for scaling of sorption data to fracture flow conditions is studied. Particle sizes of the biotites are 2/g. Mineral purity is > 90 %, the only major impurity is chlorite. Cation exchange capacities of the biotites are 0.013 meq/g to 0.018 meq/g. Cs sorption capacity in fresh groundwater simulant is equal to CEC, but in saline groundwaters the capacity is 1/3 of CEC. The major cation competing with Cs is K, but Na and Ca have to be taken account of when modeling the groundwater chemistry due to their high concentrations in the relevant groundwaters. (authors)

  3. Rare earth element patterns in biotite, muscovite, and tourmaline minerals

    International Nuclear Information System (INIS)

    Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10-4 g/g to 10010 g/g/. The Ree patterns of biotite, muscovite and tourmaline reported herin are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite mel/fluid system during crystallization. (author)

  4. Rare earth element patterns in biotite, muscovite and tourmaline minerals

    International Nuclear Information System (INIS)

    Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10-4 g/g to 10/sup -10g//sub g/. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigenous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization

  5. Biotite weathering in a natural forest setting near Derome, Sweden

    Science.gov (United States)

    Balogh-Brunstad, Z.; Negrich, K.; Hassenkam, T.; Wallander, H.; Stipp, S. L.

    2011-12-01

    Chemical weathering is a key process in non-nitrogen nutrient acquisition by microbes, fungi and plants. Biotite is commonly the major source of potassium, magnesium and iron. A unique opportunity arose to study natural weathering of biotite by mixed conifer and hardwood forest vegetation and associated microbes and fungi at an abandoned mine site. After the mining stopped over 30 years ago biotite was left behind in piles and the forest vegetation progressively colonized the site. Samples were collected from the top 40 cm of the biotite piles in a vicinity of pine, spruce and birch trees and included some young seedlings. Macroscopic observations documented abundant hyphal growth between the sheets of biotite. We hypothesized that fungal hyphae grow between the sheets to explore the nutrient source and weather the biotite leaving hyphal-sized etched channels on the basal surfaces. Biotite surfaces were examined with atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) in their natural state and after removing the biological material from the mineral surfaces. The ESEM images show extensive hyphal colonization and patchy biofilm cover of the entire biotite surface on and within the sheets and at the edges of the particles. Fungal hyphae did not attach strongly to the basal surfaces of the biotite flakes as a result of small particles on the surfaces and the uneven micro-topography. The AFM images illustrate a complex microbial community around the fungal hyphae and detailed fungal morphology. High resolution AFM images show unique globular features of diameter 10-100 nm on all biofilm surfaces. However, removal of the biological material resulted in smooth and un-etched surfaces indicating that either our removal techniques are too invasive and destroy the surface layers of interest, or the etching of the basal surface is not the main mechanism for chemical weathering and base-cation nutrient immobilization in this natural setting

  6. Rare earth element patterns in biotite muscovite and tourmaline minerals

    International Nuclear Information System (INIS)

    Rare earth element (REE) concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite were measured by instrumental NAA and comprehensive NAA. The concentrations range from 10-4 g/g to 10-10 g/g. The REE patterns of biotite, muscovite and tourmaline reported herein are highly fractionated from light to heavy REE. The REE concentrations in biotite and muscovite are high and indigeneous. The pegmatite tourmalines contain low concentrations of REE. Variations in tourmaline REE patterns reflect the geochemical evolution of pegmatite melt/fluid system during crystallization. (author) 10 refs.; 4 figs.; 3 tables

  7. Microbial Lithotrophic Oxidation of Structural Fe(II) in Biotite

    Energy Technology Data Exchange (ETDEWEB)

    Shelobolina, Evgenya S.; Xu, Huifang; Konishi, Hiromi; Kukkadapu, Ravi K.; Wu, Tao; Blothe, Marco; Roden, Eric E.

    2012-06-08

    Microorganisms are known to participate in the weathering of primary phyllosilicate minerals through production of organic ligands and acids, and through uptake of products of weathering. Here we show that a lithotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture (Straub, 6 1996) can grow via oxidation of structural Fe(II) in biotite, a Fe(II)-rich trioctahedral mica found in granitic rocks. Oxidation of silt/clay sized biotite particles was detected by a decrease in extractable Fe(II) content and simultaneous nitrate reduction. Moessbauer spectroscopy confirmed structural Fe(II) oxidation. Approximately 107 cells were produced per {micro}mol Fe(II) oxidized, in agreement with previous estimates of the growth yield of lithoautotrophic circumneutral-pH Fe(II)-oxidizing bacteria. Microbial oxidation of structural Fe(II) resulted in biotite alterations similar to those found in nature, including decrease in unit cell b-dimension toward dioctahedral levels and iron and potassium release. The demonstration of microbial oxidation of structural Fe(II) suggests that microorganisms may be directly responsible for the initial step in the weathering of biotite in granitic aquifers and the plant rhizosphere.

  8. Effect of neutron and proton radiations on magnetization of biotite

    CERN Document Server

    Abdurakhimov, A U; Sharipov, S M; Yugaj, V P; Granovskij, A B; Radkovskaya, A A

    2002-01-01

    One analyzes curves of field dependence of magnetization of biotite measured in the initial state under 4.2 K temperature subsequent to irradiation of 14 MeV energy and 1.2 x 10 sup 1 sup 3 cm sup - sup 2 dose neutrons and by 3 MeV energy and 2.2 x 10 sup 1 sup 4 cm sup - sup 2 dose protons, as well as, subsequent to annealing under 1000 deg temperature during 15 min. Irradiation by neutrons and protons was determined to result in increase of magneto-ordered phase content in biotite and, thus, in increase of magnetization of specimen. It is accounted for by formation of oxides in melt radiation thermal peaks and by freezing of high-temperature phase states corresponding to magnetite or solid solution of magnetite and hematite there. Thermal treatment does not change content of magneto-ordered phase in specimens

  9. Microbial lithotrophic oxidation of structural Fe(II) in biotite.

    Science.gov (United States)

    Shelobolina, Evgenya; Xu, Huifang; Konishi, Hiromi; Kukkadapu, Ravi; Wu, Tao; Blöthe, Marco; Roden, Eric

    2012-08-01

    Microorganisms are known to participate in the weathering of primary phyllosilicate minerals through the production of organic ligands and acids and through the uptake of products of weathering. Here we show that the lithotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture described by Straub et al. (K. L. Straub, M. Benz, B. Schink, and F. Widdel, Appl. Environ. Microbiol. 62:1458-1460, 1996) can grow via oxidation of structural Fe(II) in biotite, a Fe(II)-rich trioctahedral mica found in granitic rocks. Oxidation of silt/clay-sized biotite particles was detected by a decrease in extractable Fe(II) content and simultaneous nitrate reduction. Mössbauer spectroscopy confirmed structural Fe(II) oxidation. Approximately 1.5 × 10(7) cells were produced per μmol of Fe(II) oxidized, in agreement with previous estimates of the growth yield of lithoautotrophic circumneutral-pH Fe(II)-oxidizing bacteria. Microbial oxidation of structural Fe(II) resulted in biotite alterations similar to those found in nature, including a decrease in the unit cell b dimension toward dioctahedral levels and Fe and K release. Structural Fe(II) oxidation may involve either direct enzymatic oxidation, followed by solid-state mineral transformation, or indirect oxidation as a result of the formation of aqueous Fe, followed by electron transfer from Fe(II) in the mineral to Fe(III) in solution. Although it is not possible to distinguish between these two mechanisms with available data, the complete absence of aqueous Fe in oxidation experiments favors the former alternative. The demonstration of microbial oxidation of structural Fe(II) suggests that microorganisms are directly responsible for the initial step in the weathering of biotite in granitic aquifers and the plant rhizosphere. PMID:22685132

  10. Microbial Lithotrophic Oxidation of Structural Fe(II) in Biotite

    OpenAIRE

    Shelobolina, Evgenya; Xu, Huifang; Konishi, Hiromi; Kukkadapu, Ravi; Wu, Tao; Blöthe, Marco; Roden, Eric

    2012-01-01

    Microorganisms are known to participate in the weathering of primary phyllosilicate minerals through the production of organic ligands and acids and through the uptake of products of weathering. Here we show that the lithotrophic Fe(II)-oxidizing, nitrate-reducing enrichment culture described by Straub et al. (K. L. Straub, M. Benz, B. Schink, and F. Widdel, Appl. Environ. Microbiol. 62:1458–1460, 1996) can grow via oxidation of structural Fe(II) in biotite, a Fe(II)-rich trioctahedral mica f...

  11. Biotite dissolution and oxygen consumption in aqueous media at 100 degrees C

    International Nuclear Information System (INIS)

    The ability of biotite to consume dissolved oxygen, and hence restore reducing conditions in a nuclear fuel waste vault after closure, has been assessed experimentally. Oxygen consumption has been measured directly, and also deduced from experimental biotite dissolution rates. Results from the dissolution experiments on granitic biotite from the Lac du Bonnet region, Manitoba indicate that the biotite component of granite backfill should consume entrained oxygen in about 50 years at 100 degrees C. Direct measurements of oxygen consumption by commercial biotite specimens originating from Bancroft, Ontario were reasonably consistent with this finding. Magnetite is significantly more effective than biotite at oxygen consumption, perhaps two orders of magnitude faster at 100 degrees C. (author)

  12. 9519 biotite granodiorite reacted in a temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Charles, R.W.; Bayhurst, G.K.

    1980-10-01

    A biotite granodiorite from the Fenton Hill Hot Dry Rock (HDR) geothermal system was reacted in a controlled temperature gradient with initially distilled water for 60d. Polished rock prisms were located in the gradient at 72, 119, 161, 209, 270, and 310/sup 0/C. Scanning electron microscope and microprobe analyses show the appearance of secondary phases: Ca-montmorillonite at 72/sup 0/C and 119/sup 0/C; zeolite, either stilbite or heulandite, at 161/sup 0/C; and another zeolite, thomsonite, at higher temperatures. Solution analyses show a steady state equilibrium exists between solution and overgrowths after about 2 weeks of reaction. The chemographic relations for the system are explored in some detail indicating the divariant assemblages may be placed in a reasonable sequence in intensive variable space. These relations predict high and low temperature effects not directly observed experimentally as well as relevant univariant equilibria. Solution chemistry indicates the Na-Ca-K geothermometer more adequately predicts temperature in this system than does the silica geothermometer.

  13. Implications of micro-compositions of garnet and biotite from high-grade meta-pelites

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on detailed studies on the compositional zoning of garnet and biotite in pelitic rocks from the Jingshan group of granulite facies in north Jiaodong, P-T pseudosections with isopleths of Fe/(Fe + Ms) in garnet and biotite were calculated in the KFMASH system for two representative rocks of sillimanite-garnet-cordierite-biotite gneiss (Vbi/Vs > 1 ) and sillimanite-garnet gneiss ( Vbi/Vg< 0.2) using the software THERMOCALC and the internally consistent thermodynamic dataset. With a comparison of the calculated Fe/(Fe + Mg) values in garnet and biotite in the peak P-T fields constrained by peak mineral assemblages with the measured ones,it is concluded that the coarse garnet crystals with diffusion zoning from high grade meta-pelites can preserve their peak compositions even when they have experienced a cooling event, and that biotite crystals surrounded by felsic minerals in biotite-rich rocks with Vbi/Vs> 1 can nearly preserve their peak compositions, and biotites in garnet-rich rocks with Vbi/Vg< 0.2 cannot preserve their peak compositions due to the influence of grain-boundary fluid.

  14. Biotite weathering in podzolic soil under conditions of a model field experiment

    Science.gov (United States)

    Sokolova, T. A.; Tolpeshta, I. I.; Topunova, I. V.

    2010-10-01

    The biotite changes in the 1-5 μm fraction after its occurrence in the F, H, AE, and E horizons of a pale-podzolic soil for five years under conditions of a model field experiment were assessed by X-ray diffraction analysis. It was found that the main changes of the biotite in all the horizons included the degradational transformation of its crystal lattice to interstratified mica-vermiculite structures and vermiculite. The intensity of this process gradually decreased from the F horizon down the profile in parallel with the decrease in the amount of roots and the abundance and activity of microbiota. Chloritized structures were present among the products of the biotite weathering in the H, AE, and E horizons; the degree of chloritization gradually increased from the H horizon to the E horizon. The main identified products of the biotite weathering in the AE and E horizons formed during the 5 years of the model experiment were identified in the clay and fine-silt fractions from these horizons of the native pale-podzolic soils. Therefore, the vermiculite, soil chlorite, and mixed-layer illite-vermiculite minerals in the soils studied could be considered as products of the recent soil functioning. The obtained results and literature data showed that the weathering of biotite resulted in the formation of K- and Al-buffer systems.

  15. Rb-Sr ages of the biotite and muscovite of the Himalayas, eastern Nepal

    International Nuclear Information System (INIS)

    Rb-Sr ages of biotite from the southern flank of Mt. Everest, eastern Nepal, range from 14.1 to 1.3 m.y., the youngest biotite coexists with muscovite of 7.3 m.y. These different ages for different samples reflect the difference in cooling history related to the uplift of the Himalayas. The biotite ages decrease with increasing distance from the high mountain range, suggesting that the high range, i.e., the northern area, was uplifted earlier than the southern area. The relationship between the ages and altitutes of sampling sites indicates that the uplift rate of the northern area was 0.60 mm/yr. (author)

  16. Radiometric dating of brannerite and biotite minerals from Ladi-ka-bas, Sikar District, Rajasthan

    International Nuclear Information System (INIS)

    In this paper results of radiometric dating on brannerite and biotite minerals from Ladi-ka-bas area are reported. The area falls in the North Delhi Fold Belt of Rajasthan where occurrences of uranium mineralized rocks have been reported from a number of places. In Ladi-ka-bas area hydrothermal uranium mineralization is hosted within quartz-biotite schist, albitite, impure quartzite and carbonate rocks of the Mesoproterozoic Ajabgarh Group of Delhi Supergroup. The Branerite is the main uranium bearing phase in these mineralized rocks. The age data obtained in this study will be useful in understanding the uranium mineralization events in this very important region.

  17. Biotite weathering and nutrient uptake by ectomycorrhizal fungus, Suillus tomentosus, in liquid-culture experiments

    Science.gov (United States)

    Balogh-Brunstad, Zsuzsanna; Kent Keller, C.; Thomas Dickinson, J.; Stevens, Forrest; Li, C. Y.; Bormann, Bernard T.

    2008-06-01

    Ectomycorrhiza-forming fungi (EMF) alter the nutrient-acquisition capabilities of vascular plants, and may play an important role in mineral weathering and the partitioning of products of weathering in soils under nutrient-limited conditions. In this study, we isolated the weathering function of Suillus tomentosus in liquid-cultures with biotite micas incubated at room temperature. We hypothesized that the fungus would accelerate weathering by hyphal attachment to biotite surfaces and transmission of nutrient cations via direct exchange into the fungal biomass. We combined a mass-balance approach with scanning electron microscopy (SEM) and atomic force microscopy (AFM) to estimate weathering rates and study dissolution features on biotite surfaces. Weathering of biotite flakes was about 2-3 orders of magnitude faster in shaken liquid-cultures with fungus compared to shaken controls without fungus, but with added inorganic acids. Adding fungus in nonshaken cultures caused a higher dissolution rate than in inorganic pH controls without fungus, but it was not significantly faster than organic pH controls without fungus. The K +, Mg 2+ and Fe 2+ from biotite were preferentially partitioned into fungal biomass in the shaken cultures, while in the nonshaken cultures, K + and Mg 2+ was lost from biomass and Fe 2+ bioaccumulated much less. Fungal hyphae attached to biotite surfaces, but no significant surface changes were detected by SEM. When cultures were shaken, the AFM images of basal planes appeared to be rougher and had abundant dissolution channels, but such channel development was minor in nonshaken conditions. Even under shaken conditions the channels only accounted for only 1/100 of the total dissolution rate of 2.7 × 10 -10 mol of biotite m -2 s -1. The results suggest that fungal weathering predominantly occurred not by attachment and direct transfer of nutrients via hyphae, but because of the acidification of the bulk liquid by organic acids, fungal

  18. Biotite dissolution and Cr(VI) reduction at elevated pH and ionic strength

    Science.gov (United States)

    He, Y. Thomas; Bigham, Jerry M.; Traina, Samuel J.

    2005-08-01

    The effects of elevated pH, ionic strength, and temperature on sediments in the vadose zone are of primary importance in modeling contaminant transport and understanding the environmental impact of tank leakage at nuclear waste storage facilities like those of the Hanford site. This study was designed to investigate biotite dissolution under simulated high level waste (HLW) conditions and its impact on Cr(VI) reduction and immobilization. Biotite dissolution increased with NaOH concentrations in the range of 0.1 to 2 mol L -1. There was a corresponding release of K, Fe, Si, and Al to solution, with Si and Al showing a complex pattern due to the formation of secondary zeolite minerals. Dissolved Fe concentrations were an order of magnitude lower than the other elements, possibly due to the formation of green rust and Fe(OH) 2. The reduction of Cr(VI) to Cr(III) also increased with increased NaOH concentration. A homogeneous reduction of chromate by Fe(II) aq released through biotite dissolution was probably the primary pathway responsible for this reaction. Greater ionic strengths increased biotite dissolution and consequently increased Fe(II) aq release and Cr(VI) removal. The results indicated that HLW would cause phyllosilicate dissolution and the formation of secondary precipitates that would have a major impact on radionuclide and contaminant transport in the vadose zone at the Hanford site.

  19. Extraction of potassium from biotite by Ba2+/K+ ion exchange and the structural transformation

    Science.gov (United States)

    Meng, Peng; Li, Ziqian; Huang, Zhiliang; Chen, Changlian

    2016-03-01

    Potassium has been extracted successfully from biotite by Ba2+/K+ ion exchange. The potassium release rate increased along S-curve versus reaction time. The maximum of potassium release rate was about 96 %. Powder X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy were used to characterize the obtained samples to reveal the exchanging behavior and structural transformation. The results showed that after treated with Ba(NO3)2 four times the original biotite transformed to vermiculite-type hydrated Ba-mica. The (001) basal plane was expanded from 1.000 nm of biotite to 1.221 nm of hydrated Ba-mica. Because of the "vacancy effect," the Ba2+ has two different statuses, causing the structural water vibration of vermiculite-type hydrated Ba-mica split. The edge of vermiculite-type hydrated Ba-mica was crimped compared with the flat edge of original biotite. The (001) basal plane of dehydrated Ba-mica was also split, supporting the "vacancy effect."

  20. Diffusion of 40Ar in biotite: temperature, pressure and compositional effects

    International Nuclear Information System (INIS)

    The measured radiogenic 40Ar loss from sized biotite samples following isothermal-hydrothermal treatment have provided model diffusion coefficients in the temperature interval 600 C to 750 C, calculated on the assumption that Ar transport proceeds parallel to cleavage. These data yield an array on an Arrhenius plot with a slope corresponding to an activation energy 47.0 +- 2 kcal-mol-1 and a frequency factor of 0.077sub(-0.06)sup(+0.21) cm2-sec-1. Together with previous diffusion data for micas in the annite-phlogopite series, our results indicate a strong compositional effect, with increasing Fe/Mg ratio corresponding to an increase in diffusivity. An effective diffusion radius of about 150 μm for biotite is inferred from the experimental data which compares favorably with that estimated from geological studies. A pressure effect on activation energy corresponding to an activation volume of about 14 cm3-mol-1 is observed. These data yield closure temperature estimates for this biotite composition cooling at rates of 100 C-Ma-1, 10 C-Ma-1 and 1 C-Ma-1 of 345 C, 310 C and 280 C, respectively. 40Ar/39Ar age-spectrum analysis of a hydrothermally treated biotite yields a complex release pattern casting doubt on the general usefulness of such measurements for geochronological purposes. (author)

  1. Effects of citrate on the dissolution and transformation of biotite, analyzed by chemical and atomic force microscopy

    International Nuclear Information System (INIS)

    Highlights: • Protons have a dominant role in the dissolution process of biotite (0 0 1) surface. • Organic (carboxyl) acts as a catalyst under weakly acidic soil condition. • Biotite dissolution starts from defect sites and develops along [h k 0] direction. • Secondary coating on (0 0 1) surface would hinder the etch pits formation. - Abstract: The aim of this study was to investigate the dissolution and transformation characteristics of phyllosilicate under low molecular weight organic acids in the farmland environment (pH 4.0–8.0). Changes of dissolution and morphology of biotite were evaluated using chemical extraction experiments and in situ/ex situ atomic force microscopy (AFM) with fluids of citric acid (CA) solution at pH 4.0, 6.0, and 8.0. Results of extracting experiments show that CA solutions contributed to the release rate of potassium (K), silicon (Si), and aluminum (Al) from biotite relative to a control aqueous solution. In situ AFM observations indicate that the dissolution of biotite from the biotite (0 0 1) surface occurred on the terrace, segment, and fringe of pits, while new etch pits did not readily form on biotite (0 0 1) surfaces in aqueous solutions. However, dissolution rates of terraces can be greatly accelerated with the help of citrate. In pH 4.0 CA solution, 70 min dissolution reactions of biotite (0 0 1) surfaces result in more etch pits than in pH 6.0 and 8.0 solutions. In addition, the transformation of biotite occurred simultaneously with the dissolution process. Secondary coating was observed on the biotite (0 0 1) surface after 140 h of immersion in a weak acid environment. Thus, the protons have a dominant role in the dissolution process of biotite with organic (carboxyl) acting as a catalyst under acidic condition. Based on the theory of interactions on a water–mineral interface in a weak acid environment, dissolution of biotite starts from defect/kink sites on the surface, one layer by one layer, and develops

  2. Pure strontium-87 isotope in rubidium biotite from the Ukrainian shield

    International Nuclear Information System (INIS)

    In lithium pegmatites of Shpoljano-Tashlyksky ore area (Kirovograd block of the Ukrainian shield) the biotites enriched with rubidium are distinguished. X-ray and electron-microprobe study of these minerals has shown that they attributed to low ferruginous biotites of structural modification 1M. By nuclear-physics methods the concentration of rubidium, 87Rb and 87Sr were defined. By X-ray-fluorescent method Sr/Rb-ratio was defined. From these data the cleanliness 87Sr s%=87Sr/Srtot x 100=96+4-6% received. The natural isotopic abundance of 87Sr is 7%. Rb/Sr age of the mineral is estimated as 2.14 billion years that will be coordinated with earlier results.

  3. Determination of Bacterial Weathering Ability in Nutrient Limited Conditions on Biotite

    Science.gov (United States)

    Grant, M. R.; Harsh, J. B.

    2011-12-01

    Bacterial and fungal communities facilitate the weathering of minerals in oligotrophic soils. The bacterial communities reside in biofilms, consisting of extracellular polymeric substances (EPS) such as lipids, carbohydrates, proteins, and nuclei acids. Biotite, a 2:1 aluminosilicate mica, is a common primary mineral found in these low nutrient soils and is a source of potassium, magnesium and iron for both microorganisms and plants. Studies show that bacteria, when incubated with biotite flakes, can remove iron, potassium, and magnesium at higher quantities and increased rates compared to abiotic controls (Balogh-Brunstad et al., 2008; Calvaruso et al., 2006; Hopf et al. 2008; Uroz et al., 2007 and 2009). How this happens mechanistically is still unclear and this study seeks to shed light on this issue. We hypothesize that weathering by bacteria is selective; i.e., that the mechanism will depend on the limiting nutrient. Using a drip flow biofilm reactor, biofilms are grown on biotite coupons under non-turbulent, low sheer flow, with four different nutrient treatments. The nutrient treatments include a complete nutrient solution and the same solution without K, Mg, or Fe. In each treatment, we determine the concentration and cumulative release of each cation in the effluent. Congruent dissolution of biotite indicates that weathering is nonselective whereas incongruent dissolution suggests that the bacteria alter the weathering mechanism for a specific nutrient. The bacteria are selected from a bacterial inoculum collected from the roots of young White Pine (Pinus strobus) trees in the Saint Joseph National Forest, Idaho. The bacteria are isolated on plates and the best weathering species are selected using a microplate bioassay technique to determine the concentrations of K, Ca, Mg, and protons colorimetrically.

  4. Distribution of manganese between coexisting biotite and hornblende in plutonic rocks

    Science.gov (United States)

    Greenland, L.P.; Gottfried, D.; Tilling, R.I.

    1968-01-01

    The distribution of manganese between coexisting biotite and hornblende for 80 mineral pairs from igneous rocks of diverse provenance (including Southern California, Sierra Nevada, Boulder, and Boulder Creek batholiths and the Jemez Mountains volcanics) has been determined by neutron activation analysis. Data on the distribution ratio (Kd = Mnhornblende Mnbiotite) indicate that an equilibrium distribution of Mn is closely approached, though not completely attained, in most samples from plutonic environments. Comparison of Kd values of mineral pairs with bulk chemical composition of host rocks reveals no correlation. Because initial crystallization temperatures vary with rock composition, the lack of correlation of composition with Kd suggests that the equilibrium distribution of Mn between biotite and hornblende reflects exchange at subsolidus temperatures rather than initial crystallization temperatures. The highest Kd values are for volcanic rocks, in which rapid quenching prevents subsolidus redistribution of Mn. For sample pairs from the Southern California and Sierra Nevada batholiths there is a positive correlation of Kd with TiO2 content of biotite. Though the evidence is not compelling, Kd may also correlate with the rate of cooling and/or the presence or absence of sphene in the rock. ?? 1968.

  5. Modeling of cesium sorption on biotite using cation exchange selectivity coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Kylloenen, Jarkko; Hakanen, Martti; Harjula, Risto; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry; Lindberg, Antero [Geological Survey of Finland, Espoo (Finland); Vehkamaeki, Marko [Helsinki Univ. (Finland). Lab. of Inorganic Chemistry

    2014-07-01

    For the modeling of cesium sorption on biotite, samples of natural biotite separated from gneissic rocks were converted into monoionic potassium, sodium, and calcium forms, and sorption isotherms for Cs/K, Cs/Na and Cs/Ca exchange were determined at pH 6 and 8 in 10{sup -4}-10{sup -8} M Cs solutions. Selectivity coefficients for Cs/K, Cs/Na, and Cs/Ca ion exchange reactions were calculated from the isotherm data, using the Gaines-Thomas convention. At Cs loadings below 1% of the total ion exchange capacity, the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange, respectively. Based on the selectivity coefficients, the ion exchange isotherms were modeled with the U.S. Geological Survey PhreeqC program, assuming three different types of ion exchange site: sites on the basal planes on biotite crystal surfaces with 95% site abundance, probable interlayer sites on crystal edges [frayed edge sites (FESs)] (0.02%) and third-type sites (5%), the physical background of which is unclear. Of these three types, the FES sites were superior in Cs selectivity, while the planar sites exhibited the lowest selectivity, and the third-type sites had selectivity between these two. The functionality of the model was successfully verified by modeling the Cs sorption isotherms on crushed mica gneiss rock in saline groundwater. Determination of the exchangeable ions K, Na, Ca, and Cs on the basal plane and edge surfaces by scanning electron microscopy-energy-dispersive x-ray spectroscopy (SEM-EDX) supports the results of modeling: edge sites highly prefer Cs ions and also Ca and Na ions but not K ions.

  6. Modeling and Measurement of 39Ar Recoil Loss From Biotite as a Function of Grain Dimensions

    Science.gov (United States)

    Paine, J. H.; Nomade, S.; Renne, P. R.

    2004-12-01

    The call for age measurements with less than 1 per mil error puts a demand upon geochronologists to be aware of and quantify a number of problems which were previously negligible. One such factor is 39Ar recoil loss during sample irradiation, a phenomenon which is widely assumed to affect only unusually small crystals having exceptionally high surface/volume ratios. This phenomenon has important implications for thermochronologic studies seeking to exploit a range of closure temperatures arising from variable diffusion radii. Our study focuses on biotite, in which spatial isotope distributions cannot be reliably recovered by stepwise heating and which therefore lack recoil-diagnostic age spectrum behavior. Previous work by Renne et al. [Application of a deuteron-deuteron (D-D) neutron generator to 40Ar/39Ar geochronology, Applied Radiation and Isotopes, in press] used the SRIM code to calculate a ˜20% 39Ar recoil loss from the outermost 0.25 μ m of an infinite slab of phyllosillicate. This result is applied to measured grains of the biotite standard GA1550, a hypabyssal granite from the Mount Dromedary Complex, Australia. We measure the thickness and surface area of 166 grains and approximate the shape of each grain as a cylinder. Grain thickness ranges from 3 to 210 μ m, with an average grain radius of 350 μ m. We predict the amount of 39Ar recoil loss from each grain, finding an expected age error >0.1 % for grains thinner than 150 μ m, a >1% error for grain less than 10 μ m thick, and up to a 3% error for grains less than 3 μ m thick. These modeling results will be tested by analysis of the measured grains after irradiation in the Oregon State University TRIGA reactor. It is important to either account for 39Ar loss in thin biotite grains, or use sufficiently thick ones so that recoil loss is negligible. Our results indicate that only biotite grains thicker than 150 μ m should be used for neutron fluence monitoring in order to avoid bias greater than the

  7. The dissolution of biotite and chlorite at 25°C in the near-neutral pH region

    Science.gov (United States)

    Malmström, Maria; Banwart, Steven; Lewenhagen, Jeanette; Duro, Lara; Bruno, Jordi

    1996-02-01

    We studied the dissolution of biotite and chlorite in laboratory systems with flow-through and batch reactors. The initial dissolution of biotite in the near-neutral pH region, under N 2(g) atmosphere is highly non-stoichiometric. A slow linear release of iron during a period of weeks indicates a surface-chemical-reaction-controlled mechanism of release for iron. The release of potassium is much faster than that of iron. A parabolic dependence of accumulated release with time suggests a diffusion-controlled mechanism of potassium release. The rates of magnesium, aluminium and silicon release are between those for potassium and iron and approach that of iron with time. There is no significant influence of (bi)carbonate or pH on biotite dissolution rate or stoichiometry in the pH region 7 < pH < 8.5. The release rates of elements from chlorite are close to stoichiometric and similar to the iron release rate from biotite. In closed batch reactors at near-basic pH the composition of test solutions in contact with biotite is apparently controlled by gibbsite (Al), kaolinite (Si) and Fe(III)-(hydr)oxide. We estimated a turn-over time (10 1-10 2 yr) for molecular oxygen and a time scale (10 months) to develop characteristic Fe(II) concentrations for a granitic groundwater.

  8. Biofilm Formation and Adaptation by Pseudomonas fluorescens on both Biotite and Glass Coupons Under Varying Fe-Nutrient Availability

    Science.gov (United States)

    Grant, M.; Helms, G. L.; Shi, Z.; Thomashow, L.; Keller, C. K.; Harsh, J. B.

    2014-12-01

    We isolated an efficient weathering strain of Pseudomonas fluorescens from the rhizosphere of a White Pine (Pinus strobus) seedling. We grew it in a drip-flow biofilm reactor using both Fe-abundant and Fe-deficient media on either a glass or biotite coupon. Our working hypothesis was that the bacterium would respond to Fe deficiency by enhancing biotite weathering through an increase in the relative amount of polysaccharides in the biofilm compared to the Fe-abundant treatment. Because Fe is necessary for biofilm development, we hypothesized that biomass production on the biotite surface would exceed that on a Fe-free glass slide only in the Fe-deficient medium. We quantified total biomass, specific number of viable cells (SNVC), and the concentrations of K, Mg, and Fe in the biofilm. High-resolution magic angle spinning proton nuclear magnetic resonance (HR-MAS 1H-NMR) spectroscopy was used to characterize the biofilm matrix in terms of relative biofilm constituent concentrations. Compared with biofilms grown on glass, biofilms grown on biotite had higher total biomass and SNVC irrespective of Fe supply, with a near doubling of both the biofilm biomass from 0.43 to 0.76 mg cm-2 and SNVC from 1.52 × 107 to 3.24 × 107 CFU cm-2 mg-1 when Fe was deficient, and an increase in biomass from 1.94 to 2.46 mg cm-2 and in SNVC from 8.39 × 107 to 1.96 × 108 CFU cm-2 mg-1 when Fe was sufficient. Similarly with Fe deficient, the cation concentrations in biofilms grown on biotite vs. glass increased 2.14 and 2.46 times for K and Mg, respectively, and 7.01 times for Fe. When Fe was sufficient, the concentrations of cations increased 1.24, 2.07, and 3.77 times for K, Mg, and Fe, respectively. Based on NMR spectra, no significant change in biofilm chemistry occurred between the glass and biotite systems whether Fe was deficient or not. However, we did observe an increase in the ratio of the integrated areas corresponding to the carbohydrate and protein NMR regions, increasing

  9. Scales of equilibrium and disequilibrium during cleavage formation in chlorite and biotite-grade phyllites, SE Vermont

    Science.gov (United States)

    McWilliams, C.K.; Wintsch, R.P.; Kunk, M.J.

    2007-01-01

    Detailed electron microprobe analyses of phyllosilicates in crenulated phyllites from south-eastern Vermont show that grain-scale zoning is common, and sympathetic zoning in adjacent minerals is nearly universal. We interpret this to reflect a pressure-solution mechanism for cleavage development, where precipitation from a very small fluid reservoir fractionated that fluid. Multiple analyses along single muscovite, biotite and chlorite grains (30-200 ??m in length) show zoning patterns indicating Tschermakitic substitutions in muscovite and both Tschermakitic and di/trioctahedral substitutions in biotite and chlorite. Using cross-cutting relationships and mineral chemistry it is shown that these patterns persist in cleavages produced at metamorphic conditions of chlorite-grade, chlorite-grade overprinted by biotite-grade and biotite-grade. Zoning patterns are comparable in all three settings, requiring a similar cleavage-forming mechanism independent of metamorphic grade. Moreover, the use of 40Ar/ 39Ar geochronology demonstrates this is true regardless of age. Furthermore, samples with chlorite-grade cleavages overprinted by biotite porphyroblasts suggest the closure temperatures for the diffusion of Al, Si, Mg and Fe ions are greater than the temperature of the biotite isograd (>???400 ??C). Parallel and smoothly fanning tie lines produced by coexisting muscovite-chlorite, and muscovite-biotite pairs on compositional diagrams demonstrate effectively instantaneous chemical equilibrium and probably indicate simultaneous crystallization. These results do not support theories suggesting cleavages form in fluid-dominated systems. If crenulation cleavages formed in systems in which the chemical potentials of all major components are fixed by an external reservoir, then the compositions of individual grains defining these cleavages would be uniform. On the contrary, the fine-scale chemical zoning observed probably reflects a grain-scale process consistent with a

  10. Studying the interface between cyanobacteria and biotite mineral surfaces using FIB and TEM

    International Nuclear Information System (INIS)

    Recent analysis of the bioweathering of minerals has highlighted the challenges for investigating the interface between fungi or bacteria and the surface of the mineral that they live on. Transmission electron microscopy (TEM) with its ability to gather imaging information and collect elemental data at high spatial resolution is the ideal technique to analyse such interfaces. Further to this, a dual beam scanning electron and focused ion beam (FIB) microscope is an ideal instrument to prepare specimens for TEM because of its ability to simultaneously cut through hard and soft materials from specific sites of interest. There are however precautions that must be taken when analysing such mineral systems. The electron beam sensitive nature of most sheet silicate minerals means that consideration has to be made as to whether the structure and/or chemistry of the material is being altered during (S)TEM analysis. Here, results from a study of cyanobacteria grown on the surface of biotite are discussed. Particular reference is given to the methods used to determine an electron beam intensity threshold, below which STEM-EDX analysis could be performed without detrimental alteration to the mineral

  11. Correlation between magnetic fabrics, strain and biotite microstructure with increasing mylonitisation in the pretectonic Wyangala Granite, Australia

    Science.gov (United States)

    Lennox, P. G.; de Wall, H.; Durney, D. W.

    2016-04-01

    The Wyangala Granite is a foliated, porphyritic Silurian granite from the Palaeozoic Circum-Pacific type Eastern Lachlan Orogen (ELO) of Australia. It is a paramagnetic ilmenite-bearing, S/marginal I type two-mica- to mainly biotite-granite with different biotite contents and local chlorite alteration. Very highly strained quartz-epidote bands are present. In this contribution, anisotropy of magnetic susceptibility (AMS) is compared with independently measured intensity and 3D style of strain, biotite microstructure and degree of mylonitisation for low-strain granites with weak S-foliations, through medium-strain protomylonitic granites with moderate S- and C-foliations to a high-strain altered granite with a strong single foliation. The samples are further analysed for possible contributions from sample heterogeneity, magmatic flow and 'sub-magmatic' deformation. A good correlation, P‧AMS ~ 1.02 + 0.04 ln P‧(e)Qtz, is obtained between site-average degree of AMS (P‧AMS) in the granite and degree of finite-strain anisotropy (P‧(e)Qtz) from aspect ratios of quartz aggregates in S-foliations in hand specimen and outcrop (P‧AMS 1.03-1.14, P‧(e)Qtz 1.4-19). The magnetic fabric ellipsoids agree with a kinematic regime between neutral and pure oblate predicted by the March model. The observed quartz strains, however, exceed the AMS March strains and are near neutral, plano-linear character. The geological factors that may have contributed to these differences include intra- and inter-crystalline deformation of biotite and bimodality in S and C. Magmatic fabric is not clearly evident in either the AMS or the biotite data. New data for synkinematic oligoclase, low-titanium biotite and low-sodium K-feldspar show that conditions during deformation were approximately transitional greenschist-amphibolite facies: i.e., well below solidus. This agrees with published age data that put the granite emplacement in an extensional, back-arc setting in already deformed

  12. Hydrogen isotope investigation of amphibole and biotite phenocrysts in silicic magmas erupted at Lassen Volcanic Center, California

    Science.gov (United States)

    Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

    2012-01-01

    Hydrogen isotope ratio, water content and Fe3 +/Fe2 + in coexisting amphibole and biotite phenocrysts in volcanic rocks can provide insight into shallow pre- and syn-eruptive magmatic processes such as vesiculation, and lava drainback with mixing into less devolatilized magma that erupts later in a volcanic sequence. We studied four ~ 35 ka and younger eruption sequences (i.e. Kings Creek, Lassen Peak, Chaos Crags, and 1915) at the Lassen Volcanic Center (LVC), California, where intrusion of crystal-rich silicic magma mushes by mafic magmas is inferred from the varying abundances of mafic magmatic inclusions (MMIs) in the silicic volcanic rocks. Types and relative proportions of reacted and unreacted hydrous phenocryst populations are evaluated with accompanying chemical and H isotope changes. Biotite phenocrysts were more susceptible to rehydration in older vesicular glassy volcanic rocks than coexisting amphibole phenocrysts. Biotite and magnesiohornblende phenocrysts toward the core of the Lassen Peak dome are extensively dehydroxylated and reacted from prolonged exposure to high temperature, low pressure, and higher fO2 conditions from post-emplacement cooling. In silicic volcanic rocks not affected by alteration, biotite phenocrysts are often relatively more dehydroxylated than are magnesiohornblende phenocrysts of similar size; this is likely due to the ca 10 times larger overall bulk H diffusion coefficient in biotite. A simplified model of dehydrogenation in hydrous phenocrysts above reaction closure temperature suggests that eruption and quench of magma ascended to the surface in a few hours is too short a time for substantial H loss from amphibole. In contrast, slowly ascended magma can have extremely dehydrogenated and possibly dehydrated biotite, relatively less dehydrogenated magnesiohornblende and reaction rims on both phases. Eruptive products containing the highest proportions of mottled dehydrogenated crystals could indicate that within a few days

  13. Formation and preservation of biotite-rich microdomains in high-temperature rocks from the Antananarivo Block, Madagascar

    Science.gov (United States)

    Cenki-Tok, Bénédicte; Berger, Alfons; Gueydan, Frédéric

    2016-07-01

    Highly restitic rocks from the Antananarivo Block in northern Madagascar are investigated in this study in order to unravel processes of H2O-rich biotite formation in HT rocks. Polyphase metamorphism and melt migration occurred at 0.6 GPa and 850 °C. Biotite remains stable together with orthopyroxene and makes up to 45 vol% of the rock. In addition, three well-characterised and delimited microdomains having different textural, chemical and petrological characteristics are preserved. Thermodynamic models using the specific bulk compositions of the domains are in agreement with petrological observations. These rocks provide evidence that the lower crust may be strongly heterogeneous, locally associated to the formation of hydrous restites controlled by episodes of melt production and melt escape. This has significant consequences for understanding of the lower crust.

  14. Redox Interactions of Tc(VII), U(VI), and Np(V) with Microbially Reduced Biotite and Chlorite.

    Science.gov (United States)

    Brookshaw, Diana R; Pattrick, Richard A D; Bots, Pieter; Law, Gareth T W; Lloyd, Jonathan R; Mosselmans, J Fredrick W; Vaughan, David J; Dardenne, Kathy; Morris, Katherine

    2015-11-17

    Technetium, uranium, and neptunium are contaminants that cause concern at nuclear facilities due to their long half-life, environmental mobility, and radiotoxicity. Here we investigate the impact of microbial reduction of Fe(III) in biotite and chlorite and the role that this has in enhancing mineral reactivity toward soluble TcO4(-), UO2(2+), and NpO2(+). When reacted with unaltered biotite and chlorite, significant sorption of U(VI) occurred in low carbonate (0.2 mM) buffer, while U(VI), Tc(VII), and Np(V) showed low reactivity in high carbonate (30 mM) buffer. On reaction with the microbially reduced minerals, all radionuclides were removed from solution with U(VI) reactivity influenced by carbonate. Analysis by X-ray absorption spectroscopy (XAS) confirmed reductive precipitation to poorly soluble U(IV) in low carbonate conditions and both Tc(VII) and Np(V) in high carbonate buffer were also fully reduced to poorly soluble Tc(IV) and Np(IV) phases. U(VI) reduction was inhibited under high carbonate conditions. Furthermore, EXAFS analysis suggested that in the reaction products, Tc(IV) was associated with Fe, Np(IV) formed nanoparticulate NpO2, and U(IV) formed nanoparticulate UO2 in chlorite and was associated with silica in biotite. Overall, microbial reduction of the Fe(III) associated with biotite and chlorite primed the minerals for reductive scavenging of radionuclides: this has clear implications for the fate of radionuclides in the environment. PMID:26488884

  15. Preservation of Sub-Microscopic Scale Structural Relics in Biotite: Implications for 40AR/39AR Geochronology

    Science.gov (United States)

    Beltrando, M.; Di Vincenzo, G.; Ferraris, C.

    2012-12-01

    Relic crystals of magmatic biotite that undewent eclogite facies metamorphism were investigated by laser step-heating and laser in-situ 40Ar/39Ar techniques, in conjunction with SEM, EMP and TEM analyses, to elucidate the influence of recrystallization on K-Ar systematics. Samples were collected from meta-granitoids of the Gran Paradiso Massif (Western Alps), emplaced at upper crustal depths (P~0.25-0.35 GPa) in the Permian and metamorphosed at P>2.0 GPa and T~500-600°C in the Middle-Late Eocene. Two different samples, which underwent different degrees of Alpine re-equilibration, were examined. Sample JT1007 still preserves the original cm-sized magmatic quartz, k-feldspar and brown biotite (Bt 1), rarely rimmed by small green biotite crystals (Bt 2) related to Alpine metamorphism. Sample JT1008, instead, is characterized by a larger degree of Alpine re-equilibration, with static re-crystallization of the original magmatic quartz into aggregates of fine-grained polygonal crystals and common green biotite rims around brown Bt 1. Compositional profiling across Bt 1 in sample JT1007 reveals a progressive decrease in Ti content towards the crystal rims, which overlap with the composition of Bt 2. Compositional profiling across Bt 1 in sample JT1008, instead, reveals a homogeneous Ti content across the grain. This compositional pattern is mirrored by TEM investigation at the sub-micron scale, revealing a systematic zoning in Bt 1 from sample JT1007, with high-temperature magmatic politypes, surrounded by 1M politypes, still preserved in crystal cores. Crystal rims, instead, are characterized by 1M politypes only. Biotites from JT1008, instead, are homogeneous, solely consisting of 1M politypes. Infrared laser step-heating experiments on mineral separates from the two samples gave contrasting results: JT1008 yielded a flat spectrum, for more than 90% of the released 39ArK, with an error-weighted mean age of 36.5±0.3 Ma; JT1007 yielded a slightly saddle-shaped profile

  16. Dietary germanium biotite supplementation enhances the induction of antibody responses to foot-and-mouth disease virus vaccine in pigs

    OpenAIRE

    Lee, Jin-A; Jung, Bock-Gie; Jung, Myunghwan; Kim, Tae-Hoon; Yoo, Han Sang; Lee, Bong-Joo

    2014-01-01

    We evaluated the potential ability of germanium biotite (GB) to stimulate the production of antibodies specific for foot-and-mouth disease virus (FMDV). To this aim, we measured the total FMDV-specific antibody responses and IgM production after vaccination against FMD both experimentally and in the field. GB supplementation with FMDV vaccination stimulated the production of anti-FMDV antibodies, and effectively increased IFN-γ and TNF-α levels. These results suggest that GB may be a novel al...

  17. Thermal regime in the central Alpine Fault zone, New Zealand: Constraints from microstructures, biotite chemistry and fluid inclusion data

    Science.gov (United States)

    Toy, Virginia G.; Craw, Dave; Cooper, Alan F.; Norris, Richard J.

    2010-04-01

    The thermal state within plate boundary fault zones is likely to influence the dimensions of large co-seismic fault ruptures, and strain localisation in underlying mylonitic shear zones. Vein microstructures, biotite chemistry and fluid inclusion data offer new insights into the thermal structure of the mylonitic shear zone down dip of the Alpine Fault, the main Pacific-Australian plate boundary structure through southern New Zealand. Quartz veins within the fault rocks were formed and deformed at temperatures ranging from > 500 °C to immediately above that of the brittle-viscous transition (˜ 325 °C), illustrating that fluids are present throughout the fault zone. Microthermometric data from primary, mixed CO 2-H 2O fluid inclusions in boudin-neck quartz-carbonate veins indicate that these inclusions were trapped at temperatures of 325 ± 15 °C and pressures of c. 40 MPa. Vein microstructures indicate that fluid temperatures were equal to rock temperatures. Assuming hydrostatic fluid pressure, the veins were trapped at depths of 500 kg m - 3 . Biotite grains in the mylonites are a mixture of porphyroclastic grains with high R = Ti/Mg# inherited from the parent Alpine Schist, and smaller, low R grains that recrystallised during mylonitisation, particularly those that are found within syn-mylonitic shear bands. Assuming a simple step-function model approximating diffusive equilibration, the changes in biotite chemistry indicate Δ T during mylonitic deformation of ˜-340 °C according to the Ti-in-biotite thermometer of Henry et al. (2005). A best-fit uplift P- T path to existing data and these new results indicate that the uplift path P- T gradient of fault zone rocks above the brittle-viscous transition is of the order of 40 °C km - 1 . Below the brittle-viscous transition, the uplift path P- T gradient is 10 °C km - 1 . The P- T profile within the fault rocks is comparable to that in the immediate hanging wall Alpine Schist, indicating there is no peak in

  18. The 3D distribution of cordierite and biotite in hornfels from the Bugaboo contact aureole (British Columbia, Canada)

    Science.gov (United States)

    Gaidies, Fred; Petley-Ragan, Arianne; Pattison, David

    2016-04-01

    The size, abundance, shape and spatial distribution of metamorphic minerals bears important information on the rates and mechanisms of fundamental processes that take place during metamorphic crystallization. X-ray computed tomography (XR-CT) has become the method of choice to study the three-dimensional (3D) disposition of minerals in rocks as it allows investigation of relatively large sample volumes at sufficiently high resolution required for statistically meaningful analyses, and as its non-destructive fashion permits further studies such as mineral chemical, isotopic or crystallographic analyses of select grains identified through XR-CT. We present results obtained through the quantification of the 3D disposition of cordierite and biotite crystals in a hornfels from the contact aureole of the Bugaboo Batholith (British Columbia, Canada) using XR-CT and global as well as scale-dependent pattern statistics (Petley-Ragan et al., 2016). The results demonstrate a random distribution of cordierite and biotite crystal sizes for all scales across the entire rock volume studied indicative of interface-controlled prograde metamorphic reaction kinetics. We show that the common approach to approximate the shape of crystals as spherical underestimates the influence of the Strauss hard-core process on rock texture which may be misinterpreted to reflect ordering of crystal sizes by inhibition of nucleation and growth commonly associated with diffusion-controlled reaction kinetics. According to our findings, Strauss hard-core ordering develops at length scales equal to and less than the average major axis of the crystal population. This is significantly larger than what is obtained if a spherical crystal geometry would be assumed, and increases with deviation from sphericity. For the cordierite and biotite populations investigated in this research, Strauss hard-core ordering developed at length scales of up to ˜2.2 and 1.25 mm, respectively, which is almost 1 mm longer than

  19. Equilibrium partitioning and subsequent re-distribution of halogens among apatite-biotite-amphibole assemblages from mantle-derived plutonic rocks: Complexities revealed

    Science.gov (United States)

    Teiber, Holger; Scharrer, Manuel; Marks, Michael A. W.; Arzamastsev, Andrei A.; Wenzel, Thomas; Markl, Gregor

    2015-04-01

    The concentration of halogens in apatite, biotite and amphibole is investigated for a large variety of mantle-derived plutonic rocks (gabbros, diorites, monzonites, olivine- and pyroxene-bearing monzonitic to granitic rocks, syenites, carbonatites and a phoscorite). In all rocks studied, apatite occurs as an early magmatic phase, whereas biotite and amphibole may occur either as a late magmatic phase or as late-stage, potentially hydrothermal product replacing precursor olivine, pyroxene and Fe-Ti oxides (ilmenite and magnetite). Based on electron microprobe analyses for F and Cl and detailed textural observations, we test existing models of halogen partitioning between apatite and biotite. Bromine concentration data for apatite, biotite and amphibole are used to further refine our understanding of the geochemical similarities and differences between Cl and Br during magmatic and hydrothermal processes. Our data suggests that F and Cl contents in apatite, biotite and amphibole can indeed be useful monitors of the halogen systematics in magmas, but they may also be subject to post-magmatic changes to variable extents. The relatively small radius and compatible F cation seems to be less prone to post-magmatic alteration and is likely to best reflect the original magmatic halogen abundances - especially in apatite. However, the larger and probably more incompatible Cl anion, is more easily re-mobilized as reflected by strong redistribution of Cl in biotite and amphibole which have been clearly overprinted by hydrothermal fluids. In certain cases, the ability of halogens to re-distribute themselves after magmatic equilibrium partitioning (as emphasized by our data) suggests that observed partitioning (especially between apatite and biotite) may also be used as a very sensitive indicator for post-magmatic hydrothermal processes.

  20. Molybdenite Re-Os dating of biotite dehydration melting in the Rogaland high-temperature granulites, S Norway

    Science.gov (United States)

    Bingen, Bernard; Stein, Holly

    2003-03-01

    The ability of the Re-Os system in molybdenite to record and preserve the age of granulite-facies metamorphism in polymetamorphic belts is tested using the Ørsdalen W-Mo district, Rogaland, S Norway. A low-pressure high-temperature granulite-facies domain, displaying osumilite and pigeonite isograds, is exposed around the 931±2 Ma Rogaland anorthosite complex. Available U-Pb monazite and zircon data show that a 0.93 Ga contact metamorphism overprints a 1.03-0.97 Ga regional Sveconorwegian metamorphism in the gneiss basement. Molybdenite and scheelite in the Ørsdalen district occur in orthopyroxene-bearing leucocratic veins parallel to the regional foliation. The veins are interpreted as migmatic leucosomes formed by fluid-absent incongruent melting of the biotite-rich host rock above ca. 800°C, producing a granulite-facies orthopyroxene±garnet residual assemblage. Molybdenite is interpreted as a product of the melting reaction, crystallized from trace amounts of Mo released from biotite in the host rock during partial melting. Four Re-Os analyses of molybdenite from three samples representing two mines yield an isochron age of 973±4 Ma. The isochroneity of the data indicates that the precipitation of molybdenite and the partial melting event are recorded on the district scale. The Re-Os system in molybdenite was not affected by subsequent 0.93 Ga contact metamorphism, corresponding to formation of garnet+quartz coronitic textures around molybdenite and other minerals in the deposits. The results indicate that granulite-facies conditions prevailed at 973±4 Ma, near the end of a protracted event of regional metamorphism (1.03-0.97 Ga). Biotite dehydration melting recorded in Ørsdalen took place at a pressure of ca. 5.5 kbar (orthopyroxene-garnet-plagioclase-quartz thermobarometry), possibly in association with regional decompression. The study shows that granulite-facies metamorphism (0.97 Ga) took place before intrusion of massif-type anorthosites in

  1. Bulk elastic anisotropy of a foliated biotite gneiss from the Outokumpu deep drill hole: 3D velocity calculations and laboratory seismic measurements

    Czech Academy of Sciences Publication Activity Database

    Ivankina, T. I.; Kern, H.; Lokajíček, Tomáš; Nikitin, A. N.

    s. l. : European Seismological Comission, 2010. ---. [European Seismological Comission General Assembly /32./. 06.09.2010-10.09.2010, Montpellier] R&D Projects: GA AV ČR IAA300130906 Institutional research plan: CEZ:AV0Z30130516 Keywords : Fine-grained biotite gneiss * neutron diffraction * elastic anisotropy lattice preferred orientation * shape preferred orientation Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  2. Fractional crystallization of high-K arc magmas: biotite- versus amphibole-dominated fractionation series in the Dariv Igneous Complex, Western Mongolia

    Science.gov (United States)

    Bucholz, Claire E.; Jagoutz, Oliver; Schmidt, Max W.; Sambuu, Oyungerel

    2014-11-01

    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

  3. Distribution of elements among minerals of a single (muscovite- biotite granite sample – an optimal approach and general implications

    Directory of Open Access Journals (Sweden)

    Janoušek Vojtěch

    2014-08-01

    Full Text Available The petrography and mineral chemistry of the coarse-grained, weakly porphyritic (muscovite- biotite Říčany granite (Variscan Central Bohemian Plutonic Complex, Bohemian Massif were studied in order to assess the distribution of major and trace elements among its minerals, with consequences for granite petrogenesis and availability of geochemical species during supergene processes. It is demonstrated that chemistry-based approaches are the best suited for modal analyses of granites, especially methods taking into account compositions of whole-rock samples as well as their mineral constituents, such as constrained least-squares algorithm. They smooth out any local variations (mineral zoning, presence of phenocrysts, schlieren… and are robust in respect to the presence of phenocrysts or fabrics. The study confirms the notion that the accessory phases play a key role in incorporation of many elements during crystallization of granitic magmas. Especially the REE seem of little value in petrogenetic modelling, unless the role of accessories is properly assessed and saturation models for apatite, zircon, monazite±rutile carefully considered. At the same time, the presence of several P-, Zr- and LREE-bearing phases may have some important consequences for saturation thermometry of apatite, zircon and monazite.

  4. Assessment of Blasting Performance Using Electronic Vis-à-Vis Shock Tube Detonators in Strong Garnet Biotite Sillimanite Gneiss Formations

    Science.gov (United States)

    Sharma, Suresh Kumar; Rai, Piyush

    2016-04-01

    This paper presents a comparative investigation of the shock tube and electronic detonating systems practised in bench blasting. The blast trials were conducted on overburden rocks of Garnet Biotite Sillimanite Gneiss formations in one of the largest metalliferous mine of India. The study revealed that the choice of detonating system was crucial in deciding the fragment size and its distribution within the blasted muck-piles. The fragment size and its distribution affected the digging rate of excavators. Also, the shape of the blasted muck-pile was found to be related to the degree of fragmentation. From the present work, it may be inferred that in electronic detonation system, timely release of explosive energy resulted in better overall blasting performance. Hence, the precision in delay time must be considered in designing blast rounds in such overburden rock formations. State-of-art image analysis, GPS based muck-pile profile plotting techniques were rigorously used in the investigation. The study revealed that a mean fragment size (K50) value for shock tube detonated blasts (0.55-0.59 m) was higher than that of electronically detonated blasts (0.43-0.45 m). The digging rate of designated shovels (34 m3) with electronically detonated blasts was consistently more than 5000 t/h, which was almost 13 % higher in comparison to shock tube detonated blasts. Furthermore, favourable muck-pile shapes were witnessed in electronically detonated blasts from the observations made on the dozer performance.

  5. Decrease in water activity due to fluid absent partial melting monitored with water content in biotite in the Western Adamello contact aureole (Italy)

    Science.gov (United States)

    Siron, Guillaume; Baumgartner, Lukas; Bouvier, Anne-Sophie; Vennemann, Torsten

    2016-04-01

    The fluorine and chlorine exchange on the hydroxyl site in micas is used to monitor changes in fluid composition (Munoz 1984). Most studies assume that the OH-site does not contain vaccancies, since the vast majority of studies use analytical techniques that does not allow to directly measure the OH- content of the mica. Nevertheless, studies have shown that significant amounts of O2- are present, and its concentration increases with temperature and titanium content. This feature was intrepreted as the consequence of a Ti-oxygen exchange in amphibolite and granulite facies rocks (Dyar et al. 1993, Cesare et al. 2008). Here, we present OH, F, Cl data for biotite from contact aureoles from biotite-schist to partially molten sillimanite-cordierite schists. OH-F-Cl content of biotites were analyzed using Secondary Ion Mass Spectrometry (SIMS), and major elements were analyzed by EMP. Samples were collected in the mid-crustal Western Adamello contact aureole (Italian Alps, Floess and Baumgartner, 2013). For that purpose we used biotite standards with water content constrained by Thermal Conversion Elemental Analyzer (TC/EA) see Bauer and Vennemann 2014, at a level of precision of 0.1-0.2 wt% (2SD). SIMS measurements typically have a precision of 0.1wt% (2SD), corresponding to the homogeneity of the internal standard at the SwissSIMS laboratory. OH- content decreases in samples with increasing peak temperature and Ti content (Ti range for biotites of 0.15-0.42 p.f.u for all samples). Nevertheless, within each individual sample, OH- is not a function of Ti. Ti variations are about 0.4 p.f.u., which is ten times the analytical uncertainty of the EMP analysis (0.004 p.f.u., 1SD). Water content is constant within analytical precision for each sample. The mean of OH- measurements is 3.41 p.f.u. in biotite and garnet grade samples, whereas those of samples in the partially molten zone have values of 3.27 p.f.u. We do not see any correlation with XMg or F and Cl. Hence, we

  6. Chemistry, reaction mechanisms and micro-structures during retrograde metamorphism of gedrite-biotite-plagioclase bearing rocks from Bergslagen, south-central Sweden

    Science.gov (United States)

    Ferrow, Embaie A.; Ripa, Magnus

    1991-01-01

    The Proterozoic rhyolitic volcanics constituting the foot-wall rocks in the Stollberg ore-field, Bergslagen, south-central Sweden, locally contain gedrite altered to chlorite and serpentine, biotite altered to chlorite and plagioclase altered to epidote. The intergrowths between the host gedrite and the chlorite/serpentine inclusions are oriented with the a ∗ of gedrite parallel to the c ∗ of serpentine and chlorite. The biotite has been altered to chlorite by brucitization of both the K-interlayer and talc-like layer. In both cases the net change in volume during chloritization is small. The assumption that Al is conserved during alteration of gedrite and biotite agrees very well with the micro-structures and orientation relations observed by transmission electron microscopy. Normalizing the chlorite to 1.00 mole, the overall chemical change that took place during the retrograde metamorphism of the Stollberg rocks can be written as: 0.84Ged+0.14Bio+0.65Mg+4.76H 2O+0.42H=1.00Chl+0.57Alb+0.72Fe+0.01Na+0.12K+0.01Ti+0.05Mn+0.95H 4SiO 4 The reaction results in ca 9% increase in volume for the solid phases. Thus, a slightly acidic Mg-rich fluid started the reaction and, upon leaving the system, the metasomatic fluid was enriched in Na, Fe, K, and Si.

  7. Modeling of the impact of dolomite and biotite dissolution on vermiculite composition in a gneissic shallow aquifer of the Sila Massif (Calabria, Italy)

    International Nuclear Information System (INIS)

    Highlights: • First reaction path modeling exercise including the thermodynamic data for several vermiculite compositions. • Prevalence of dolomite dissolution leads to Mg–Al- and Ca–Al-vermiculites. • Prevalence of biotite dissolution leads to Mg–Mg–Fe- and Ca–Mg–Fe vermiculites. • Reaction path modeling confirms that vermiculite composition is also a function of pH. - Abstract: Reaction path modeling of water–rock interaction in a gneissic shallow aquifer of the Sila Massif was performed in kinetic (time) mode, under conditions of closed-system with secondary minerals and closed-system with CO2, to investigate the influence of both dolomite dissolution and biotite dissolution on the chemical characteristics of secondary vermiculites. Magnesium–Al- and calcium–Al-vermiculites are the major components of the vermiculite solid solution precipitated in the early stages of the process, which is dominated by dolomite dissolution. In contrast, Mg–Mg–Fe- and Ca–Mg–Fe vermiculites are important components of the vermiculite solid solution produced in the late stages of the process, where biotite dissolution prevails. Outcomes of this reaction-path-modeling exercise on vermiculite chemistry are fully consistent with the results obtained by Apollaro et al. (in press) through speciation–saturation calculations. In particular, Apollaro et al. (in press) showed that the pH of Mg–Al-vermiculite/Mg–Mg–Fe-vermiculite coexistence is 7.3. This value is virtually equal to the pH of Mg–Al-vermiculite/Mg–Mg–Fe-vermiculite iso-activity, 7.35, which is obtained from the results of reaction-path-modeling runs 3 and 4 carried out in this work

  8. Experimental study on dehy- dration melting of natural biotite-plagioclase gneiss from High Himalayas and implica- tions for Himalayan crust anatexis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Here we present the results of dehydration melting, melt morphology and fluid migration based on the dehydration melting experiments on natural biotite- plagioclase gneiss performed at the pressure of 1.0-1.4 GPa, and at the temperature of 770-1028℃. Experimental results demonstrate that: (ⅰ) most of melt tends to be distributed along mineral boundaries forming "melt film" even the amount of melt is less than 5 vol%; melt connectivity is con-trolled not only by melt topology but also by melt fraction; (ⅱ) dehydration melting involves a series of subprocesses including subsolidus dehydration reaction, fluid migration, vapor-present melting and vapor-absent melting; (ⅲ) ex-periments produce peraluminous granitic melt whose com-position is similar to that of High Himalayan leucogranites (HHLG) and the residual phase assemblage is Pl+Qz+Gat+Bio+Opx±Cpx+Ilm/Rut±Kfs and can be compa-rable with granulites observed in Himalayas. The experi-ments provide the evidence that biotite-plagioclase gneiss is one of source rocks of HHLG and dehydration melting is an important way to form HHLG and the granulites. Addition-ally, experimental results provide constraints on determining the P-T conditions of Himalayan crustal anatexis.

  9. Zircon U-Pb And Biotite 40Ar/39Ar Ages Of Kohistan Lower Crustal Tonalite And Their Implications For The History Of Continental Collision

    Science.gov (United States)

    Nakajima, T.; Williams, I. S.; Hyodo, H.; Miyazaki, K.; Sano, S.; Kausar, A. B.

    2002-12-01

    The Kohistan block in northern Pakistan exposes a crustal cross section through an ancient oceanic island arc, comprising garnet pyroxenite, garnet granulite, banded amphibolite, norite gabbro, metasediment and metavolcanics. The Dasu Tonalite intrudes the lower crustal Kamila Amphibolite. The tonalite is foliated and folded concordantly with the host amphibolite, indicating syn-tectonic intrusion, and contains abundant magmatic epidotes, indicating high-P crystallization. The Dasu Tonalite is extremely poor in K2O (0.6-0.9 wt.% for SiO2 64-70%) and has a low initial 87Sr/86Sr (0.7037-0.7038, similar to the associated lower crustal amphibolite and granulite), consistent with juvenile granitic magma free of contamination by recycled upper crust. The Dasu Tonalite gave SHRIMP zircon U-Pb ages of 97.6+/-1.0 Ma and 98.0+/-1.1 Ma on two samples, and biotite 40Ar/39Ar ages of 69.7+/-0.7 Ma and 69.7+/-0.9 Ma. The euhedral shape and lack of overgrowth or resorption features in CL images of the zircons suggest a simple magmatic history starting at ca. 98 Ma with no evidence for a later major thermal event. The large discrepancy between the U-Pb and Ar-Ar ages might record the deep crustal residence time of the Dasu Tonalite. The tonalite magma was probably generated and crystallized at ca. 98 Ma, then remained in the lower crust at a temperature of about 700C (which is given by geothermometry of the intercalating Kamila amphibolite), cooling down to ca.300C at 69.7Ma. 69.7Ma is a cooling age during the process of exhumation of the Kohistan arc caused by the Indian collision.

  10. Experimental Observations of the Patterns of Fungi-Mineral Surfaces Interactions with Muscovite, Biotite, Bauxite, Chromite, Hematite, Galena, Malachite, Manganite and Carbonate Substrates.

    Science.gov (United States)

    Claeys, P.

    2006-12-01

    In an in vitro experimental work, mineral substrates of muscovite, biotite, bauxite, chromite, hematite, galena, malachite, manganite and carbonate were exposed to free fungal growth and interaction in Petri dishes under open conditions. All of the experimental minerals were examined by XRD for identity and purity. The 12-week experiment resulted in significant alteration of the mineral substrates. SEM, EDX, and XRD analysis showed secondary mineral biomineralization represented by different crystal morphologies of Ca- and Mg- oxalates (weddelite: CaC2O4·2H2O, whewellite CaC2O4·H2O and glushinskite: MgC2O4·2H2O), struvite: (NH4) MgPO4·6H2O, gypsum CaSO4.2H2O, and possible dolomite. Metals bioleached from the substrates included: Fe, Pb, S, Cu, Al as single crystals or aggregates, amorphous layers, amorphous aggregates, and linear forms influenced by the fungal filaments. Bauxite and manganite showed the strongest cases of bioleaching where Fe and Al were fungally extracted and deposited as separate mineral species from the Al-Fe oxides mixture, while Ca and S were extracted from the manganite substrate and deposited as gypsum. The bioleached metals were either deposited on the mineral substrates, attached to fungal filaments, embedded in the fungal mycelium or in the extracellular polysaccharide substance (EPS) layer. The EDX microanalysis of the fungal hyphae frequently revealed metal content adsorbed on the hyphae sheath surface. During the short period of the experiment, fungal interaction with the mineral surfaces produced significant biomechanical and biochemical bioweathering features: strong pitting of the mineral surfaces, exfoliation, tunnelling, dissolution, honeycomb-alveolar structures, perforations, fragmentation, and cementation. One important aspect of these interactions is the strong affinity of fungal hyphae to mineral surfaces. The fungi engulfed whole blocks of minerals in the hyphal network, irrespective of mineral surface topography with

  11. 3D velocity distribution of P- and S-waves in a biotite gneiss, measured in oil as the pressure medium: Comparison with velocity measurements in a multi-anvil pressure apparatus and with texture-based calculated data

    Science.gov (United States)

    Lokajíček, T.; Kern, H.; Svitek, T.; Ivankina, T.

    2014-06-01

    Ultrasonic measurements of the 3D velocity distribution of P- and S-waves were performed on a spherical sample of a biotite gneiss from the Outokumpu scientific drill hole. Measurements were done at room temperature and pressures up to 400 and 70 MPa, respectively, in a pressure vessel with oil as a pressure medium. A modified transducer/sample assembly and the installation of a new mechanical system allowed simultaneous measurements of P- and S-wave velocities in 132 independent directions of the sphere on a net in steps of 15°. Proper signals for P- and S-waves could be recorded by coating the sample surface with a high-viscosity shear wave gel and by temporal point contacting of the transmitter and receiver transducers with the sample surface during the measurements. The 3D seismic measurements revealed a strong foliation-related directional dependence (anisotropy) of P- and S-wave velocities, which is confirmed by measurements in a multi-anvil apparatus on a cube-shaped specimen of the same rock. Both experimental approaches show a marked pressure sensitivity of P- and S-wave velocities and velocity anisotropies. With increasing pressure, P- and S-wave velocities increase non-linearly due to progressive closure of micro-cracks. The reverse is true for velocity anisotropy. 3D velocity calculations based on neutron diffraction measurements of crystallographic preferred orientation (CPO) of major minerals show that the intrinsic bulk anisotropy is basically caused by the CPO of biotite constituting about 23 vol.% of the rock. Including the shape of biotite grains and oriented low-aspect ratio microcracks into the modelling increases bulk anisotropy. An important finding from this study is that the measurements on the sample sphere and on the sample cube displayed distinct differences, particularly in shear wave velocities. It is assumed that the differences are due to the different geometries of the samples and the configuration of the transducer-sample assembly

  12. Disturbed 40Ar 39Ar systematics in hydrothermal biotite and hornblende at the Scotia gold mine, Western Australia: Evidence for argon loss associated with post-mineralisation fluid movement

    Science.gov (United States)

    Kent, Adam J. R.; Campbell McCuaig, T.

    1997-11-01

    Homblende and biotite that formed during gold mineralisation at the Scotia mine, Western Australia, have erratic 40Ar 39Ar release spectra and total gas ages that are ˜200-900 million year younger than the ca. 2600-2620 Ma minimum age of gold mineralisation, as given by 40Ar 39Ar plateau (muscovite) ages of crosscutting pegmatite dykes. Analysed hornblendes are dominated by magnesio hornblende but also contain small domains of ferro-actinolitic hornblende, actinolitic hornblende, and actinolite. Biotite also appears to be substantially altered to chlorite along cleavage planes. Relatively young apparent ages and high K/Ca ratios of argon released from hornblendes at temperatures less than ˜1000°C are interpreted to be the result of degassing of contaminant biotite. However, this cannot totally explain the young ages of hornblendes. Gas fractions released at furnace temperatures above 1000 C, where the effect of biotite degassing is demonstrably negligible, still have apparent ages that are ˜200-900 million years younger than the age of muscovite from post-gold pegmatite dykes. The close proximity of disturbed hydrothermal hornblende samples to apparently undisturbed pegmatite muscovite samples (less than a few metres in some cases) is difficult to reconcile with argon loss in hydrothermal hornblende being the product of thermally-driven volume diffusion. Given a suitable thermal history, argon loss could occur preferentially in hornblendes if (1) the closure (for slow cooling) and blocking (for reheating) temperatures of hydrothermal hornblendes were lower than published estimates, as has been observed in structurally complex metamorphic hornblendes and/or (2) the closure and blocking temperature of pegmatite muscovite were higher than commonly estimated. However, neither of these interpretations can easily explain the large variation in hornblende ages. It is instead suggested that argon loss occurred during mineral-fluid interaction during movement of a

  13. The Microarea Composition of Garnet and Biotite from the Ji‘an Group in Tonghua District and Its Significance as an Indicator of Metamorphic P—T—t Path

    Institute of Scientific and Technical Information of China (English)

    卢良兆; 靳是琴; 等

    1997-01-01

    The garnet(Grt)and biotite(Bt) from gneisses of the Ji'an Group are characterized by diffusion zoning at the rim,but equilibrium composition of metamorphic peak is usually remained in extensive interior area.Garnet with growth zoning is also found in the kyanite zone.In the light of microarea compositional variation of Grt and Bt,the temperature and pressure at the progressive,peak and post-peak metamorphic stages are determined by correctly using Grt Bt thermometer and GASP barometer.On this basis,a counterclockwise P-T-t path can be constructed,which reflects the closing process of an ensialic rift belt in this region during the Early Proterozoic.

  14. 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

    Science.gov (United States)

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

    2008-03-01

    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

  15. 黑龙江金厂矿区黑云母花岗岩成因及含矿性%Genesis and Ore-Bearing Potential for Biotite Granite in the Jinchang Au Deposit, Heilongjiang

    Institute of Scientific and Technical Information of China (English)

    张宏辉; 陈凯; 陈可忠; 占达积; 谭开远

    2015-01-01

    黑龙江省东宁县金厂金矿发现于20世纪60年代.20世纪90年代开始,武警黄金地质研究所和武警黄金第一总队在此开展找矿勘探工作并相应完成对其的科学研究工作.目前,该金矿已提交金资源量(333)超过 90 吨,是国内外罕见的以金为主的大型斑岩型金矿床.矿区主要岩性为花岗岩、花岗闪长岩、石英闪长岩等,可分为五期.通过研究印支晚期第三阶段黑云母花岗岩的演化、成岩成矿及含矿性,对找矿有指导作用.%The Jinchang Gold Deposit in Heilongjiang Province was discovered in the 1960's. The Geological Research Institute and First Corps of Gold Geological Party of CAPF have explored and researched since the 1990's. It has obtained gold reserves over 90 tons of gold (333). Au mineralization is related to the third stage biotite granite of the Late Indo-Chinese epoch.

  16. Biotite and chlorite weathering at 25 degrees C: the dependence of pH and (bi)carbonate on weathering kinetics, dissolution stoichiometry, and solubility; and the relation to redox conditions in granitic aquifers

    International Nuclear Information System (INIS)

    We have studied the kinetics and thermodynamics of biotite and chlorite weathering in the pH range 22-102 year); and 2. the development of characteristic Fe(III) concentrations (10-5 M in 10-1 years). The Fe(III)-bearing clay minerals formed during these experiments are similar to the fracture-filling-material observed at the Aespoe Hard Rock Laboratory. Such clays can provide reducing capacity to a repository. They can help maintain anoxic conditions by consuming oxygen that enters the repository during the construction and operation phases thereby helping maintain the redox stability of the repository regarding canister corrosion. The half-life of oxygen trapped in the repository at the time of closure depends on the rate of oxygen uptake by Fe(II) minerals, sulfide minerals and organic carbon. Fe(II)-clay minerals are important to the redox stability of a repository, as well as providing a sorption barrier to radionuclide migration. 107 refs, 52 figs, 35 tabs

  17. SHRIMP U-Pb Dating of the Zircon from the Hercynian Biotite Monzonitic Granites in Urad Zhongqi,Inner Mongolia,and Its Geological Significance%内蒙古乌拉特中旗海西期黑云母二长花岗岩锆石SHRIMP U-Pb年龄及其地质意义

    Institute of Scientific and Technical Information of China (English)

    王挽琼; 刘正宏; 王兴安; 张超; 范志伟; 时溢; 朱凯

    2012-01-01

    对乌拉特中旗德尔斯地区黑云母二长花岗岩岩相学、锆石SHRIMP U-Pb年代学和岩石地球化学进行了研究,并讨论了岩石成因及研究区晚海西期构造演化.黑云母二长花岗岩发育两期:早期为中粗粒斑状黑云母二长花岗岩,晚期为中细粒黑云二长花岗岩.岩石中的锆石大部分具核-边结构:边部震荡环带发育,Th/U值为0.16~0.50,反映了岩浆成因;核部呈浑圆状,多数具岩浆环带,个别弱分带-无分带,Th/U值为0.06~0.44,表明核部大部分属岩浆型残留锆石,个别为变质型残留锆石.测年结果显示:边部锆石加权平均年龄为早、中二叠世((279±3)Ma、(266±3)Ma),代表黑云母二长花岗岩形成时代;核部残留锆石加权平均年龄为(1 972±63) Ma、(1 962±43) Ma,代表源岩的形成时代.岩石属于亚碱性系列,REE配分形式呈右倾型,LREE/HREE为5.86~22.81,明显亏损高场强元素Nb,富集大离子亲石元素Rb、Ba,显示活动大陆边缘火成岩的地球化学特征.黑云母二长花岗岩地球化学属性反映了早、中二叠世古亚洲洋向华北板块北缘的俯冲作用及古亚洲洋消亡的演化历史.%Petrography, SHRIMP U - Pb chronology of the zircon and geochemistry of the Hercynian biotite monzonitic granites in Deersi area of Urad Zhongqi are studied to constrain the genesis of the rock and regional tectonic evolution in the study area. The emplacement of the biotite monzonitic granite in this area can be divided into two periods, the earlier is medium-coarse prophyritic biotite monzonitic granite and the latter is medium-fine grain biotite monzonitic granite. Most of zircons from biotite monzonitic granites show core-mantle ring structure, fine-scale oscillatory zoning and Th/U ratios of 0. 16 - 0. 50, implying their magmatic origin. Whereas most of cores of rouded zircons have fine-scale oscillatory zoning and Th/U ratios of 0. 06 - 0. 44, which indicates their magmatic genesis and

  18. 陕西华阳川铀多金属矿床黑云母40Ar/39Ar年龄及其地质意义%40 Ar/39 Ar Geochronology of Biotite in Huayangchuan Uranium-Polymetallic Deposit in Shanxi Province and its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    何升; 李子颖; 惠小朝; 郭建

    2016-01-01

    In this study , the forming age of Huayangchuan uranium‐polymetallic deposit was performed on the biotite using Ar Ar dating method.Biotite in carbonatite was dated with a plateau age of 132.58 ± 0.70 Ma ,an isochron age of 133.01 ± 0.74 Ma ,and biotite in biotite‐amphibole‐sulfide‐bearing peg‐matite was dated with a plateau age of 93.72 ± 2.38 Ma , an isochron age of 91.49 ± 1.97 Ma.Microprobe examination found that the biotite was formed prior to the betafite , and therefore the betafite was believed to be formed later than 93.72 ± 2.38 Ma ,which suggested there was a later Early Cretaceous magma hydrothermal U Nb Ti mineralization process in Xiaofuyu‐Huayangchuan‐Huan‐glongpu mineralization belte beside the discoved Triassic carbonatite vein‐type Mo Pb , there occured a Cretaceous porphyry Mo metalization process.%笔者采用Ar Ar测年技术,获得华阳川铀多金属矿床碳酸岩中黑云母40 Ar/39 Ar坪年龄132.58±0.70Ma ,等时线年龄133.01±0.74Ma ,含黑云母闪石硫化物伟晶岩中黑云母的40Ar/39Ar坪年龄93.72±2.38Ma ,等时线年龄91.49±1.97Ma。镜下特征显示,铌钛铀矿的形成晚于碳酸岩中的黑云母及含黑云母闪石硫化物伟晶岩中的黑云母。因此,铌钛铀矿的形成时间应晚于93.72±2.38Ma。这表明成矿带内除了已知存在三叠纪碳酸岩型Mo Pb矿和白垩纪斑岩型Mo矿的成矿过程之外,还存在早白垩世之后的岩浆热液型U Nb Ti成矿过程。

  19. 大青山-乌拉山变质杂岩带大南沟地区含榴尖晶黑云钾长片麻岩成因及其形成的P-T条件%Petrogenesis and metamorphic P-T conditions of garnet-spinel-biotite-bearing paragneiss in Danangou area, Daqingshan-Wulashan metamorphic complex belt

    Institute of Scientific and Technical Information of China (English)

    蔡佳; 刘福来; 刘平华; 施建荣; 刘建辉

    2013-01-01

    大南沟贫硅的含榴尖晶黑云钾长片麻岩出露于华北克拉通西北部大青山-乌拉山变质杂岩带(孔兹岩带)中,主要以大小不等的透镜状和互层状产于石榴长英质粒状岩石和石榴堇青夕线黑云二长片麻岩中.本文通过岩相学、变质反应、成因矿物学、矿物化学以及相平衡模拟的综合研究,揭示合榴尖晶黑云钾长片麻岩的成因机制及其形成的P-T条件.研究表明,大南沟含榴尖晶黑云钾长片麻岩内尖晶石的Zn含量极低(XZn=Zn/(Fe2+Mg+ Zn)<0.006).含尖晶石的后成合晶微域反映峰后退变条件下局部的再平衡过程,其中石榴石分解形成的钾长石+尖晶石±斜长石后成合晶是由Grt+ Sil+ Melt→Kfs+Spl+ Pl反应形成的.而细粒尖晶石-刚玉-磁铁矿矿物组合及相应的退变结构是在晚期降温和氧化作用下,通过反应Splss+O2→Spl+ Mag+ Crn分解形成的.相平衡模拟结果表明含榴尖晶黑云钾长片麻岩峰期矿物组合为Bt+ Grt+ Spl+ Mag+ Sil+Kfs +P1+ Liq,稳定的温压条件在830~ 870℃和8.3~8.6kb,位于夕线石的稳定域.%Danangou garnet-spinel-biotite-bearing paragneiss occurs as interlayers or various lenses within garnet-bearing quartzofeldspathic rocks and garnet-cordierite-sillimanite-bearing paragneisses,Daqingshan-Wulashan metamorphic complex belt,North China Craton.The combined studies of petrography,metamorphic reaction,genetic mineralogy,and quantitative phase modeling provide insight into the origin of the garnet-spinel-biotite-bearing paragneiss.This typical silica-undersaturated metamorphic rock mainly consists of garnet,spinel,biotite,sillimanite,K-feldspar with secondary minerals of magnetite,apatite,quartz,etc.Thereinto,spinel has extremely low gahnite content with XZn ratio < 0.006 (XZn =Zn/(Fe2 + + Mg + Zn).Spinel-beating mineral assemblages within the same microdomain were formed at the late re-equilibration stage corresponding to the decompression or cooling

  20. Heat capacities and thermodynamic properties of annite (aluminous iron biotite)

    Science.gov (United States)

    Hemingway, B.S.; Robie, R.A.

    1990-01-01

    The heat capacities have been measured between 7 and 650 K by quasi-adiabatic calorimetry and differential scanning calorimetry. At 298.15 K and 1 bar, the calorimetric entropy for our sample is 354.9??0.7 J/(mol.K). A minimum configurational entropy of 18.7 J/(mol.K) for full disorder of Al/Si in the tetrahedral sites should be added to the calorimetric entropy for third-law calculations. The heat capacity equation [Cp in units of J/mol.K)] Cp0 = 583.586 + 0.075246T - 3420.60T-0.5 - (4.4551 ?? 106)T-2 fits the experimental and estimated heat capacities for our sample (valid range 250 to 1000 K) with an average deviation of 0.37%. -from Authors

  1. Geochemistry, zircon U-Pb dating and Pb-Sr-Nd isotopic composition of the gneissic biotite granodiorite in Mainling County, Tibet%西藏米林县片麻状黑云花岗闪长岩地球化学特征、锆石U-Pb定年及Pb-Sr-Nd同位素组成

    Institute of Scientific and Technical Information of China (English)

    时超; 李荣社; 何世平; 王超; 辜平阳; 计文化; 查显锋; 张海迪

    2012-01-01

    The Himalayan orogenic belt, caused by the subduction and collision between Indian plate and Eurasian plate, is the youngest and largest currently active orogenic belt in the world. The LA-ICP-MS U-Pb zircon age of 515.5 ± 2.3 Ma from the gneissic biotite granodiorite that intruded into the Namche Barwa complex in eastern syntaxis of the Himalayan orogenic belt provides a geological record of Pan-African tectonic-mag-matic event in this area. The SiO2 content is 66.47% ~72.42%, the average of the A/CNK indexes is 1.03 (0.98 ~ 1.03), and all samples fall into the peraluminous region in the A/NK-A/CNK index diagram. The Rittmann index σ is between 1.53 and 3.08, belonging to the calc-alkaline series. Most of the samples fall into a high-K calc-alkaline series area in the SiQ ~ K2O diagram. The values of TiO2, MgO, FeOT , MnO and K2O show a good linear relationship with SiO2 content in the Harker diagrams. The chondrite-nomalized REE patterns indicate that the samples are enriched in LREE, (La/Yb)N values are 19.1~63.8, with slightly negative Eu anomalies (δEu = 0.62 ~0.79). Trace elements show the depletion of Ba, Nb, Ta, Sr and Z as well as the relative enrichment of Rb, Th and U. The negative e Nd(t) values(-8.67~-10.57) and Nd model ages (tdm= 1.84 ~ 3.42) of the gneissic biotite granodiorite of Tanya Township indicate that this rock had an old upper crust material source. Combined with the initial 87Sr/86Sr ratio features, the authors hold that the source rock of the gneissic biotite granodiorite of Tanya Township was granitic magma that partially melted in a high temperature environment. From the tectonic environment discrimination diagrams, it is inferred that metalumi-nous-weakly peraluminous gneissic biotite granodiorite of Tanya Township was formed in the post-collisional stage characterized by the conversion from a compressional environment to an extensional. Combined with the isotope age 513 Ma, the authors consider that the Pan-African collisional

  2. Argon in hornblende, biotite and muscovite in geologic cooling - Ar-40/Ar-39-investigations

    International Nuclear Information System (INIS)

    The results of the Ar-40/Ar-39 studies are discussed under the aspect of whether the age data of the minerals indicate a cooling process. The author hopes that isotope dating of minerals with different closing temperatures will describe the temperature/time history of an area in the temperature range of 600 to 2000C. The findings are analyzed under three aspects: How much do they contribute to the initial methodological question, what do they contribute to the regional geology of the areas investigated, and in what respects do they extent the present knowledge of the geochronological analysis, i.e. its techniques and interpretation. (orig.)

  3. Distribution of elements among minerals of a single (muscovite-) biotite granite sample – an optimal approach and general implications

    Czech Academy of Sciences Publication Activity Database

    Janoušek, V.; Navrátil, Tomáš; Trubač, J.; Strnad, J.; Laufek, F.; Minařík, Luděk

    2014-01-01

    Roč. 65, č. 4 (2014), s. 257-271. ISSN 1335-0552 Institutional research plan: CEZ:AV0Z30130516 Institutional support: RVO:67985831 Keywords : modal analyses * trace-element residence * ICP-MS * Central Bohemian Plutonic Complex * Říčany granite Subject RIV: DD - Geochemistry Impact factor: 0.761, year: 2014

  4. The contribution of crystallographic and shape prefered orientation to the bulk elastic anisotropy of a foliated biotite gneiss

    Czech Academy of Sciences Publication Activity Database

    Kern, H.; Ivankina, T. I.; Lokajíček, Tomáš

    2009. [1-1]. [Texture and Anisotropy of Polycrystals /3./. 23.09.2009-25.09.2009, Göttingen] R&D Projects: GA ČR GA205/08/0676 Institutional research plan: CEZ:AV0Z30130516 Keywords : anisotrophy * crystallography Subject RIV: BM - Solid Matter Physics ; Magnetism

  5. Study of granitic biotites by X-ray fluorescence analysis: determination of iron, manganese, titanium, calcium, potassium, silicon and aluminium

    International Nuclear Information System (INIS)

    A method for the quantitative determination of iron, manganese, titanium, calcium potassium, silicon, and aluminium, is reported, Sample preparation is carried out by the miniature flux technique, and rubidium is used as internal standard for silicon and aluminium. (Author) 5 refs

  6. Anomalous Seismic Velocity Drop in Iron and Biotite Rich Amphibolite to Granulite Facies Transitional Rocks from Deccan Volcanic Covered 1993 Killari Earthquake Region, Maharashtra (India): a Case Study

    Science.gov (United States)

    Pandey, O. P.; Tripathi, Priyanka; Vedanti, Nimisha; Srinivasa Sarma, D.

    2016-07-01

    65 Ma Deccan Volcanic Province of western India forms one of the largest flood basaltic eruptions on the surface of the earth. The nature of the concealed crust below this earthquake prone region, which is marked by several low velocity zones at different depths has hardly been understood. These low velocity zones have been invariably interpreted as fluid-filled zones, genetically connected to earthquake nucleation. While carrying out detailed geological and petrophysical studies on the Late Archean basement cores, obtained from a 617 m deep KLR-1 borehole, drilled in the epicentral zone of 1993 Killari earthquake region of the southern Deccan Volcanic Province, we came across several instances where we observed remarkable drop in measured P-wave velocity in a number of high density cores. We provide detailed petrographic and geological data on 11 such anomalous samples which belong to mid-crustal amphibolite to granulite facies transitional rocks. They are associated with a mean P-wave velocity of 6.02 km/s (range 5.82-6.22 km/s) conforming to granitic upper crust, but in contrast have a high mean density of 2.91 g/cm3 (range 2.75-3.08 g/cm3), which characterise mid to lower crust. This velocity drop, which is as much as 15 % in some cores, is primarily attributed to FeOT enrichment (up to about 23 wt%) during the course of mantle-fluid driven retrogressive metasomatic reactions, caused by exhumation of deep-seated mafic rocks. Presence of Iron content (mainly magnetite), widely seen as opaques in thin sections of the rocks, seems to have resulted into sharp increase in density, as well as mean atomic weight. Our study indicates that the measured V p is inversely related to FeOT content as well as mean atomic weight of the rock.

  7. 磷霉素钙生物效价检定法的改进%Amelioration of bio-titer verification method for fosfomycin calcium

    Institute of Scientific and Technical Information of China (English)

    孔梅; 李慧芝; 吴连勇; 张荃

    2004-01-01

    磷霉素钙生物效价测定,原标准以藤黄微球菌[CMCC(B)28001]为实验检定菌,测定对抑菌圈边缘不清晰,影响含量测定,改用大肠杆菌[CMCC(B)44103]为实验菌,经试验证明效果比较理想.

  8. Anomalous Seismic Velocity Drop in Iron and Biotite Rich Amphibolite to Granulite Facies Transitional Rocks from Deccan Volcanic Covered 1993 Killari Earthquake Region, Maharashtra (India): a Case Study

    Science.gov (United States)

    Pandey, O. P.; Tripathi, Priyanka; Vedanti, Nimisha; Srinivasa Sarma, D.

    2016-03-01

    65 Ma Deccan Volcanic Province of western India forms one of the largest flood basaltic eruptions on the surface of the earth. The nature of the concealed crust below this earthquake prone region, which is marked by several low velocity zones at different depths has hardly been understood. These low velocity zones have been invariably interpreted as fluid-filled zones, genetically connected to earthquake nucleation. While carrying out detailed geological and petrophysical studies on the Late Archean basement cores, obtained from a 617 m deep KLR-1 borehole, drilled in the epicentral zone of 1993 Killari earthquake region of the southern Deccan Volcanic Province, we came across several instances where we observed remarkable drop in measured P-wave velocity in a number of high density cores. We provide detailed petrographic and geological data on 11 such anomalous samples which belong to mid-crustal amphibolite to granulite facies transitional rocks. They are associated with a mean P-wave velocity of 6.02 km/s (range 5.82-6.22 km/s) conforming to granitic upper crust, but in contrast have a high mean density of 2.91 g/cm3 (range 2.75-3.08 g/cm3), which characterise mid to lower crust. This velocity drop, which is as much as 15 % in some cores, is primarily attributed to FeOT enrichment (up to about 23 wt%) during the course of mantle-fluid driven retrogressive metasomatic reactions, caused by exhumation of deep-seated mafic rocks. Presence of Iron content (mainly magnetite), widely seen as opaques in thin sections of the rocks, seems to have resulted into sharp increase in density, as well as mean atomic weight. Our study indicates that the measured V p is inversely related to FeOT content as well as mean atomic weight of the rock.

  9. 3D velocity distribution of P- and S-waves in a biotite gneiss, measured in oil as the pressure medium: Comparison with velocity measurements in a multi-anvil pressure apparatus and with texture-based calculated data

    Czech Academy of Sciences Publication Activity Database

    Lokajíček, Tomáš; Kern, H.; Svitek, Tomáš; Ivankina, T.

    2014-01-01

    Roč. 231, June (2014), s. 1-15. ISSN 0031-9201 R&D Projects: GA MŠk LH13102; GA ČR(CZ) GAP104/12/0915; GA ČR GA13-13967S Institutional support: RVO:67985831 Keywords : 3D-velocity calculation * measured and calculated elastic properties * neutron diffraction * seismic anisotropy * velocity measurements Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.895, year: 2014

  10. Geology, alteration, mineralization and geochemistry at south of Arghash (Neyshabour)

    OpenAIRE

    Zahra Karimi Saeid Abadi; Seyed Ahmad Mazaheri; Mohammad Hassan Karimpour

    2010-01-01

    The Arghash area is located 45 km to southwest of Neyshabour. The subvolcanic rocks in the area consist of biotite hornblende quartz monzodiorite porphyry, hornblende biotite quartz monzodiorite porphyry, hornblende monzonite porphyry, biotite hornblende monzonite porphyry, monzodiorite porphyry and biotite quartz monzodiorite porphyry units. The volcanic rocks consist of hornblende biotite dacite, biotite hornblende dacite, and andesite and pillow lava. The plutonic rocks consist of hornblen...

  11. 河北平山阜平群夕线石浅粒岩中黑云母深熔作用的微区信息研究%STUDY OF MICRO-AREA INFORMATION ON ANATEXIS IN BIOTITE IN SILLIMANITE LEUCO-GRANULITITE OF FUPING GROUP IN PINGSHAN,HEBEI PROVINCE,CHINA

    Institute of Scientific and Technical Information of China (English)

    宋书林; 姚杰; 王安平

    2000-01-01

    通过对阜平群夕线石浅粒岩样品中黑云母的微形貌及其主要组成元素变化规律的电子显微镜研究,并结合浅粒岩和黑云变粒岩高温高压熔融实验研究结果的对比分析,获得了黑云母受深熔作用影响的微区信息.依据微形貌特征分为残留黑云母、不均一熔融黑云母和再结晶黑云母.深熔作用过程中Mg、Fe、Ti、K、Ca等元素从黑云母晶格中迁出,重组形成再结晶黑云母、磁铁矿、金红石、氟硅钠钾石类矿物.

  12. Evolution of the Santana do Araguaia (PA region based on geology and Pb-Pb zircon geochronology from granitoid rocks

    Directory of Open Access Journals (Sweden)

    Lívio Wagner Chaves Corrêa

    2014-06-01

    Full Text Available The region of Santana do Araguaia, focus of this study, is located in the southeast of Pará State, which, in its turn, lies in the southeastern Amazonian Craton. From the tectonic point of view, it is positioned in the Domain Santana do Araguaia, interpreted as an Archean terrain affected by the Transamazonic Cycle. A petrographic and geochronological study, supported by field data, was undertaken in granitoids of the region in order to unravel the evolution of this field. In modal terms, the studied rocks consist of biotite monzogranite, biotite metagranodiorite, hornblende-biotite granodiorite, hornblende-biotite metatonalite and enderbite. These rocks present themselves undeformed to moderately deformed, with some particularities: the biotite metagranodiorite presents foliation following an E-W trend; the hornblende-biotite metatonalite has a foliation following the NW-SE direction, usually with high to subvertical dives, the biotite monzogranite is isotropic, and lithologies hornblende-biotite granodiorite and enderbite show only a slight orientation of their crystals, mainly noticeable in thin section. These rock types were analyzed by evaporating Pb zircon method and the following ages were obtained: biotite metagranodiorite, 3066±3 Ma and 2829±13 Ma, hornblende-biotite metatonalite, 2852±2 Ma, biotite monzogranite, 2678 to 2342 Ma, hornblende-biotite granodiorite, 1990±7 Ma, and enderbite, 1988±4 Ma. The geochronological data indicate that the rocks crystallized both in the Archean and in the Paleoproterozoic; however, no evidence to prove the action of the Transamazonic Cycle was detected in the region.

  13. Geology, alteration, mineralization and geochemistry at south of Arghash (Neyshabour

    Directory of Open Access Journals (Sweden)

    Zahra Karimi Saeid Abadi

    2010-11-01

    Full Text Available The Arghash area is located 45 km to southwest of Neyshabour. The subvolcanic rocks in the area consist of biotite hornblende quartz monzodiorite porphyry, hornblende biotite quartz monzodiorite porphyry, hornblende monzonite porphyry, biotite hornblende monzonite porphyry, monzodiorite porphyry and biotite quartz monzodiorite porphyry units. The volcanic rocks consist of hornblende biotite dacite, biotite hornblende dacite, and andesite and pillow lava. The plutonic rocks consist of hornblende monzodiorite, hornblende monzonite, quartz monzonite, hornblende quartz monzodiorite, biotite granodiorite, hornblende granodiorite, biotite hornblende granodiorite, biotite quartz diorite and pyroxene dolerite units. Five types of alteration including propylitic, carbonate, argillic, silicification and sericitic were recognized. Those are subdivided into twelve sub-zones based on the mineral abundances and intensity of alteration. Primary pyrite, 3-4%, is found mainly as disseminated. Secondary mineralization includes limonite, hematite and jarosite. Twenty rock chip and 8 stream sediment samples were collected for geochemical exploration. The samples were analysed for Cu, Zn, Pb, Ag and Sb using Atomic Absorbtion Spectrophotometric (AAS method. In stream sediment samples, Cu abundance is 34-58 ppm, Zn 45-422 ppm, Pb 28-42 ppm and Ag 2-12 ppm; whereas in rock chip samples, Cu abundance is 8-1137 ppm, Zn 13-411 ppm, Pb 15-97 ppm and Ag 3-32 ppm.

  14. STUDY ON THE18O DEPLETION IN THE SUZHOU Nb,Ta-BEARING GRANITE

    Institute of Scientific and Technical Information of China (English)

    WangRucheng; XuShijin; ShenWeizhou; XuKeqin

    1997-01-01

    The Suzhou granite is one of the farnous-Nb,Ta-bearing granites in China. Petrographic studies permitted to divide it into three intrusion stages;the first stage-medium-grained am-phibole-biotite granite,the second stage-medium-to-fine-grained biotite granite ,and the third

  15. Investigation into the metamorphic Nappes of the Central Scandinavian Caledonides on the basis of Rb-Sr and K-Ar age determination

    International Nuclear Information System (INIS)

    This study concerns age determinations on several rock units of metamorphic nappes in the central Scandinavian Caledonides. Rb-Sr analyses on whole-rocks and minerals (biotite, muscovite/phengite, feldspars, garnet) were made as well as K-Ar determinations on biotite, muscovite/phengite, amphibole and feldspar. (Auth.)

  16. Bedrock Geology of the Thiel Mountains, Antarctica.

    Science.gov (United States)

    Ford, A B; Aaron, J M

    1962-09-01

    Cordierite-bearing, hyper-sthene-quartz monzonite porphyry, the most widespread rock unit, is intruded by biotite granite and porphyritic biotite granite. Sedimentary and metasedimentary rocks, mainly quartzites and argillites, have been metamorphosed locally to hornfels and have been involved in high-angle faulting. Shear zones are common in the plutonic rocks. PMID:17732193

  17. Microstructural records of multiple retrograde local H2O supplement in the pelitic gneiss, Lützow-Holm Complex at Akarui Point, East Antarctica

    Science.gov (United States)

    Nakamura, Aya; Kitamura, Masao; Kawakami, Tetsuo

    2014-04-01

    The alkali-feldspar and biotite in the sillimanite-biotite-garnet gneiss from East Antarctica preserves characteristic microstructural evidence of multi-stage H2O supplement during the retrograde metamorphism. The first microstructural evidence is the "zoned feldspar," in which the mesoperthitic zone, the anti-perthitic zone, and lamella-free plagioclase zone coexist within a single crystal. They are occasionally found next to biotite, and are always depleted in orthoclase (Or) component toward the biotite. The formation process of this microstructure could be explained by the diffusion that oversteps the solvus. The second microstructural evidence is the serrate boundary between alkali-feldspar and biotite. The projections of biotite are selectively developed next to Or lamellae of alkali-feldspar every 3-5 μm. These two microstructures would have formed as the biotite grew by consuming potash in alkali-feldspar when H2O-bearing fluid locally passed through the grain boundaries. The former microstructure was formed at 825-900 °C before lamella formation, and the latter microstructure was formed after the lamella formation. These microstructures are the indicators of fluid pathways formed under two different temperature conditions. The common coexistence of these microstructures implies that the fluid used similar pathways during the retrograde metamorphism.

  18. Magnetic petrology of the Água Azul and Água Limpa granodiorites, southern portion of the Carajás Domain – Pará

    Directory of Open Access Journals (Sweden)

    Eleilson Oliveira Gabriel

    2013-12-01

    Full Text Available The Água Azul and Água Limpa granodiorites (AAGrd and ALGrd, respectively outcrop in the extreme southern of the Carajás Domain as two elongated bodies following the EW regional trend and were previously included in the Xingu Complex. The ALGrd consists mainly of biotite-amphibole granodiorites and muscovite-biotite granodiorites, with subordinate amphibole-biotite tonalites; the AAGrd contains dominant epidote-amphibole-biotite granodiorites, epidote-amphibole-biotite tonalite and restricted (amphibole-epidote-biotite monzogranites. These rocks show geochemical signatures like of archaean sanukitoids. The magnetic susceptibility (MS values obtained in the ALGrd (average 17.54 × 10-4 SIv and AAGrd (average 4.19 × 10-4 SIv are relatively low. The main opaque minerals are magnetite and hematite, and ilmenite is lacking in these rocks. The ALGrd contains titanite associated with magnetite, while the AAGrd contains pyrite, chalcopyrite, and goethite. In the ALGrd, magnetite is more developed and large than in the AAGrd, justifying its highest values of MS. The oxidation of magnetite (martitization and the alteration of sulfides to goethite, occurred at low temperatures. The positive correlation between MS values and the modal content of opaque, amphibole, epidote + allanite and quartz + K-feldspar, as well as the negative correlation of MS with biotite and mafic observed in these units, reveal a trend of MS increasing in the direction: amphibole tonalites/amphibole granodiorites à biotite granodiorites/biotite monzogranites. The geochemical data confirm this fact, with a negative correlation between the MS values and Fe2O3T, FeO, and MgO, reflecting, for the two units, an upward trend in MS values parallel to magmatic differentiation. The geochemical and mineralogical affinities between these rocks and sanukitoids of the Rio Maria Domain suggest conditions of the oxygen fugacity between HM and FMQ buffers for the studied granitoids

  19. An experimental study on the behaviour of copper and other trace elements in magmatic systems

    OpenAIRE

    Were, Patrick

    2007-01-01

    1. Distribution of trace elements between biotite and hydrous granitic melt. The synthetic system haplogranite-anorthite-biotite-H2O, doped with a suite of trace elements (V, Cr, Co, Ni, Cu, Zn, Rb, Cs, Sr, Ba, Mo, W, Nb, Ta, REE, Pb and Zr) was experimentally investigated over the temperature interval of 700-800°C at 200 MPa (H2O) to study the distribution of trace elements between biotite and coexisting hydrous melt. The starting materials were a series of volatile-free synthetic glasse...

  20. U-Pb zircon SHRIMP ages, geochemical and Sr-Nd isotopic compositions of the Early Cretaceous I-type Sarıosman pluton, Eastern Pontides, NE Turkey

    OpenAIRE

    KAYGUSUZ, ABDULLAH; Chen, Bin; Zafer ASLAN; ŞEN, WOLFGANG SIEBEL & CÜNEYT

    2009-01-01

    The petrogenesis and U-Pb SHRIMP zircon ages of the Late Cretaceous Sarıosman pluton in the Eastern Pontides is investigated by means of whole-rock Sr-Nd isotope data with field, petrographic and whole-rock geochemical studies. The bulk of the I-type Sarıosman pluton consists of biotite-hornblende monzogranite, with minor quantities of porphyritic hornblende-biotite monzogranite. The biotite-hornblende monzogranite contains a number of mafic microgranular enclaves (MMEs) of quartz monzodiorit...

  1. Experimental study of gold activation-transportation in the process of potash metasomatism-alteration——North China platform gold deposit taken as an example

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Chemical reactions of plagioclase, biotite and their singleminerals, as well as a mineral mixture of (plagioclase +biotite+quartz), with KCl and (KCl+KHCO3) solutions were carried out at 150400℃ and 5080 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite. After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold are related to the elementary effect of the fluid-mineral interfaces. Fe3+-Fe2+, as an oxidition-reduction agent, and volatile components Cl? and CO2 play important roles in the reaction process.

  2. Experimental study of gold activation-transportation in the process of potash metasomatism-alteration ——North China platform gold deposit taken as an example

    Institute of Scientific and Technical Information of China (English)

    WANG; Yurong; HU; Shouxi

    2001-01-01

    Chemical reactions of plagioclase, biotite and their single minerals, as well as a mineral mixture of (plagioclase +biotite+quartz), with KCl and (KCl+KHCO3) solutions were carried out at 150400℃ and 5080 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite. After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold are related to the elementary effect of the fluid-mineral interfaces. Fe3+-Fe2+, as an oxidition-reduction agent, and volatile components Cl? and CO2 play important roles in the reaction process.

  3. High grade metamorphism in the Bundelkhand massif and its implications on Mesoarchean crustal evolution in central India

    Science.gov (United States)

    Singh, S. P.; Dwivedi, S. B.

    2015-02-01

    The Bundelkhand Gneissic Complex (BnGC) in the central part of the Bundelkhand massif preserves a supracrustal unit which includes pelitic (garnet-cordierite-sillimanite gneiss, garnet-sillimanite gneiss, biotite gneiss and garnet-biotite gneiss) and mafic (hornblende-biotite gneiss and garnetiferous amphibolite) rocks. Granulite facies metamorphism of the complex initiated with breaking down of biotite to produce garnet and cordierite in the pelitic gneisses. Geothermobarometric calculations indicate metamorphic conditions of 720°C/6.2 kbar, followed by a retrograde (687°C/4.9 kbar) to very late retrograde stages of metamorphism (579°C/4.4 kbar) which is supported by the formation of late cordierite around garnet. The P-T conditions and textural relations of the garnet-cordierite-bearing gneiss suggest a retrograde cooling path of metamorphism.

  4. High grade metamorphism in the Bundelkhand massif and its implications on Mesoarchean crustal evolution in central India

    Indian Academy of Sciences (India)

    S P Singh; S B Dwivedi

    2015-02-01

    The Bundelkhand Gneissic Complex (BnGC) in the central part of the Bundelkhand massif preserves a supracrustal unit which includes pelitic (garnet–cordierite–sillimanite gneiss, garnet–sillimanite gneiss, biotite gneiss and garnet–biotite gneiss) and mafic (hornblende–biotite gneiss and garnetiferous amphibolite) rocks. Granulite facies metamorphism of the complex initiated with breaking down of biotite to produce garnet and cordierite in the pelitic gneisses. Geothermobarometric calculations indicate metamorphic conditions of 720°C/6.2 kbar, followed by a retrograde (687°C/4.9 kbar) to very late retro-grade stages of metamorphism (579°C/4.4 kbar) which is supported by the formation of late cordierite around garnet. The P–T conditions and textural relations of the garnet–cordierite-bearing gneiss suggest a retrograde cooling path of metamorphism.

  5. Clay minerals sorbing radiocesium in Fukushima. Investigation by IP autoradiography and electron microscopy

    International Nuclear Information System (INIS)

    Although more than four years have passed after the accident at the Fukushima-Daiichi nuclear power plant, the state of radioactive cesium, which is the main source of the high radioactivity in the environment of Fukushima, is not well understood yet. To advance this situation, we tried to specify radioactive soil particles using IP autoradiography and electron microscopy. As a result, the radioactive soil particles were classified into three types from their morphologies and chemical compositions: (1) conglomerates of fine clay minerals, (2) organic matter containing clay mineral particles, and (3) weathered biotite with a platy shape originated from granite. The weathered biotite is actually a biotite-vermiculite mixed layer mineral, forming a porous structure with well-developed cleavage, and kaolinite filling the cleavage spaces. It was indicated that radioactive cesium is located uniformly in the weathered biotite, rather than concentrated around the edge of the platy shape. (author)

  6. Development of modal layering in granites: a case study from the Carna Pluton, Connemara, Ireland

    Science.gov (United States)

    McKenzie, Kirsty; McCarthy, William; Hunt, Emma

    2016-04-01

    Modal layering in igneous rocks uniquely record dynamic processes operating in magma chambers and also host a large proportion of Earth's strategic mineral deposits. This research investigates the origin of biotite modal layering and primary pseudo-sedimentary structures in felsic magmas, by using a combination of Crystal Size Distribution (CSD) analysis and Electron Probe Microanalysis (EPMA) to determine the mechanisms responsible for the development of these structures in the Carna Pluton, Connemara, Ireland. The Carna Pluton is a composite granodiorite intrusion and is one of five plutons comprising the Galway Granite Complex (425 - 380 Ma). Prominent 30 cm thick modal layers are defined by sharp basal contacts to a biotite-rich (20%) granite, which grades upward over 10 cm into biotite-poor, alkali-feldspar megacrystic granite. The layering strikes parallel to, and dips 30-60° N toward the external pluton contact. Pseudo-sedimentary structures (cross-bedding, flame structures, slumping and crystal graded bedding) are observed within these layers. Petrographic observations indicate the layers contain euhedral biotite and fresh undeformed quartz and feldspar. Throughout the pluton, alkali-feldspar phenocrysts define a foliation that is sub-parallel to the strike of biotite modal layers. Together these observations indicate that the intrusion's concentric foliation, biotite layers and associated structures formed in the magmatic state and due to a complex interaction between magma flow and crystallisation processes. Biotite CSDs (>250 crystals per sample) were determined for nine samples across three biotite-rich layers in a single unit. Preliminary CSD results suggest biotite within basal contacts accumulated via fractional crystallisation within an upward-growing crystal pile, likely reflecting the yield strength of the magma as a limiting factor to gravitational settling of biotite. This is supported by the abrupt decrease in mean biotite crystal size across

  7. 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)

  8. Petrology and U-Pb zircon dating of intrusive rocks from A, C-south, and Dardvay districts, Sangan iron stone mine, Khaf

    OpenAIRE

    Abbas Golmohammadi; Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Seyed Ahamad Mazaheri

    2013-01-01

    Sangan magnetite skarn mine is located 300 km southeast of Mashhad, along the eastern part of Khaf-Drouneh volcanic-plutonic belt. Granitoids from three areas within the Sangan mine A, C-North and Dardvay were studied. Within the study area, three intrusive rocks including biotite-hornblende monzonite porphyry, biotite syenite and syenogranite were recognized. Based on field cross cutting, absence of garnet-magnetite skarn around the contact, and alteration by younger hydrothermal fluids, the...

  9. Late ordovician age of camptonite dike of Agardak complex in south-east Tuva as an evidence of the presence of plume magmatism in collision orogeny

    International Nuclear Information System (INIS)

    For studying specific features of evidence and evolution of mantle magmatism in the area of the Agardak complex in south-east of Tuva geochronological investigation of biotite and kersutite samples from camptonite dike was conducted. The age of biotite calculated on the basis of isotopic data made up 446±4 mln. years. It is shown that Late Ordovician age of camptonite dikes in the Agardak complex permits considering them as a manifestation of post-collision plume magmatism

  10. Isotopic age-determinations in Bergslagen, Sweden. 8

    International Nuclear Information System (INIS)

    Biotite Rb-Sr data from 1.70-1.65 Ga ol rocks of the Gothian Trans-Scandinavian Smaland-Vaermland Granitic Belt and from 1.90-1.84 Ga old rocks of the adjoining Svecokarelian Berglagen Region indicate complete Sveconorwegian resetting 0.90 Ga ago, but a K-Ar analysis of the same biotites and of coexisting hornblendes yields significantly older ages. Some biotites and hornblendes have exceptionally high apparent ages, much oldre than those of the host rocks, pointing to the presence of excess radiogenic argon. The other K-Ar mineral ages are intermediate between the age of the host rocks and the 0.90 Ga old Sveconorwegian resetting. The hornblendes and biotites with intermediate ages show a weak positive correlation between radiogenic argon content and whole-rock potassium content. It is concluded that there was only limited mobility of radiogenic argon during the Sveconorwegian event. Apperently, the physicochemical conditions during Sveconorwegian recrystallisation were suitable for complete resetting of the Rb-Sr biotite systems, whereas the behaviour of radiogenic argon in the biotites and hornblendes was complex, leading to anomalous K-Ar dates (author). 34 refs.; 4 figs.; 3 tabs

  11. The Pikes Peak batholith, Colorado front range, and a model for the origin of the gabbro-anorthosite-syenite-potassic granite suite

    Science.gov (United States)

    Barker, F.; Wones, D.R.; Sharp, W.N.; Desborough, G.A.

    1975-01-01

    This study of the Pikes Peak batholith includes the mineralogy and petrology of quartz syenite at West Creek and of fayalite-bearing and fayalite-free biotite granite near Mount Rosa; major element chemistry of the batholith; comparisons with similar postorogenic, intracratonic, sodic to potassic intrusives; and genesis of the batholith. The batholith is elongate in plan, 50 by 100 km, composite, and generally subalkalic. It was emplaced at shallow depth 1,040 m. y. ago, sharply transects its walls and may have breached its roof. Biotite granite and biotite-hornblende granite are predominant; quartz syenite, fayalite granite and riebeckite granite are present in minor amounts. Fayalite-bearing and fayalite-free quartz syenite, fayalite-biotite granite and riebeckite granite show a well-defined sodic differentiation trend; the less sodic fayalite-free granites exhibit a broader compositional range and no sharp trends. Crystallization was largely at PH2O suite that includes gabbro or basalt, anorthosite, quartz syenite, fayalite granite, riebeckite granite, and biotite and/or hornblende granites is of worldwide occurrence. A model is proposed in which mantle-derived, convecting alkali olivine basaltic magma first reacts with K2O-poor lower crust of granulite facies to produce magma of quartz syenitic composition. The syenitic liquid in turn reacts with granodioritic to granitic intermediate crust of amphibolite facies to produce the predominant fayalite-free biotite and biotite-hornblende granites of the batholith. This reaction of magma and roof involves both partial melting and the reconstitution and precipitation of refractory phases, as Bowen proposed. Intermediate liquids include MgO-depleted and Na2O-enriched gabbro, which precipitated anorthosite, and alkali diorite. The heat source is the basaltic magma; the heat required for partial melting of the roof is supplied largely by heats of crystallization of phases that settle out of the liquid - mostly olivine

  12. Geochemistry and petrology of mafic enclaves of metasedimentary origin: case study from the Peninsular Ranges Batholith, California

    Science.gov (United States)

    Liao, K.; Morton, D.; Lee, C.

    2011-12-01

    Dark clasts rich in amphibole or biotite, commonly referred to as "mafic enclaves", are frequently found in felsic plutons and are traditionally interpreted to represent fragments of mafic magmas, such as basalt, entrained by or intruded into felsic magma bodies. However, during emplacement, magmas often assimilate pre-existing wallrock, begging the question of whether some dark enclaves might have non-igneous protoliths. To investigate this process of forming dark enclaves in more detail, we examined the Cretaceous Domenigoni Valley pluton in the Peninsular Ranges Batholith in southern California. This pluton was emplaced into pre-existing metamorphic country rock, composed of Paleozoic to early Mesozoic calc-silicates, phyllites, and calcareous quartzites. Dark enclaves, in the form of amphibole- or biotite-bearing angular fragments, are abundant in the pluton. However, evidence for wallrock stoping is also seen in the extensive presence of wallrock xenoliths in varying extents of thermal and chemical equilibration with the host tonalite pluton. Enclaves with a clear calc-silicate protolith are represented by quartz-diopside-wollastonite-plagioclase rocks, whereas enclaves with clear pelitic protoliths are represented by biotite-quartz-alkali feldspar rocks. Several lines of evidence, however, suggest that the dark amphibole-rich and biotite-rich enclaves, although mafic in composition (high Mg and Fe), represent the fully equilibrated state of these assimilated wallrocks rather than fragments of basaltic magmas. First, many of the dark, biotite- and amphibole-bearing enclaves have SiO2 contents greater than 60 %, too high to represent typical mafic magmas. Second, although some biotite-rich enclaves have SiO2 contents dark amphibole-bearing enclaves have bulk Al and K lower than the host tonalite but similar to the quartz-diopside-wollastonite-plagioclase rocks thought to have a calc-silicate protolith. Fourth, composite enclaves exist wherein hornblende

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

    Science.gov (United States)

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

    2011-01-01

    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.

  14. The key role of mica during igneous concentration of tantalum

    Science.gov (United States)

    Stepanov, Aleksandr; A. Mavrogenes, John; Meffre, Sebastien; Davidson, Paul

    2014-06-01

    Igneous rocks with high Ta concentrations share a number of similarities such as high Ta/Nb, low Ti, LREE and Zr concentrations and granitic compositions. These features can be traced through fractionated granitic series. Formation of Ta-rich melts begins with anatexis in the presence of residual biotite, followed by magmatic crystallization of biotite and muscovite. Crystallization of biotite and muscovite increases Ta/Nb and reduces the Ti content of the melt. Titanium-bearing oxides such as rutile and titanite are enriched in Ta and have the potential to deplete Ta at early stages of fractionation. However, mica crystallization suppresses their saturation and allows Ta to increase in the melt. Saturation with respect to Ta and Nb minerals occurs at the latest stages of magmatic crystallization, and columbite can originate from recrystallization of mica. We propose a model for prediction of intrusion fertility for Ta.

  15. An identification study of vermiculites and micas. Adsorption of metal ions in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Alexandre-Franco, Maria; Gomez-Serrano, Vicente [Extremadura Univ., Badajoz (Spain). Dept. doe Quimica Organica e Inorganica; Albarran-Liso, Angel [Extremadura Univ., Badajoz (Spain). Escuela de Ingenieros Agronomos

    2011-02-15

    This study deals with the identification of vermiculite in the presence of mica. Three natural silicates were first subjected to expansion by rapid heat treated at 400 C. Then, the starting silicates and their derived heat-treated products were analyzed by X-ray diffraction, FT-IR spectroscopy, N{sub 2} adsorption at - 196 C, and helium density measurement. The adsorption of cadmium, chromium, and lead was also carried out. Two of the silicates are composed of mainly biotite and the other of biotite and vermiculite. In general, the results of X-ray diffraction, FT-IR spectroscopy, and helium density measurements are well in agreement. The heat treatment at 400 C has little effect on the chemical composition, structure, and texture of the silicates. The development of microporosity is small in the silicates. Surprisingly, the adsorption capacity toward chromium and lead is larger for the biotite silicate than for the vermiculite containing silicate. (author)

  16. Mineralogy, geochemistry, and genesis of high-alumina fenites of the Mont Saint-Hilaire alkaline pluton, Québec, Canada

    Science.gov (United States)

    Yakovleva, O. S.; Pekov, I. V.; Horváth, L.; Bryzgalov, I. A.; Yapaskurt, V. O.; Guseva, E. V.

    2010-12-01

    High-alumina fenites in the Mont Saint-Hilaire alkaline complex, Québec, Canada, form bodies at the contact of peralkaline nepheline syenite. Fenites are subdivided into four types: corundum-spessartine-biotite-feldspar, muscovite-corundum-hercynite-biotite-feldspar, carbonated muscovite-biotite-hercynite-feldspar, and spessartine-hercynite-feldspar. Accessory minerals of the ilmenite-pyrophanite series, columbites, zircon, thorite, pyrrhotite, Fe, Mn, Mg, Ca, Ba, and REE carbonates, uedaite-(Ce), etc. are identified. Three stages are suggested in the formation of these rocks. In mineralogy and geochemistry, the Mont Saint-Hilaire high-alumina fenites are similar to Al-rich fenites replacing xenoliths in the Khibiny alkaline complex, Russia. In both cases, fenites are related to peralkaline rocks and replace high-alumina protoliths: granite at Mont Saint-Hilaire and metapelites in the Khibiny Mountains. These fenites are regarded as a specific type of fenites with rock-forming Mg-depleted hercynite.

  17. Petrology and U-Pb geochronology of buried Avalonian plutonic rocks on southeastern Cape Cod

    Science.gov (United States)

    Leo, G.W.; Mortensen, J.K.; Barreiro, B.; Phillips, J.D.

    1993-01-01

    Plutonic rocks have been intersected by two separate drill holes on souteastern Cape Cod. Hole CC2 is located about 7 km south of the Nauset anomaly, an east-northeast-trending magnetic lineament that was considered to separate the distinct plutonic zones of Avalon terrane. This drill hole intersected weakly foliated, fairly homogeneous biotite granite. Zircons from this granite give a U-Pb age of 584+9/-8 Ma. Hole CC1 is located about 12 km north of the Nauset anomaly. The drill core intersected foliated, sheared, biotite granodiorite and biotite-hornblende-clinopyroxene-quartz gabbro, metamorphosed to greenschist facies. The deformed and altered state of these rocks, as well as their geochemistry, suggest that their origin and possibly their ages are distinct from the granite in hole CC2. No datable zircons were obtained from rocks in CC1. -from Authors

  18. Mineral Chemistry and Pressure and Temperature Estimates of Metasedimentary Rocks of the Araxá Group in the Region of Morrinhos, South of Goiás State

    Directory of Open Access Journals (Sweden)

    Guillermo Rafael Beltran Navarro

    2011-08-01

    Full Text Available In the Morrinhos region, Goiás state, Brazil, the rocks of the Araxá Group have mineral assemblages related to themetamorphic peak which occurred in this region and is typical of the amphibolite facies (kyanite zone. These rocks areassociated with the initial stage of the main ductile deformation that occurred in this area. Thermobarometric calculations,including the associations, garnet + plagioclase + biotite + muscovite; garnet + plagioclase +biotite + muscovite + kyanite;garnet + plagioclase + biotite + muscovite + amphibole, with quartz in excess, indicate that the metamorphic peak occurredat temperatures of approximately 610ºC and pressures in the order of 10 kbar. The P-T path is probably clockwise and is inagreement with the tectonic conditions observed in collisional settings.

  19. Geochemistry and Geochronology U-Pb SHRIMP of granites from Peixoto de Azevedo: Alta Floresta Gold Province; Geoquimica e geocronologia U-Pb (SHRIMP) de granitos da regiao de Peixoto de Azevedo: Provincia Aurifera Alta Floresta, MT

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Fernanda Rodrigues da; Barros, Marcia Aparecida Sant' Ana; Pierosan, Ronaldo; Pinho, Francisco Edigio Cavalcante; Tavares, Carla; Rocha, Jhonattan, E-mail: geologia.fernanda@gmail.com, E-mail: mapabarros@yahoo.com, E-mail: ronaldo.pierosan@gmail.com.br, E-mail: aguapei@yahoo.com, E-mail: carlageologia@hotmail.com, E-mail: geologojrocha@live.com [Universidade Federal de Mato Grosso (UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra; Rocha, Mara Luiza Barros Pita; Vasconcelos, Bruno Rodrigo; Dezula, Samantha Evelyn Max, E-mail: marapita1@yahoo.com.br, E-mail: brunovasc@gmail.com, E-mail: samanthadezula@gmail.com [Universidade de Brasilia (UNB), Brasilia, DF (Brazil). Programa de Pos-Graduacao em Geologia

    2014-09-15

    The analysis of petrographic, geochemical and geochronological data of granites in the Peixoto de Azevedo region, Mato Grosso, Brazil, in the eastern portion of the Alta Floresta Gold Province, led to the recognition of two granitic bodies bounded by regional major faults and shear zones. In the northwestern portion a body with featured as biotite granodiorite, coarse-grained, with porphyritic to inequigranular texture, metaluminous to peraluminous, high-K calc-alkaline and magnesium character. In the southeastern portion of the area, a biotite monzogranite coarse-grained, with equigranular to porphyritic texture, slightly peraluminous, high-K calc-alkaline and dominantly of ferrous character. U- Pb dating (SHRIMP) showed that the biotite monzogranite has an age of 1869 ± 10 Ma, similar to the Matupa Intrusive Suite, while the biotite granodiorite has an age of 1781 ± 10 Ma, that is the age expected to Peixoto Granite. Both units show patterns of rare earth elements with enrichment of light over heavy and negative Eu anomaly (La{sub N}/Yb{sub N} » 7.6 to 17.31 and ratios Eu/EU{sup ⁎} between 0.46 – 0.72 for biotite monzogranite and La{sub N}/Yb{sub N} » 7.13 to 29.09 with ratios Eu/Eu{sup ⁎} between 0.25 - 0.40 for the biotite granodiorite). Trace elements pattern for both present negative anomalies of Ba, P, Ti and Nb indicating an evolution from mineral fractionation and subduction related sources. In this paper, it is suggested that the monzogranite Matupa was developed in mature arc tectonic environment. For the Peixoto Granite, two hypotheses are suggested: (a) it was developed in younger magmatic arc environment associated with the Colider Magmatism or (b) it was generated in extensional tectonic environment during the Columbia Super continent break up. (author)

  20. First direct radiometric dating of the Tortonian/Messinian boundary

    International Nuclear Information System (INIS)

    New volcanogenic layers found in the Northern Appennines of Romagna at the Tortonian/Messinian transition have been dated. The Globorotalia suterae FAD yielded a date of 7.72±0.15 Ma (K/Ar on biotites). The boundary taken as the Globorotalia conomiozea FAD is closely predated by 7.33 Ma (K/Ar on biotite and 39Ar/40Ar on plagioclase). An age of 7.26±0.10 Ma for the boundary is suggested. There are appropriate conditions for placing here the related Global Stratotype Section and Point

  1. An oxygen buffer for some peraluminous granites and metamorphic rocks.

    Science.gov (United States)

    Zen, E.

    1985-01-01

    The mineral assemblage biotite-garnet-muscovite-magnetite-quartz and its sub-sets are common in many peraluminous granites, schists and gneisses. If the biotite and garnet are reasonably iron-rich, then the system is a useful buffer for fO2. Available thermochemical data indicate that, in T-fO2 space, the buffer curve is located between the hematite-magnetite curve and the quartz-magnetite-fayalite curve, in a region that previously had no buffer curve applicable to peraluminous rocks. -J.A.Z.

  2. Chemical migration by contact metamorphism between pegmatite/country rocks: natural analogs for radionuclides migration

    International Nuclear Information System (INIS)

    Comparison of trace element signatures of country rocks as a function of distance from the contact with two pegmatites, Tin Mountain and Etta, in the Black Hills of South Dakota, suggests that some elements such as K, Li, Rb, Cs, As, Sb, Zn and Pb, have migrated to distances of 4 to 40 meters during contact metamorphism. The relative degree of migration varies depending on the element. On the other hand, there is virtually no migration of rare earth elements (REE), Al, Sc, Cr, Hf, U, and Th. Biotite and muscovite are effective trace element traps for Li, Rb and Cs. Biotite has a greater affinity for Rb, Cs and Li than muscovite

  3. Crystallochemical transformation of phyllosilicates under the impact of cyanobacteria and actinomycetes

    Science.gov (United States)

    Chizhikova, N. P.; Omarova, E. O.; Lobakova, E. S.; Zenova, G. M.; Manucharov, A. S.

    2009-01-01

    The transformation of the crystallochemical structure of phyllosilicates (vermiculite and biotite) under the impact of growing cyanobacterial and actinomycetal associations, as well as monocultures of cyanobacteria and actinomycetes, has been studied. The character of the mineral transformation depends on their crystallochemical structure and the type of biota. The most significant changes take place in the contact zone between minerals and microbial associations; the effect of microbial monocultures is smaller. The transformation of biotite proceeds via the stage of ordered mica-vermiculite (smectite) neoformation (rectorite); the destruction of vermiculite has been identified.

  4. Geochronology and geochemistry of the Early Cretaceous Jigongshan and Qijianfeng batholiths in the Tongbai orogen, central China: implications for lower crustal delamination

    Science.gov (United States)

    Zhang, Jinyang; Ma, Changqian; Li, Jianwei; She, Zhenbing; Zhang, Chao

    2013-06-01

    The Jigongshan and Qijianfeng batholiths in the Tongbai orogen consist mainly of porphyritic hornblende-biotite monzogranite, biotite monzogranite, and biotite syenogranite, which are variably intruded by lamprophyre, diorite, and syenogranite dykes. Mafic microgranular enclaves commonly occur in the hornblende-biotite monzogranite, whereas surmicaceous enclaves are found in the biotite monzogranite. Both batholiths have zircon U-Pb ages ranging from ca. 139 to 120 Ma, indicating their emplacement in the Early Cretaceous. The hornblende-biotite monzogranite has an adakitic affinity marked by relatively high Sr/Y and (La/Yb) N ratios, lack of Eu anomalies, low MgO and Ni contents, and Na2O > K2O. Its chemical compositions, combined with enriched Sr-Nd isotopic signatures, suggest formation by dehydration melting of mafic rocks in a thickened lower crust. This thickened crust resulted from the Permo-Triassic subduction-collision between the North China and South China blocks and persisted until the Early Cretaceous. The biotite monzogranite and biotite syenogranite have low Al2O3, CaO, and Sr contents, low Rb/Sr, FeOt/MgO, and (Na2O + K2O)/CaO ratios, and flat HREE patterns with moderate to weak Eu anomalies. They were produced by partial melting of crustal materials under relatively low pressure. Partial melting at different crustal levels could have significantly contributed to mechanical weakening of the crust. The diorite and lamprophyre dykes show linear trends between SiO2 and major or trace elements on Harker diagrams, with two lamprophyre samples containing normative nepheline and olivine. These rocks have high La/Yb and Dy/Yb ratios, both displaying co-variation with contents of Yb. They were originated from relatively deep lithospheric mantle followed by fractionation of olivine + clinopyroxene + apatite + Fe-Ti oxides. Extensive partial melting in the lithospheric mantle indicates relatively high temperatures at this level. We suggest that the presence of

  5. Evidence of Himalayan erosional event at approx. 0.5 Ma from a sediment core from the equatorial Indian Ocean in the vicinityof ODP Leg 116 sites

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Gupta, S.M.; Mislankar, P.G.; Rao, B.R.; Parthiban, G.; Roelandts, I.; Patil, S.K.

    changes, shifts in depocentres between distal and proximal basins,internal lobeswitching, etc. (e.g. France-Lanord and Derry, 1997). From the seismic studies in the Bengal Fan in a transect running from ODP 116 in the distal part to DSDP Leg 22... contain abundant quantities of biotite and muscovite (C2430%; Sorkhabi et al., 1993, 1996; Derryand Fig. 6. SEM photos of (A) biotite, (B) muscovite and (C) quartz. France-Lanord, 1996), and simplified composition of the HHC rocks would be quartz, feldspar...

  6. Evaluation of geochronologic data from Granja Complex (CE, Brazil)

    International Nuclear Information System (INIS)

    This paper describes the geochronological data of Chaval Granitoid and the reinterpretation of the geological evolution of Granja Complex. The Chaval Granitoid, situated on the peak of Granja Complex, gave the Rb/Sr isochronic age of 507±27 Ma for initial ratio of 0,70557±0,00013. The Granja Complex area, characterized by a significant lithological alteration was dating with k/Ar in isolated minerals, giving 566±17 Ma for migmatite, (hornblend), 429±13 Ma for gneisses, (biotite), 627±19 Ma for granite (hornblende) and 512±15 Ma for granite (biotite). (C.G.C.)

  7. Weathering of the Rio Blanco Quartz Diorite, Luquillo Mountains, Puerto Rico: Coupling Oxidation, Dissolution, And Fracturing

    International Nuclear Information System (INIS)

    In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2-2 m thick zone of partially weathered rock layers (∼2.5 cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive ΔV of reaction builds up elastic strain energy. The rates of spheroidal fracturing and saprolite formation are therefore controlled by the rate of the weathering reaction. Chemical, petrographic, and spectroscopic evidence demonstrates that biotite oxidation is the most likely fracture-inducing reaction. This reaction occurs with an expansion in d (0 0 1) from 10.0 to 10.5 (angstrom), forming 'altered biotite'. Progressive biotite oxidation across the rindlet zone was inferred from thin sections and gradients in K and Fe(II). Using the gradient in Fe(II) and constraints based on cosmogenic age dates, we calculated a biotite oxidation reaction rate of 8.2 x 10-14 mol biotite m-2 s-1. Biotite oxidation was documented within the bedrock corestone by synchrotron X-ray microprobe fluorescence imaging and XANES. X-ray microprobe images of Fe(II) and Fe(III) at 2 (micro)m resolution revealed that oxidized zones within individual biotite crystals are the first evidence of alteration of the otherwise unaltered corestone. Fluids entering along fractures lead to the dissolution of plagioclase within the rindlet zone. Within 7 cm surrounding the rindlet-saprolite interface, hornblende dissolves to completion at a rate of 6.3 x 10-13 mol hornblende m-2 s-1: the fastest reported rate of hornblende weathering in the field. This rate is consistent with laboratory-derived hornblende dissolution rates. By revealing the coupling of these mineral weathering reactions to fracturing and porosity formation we are able to describe the process by which the quartz diorite bedrock disaggregates and forms saprolite. In the corestone

  8. Isotopic characteristics of two kinds of hydrothermal carbonation in the Maria Lazara gold deposit. Goias Estate of Central Brazil

    International Nuclear Information System (INIS)

    In the hydrothermal halo of the Maria Lazara gold deposit, two kinds of carbonation were identified: pervasive carbonation, which corresponds to the disseminations of calcite in the hydrothermal halo represented by the biotite-sulfide and carbonate-chlorite zones and, venular carbonation expressed by quartz and calcite veins inserted in the inner biotite-sulfide zone show an organic carbon component depleted in C. In the carbonate-chlorite zone the calcite isotopic behavior reflects the Co2 derived from the metamorphism o the basic host-rocks. (author)

  9. Regional elevation history from Ribeira belt based in K-Ar dating

    International Nuclear Information System (INIS)

    The Ribeira orogenic belt, Brazilian cycle in metamorphism, has biotite K-Ar ages becoming young from the border (600 Ma) to the central axis (450 Ma), these ages are not related to rock type nor intrusive phase, but to occurrence area. The fact suggests that this wide-ranging age distribution is not due to later thermal events, e.g. post tectonic intrusion, but to slow cooling on the axis zone. The climax metamorphic condition have been estimated as 675 sup(0)C and 4 to 5 kb (18 km's depth). This temperature is much higher than that of biotite argon retention (310 sup(0)C). These data indicate that the biotite K-Ar clock have been set fairly after the climax during regional uplift at a depth much shallower that the metamorphism. Biotite clock setting depth (310 sup(0)C) is calculated as 7.5 km, using geothermal gradient of 30 sup(0)C/km. In this connection, uplift of 11.5 km from 600 Ma to 450 Ma (rate of 77 m/m.y.) is estimated. Fission track datings in apatite (110 Ma), combined with a present geothermal gradient (25 sup(0)C/km) indicate uplift of 3.5 km from 450 Ma to 110 Ma (16 m/m.y.) and 4 km from 110 Ma to the present (35 m/m.y.). (author)

  10. A polyphase metamorphic evolution for the Xitieshan paragneiss of the north Qaidam UHP metamorphic belt, western China: In-situ EMP monazite- and U-Pb zircon SHRIMP dating

    NARCIS (Netherlands)

    Zhang, C.; Roermund, H.L.M. van; Zhang, L.; Spiers, C.

    2012-01-01

    In-situ electron microprobe (EMP) U–Th–Pbmonazite-, sensitive high-resolution ion microprobe (SHRIMP) zircon analyses, metamorphic phase equilibrium (Domino/Theriak)- and geothermobarometric calculations are performed on kyanite/sillimanite-bearing garnet biotite gneisses forming part of the dominan

  11. Rb-Sr age and K-Ar age of the Takai pegmatite, Nara Prefecture, Japan

    International Nuclear Information System (INIS)

    The Rb-Sr and the K-Ar ages were determined for biotite, muscovite and K-feldspar collected from the Takai pegmatite, Nara Prefecture. The pegmatite is a largescaled one and occurs in the Ryoke metamorphic terrain intruding basic metamorphic rocks. The Rb-Sr ages are 73.9 m.y. for biotite, 75.0 m.y. for muscovite and 75.7 m.y. for K-feldspar, while the K-Ar ages are 73.6 m.y. for biotite, 70.3 m.y. for muscovite and 70.0 m.y. for K-feldspar. Thus, the Rb-Sr and the K-Ar ages are not concordant, except for biotite. The younger K-Ar ages for both mulcovite and K-feldspar suggest that Ar diffusion continued after the ceasing of Sr diffusion. The concordant Rb-Sr ages for muscovite and K-feldspar may indicate the time of the formation of the pegmatite. This result suggests that the plutonic activity which occurred in the Ryoke metamorphic terrain in the Kinki district ceased approximately 75 m.y. ago. (author)

  12. Geological characteristics and prospective analysis of uranium-producing pegmatites in lushi, western henan province

    International Nuclear Information System (INIS)

    Two small pegmatite-type uranium deposits and lots of uranium mineralization are found in Shangdan triangle area in Shaanxi Qinling group strata. In western Henan, Huichizi rock extend eastward from the Shaanxi to Huangbogou-Qima river-Limanping area. Huichizi rock in the Qinling group is controlled by Shangdan and Zhixia fracture zone. Qinling group is a set of deep metamorphic rocks. Huichizi rock is I type granite rock. Pegmatite is divided into three types of uranium mineralization: biotite pegmatite, two-mica pegmatite and muscovite pegmatite. Around the rock, the distribution of pegmatites have horizontal and vertical zonation. The rock within the zone is biotite pegmatites, away from rock distribution muscovite pegmatites, between two-mica pegmatites. Biotite pegmatites REE produced in the Caledonian is a light rare earth-based, with strong Eu depletion, chemical characteristics of rocks with high silica (73%), alkali-rich, K> Na, poor Fe, Mn, Mg, Ca. Accessory mineral assemblages are ilmenite-Monazite-uraninite. Crystalline uranium aged in 426 Ma mainly distributed in pegmatites of biotite or rare earth. Huichzi rock in some Henan pegmatites have good prospects of uranium, mineralization. Especially in Limanping, Qima river and Huangbguo Lushi county, Uranium resources are rich. (authors)

  13. Geology and associated mineral occurrences of the Araxa Group, Mossamedes Region, Goias, Brazil

    International Nuclear Information System (INIS)

    In the region of Mossamedes, State of Goias, Brazil, the Precambrian metamorphic rocks of the Araxa group were mapped at the scale of 1:25,000, with emphasis on stratigraphic, structural, petrographic and economic aspects. These metamorphites represent a continous stratigraphic sequence which, from bottom to top can be subdivided into five informal lithostratigraphic units: 1) psamitic unit (quartzite, metaconglomerate); 2) psamitic-pelitic unit (quartzite, quartz schist, muscovite schist); 3) lower pelitic - volcanic unit (chlorite - biotite schist, fine grained blastoporphyritic gneiss, amphibolite and calc-schist); 4) upper pelitic - volcanic unit (garnet muscovite schist, biotite schist and gneiss, amphibolite, magnetite muscovite schist); 5) gneissic unit (epidote biotite gneiss, amphibolite). Three types of meta-intrusive rocks were found, besides basic dykes related to Mesozoic magmatism. Four phases of deformation affected the volcano-sedimentary sequence;D1, D2, D3 and D4, each of them developing distinct deformational features. Barrowian type metamorphism increases progressively from North to South from the biotite zone to the garnet zone (greenschist facies), reaching the staurolite-kyanite zone (amphibolite facies). The magmatism throughout the Group's evolution consists of mafic to felsic volcanic activity, mustly intermediary, as well as three intrusive events. Gold, copper and zinc minerals of economic interest occur within the studied area. The gold mineralizations are related to the pelitic-volcanic sequences. Copper occurs in several rocks from the pelitic-volcanic and gneissic sequences. (Author)

  14. Geochronologic study of polycyclic rocks from Sao Vicente complex in anticlinorium of Caico and Florania - RN, Brazil

    International Nuclear Information System (INIS)

    The characterization of geochronologic standard in a polycyclic area, verifying the interpretative potentials of Rubidium-Strontium and Potassium-Argon methods is the main objective of this paper. The determinations of K/Ar were made in amphiboles, moscovites and biotites. Petrology studies were also made for verifying the composition of several lithological types. (author)

  15. Manganese Biogeochemistry in a Central Czech Republic Catchment

    Czech Academy of Sciences Publication Activity Database

    Navrátil, Tomáš; Shanley, J. B.; Krám, P.; Mihaljevič, M.; Drahota, Petr

    2007-01-01

    Roč. 186, 1-4 (2007), s. 149-165. ISSN 0049-6979 R&D Projects: GA ČR GA205/04/0060 Institutional research plan: CEZ:AV0Z30130516 Keywords : manganese * catchment * weathering * biogeochemistry * biotite weathering * forest ecosystem * mass balance Subject RIV: DD - Geochemistry Impact factor: 1.224, year: 2007

  16. Las rocas básicas de Monte Castelo (La Coruña)

    NARCIS (Netherlands)

    Warnaars, F.W.

    1967-01-01

    A gabbroic complex is found 30 km to the North of Santiago de Compostela, Galicia. It turns out to be a multiple intrusion of different sills with a North-South trend. The borders of the sills are indicated by the occurrence of biotite and garnet, and sometimes xenoliths were found. Reaction-equatio

  17. Delineation of structures favourable to groundwater occurrence employing seismic refraction method — A case study from Tiruvuru, Krishna district, Andhra Pradesh

    Indian Academy of Sciences (India)

    N Sundararajan; Y Srinivas; M Narasimha Chary; G Nandakumar; A Hanmantha Chary

    2004-09-01

    The contacts associated with an outlier in biotite gneiss and sandstones near Tiruvuru, Krishna district, Andhra Pradesh which are generally favourable for groundwater occurrence were investigated employing refraction seismic method. Results were examined by correlating the signals with local geology, bore well data and other available information in order to improve the reliability of interpretation.

  18. Differences of granitic weathering at the northern and southern feet of Dabie Mountains, Central China: Implication for tectonic and climatic environments

    Institute of Scientific and Technical Information of China (English)

    XU; Haijin(续海金); MA; Changqian(马昌前); LIU; Fan(刘凡); YANG; Kunguang(杨坤光)

    2003-01-01

    Two weathering profiles of Yanshanian granites on the southern and northern feet of the Dabie Mountains were investigated. The results showed that, on the southern foot of the Dabie Mountains, the weathering profile of the Sikongshan biotite monzonitic granite was eroded with remarkable loss of alkila, calcium and silicon, and richness of aluminium during hydrolysis process and in acidic mediums. Feldspar and biotite, major rock-forming minerals, were altered to illite→(vermiculite→1.4 nm transition minerals) →kaolinite→halloysite. However, on the northern foot of the Dabie Mountains, the Hepeng biotite orthogranite weathering profile was stable, without silicon depletion, but with remarkably enriched iron and noncrystalline during oxidizing process and in feebly acidic-neutral mediums. The major rock-forming minerals such as feldspar and biotite in the Hepeng weathering profile were weathered to smectites and halloysite→noncrystalline. The above results reveal that weathering differences of the granites between southern and northern feet of the Dabie Mountains may be related to climatic environments and tectonic movements. The southern foot, in hot and rainy environments, was uplifted by tectonics and was intensively leached. The soils in the southern slope were under acidic conditions. In contrast, the northern foot was slightly leached in hot and droughty environments, and the soils were under feebly acidic-neutral conditions.

  19. Radioelemental, petrological and geochemical characterization of the Bundelkhand craton, central India: implication in the Archaean geodynamic evolution

    Science.gov (United States)

    Ray, Labani; Nagaraju, P.; Singh, S. P.; Ravi, G.; Roy, Sukanta

    2016-06-01

    We have carried out radioelemental (232Th, 238U, 40K), petrological and geochemical analyses on granitoids and gneisses covering major rock formations of the Bundelkhand craton, central India. Our data reveal that above characteristics are distinct among granitoids (i.e. pink, biotite and grey granitoids) and gneisses (i.e. potassic and sodic types). Pink granitoid is K-feldspar-rich and meta-aluminous to per-aluminous in character. Biotite granitoid is meta-aluminous in character. Grey granitoid is rich in Na-feldspar and mafic minerals, granodiorite to diorite in composition and meta-aluminous in character. Among these granitoids, radioelements (Th, U, K) are highest in pink granitoid (45.0 ± 21.7 ppm, 7.2 ± 3.4 ppm, 4.2 ± 0.4 %), intermediate in biotite granitoid (44.5 ± 28.2 ppm, 5.4 ± 2.8 ppm, 3.4 ± 0.7 %) and lowest in grey granitoid (17.7 ± 4.3 ppm, 4.4 ± 0.6 ppm, 3.0 ± 0.4 %). Among gneisses, potassic-type gneisses have higher radioelements (11.8 ± 5.3 ppm, 3.1 ± 1.2 ppm, 2.0 ± 0.5 %) than the sodic-type gneisses (5.6 ± 2.8 ppm, 1.3 ± 0.5 ppm, 1.4 ± 0.7 %). Moreover, the pink granitoid and the biotite granitoid have higher Th/U (6 and 8, respectively) compared to the grey granitoid (Th/U: 4), implying enrichment of Th in pink and biotite granitoids relative to grey granitoid. K/U among pink, biotite and grey granitoids shows little variation (0.6 × 104, 0.6 × 104, 0.7 × 104, respectively), indicating relatively similar increase in K and U. Therefore, mineralogical and petrological data along with radioelemental ratios suggest that radioelemental variations in these lithounits are mainly related to abundances of the radioactive minerals that have formed by the fractionation of LILE from different magma sources. Based on present data, the craton can be divided into three distinct zones that can be correlated with its evolution in time and space. The central part, where gneisses are associated with metavolcanics of greenstone belt, is

  20. Further support for a Cretaceous age for the feathered-dinosaur beds of Liaoning,China:New 40Ar/39Ar dating of the Yixian and Tuchengzi Formations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We report new 40Ar/39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar/39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation.The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar/39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca/K ratios, excellent reproducibility and gave a mean age of 125.0 ± 0.18 (1SD) ±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar/39Aranalyses of the Hengdaozi tuff gave a mean age of 125.0 +0.19 (1SD) ± 0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4 ± 0.19 (1SD) ± 0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.``

  1. Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre : implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand

    International Nuclear Information System (INIS)

    The Mangakino Volcanic Centre is the westernmost and oldest rhyolitic caldera volcano in the Taupo Volcanic Zone, North Island, New Zealand. The largest eruptions from Mangakino occurred in two periods of caldera-forming activity during the 1.68-1.53 Ma (Period I), and 1.21-0.95 Ma (Period IIA), producing several voluminous widespread welded and nonwelded ignimbrites and minor fall deposits. Other activity from Mangakino generated fall deposits and rhyolitic lava domes. Lithic fragments are common in all Mangakino ignimbrites (1-10 modal %), and consist of diverse lithologies including: rhyolite, dacite, andesite, and basaltic andesite lava, welded ignimbrite, tuff, volcanic breccia, biotite granite, granodiorite porphyry, siltstone, sandstone, greywacke, metagreywacke, metaconglomerate, biotite and hornblende-biotite schist. Lithic populations in Period I ignimbrites are dominated by andesite lavas, suggesting that there was a pre-existing andesite volcano in the Mangakino area, geochemically distinct from Titiraupenga and Pureora, the nearest roughly contemporaneous andesitic volcanoes. Later ignimbrites that erupted during Period IIA, contain predominantly rhyolitic lava lithics, implying that significant dome building activity occurred at Mangakino, which represented greater volumes of rhyolitic lava than previously described from the area. Petrographic, geochemical, and geophysical (density and magnetic susceptibility) data measured from the lithic fragments are used to propose a model for the shallow crust below Mangakino Volcanic Centre. This model postulates eruptions through a basement of Mesozoic biotite schists overlain by metagreywackes, a thin cover of Tertiary sandstones and siltsones, and an overlying volcanic succession of andesite, dacite and rhyolite lavas, welded ignimbrites, and lacustrine sediments. Ignimbrite eruptions incorporated comagmatic biotite granite fragments from the crystallised margins of the silicic magma chambers, and effectively

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

    Directory of Open Access Journals (Sweden)

    Robabeh Jafari

    2010-05-01

    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.

  3. Primary uranium sources for sedimentary-hosted uranium deposits in NE China: insight from basement igneous rocks of the Erlian Basin

    Science.gov (United States)

    Bonnetti, Christophe; Cuney, Michel; Bourlange, Sylvain; Deloule, Etienne; Poujol, Marc; Liu, Xiaodong; Peng, Yunbiao; Yang, Jianxing

    2016-05-01

    Carboniferous-Permian, Triassic and Jurassic igneous basement rocks around the Erlian Basin in northeast China have been investigated through detailed mineralogical, whole-rock geochemistry, geochronological data and Sm-Nd isotope studies. Carboniferous-Permian biotite granites and volcanic rocks belong to a calc-alkaline association and were emplaced during the Late Carboniferous-Early Permian (313 ± 1-286 ± 2 Ma). These rocks are characterised by positive ɛNd(t) (3.3-5.3) and fairly young T DM model ages (485-726 Ma), suggesting a dominant derivation from partial melting of earlier emplaced juvenile source rocks. Triassic biotite granites belong to a high-K calc-alkaline association and were emplaced during the Middle Triassic (243 ± 3-233 ± 2 Ma). Their negative ɛNd(t) (-2 to -0.1) and higher T DM model ages (703-893 Ma) suggest a contribution from Precambrian crust during the magma generation processes, leading to a strong enrichment in K and incompatible elements such as Th and U. Highly fractionated magmas crystallised in U-rich biotite (up to 21 ppm U) and two-mica granites. In biotite granite, the major U-bearing minerals are uranothorite and allanite. They are strongly metamict and the major part of their uranium (90 %) has been released from the mineral structure and was available for leaching. Mass balance calculations show that the Triassic biotite granites may have, at least, liberated ˜14,000 t U/km3 and thus correspond to a major primary uranium source for the U deposits hosted in the Erlian Basin.

  4. Zircon U-Pb ages and geochemical characteristics of granitoids in Nagqu area, Tibet

    Science.gov (United States)

    Sun, Sai-Jun; Sun, Wei-Dong; Zhang, Li-Peng; Zhang, Rong-Qing; Li, Cong-Ying; Zhang, Hong; Hu, Yong-Bin; Zhang, Zhao-Rong

    2015-08-01

    This paper reports zircon LA-ICP-MS U-Pb ages and Hf-O isotopic ratios, and whole-rock major and trace element data of Early Cretaceous felsic intrusive rocks from Nagqu area, the northern Lhasa subterrane, southern Tibet. LA-ICP-MS zircon U-Pb dating of biotite granites and biotite monzogranites in the area yields magmatic crystallization ages of ca. 112 Ma, which suggests that they were emplaced in the late Early Cretaceous. Both rocks show high-K calc-alkaline to shoshonitic composition and slightly-moderately peraluminous signature. They are enriched in the alkalis, Rb, Th, K, U and light rare earth elements, depleted in Nb, Ta, Ti and P, and characterized by high Al2O3 contents (12-16 wt.%), high Rb/Sr ratios (1.3-33) and low Mg# values (15-39). Their magmatic zircons have negative εHf(t) values (from - 25.9 to 0.5) and high positive δ18O values (from 7.9‰ to 11.5‰). All the above characteristics indicate that Nagqu biotite monzogranites and biotite granites were likely derived from hybrid melts of sediments from the continent crust with minor mantle-derived input, then experienced varied degrees of fractional crystallization. The Nagqu intrusion is a component of the late Early Cretaceous magmatic flare-up event that occurred during ~ 120-100 Ma in the northern and partly central Lhasa subterranes. This magmatic flare-up is marked with a great compositional diversity (basalt, rhyolite, adakitic rocks, dioritic enclave, biotite monzogranite and granite) that might be caused by the slab breakoff of the southward subducting Bangong-Nujiang oceanic lithosphere, or more likely by slab window opening, which may have significantly contributed to juvenile crustal growth of the northern Lhasa subterrane.

  5. Retention of 137Cs and 90Sr by mineral sorbents surrounding vitrified nuclear waste

    International Nuclear Information System (INIS)

    In June 1960, twenty-five 14-cm diameter hemispheres of vitrified nuclear waste (glass blocks) were buried in a shallow sand aquifer in the lower Perch Lake Basin, Chalk River Nuclear Laboratories, Ontario, Canada. Almost all leaching of the glass blocks occurred during the first 18 months of emplacement, and consequently the burial experiment approximated a single-injection source of 137Cs and 90Sr. After about 11 years, most of the 90Sr that was released had been advected and dispersed from the site, whereas the bulk of the 137Cs had travelled no more than 0.3 m from the blocks. Three piezometers were installed and five cores of sediment were collected at the glass block site in 1978. Mineralogically pure segregates of sand grains were prepared by hand and characterized using binocular, petrographic and scanning electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. A technique also was developed to measure very low levels of 137Cs and 90Sr by counting small (10-100 mg) sediment samples directly with a thin window, flow proportional counter. Results show that sand-sized grains of altered biotite (biotite-vermiculite), biotite, muscovite, hornblende and serictized feldspar are able to retain 137Cs over a period of 18 years, and that grains of biotite-vermiculite, biotite and hematite-bearing feldspar (largely microline) can retain low levels of 90Sr over the same period of time. The amounts of 137Cs and 90Sr sorbed by the mineral grains ranged from undetectable levels to approximately 380 and 35 becquerels/gram sediment, respectively. This report contains the complete series of mineral segregates ranked on a weight basis according to the amounts of retained 137Cs and 90Sr. Ground-water quality data indicate that none of the retention is the result of the precipitation of strontium or cesium minerals

  6. Evidence of pre-Gondwana tectono-thermal event from the Bhilwara Supracrustal units of Rajasthan, north-west India

    Science.gov (United States)

    Saha, Lopamudra; Sarkar, Saheli; Rakshit, Nibedita; Nasipuri, Pritam

    2014-05-01

    In the Indian subcontinent, two pre- Gondwana (pre- Pan African) orogenies are mostly recorded and well-studied from the Eastern Ghat Mobile Belt: (i) >1.1 Ga and (ii) ~950 Ma. During the ~950Ma orogeny, the pre-existing granulites have been re-melted under granulite facies conditions at ~8 kbar, 800-850ºC in the sillimanite stability field with formation of garnet-orthopyroxene in the restites. In this study we report garnet-sillimanite bearing and garnet-staurolite-kyanite bearing supracrustal rocks from the Bhilwara Supergroup in Rajasthan, N-W India. Peak assemblage in the garnet-sillimanite bearing metapelite is: garnet-sillimanite-biotite-plagioclase-quartz. Garnet porphyroblasts contain sillimanite-biotite bearing inclusion trails. Matrix foliations consist of biotite, sillimanite, quartz. Peak pressure-temperature calculated for garnet formation are ~7-8 kbar, 800ºC. Garnet is replaced along the margins by biotite during retrogression. Within garnet-staurolite-kyanite schist, peak assemblage is formed of garnet-staurolite-biotite-kyanite quartz, where garnet and staurolite occur as porphyroclasts and the matrix foliations are formed of kyanite-biotite-quartz. Mineral assemblages and compositions in the rock indicate peak pressure-temperature >8 kbar, 600ºC. The ages of the metamorphic events at sillimanite and kyanite facies are not well-constrained. However since the Bhilwara supracrustal units occur close to the Grenvillian orogenic belt at Sandmata Complex, the timing of the peak metamorphism can be constrained at ~1.0 Ga. Garnet-sillimanite-bearing assemblages noted in the Bhilwara Supracrustal Belt, has also been noted from the Grenvillian belts in the Eastern Ghat Mobile Belt. So the question that needs to be addressed is whether the Grenvillian orogenic belt recorded form the Sandmata Complex in Rajasthan and that of the Eastern Ghat Belt had been a continuous orogenic belt? Such possibilities can be addressed by establishing detailed structural

  7. Geología y petrología de los granitoides del sur de la Sierra de Comechingones, Córdoba, Argetina

    Directory of Open Access Journals (Sweden)

    Otamendi, J. E.

    1992-12-01

    Full Text Available The petrography and petrology characteristics of a group of granitoid bodies from the crystalline basement of Southern Comechingones Hills, is described here.In the metamorphic Complex biotitic gneisses, anphibolites, marbles and metabasic rocks were recognized. The main metamorphic episode in this area reached high-temperature within medium grade conditions.These granitoid are: biotitic granites, leucogranites and gneissic granites.The biotitic granites, with biotite, apatite sillimanite and garnet, are elongate bodies, concordant with the main penetrative schistosity. Have medium to small grain, with an important foliation, shown by the lineation of micaceous minerals.The muscovite, garnet, tourmaline, dumortierite and biotite leucogranites have tabular shape, and an extension more than one kilometre.The gneissic granites are plutons that intruded concordant to the regional structural trend. Biotite, sillimanite, monacite and apatite minerals are characteristic of these rocks. Radimetric ages obtained in nearby areas, show that granitoids may be of Lower Paleozoic age.Geology and petrology characteristics of granitoids suggest that they may have been produced by partial melt of crustal metasedimentary rocks.Se describe la petrografía y petrología de los granitoides aflorantes en el basamento cristalino del sur de la Sierra de Comechingones.Dentro del complejo metamórfico regional predominan gneises biotíticos, paranfibolitas, mármoles y metabasitas. El evento metamórfico principal alcanzó condiciones de alta temperatura dentro del grado medio.Entre los granitoides se reconocieron los siguientes tipos litológicos: granitos biotíticos, leucogranitos y granitos gnéisicos.Los granitos biotíticos con apatito, sillimanita y granate conforman cuerpos elongados, concordantes con la esquistosidad penetrativa principal. Son de grano fino a medio, con marcada foliación, dada por la alineación de elementos micáceos.Los leucogranitos, cuyos

  8. Molybdenum mineralization at Alpeiner Scharte, Tyrol (Austria): results of in-situ U Pb zircon and Re Os molybdenite dating

    Science.gov (United States)

    Langthaler, K. J.; Raith, J. G.; Cornell, D. H.; Stein, H. J.; Melcher, F.

    2004-09-01

    Vein-type Mo mineralization at Alpeiner Scharte occurs in the Penninic units of the western Tauern Window in the Eastern Alps. Three types of previously undated metagranitoids (central gneisses) are distinguished and preserve intrusive contacts with pre-Alpine metamorphosed supracrustal rocks. The granitic protoliths represent fractionated late to post-orogenic, calc-alkaline, I-type magmas with minor S-type components. The Mo veins are restricted to a biotite and alkali feldspar-rich gneiss variety and occur in E W trending normally sub-vertical quartz veins with adjacent thin discontinuous garnet- and biotite-rich zones; the latter are interpreted as metamorphosed vein selvages. Prior to this work the age of the intrusive host rocks as well as the age of Mo mineralization were unknown.

  9. Occurrence of the radionuclides in groundwater of crystalline hard rocks regions of central part Tamil Nadu, India

    International Nuclear Information System (INIS)

    Samples were collected in hard rock region central parts of Tamilnadu, South India to assess the U and 222Rn levels in groundwater belonging to various lithologies and evaluate their correlations with other water quality parameters. The order of dominance of U in groundwater is; Granite> Charnockite> Fissile Hornblende biotite gneiss> Flood Plain Alluvium> Quartzite, while that of 222Rn is: Granite> Quartzite> Charnockite > Fissile Hornblende biotite gneiss> Flood Plain Alluvium. Both U and 222Rn concentrations were compared with drinking water standards and a few samples show levels above the permissible limits. High degree of weathering of granitic rocks and long contact time of groundwater with the aquifer matrix could be the reason for enhanced U and 222Rn levels in groundwater. (author)

  10. Microscopic studies of uranium mineralization at Mentawa Area, Central Kalimantan

    International Nuclear Information System (INIS)

    In Mentawa areas there are indications that the U mineralization associated with tourmaline, quartz, sulfide minerals that fill the fracture aperture, on the rocks meta silt, and fill it with the direction of WNW - ESE, the thickness milli metric - centi metric with radioactivity 500-15000 c/s SPP 2 NF. The purpose of this study is to know the characters. para geneses and the process of formation of uranium minerals. The method used by microscopic observation of several examples of thin sections and polished sections of the previous research results. The study shows that uranium minerals are uraninite, associated with molybdenite, magnetite, rutile, ilmenite, pyrite, pyrrhotite, tourmaline, garnet, quartz and mineral pitchblende associated with arsenopyrite, hematite, chalcopyrite, pyrite, pyrrhotite, tourmaline, quartz till in cracks in rocks biotite and biotite schist. Mineral associations indicate that the process of formation of uranium mineralization occurs in three phases: pegmatites pneumatolitic, and hydrothermal alteration. (author)

  11. 我国某地含褐钇钶矿碱性花岗岩的特征

    Institute of Scientific and Technical Information of China (English)

    康旭

    1975-01-01

    The fergusonite alkaline granite referred to in this paper is a complex consisting of acmite-augite riebeckite granite, riebeckite granite and biotite riebeckite granite. Its principal rock-forming minerals include acmite-augite, riebeckite, quartz, perthite and biotite, with fergusonite, zircon, magnetite and galena as its accessary minerals. Astrophyllite and thorite are abundant in a late alkali granite dike. Petrochemically, it is rich in K, Na, Si, and such rare metals as Nb, Ta, Y, Yb, Zr and Hf, but depleted in Al and Ca. In comparison with that found in other types of granite, the fergusonite in the alkaline granite has higher ferromagnesian components, thorium, niobium, but lower rare earths and tantalum.

  12. Chemical migration by contact metamorphism between pegmatite and country rocks: natural analogs for radionuclide migration

    International Nuclear Information System (INIS)

    Comparison of trace element signatures of country rocks as a function of distance from the contact with two pegmatites, Tin Mountain and Etta, in the Black Hills of South Dakota, suggests that some elements such as K, Li, Rb, Cs, As, Sb, Zn and Pb, have migrated to distances of 4 to 40 meters during contact metamorphism. The relative degree of migration varies depending on the element. On the other hand, there is virtually no migration of rare earth elements (REE), Al, Sc, Cr, Hf, U, and Th. Biotite and muscovite are effective trace element traps for Li, Rb, and Cs. Biotite has a greater affinity for Rb, Cs and Li than muscovite. 9 references, 5 figures, 1 table

  13. Evolutionary features of Caledonian magmatic rock and its relationship to uranium mineralization in the northern Danfeng area

    International Nuclear Information System (INIS)

    Caledonian magmatism in northern Danfeng area has experienced three tectonic stages as compression, transition and tension and formed granite batholith, granite stock and granitic pegmatite vein respectively. These rocks are obvious different in mineral component, texture and structure. Movement direction of magma is from north to south and from east to west with oblique uplifting. The transportation of magma is synchronous to the differential crystallization, diagenesis and ore-forming of uranium mineralization. The mineralization is located in biotitic granitic pegmatite veins which is formed in the final tension stage. This uranium forming mechanism can well explain the phenomenon that the deposit, occurrence, mineralizing occurrence found at present mainly distribute in the biotite granitic pegmatite veins between the contact zone of granite stock and southern granite batholith, and can be used as the criteria to select target for uranium prospecting in the area. (authors)

  14. Selected mineral associations in radioactive and REE occurrences in the Baie-Johan-Beetz area, Quebec

    International Nuclear Information System (INIS)

    This paper documents results of rapid chemical, spectrographic, scanning electron microscope, semiquantitative energy dispersive spectrometer, and neutron activation analyses for uranium content of minerals and host rocks for the following associations of primary and secondary minerals: 1. metasediments grading to garnetiferous feldspar pegmatites containing mafic zenoliths; 2. fergusonite-bearing pegmatite and rock-forming feldspars and micas; 3. biotite-horneblende gneiss hosting white radioactive pegmatites containing titanite, allanite and bastnaesite; 4. granite pegmatite containing associations of primary and secondary Pb, Ti, Nb, Th, U and Y minerals; 5. syenite pegmatite containing biotite, uraninite, uranothorite, zircon, apatite, allanite, xenotime, monazite, hydroxyl-bastnaesite and secondary amorphous phyllosilicates and U, Zr and REE mineral aggregates

  15. Origin and implications of zoned amphiboles and other hydrous silicates during aqueous brine infiltration in the Bamble mega shearzone, S-Norway

    Science.gov (United States)

    Sorensen, B. E.; Larsen, R. B.

    2009-12-01

    This study addresses the metasomatic alteration of ortho-amphibolites, in the Froland area in the Bamble sector, South Norway. Potassic alteration is associated with the introduction of biotite and the formation of conspicuous rims on the amphiboles. Significant color variation from deep blue green to light green in the rims encouraged a chemical study of their evolution. Dark blue-green rims are ferrotschermakite/ferropargasite. Rims gradually becomes richer in Mg and depleted in Fe, K, Na, Al and Cl and, finally, terminates with Cl poor actinolite (XMg ≈ 0.9). Simultaneously biotite experiences metasomatic alteration that is strongly correlated with the coexisting calcic amphibole rims. Fluid inclusions combined with phase diagram calculations documents that high salinity brines with near constant salinities of c. 30 wt% solvents, infiltrated and metasomatised the amphibolites throughout cooling and uplift from 630 to 280°C. The compositional changes reflect the complex interaction between brine fluids and hydrous minerals during cooling and uplift. Accordingly, the brine fluids fully control the composition of Fe-Mg silicates by metasomatosis. Models that argue that the biotite Fe/Mg ratio together with the P, T and the fluid compositin control the Cl content of (Munoz and Swenson 1981), can not explain the Froland amphiboles and biotites. This is because the silicate and whole rock chemistries are changed by interaction with the brine fluids. The compositional zoning reflects interaction with a fluid having constant halogen contents during gradually changing PT-conditions. In intensively altered areas the original amphibolite mineralogy is entirely replaced. Here we observe the large-scale metasomatic processes in a small scale version, for example following this pattern toward the centre of a vein: Amphibolite with small amount of biotite (host rock): Zone1: biotite-plagioclase zone (K-enrichment). Zone2: amphibole-plagioclase (K-depletion). Zone3

  16. Evaluation of the exploration drilling result of TML-3, TML-4, TML-5, TML-6 at Tanah Merah sector West Kalimantan

    International Nuclear Information System (INIS)

    Previous researcher obvioused that the uranium favourable zone at Tanah Merah has been existed, it is oriented NW-SE. In those zones have been discovered uranium mineralizations of NW-SE orientation and sub vertical dipping. This research intend to get knowledge about the uranium geology, character and geometry of the sub surface mineralization using exploration drilling. The result shows that lithologically the area dominated by biotite quartzite which is intruded by granitic rocks and lamprophyres. The mineralization consist of uraninite/ pitchblende associated by pyrite, chalcopyrite, pyrhotite, ilmenite, molybdenite, quartz, feldsphart and biotite. It seems to be granitic related mineralization as a vein type. Surface mineralization could be correlable to those of sub surface with in the lensoid or tabular shape favourable zones. Geological reserve of those mineralization is about 157 ton U3O8

  17. Uruguay geology contributions no. 7

    International Nuclear Information System (INIS)

    Arroyo Grande Formation (Lower Precambrian) are intruded by several granitoid bodies.The Marincho complex are represented by: a) a main unit integrated by hornblende diorites to monzoqranites, the main facies is a biotitic-hornblenditic granodiorite; b) An unconformable belt of porphyroblastics hornblendites and related granodiorites in complex relationships; c) A unit characterized by a two mica granite heterogranular to porphyritic wich cuts the previous sets; d) a little intrusion of gross leucogranite.The granodiorite of Arroyo Grande shows to be a apophysis to NW 01 Marincho Complex, being the most frecuent lacies a hornblende-biotite-granodiorite.The petrographic diagrams shows evolutive lines, suggesting different origins tor the main granodiorite, the Arroyo Grande granodiorite south granite and the hornbledites.

  18. New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana

    Science.gov (United States)

    Flowerdew, M.J.; Daly, J.S.; Riley, T.R.

    2007-01-01

    Five of six Rb-Sr muscovite mineral isochron ages from the Scotia Metamorphic Complex of the South Orkney Islands, West Antarctica, average 190 ± 4 Ma. The muscovite ages are interpreted to date foliation-formation and thus also accretion and subduction at the Gondwana margin. Coincident picrite and ferropicrite magmatism, indicative of melts from deep-seated depleted mantle, permits a causative link between accretion and the arrival of the Karoo – Ferrar – Chon Aike mantle plume in the Early Jurassic. Three biotite Rb-Sr mineral isochron ages are consistently younger and average 176 ± 5 Ma. The biotite ages may record post-metamorphic cooling or more likely retrogressive metamorphic effects during uplift.

  19. Bone Response to Four Dental Implants with Different Surface Topographies: A Histologic and Histometric Study in Minipigs.

    Science.gov (United States)

    Kalemaj, Zamira; Scarano, Antonio; Valbonetti, Luca; Rapone, Biagio; Grassi, Felice Roberto

    2016-01-01

    This study evaluated four implant surfaces in a minipig model: (1) Kohno Straight dual-engineered surface (DES) (Sweden & Martina); (2) SLActive (Straumann); (3) SM Biotite-H coated with Brushite (DIO); and (4) UF hybrid sandblasted and acid etched (HAS) (DIO). The surfaces presented different topographic features on the macro-, micro-, and nanoscales. After 12 weeks in vivo, significant differences were observed in bone-to-implant contact. UF HAS, presenting moderate microroughness and high nanoroughness, showed some advantage compared to nanorough SM Biotite-H and SLActive. A more pronounced difference was observed between UF HAS and Kohno Straight DES, characterized by a nanosmooth surface. Newly formed bone was observed around all surfaces. PMID:27560680

  20. Mineralogic and petrologic investigation of pre-test core samples from the spent fuel test-climax

    Energy Technology Data Exchange (ETDEWEB)

    Ryerson, F.J.; Qualheim, B.J.

    1983-12-01

    Pre-test samples obtained from just inside the perimeter of the canister emplacement holes of the Spent Fuel Test-Climax have been characterized by petrographic and microanalytical techniques. The primary quartz monzonite has undergone various degrees of hydrothermal alteration as a result of natural processes. Alteration is most apparent on primary plagioclase and biotite. The most common secondary phases on plagioclase are muscovite and calcite, while the most common secondary phases on biotite are epidote and chlorite. The major alteration zones encountered are localized along filled fractures, i.e. veins. The thickness and mineralogy of the alteration zones can be correlated with the vein mineralogy, becoming wider and more complex mineralogically when the veins contain calcite. 7 references, 10 figures, 4 tables.

  1. Mineralogic and petrologic investigation of pre-test core samples from the spent fuel test-climax

    International Nuclear Information System (INIS)

    Pre-test samples obtained from just inside the perimeter of the canister emplacement holes of the Spent Fuel Test-Climax have been characterized by petrographic and microanalytical techniques. The primary quartz monzonite has undergone various degrees of hydrothermal alteration as a result of natural processes. Alteration is most apparent on primary plagioclase and biotite. The most common secondary phases on plagioclase are muscovite and calcite, while the most common secondary phases on biotite are epidote and chlorite. The major alteration zones encountered are localized along filled fractures, i.e. veins. The thickness and mineralogy of the alteration zones can be correlated with the vein mineralogy, becoming wider and more complex mineralogically when the veins contain calcite. 7 references, 10 figures, 4 tables

  2. Micro tectonic milonitas analysis in the extreme south of the Sarandi del Yi shear zone: Kinematics and deformation conditions

    International Nuclear Information System (INIS)

    The Shear Zone divides Sarandi del Yi Craton River Plate in Piedra Alta and Nico Perez land . The southern end of this zone extends to north - south from the vicinity of the town of Minas to Punta Solis. The predominant lithology of the study area consists of a granitic mylonite with abundant muscovite and biotite. Structural data of foliation , stretching lineation and kinematic indicators were surveyed .Petrographic analysis shows that quartz is presented as ribbons polycrystalline product subgrain rotation recrystallization and grain boundary migration . Feldspar porphyroclasts are partially recrystallized in developing type structures core and mantle . Kinematic indicators such as sigma porphyroclasts , mica fish and oblique foliation defined consistently sinistral sense . The presence of stable and mirmequitas in the plane of biotite foliation along the microstructures described in quartz and feldspar , can be inferred temperature conditions between 450 ° C and 550° C during deformation

  3. 40Ar/39Ar age of the Rotoiti Breccia and Rotoehu Ash, Okataina Volcanic Complex, New Zealand, and identification of heterogeneously distributed excess 40Ar in supercooled crystals

    DEFF Research Database (Denmark)

    Flude, Stephanie; Storey, Michael

    2016-01-01

    Co-magmatic granitoid clasts erupted as part of the Rotoiti Ignimbrite (Rotoehu Tephra) contain euhedral K-feldspar and biotite crystals that protrude into miarolytic cavities and show textural evidence for growth in super-cooled conditions and are thus interpreted as growing during eruption. 40Ar....../39Ar stepped heating experiments on single K-feldspar crystals reveal the presence of heterogeneously distributed excess 40Ar, preferentially released at lower temperature steps (most likely from fluid/melt inclusions), which cannot reliably be characterised by, or corrected for using isotope...... correlation diagrams due to mixing between three reservoirs of 40Ar (radiogenic, atmospheric and excess). This excess 40Ar component is common, but not ubiquitous, and an age population unmixing algorithm applied to single-crystal fusion data identifies a younger group of K-feldspar and biotite crystals that...

  4. Rb-Sr systematics in drill core samples of the Eye-Dashwa Lakes pluton at the whole rock and mineral scale

    International Nuclear Information System (INIS)

    Twenty-one whole-rock samples from boreholes ATK-1 and ATK-6 define a precise Rb-Sr isochron with an age of 2637 ± 33 Ma and initial 87Sr/86Sr intercept, IR(Sr), of 0.70144 ± 0.00006. An internal mineral isochron for ATC-1 (991-997) and biotites from ATK-1 (35.63) and ATK-1 (3.84) give younger ages of 2541 ± 14 Ma 2574 ± 25 Ma, and 2534 ± 25 Ma, respectively. Data for samples from fracture zones scatter but correlate around an isochron of 2281 ± 153 Ma. The internal isochron and biotite ages record cooling below about 300 C due to uplift and erosion. The younger age, 2281 ± 153 Ma, records an episode or episodes of brittle failure at relatively high crustal levels. These fractures provided pathways for infiltration of water, which facilitated the mineralogical alteration

  5. The Polumir granite: Addititional data on its origin

    Directory of Open Access Journals (Sweden)

    Vukov Milenko S.

    2002-01-01

    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. The age of the Umkondo Group, eastern Zimbabwe, and implications for palaeomagnetic correlations

    International Nuclear Information System (INIS)

    The palaeomagnetic and geochronological evidence which led to assigning an age of approximately 1800 Ma for the Umkondo Group is reviewed. New Rb-Sr data from the Umkondo dolerites and lavas are presented involving 47 whole rock determinations and three analyses of separated biotites. The former give an errorchron yielding an age of 1078 ± 143 Ma; the scatter of points is largely attributed to country rock contamination. Biotite analyses from three of the samples yielded 1075 ± 21 Ma. It is concluded that the Umkondo Group has an age of 1080 + 140/-25 Ma. Comparisons of palaeomagnetic and geochronological datafrom various southern African igneous formations suggest widespread igneous activity in the subcontinent some 1200 - 1100 Ma ago. Implications for the previously suggested palaeomagnetic correlation of the Umkondo Group with the upper parts of the Waterberg Group of South Africa are discussed. 6 figs., 2 tabs., 40 refs

  7. Sr-Nd isotopic composition of lamprophyre dykes from Queen Maud Land, East Antarctica

    International Nuclear Information System (INIS)

    Alkali basaltic-lamprophyric dykes intrude precambrian gneisses in the Schirmacher oasis, Queen Maud land, East Antarctica. Rb-Sr and Sm-Nd isotopic data on two lamprophyre dykes are reported from the Schirmacher oasis. The lamprophyre dykes have given Rb-Sr biotite/whole rock isochron age of 439 ± 10 Ma (2σ). Large variations in εSr and εNd indicate higher degree of crustal assimilation. Higher εSr (+54 to +72) and lower εNd (-7 to -13) of these dykes also suggest that the source was contaminated by older crust. Biotite/whole rock Rb-Sr isotope data on lamprophyre dykes show that the terrain was affected by thermal event during early paleozoic which is correlated with the end of Pan-African orogeny. (author)

  8. Redox conditions in host rocks surrounding a drift in the Kamaishi in Situ Test Site, Japan

    International Nuclear Information System (INIS)

    The results of the redox investigation at the Kamaishi In Situ Test Site are summarized as follows: the dissolved oxygen concentration in groundwater decreases with increasing distance into the host rock from the drift wall; we have developed a conceptual model of redox front progress for estimating chemical change in the EDZ. Preliminary estimates of oxygen flux into the host rock from the drift wall are between 0.17 and 0.14 mol/m2, depending on the reactive surface area of biotite. The modeling results may overestimate the migration distance of the redox front into the host rock because ferrous minerals other than biotite are not considered in these preliminary calculations. Better estimates of redox-front behavior can be obtained, however, when reliable kinetic data for these minerals are available. (author)

  9. Petrology and geochemistry of the Los Cuartos granite, Tafi del Valle, Tucuman, northwest of Argentina: its integration to the regional magmatic layout; Petrologia y geoquimica del granito Los Cuartos, Tafi del Valle, Tucuman, noroeste de Argentina: integracion al esquema magmatico regional

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, J.P.; Bellos, L.I.

    2010-07-01

    Los Cuartos Granite crops out on the western flank of the Cumbres Calchaquies, east of Tafi del Valle, Tucuman Province, Argentina. It has a granitic to granodioritic composition, of two micas, being biotite dominant. The granite is medium grained and inequigranular, with rare K-feldspar megacrysts. It contains host-rock xenoliths with different degrees of assimilation. The granite intrusion produced contact metamorphism in the surrounding basement, with development of andalucite porphyroblasts and poikiloblastic biotite. The granite is calk-alkaline and peraluminous, and is K- and P-rich and Ca- and Napoor compared to other granitoids of the region. The pluton shows late-tectonic features with regard to the regional deformation. The granite possibly intruded during the Ordovician (Famatinian Cycle) and its emplacement was structurally controlled by the Tafi Megafracture. Los Cuartos Granite and other intrusive bodies of the region share similar petrographical, geochemical, structural and geochronological characteristics. (Author).

  10. 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

    2015-02-01

    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.

  11. Coupling limit equilibrium analyses and real-time monitoring to refine a landslide surveillance system in Calabria (southern Italy)

    OpenAIRE

    G. G. R. Iovine; P. Lollino; S. L. Gariano; O. G. Terranova

    2010-01-01

    On 28 January 2009, a large debris slide was triggered by prolonged rainfalls at the southern suburbs of San Benedetto Ullano (Northern Calabria). The slope movement affected fractured and weathered migmatitic gneiss and biotitic schist, and included a pre-existing landslide. A detailed geomorphologic field survey, carried out during the whole phase of mobilization, allowed to recognize the evolution of the phenomenon. A set of datum points was located along the borders of the landslide and f...

  12. Impact de l’alteration sur le bilan chimique des diatexites du Massif de l’Edough (Annaba, NE Algérien)

    OpenAIRE

    Hadj-Zobir, Soraya

    2012-01-01

    The studied section, located on the eastern part of the Edough massif (region of Annaba, Algeria), is characterized by a Mediterranean climate and the area is one of the most humid of Algeria (precipitation between 750 and 1200 mm/year). It consists of diatexites with homogeneous petrographic and metamorphic facies. The primary minerals are quartz, feldspar, oligoclase and biotite whereas weathering products are mostly represented by illite and montmorillonite. Although all samples comprise t...

  13. 40Ar/39Ar-Dating of deformation of transform-shear stage in evolution of the Early Caledonides in Western Sangilen (South-Eastern Tuva)

    International Nuclear Information System (INIS)

    Detail structural-metamorphic and isotopic investigations into borders of the Muguro-Chinchilig tectonic block are conducted. 40Ar/39Ar-isotope dating was conducted by the graduated warming-up with biotite for different zones. Carried studies demonstrate that in the boundary of 465 million years intensive shift disturbances entailing fragmentation of the Muguro-Chinchilig tectonic block and disturbances in entirety of its separate parts in borders of the Sangilen plateau (South-Eastern Tuva) were stated

  14. GEOCHEMISTRY

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>20082178 Cheng Liangjuan(College of Re- sources and Environmental Sciences,Nanjing Agricultural University,Nanjing 210095, China);Li Fuchun Adsorption of Silicate Bacteria on Surface of Orthoclase and Biotite and Its Selectivity(Geological Journal of Chi- na Universities,ISSN1006—7493,CN32—1440/P,13 (4),2007,p.669—674,4 illus.,21 refs.,with English abstract) Key words:silicates,bacteria

  15. Sorption and desorption of cesium on rapakivi granite and its minerals

    International Nuclear Information System (INIS)

    Batch sorption experiments of cesium were performed for rapakivi granite and its main minerals, and also for some fracture minerals. The main minerals quartz, potassium feldspar, plagioclase, biotite and hornblende were magnetically separated from crushed rapakivi granite. The fracture minerals were chlorite, dolomite and kaolinite. Sorption was studied in fresh and saline reference waters containing cesium in the range of 10-8 to 10-3 mol/l. The distribution ratios for rapakivi granite generally decreased with an increasing Cs concentration and an increasing ionic strength. For fresh rapakivi granite, the sorption behaviour was rather complex in both fresh and saline reference waters, being complex for the other alteration stages only in saline water. Sorption increased unexpectedly when the initial cesium concentration was raised to 10-5 - 10-4 mol/l. The sorption on rapakivi granite was non-linear, especially in saline water. Sorption was reversible for rapakivi granite. The sorption on the minerals proved to be very non-linear, especially on biotite. Sorption was also reversible for biotite and kaolinite. For the other minerals, sorption was irreversible to some degree. As to the sorption of cesium investigated by studying thin sections of rapakivi granite and their autoradiograms, the most dominating mineral was biotite. The water analyses made during the sorption experiment revealed the exchange of potassium and cesium. The corresponding changes were difficult to detect in saline water. Calculation of the Rd values for the rock, based on the Rd values of minerals and the portions of minerals in the rock, yielded smaller distribution ratios than the values determined for the rock. (orig.)

  16. Mafic granulite xenoliths in the Chilka Lake suite, Eastern Ghats Belt, India: evidence of deep-subduction of residual oceanic crust

    OpenAIRE

    Bhattacharya, S.; Chaudhary, A.K.; Saw, A. K.; Das, P.; Chatterjee, D

    2012-01-01

    Granulite xenoliths preserve key geochemical and isotopic signatures of their mantle source regions. Mafic granulite and pyroxinite xenoliths within massif-type charnockitic rocks from the Eastern Ghats Belt have recently been reported by us. The mafic granulite xenoliths from the Chilka Lake granulite suite with abundant prograde biotite are geochemically akin to Oceanic Island Basalt (OIB). They can be distinguished from the hornblende-mafic granulite xenoliths with signatures of Arc-derive...

  17. Magma mixing/mingling in the Eocene Horoz (Nigde) granitoids, Central southern Turkey: evidence from mafic microgranular enclaves

    Science.gov (United States)

    Kocak, Kerim; Zedef, Veysel; Kansun, Gursel

    2011-11-01

    Mafic microgranular enclaves (MMEs) are widespread in the Horoz pluton with granodiorite and granite units. Rounded to elliptical MMEs have variable size (from a few centimetres up to metres) and are generally fine-grained with typical magmatic textures. The plagioclase compositions of the MMEs range from An18-An64 in the cores to An17-An29 in the rims, while that of the host rocks varies from An17 to An55 in the cores to An07 to An33 in the rims. The biotite is mostly eastonitic, and the calcic-amphibole is magnesio-hornblende and edenite. Oxygen fugacity estimates from both groups' biotites suggest that the Horoz magma possibly crystallised at fO2 conditions above the nickel-nickel oxide (NNO) buffer. The significance of magma mixing in their genesis is highlighted by various petrographic and mineralogical characteristics such as resorption surfaces in plagioclases and amphibole; quartz ocelli rimmed by biotite and amphibole; sieve and boxy cellular textures, and sharp zoning discontinuities in plagioclase. The importance of magma mixing is also evident in the amphiboles of the host rocks, which are slightly richer in Si, Fe3+ and Mg in comparison with the amphiboles of MMEs. However, the compositional similarity of the plagioclase and biotite phenocrysts from MMEs and their host rocks suggests that the MMEs were predominantly equilibrated with their hosts. Evidence from petrography and mineral chemistry suggests that the adakitic Horoz MMEs could be developed from a mantle-derived, water-rich magma (>3 mass%) affected by a mixing of felsic melt at P >2.3 kbar, T >730°C.

  18. The effects of retrograde reactions and of diffusion on 39Ar-40Ar ages of micas

    DEFF Research Database (Denmark)

    Allaz, Julien; Engi, Martin; Berger, Alfons;

    2011-01-01

    Effects of metamorphic reactions occurring during decompression were explored to understand their influence on 39Ar-40Ar ages of micas. Monometamorphic metasediments from the Lepontine Alps (Switzerland) were studied. Collected samples reached lower amphibolite facies during the Barrovian...... retrograde chlorite formation. We conclude that even very minor chloritisation of biotite is apparently a more effective parameter than temperature in resetting the Ar clock, as is the formation of plagioclase from paragonite decomposition. Multi-equilibrium thermobarometry is necessary to ensure that...

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

    Science.gov (United States)

    Ripa, M.

    1994-06-01

    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.

  20. Retention of radiocaesium traces in clay: a dynamic semi-empirical modelling

    International Nuclear Information System (INIS)

    The contribution consists of an abstract of a PhD thesis. After deposition, Cs+bioavailability in soil is a key parameter with regard to public exposure after a severe nuclear accident.The objective of the PhD thesis was to understand and model the interaction of Cs+ and 2:1 clay minerals. This interaction was characterised through Cs+ sorption-desorption experiments carried out on seven 2:1 clay minerals (four smectite types, illite, biotite and vermiculite)

  1. Mikroskopische Studien ueber Gesteine aus den Molukken. 1. Gesteine von Ambon und den Uliassern. Mit einem französischen Résumé

    NARCIS (Netherlands)

    Schroeder van der Kolk, J.L.C.

    1888-01-01

    Dans le traité précédent j’ai décrit les types les plus caractéristiques parmi les échantillons de roche recueillis par M. MARTIN pendant ses voyages dans les Moluques. Ainsi il s’agit des Granites à biotite, des Péridotites, des Dacites, des Andésites à pyroxène, des Brèches volcaniques et aussi de

  2. Rare evidence for formation of garnet + corundum during isobaric cooling of ultrahigh temperature metapelites: New insights for retrograde P-T trajectory of the Highland Complex, Sri Lanka

    Science.gov (United States)

    Dharmapriya, P. L.; Malaviarachchi, Sanjeeva P. K.; Galli, Andrea; Su, Ben-Xun; Subasinghe, N. D.; Dissanayake, C. B.

    2015-04-01

    We report the occurrence of coexisting garnet + corundum in spinel- and corundum-bearing, garnet-sillimanite-biotite-graphite gneiss (pelitic granulites) from the Highland Complex (HC), Sri Lanka. In the investigated pelitic granulites, two domains such as quartz-saturated and quartz-undersaturated are distinguishable. The quartz-saturated domains consist of porphyroblastic garnet, quartz, plagioclase, alkali-feldspar and biotite flakes rimming garnet. The quartz-undersaturated domains are constituted of two generations of garnet (Grt1 and Grt2), sillimanite, plagioclase, alkali-feldspar, corundum, spinel and biotite. Grt1 encloses rare Ti-rich biotite and numerous rutile needles and apatite rods. Grt2 contains rare sillimanite and/or spinel inclusions. Corundum occurs in mutual contact with Grt2, partially embedded at the rim or as an inclusions in Grt2. Thermobarometry on inclusion phases in Grt1 indicates that during the prograde history pelitic granulites attained a P of 10.5-11 kbar at T of ~ 850 °C. Textural observations coupled with both pseudosections calculated in the NCKFMASHTMnO system and Ti-in-Garnet geothermobarometry suggest that peak metamorphism occurred at ultrahigh temperature (UHT) conditions of 950-975 °C and pressures of 9-9.5 kbar. Peak T was followed by a period of isobaric cooling that formed corundum and Grt2 at approx. 930 °C along with exsolution of rutile needles and apatite rods in Grt1. Thermodynamic modelling confirms that corundum appears along an isobaric cooling path at about 920-930 °C and 9-9.5 kbar. Therefore, the investigated granulites provide a rare example of post-peak crystallization of garnet + corundum along a retrograde metamorphic trajectory under UHT conditions. Thus, isobaric cooling at the base of the crust could be regarded as an alternative process to form coexisting garnet + corundum.

  3. The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

    Science.gov (United States)

    Simons, B.; Shail, Robin K.; Andersen, Jens C. Ø.

    2016-09-01

    The Early Permian Cornubian Batholith was generated during an extensional regime following Variscan convergence within the Rhenohercynian Zone of SW England. Its component granites can be classified, using mineralogical, textural and geochemical criteria, into five main types, all of which are peraluminous (A/CNK > 1.1): G1 (two-mica), G2 (muscovite), G3 (biotite), G4 (tourmaline) and G5 (topaz). G1 granites formed through up to 20% muscovite and minor biotite dehydration melting of a metagreywacke source at moderate temperatures and pressures (731-806 °C, > 5 kbar). Younger G3 granites formed through higher temperature, lower pressure (768-847 °C, data. Variations in the major elements, Ba, Sr and Rb indicate that G1 and G3 granites underwent 15%-30% fractionation of an assemblage dominated by plagioclase, alkali feldspar and biotite to form more evolved G2 and G4 granites, respectively. Decreasing whole-rock abundances of Zr, Th and REE support the fractionation of zircon, monazite, apatite and allanite. Subsolidus alteration in G2 and G4 granites is indicated by non-primary muscovite and tourmaline and modification of major and trace element trends for G3-G4 granites, particularly for P2O5 and Rb. Topaz (G5) granites show low Zr, REE and extreme enrichment in Rb (up to 1530 ppm) and Nb (79 ppm) that cannot be related in a straightforward manner to continued differentiation of the G1-G2 or G3-G4 series. Instead, they are considered to represent partial melting, mediated by granulite facies fluids, of a biotite-rich restite following extraction of G1 and/or G3 magmas; they do not exhibit the typical geochemical characteristics of intraplate A-type granites.

  4. Metagabbro associated with the shear zone on Prins Karls Forland (Svalbard, Arctic)

    Science.gov (United States)

    Maraszewska, Maria; Manecki, Maciej; Czerny, Jerzy; Schneider, David; Myhre, Per Inge; Faehnrich, Karol; Barnes, Christopher

    2016-04-01

    Prins Karls Forland (PKF) is a N-S elongated island situated west of Spitsbergen in the Svalbard archipelago, High Arctic. The northern part of the island is dominated by siliciclastic metasediments regionally metamorphosed to greenshist facies assemblages during one distinct stage of tectonism. Amphibolite facies garnet-mica schists, mica schists, quartzites and carbonate-silicate rocks exhibiting evidence of at least two distinct, strong deformation episodes (including mylonitization) locally outcrop on the east coast of PKF, termed the Pinkie Unit. A ~1 km wide shear zone containing ductile to brittle structures and distinct outcrops of greenstones (metagabbros and greenschists), associated with magnetite ore, separates these two contrasting tectonic units. Ten samples of greenstones were collected on the slopes of Lauratzonfjellet and Boureefjellet for petrologic and geochemical analyses. Despite intense localized shearing, the metagabbros are undeformed and preserve coarse crystalline, magmatic texture, which is locally poikilitic. The primary magmatic assemblage consists of brown hornblende, plagioclase, biotite and opaque minerals, with accessory apatite and titanite. No relicts of pyroxenes are preserved. Formation of secondary uralite, sericite and chlorite is observed. Metamorphic assemblage consists of actinolite pseudomorhs after hornblende, epidote, and second generation biotite. Blue amphibole is observed in one sample from Boureefjellet; greenschists from Boureefjellet also contain fibrous blue amphibole, as well as garnets, actinolite, epidote and biotite. Some rocks sampled on Boureefjellet are more strongly deformed and exhibit probably two stages of metamorphism: amphibolite facies metamorphism resulting in blue amphibole-garnet assemblage followed by greenschist facies metamorphism resulting in actinolite-epidote-biotite paragenesis. Parallel and overlapping patterns on chondrite-normalized REE diagrams and spider diagrams indicate that these

  5. Phosphate minerals of some granitic rocks associated quartz veins from northern and central Portugal

    OpenAIRE

    Neiva, A.M.R.; Silva, M.M.V.G.; Antunes, I.M.H.R.; Ramos, J. M. F.

    2000-01-01

    Phosphate minerals are common in northern and central Portuguese granitic rocks. Childrenite, eosphorite and intermediate compositions in this solid-solution séries occur in muscovite granites at Paredes da Beira and Penamacor-Monsanto, muscovite-biotite granites at Penamacor-Monsanto and in aplite veins at Vidago. The composition of childrenite and eosphorite are similar in each of these localities. Germanite occurs in a muscovite granite at Segura.

  6. The influence of particle size on the chemistry of mica clays

    OpenAIRE

    Gassman, Paul Lawrence

    1990-01-01

    In order to assess the importance of particle size on elemental composition, structure, morphology, and charge characteristics of 2:1 micas, mechanically produced clay separates were analyzed by; electron probe microanalysis (EPMA), transmission electron microscopy (TEM), thermogravimetry, specific surface area analysis, and ion exchange. Books of biotite and muscovite were reduced to clay size « 2.0 μm) particles by mechanical comminution, then further fractionated into coar...

  7. Baskarp Sand No. 15

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo; Bødker, Lars Bødker

    The Soil Mechanics Laboratory has started performing tests with a new sand, Baskarp No 15. Baskarp No 15 is a graded sand from Sweden. The shapes of the largest grains are round, while the small grains have sharp edges. The main part of of Baskarp No 15 is quarts, but it also contains feldspar an...... and biotit. Mainly the sand will be used for tests concerning the development of the theory of building up pore pressure in sand....

  8. High resolution characterization of ectomycorrhizal fungal-mineral interactions in axenic microcosm experiments

    OpenAIRE

    Saccone, Loredana; Gazzè, Salvatore A.; Duran, Adele L.; Leake, Jonathan R; Banwart, Steven A.; Ragnarsdóttir, Kristín Vala; Smits, Mark M; McMaster, Terence J.

    2012-01-01

    Microcosms with Pinus sylvestris seedlings in symbiosis with the fungus mycorrhizal Paxillus involutus were established, and atomic force microscopy (AFM) was used to characterise plant photosynthate-driven fungal interactions with mineral surfaces. Comparison of images of the same area of the minerals before and after mycorrhizal fungal colonization showed extensive growth of hyphae on three different mineral surfaces - hornblende, biotite and chlorite. A layer of biological exudate, or biol...

  9. Petrography and geochemistry of the topaz-bearing granite stocks in Artjärvi and Sääskjärvi, western margin of the Wiborg rapakivi granite batholith

    Directory of Open Access Journals (Sweden)

    Sari Lukkari

    2002-01-01

    Full Text Available The Artjärvi and Sääskjärvi granite stocks at the western margin of the Wiborg rapakivi batholith are multiphase rapakivi granite intrusions in which the most evolved phase is topaz-bearing granite. The Artjärvi stock is composed of porphyritic and even-grained biotite granite and even-grained topaz granite, and the Sääskjärvi stock comprises even-grained biotite granite and porphyritic topazgranite. The granites are metaluminous to peraluminous A-type granites, showing within-plate (WPG geochemical characteristics. The topaz granites from the Artjärvi and Sääskjärvi stocks are petrographically and geochemically similar to other topaz-bearing rapakivi granites in Finland. The anomalous geochemistry of the topaz granite is essentially magmatic; postmagmatic reactions have only slightly modified its composition. Greisen veins, some of which are mineralized, are widely found associated with the Artjärvi and Sääskjärvi stocks.The most characteristic feature of the Artjärvi granite stock is a stockscheider at the roof contact of the topaz granite. The stockscheider is composed of schlieren layering and pegmatite layers parallel to the contact. The most probable mechanism for the formation of the schlieren layering is velocity-gradient sorting parallel to the flow, which led to accumulation of mafic minerals along the upper contact of the topaz granite. Cooling and contraction of the topaz granite formed fractures parallel to the roof contact and the residual pegmatite magmas were injected along the fractures forming pegmatite layers. Textures like graphic intergrowths, aplitic groundmass and fan-shaped alkali feldspar crystals associated with the Artjärvi porphyritic biotite granite and pegmatite indicatecrystallization from undercooled magma. Miarolitic cavities found in the porphyritic biotite granite and topaz granite indicate at least local volatile saturation.

  10. On the Paleomagnetism of the Intrusives from the Panguna Porphyry Copper Deposit, Bougainville, Papua New Guinea

    OpenAIRE

    Nedachi, Munetomo; ENJOJI, Mamoru; URASHIMA, Yukitoshi; MANSER, Warren; ネダチ, ムネトモ; エンジョウジ, マモル; ウラシマ, ユキトシ; 根建, 心具; 浦島, 幸世

    1985-01-01

    The temporal relation between intrusives and mineralization of the Panguna porphyry copper deposit, Bougainville Island, Papua New Guinea, was reexamined using paleomagnetic method. The Kaverong Quartz Diorite intruded at the reversed geomagnetic period of 4.0 to 5.0 Ma. After the geomagnetic polarity changed, the Biotite Granodiorite intruded, and the surrouding rocks were mineralized. These rocks have remanent magnetizations of normal polarity. At the next geomagnetic peri...

  11. Investigation of magnesium isotope fractionation during granite differentiation: Implication for Mg isotopic composition of the continental crust

    Science.gov (United States)

    Liu, Sheng-Ao; Teng, Fang-Zhen; He, Yongsheng; Ke, Shan; Li, Shuguang

    2010-09-01

    High-precision Mg isotopic analysis was performed on a suite of well-characterized I-type granitoids and associated hornblende and biotite minerals from the Dabie Orogen in central China, to address the behavior of Mg isotopes during granite differentiation. Although these granitoids formed through different degrees of partial melting and fractional crystallization, with large variations in elemental and mineral compositions, their δ26Mg values vary from -0.26 to -0.14 and are indistinguishable within our analytical precision (± 0.07‰; 2 SD). Coexisting hornblendes and biotites in these granitoids display similar Mg isotopic composition, with δ26Mg ranging from -0.31 to -0.14 in hornblendes and -0.23 to -0.12 in biotites. The inter-mineral fractionation factors (Δ 26Mg Hbl-Bt = δ26Mg Hbl - δ26Mg Bt) vary from -0.10 to -0.02, with an average = -0.06 ± 0.08 (2 SD). The limited inter-mineral fractionation agrees with the theoretic prediction that Mg cations in both hornblende and biotite are octahedrally coordinated with oxygen, which restricts the magnitude of equilibrium isotope fractionation. Overall, data from both bulk granitoids and associated mineral separates suggest that Mg isotope fractionation during I-type granite differentiation is limited. Collectively, granitoids studied here have Mg isotopic composition similar to that of terrestrial basalts and peridotites ( δ26Mg = -0.21 ± 0.07 vs. -0.25 ± 0.07; 2 SD), confirming that magmatic processes do not significantly fractionate Mg isotopes. The continental crust in the Dabie Orogen, as sampled by these I-type granitoids, has a mantle-like Mg isotopic composition. Given that significant Mg isotope fractionation occurs during chemical weathering processes, Mg isotopes may potentially be used for tracing granite genesis, in particular, if sedimentary materials are involved in granite sources.

  12. Composition and origin of aeolian and fluvial sands of Gavkhuni playa lake (southeast of Isfahan)

    OpenAIRE

    H.R., Pakzad,; Van, M. A.; M., Pasandi,; Z., Aliniaie,

    2012-01-01

    Gavkhuni playa lake, located 130 km southeast of Isfahan, comprises of sand, mud and salt flats. This playa includes two environments as delta and playa lake. Sand dunes, 45 kilometers long, extend in the west of the playa. Rock fragments of andesite, dacite, tuff, granite, schist, gneiss, fossil bearing limestone, sandstone and also quartz and feldspar minerals form the alluvial and aeolian sediments. Heavy minerals including idocrase, tourmaline, biotite, wollastonite, magnetite, hematite, ...

  13. Nuclear physics techniques for determination of rocks age

    International Nuclear Information System (INIS)

    The low background nuclear physics techniques were used for measure age geologic samples of micas (biotite, lepidolite, muscovite, phlogopite) by means of detection a gamma radiation from radioisotopes. The nuclear reactions 87Sr(gamma,gamma)87mSr, 87Rb(gamma,n)86Rb and 85Rb(gamma,n)84Rb was used. Application of a braking radiation of the powerful accelerator of electrons has allowed simultaneously to measure an element composition of samples

  14. La formación Chango Real (NW de Sierras Pampeanas, República Argentina), ejemplo del magmatismo paleozoico (Cambrico?). Diferencias geoquímicas con batolitos ordovicicos

    OpenAIRE

    Lazarte, J. E.

    1992-01-01

    Chango Real Formation is part of Lower Paleozoic magmatism in Sierras Pampeanas Range, Northwestern Argentina. It is a biotitic, granitic ortogneiss, peraluminous, calcalkaline from Cambrian(?), different from others Ordovician batholiths. The origin of the magma was in a convergent active margin of plate, generated in the middle crust. It evolved by fractional crystallization (the last stage ended at 4 kb and 680º C) and was deformed during Famatinian Cycle (Ordovician-Silurian).L...

  15. Geology, age and tectonic evolution of the Sierra Maestra Mountains, southeastern Cuba

    OpenAIRE

    Bojar, A.V.; García-Delgado, D.E.; Rojas-Agramonte, Y.; Neubauer, F.; Hejl, E.; Handler, R.

    2006-01-01

    We summarize the available geological information on the Sierra Maestra Mountains in southeastern Cuba and report new zircon fission track and biotite Ar-Ar ages for this region. Two different and genetically unrelated volcanic arc sequences occur in the Sierra Maestra, one Cretaceous in age (pre-Maastrichtian) and restricted to a few outcrops on the southern coast, and the other Palaeogene in age, forming the main expression of the mountain range. These two sequences are overlain by middle t...

  16. Dataciones Rb/Sr en el complejo plutónico Táliga Barcarrota (CPTB) (Badajoz)

    OpenAIRE

    Galindo Francisco, Mª del Carmen; Portugal Ferreira, Martín R.; Casquet, César; Priem, H.N.A.

    1990-01-01

    The Plutonic Complex of Táliga-Barcarrota crops out in the core of the Olivenza-Monesterio anticline, where it intrudes the Upper Precambrian and Lower Cambrian metasediments. As this Complex is made of a) the Circular Pluton of Barcarrota, where the core is constituted by gabbros, diorites and pegmatoides and the outer rim shows quartz monzonites, quartz syenites and hypersolvus granites, and b) the NW-SE elongated Táliga Massif, almost entirely made of biotite orthogneisses, ...

  17. Petrology and geochemistray of Imam-Zadeh Hashem mafic and ultramafic bodies, southern Guilan province

    OpenAIRE

    Mojgan Salavati; Reza Fahim Guilani

    2013-01-01

    Mafic and ultramafic plutonic igneous bodies, with small and big outcrops, between Shemshak rock units (Jurassic) are observed in east of Imam Zadeh Hashem, in southern Guilan province. Ultramafic cumulates consist of clinopyroxenite, and plagiofer clinopyroxenite, olivine clinopyroxenite, and mafic rocks, based on mineralogy consist of gabbros, olivine gabbros, biotite gabbros and amphibole gabbros. According to geochemical data, studied rocks have tholeiitic nature and in the tectonic setti...

  18. 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)

  19. The thermal history of the Lhasa Block, South Tibetan Plateau based on FTD and Ar-Ar dating

    CERN Document Server

    Yang, T F; Lo Chong Huah; Chung, S L; Tien, R L; Xu, R; Deng, W

    1999-01-01

    Twelve basement samples were collected from South Tibet Plateau for FTD and Ar-Ar analysis to demonstrate their uplifting history since Cenozoic era. The preliminary results from different minerals with different closure temperatures, including apatite and zircon for fission-track dating, and K-feldspar, biotite for Ar-Ar dating, show that at least four stages of thermal history can be recognized in the studied area.

  20. Geochronology of Triassic-Jurassic granitoids in the southern frames of Mongol-Okhotsk fold belt and the principles of early mesozoic granitic formation in the Central and East Asia

    International Nuclear Information System (INIS)

    Results of U-Pb and U-Pb-Th-isotope dating of zircon from biotite and leucocratic granites in the southern frames of the Mongol-Okhotsk fold belt are presented. The similar estimates of the above mentioned granite ages (208±9 and 190±3 mln. years), the granites being referred traditionally to different intrusive complexes, permit defining essentially the scale of the early mesozoic magmatism manifestations in the Central and East Asia

  1. The nature of transition from adakitic to non-adakitic magmatism in a slab window setting: A synthesis from the eastern Pontides, NE Turkey

    OpenAIRE

    Eyuboglu, Yener; Santosh, M; Dudas, Francis O.; Chung, Sun-Lin; Akdag, Kemal; Bektas, Osman; AKARYALI, Enver

    2012-01-01

    The eastern Pontides orogenic belt provides a window into continental arc magmatism in the Alpine–Himalayan belt. The late Mesozoic–Cenozoic geodynamic evolution of this belt remains controversial. Here we focus on the nature of the transition from the adakitic to non-adakitic magmatism in the Kale area of Gumushane region in NE Turkey where this transition is best preserved. The adakitic lithologies comprise porphyries and hyaloclastites. The porphyries are represented by biotite-rich andesi...

  2. Magma Interaction Recorded in Plagioclase Zoning in Granitoid Systems, Zigana Granitoid, Eastern Pontides, Turkey

    OpenAIRE

    KARSLI, ORHAN; SADIKLAR, FARUK AYDIN & M. BURHAN

    2004-01-01

    Plagioclase crystals characterized by compositional zoning are typical of the Zigana Granitoid (ZG), NE Turkey. The zoned crystals, which show textural equilibrium with the assemblage quartz + plagioclase + K-feldspar + hornblende + biotite + pyroxene + magnetite + ilmenite, exhibit oscillatory zoning. The zoned plagioclase crystals, ranging in size from 3 to 6 mm, are oval and larger than normal lath-shaped crystals. The zoned crystals are divided petrographically into two main types: (i) cr...

  3. Moessbauer and XRD Comparative Study of Host Rock and Iron Rich Mineral Samples from Paz del Rio Iron Ore Mineral Mine in Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, M.; Perez Alcazar, G. A. [Universidad del Valle, Departamento de Fisica (Colombia); Moreira, A. M.; Speziali, N. L. [Universidade Federal de Minas Gerais, Departamento de Fisica (Brazil)

    2004-12-15

    A comparative study between the host rock and the iron rich mineral samples from the Paz del Rio iron ore mineral mine in Colombia was performed using X-ray diffraction and Moessbauer spectroscopy. Diffraction results of the iron rich mineral sample show that goethite, hematite, quartz, kaolinite and siderite are the main phases, and that a small amount of illite is also present. By Moessbauer spectroscopy at room temperature (RT) the presence of all the above mentioned phases was detected except quartz as well as an additional presence of small amount of biotite. The goethite, which appears as four sextets with hyperfine fields of 33.5, 30.5, 27.5 and 18.5 T, respectively, is the majority phase. This result shows the different grades of formation of this oxyhydroxide. The Moessbauer spectrum of this sample at 80 K presents the same phases obtained at RT without any superparamagnetic effect. In this case the goethite appears as two sextets. Diffraction results of the host rock sample show a large amount of quartz and kaolinite and small amounts of illite and biotite, whereas by Moessbauer spectroscopy illite, kaolinite and biotite were detected.

  4. Preliminary thermal expansion screening data for tuffs

    International Nuclear Information System (INIS)

    A major variable in evaluating the potential of silicic tuffs for use in geologic disposal of heat-producing nuclear wastes is thermal expansion. Results of ambient-pressure linear expansion measurements on a group of tuffs that vary treatly in porosity and mineralogy are presente here. Thermal expansion of devitrified welded tuffs is generally linear with increasing temperature and independent of both porosity and heating rate. Mineralogic factors affecting behavior of these tuffs are limited to the presence or absence of cristobalite and altered biotite. The presence of cristobalite results in markedly nonlinear expansion above 2000C. If biotite in biotite-hearing rocks alters even slightly to expandable clays, the behavior of these tuffs near the boiling point of water can be dominated by contraction of the expandable phase. Expansion of both high- and low-porosity tuffs containing hydrated silicic glass and/or expandable clays is complex. The behavior of these rocks appears to be completely dominated by dehydration of hydrous phases and, hence, should be critically dependent on fluid pressure. Valid extrapolation of the ambient-pressure results presented here to depths of interest for construction of a nuclear-waste repository will depend on a good understanding of the interaction of dehydration rates and fluid pressures, and of the effects of both micro- and macrofractures on the response of tuff masss

  5. Combined oxygen, hydrogen, /sup 40/Ar//sup 39/Ar isotopic evaluation of molybdenite mineralization, east Pioneer Mountains, Montana

    Energy Technology Data Exchange (ETDEWEB)

    Chesley, J.T.; Snee, L.W.; O' Neil, J.R.

    1985-01-01

    The Pear Lake molybdenite (moly) prospect is in the Eastern Pioneer Wilderness Area, 30 km south of the Cannivan Gulch moly deposit. It lies on a NW-SE trend with other prospects that are contemporaneous. Mineralized veins outcrop sporadically over a 4 square mile area, with a major concentration in the center of the study area. Previous studies have suggested potential moly-mineralization at depth. /sup 40/Ar//sup 39/Ar age-spectra on hornblend (hb) from the granodiorite host rock indicate emplacement at 75.0 +/- 1 Ma, with biotite closure at 69.0 +/- .3 Ma, in the vicinity of Pear Lake. Hydrothermal muscovites from the moly-bearing veins have ages of 68.0 +/- .5 Ma. partial resetting of biotite cooling dates in the vicinity of mineralization are observed, but biotites on the outer portion of the mineralizing system are undisturbed. These relations suggest that mineralization occurred after the host pluton had cooled to below 280/sup 0/C. Quartz-magnetite isotopic temperatures are 380 to 420/sup 0/C for moly-veins. These data suggest that magmatic hydrothermal fluids operated in the upper portion of this molysystem. These isotopic data, combined with geologic mapping, suggest that the Pear Lake moly prospect resulted from a weak, short-lived magmatic hydrothermal event at depth, and is unlikely to contain economic levels of molybdenum. The combined /sup 40/Ar//sup 39/Ar-stable isotope approach should prove useful in evaluating other hydrothermal systems.

  6. Petrology and mineral chemistry of peraluminous Marziyan granites, Sanandaj-Sirjan metamorphic belt (NW Iran

    Directory of Open Access Journals (Sweden)

    Darvishi Esmaiel

    2015-10-01

    Full Text Available The Marziyan granites are located in the north of Azna and crop out in the Sanandaj-Sirjan metamorphic belt. These rocks contain minerals such as quartz, K-feldspars, plagioclase, biotite, muscovite, garnet, tourmaline and minor sillimanite. The mineral chemistry of biotite indicates Fe-rich (siderophyllite, low TiO2, high Al2O3, and low MgO nature, suggesting considerable Al concentration in the source magma. These biotites crystallized from peraluminous S-type granite magma belonging to the ilmenite series. The white mica is rich in alumina and has muscovite composition. The peraluminous nature of these rocks is manifested by their remarkably high SiO2, Al2O3 and high molar A/CNK (> 1.1 ratio. The latter feature is reflected by the presence of garnet and muscovite. All field observations, petrography, mineral chemistry and petrology evidence indicate a peraluminous, S-type nature of the Marziyan granitic rocks that formed by partial melting of metapelite rocks in the mid to upper crust possibly under vapour-absent conditions. These rocks display geochemical characteristics that span the medium to high-K and calc-alkaline nature and profound chemical features typical of syn-collisional magmatism during collision of the Afro-Arabian continental plate and the Central Iranian microplate.

  7. Metamorphism of the Basement of the Qilian Fold Belt in the Minhe-Ledu Area, Qinghai Province, NW China

    Institute of Scientific and Technical Information of China (English)

    蔡金郎; 魏光华; 王庆树

    2002-01-01

    The basement of the central Qilian fold belt exposed along the Minhe-Ledu highway consists of psammiticschists, metabasitic rocks, and crystalline limestone. Migmatitic rocks occur sporadically among psammitic schist andmetabasitic rocks. The mineral assemblage of psammitic schist is muscovite + biotite + feldspar + quartz + tourmaline ±titanite ± sillimanite and that of metabasitic rocks is amphibole + plagioclase + biotite ± apatite ± magnetite ± pyroxene ±garnet ± quartz. The migmatitic rock consists of leucosome and restite of various volume proportions; the former consistsof muscovite + alkaline feldspar + quartz ± garnet ± plagioclase while the latter is either fragments of psammitic schist orthose of metabasitic rock. The crystalline limestone consists of calcite that has been partly replaced by olivine. The olivinewas subsequently altered to serpentine. Weak deformations as indicated by cleavages and fractures were imposed promi-nently on the psammitic schists, occasionally on metabasitic rocks, but not on migmatitic rocks. The basement experiencedmetamorphism up to temperature 606-778C and pressure 4.8-6.1 kbar (0.48-0.61 GPa), equivalent to amphibolite-granulite facies. The peak of the metamorphism is marked by a migmatization which occurred at several localities alongthe studied route 587-535 Ma ago. The basement also recorded a retrograde metamorphism of greenschist facies, duringwhich biotite, garnet, amphibole, and pyroxene were partly altered to chlorite.

  8. Petrology and mineral chemistry of peraluminous Marziyan granites, Sanandaj-Sirjan metamorphic belt (NW Iran)

    Science.gov (United States)

    Darvishi, Esmaiel; Khalili, Mahmoud; Beavers, Roy; Sayari, Mohammad

    2015-10-01

    The Marziyan granites are located in the north of Azna and crop out in the Sanandaj-Sirjan metamorphic belt. These rocks contain minerals such as quartz, K-feldspars, plagioclase, biotite, muscovite, garnet, tourmaline and minor sillimanite. The mineral chemistry of biotite indicates Fe-rich (siderophyllite), low TiO2, high Al2O3, and low MgO nature, suggesting considerable Al concentration in the source magma. These biotites crystallized from peraluminous S-type granite magma belonging to the ilmenite series. The white mica is rich in alumina and has muscovite composition. The peraluminous nature of these rocks is manifested by their remarkably high SiO2, Al2O3 and high molar A/CNK (> 1.1) ratio. The latter feature is reflected by the presence of garnet and muscovite. All field observations, petrography, mineral chemistry and petrology evidence indicate a peraluminous, S-type nature of the Marziyan granitic rocks that formed by partial melting of metapelite rocks in the mid to upper crust possibly under vapour-absent conditions. These rocks display geochemical characteristics that span the medium to high-K and calc-alkaline nature and profound chemical features typical of syn-collisional magmatism during collision of the Afro-Arabian continental plate and the Central Iranian microplate.

  9. Discovery of khondalite series from the western segment of Altyn Tagh and their petrological and geochronological studies

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and garnet-amphibole two-pyroxene granulites occurring as lenses and layers within gneisses (schists), were discovered in Tula area of western segment of Altyn Tagh. The petrology and geochemistry indicate that the protoliths of aluminum-rich gneisses (schists) are aluminum-rich pelitic and pelitic arenaceous sedimentary rocks, the protoliths of basic granulites are continental tholeiitic basalts. Therefore, the khondalite series may be produced at continental margin. They had suffered granulitic facies metamorphism with peak temperatures of 700-850℃ and pressures of 0.8-1.2 GPa. The U-Pb and Pb-Pb isotopic dating of zircons provided the ages of 447-462 Ma representing the ages of peak granulitic metamorphism. The U-Pb dating of detrital zircons from aluminum-rich gneisses yielded older upper intercept ages which reflect the times of older materials derived from source rocks of the gneiss protoliths.

  10. Discovery of khondalite series from the western segment of Altyn Tagh and their petrological and geochronological studies

    Institute of Scientific and Technical Information of China (English)

    张建新[1; 张泽明[2; 许志琴[3; 杨经绥[4; 崔军文[5

    2000-01-01

    The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and garnet-amphibole two-pyroxene granulites occurring as lenses and layers within gneisses (schists), were discovered in Tula area of western segment of Altyn Tagh. The petrology and geochemistry indicate that the protoliths of aluminum-rich gneisses (schists) are aluminum-rich pelitic and pelitic arenaceous sedimentary rocks, the protoliths of basic granulites are continental tholeiitic basalts. Therefore, the khondalite series may be produced at continental margin. They had suffered granulitic facies metamorphism with peak temperatures of 700-850℃ and pressures of 0.8-1.2 GPa. The U-Pb and Pb-Pb isotopic dating of zircons provided the ages of 447-462 Ma representing the ages of peak granulitic metamorphism. The U-Pb dating of detrital zircons from aluminum-rich gneisses yielded older upper i

  11. Metamorphism of cordierite gneisses from Eastern Ghat Granulite Terrain, Andhra Pradesh, South India

    Science.gov (United States)

    Murthy, D. S. N.; Charan, S. Nirmal

    1988-01-01

    Cordierite-bearing metapelites of the Eastern Ghat granulite terrain occur in close association of Khondalites, quartzites, calc-silicate rocks and charnockites. Rocks occurring between Bobbili in the north and Guntur in the south of Andhra Pradesh are studied. The association of the mineral and textural relationships suggest the following metamorphic reactions: Garnet + sillimanite + quartz = cordierite, hypersthene + sillimanite + quartz = cordierite, sillimanite + spinel = cordierite + corundum, and biotite + quartz + sillimanite = cordierite + K=feldspar. Generally the minerals are not chemically zoned except garnet-biotite showing zoning when they come in close contact with one another. The potential thermometers are provided by the Fe-Mg distribution of coexisting biotite-garnet and cordierite-garnet. Conflicting interpretation of the P/T dependence of these reactions involving cordierite are due to H2O in the cordierite. The presence of alkali feldspar-quartz assemblage which is common in these gneisses will be constrained from melting only if H2O activity is less than 0.5. The piezometric array inferred is convex towards the temperature array, indicating a rapid and isothermal crustal uplift probably aided by thrust tectonics.

  12. Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    刘伟

    2000-01-01

    18O/16O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of 18O/16O and D/H exchanges with meteoric water brought about a marked decrease in the δ18O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its 18O/16O. However, the first stage of 18O/16O exchange with the 18O-rich aqueous fluid derived from the dehydration within the deep crust caused the Δ18OQuariz-Feidspar reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.

  13. Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    18O/16O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of 18O/16O and D/H exchanges with meteoric water brought about a marked decrease in the δ18O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its 18O/16O. However, the first stage of 18O/16O exchange with the 18O-rich aqueous fluid derived from the dehydration within the deep crust caused the δ18OQuartz-Feldspar reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.

  14. Charnockitic ortho gneisses and mafic granulite s of the Cerro Olivo complex, south-east Uruguay, Part 2: lithogeochemistry, mineral o chemistry and thermo barometry

    International Nuclear Information System (INIS)

    The Cerro Olivo complex in SE-Uruguay shows different kinds of orthogneisses containing biotite, amphibole and/or orthopyroxene-biotite (charnockitic gneisses). Minor occurrences of mafic granulites are associated. They include low and high pressure kinds. We present the lithogeochemistry and compared mineral chemistry analyses of both the charnockitic orthogneisses and the mafic rocks. Theres i a calc-alkaline geochemical affinity of the biotite-bearing and charnockitic gneisses, while the mafic rocks could derive from tholeitic gabbros. These results allow discrininatieg two kinds of mafic rocks: Low and hight MgO contents, both representing respectively garnet-bearing and garnet-free mafic granulites. The orthopyroxene in the Opx-Bt orthogneisses in FE-rich while MgO-rich mafic rocks show hypersthenes. The thermobarometric data of mafic granulites show temperatures higher than 850°C and two contrasting mineral assemblages, one formed by ∼ 1 Kbar and 770° - 800°C (pre-M). and the other by 5.5 Kbar and 680-700° (M). The mineral chemistry suggests the occurrence of contrasting protoliths to explain the stability of two different mineral associations

  15. Preliminary studies of stable isotope data in the Pancanta-La Carolina tungsten district, San Luis, Argentina

    International Nuclear Information System (INIS)

    In the southern part of igneous-metamorphic basement of Sierras de San Luis (Eastern Pampean Ranges) in the Pancanta area, are located the tungsten deposits; the distribution of W-bearing quartz vein mineralization was controlled by shear zones heterogeneously spride within the La Escalerilla Granite (early Devonian), Las Verbenas Tonalite (early Famatinian) and metasedimentary rocks (San Luis Formation). In the granite the W-bearing quartz vein mineralization are in contact with thin sheared tonalite bands. The close spacial relation between the granite and the W-deposits seem to indicate the influence of the granite hydrotemal activity in the ore-fluids. The calculated δ18O values of 6.0 per mil and 9.4 per mil from biotite and quartz, respectively (El Porvenir mine) resemble those for fluids in felsic magmas. The calculated δD values of -88 per mil from biotite (El Porvenir mine) lie below the fields for waters in felsic magmas. For other hand both calculated δ18O and δD values from biotite (El Porvenir mine) lie within the field late potassic alteration. The calculated δ 34S value = 6.0 per mil from pyrite in the Pancanta mine), will closely reflect those of the hydrothermal fluids at the temperatures of interest, with a significant input of metasedimentary sourced sulfur in the ore fluids (au)

  16. Speciation of radioactive soil particles in the Fukushima contaminated area by IP autoradiography and microanalyses.

    Science.gov (United States)

    Mukai, Hiroki; Hatta, Tamao; Kitazawa, Hideaki; Yamada, Hirohisa; Yaita, Tsuyoshi; Kogure, Toshihiro

    2014-11-18

    Radioactive soil particles several tens of micrometers in size were collected from litter soil in the radiation contaminated area by the Fukushima nuclear plant accident and characterized using electron and X-ray microanalyses. The radioactive particles were discriminated by autoradiography using imaging plates (IP) on which microgrids were formed by laser ablation in order to find the particles under microscopy. Fifty radioactive particles were identified and classified into three types from their morphology and chemical composition, namely: (1) aggregates of clay minerals, (2) organic matter containing clay mineral particulates, and (3) weathered biotite originating from local granite. With respect to the second type, dissolution of the organic matter did not reduce the radiation, suggesting that the radionuclides were also fixed by the clay minerals. The weathered biotite grains have a plate-like shape with well-developed cleavages inside the grains, and kaolin group minerals and goethite filling the cleavage spaces. The reduction of the radiation intensity was measured before and after the trimming of the plate edges using a focused ion beam (FIB), to examine whether radioactive cesium primarily sorbed at frayed edges. The radiation was attenuated in proportion to the volume decrease by the edge trimming, implying that radioactive cesium was sorbed uniformly in the porous weathered biotite. PMID:25343443

  17. Field Features And Mode Of Emplacement Of Pegmatites Of Keffi Area North Central Nigeria

    Directory of Open Access Journals (Sweden)

    Tanko

    2015-04-01

    Full Text Available Abstract The Keffi area of North Central Nigeria hosts numerous pegmatite bodies which are related to the surrounding granitic intrusions islocated about 45 km east of the Federal Capital Territory Abuja Nigeria. Petrological investigation of the pegmatites and surrounding host rocks aimed at characterising and understanding field relations and mode of emplacement of the rocks with a view to assess their mineralisation potentials were carried out. From the field observations the pegmatites were characterised into 1 Pelitic schist-amphibolite hosted pegmatites and 2 Granitoids orthogneisses hosted pegmatites and the granites into 1 the Bakin Ayini biotite granites 2 the Angwan Madugu biotite-muscovite granites and 3 the Sabongida biotite-muscovite granites. It is clear that those discordantly emplaced in pelitic schists varied in shape and size with length and width ranging from 400-2000m and 2-20m respectively some are huge isolated sill-like and flat-lying whilst those hosted in orthogneisses are narrow ranging in length 40-1000m and width 1-4m crosscutting and vertically oriented along shear zones which suggest passive emplacement

  18. Degradative crystal–chemical transformations of clay minerals under the influence of cyanobacterium-actinomycetal symbiotic associations

    Directory of Open Access Journals (Sweden)

    Ekaterina Ivanova

    2014-04-01

    Full Text Available Cyanobacteria and actinomycetes are essential components of soil microbial community and play an active role in ash elements leaching from minerals of the parent rock. Content and composition of clay minerals in soil determine the sorption properties of the soil horizons, water-holding capacity of the soil, stickiness, plasticity, etc. The transformative effect of cyanobacterial–actinomycetes associations on the structure of clay minerals – kaolinite, vermiculite, montmorillonite, biotite and muscovite – was observed, with the greatest structural lattice transformation revealed under the influence of association in comparison with monocultures of cyanobacterium and actinomycete. The range of the transformative effect depended both on the type of biota (component composition of association and on the crystal–chemical parameters of the mineral itself (trioctahedral mica – biotite, was more prone to microbial degradation than the dioctahedral – muscovite. The formation of the swelling phase – the product of biotite transformation into the mica–vermicullite mixed-layered formation was revealed as a result of association cultivation. Crystal chemical transformation of vermiculite was accompanied by the removal of potassium (К, magnesium (Mg and aluminum (Al from the crystal lattice. The study of such prokaryotic communities existed even in the early stages of the Earth's history helps to understand the causes and nature of the transformations undergone by the atmosphere, hydrosphere and lithosphere of the planet.contribution of treatments on structure induces and model parameters are discussed in the paper.

  19. Geology and uranium mineralisation around Ampulli Area, Papum-Pare District, Arunachal Pradesh, North-East India

    International Nuclear Information System (INIS)

    Uranium mineralisation associated with Middle Proterozoic Bomdila Group (Daling equivalent) metasediments have been located intermittently over a strike length of 310 m with 0.11 to 2.0 m thickness around Ampulli area of Papum-Pare district, Arunachal Pradesh. The metasediments trend NE-SW and dip 20°- 85° due either side. The grab and trench samples assayed 0.012 - 0.36% eU3O8, 0.006 - 0.19% U3O8 (beta/gamma), 0.009 - 0.235% U3O8 (Chem.) and less than 0.010% ThO2. The host rocks have been identified as tourmaline bearing biotite-quartz schist, garnet bearing muscovite-biotite-quartz schist and muscovite-biotite schist. Uraninite, brannerite and U-Ti complex are observed with uranocircite and meta-uranocircite, the secondary uranium minerals. Replacement of uraninite by molybdenite and pyrite suggested earlier oxide and later sulphide phase. Partial chemical analysis indicated aluminous nature of the host rock and their high K2O/Na2O (3.3-10.73) ratios are suggestive of predominance of potash feldspar over sodic and effects of potash metasomatism. Both syngenetic as well as epigenetic hydrothermal origin of uranium mineralisation has been suggested. (author)

  20. A study of small-scale foliation in lengths of core enclosing fault zones in borehole WD-3, Permit Area D, Lac du Bonnet Batholith

    Energy Technology Data Exchange (ETDEWEB)

    Ejeckam, R.B.

    1992-12-01

    Small-scale foliation measurements in lengths of core from borehole WD-3 of Permit Area D of the Lac du Bonnet Batholith have defined five major mean orientation sets. They strike NW, N and NE. The orientations (strike to the left of the dip direction/dip) of these sets are as follows: Set I - 028/74 deg; II - 001/66 deg; III - 100/58 deg; IV - 076/83 deg; and V - 210/40 deg. The small-scale foliations were defined by different mineral types such as biotite crystals, plagioclase, mineral banding and quartz lenses. Well-developed biotite foliation is commonly present whenever well-developed plagioclase foliation exists, but as the strength of development weakens, the preferred orientations of plagioclase foliation do not correspond to those of biotite. It is also noted that the foliations appear to strike in directions orthogonal to the fractures in the fracture zones in the same depth interval. No significant change in foliation orientation was observed in Zones I to IV. Set V, however, whose mean orientation is 210/40 deg, is absent from the Zone IV interval, ranging from 872 to 905 m. (auth)

  1. Middle cretaceous crustal anatexis associated to contractional deformation on Eden's shear zone

    International Nuclear Information System (INIS)

    The Puerto Eden's igneous and metamorphic complex (PEIMC) is composed by amphibolite facies schists, melanocratic and leucocratic diatexites (with biotite in schlieren structure), and orthomylonites intruded by schlieren bearing porphyritic biotite monzogranite, tabular garnet - tourmaline and white mica - garnet leucogranites, pegmatitic felsic dikes, andesitic dikes, and biotite hornblende granodiorites belonging to the South Patagonian Batholith (SPB). This locality represent the westernmost outcrop of the Eastern Andean Metamorphic Complex (EAMC), situated at 49o8min. 20.seg S - 74o 23min.20seg. W, on the eastern margin of the SPB. A common relationship exists in convergent orogenic belts between a shear zone system, high-grade metamorphic rocks, and granites, which suggests a feedback relationship between crustal anatexis and contractional deformation that helps granite extraction and focusses granite ascent (Solar et al, 1998). The aim of this study is to constraint the temporal relationship between the magmatic and deformational evolution in Puerto Eden, associated to one or more events of crustal anatexis recorded. This work is based on geochemistry and K-Ar radiometric age data set previously presented as part of first author's MSc thesis related to the petrogenesis of PEIMC (au)

  2. Petrology of metabasites in the south of Arousan, northeastern Isfahan province

    Directory of Open Access Journals (Sweden)

    Fereshteh Bayat

    2012-10-01

    Full Text Available Metagabbro, metadiabase and metabasalt of the Chah Palang and Me'raji mountains associated with Lower Paleozoic metamorphites are situated in the south of Arousan. Metabasites of these areas are relatively similar in terms of mineralogy and geochemical characteristics. Rock-forming minerals of the Me'raji metabasites are feldspar, amphibole, biotite, sphene, epidote, chlorite ± calcite. Metagabbro and metadiabase of the Chah Palang area are similar to the Me'raji metabasites in mineralogy and geochemistry. Volcanic rocks are overlain by metagabbros and consist of plagioclase, biotite, sphene, sanidine, chlorite, epidote and iron oxides. The rigid dykes, which are found in the volcanic units are associated with metagabbros and mineralogically are similar to the metavolcanics. Amphibolitic dykes are composed of amphibole, plagioclase and biotite with preferred orientation. Metabasites show limited range of differentiation. Me'raji metabasites are basalt and trachy-basalt in composition, whereas the Chah Palang ones present basalt and trachy-basalt composition. Similar to metabasites of the other parts of Iran, the studied basic rocks demonstrate alkaline to transitional chemical characteristic and are formed in an extensional environment by low-degree partial melting of a garnet-spinel peridotite. Metamorphic episodes have changed the studied rocks to amphibolite and greenschist, but the primitive igneous textures are preserved.

  3. Cretaceous sedimentation and metamorphism of the western Alpine Schist protoliths associated with the Pounamu Ultramafic Belt, Westland, New Zealand

    International Nuclear Information System (INIS)

    The Pounamu Ultramafic Belt (PUB), part of the Alpine Schists, comprises a metamorphosed ophiolitic sequence overlain by a thin pelagic unit, a massive quartzofeldspathic biotite rock and quartzofeldspathic turbidites derived from a Torlesse/Otago Schist source. Constituent zircon populations from the biotite rock are euhedral/prismatic and are unabraded. One sample is near unimodal, with a U-Pb SHRIMP age of 106.6 ± 1.4 Ma (2σm), while the other has two peaks at 108.0 ± 1.6 Ma and 71.9 ± 1.8 Ma. The older age is interpreted to represent the age of igneous activity and sedimentation, while the younger peak is interpreted to represent the age of subsequent metamorphism. The whole-rock geochemistry of the biotite rock, its field distribution and zircon morphology are consistent with an origin by eruption of a dacitic air-fall tuff. The base of the Pounamu sequence divides predominantly psammitic Triassic metasediments to the east from intensely deformed, but regionally west-facing, Cretaceous metasediments to the west. These Cretaceous metasediments have undergone multiphase deformation and metamorphism by 72 Ma, a timing that contrasts markedly with previous interpretations for Jurassic amalgamation of the Haast Schists. (author)

  4. Lithostratigraphic units, petrography and chemical composition of the Mitu migmatitic complex in the surroundings of Mitu, Colombia

    International Nuclear Information System (INIS)

    Mitu complex migmatites rocks correlates with the province of Rio Negro - Juruena (Brazil). Mitu on the plategeologic 443 in an area of 1,115 km2 approximately where divided into three units called monzogranite of Mitu, pringamosa's granofels and gneiss Del Yi; units with macroscopic textural and structural differences, and similar mineralogical composition. The rocks from Mitu's monzogranite are classified petrographically as monzogranite with syenogranites, granodiorites and subordinated quartz feldspar granofels. The pringamosa's granofels groups, granofels and gneisses with homophonous migmatitic structures, nebulite, ophthalmic, schlieren and banded, of granitic composition and gneiss del Yi groups quartz tube feldspathic gneisses with biotite and large porphyroblasts alkaline feldspar by way of augen together with quartz-feldspar granofels bands with biotite. The essential minerals found in these units are quartz, potassium feldspar (microcline), plagioclase (andesine-oligoclase) and biotite. Accessory minerals are apatite, zircon, monazite, opaque, rutile, allanite, fluorite and hastingsite. Rocks from Mitu's migmatites complex are high potassium sub-alkaline, metaluminous and peraluminous affinity; correspond to grains of a type affinity ferrous and magnetite series, with enrichment of REE in samples with monazite.

  5. Application of SIMS to the analysis of environmental samples

    International Nuclear Information System (INIS)

    As an example of surface analysis of environmental samples, SIMS was applied to airborne particulates, fish otoliths (a calcareous ear-stone) and biotites (a rock-forming aluminosilicate mineral). Airborne particulates deposited on leaf surface were analyzed directly by fast atom bombardment (FAB)-SIMS using an O2 primary neutral beam. Some metal elements, such as Pb, of aerosol origin could be detected. Local areas of a thin section of an otolith were analyzed by FAB-SIMS. Line scans and images of secondary ions revealed seasonal periodicity in Sr, Na and K concentrations in the otolith that corresponded to the annual band structure. Surface alteration of acid-treated and naturally weathered biotites was studied by SIMS depth profiling using an O- primary ion. The depth profile of the acid-treated biotite showed the formation of an altered surface layer rich in Si. In contrast a thick altered surface layer was not observed and Al was held on the surface under natural weathering

  6. The Araxá Group in the South-Southwest Region of the Goiás State

    Directory of Open Access Journals (Sweden)

    Guillermo Rafael Beltran Navarro

    2013-06-01

    Full Text Available In the S – SW region of Goiás State, Brazil, the Araxá Group is constituted of a metasedimentary sequence containing schistoseand gneissic (garnet-biotite-quartz schists, feldspatic garnet-biotite-quartz schists, garnet-biotite-quartz paragneisses,with muscovite and locally amphibole, epidote, kyanite and staurolite. This sequence presents intercalations of metaultramaficrocks (serpentinite, actinolite schist, talc schist, chlorite schist, metamafic ones (amphibolite, amphibole schistcontaining or not garnet, garnet amphibolite and associated granitic bodies. Chemically, the Araxá Group metasedimentspresent peraluminous composition, showing enrichment in LILE, when compared with HFSE and REE, and displayingnegative anomalies of Nb, Ta, Sr, P and Ti. Their chemical composition is that of greywake and the chemical characteristicsof the sediments are generated in magmatic arcs. Isotopic data for Sm/Nd – model ages (TDM between 1,04 – 1,51 and1,76 – 2,26 Ga – and U/Pb (predominance of zircon with ages < 900 Ma suggest that these metasediments have Neoproterozoicrocks as the source rocks. Chemical and isotopic characteristics of the studied metasediments suggest that theirsource are rocks originated in magmatic arcs and that they were deposited in a fore arc basin developed in the margins ofNeoproterozoic island arcs.

  7. Volcanogenic Turonian and epiclastics of senonian in the Timok magmatic complex between Bor and the Tupižnica mountain, eastern Serbia

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    Đorđević Miodrag

    2005-01-01

    Full Text Available In the light of the findings presented in this paper, among the volcanic products of the Upper Cretaceous, referred to as "the first volcanic phase" (Drovenik, 1961, two lithostratigraphic units can be singled out within the Timok Magmatic Complex (TMC: - The lower one, consisting of volcanogenic, subaerial, dominantly hornblende andésite volcaniclastic, formed on land, and less abundant volcanic and sub-volcanic-hypoabyssal rocks. It is the main source of sulfide mine­ralization in Bor. It was formed before the Upper Turonian and consists of hornblende andésite and occasionally low biotite. Minor constituents are biotite-hornblende dacite and some andésite and dacite materials con­taining augite in addition to hornblende and biotite. - The upper one, from the Upper Turonian period when the volcanic activity of the region had ended, is marine deposited and epiclastic. Intercalated with Senonian marls, it is composed of land deposited Turonian volcanogenic material of all generations. Fresh material mostly consisting of hornblende andésite volcanoclastics prevails in it. Fresh epiclastics include ore mineral epiclasts. Epiclastics composed of epiclasts of hydro thermally altered rocks were observed which also include ore epiclasts. The ore epiclasts originate from copper ore. The boundary between the volcanogenic Turonian and the epiclastic deposits is a well-recognized unconformity. Table 1 in the text summarizes the main characteristics of the Turonian volcanogenic rocks, primarily those of volcaniclastics, as well as those of epiclastic deposits.

  8. Deformation partitioning and fabric development during shearing of felsic migmatites (Valpelline Series, NW Alps)

    Science.gov (United States)

    Pariani, Federico; Menegon, Luca; Bistacchi, Andrea; Malaspina, Nadia

    2014-05-01

    The relationships between partial melting and deformation in the continental lower crust are critical for understanding lithosphere rheology and the processes leading to melt segregation. In metapelitic rocks in the lower portions of the crust partial melting typically occurs via dehydration of biotite and is generally characterized by a negative volume change when garnet is produced as a peritectic phase. As a result, segregation of biotite-derived melt by fracturing resulting from dilational strain is not common. Hence segregation of biotite-derived melts in the lower crust is likely to be controlled by active deformation via creation of structural anisotropies (fabric), which define migration pathways from the grain-size to the kilometre scale. This study investigates the relations between deformation mechanisms of minerals, fabric development and grain- and meso-scale deformation partitioning in felsic migmatites. The study area is located in the Valpelline Series of the Dent Blanche Nappe in the north-western Alps, which represents a slice of pre-Alpine lower crust dominated by metapelitic migmatites (i.e. 'kinzigites' in the Alpine literature). The migmatites are stromatic and show a leucosome-melanosome interlayering defining the dominant foliation (S2), which forms along a sinistral shear zone at least 1 km thick and laterally continuous for at least 8 km. Ti-in biotite geothermometry, mineral inclusions in garnet, and literature data indicate that S2 formed at P, T conditions of 800-820°C, 0.4-0.7 GPa, during dehydration melting of biotite. The melanosomes have about 80 vol% of garnet + biotite + sillimanite and are very poor in quartz and feldspars, indicating almost complete removal of melt. Garnet forms slightly elongated grains wrapped by biotite and sillimanite layers. Compositional maps of the elongated garnet do not show any zonation. EBSD analysis indicates that the elongated garnets are actually clusters of individual grains with no internal

  9. Unraveling eclogite-facies fluid-rock interaction using thermodynamic modelling and whole-rock experiments: the in-situ eclogitization of metapelites from Val Savenca (Sesia Zone, Western Alps)

    Science.gov (United States)

    Jentsch, Marie; Tropper, Peter

    2015-04-01

    A common feature of HP and UHP terranes is the subduction of crustal rocks to great depths. Previous investigations have shown that this process is triggered by fluids present during an eclogite-facies metamorphic overprint. An examples is exposed in the metapelites at Val Savenca in the Sesia-Lanzo Zone, Italy where Alpine eclogite-facies metamorphism and fluid flow led to partial transformation of Variscan amphibolite-eclogite facies metapelites (garnet + biotite + sillimanite + K-feldspar + plagioclase + quartz) to zoisite ± jadeite + kyanite + phengite + quartz. This transformation took place under P-T conditions of 1.7 - 2.1 GPa at 600°C and low a(H2O) of 0.3-0.6. The replacement of plagioclase by jadeite + zoisite + kyanite + quartz takes place also along former fractures. Biotite is replaced by the assemblage phengite + omphacite ± kyanite adjacent to former plagioclase, otherwise by phengite + rutile/titanite. Garnet and clinopyroxene show variable compositions depending in which micro-domain (plagioclase or biotite) they grew. The extreme development of microdomains can best be studied by thermodynamic pseudosection modelling of individual microdomains using stoichiometric mixtures of protolith minerals from this domain and the program DOMINO (De Capitani & Petrakakis, 2010). The aim of these calculations was: 1.) to reproduce the observed mineral assemblage and 2.) to provide constraints on the amount of fluid present in the transformation. The results so far indicate that the amount of fluid was very low, otherwise paragonite would have formed instead of jadeite and reproduction of the observed mineral assemblage has only been partly successful so far since biotite is still stable in the calculations. In addition to understand the role of fluids in the mineralogical and textural transformation piston-cylinder experiments with a fresh, natural orthogneiss granulite from the Moldanubic Unit in upper Austria with the assemblage garnet + biotite + K

  10. Formation of garnet + corundum during isobaric cooling at UHT conditions: an example from pelitic granulites of the Highland Complex, Sri Lanka

    Science.gov (United States)

    Laksthitha Dharmapriya, Prasanna; Galli, Andrea; Prabath Malaviarachchi, Sanjeeva; Su, Ben-Xun

    2014-05-01

    Coexisting garnet and corundum have been reported from different rock types such as UHP rocks, aluminous eclogites, kimberlites and numerous granulites worldwide which experienced UHT conditions of 900-1050 °C at relatively high but not eclogitic pressures of 10-12 kbar. In pelitic granulites the assemblage garnet + corundum is usually interpreted to form at peak P during prograde heating along a clock-wise metamorphic path and subsequently breaks down during decompression to form sapphirine, cordierite-sapphirine-spinel or spinel-sillimanite bearing assemblages, depending on the PT-trajectory and bulk rock composition. In any cases, coexisting garnet + corundum are rarely preserved. Even less usual is the occurrence of garnet + corundum in pyroxene-free rocks. In this study, we report the occurrence of coexisting garnet + corundum within spinel- and corundum-bearing, orthopyroxene-free garnet-sillimanite-biotite-graphite gneisses from the Highland Complex (HC), Sri Lanka. In the investigated pelitic granulites, quartz-saturated domains and quartz-deficient domains are distinguishable. Quartz-saturated domains consist of quartz, plagioclase, alkali-feldspar, garnet-porphyroblasts and biotite flakes around garnet. Quartz-deficient domains are constituted of sillimanite, plagioclase, alkali-feldspar, corundum, spinel, biotite and two generations of garnet. Grt1 is coarse- to medium-grained (0.5-3 cm in diameter) and encloses rare Ti-rich biotite and numerous rutile needles and apatite rods. Grt2 is medium- to fine-grained (0.25-1 cm in diameter), contains rare sillimanite and/or spinel inclusions and is always associated with corundum. Corundum occurs in mutual contact with Grt2, partially embedded within rim area of Grt2 or as inclusions in Grt2. Rarely, tiny spinel inclusions can be observed in corundum. The chemistry of minerals preserved as inclusion in Grt1 indicates that pelitic granulites attained maximal P of 10.5-11 kbar at T around 850°C during their

  11. Systematics of hydrothermal alteration at the volcanic-hosted Falun Zn-Pb-Cu-(Au-Ag) deposit - implications for ore genesis, structure and exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    Science.gov (United States)

    Kampmann, Tobias C.; Jansson, Nils J.; Stephens, Michael B.; Majka, Jarosław

    2016-04-01

    The Palaeoproterozoic, volcanic-hosted Falun Zn-Pb-Cu-(Au-Ag) sulphide deposit was mined for base and precious metals during several centuries, until its closure in 1992. The deposit is located in a 1.9 Ga ore district in the Bergslagen lithotectonic unit, Fennoscandian Shield, south-central Sweden. Both the ores and their host rock underwent polyphase ductile deformation, and metamorphism under amphibolite facies and later retrograde conditions at 1.9-1.8 Ga (Svecokarelian orogenic system). This study has the following aims: (i) Classify styles and intensities of alteration in the hydrothermally altered zone at Falun; (ii) identify precursor rocks to hydrothermally altered rocks and their spatial distribution at the deposit; (iii) evaluate the chemical changes resulting from hydrothermal alteration using mass change calculations; and (iv) assess the pre-metamorphic alteration assemblages accounting for the observed metamorphic mineral associations in the altered rocks at Falun. Results will have implications for both the ore-genetic and structural understanding of the deposit, as well as for local and regional exploration. Metamorphic mineral associations in the altered rocks include biotite-quartz-cordierite-(anthophyllite) and, more proximally, quartz-anthophyllite-(biotite-cordierite/almandine), biotite-cordierite-(anthophyllite) and biotite-almandine-(anthophyllite). The proximal hydrothermally altered zone corresponds to intense chlorite-style alteration. Subordinate dolomite or calcite marble, as well as calc-silicate (tremolite, diopside) rocks are also present at the deposit. Metavolcanic rocks around the deposit are unaltered, weakly sericitized or sodic-altered. Immobile-element (e.g. Zr, TiO2, Al2O3, REE) systematics of the silicate-rich samples at and around the deposit suggest that the precursors to the hydrothermally altered rocks at Falun were predominantly rhyolitic in composition, dacitic rocks being subordinate and mafic-intermediate rocks

  12. Mobility of gold during metamorphism of the Dalradian in Scotland

    Science.gov (United States)

    Pitcairn, I. K.; Skelton, A. D. L.; Wohlgemuth-Ueberwasser, C. C.

    2015-09-01

    Mobility of Au and related metals during metamorphism has been suggested to be the source of metals enriched in orogenic Au deposits. This study investigates the mobility of Au, As, and Sb during metamorphism of the Dalradian metasedimentary rocks of Scotland. The metamorphic processes in the Dalradian of Scotland are extremely well studied, and the terrane is an ideal area to investigate mobility of these metals. Our results show that of the 25 major and trace elements analysed, only Au, As, Sb, S and volatile contents as shown by loss on ignition (LOI) values show systematic variation with the metamorphic grade of the samples. Average Au concentrations decrease from 1.1 ± 0.55 ppb and 0.72 ± 0.34 ppb in chlorite and biotite zone rocks down to 0.4 ± 0.22 ppb and 0.34 ± 0.13 ppb in kyanite and sillimanite zone rocks. Average As concentrations decrease from 4.8 ppm (range 0.5 to 17.8 ppm) and 1.96 ± 1.9 ppm in chlorite and biotite zone rocks down to 0.24 ± 0.15 ppm and 0.2 ± 0.12 ppm in kyanite and sillimanite zone rocks. Average Sb concentrations decrease from 0.18 ± 0.15 ppm and 0.11 ± 0.10 ppm in chlorite and biotite zone rocks down to 0.04 ± 0.02 ppm in both kyanite and sillimanite zone rocks. Sulphur and LOI concentrations also show significant decreases. Mass balance calculations indicate that compared to chlorite and biotite zone samples, sillimanite zone samples have an average mass loss of 62 ± 14%, 94 ± 4% and 74 ± 14% for Au, As, and Sb respectively. Every 1 km3 of chlorite-biotite zone mixed psammitic-pelitic protolith rock that is metamorphosed to sillimanite zone conditions would release 1.5 t Au, 8613 t As, 270 t Sb, and 1.02 Mt S. The mobility of these elements is strongly controlled by the paragenesis of sulphide minerals. Pyrite, sphalerite, galena and cobaltite (as well as gersdorffite) decrease in abundance with increasing metamorphic grade in the Dalradian metasedimentary rocks. A critical aspect of the sulphide paragenesis is the

  13. Redefinition and Significance of Metamorphism Xilinhot Group in Xilinhot Area, Inner Mongolia, China%内蒙古锡林浩特地区中元古代锡林浩特岩群的厘定及其意义

    Institute of Scientific and Technical Information of China (English)

    周文孝; 葛梦春

    2013-01-01

    Based on large scale geologic mapping and measuring section,the Xilin Col complex is divided into three parts:supracrustal rock,Late Proterozoic basic-uhrabasic rock and Early Paleozoic acid intrusive rocks.According to lithologic association and characteristics of deformation and metamorphism,biotite (garnet) plagioclase gneiss intercalated with several layers barred amphibolite,with thin layer magnetite quartzite on its top; medium-coarse biotite plagioclase gneiss and fine-grained felsic gneiss; lithologic association of migmatization banding biotite (hornblende) plagioclase gneiss and garnet monzonitic gneiss intercalated with barred amphibolite; sillimanite biotite plagioclase gneiss,barred biotite plagioclase gneiss,intercalated with garnet bearing biotite quartz schist.Comparison study on the different lithologic association,metamorphic characteristics and depositional environment of Baoyintu Group,Ailegemiao Formatio,Bainaimiao Group and others.This paper proposes to redefine these supercrustal rocks named "Xilinhot Group",which compose the Precambrian metamorphic basement of Xilin Col micro block.It's important to study the formation and development of Xilin Col micro block and the evolution of structural relationship between Siberia plate and North China plate.%通过大比例尺填图和剖面研究,将内蒙古锡林浩特地区的“锡林郭勒杂岩”解体分为3大部分:一套表壳岩、晚元古代基性-超基性侵入岩和早古生代酸性侵入岩.在此基础上根据变质岩的岩性组合和变形变质特点,可将其中的表壳岩化分为4个岩性段:黑云(石榴石)斜长片麻岩,间夹多层条纹状斜长角闪岩,在其顶部多见薄层含磁铁石英岩;中粗粒黑云斜长片麻岩和细粒长英质片麻岩;混合岩化条带状黑云(角闪)斜长片麻岩,含石榴石黑云二长片麻岩夹条纹状斜长角闪岩组合;夕线石黑云斜长片麻岩,条纹状黑云斜长片麻岩,间夹含石榴石黑云母

  14. Geological Characteristics of the Furong Tin Orefield, Hunan,40Ar-39Ar Dating of Tin Ores and Related Granite and Its Geodynamic Significance for Rock and Ore Formation

    Institute of Scientific and Technical Information of China (English)

    MAO Jingwen; LI Xiaofeng; CHEN Wen; LAN Xiaoming; WEI Shaoliu

    2004-01-01

    Furong, Hunan, is a large tin orefield discovered in China in recent years, which is mainly of the skarn-greisenchlorite type. On the basis of the geological characteristics of the orefield, 40Ar-39Ar dating was performed on muscovite from greisen-type tin ore and biotite from related amphibole-biotite granite, which yielded three sets of age data, i.e., a plateau age of 157.5±0.3 Ma and an i sochron age of 156.9±3 Ma for amphibole-biotite granite; a plateau age of 156.1 ±0.4Ma and an isochron age of 155.7±1.7 Ma for the Sanmen greisen-type tin ore; and a plateau age of 160.1±0.9 Ma and an isochron age of 157.5±1.5 Ma for the Taoxiwo greisen-type tin ore. The three sets of age data coincide well with each other They not only accurately reflect the timing of rock and ore formation but also indicate close relations between granite and tin deposits. In addition, the plateau ages of all three sets suggest that no subsequent thermal perturbation event occurred after the formation of granite and tin deposits. The Furong tin orefield is a component part of the southern Hunan large tungsten-tin polymetallic deposit concentration area and also a representative deposit formed in the time interval of 160-135 Ma in four peaks of Mesozoic tungsten-tin mineralization in the South China region. They might still correspond to the middle and late stages of the major geodynamic transition from a N-S- to an E-W-direction in eastern China.

  15. Occurrence of Tourmaline in Metasedimentary Rocks of the Isua Supracrustal Belt, Greenland: Implications for Ribose Stabilization in Hadean Marine Sediments

    Science.gov (United States)

    Mishima, Shinpei; Ohtomo, Yoko; Kakegawa, Takeshi

    2016-06-01

    Abiotic formation of RNA was important for the emergence of terrestrial life, but the acknowledged difficulties of generating and stabilizing ribose have often raised questions regarding how the first RNA might have formed. Previous researchers have proposed that borate could have stabilized ribose; however, the availability of borate on the early Earth has been the subject of intense debate. In order to examine whether borate was available on the early Earth, this study examined metasedimentary rocks from the Isua Supracrustal Belt. Garnet, biotite, and quartz comprise the major constituents of the examined rocks. Field relationships and the chemical compositions of the examined rocks suggest sedimentary origin. The present study found that garnet crystals contain a number of inclusions of tourmaline (a type of borosilicate mineral). All tourmaline crystals are Fe-rich and categorized as schorl. Both garnet and tourmaline often contain graphite inclusions and this close association of tourmaline with garnet and graphite has not been recognized previously. Garnet-biotite and graphite geothermometers suggest that the tourmaline in garnet experienced peak metamorphic conditions (~500 °C and 5 kbar). The mineralogical characteristics of the tourmaline and the whole rock composition indicate that the tourmaline formed authigenically in the sediment during diagenesis and/or early metamorphism. Clay minerals in modern sediments have the capability to adsorb and concentrate borate, which could lead to boron enrichment during diagenesis, followed by tourmaline formation under metamorphic conditions. Clay minerals, deposited on the early Archean seafloor, were the precursors of the garnet and biotite in the examined samples. The studied tourmaline crystals were most likely formed in the same way as modern tourmaline in marine sediments. Therefore, boron enrichment by clays must have been possible even during the early Archean. Thus, similar enrichment could have been

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

    Science.gov (United States)

    Smith, M. P.

    2007-01-01

    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.

  17. Petrology of the anorogenic, oxidised Jamon and Musa granites, Amazonian Craton: implications for the genesis of Proterozoic A-type granites

    Science.gov (United States)

    Dall'Agnol, Roberto; Rämö, O. Tapani; de Magalhães, Marilia Sacramento; Macambira, Moacir José Buenano

    1999-03-01

    The 1.88 Ga Jamon and Musa granites are magnetite-bearing anorogenic, A-type granites of Paleoproterozoic age. They intrude the Archaean rocks of the Rio Maria Granite-Greenstone Terrain in the eastern part of the Amazonian Craton in northern Brazil. A suite of biotite±amphibole monzogranite to syenogranite, with associated dacite porphyry (DP) and granite porphyry (GP) dykes, dominates in these subalkaline granites that vary from metaluminous to peraluminous and show high FeO/(FeO+MgO) and K 2O/Na 2O. In spite of their broad geochemical similarities, the Jamon and Musa granites show some significant differences in their REE patterns and in the behaviour of Y. The Jamon granites are related by fractional crystallisation of plagioclase, potassium feldspar, quartz, biotite, magnetite±amphibole±apatite±ilmenite. Geochemical modelling and Nd isotopic data indicate that the Archaean granodiorites, trondhjemites and tonalites of the Rio Maria region are not the source of the Jamon Granite and associated dyke magmas. Archaean quartz diorites, differentiated from the mantle at least 1000 m.y. before the emplacement of the granites, have a composition adequate to generate DP and the hornblende-biotite monzogranite magmas by different degrees of partial melting. A larger extent of amphibole fractionation during the evolution of the Musa pluton can explain some of the observed differences between it and the Jamon pluton. The studied granites crystallised at relatively high fO 2 and are anorogenic magnetite-series granites. In this aspect, as well as concerning geochemical characteristics, they display many affinities with the Proterozoic A-type granites of south-western United States. The Jamon and Musa granites differ from the anorthosite-mangerite-charnockite-rapakivi granite suites of north-eastern Canada and from the reduced rapakivi granites of the Fennoscandian Shield in several aspects, probably because of different magmatic sources.

  18. LA-ICP-MS U-Pb apatite dating of Lower Cretaceous rocks from teschenite-picrite association in the Silesian Unit (southern Poland

    Directory of Open Access Journals (Sweden)

    Szopa Krzysztof

    2014-08-01

    Full Text Available The main products of volcanic activity in the teschenite-picrite association (TPA are shallow, sub-volcanic intrusions, which predominate over extrusive volcanic rocks. They comprise a wide range of intrusive rocks which fall into two main groups: alkaline (teschenite, picrite, syenite, lamprophyre and subalkaline (dolerite. Previous 40Ar/39Ar and 40K/40Ar dating of these rocks in the Polish Outer Western Carpathians, performed on kaersutite, sub-silicic diopside, phlogopite/biotite as well as on whole rock samples has yielded Early Cretaceous ages. Fluorapatite crystals were dated by the U-Pb LA-ICP-MS method to obtain the age of selected magmatic rocks (teschenite, lamprophyre from the Cieszyn igneous province. Apatite-bearing samples from Boguszowice, Puńców and Lipowa yield U-Pb ages of 103± 20 Ma, 119.6 ± 3.2 Ma and 126.5 ± 8.8 Ma, respectively. The weighted average age for all three samples is 117.8 ± 7.3 Ma (MSWD = 2.7. The considerably smaller dispersion in the apatite ages compared to the published amphibole and biotite ages is probably caused by the U-Pb system in apatite being less susceptible to the effects of hydrothermal alternation than the 40Ar/39Ar or 40K/40Ar system in amphibole and/or biotite. Available data suggest that volcanic activity in the Silesian Basin took place from 128 to 103 Ma with the the main magmatic phase constrained to 128-120 Ma.

  19. P-T-t-D paths of the North Himalayan metamorphic rocks: Implications for the Himalayan orogeny

    Science.gov (United States)

    Ding, Huixia; Zhang, Zeming; Hu, Kaiming; Dong, Xin; Xiang, Hua; Mu, Hongchen

    2016-06-01

    Metamorphic P-T-t-D paths have been determined in the Yardoi gneiss dome of the eastern Himalaya that place new constraints on the genesis of the North Himalayan Gneiss Dome and tectonic evolution of the Himalayan orogen. Our study shows that the schists from the Yardoi dome underwent at least three stages of metamorphism and deformation. The first stage of prograde metamorphism is represented by the core of porphyroblastic garnet, showing distinct growth compositional zoning, and hosting mineral inclusions of biotite, muscovite, quartz and ilmenite; the curved inclusion trails define the first stage of deformation foliation (S1). The second stage of peak metamorphism is represented by the rim of porphyroblastic garnet and the aligned matrix minerals of biotite, muscovite, plagioclase, quartz, kyanite and staurolite, which define the main deformation foliation (S2). The third stage of retrograde metamorphism is characterized by occurrence of biotite, plagioclase, muscovite and sillimanite within the distributed shear bands, which define the late deformation foliation (S3). Phase equilibrium modeling reveals that Yardoi schists witnessed a peak metamorphism of upper amphibolite-facies under P-T conditions of 7-8 kbar and 615-665 °C, and records a clockwise P-T-t-D path with a prograde process of both temperature and pressure increase and subsequent retrogression of isothermal decompression. The zircon U-Pb dating indicates that the prograde process occurred during the Middle Eocene of 48-36 Ma and the retrograde metamorphism probably lasted to ca. 16 Ma. The present result shows that the formation of the Yardoi schists was related to the subduction and exhumation of Indian crust, the initial collision of Indian and Asian continents occurred at ca. 50 Ma, the northeastern margin of the Indian continent was shallowly underthrusted beneath the Asian continent, and distinct tectonic discontinuity is present in the Greater Himalayan Sequence.

  20. Timing and conditions of peak metamorphism and cooling across the Zimithang Thrust, Arunachal Pradesh, India

    Science.gov (United States)

    Warren, Clare J.; Singh, Athokpam K.; Roberts, Nick M. W.; Regis, Daniele; Halton, Alison M.; Singh, Rajkumar B.

    2014-07-01

    The Zimithang Thrust juxtaposes two lithotectonic units of the Greater Himalayan Sequence in Arunachal Pradesh, NE India. Monazite U-Pb, muscovite 40Ar/39Ar and thermobarometric data from rocks in the hanging and footwall constrain the timing and conditions of their juxtaposition across the structure, and their subsequent cooling. Monazite grains in biotite-sillimanite gneiss in the hanging wall yield LA-ICP-MS U-Pb ages of 16 ± 0.2 to 12.7 ± 0.4 Ma. A schistose gneiss within the high strain zone yields overlapping-to-younger monazite ages of 14.9 ± 0.3 to 11.5 ± 0.3 Ma. Garnet-staurolite-mica schists in the immediate footwall yield older monazite ages of 27.3 ± 0.6 to 17.1 ± 0.2 Ma. Temperature estimates from Ti-in-biotite and garnet-biotite thermometry suggest similar peak temperatures were achieved in the hanging and footwalls (~ 525-650 °C). Elevated temperatures of ~ 700 °C appear to have been reached in the high strain zone itself and in the footwall further from the thrust. Single grain fusion 40Ar/39Ar muscovite data from samples either side of the thrust yield ages of ~ 7 Ma, suggesting that movement along the thrust juxtaposed the two units by the time the closure temperature of Ar diffusion in muscovite had been reached. These data confirm previous suggestions that major orogen-parallel out-of-sequence structures disrupt the Greater Himalayan Sequence at different times during Himalayan evolution, and highlight an eastwards-younging trend in 40Ar/39Ar muscovite cooling ages at equivalent structural levels along Himalayan strike.

  1. Petrology and radiogeology of the Stripa pluton

    International Nuclear Information System (INIS)

    Both the quartz monzonite and the metavolcanic leptite which it intruded are strongly fractured. Two stages of fracture filling are evident; an earlier stage encompassing quartz, sericite, feldspar, epidote, and chlorite, and a later stage dominated by carbonate minerals. The Stripa quartz monozite is chemically and mineralogically distinct from other plutons in the region. Muscovite is the predominant mica in the quartz monzonite; biotite has been altered to chlorite, hornblende is absent, and accessory minerals are scarce. In contrast, in other plutons in the Stripa region, biotite and hornblende are prominent mafic minerals and accessory minerals are abundant. The Stripa quartz monzonite is also considerably more radioactive than the the leptite and other plutons in the region. Uranium and thorium abundances are both approx. 30 ppM, considerably higher than in normal granitic rocks where the thorium-to-uranium ratio generally exceeds 2. Potassium-argon dating of muscovite from the Stripa quartz monzonite indicates that this rock may be older, at 1691 million years than granitic rock of the neighboring Gusselby and Kloten massifs, whose ages, based on K-Ar dating of biotite, are respectively 1604 and 1640 m.y. Heat flow and heat productivity considerations show that although Stripa quartz monzonite contains high abundances of radioelements, the pluton has little efect on the regional heat flow. If it occurs in a layered plutonic setting, it is not more than 1.5 km thick; otherwise it may comprise a stock, dike, or border phase that is relatively small compared with the large granitic plutons exposed in the region

  2. Indicator minerals as guides to base metal sulphide mineralisation in Betul Belt, central India

    Indian Academy of Sciences (India)

    Biswajit Ghosh; M N Praveen

    2008-08-01

    Zn-bearing minerals that act as indicator minerals for base metal sulphide mineralization from the Proterozoic Betul Belt,central India with special emphasis on their genetic significance have been discussed.Sulphide mineralisation is hosted by the felsic volcanic rocks and has similarities with volcanic-hosted massive sulphide deposits in other parts of the world.Synvolcanic hydrothermal alteration is crudely zoned with an inner high Mg-Ca core and an outer wider envelop of Al-Fe rich mineral assemblage.Most of the prospects have strata bound,moderately to steeply dipping, multiple,sub-parallel sheet like ore bodies composed of disseminated and semi-massive to massive ores.Zn-bearing spinel,staurolite,biotite and ilmenite typically occur within the foot-wall altera- tion zones in close proximity to the sulphide mineralization.Zincian spinel is ubiquitous irrespective of the nature of alteration zone.Zincian staurolite is nearly absent in Mg-Ca alteration zones but commonly present in Al-Fe alteration zone along with zincian ilmenite.Zn-bearing biotite in intimate association with zincian spinel is generally found in Mg-Ca alteration zone and in the transition to Al-Fe alteration zone.Most of these indicator minerals can be considered as products of desulphidation of sphalerite during metamorphism.Mechanisms other than desulphidation like formation of gahnite by overstepping of the zinc saturation limit of biotite during retrogression to chlorite and formation of zincian staurolite at the expense of gahnite is also recorded.Field presence of these minerals has immense significance in exploration in Betul Belt as they occur in close spatial relationship with the sulphide rich zones and therefore act as direct vectors to ore.

  3. Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

    Science.gov (United States)

    Zeitlhofer, Helga; Grasemann, Bernhard; Petrakakis, Konstantin

    2016-06-01

    Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO2 contents and high amounts of MgO and K2O; these rocks have high Ba (800-3000 ppm) and Sr (250-1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb-Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334-318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330-310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an

  4. The post-collisional volcanism of northern Tunisia: Petrology and evolution through time

    Science.gov (United States)

    Halloul, Néji; Gourgaud, Alain

    2012-02-01

    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.

  5. Isotopic evidence of Middle Proterozoic magmatism from Bombay High Field: Implications to crustal evolution of western offshore of India

    Indian Academy of Sciences (India)

    S S Rathore; A R Vijan; M P Singh; B N Prabhu; Anand Sahu

    2004-03-01

    Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67Ma with an initial 87Sr/86Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43Ma and 1465 ± 43Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42Ma and 1425 ± 40Ma with an overall mean age of 1438 ± 19Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield.

  6. Rb–Sr and Sm–Nd study of granite–charnockite association in the Pudukkottai region and the link between metamorphism and magmatism in the Madurai Block

    Indian Academy of Sciences (India)

    M Chandra Sekaran; Rajneesh Bhutani; S Balakrishnan

    2016-04-01

    Pudukkottai region in the northeastern part of the Madurai Block exposes the garnetiferous pink granite that intruded the biotite gneiss. Charnockite patches are associated with both the rock types. Rb–Sr biotite and Sm–Nd whole-rock isochron ages indicate a regional uplift and cooling at ∼550 Ma. The initialNd isotope ratios (ε^t_{Nd} = −20 to −22) and Nd depleted-mantle model ages (T_{DM} = 2.25 to 2.79 Ga) indicate a common crustal source for the pink-granite and associated charnockite, while the biotite gneiss and the charnockite within it represent an older crustal source (ε^t_{Nd} = −29 and T_{DM} =>3.2 Ga). TheRb–Sr whole-rock data and initial Sr–Nd isotope ratios also help demonstrate the partial but systematic equilibration of Sr isotope and Rb/Sr ratios during metamorphic mineral-reactions resulting in an ‘apparent whole-rock isochron’. The available geochronological results from the Madurai Block indicate four major periods of magmatism and metamorphism: Neoarchaean–Paleoproterozoic, Mesoproterozoic, mid-Neoproterozoic and late-Neoproterozoic. We suggest that the high-grade and ultrahigh-temperature metamorphism was preceded by magmatism which ‘prepared’ the residual crust to sustain the high P–T conditions. There also appears to be cyclicity in the tectono-magmatic events and an evolutionary model for the Madurai Block should account for the cyclicity in the preserved records.

  7. Structural, petrological and geochronological analysis of the lithotypes from the Pien region (Parana State, Brazil) and adjacences

    International Nuclear Information System (INIS)

    The Pien area presents the major geotectonic domains separated by the Pien Shear Zone (PSZ). The northern one is the Rio Pien Granite-Mylonitic Suite composed by calc-alkaline granitoids of Neoproterozoic age. The southern domain is represented by the Amphibolite-Granulite where high grade metamorphism took place at the end of paleoproterozoic time. Considering the identified lithotypes, their geochemical affinity (particularly the Ti, Cr, Ni and REE content) and the geological context observed in the area, a geotectonical model of active continental margin related to subduction SSZ (Supra-Subduction Zone) is proposed. K-Ar on plagioclase from gabbronorites gave Neoproterozoic ages although Sm-Nd whole rock isochron yielded Paleoproterozoic ages. Based in geochemical data, it is proposed that the biotite gneiss and biotite-amphibole-gneiss which occur near the PSZ have a shoshonitic to high-K calc-alkaline features which are characteristic of active continental margins. K-Ar on biotite extracted from these rocks, gave Neoproterozoic ages. The available radiometric data for the Rio Pien mylonitic granitoids show that between 650-595 Ma the generation, deformation and cooling below the isotherm of 250 deg C occurred. On the other hand, the geochronological data for the Agudos do Sul Massif are in the 590-570 Ma interval showing its younger generation. The Sr87 / Sr86 initial ratios for both granitoids suggest more involvement of the continental crust in the origins of Agudos do Sul granitic Massif. The analyses of the entire set of the available data for the Pien area allows the suggestion of a geotectonic scenery related to the evolution of an active continental margin during the collages associated to the Brasiliano Cycle

  8. Características petrográficas y geoquímicas de la Tonalita La Ovejería, borde oriental de la Sierra del Aconquija, Tafí del Valle, Tucumán: integración con la Granodiorita El Infiernillo

    Directory of Open Access Journals (Sweden)

    Castro, Antonio

    2011-12-01

    Full Text Available The La Ovejería Tonalite is a N-S elo ngated body that crops out on the eastern side of the Sierra del Aconquija, west of of Tafi del Valle, Tucumán Province, Argentina. It is located just south of thelarger, and probably genetically related, El Infiernillo Granodiorite. The studied pluton has a zoning determined by different grain sizes and mineralogies: the northern outcrops are medium-grained and composed of plagioclase, quartz scarce microcline, and biotite and pistacite (± tourmaline as major accessories; the southern part of the intrusive is fine grained and composed of plagioclase, quartz scarce microcline, and biotite and sphene as accessory minerals. Two meter thick granitic dikes cross-cut the tonalites. The tonalite is calc-alkaline and peraluminous, with an ASI between 1.10 and 1.48. It intrudes metamorphic basement rocks composed of low grade schists that are characterized by an increase in static metamorphism, by syntectonic intrusions and by the intensity of flow folds.The emplacement of the La Ovejería Tonalite probably occurred during the Lower Paleozoic and was structurally controlled by the Tafi Megafracture, like the other intrusive bodies of the area. The El Infiernillo intrusive is composed of a two-mica (± tourmaline equigranular granodiorite main facies and a biotite and epidote bearing (without primary muscovite tonalitic border facies. According to field relations and petrographic, geochemical and structural data, the La Ovejería Tonalite may correspond to the northern border facies of the El Infiernillo intrusive.

  9. Cooling age record of domal uplift in the core of the Higher Himalayan Crystallines (HHC), southwest Zanskar, India

    International Nuclear Information System (INIS)

    The cooling and tectonic history of the Higher Himalayan Crystallines (HHC) in southwest Zanskar (along the Kishtwar-Padam traverse) is constrained by K-Ar biotite and fission-track (FT) apatite and zircon ages. A total of nine biotite samples yields ages in the range of 14-24 Ma, indicating the post-metamorphic cooling of these rocks through ∼ 300 degC in the Miocene. Overall, the ages become younger away from the Zanskar Shear Zone (ZSZ), which marks the basement-cover detachment fault between the HHC and the Tethyan sedimentary zone, towards the core of the HHC. The same pattern is also observed for the FT apatite ages, which record the cooling of the rocks through ∼ 120 degC. The apatite ages range from 11 Ma in the vicinity of the ZSZ to 4 Ma at the granitic core of the HHC. This pattern of discordant cooling ages across the HHC in southwest Zanskar reveals an inversion of isotherms due to fast uplift-denudation (hence cooling) of the HHC core, which is, in turn, related to domal uplift within the HHC. The Chisoti granite gneiss is the exposed domal structure along the studied traverse. Cooling history of two granite gneisses at the core of the HHC is also quantified with the help of the biotite, zircon and apatite ages; the time-temperatures thus obtained indicate a rapid pulse of cooling at ∼ 6 Ma, related to accelerated uplift-denudation of the HHC core at this time. Long-term denudation rates of 0.5-0.7 mm/yr are estimated for the high-grade rocks of the Higher Himalaya in southwest Zanskar over the past 4.0-5.5 m.yr. (author)

  10. "Gris Quintana": a Spanish granite from the Past into the Future.

    Science.gov (United States)

    José Tejado, Juan; Mota, M. Isabel; Pereira, Dolores

    2014-05-01

    "Gris Quintana" is a medium-grained, biotite and amphibole granodiorite extracted in the Pluton of Quintana de la Serena (Extremadura, Spain). It is a constant light grey granite from the Hercynian geologic with excellent physicomechanical and physicochemical properties. The granodiorite is composed of plagioclase, biotite, quartz and alkali feldspar, with accessory allanite, titanite, apatite, zircon and ilmenite, mostly as inclusions within the biotite crystals. This commercial variety is extracted from many quarries in the late Hercynian plutons located in the Iberian Massif in Spain period (transition between Central Iberian and Ossa-Moren Zones), having large reserves of granite. Many of the quarries have their own transformation factory (high production zone), with which the sector is offered an endless variety of finishes and constructive rock typologies. A wide range of solutions to architects and designers are offered. Gris Quintana granite is one of the materials with highest technological benefits that are used in arquitecture. "Gris Quintana" granite has been used since ancient times, not only at a regional, but also at national and international level: paving, building (structural, exterior façadas, interior uses), urban decoration and funeral art. It can be found in monuments and more recently, in buildings of different styles and uses, that stand out in beauty and splendor, lasting in time. Some singular works in "Gris Quintana" granite all over the world: extension to the "Congreso de Diputados" (Parliament) in Madrid, "Puerta de San Vicente" in Madrid, Andalucia Parliament columns in Sevilla, New Senate Buiding in Madird, "Gran Vía" pavement in Madrid, "Teatro Real façade" in Madrid… "Gris Quintana" granite accomplishes all the requirements for its nomination as Global Heritage Stone Resource, for both its use in construction and for artistic purposes.

  11. Age of Cu-Au mineralisation, Cloncurry district, eastern Mt Isa Inlier, Queensland, as determined by 40Ar/39Ar dating

    International Nuclear Information System (INIS)

    The 40Ar/39Ar dating of alteration biotite. muscovite and amphibole from a number of post-peak metamorphic Cu-Au deposits and alteration systems in the Cloncurry district. north Queensland has determined the timing of mineralisation and hydrothermal activity. Alteration biotite from the Ernest Henry Cu-Au, Starra Au-Cu, and Mt Elliott Cu-Au deposits, sericite associated with hematite breccias in the Wimberu Granite, muscovite from an albitite pipe that intrudes the Gilded Rose Breccia. And sericite from a granitoid near the Osborne Cu-Au deposit. yield ages which are broadly contemporaneous with the late ca 1510-1485 Ma phases of the Williams and Naraku Batholiths. Hornblende and biotite alteration, which pre-date Cu-Au mineralisation at Osborne. give a maximum age of ca 1540 Ma for the deposit. which is also a probable minimum age for peak metamorphism. Metamorphic minerals from the vicinity of Osborne yield dates which are significantly older (ca 1590-1570 Ma) than those from the hydrothermal phases. Dating by the K-Ar method of red. Hematitic K-feldspars which are regionally common in the Cloncurry district was not effective as the mineral yields ages up to 300 million years younger than coexisting alteration sericite. The 40Ar/39Ar age spectra obtained from most hydrothermal phases in the Eastern Fold Belt. Mt Isa Inlier commonly contain flat parts which comprise a large proportion of the released gas and are indicative of rapid cooling through the temperature of partial closure to Ar diffusion for the respective minerals. Copyright (1998) Blackwell Science Asia

  12. 40Ar/39Ar constraints on the timing and history of amphibolite facies gold mineralisation in the Southern Cross area, Western Australia

    International Nuclear Information System (INIS)

    The Southern Cross Greenstone Belt in Western Australia contains structurally controlled, hydrothermal gold deposits which are thought to have formed at or near the peak of amphibolite facies regional metamorphism during the Late Archaean. Although the geological features of deposits in the area are well documented. conflicting genetic models and ore-fluid sources have been used to explain the observed geological data. This paper presents new 40Ar/39Ar data which suggest that the thermal history of the Southern Cross area after the peak of regional metamorphism was more complex than has previously been suggested. After the main gold mineralisation event prior to ca 2620 Ma, the 40Ar/39Ar ages from amphiboles and biotites sampled from the alteration selvages of gold-bearing veins indicate that temperatures remained elevated in the region of 500 deg C for between 20 and 70 million years. These amphiboles and biotites from individual deposits yield ages that are in good agreement with one another to a high precision. implying increased cooling rates after the long period of elevated temperatures. Along the Southern Cross Greenstone Belt. however. amphibole-biotite pairs from the alteration selvages of gold-bearing quartz veins. while remaining in good agreement with one another, vary between deposits from ca 2560 Ma to ca 2440 Ma. Amphiboles from metabasalts that are associated with regional metamorphism and not hydrothermal alteration contain numerous exsolution lamellae that reduce the effective closure temperature of the amphiboles and yield geologically meaningless ages. These age relationships show that the thermal history of the area did not follow a simple cooling path and the area may have been tectonically active for a long period after the main gold mineralisation event before ca 2620 Ma. Such data may provide important constraints on subsequent genetic modelling of gold mineralisation and metamorphism. Copyright (1998) Blackwell Science Asia

  13. Mineralogic Investigation into Occurrence of High Uranium Well Waters in Upstate South Carolina USA

    Energy Technology Data Exchange (ETDEWEB)

    R Warner; J Meadows; S Sojda; V Price; T Temples; Y Arai; C Fleisher; B Crawford; P Stone

    2011-12-31

    High levels of U (up to 5570 {micro}g/L) have been discovered in well waters near Simpsonville, South Carolina, USA. In order to characterize the mineralogical source of the U and possible structural controls on its presence, a deep (214 m) well was cored adjacent to one of the enriched wells. The highest gamma-ray emissions in the recovered core occur in coarse biotite granite at a depth just below 52 m. A slickenlined fault plane at 48.6 m and narrow pegmatite layers at depths of 113, 203 and 207 m also yield high gamma-ray counts. Thin sections were made from the above materials and along several subvertical healed fractures. Uraninite and coffinite are the principal U-rich minerals in the core. Other U-bearing minerals include thorite and thorogummite, monazite, zircon and allanite. Primary uraninite occurs in the biotite granite and in pegmatite layers. Secondary coffinite is present as tiny (<5 {micro}m) crystals dispersed along fractures in the granite and pegmatites. Coffinite also occurs along the slickenlined fault plane, where it is associated with calcite and calcic zeolite and also replaces allanite. Coffinite lacks radiogenic Pb, hence is considerably younger than the uraninite. Dissolution of partially oxidized Ca-rich uraninite occurring in the surficial biotite granite (or secondary coffinite in fracture zones) is likely the main source for the current high levels of U in nearby area wells. The high-U well waters have a carbonate signature, consistent with pervasive calcite vein mineralization in the core. Aqueous speciation calculations suggest U transport as an uranyl (U{sup 6+}) hydroxyl-carbonate complex. Later reduction resulted in secondary precipitation along fractures as a U{sup 4+} mineral (i.e., coffinite).

  14. Geology and pegmatites of part of the Fourmile area, Custer County, South Dakota

    Science.gov (United States)

    Lang, Andrew J.; Redden, Jack Allison

    1953-01-01

    The Fourmile area, Custer County, S. Dak., is underlain by pre-Cambrian metamorphic rocks that surround the granitic core of the Black Hills. The main structure in the area is the upright limb of an overturned anticline that plunges about 30 ? S. 10 ? E. Three units of metamorphic rocks are described that have a total thickness of at least 7, 700 feet. The oldest of these units, a quartz-mica schist, is more than 6, 500 feet thick. The overlying unit, about 200 feet thick, is composed of thin beds of amphibolite and hornblende schist, lime-silicate rock, cordierite-biotite schist, microcline-biotite schist, and other types of rocks. The youngest unit, a quartz-mica-feldspar schist, is more than 1,000 feet thick. The presence of kyanite, staurolite, cordierite, and sillimanite in the rocks indicates that they have been subjected to high-grade metamorphism. About 420 pegmatites were mapped in the quartzmica-schist and the quartz-mica-feldspar schist. A few thin pegmatites in the third unit were not mapped. Most of these are concordant with the schistosity and relict (?) bedding of the enclosing metamorphic rocks. They are as much as 250 feet thick and range from 10 to 2, 600 feet in length. Nine peqmatites are zoned and classified as heterogeneous. The remainder are homogeneous and are poorly zoned. The major constituents are plaqioclase, quartz, perthite, and muscovite. The accessory minerals are tourmaline, apatite, garnet, and biotite. Beryl was observed in 15 peqmatites. The heterogeneous pegmatites contain commercial deposits of potash feldspar, mica (sheet and scrap), and beryl.

  15. Petrology and radiogeology of the Stripa pluton

    Energy Technology Data Exchange (ETDEWEB)

    Wollenberg, H.; Flexser, S.; Andersson, L.

    1980-12-01

    Both the quartz monzonite and the metavolcanic leptite which it intruded are strongly fractured. Two stages of fracture filling are evident; an earlier stage encompassing quartz, sericite, feldspar, epidote, and chlorite, and a later stage dominated by carbonate minerals. The Stripa quartz monozite is chemically and mineralogically distinct from other plutons in the region. Muscovite is the predominant mica in the quartz monzonite; biotite has been altered to chlorite, hornblende is absent, and accessory minerals are scarce. In contrast, in other plutons in the Stripa region, biotite and hornblende are prominent mafic minerals and accessory minerals are abundant. The Stripa quartz monzonite is also considerably more radioactive than the the leptite and other plutons in the region. Uranium and thorium abundances are both approx. 30 ppM, considerably higher than in normal granitic rocks where the thorium-to-uranium ratio generally exceeds 2. Potassium-argon dating of muscovite from the Stripa quartz monzonite indicates that this rock may be older, at 1691 million years than granitic rock of the neighboring Gusselby and Kloten massifs, whose ages, based on K-Ar dating of biotite, are respectively 1604 and 1640 m.y. Heat flow and heat productivity considerations show that although Stripa quartz monzonite contains high abundances of radioelements, the pluton has little efect on the regional heat flow. If it occurs in a layered plutonic setting, it is not more than 1.5 km thick; otherwise it may comprise a stock, dike, or border phase that is relatively small compared with the large granitic plutons exposed in the region.

  16. Influence of the nonexchangeable potassium of mica on radiocesium uptake by paddy rice

    International Nuclear Information System (INIS)

    A pot cultivation experiment was conducted to elucidate the influence of the nonexchangeable potassium (K) of mica on radiocesium (137Cs) uptake by paddy rice (Oryza sativa L. cv. Koshihikari), and to evaluate the potential of mica application as a countermeasure to reduce radiocesium transfer from soil to paddy rice. The increase in the exchangeable K concentrations of soils, measured before planting, due to mica (muscovite, biotite, and phlogopite) application was negligible. However, in trioctahedral mica (biotite and phlogopite)-treated soil, the release of nonexchangeable K from the mica interlayer maintained the soil-solution K at a higher level during the growing season in comparison to the control, and consequently decreased the 137Cs transfer factor for brown rice (TF). The sodium tetraphenylboron (TPB)-extractable K concentration of the soils, measured before planting, was strongly negatively correlated with the TF, whereas the exchangeable K concentration of the soils, also measured before planting, was not correlated with the TF. Therefore, we conclude that TPB-extractable K is more reliable than exchangeable K as a basis of fertilizer recommendations for radiocesium-contaminated paddy fields. Phlogopite-treated soils exhibited higher TPB-extractable K concentrations and lower TF values than biotite-treated soils. We thus conclude that phlogopite application is an effective countermeasure to reduce radiocesium uptake in paddy rice. - Highlights: • Nonexchangeable K of added trioctahedral mica decreased 137Cs uptake by paddy rice. • TPB-extractable K would be a more reliable indicator than exchangeable K. • Phlogopite would be a good amendment for radiocesium-contaminated paddy fields

  17. On the genetic classification and tectonic implications of the Early Yanshanian granitoids in the Nanling Range, South China

    Institute of Scientific and Technical Information of China (English)

    LI XianHua; LI WuXian; LI Zheng-Xiang

    2007-01-01

    Early Yanshanian (Jurassic) granitoids are widespread in the Nanling Range of South China, and are associated with numerous non-ferrous and rare metal mineral deposits. These granitoids consist mainly of slightly peraluminous biotite monzogranites and K-feldspar granites that are closely associated in time and space with subordinate amphibole-bearing granites and muscovite- and garnet-bearing granites. In most previous studies, the biotite-bearing granites were classified as crustal transformation-type (corresponding to the S-type) granites which were interpreted to be derived from the regional Paleoproterozoic meta-sedimentary rocks. In this paper, we re-analyze the geochemical characteristics of a number of representative Early Yanshanian Nanling granitoids. There exists a clear negative correlation between SiO2 and P2O5 for the studied granitoids. The Early Yanshanian Nanling granitoid suites (including amphibole-bearing granodiorites→biotite monzogranites→K-feldspar granites→two-mica (muscovite) granites) are metaluminous to slightly peraluminous I-type or fractionated I-type granites. They were derived predominantly from Proterozoic igneous protoliths. The juvenile crust and/or newly mantle-derived materials might also have been involved in some of these granites. In addition, the I- and fractionated I-type granites are closely associated in time and space with minor amount of A-type felsic and mafic volcanic and intrusive rocks as well as alkaline rocks. All these rocks constitute a typical assemblage of anorogenic, intraplate magmatism, suggesting a dominant lithospheric extensional regime for the Nanling Range and neighboring region during the Early Yanshanian period.

  18. Contamination in mafic mineral-rich calc-alkaline granites: a geochemical and Sr-Nd isotope study of the Neoproterozoic Piedade Granite, SE Brazil

    Directory of Open Access Journals (Sweden)

    Leite Renato J.

    2006-01-01

    Full Text Available The Piedade Granite (~600 Ma was emplaced shortly after the main phase of granite magmatism in the Agudos Grandes batholith, Apiaí-Guaxupé Terrane, SE Brazil. Its main units are: mafic mineral-rich porphyritic granites forming the border (peraluminous muscovite-biotite granodiorite-monzogranite MBmg unit and core (metaluminous titanite-bearing biotite monzogranite BmgT unit and felsic pink inequigranular granite (Bmg unit between them. Bmg has high LaN/YbN (up to 100, Th/U (>10 and low Rb, Nb and Ta, and can be a crustal melt derived from deep-seated sources with residual garnet and biotite. The core BmgT unit derived from oxidized magmas with high Mg# (~45, Ba and Sr, fractionated REE patterns (LaN/YbN= 45, 87Sr/86Sr(t~ 0.710, epsilonNd(t ~ -12 to -14, interpreted as being high-K calc-alkaline magmas contaminated with metasedimentary rocks that had upper-crust signature (high U, Cs, Ta. The mafic-rich peraluminous granites show a more evolved isotope signature (87Sr/86Sr(t = 0.713-0.714; epsilonNd(t= -14 to -16, similar to Bmg, and Mg# and incompatible trace-element concentrations intermediate between Bmg and BmgT. A model is presented in whichMBmgis envisaged as the product of contamination between a mafic mineral-rich magma consanguineous with BmgT and pure crustal melts akin to Bmg.

  19. Rare metal granites and related rocks of the Ukrainian shield

    Directory of Open Access Journals (Sweden)

    Esipchuk, K.Ye.

    1993-12-01

    Full Text Available Two rare metal leucocratic granites, Perga and Kamennaya complexes, can be distinquished on the Ukrainian shield. The Perga complex consists of medium- and coarse grained, mainly porphyric, biotite, riebeckite and aegirine granites, granite porphyries, microclinites and albitites with rare metal mineralization (genthelvite, phenacite, tantalite, cassiterite and wolframite etc.. Granites from several stocks (up to 30 km2 in the northwestern part of the shield, situated along the fracture zone, restricted the large Korosten pluton of rapakivi granites to the northwest. The age of these granites (Pb-Pb and U-Pb methods on zircon and monazite practically coincide with the age of rapakivi granites being 1750 Ma. Within the Korosten complex of rapakivi granites we consider that zinnwaldite granites, which are characterized by fluorite and topazine mineralization, represent the final phase of pluton. These granites differ from the Perga ones by their low content of rare metals. The Kamennaya Mogila complex lies in the southeastern part of the Ukrainian shield. It consists of biotite and muscovite-biotite, medium- and coarse-grained (also porphyric, and occasionally greisining granites with rare metal mineralization (cassiterite, columbite, molybdenite, wolframite and beryl. Granites form several stocks (5-30 km2 situated 10-30 km to the west-northwest of the South-Kalchik gabbro-syenite-granite pluton. Granitoids in both of these complexes have similar isotopic ages (1800 Ma. Leucocratic subalkaline granites (the Novoyanisol type are known within the pluton itself, occupying an intermediate position between the above mentioned in terms of mineral and geochemical composition. The gabbro-syenite-granite formation of the Nearazov region has a substantial similarity to the anorthosite-rapakivi-granite formation. In this respect the relation of each of them to rare metal granites is rather remarkable. This relation is, most probably, not only spatial, but

  20. Occurrence of Tourmaline in Metasedimentary Rocks of the Isua Supracrustal Belt, Greenland: Implications for Ribose Stabilization in Hadean Marine Sediments.

    Science.gov (United States)

    Mishima, Shinpei; Ohtomo, Yoko; Kakegawa, Takeshi

    2016-06-01

    Abiotic formation of RNA was important for the emergence of terrestrial life, but the acknowledged difficulties of generating and stabilizing ribose have often raised questions regarding how the first RNA might have formed. Previous researchers have proposed that borate could have stabilized ribose; however, the availability of borate on the early Earth has been the subject of intense debate. In order to examine whether borate was available on the early Earth, this study examined metasedimentary rocks from the Isua Supracrustal Belt. Garnet, biotite, and quartz comprise the major constituents of the examined rocks. Field relationships and the chemical compositions of the examined rocks suggest sedimentary origin. The present study found that garnet crystals contain a number of inclusions of tourmaline (a type of borosilicate mineral). All tourmaline crystals are Fe-rich and categorized as schorl. Both garnet and tourmaline often contain graphite inclusions and this close association of tourmaline with garnet and graphite has not been recognized previously. Garnet-biotite and graphite geothermometers suggest that the tourmaline in garnet experienced peak metamorphic conditions (~500 °C and 5 kbar). The mineralogical characteristics of the tourmaline and the whole rock composition indicate that the tourmaline formed authigenically in the sediment during diagenesis and/or early metamorphism. Clay minerals in modern sediments have the capability to adsorb and concentrate borate, which could lead to boron enrichment during diagenesis, followed by tourmaline formation under metamorphic conditions. Clay minerals, deposited on the early Archean seafloor, were the precursors of the garnet and biotite in the examined samples. The studied tourmaline crystals were most likely formed in the same way as modern tourmaline in marine sediments. Therefore, boron enrichment by clays must have been possible even during the early Archean. Thus, similar enrichment could have been

  1. Structural, petrological and geochronological analysis of the lithotypes from the Pien region (Parana State, Brazil) and adjacences; Analise estrutural, petrologica e geocronologica dos litotipos da Regiao de Pien (PR) e adjacencias

    Energy Technology Data Exchange (ETDEWEB)

    Harara, Ossama Mohamed

    1996-12-31

    The Pien area presents the major geotectonic domains separated by the Pien Shear Zone (PSZ). The northern one is the Rio Pien Granite-Mylonitic Suite composed by calc-alkaline granitoids of Neoproterozoic age. The southern domain is represented by the Amphibolite-Granulite where high grade metamorphism took place at the end of paleoproterozoic time. Considering the identified lithotypes, their geochemical affinity (particularly the Ti, Cr, Ni and REE content) and the geological context observed in the area, a geotectonical model of active continental margin related to subduction SSZ (Supra-Subduction Zone) is proposed. K-Ar on plagioclase from gabbronorites gave Neoproterozoic ages although Sm-Nd whole rock isochron yielded Paleoproterozoic ages. Based in geochemical data, it is proposed that the biotite gneiss and biotite-amphibole-gneiss which occur near the PSZ have a shoshonitic to high-K calc-alkaline features which are characteristic of active continental margins. K-Ar on biotite extracted from these rocks, gave Neoproterozoic ages. The available radiometric data for the Rio Pien mylonitic granitoids show that between 650-595 Ma the generation, deformation and cooling below the isotherm of 250 deg C occurred. On the other hand, the geochronological data for the Agudos do Sul Massif are in the 590-570 Ma interval showing its younger generation. The Sr{sup 87} / Sr{sup 86} initial ratios for both granitoids suggest more involvement of the continental crust in the origins of Agudos do Sul granitic Massif. The analyses of the entire set of the available data for the Pien area allows the suggestion of a geotectonic scenery related to the evolution of an active continental margin during the collages associated to the Brasiliano Cycle 201 refs., 130 figs., 6 tabs., 2 maps

  2. Rb-Sr geochronologic investigation of precambrian samples from deep geothermal drill holes, Fenton Hill, New Mexico

    International Nuclear Information System (INIS)

    Analyses of twenty-six gneissic whole rocks from the depth range 732-2588 m in drill hole GT-2 yield a 1.62+-0.04 b.y. isochron age with initial 86Sr/86Sr(R0)=0.7067+-0.0014; this age is in agreement with radiometric ages reported for rocks elsewhere in north-central New Mexico. A preliminary isochron age of 1.92+-0.18 b.y. with R0=7014+-0.0025 from the nearby drill hole GT-1 is defined by eight samples. Because these samples are more representative of mineral systems or granite gneiss-amphibolite mixtures, the age is interpreted as being anomalously old. Samples of non-foliated biotite granodiorite from below 2588 m in GT-2 and from EE-2 yield an 1.50+-0.12 b.y. isochron (R0=0.7038+-0.0016). Hence the biotite granodiorite may either be a sill or an apophysis of a younger pluton. Dikes of fine-grained leucocratic and biotite monzogranites, which intrude the more coarse-grained 1.62-b.y. old gneisses are dated at 1.44+-0.03 b.y. (R0=0.7040+-0.0009). We thus recognize metamorphic activity at 1.62 b.y.; major magmatism at about 1.50 b.y.; and more local dike emplacement at 1.44 b.y. Present elevated in-situ temperatures have not disturbed the Rb-Sr systematics. (orig.)

  3. Conditions pression-température de la déformation dans les orthogneiss. Modèle thermodynamique et exemples naturels.

    OpenAIRE

    Le Goff, E.

    1989-01-01

    Les roches de composition granitique à granodioritique déformées constituent une part importante du matériel impliqué dans les zones de collision continentale. Cette thèse a pour objectif de développer des méthodes d'estimation des conditions P-T dans les orthogneiss. L'analyse des paragénèses dans les métagranites montre qu'elles sont contrôlées par: - la disparition de la biotite et du plagioclase (des basses pressions vers les hautes pressions); - l'apparition de l'oligoclase et la dispari...

  4. Sorption characteristics of Np on Fe(II) + Fe(III) oxides

    International Nuclear Information System (INIS)

    The sorption of neptunium on magnetite, hematite and biotite in 0.05, 0.1 and 0.2 M NaNO3 was investigated at 25degC for pH values between 1 and 8. The pH dependence of the sorption was different among three Np-iron-containing mineral systems. However, there were no or a little (biotite) dependence of sorption on ionic strength. After the sorption experiment, desorption experiments, with water of which pH was adjusted to corresponding values, 1 M KCl and 0.1 M potassium oxalate were also carried out to investigate the Np sorption form. The Np sorbed loosely can be desorbed by water and the Np sorbed as an exchangeable ion can be desorbed by KCl while the Np sorbed on non-crystalline part of iron-containing mineral by K2C2O4. The remaining Np amount, that could not be extracted by water, 1 M KCl and 0.1 M K2C2O4, is considered to be sorbed on the crystalline part of iron-containing minerals. It was found that for magnetite 50% of sorbed Np were sorbed by ion exchange and 25% were sorbed on the crystalline part, and that for biotite 35% of Np were sorbed by ion exchange and 30% were sorbed on the crystalline part. The sorption on crystalline part was a dominant mechanism together with ion exchange in magnetite and biotite systems. For hematite system, the sorption mechanism was different blow and above around pH 6. Ion exchange was dominant mechanism below pH 6 while the sorption on non-crystalline and crystalline parts were dominant mechanisms above pH 6. This phenomenon is considered because surface of hematite changed with increase of pH. Sorption kinetics of Np was also investigated. Sorption process consists of a rapid initial uptake followed by slow increase and sorption reaches nearly equilibrium in one hour. It was found that this rapid sorption was correlative loose sorption and ion exchange sorption in desorption experiment and this slow sorption was correlative sorption on non-crystalline and crystalline part in desorption experiment form quantitative

  5. Paleoproterozoic migmatitic gneisses from the Tandilia belt (Argentina), Río de la Plata craton, record cooling at deep crustal levels

    Science.gov (United States)

    Martínez, Juan Cruz; Massonne, Hans-Joachim; Dristas, Jorge Anastasio; Theye, Thomas; Graff, Ailín Ayelén

    2016-04-01

    We studied high-grade metamorphic rocks of the El Cristo hill area of the Tandilia belt. Mineral analyses and thermodynamic calculations were carried out for two adjacent rock samples: an amphibole-biotite gneiss and a garnet-biotite-bearing migmatite. Peritectic garnets in the migmatite show core compositions of pyr4.5(gro + andr)10spes6alm79.5 changing to pyr3.5(gro + andr)17spes6alm73.5 at their thin rims. Garnet compositions in the gneiss are pyr6.5(gro + andr)26spes12alm55.5 and pyr4.5(gro + andr)34spes12alm49.5 for core and rim, respectively. A P-T path was constructed by calculating pseudosections in the 11-component system Si-Ti-Al-Fe-Mn-Mg-Ca-Na-K-O-H and contouring them by isopleths for garnet components using the PERPLE_X software package. Supra-solidus crystallization of garnet cores in the migmatite began at 5.8 kbar and 660 °C. Garnet rims equilibrated at 7.0 kbar and 640 °C compatible with garnet cores in the amphibole-biotite gneiss (7.6 kbar and 660 °C). The further chemical development of garnet in this rock points to P-T conditions of 11.6 kbar and 620 °C and 12.2 kbar and 595 °C (outermost garnet rim). At this high-pressure stage Ca-amphibole was not stable. Most biotite formed during exhumation whereas the high-pressure accessory minerals, titanite and epidote, persisted. According to the obtained anti-clockwise P-T path the originally partly melted material was tectonically transported from ∼22 km (middle crust) to ∼40 km (lower crust) depths reaching a geothermal gradient as low as 15 °C km-1. This transport probably occurred along a major suture zone, which was active during the Paleoproterozoic (2.25-2.10 Ga), before a terminating collision of terranes near the SW boundary of the Rio de la Plata craton.

  6. A re-appraisal of the stratigraphy and volcanology of the Cerro Galán volcanic system, NW Argentina

    Science.gov (United States)

    Folkes, Christopher B.; Wright, Heather M.; Cas, Ray A.F.; de Silva, Shanaka L.; Lesti, Chiara; Viramonte, Jose G.

    2011-01-01

    From detailed fieldwork and biotite 40Ar/39Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60–4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km3 Lower Merihuaca Ignimbrite to a maximum of ~390 km3 (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km3 (DRE), approximately two thirds of the commonly quoted value.

  7. Trioctaedric granites talc from the Surovec region and Dlha dolina (gemerikum)

    International Nuclear Information System (INIS)

    Gemeric granitoids contain besides other minerals also talc, which are enriched in Li, which occurs in association with muscovite or biotite mostly siderophylit composition. These Li mica are either in the form of small Li enriched fengitic muscovite forming matrix with minor quartz and plagioclase, or create larger petals in the matrix. Larger petals have polylithionit composition (in older literature called Zinnwald). Li content was calculated indirectly using the first regression equation to estimate Li in talc. Talc was classified as a polylithionit and siderofylite, some of them also as annit. (authors)

  8. Petrogenetic Characteristics Of Oyaca Kedikayası Boyalık Adakites In SW Ankara (Central Anatolia, Turkey): Evidences For Slab Melt Metasomatism

    OpenAIRE

    Şen, Pınar; Şen, Erdal

    2013-01-01

    The Early Miocene Oyaca, Kedikayası and Boyalık dacites, situated approximately 50-60 km southwest of Ankara have affinities similar to adakitic rocks. They have porphyritic texture with a variable amount of plagioclase feldspar, hornblende and lesser biotite phenocrysts and a groundmass of plagioclase and quartz microcrysts. They have high Sr/Y (55-79 ppm) and (La/Yb)n (21-32 ppm) ratios, and low Y (10-19 ppm) and heavy rare earth element contents. According to their SiO2 (62.3-69.70 % wt.) ...

  9. PETROGENETIC CHARACTERISTICS OF OYACA – KEDİKAYASI – BOYALIK ADAKITES IN SW ANKARA (CENTRAL ANATOLIA, TURKEY): EVIDENCE FOR SLAB MELT METASOMATISM

    OpenAIRE

    Şen, Pınar; Şen, Erdal

    2013-01-01

    The Early Miocene Oyaca, Kedikayası and Boyalık dacites, situated approximately 50-60 km southwest of Ankara have affinities similar to adakitic rocks. They have porphyritic texture with a variable amount of plagioclase feldspar, hornblende and lesser biotite phenocrysts and a groundmass of plagioclase and quartz microcrysts. They have high Sr/Y (55-79 ppm) and (La/Yb)n (21-32 ppm) ratios, and low Y (10-19 ppm) and heavy rare earth element contents. According to their SiO2 (62.3-69.70 % wt.) ...

  10. K-Ar ages of the Jecheon granitic complex and related molybdenite deposits in South Korea

    International Nuclear Information System (INIS)

    K-Ar age determinations were carried out on the Jecheon mass and adjacent rocks occurring in the Ogcheon Zone of South Korea. Biotites separated from the Jecheon mass yield ages of 179, 169 and 159 Ma, confirming that the mass and the related molybdenum deposit were formed by the Daebo igneous activity. Muscovite from the Daehwa mine gives an age of 89 Ma and belongs to the Bulgugsa activity. Muscovite from pegmatite near the Dangdu mine, which intrudes into the Ogcheon Group, gives a Precambrian age of 1720 Ma. Thus the original rocks of the Ogcheon Group appear to have a middle Proterozoic age. (author)

  11. K-Ar ages of the Jecheon granitic complex and related molybdenite deposits in South Korea

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Ken; Uchiumi, Shigeru; Ishihara, Shunso (Geological Survey of Japan, Yatabe, Ibaraki (Japan)); Park, No-Young

    1983-07-01

    K-Ar age determinations were carried out on the Jecheon mass and adjacent rocks occurring in the Ogcheon Zone of South Korea. Biotites separated from the Jecheon mass yield ages of 179, 169 and 159 Ma, confirming that the mass and the related molybdenum deposit were formed by the Daebo igneous activity. Muscovite from the Daehwa mine gives an age of 89 Ma and belongs to the Bulgugsa activity. Muscovite from pegmatite near the Dangdu mine, which intrudes into the Ogcheon Group, gives a Precambrian age of 1720 Ma. Thus the original rocks of the Ogcheon Group appear to have a middle Proterozoic age.

  12. Sorption of cesium in intact rock

    Energy Technology Data Exchange (ETDEWEB)

    Puukko, E. [Univ. of Helsinki, Dept. of Chemistry (Finland)

    2014-04-15

    The mass distribution coefficient K{sub d} is used in performance assessment (PA) to describe sorption of a radionuclide on rock. The R{sub d} is determined using crushed rock which causes uncertainty in converting the R{sub d} values to K{sub d} values for intact rock. This work describes a method to determine the equilibrium of sorption on intact rock. The rock types of the planned Olkiluoto waste disposal site were T-series mica gneiss (T-MGN), T-series tonalite granodiorite granite gneiss (T-TGG), P-series tonalite granodiorite granite gneiss (P-TGG) and pegmatitic granite (PGR). These rocks contain different amount of biotite which is the main sorbing mineral. The sorption of cesium on intact rock slices was studied by applying an electrical field to speed up migration of cesium into the rock. Cesium is in the solution as a noncomplex cation Cs{sup +} and it is sorbed by ion exchange. The tracer used in the experiments was {sup 134}Cs. The experimental sorption on the intact rock is compared with values calculated using the in house cation exchange sorption model (HYRL model) in PHREEQC program. The observed sorption on T-MGN and T-TGG rocks was close to the calculated values. Two PGR samples were from a depth of 70 m and three samples were from a depth of 150 m. Cesium sorbed more than predicted on the two 70 m PGR samples. The sorption of Cs on the three 150 m PGR samples was small which was consistent with the calculations. The pegmatitic granite PGR has the smallest content of biotite of the four rock types. In the case of P-TGG rock the observed values of sorption were only half of the calculated values. Two kind of slices were cut from P-TGG drill core. The slices were against and to the direction of the foliation of the biotite rims. The sorption of cesium on P-TGG rock was same in both cases. The results indicated that there was no effect of the directions of the electric field and the foliation of biotite in the P-TGG rock. (orig.)

  13. Mantle derivation of Archean amphibole-bearing granitoid and associated mafic rocks: evidence from the southern Superior Province, Canada

    Science.gov (United States)

    Sutcliffe, Richard H.; Smith, Alan R.; Doherty, William; Barnett, Robert L.

    1990-08-01

    Amphibole-bearing, Late Archean (2.73 2.68 Ga) granitoids of the southern Superior Province are examined to constrain processes of crustal development. The investigated plutons, which range from tonalite and diorite to monzodiorite, monzonite, and syenite, share textural, mineralogical and geochemical attributes suggesting a common origin as juvenile magmas. Despite variation in modal mineralogy, the plutons are geochemically characterized by normative quartz, high Al2O3 (> 15 wt%), Na-rich fractionation trends (mol Na2O/K2O >2), low to moderate Rb (generallyenclaves and igneous layers and as intrusive units which exhibit textures indicative of contemporaneous mafic and felsic magmatism. Mafic mineral assemblages include: hornblende + biotite in tonalites; augite + biotite ± orthopyroxene ± pargasitic hornblende or hornblende+biotite in dioritic to monzodioritic rocks; and aegirine-augite ± silicic edenite ± biotite in syenite to alkali granite. Discrete plagioclase and microcline grains are present in most of the suites, however, some of the syenitic rocks are hypersolvus granitoids and contain only perthite. Mafic-ultramafic rocks have REE and Y contents indicative of their formation as amphibole-rich cumulates from the associated granitoids. Some cumulate rocks have skeletal amphibole with XMg(Mg/(Mg+ Fe2+)) indicative of crystallization from more primitive liquids than the host granitoids. Geochemical variation in the granitoid suites is compatible with fractionation of amphibole together with subordinate plagioclase and, in some cases, mixing of fractionated and primitive magmas. Mafic to ultramafic units with magnesium-rich cumulus phases and primitive granitoids (mol MgO/ (MgO+0.9 FeOTOTAL) from 0.60 to 0.70 and CT >150 ppm) are comagmatic with the evolved granitoids and indicate that the suites are mantle-derived. Isotopic studies of Archean monzodioritic rocks have shown LREE enrichment and initial 143Nd/144Nd ratios indicating derivation from mantle

  14. Geochemistry and petrogenesis of Mesoproterozoic A-type granitoids from the Danish island of Bornholm, southern Fennoscandia

    DEFF Research Database (Denmark)

    Johansson, Åke; Waight, Tod Earle; Andersen, Tom;

    2016-01-01

    ongoing deformation. The strong similarity in geochemical signatures indicate that they all belong to a single igneous suite composed of alkali-calcic biotite–hornblende quartz monzonites to more evolved biotite granites, albeit with an apparent gap in SiO2 content at around 70 wt%, dividing the suite...... trace element characteristics between the orthogneisses and the less deformed granitoids, suggesting similar origins for both rock types, and no systematic changes in isotopic composition with SiO2 concentration. Trace element compositions indicate a within-plate setting, similar to other 1.45 Ga...

  15. 湘南王仙岭花岗岩体的锆石U-Pb年代学、地球化学、锆石Hf同位素特征及其地质意义%Geochronology, geochemistry and zircon Hf isotopes of the Wangxianling granitic intrusion in South Hunan Province and its geological significance

    Institute of Scientific and Technical Information of China (English)

    郑佳浩; 郭春丽

    2012-01-01

    湘南王仙岭岩体由主体电气石黑云母花岗岩和侵入其内部的黑云母二长花岗岩组成,LA-MC-ICP MS锆石U-Pb 定年显示电气石黑云母花岗岩形成于印支期(235.0±1.3Ma),黑云母二长花岗岩形成于燕山期(155.9±1.0Ma),表明该岩体是两期岩浆活动的产物.这两期岩石均为高钾钙碱性系列,A/CNK值为1.07 ~1.66,属过铝-强过铝质花岗岩类.稀土元素显示LREE富集,HREE亏损,Eu负异常明显(0.01 ~0.38)的特征.早期电气石黑云母花岗岩和晚期黑云母二长花岗岩的εHf(t)值分别为-7.92~+4.61和-10.66~ -5.35;两阶段Hf模式年龄(tDM2)分别为1758 ~ 967Ma和1875 ~1538Ma.两期花岗岩均来自于古中元古代地壳物质重熔,其中早期电气石黑云母花岗岩在侵位上升过程中捕获了部分幔源老锆石,成岩过程中有少量地幔物质参与,且其源区具有高εHf(t)值的特点.综合前人研究成果,本文认为华南中生代印支期和燕山期均有钨锡矿化作用,印支期花岗质岩浆形成于碰撞挤压作用间隙伸展环境,而燕山期花岗质岩浆可能形成于大陆边缘弧后伸展环境.%The Wangxianling intrusion in South Hunan Province consists of two granitoids, the main tourmaline biotite granites and the biotite monzonite granites invading into the former. LA-MC-ICP MS zircon U-Pb dating shows that tourmaline biotite granites formed in Indosinian (235.0 ± 1.3Ma) while the biotite monzonite granites formed in Yanshanian (155.9 ± l.Oma), indicating that Wangxianling intrusion is the product of two-time magmatic activities. The compositions of these two period granites fall into the calc-alkaline category, with an A/CNK ratio of 1. 07 ~ 1. 66, which are peraluminous to strongly peraluminous granites. Their whole rock rare earth elements demonstrate total LREE enrichment and HREE deficit with significant negative Eu anomalies (0. 01 - 0. 38 ). The sm(t) values and two-staged Hf model ages of tourmaline

  16. Lithological model of the South China crust based on integrated geophysical data

    International Nuclear Information System (INIS)

    The structure and petrology of the earth's crust is critical to understand the growth and evolution of the continents. In this paper, we present the crustal lithological model along the 400-km-long seismic profile between Lianxian, near Hunan Province, and Gangkou Island, near Guangzhou City, South China. This model is based on an integrated geophysical data set including P-wave velocity (VP), S-wave velocity (VS), VP/VS ratio, mass density (ρ) and Lamé impedances (ρλ, ρµ), which are compared to those determined by laboratory measurements on a variety of crustal rock samples. The Bouguer gravity anomaly together with the seismic velocity enables us to constrain density. The heat flow and thermal field allow us to carry out corrections for temperature. Pressure correction is based on depth. We directly compare the property parameters determined from the South China seismic data with laboratory measurements made at the same conditions of pressure and temperature. Inversion of the available data for rock lithology indicates that there are substantial differences in the crustal lithology of the Yangtze and Cathaysia blocks. While the average lithology of the upper crust in both blocks is mainly characterized by granite–granodiorite and biotite gneiss, the granite–granodiorite layer is much thicker beneath the Cathaysia block. The middle crust in these two domains is not entirely similar, being granite–granodiorite and granite gneiss as the best fit for the Yangtze block, and granite gneiss and biotite gneiss for the Cathaysia block. The lower crust is composed of biotite gneiss, paragranulite and amphibolite for the Yangtze block, whereas biotite gneiss, paragranulite, diorite, mica quartz schist, amphibolite, green schist facies basalt and hornblende provide the best fit for the Cathaysia block. The results demonstrate that to the east of the Chenzhou–Linwu fault (CLF) that is the southern segment of the Jiangshan–Shaoxing fault, the lithology displays

  17. Microstructures and Petrology of Melt Inclusions in the Anatectic Sequence of Jubrique (Betic Cordillera, S Spain): Implications for Crustal Anatexis

    Science.gov (United States)

    Acosta-vigil, A.; Barich, A.; Garrido, C. J.; Cesare, B.; Tajčmanová, L.; Bartoli, O.

    2014-12-01

    We report a new occurrence of melt inclusions in polymetamorphic granulitic gneisses of the Jubrique unit, a complete though thinned crustal section located above the Ronda peridotite slab (Betic Cordillera, S Spain). The gneissic sequence is composed of mylonitic gneisses at the bottom and porphyroblastic gneisses on top. Mylonitic gneisses are strongly deformed rocks with abundant garnet and rare biotite. Except for the presence of melt inclusions, microstructures indicating the former presence of melt are rare or absent. Upwards in the sequence garnet decreases whereas biotite increases in proportion. Melt inclusions are present from cores to rims of garnets throughout the entire sequence. Most of the former melt inclusions are now totally crystallized and correspond to nanogranites, whereas some of them are partially made of glass or, more rarely, are totally glassy. They show negative crystal shapes and range in size from ≈5 to 200 micrometers, with a mean size of ≈30-40 micrometers. Daughter phases in nanogranites and partially crystallized melt inclusions include quartz, feldspars, biotite and muscovite; accidental minerals include kyanite, graphite, zircon, monazite, rutile and ilmenite; glass has a granitic composition. Melt inclusions are mostly similar throughout all the gneissic sequence. Some fluid inclusions, of possible primary origin, are spatially associated with melt inclusions, indicating that at some point during the suprasolidus history of these rocks granitic melt and fluid coexisted. Thermodynamic modeling and conventional thermobarometry of mylonitic gneisses provide peak conditions of ≈850 ºC and 12-14 kbar, corresponding to cores of large garnets with inclusions of kyanite and rutile. Post-peak conditions of ≈800-850 ºC and 5-6 kbar are represented by rim regions of large garnets with inclusions of sillimanite and ilmenite, cordierite-quartz-biotite coronas replacing garnet rims, and the matrix with oriented sillimanite. Previous

  18. Provenance of metasedimentary rocks of the Western Pernambuco-Alagoas Domain: Contribution to understand the crustal evolution of southern Borborema Province

    Science.gov (United States)

    Cruz, Rodrigo Fabiano da; Pimentel, Márcio Martins; Accioly, Ana Cláudia de Aguiar

    2014-12-01

    The Borborema Province is a complex neoproterozoic orogen in northeastern Brazil, made of a mosaic of fault-bounded terrains and several metassedimentary sequences. In the present work, new zircon U-Pb provenance data for metasedimentary rocks in the Western Pernambuco-Alagoas Domain, southern part of the Province, are reported. Detrital zircon ages range from Archean to Neoproterozoic. Three samples of the Cabrobó Complex were investigated: (i) sillimanite-kyanite-garnet-biotite schist, which presented mostly Ediacaran and Cryogenian detrital zircon ages (youngest zircon at ca. 554 Ma) indicating erosion of neoproterozoic sources, (ii) garnet-biotite schist, which has a dominant Tonian/Stenian population, a less abundant Cryogenian (youngest zircon age at ca. 643 Ma) as well as Paleoproterozoic and Archean zircon grains, and (iii) tourmaline-muscovite quartzite, which contains detrital zircon varying in age between ca. 2.08 Ga and 1.57 Ga, and an abundant population close to the Meso/Paleoproterozoic boundary, possibly associated with the erosion of rocks formed during the Statherian taphrogenesis, known in the central part of the São Francisco Craton as well as in other areas of the Borborema Province. Two samples of the Riacho Seco Metasedimentary Complex were also investigated: (i) a biotite schist with a dominant population presenting ages mostly between 2.3 and 2.7 Ga (youngest zircon age at ca. 2023 Ma) and (ii) a magnetite-biotite-muscovite quartzite, having detrital zircon grains with ages ranging between ca. 1.9 and 2.7 Ga. The sedimentary rocks of the Riacho Seco Complex may have their origin related to the erosion of sources within the São Francisco Craton. The data for the Riacho Seco metasedimentary rocks, however, are not conclusive with respect to the depositional age of the original sedimentary rocks. The sequence might represent exposure of an old (Paleoproterozoic) sedimentary pile or, alternatively, it comprises a neoproterozoic passive

  19. 华南某些不同时代花岗岩类岩石中铍地球化学特征的研究

    Institute of Scientific and Technical Information of China (English)

    刘振声

    1975-01-01

    Beryllium was determined from more than 40 granite bodies of different ages in southern China. Results show that it tends to increase with geologie age. The average beryllium contents for granites of various ages are (%): Hsuehfeng Period, 0.00016;Early Caledonian, 0.00034; Late Caledonian, 0.00035 ; Indosinian, 0.00055; Early Yenshanian, 0.00111; Late Yenshanian, 0.00032. The overall average content of beryllium of granite in this area is 0.00052%, 0.00047% and 0.00137% for biotite-granites and two-mica granites respectively. There seems to he a close relationship between Bemineralization and Yenshanian granites.

  20. Diffusion experiment of a radionuclide in granitic rock cores

    International Nuclear Information System (INIS)

    An effective diffusion coefficient of neptunium-237 which is one of hazardous long-lived radionuclide including high level radioactive waste was determined by using 40 mm diameter and 5 mm thick disks under an aerobic condition. An alpha autoradiography was performed for cross sections of a 20 mm thick granite disk to study the penetrated neptunium into granite. The effective diffusion coefficient of neptunium diffused through a water saturated granite was about 2.5 x 10-13 m2/sec. The autoradiograph of solid state track detectors clearly showed that biotite constituting granite has storage pores and keep diffusing species in it. (author)

  1. Zircon U-Pb geochronological framework of Qitianling granite batholith, middle part of Nanling Range, South China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Qitianling granite batholith (QGB) is located in the southern Hunan Province, middle part of the Nanling Range, South China. Its total exposure area is about 520 km2. Based on our 25 single grain zircon U-Pb age data and 7 published data as well as the geological, petrological, and space distribution characteristics, we conclude that QGB is an Early Yanshanian (Jurassic) multi-staged composite pluton. Its formation process can be subdivided into three major stages. The first stage, emplaced at 163―160 Ma with a peak at about 161 Ma, is mainly composed of hornblende-biotite monzonitic granites and locally biotite granites, and distributed in the eastern, northern, and western peripheral parts of the pluton. The second stage, emplaced at 157―153 Ma with a peak at 157―156 Ma, is mainly composed of biotite granites and locally containing hornblende, and distributed in the middle and southeastern parts of the pluton. The third stage, emplaced at 150―146 Ma with a peak at about 149 Ma, is mainly composed of fine-grained (locally porphyritic) biotite granites, and distributed in the middle-southern part of the pluton. Each stage can be further disintegrated into several granite bodies. The first two intrusive stages comprise the major phase of QGB, and the third intrusive stage comprises the additional phase. Many second stage fine-grained granite bosses and dykes intruded into the first stage host granites with clear chilling margin-baking phenomena at their intrusive contacts. They were emplaced in the open fracture space of the earlier stage consolidated rocks. Their isotopic ages are mostly 2―6 Ma younger than their hosts. Conceivably, the time interval from magma emplacement, through cooling, crystallization, solidification, up to fracturing of the earlier stage granites cannot exceed 2―6 Ma. During the Middle-Late Jurassic in the Qitianling area and neighboring Nanling Range, the coeval granitic and basic-intermediate magmatic activities were widely

  2. Partial melting of metavolcanics in amphibolite facies regional metamorphism

    Indian Academy of Sciences (India)

    Alan Bruce Thompson

    2001-12-01

    Metavolcanic rocks containing low-Ca amphiboles (gedrite, cummingtonite) and biotite can undergo substantial dehydration-melting. This is likely to be most prominent in Barrovian Facies Series (kyanite-sillimanite) and occurs at the same time as widespread metapelite dehydration- melting. In lower pressure facies series, metavolcanics will be represented by granulites rich in orthopyroxene when dehydration occurs at much lower temperatures than melting. In higher pressure facies series it is not well known whether metavolcanic rocks dehydrate or melt at temperatures lower or similar to that of metapelites.

  3. 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.

    2011-01-01

    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

  4. Mineral and whole-rock geochemistry of the Topuk Granitoid (Bursa, Western Anatolia, Turkey)

    Science.gov (United States)

    Orhan, Ayşe; Demirbilek, Mehmet; Mutlu, Halim

    2014-05-01

    The Eocene aged Topuk Granitoid exposing in the Tavşanlı Zone at south of the Izmir-Ankara Suture Zone is one of the granitoids which were formed as a result of collision of the Anatolide-Tauride block with the Sakarya continent in the late Cretaceous. Nearly east-west extending, elliptical shaped Topuk Granitoid was intruded into the Paleozoic and Mesozoic metamorphites and upper Cretaceous ophiolitic rocks. The intrusion is in granodiorite composition and contains spherical/ellipsoidal mafic microgranular enclaves (MME) with composition of monzodiorite to monzogabbro. The granitoid which contains xenoliths is frequently cut by porphyritic granodiorite, granite aplite and quartz dikes at the margins. Topuk Granitoid is represented by an I-type pluton with medium to high K calc-alkaline affinity and metaluminous melt composition. Ocean ridge granite (ORG) normalized element distributions show that the granitoid, dikes and MME's have similar patterns. A significant enrichment of LIL (Rb, Ba, K, Th and Sr) elements and relatively depletion of HFS (Ta, Nb, Ce, Hf, Y, Zr and Ti) elements are indicative of formation from hybrid magma in a subduction environment. In tectonic discrimination diagrams (Ta -Yb and Rb-Y+Nb), samples of the Topuk Granitoid are plotted into the volcanic arc granite (VAG) field which is characteristic for the post collision granites. The results of mineral chemistry show that plagioclases are in oligoclase-andesine (An20-49) composition, amphiboles are of magnesio-hornblende and biotites are of Fe-Mg-biotite composition. In the Al2O3-FeO-MgO diagram biotite minerals are accompanied by amphibole and other ferromagnesian minerals and represent biotites of calc-alkaline orogenic zones. Calculations based on the hornblende-barometer indicate that the calc-alkaline magma was crystallized under pressure of 2-6 kbars (mean=4 kbars) and at depth of 7-20 km (mean=12 km). The whole-rock and mineral chemistry data show that the Topuk Granitoid was formed

  5. Thermal history of peninsular India

    International Nuclear Information System (INIS)

    Fission track age date and the fission track annealing characteristic of the minerals - muscovite, biotite, apatite, garnet and zircon from various well-defined geological settings - are used with other radiometric ages to delineate the temperature history of the Indian Peninsula. The minerals studied are of pegmatitic as well as of granitic cogenetic origin mainly from Eastern Ghats, Satpura and Aravalli-Delhi belts. It is suggested that the Indian Ocean cycle may not be thermally independent but only a last phase of the main orogenic activity of the Eastern Ghats. (author). 32 refs., 4 figs

  6. Petrography of auriferous conglomerates in the Fortuna formation of the group Aguapei in Pau-A-Pique deposits in the Mato Grosso district, in the centre of Brazil

    International Nuclear Information System (INIS)

    Gold anomalies in the Pau a-Pique deposits are present in anastomossed shear zones near the contact between the Group Aguapei conglomerates and the Tonalito Alvorada. These high-strain zones are subparallel to the regional shearing NW - SE, and they have a brittle-ductile structures. The gold ore is exploted from veins and disseminations in the conglomerates that were affected by hydrothermal alteration. The main hydrothermal minerals in the mineralized layer are quartz, tourmaline, pyrite, biotite, chlorite and white mica. These hydrothermal minerals present textures that indicate their post-tectonic growth due the circulation of mineralizing fluids in the late shearing stages. (author)

  7. Metasedimentary, granitoid, and gabbroic rocks from central Stewart Island, New Zealand

    International Nuclear Information System (INIS)

    A NNE-NE trending strip, 3-8 km wide, extending from the Freshwater valley across Mt Rakeahua Table Hill, and Mt Allen to the northern end or the Tin Range was mapped at a scale of 1:12,500 to locate and investigate the boundary between the Median Tectonic Zone (MTZ) and Western Province on Stewart Island. A NNE-trending fault, herein termed the Escarpment Fault, separates predominantly ductily deformed rocks on its south side from essentially undeformed rocks to the north. North of the Escarpment Fault, a small (2-3 km2) pluton of alkali-feldspar granite (Freds Camp) intruded gabbroic rocks tentatively considered to be associated with gabbro/anorthosite/diorite of the Rakeahua pluton, centred on Mt Rakeahua. Both units were subsequently intruded by I-type biotite granite of the South West Arm pluton. South of the Escarpment Fault the oldest intrusions are biotite tonalite-granite orthogneisses (Ridge and Table Hill plutons) intercalated with the sillimanite-cordierite-bearing Pegasus Group metasedimentary rocks, considered to represent the Western Province. They contain titanite, allanite, and magmatic epidote-bearing assemblages, implying affinities with I-type granitoids. These older granitoids have been affected by at least three phases of ductile deformation. Immediately south of the Escarpment Fault, the Escarpment pluton (hornblende, biotite, quartz, monzonite-quartz monzodiorite) only exhibit effects of the third phase of deformation. Minor gabbroic intrusives concordant with the S3 fabric intrude the Pegasus Group and intercalated orthogneisses. Plutons of two-mica, garnet ±cordierite granite (Blaikies and Knob) and younger biotite-titanite-magmatic epidote granite (Campsite) cut fabrics associated with the third phase of ductile deformation. Preliminary U-Pb dating indicate Devonian-Carboniferous, Jurassic, and Early Cretaceous emplacement ages for Ridge Orthogneiss, Freds Camp pluton, South West Arm pluton, and Blaikies pluton, respectively. South West

  8. New 40Ar/39Ar age constraints on the Late Palaeozoic tectonic evolution of the western Tianshan (Xinjiang, northwestern China), with emphasis on Permian fluid ingress

    OpenAIRE

    De Jong, Koenraad; Wang, Bo; Faure, Michel; Shu, Liangshu S.; Cluzel, Dominique; Charvet, Jacques; Ruffet, Gilles; Yan CHEN

    2009-01-01

    Laser-probe dating of mylonite whole-rock samples from the North Tianshan—Main Tianshan fault zone that cross-cuts the North Tianshan domain's southern margin yielded 40Ar/39Ar spectra with 255–285 Ma ages. Biotite from an undeformed, Early Carboniferous granite, which cuts the steep mylonitic foliation in the Proterozoic basement of the Yili arcs's southern margin, gave a 263.4 ± 0.6 Ma plateau age (1σ). Pre-Carboniferous metasediments overlying this basement yielded plateau ages (1σ) of 253...

  9. Phenocrysts in obsidian glasses

    International Nuclear Information System (INIS)

    Minerals mainly of Carpathian obsidian glasses were mapped by nuclear microprobe based on the particle induced X-ray emission (PIXE) providing analytical data on them for the first time. Some samples from Armenia, Greece are also involved to make a comparison with the Carpathian specimens. The following minerals are identified and analyzed: pyrrhotite, chalcopyrite, pyrite, zircon, pyroxene, biotite, plagioclase feldspar, and anhydrite. On the basis of rock-forming silicate minerals, some petrologic processes are outlined. With the identification of accessory minerals (anhydrite, pyrrhotite, chalcopyrite, pyrite), some geological conclusions are also drawn. (author)

  10. Internal deterioration of concrete by the oxidation of pyrrhotitic aggregates

    International Nuclear Information System (INIS)

    This paper presents research results on the causes of a severe concrete deterioration, which occurred in many building foundations approximately 2 years after construction. Concrete samples were investigated with X-ray diffraction (XRD) analysis, a scanning electron microscope (SEM) and a petrographic examination performed with a stereomicroscope. It was found that the early cracking of concrete stemmed from the oxidation of the pyrrhotite found in the anorthosite aggregates used to produce the concrete. The oxidation process led to the precipitation of iron hydroxides having a higher volume than the original pyrrhotite does. The presence of micas (biotite) close to the pyrrhotite seemed to promote and accelerate the oxidation process

  11. Porphyry-Cu-Mo Stockwork Formation by Dynamic, Transient Hydrothermal Pulses: Mineralogic Insights From the Deposit at Butte, Montana

    Science.gov (United States)

    Mercer, C. N.; Reed, M. H.

    2011-12-01

    The temperature profile in magmatic-hydrothermal systems directly affects the chemical behavior and pressure regime of hydrothermal fluids and the resulting diversity of mineralization. We combine textural observations of igneous and hydrothermal minerals using SEM-CL and -BSE images with three independent mineral thermobarometers to better understand the thermal profile at the porphyry-Cu-Mo deposit in Butte, Montana. We apply the two most recent (and controversial) forms of the Ti-in-quartz thermobarometer from Thomas et al. (2010) and Huang and Audétat (2011), the Zr-in-rutile thermobarometer of Tomkins et al. (2007), and the XMg-Ti-in-biotite thermometer of Henry et al. (2005) to estimate the formation temperatures of these magmatic and hydrothermal minerals. In a comparison of isobaric temperature distributions from Ti-in-quartz (Thomas et al., 2010) and Zr-in-rutile we find that the Thomas et al. calibration consistently yields temperatures that are 50 to 200°C lower than those from Zr-in-rutile. These quartz temperatures are unreasonably low for quartz phenocrysts and are considerably lower than previous estimates for vein quartz. Temperature estimates from the Zr-in-rutile and XMg-Ti-in-biotite thermobarometers agree well with each other and with previous temperature estimates. We conclude that application of the Ti-in-quartz thermobarometer of Thomas et al. is not appropriate for this natural system. Quartz temperatures calculated using the calibration of Huang and Audétat (2011) are closer to those from rutile and biotite. Application of the Ti-in-quartz thermobarometer of Huang and Audétat to hydrothermal samples yields maximum temperature estimates, however, and requires evaluation of trace element abundances (e.g., Ti, Al) and other crystal lattice impurities (e.g., fluid inclusions) in growth zones as a means to determine whether growth zones represent slow or fast-growing quartz. Using thermobarometry from rutile, biotite, and quartz (Huang and

  12. Lithium anomaly near Pringle, southern Black Hills, South Dakota, possibly caused by unexposed rare-mineral pegmatite

    Science.gov (United States)

    Norton, James Jennings

    1984-01-01

    Six samples of biotite schist from a site near Pringle, South Dakota, contained from 140 to 750 parts per million lithium. These values are far greater than are found in mica schists in most of the rest of the southern Black Hills. The lithium may have emanated from concealed lithium pegmatite, and such pegmatite can be of interest as a possible source of rare minerals, especially tantalite and beryl. Whether making a full test of the anomaly will become economically judicious is much less clear.

  13. Pegmatite/wallrock interactions, Black Hills, South Dakota: Progressive boron metasomatism adjacent to the Tip Top pegmatite

    Science.gov (United States)

    Shearer, C.K.; Papike, J.J.; Simon, S.B.; Laul, J.C.; Christian, R.P.

    1984-01-01

    Interaction between country rock and fluids derived from the Tip Top pegmatite has resulted in a series of boron enriched assemblages. Between unaltered quartz-mica schist to the pegmatite contact is a succession of four mineral assemblages: 1. (1) Quartz-Biotite-Potassium Feldspar assemblage (Q-B-K), which consists essentially of the original metamorphic silicate assemblage plus anomalously high amounts of modal tourmaline 2. (2) Quartz-Biotite-Tourmaline assemblage (Q-B-T) 3. (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M) 4. (4) Tourmaline-Quartz assemblage (T-Q). Alkali elements (Cs, Rb, K, Li), SiO2, and Ba show a decrease from the Q-B-K assemblage to the T-Q assemblage. A12O3, Ga, B, total Fe and Zn increase moderately from the Q-B-K assemblage to the T-Q assemblage. The mineral chemistries also change considerably. The Mg/(Mg + Fe2+) ratios in biotites range from 0.54 to 0.50 in samples from the Q-B-K assemblage to 0.39 in the (Q-B-T) assemblage. The range in tourmaline end-member components from the Q-B-K assemblage to the T-Q assemblage is as follows: Q-B-K: Dravite.63 Schorl.23 Elbaite.05 Buergerite.09 T-Q: Dravite.23 Schorl.37 Elbaite.17 Buergerite.23. Observed variations in mineral assemblage and whole rock chemistry within the alteration zone appear to a first approximation to be a function of ??B2O3 (boron metasomatism) and ??K2O (alkali leaching). The breakdown of feldspar and biotite may be approximated by reactions: 2HCl + 2(K, Na)AlSi3O8 /ai 2(K, Na)Cl + Al2SiO5 + 5SiO2 + H2O and 2 Annite + SiO2 + 5Al2SiO5 + 2NaCl + 6H3BO3 /ai 2 Tourmaline + 2KCl + 7H2O. The alteration zone may represent either a single episode (B-, Cs-, Li-, Rb-enriched fluid) or multiple episodes (B, Zn, Mn fluid and Cs, Li, Rb fluid) of pegmatite fluid-schist interactions. In both situations, B in the aqueous fluid from the pegmatite reacts with the schist breaking down sheet silicate "traps" for Cs, Rb, Li, and K and forming tourmaline-rich assemblages. ?? 1984.

  14. Danfeng granitic pegmatite-type characteristics and uranium prospecting

    International Nuclear Information System (INIS)

    Caledonian Danfeng mixing of crust-mantle magma is rich in uranium, magma-hydrothermal fluid system transition including F.oxygen fugacity, in the background of the tensile differentiation of continental dynamics, the differentiation and crystallization formed the granitic pegmatite-type uranium. Conglomeration of such uranium-rich biotite, minerals and brown longer Mo, Zr, F elements. Strains of the southern rock of granite inside and outside the contact zone 300 m is range and the prospecting of distributing uranium ore. (authors)

  15. Mineralogical and geochemical investigation of micas from the Góry Sowie Mts pegmatites

    Directory of Open Access Journals (Sweden)

    Magdalena Dumańska - Słowik

    2004-01-01

    Full Text Available Micas from pegmatites of the Góry Sowie Mts were characterized using: microscopic observations,X-ray diffractometry, IR-spectroscopy and chemical analyses. The main stress of this study was puton concentration of main and trace elements in these minerals. Micas are very sensitive indicators ofpetrogenetic processes. A depletion in F, Rb, Cs, Li, Sn and REE as well as an enrichment in Ba show thehigh-temperature, post-magmatic crystallization of these minerals. The biotites are enriched in Cr what canconfirm metamorphic and metasomatic genesis of the pegmatites.

  16. Discussion on migration and precipitation mechanism of uranium in a granite-pegmatite type uranium deposit

    International Nuclear Information System (INIS)

    The authors focus on the physicochemical conditions of uranium mineralization in Guangshigou granite-pegmatite type uranium deposit and the mechanism of migration and precipitation of uranium in the pneumatolytic hydrothermal solution according to the theories and methods of thermodynamics. The studies show that U-bearing pneumato hydrothermal fluid is a reductive and acidic medium. Among it UF62- is a predominant form of uranium migration. In the mineralized period, the formation of biotite reduce the content of fluorine and make UF62- in the state of hydrolysis and form uraninite

  17. The genesis of LCT-type granitic pegmatites, as illustrated by lithium isotopes in micas

    OpenAIRE

    Deveaud, Sarah; Millot, Romain; Villaros, Arnaud

    2015-01-01

    Isotopic compositions in the Monts d’Ambazac Pegmatite Field (French Massif Central) exhibit a narrow range of mica δ7Li values, ranging from -3.6 to + 3.4‰. The value obtained in biotite from the host Saint Sylvestre granite falls within this range (δ7Li = -1.5‰). Lithium concentrations are consistent with the degree of magmatic evolution of each pegmatite type: from 630 ppm in Type II up to 13,500 ppm in the more evolved Type VI pegmatite. Although the rare-element contents e.g., Li, Cs, Ta...

  18. The life cycle of iron Fe(III) oxide: impact of fungi and bacteria

    Science.gov (United States)

    Bonneville, Steeve

    2014-05-01

    Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit vast surface areas which bind a large array of trace metals, nutrients and organic molecules hence controlling their mobility/reactivity in the subsurface. In this context, understanding the "life cycle" of iron oxide in soils is paramount to many biogeochemical processes. Soils environments are notorious for their extreme heterogeneity and variability of chemical, physical conditions and biological agents at play. Here, we present studies investigating the role of two biological agents driving iron oxide dynamics in soils, root-associated fungi (mycorrhiza) and bacteria. Mycorrhiza filaments (hypha) grow preferentially around, and on the surface of nutrient-rich minerals, making mineral-fungi contact zones, hot-spots of chemical alteration in soils. However, because of the microscopic nature of hyphae (only ~ 5 µm wide for up to 1 mm long) and their tendency to strongly adhere to mineral surface, in situ observations of this interfacial micro-environment are scarce. In a microcosm, ectomycorrhiza (Paxillus involutus) was grown symbiotically with a pine tree (Pinus sylvestris) in the presence of freshly-cleaved biotite under humid, yet undersaturated, conditions typical of soils. Using spatially-resolved ion milling technique (FIB), transmission electron microscopy and spectroscopy (TEM/STEM-EDS), synchrotron based X-ray microscopy (STXM), we were able to quantify the speciation of Fe at the biotite-hypha interface. The results shows that substantial oxidation of biotite structural-Fe(II) into Fe(III) subdomains occurs at the contact zone between mycorrhiza and biotite. Once formed, iron(III) oxides can reductively dissolve under suboxic conditions via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. We aimed here to understand the role of Fe(III) mineral

  19. Petrological studies of plutonic rocks of Ecuador

    International Nuclear Information System (INIS)

    The feldspars of many tonalitic plutonic rocks in the coastal regions and West Andean regions are zoned. This leads to the conclusion that they are relatively flat intrusions and to some extent transition rocks in the subvulcanite direction. This is in accordance with the genetic and chronological relationship between plutonites and the surrounding vulcanites of the Basic Igreous Complex (BIC). The composition of representative minerals, e.g. alkali feldspar, plagioclase feldspar, biotite, chlorite, and amphibole has been determined as well as the age of plutonite samples by the K/Ar dating method. (DG)

  20. Geology, petrology and geochronology of meridional and oriental regions of the Morungaba complex, SP

    International Nuclear Information System (INIS)

    This work studies the Morungaba Intensive Complex, in Southwestern of Sao Paulo State. Formed principally by granitoid rocks with biotite. 31 granitoid facies with structural was recognized. Petrographic own characteristics. The rocks from Morungaba Complex was joint in three magmatics groups, denominated: Roby Gray and Porphyritic. Petrographic and mineralogical composition studies of this three groups were done. Geochranological studies by Rb/Sr and K/sr methods made possible to establish the ages and evolution of this rocks. This Complex formation and evolution are associated with the dioritic rocks presence. This work also concluded that the Morungaba Intrusive Complex represent the pos-orogenic wents from Brazilian Cycle. (C.D.G.)

  1. Oxigen isotope compositions as indicators of epidote granite genesis in the Borborema Provinces, NE Brazil

    International Nuclear Information System (INIS)

    Neoproterozoic magmatic epidote-bearing granitoids intrude low-grade metapelites in the Cachoeirinha-Salgueiro terrane (CST), and gneisses and migmatites in the Serido terrane (ST), in the Borborema structural province, northeastern Brazil. Granitoids in both terranes contain biotite and hornblende, and are metaluminous, calc-alkalic, and oxidized I-type granites according to White's (1992) classification. However, in spite of these similarities, this work shows that mineral oxygen isotope data from plutons of the two terranes indicate different magma sources, and that magmatic epidote besides crystallizing at different pressure conditions, can have variable isotopic composition (au)

  2. Argon Isotopic and Experimental Petrologic Evidence for Phenocrysts Versus Xenocrysts in the Youngest Toba Tuff

    Science.gov (United States)

    Layer, P. W.; Gardner, J. E.; Rutherford, M. J.

    2001-12-01

    One of the largest known eruptions is that of the 74 ka Youngest Toba Tuff (YTT), which vented more than 2800 cubic km of magma from the Toba Caldera in Sumatra, Indonesia. The YTT was preceded by the 501 ka Middle Toba Tuff, and it has been proposed that the hiatus between them represents the time needed to develop a large magma body (Chesner, 1998). A controversial aspect of the YTT is that the aluminum content of the amphiboles in the magma indicates growth at pressures of ca. 300 MPa, whereas water contents in glass inclusions suggest much lower pressures, implying that the magma was greatly water undersaturated before eruption (Chesner, 1998). To develop a fuller understanding of the YTT magma's petrogenesis, we investigated the experimental phase equilibria of the magma and measured the argon isotopic signatures of sanidine, biotite, amphibole, and plagioclase. We find that biotite, plagioclase, and quartz are stable under almost all pressure-temperature conditions investigated, with sanidine crystallizing at low temperatures. Amphibole does not crystallize at temperatures and pressures recorded by the natural mineral assemblage and we can find no conditions under which amphibole is stable. Biotite and sanidine 40Ar/39Ar isochron ages are concordant at about 77 ka, similar to previous age determinations. Amphiboles and some plagioclases show significantly older ages, some as great as 1.5 Ma. Our results suggest that the YTT magma contained pheoncrysts of biotite, plagioclase, quartz, and sanidine, and resided at nearly water saturated pressures of 100 - 150 MPa. All amphiboles and some plagioclases were xenocrysts and were entrained throughout the entire 2800 cubic km of magma. Diffusion loss modeling of the xenocrysts indicates that these phases could not have resided in the magma chamber since the Middle Toba eruption, and that some were incorporated into the YTT magma perhaps only a few years prior to eruption. This study indicates that combining

  3. A desk study of surface diffusion and mass transport in clay

    International Nuclear Information System (INIS)

    Research into the properties of clays as barrier materials for nuclear waste disposal has led to the realization that they have important transport properties which are relatively insignificant in most other geological materials. Sorption has always been regarded as a purely retarding mechanism, but laboratory experiments over the past decade have indicated that surface diffusion of sorbed cations is a potentially significant transport mechanism in both compacted montmorillonite, and biotite gneiss. The present desk study about these issues was part of the CEC coordinated project Mirage-Second phase, research area Natural analogues

  4. Geochronological stages of magmatism of Sorsk copper-molybdenum-porphyry are district, Kuznetsk Alatau (K-Ar, Ar-Ar and Rb-Sr methods)

    International Nuclear Information System (INIS)

    Studies on biotite, amphibole and feldspar rocks were conducted through K-Ar, 39Ar-40Ar and Rb-Sr methods for evaluation of geochronological stages of magmatism development of the Sorsk copper-molybdenum-porphyry ore district. It is shown that general duration of magmatism development at the Sorsk district exceeds 100 mln years with intervals between individual magmatic pulses about 30 mln years. Dating by magmatites, related to ore-bearing porphyry complex and ore-metasotamic formations, is within the interval of 380-400 mln years. 13 refs.; 2 figs

  5. Early paleozoic magmatism manifestation of the South-Yenisei ridge

    International Nuclear Information System (INIS)

    To study the geological history of the magmatic complexes in the South-Yenisej ridge region one carried out the U-Pb-geochronological investigation of zircons from the granitoid rocks of the Posolnenskij and the Nizhnekanskij massive, as well as, the Ar-Ar isotopic analysis of the biotites contained in the mentioned rock samples. On the basis of the obtained coordinated U-Pb- and Ar-Ar-isotopic data one determined that formation of the mentioned granitoid rocks took place 510-455 million years ago

  6. Geology, petrography and geochronology of meridional and oriental regions from Morungaba complex, SP

    International Nuclear Information System (INIS)

    The Morungaba Granitoid Complex, covering about 330 km2, crops out as an elongate irregular Massif trending SW-NE, in the southeast part of the State of Sao Paulo, southeast Brazil. Major constituents are biotite granitoids with subordinate diorites. Over thirty facies types, each with distinctive structural-petrographic features, were recognized during detailed mapping of part of the Massif (about 200 km2), and mapped as groups of facies. Geochronological Rb/Sr data for several groups of associated facies are also presented. (author)

  7. Mineralogic investigation into occurrence of high uranium well waters in upstate South Carolina, USA

    Energy Technology Data Exchange (ETDEWEB)

    Warner, Richard, E-mail: wrichar@clemson.edu [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634-0919 (United States); Meadows, Jason; Sojda, Scott; Price, Van; Temples, Tom [Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC 29634-0919 (United States); Arai, Yuji [Department of Entomology, Soils, and Plant Sciences, Clemson University, Clemson, SC 29634-0315 (United States); Fleisher, Chris [Department of Geology, University of Georgia, Athens, GA 30602-2501 (United States); Crawford, Bruce; Stone, Peter [Bureau of Water, South Carolina Department of Health and Environmental Control, Columbia, SC 29201 (United States)

    2011-05-15

    Research Highlights: > Oxidative dissolution of uraninite in biotite granite is primary source of uranium in high-U well waters near Simpsonville, SC. > Uranium is chiefly transported as mixed uranyl hydroxyl-carbonate complexes. > Local reduction has resulted in secondary precipitation of uranium along fractures as coffinite. > Dissolution of uraninite and precipitation of coffinite were geologically recent. - Abstract: High levels of U (up to 5570 {mu}g/L) have been discovered in well waters near Simpsonville, South Carolina, USA. In order to characterize the mineralogical source of the U and possible structural controls on its presence, a deep (214 m) well was cored adjacent to one of the enriched wells. The highest gamma-ray emissions in the recovered core occur in coarse biotite granite at a depth just below 52 m. A slickenlined fault plane at 48.6 m and narrow pegmatite layers at depths of 113, 203 and 207 m also yield high gamma-ray counts. Thin sections were made from the above materials and along several subvertical healed fractures. Uraninite and coffinite are the principal U-rich minerals in the core. Other U-bearing minerals include thorite and thorogummite, monazite, zircon and allanite. Primary uraninite occurs in the biotite granite and in pegmatite layers. Secondary coffinite is present as tiny (<5 {mu}m) crystals dispersed along fractures in the granite and pegmatites. Coffinite also occurs along the slickenlined fault plane, where it is associated with calcite and calcic zeolite and also replaces allanite. Coffinite lacks radiogenic Pb, hence is considerably younger than the uraninite. Dissolution of partially oxidized Ca-rich uraninite occurring in the surficial biotite granite (or secondary coffinite in fracture zones) is likely the main source for the current high levels of U in nearby area wells. The high-U well waters have a carbonate signature, consistent with pervasive calcite vein mineralization in the core. Aqueous speciation calculations

  8. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20111705 An Junbo(Team 603,Bureau of Nonferrous Metals Geological Exploration of Jilin Province,Hunchun 133300,China);Xu Renjie Geological Features and Ore Genesis of Baishilazi Scheelite Deposit in Yanbian Area(Jilin Geology,ISSN1001-2427,CN22-1099/P,29(3),2010,p.39-43,2 illus.,2 tables,7 refs.)Key words:tungsten ores,Jilin ProvinceThe Baishilazi scheelite deposit is located in contacting zone between the marble of the Late Palaeozoic Qinglongcun Group and the Hercynian biotite granite.The vein and lenticular major ore body is obviously controlled by NE-extending faults and con

  9. Recrystallization of zircon and its effect on U-Pb dating

    International Nuclear Information System (INIS)

    Zircon is the most preferred mineral for U-Pb geochronology to obtain high precision mineral growth ages of crystalline rocks. In this work, a suite of discordant zircons from a leucosome of a garnet biotite gneiss from the Kerala Khondalite Belt, India were investigated by a combination of back-scattered electron imaging and SHRIMP analyses to ponder over the pattern of Pb-loss in recrystallized zircon. Previous attempts for U-Pb zircon dating of this rock type in the area have all resulted highly discordant ages

  10. The rapakivi granite plutons of Bodom and Obbnäs, southern Finland: petrography and geochemistry

    Directory of Open Access Journals (Sweden)

    Kosunen, P.

    1999-12-01

    Full Text Available The Obbnäs and Bodom granite plutons of southernmost Finland show the typical petrographic and geochemical features of the Proterozoic rapakivi granites in Finland and elsewhere: they cut sharply across the 1900 Ma Svecofennian metamorphic bedrock and have the geochemical characteristics of subalkaline A-type granites. The Bodom pluton is composed of porphyritic granites (hornblende-, hornblende-biotite-, and biotite-bearing varieties and an even-grained granite that probably represent two separate intrusive phases. This lithologic variation does not occur in the Obbnäs pluton, which is almost entirely composed of porphyritic hornblende-biotite granite that gradually becomes more mafic to the southwest. Three types of hybrid granitoids resulting from magma mingling and mixing occur on the southwestern tip of the Obbnäs peninsula. The Bodom granites are syenogranites, whereas the composition of the Obbnäs granite varies from syeno- to monzogranite. The main silicates of both the Bodom and Obbnäs granites are quartz, microcline, plagioclase (An1541, biotite (siderophyllite, and generally also amphibole (ferropargasite or hastingsite. Plagioclase-mantled alkali feldspar megacrysts are absent or rare. The accessory minerals are fluorite, allanite, zircon, apatite, and iron-titanium oxides; the Obbnäs granite also contains titanite. The Bodom and Obbnäs granites are metaluminous to weakly peraluminous, with average A/CNK of 1.00 and 1.05, respectively, have high Fe/Mg (average FeOtot/[FeOtot+MgO] is 0.94 for the Bodom and 0.87 for the Obbnäs granites, and high Ga/Al (3.78 to 5.22 in Bodom and 2.46 to 4.18 in Obbnäs. The REE contents are high with LREE-enriched chondrite-normalized patterns and moderate (Obbnäs to relatively strong (Bodom negative Eu-anomalies. The Obbnäs granite is enriched in CaO, TiO2, MgO, and FeO, and depleted in SiO2 and K2O compared to the Bodom granites. Also, there are differences in the Ba, Rb, and Sr contents of

  11. Geochemical and Sr-Nd Isotopic Characteristics of Post-Collisional Calc-Alkaline Volcanics in the Eastern Pontides (NE Turkey)

    OpenAIRE

    KAYGUSUZ, ABDULLAH; Arslan, Mehmet; ŞEN, WOLFGANG SIEBEL & CÜNEYT

    2011-01-01

    Major, trace element, K-Ar age and Sr-Nd isotopic data are presented for the Eocene Torul volcanics in the eastern Pontide orogenic belt (NE Turkey). The studied rocks are composed of basaltic andesitic, andesitic, trachyandesitic, and minor trachydacitic lavas associated with their pyroclastics. These rocks contain plagioclase (An2-44), hornblende (Mg#= 0.78-0.98), clinopyroxene (Wo43-46 En41-43 Fs10-15), biotite, quartz, and minor sanidine phenocrysts. K-Ar ages on hornblendes ages range fr...

  12. Petrogenesis of the Kösedağ Pluton, Suşehri-NE Sivas, East-Central Pontides, Turkey

    OpenAIRE

    BOZTUĞ, DURMUŞ

    2008-01-01

    The Kösedağ syenite crops out as a shallow-seated pluton within the Eocene volcano-sedimentary rocks and is unconformably overlain by Lower Miocene limestones in the Suşehri-NE Sivas region, east-central Pontides. It consists of syenites and quartz syenites with a phaneritic, porphyritic texture characterized by K-feldspar megacrysts set in a coarse- to medium-grained groundmass comprising K-feldspar, plagioclase, clinopyroxene, amphibole, biotite and quartz. Major element geochemistry data r...

  13. Research on the metallogenetic material source by means of mathematical statistics and spidergram. A case study of No.6722 uranium deposit in southern Jiangxi

    International Nuclear Information System (INIS)

    By means of Q-type fuzzy cluster analysis and spidergram on trace elements and REE data, the source of metallogenetic material for No. 6722 uranium deposit in South Jiangxi province is discussed in this paper. It has been discrminated that the ore-bearing cryptoexplosive breccia and the alted granite have a close genetical relationship with the biotite granite but not with the two-mica granite. It is concluded that mathematical statical analysis is able to obtain finer geochemical information with significant geo- logical implications which are hidden in the spidergram. Thus more strict and objective conclusions with scientific reappearance may be drawn after using this method. (authors)

  14. Petrogenesis of the Seleteguole granitoids from Jinhe county in Xinjiang (West China): Implications for the tectonic transformation of Northwest Tianshan

    Science.gov (United States)

    Zhang, Wei; Leng, Cheng-Biao; Zhang, Xing-Chun; Su, Wen-Chao; Tang, Hong-Feng; Yan, Jia-Hui; Cao, Jing-Liang

    2016-07-01

    The Seleteguole Cu-Mo deposit in Jinghe County, Xinjiang is tectonically located on the northern margin of the Northwestern Tianshan. Three major intrusions including biotite granite, diorite porphyry and quartz diorite porphyry have been identified. The biotite granite, with a zircon U-Pb age of 307 ± 3 Ma, intruded carbonates and clastic rocks of the Middle Carboniferous Dongtujin Formation. The younger diorite porphyry and quartz diorite porphyry, with an identical zircon U-Pb age of 302 ± 3 Ma, locally intruded the biotite granite; where the granite in contact with the two porphyries were characterized by phyllic alteration. The mineralogical and geochemical characteristics indicate that all granitoids in Seleteguole belong to calc-alkaline I-type. These granitoids are enriched in LILE relative to HFSE with negative anomalies of Nb, P and Ti, typical of arc-related rocks. All three granitoids have positive zircon εHf(t) values, low Mg# ratios (34-39), and low Cr (parental magmas could be derived from juvenile lower crust that has probably originated from cooling of mantle-derived magmas as a result of the subduction of Paleo-Junggar Ocean beneath the Yili Block. Subducted sediments were involved in the source of the granitoids in Seleteguole. Compared to biotite granite, diorite porphyry and quartz diorite porphyry have higher Th/La ratios but lower zircon εHf(t) values, indicating that more subducted sediments contributed in the latter two. The regional geological and geochemical characteristics of the Late Carboniferous igneous rocks in the Northwestern Tianshan show that Late Carboniferous I-type granitoids, with juvenile Sr-Nd-(Hf) isotopic signatures, formed in a continent-marginal arc setting as a result of the subduction of Paleo-Junggar Ocean beneath the Yili Block. In combination with the compositions of the Early Permian granitoids in the region, we suggest that the tectonic setting of the Northwestern Tianshan transformed from a continental arc

  15. Iron deposition as acidic groundwater encounters carbonates in the alluvium of Pinal Creek, Arizona, U.S.A.

    Science.gov (United States)

    Lind, Carol J.; Oscarson, R.L.

    1997-01-01

    In a column experiment, acidic groundwater from Pinal Creek Arizona, a Cu mining area, was eluted through a composited alluvial sample obtained from a core that had been removed from a well downgradient of the acidic groundwater. The minerals present in typical grains and flakes in the alluvium before and after the elution were determined by X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive multichannel analyses (EDX). The concentrations of Fe, Ti, Mn, Si, Al, Na, Ca, K, Mg and S in these grains and flakes and in their microcrystalline surface coatings were measured by EDX. In addition to magnetite, hematite, and Fe-Ti oxides, Fe was most concentrated in micas (especially biotite-like flakes) and in the microcrystalline coatings. The measured elements in these microcrystalline coatings were primarily K, Fe, Al, and Si. The microcrystalline coatings on the mica flakes also contained Mg. The approximate 1:3 Mg:Si atomic ratios (ARs) of the biotite-like flakes both before and after the elution would suggest that the Fe deposited during the elution had not substituted for Mg in these flakes. As a result of the elution, assuming no loss of Si, the averaged recorded Fe:Si AR of the microcrystalline coatings increased from (0,46 to 0.58):3.00. Iron deposition on the typical grains and flakes may relate to the presence of Fe in the particle on which it is deposited or to the presence of Fe in the microcrystalline surface coatings before elution. The data here are not sufficient for a statistical evaluation, but elution caused the following trends: (1) The Fe:Si A R increased in the (K,Fe,Al,Si)-microcrystalline surface coatings; (2) For the mica flakes, there was more than a 2-fold increase in the Fe:Si AR for the microcrystalline surface coatings of the Fe-rich biotite-like flakes but no measurable increase of the Fe:Si AR for the microcrystalline surface coatings of the muscovite-like flakes that contained 3-5 times less Fe; (3) Also for the

  16. SHRIMP zircon U-Pb geochronology of early Mesozoic felsic igneous rocks from the southern Lancangjiang and its tectonic implications

    Institute of Scientific and Technical Information of China (English)

    PENG Touping; WANG Yuejun; FAN Weiming; LIU Dunyi; SHI Yuruo; MIAO Laicheng

    2006-01-01

    The SHRIMP zircon U-Pb geochronology of three typical samples, including two monzonitic granites from the Lincang batholith and a rhyolite from the Manghuai Formation are presented in the southern Lancangjiang, western Yunnan Province. The analyses of zircons for the biotite monzonitic granites from the northern (02DX-137) and southern (20JH-10) Lincang batholith show the single and tight clusters on the concordia, and yield the weighted mean 206pb/238U ages of 229.4 ± 3.0 Ma and 230.4 ± 3.6 Ma, respectively, representing the crystallized ages of these granites. The zircons for the rhyolitic sample (02DX-95) from the Manghuai Formation give a weighted mean 206Pb/238U age of 231.0 ± 5.0 Ma. These data suggest that the igneous rocks from the Lincang granitic batholith and Manghuai Formation have a similar crystallized age. In combination with other data, it is inferred that both were generated at a narrow age span (~230 Ma) and were originated from the postcollisional tectonic regime. An early Proterozoic 206Pb/238U apparent age of 1977±44 Ma is additionally obtained from one zircon from the biotite monzonitic granite (southern Lincang batholith), indicative of development of the early Proterozoic Yangtze basement in the region. These precisely geochronological data provide important constraints on better understanding the Paleozoic tectonic evolution of the Tethys, western Yunnan Province.

  17. Sand and clay mineralogy of sal forest soils of the Doon Siwalik Himalayas

    Indian Academy of Sciences (India)

    Mukesh; R K Manhas; A K Tripathi; A K Raina; M K Gupta; S K Kamboj

    2011-02-01

    The peteromineralogical characterization of the soil was carried out for the 12 soil profiles exposed in the Shorea robusta dominated forests of the Siwalik forest division, Dehradun. The quartz was observed as the dominating light mineral fraction (64–80%) in all the profiles studied. Biotite, hornblende, zircon, tourmaline, rutile and opaques comprising of iron minerals constituted the heavy mineral fraction (20%). The mineralogy of both the sand and clay fractions revealed a mixed mineralogy. The clay minerals in the order of their dominance were vermiculite, illite, kaolinite and mixed layer minerals. The presence of vermiculite and illite in appreciable quantities indicates that these were synthesized from the K-rich soil solution, as orthoclase and micas were present in significant quantities in the sand minerals. The mineral suites identified in the study shows that the geological, climatological and topographical factors of the region collectively played a dominant role in their formation and transformation. After critical appraisal of the results, it may be deduced that the mineralogical composition, physicochemical properties and total elemental analysis of the soils do not show any deficiency of the bases and other plant nutrients in general. The inherent fertility of the soil is good as indicated by the sand and clay mineralogy of the soil and the biotite and feldspar together with the mica is an important source of nutrients for the vegetation in the soils of the Doon valley.

  18. Occurrence of disseminated uraninite in Wheeler Basin, Grand County, Colorado

    International Nuclear Information System (INIS)

    Disseminated uraninite occurs in Wheeler Basin, Grand County, Colo., about 5 mi (8 km) southeast of Monarch Lake, in Precambrian metamorphic rocks consisting of migmatized gneiss and mixed gneiss and pegmatite. An intrusion of Precambrian Y Silver Plume Granite lies within 400 ft (122 m) of the occurrence. The disseminated uraninite is confined to parts of the host rock that are rich in biotite; highest grade found was 0.73 percent uranium. The disseminated uraninite occurs as cubes and grains, generally from 0.1 to 0.3 mm across. Unit cell edge of the uraninite, approximately 5.48 A, suggests its pegmatitic origin. The origin of the uraninite disseminations is attributed by us to remobilization and concentration of elements during metamorphism caused by the intrusion of Silver Plume Granite. Uranium and lead isotopic analyses by K. R. Ludwig of uraninite and monazite from biotite concentrations confirm an apparent age of 1,450 +- 20 m.y. for these minerals. This age is equivalent to that reported for the Silver Plume Granite. Although the Wheeler Basin occurrence is small in size, it has many similarities to the Roessing uranium deposit in South-West Africa

  19. Occurrence of disseminated uraninite in Wheeler Basin, Grand County, Colorado

    International Nuclear Information System (INIS)

    Disseminated uraninite occurs in Wheeler Basin. Grand County, Colo., about 5 mi (8 km) southeast of Monarch Lake, in Precambrian metamorphic rocks consisting of migmatized gneiss and pegmatite. An intrusion of Precambrian Y Silver Plume Granite lies within 400 ft (122 m) of the occurrence. The disseminated uraninite is confined to parts of the host rock that are rich in biotite; highest grade found was 0.73 percent uranium. The disseminated uraninite occurs as cubes and grains, generally from 0.1 to 0.3 mm across. Unit cell edge of the uraninite, approx. =5.48 A, suggests its pegmatitic origin. The origin of the uraninite disseminations is attributed by us to remobilization and concentration of elements during metamorphism caused by the intrusion of Silver Plume Granite. Uranium and lead isotopic analyses by K. R. Ludwig of uraninite and monazite from biotite concentrations confirm an apparent age of 1,450 +- 20 m.y. for these minerals. This age is equivalent to that reported for the Silver Plume Granite. Although the Wheeler Basin occurrence is small in size, it has many similarities to the Rossing uranium deposite in South-West Africa

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

    Science.gov (United States)

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

    2016-04-01

    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.

  1. Mechanisms of hydrothermal alteration in a granitic rock. Consequences for high-level radioactive waste disposal

    International Nuclear Information System (INIS)

    The study of hydrothermal alteration in the Auriat granitic rock (France, Massif-Central) has evidenced three main events: - a pervasive chloritisation of biotites in some parts of the drill-core, - an alteration localized around subvertical cracks and superimposed on previously chloritized or unaltered granite, - an alteration localized around subhorizontal cracks cross-cutting the preceding ones. The second type of alteration, produced by a geothermal system, gives the most interesting results to be applied to the nuclear radwaste disposal problem. Among primary minerals of granite, only biotite (or chlorite) and oligoclase are intensively altered. Therefore, the chemical composition of these minerals induces the nature of secondary parageneses. These, associated to the subvertical cracks network, indicate a thermal gradient of 150 C/Km. The geochemical code has allowed to corroborate that the thermal gradient was responsible for the occurrence of different parageneses with depth. Moreover, it was shown that the variable mineralogy around cracks was due to a thermal profile established at equilibrium between the rock and the fluid. Therefore, the extent of the alteration was proportional to the thermal power of the fluid. A dissolution and next a precipitation phase of new minerals characterize hydrothermal alteration, which is due to the thermal power emitted by radioactive waste and linked with the evolution of temperature during time. This alteration provokes two favourable events to storage: decrease of rock porosity and increase of sorption capacity

  2. Pyroxene zonation trends in mafic nepheline syenite and ijolite, Diamond Jo quarry, Magnet Cove igneous alkalic complex, Arkansas

    Energy Technology Data Exchange (ETDEWEB)

    Flohr, M.J.K.; Ross, M.

    1985-01-01

    Compositions of pyroxenes from mafic nepheline syenite and ijolite from Magnet Cove (NS and IJ) define zoning trends that reflect changing conditions in the crystallizing magmas and are used to contrast Magnet Cove with other alkalic complexes. The Na-Mg-Fe/sup 2 +/+Mn plot is used to compare NS and IJ pyroxenes with pyroxenes from nepheline syenites from S. Qoroq Centre, Greenland, and the Coldwell Complex intrusions, Ontario. Trends from the three areas are similar, but differences exists. Zoning in individual NS grains is greater than ranges for individual intrusions from S. Qoroq. Also, NS pyroxenes with compositions more magnesisan than Mg/sub 50/Nag are more Al-rich than S. Qoroq and Coldwell pyroxenes, indicating crystallization from a more undersaturated magma. These NS pyroxenes also contain 2-3 times more Ti and Fe/sup 3 +/. Despite different concentrations of Al, Ti, and Fe/sup 3 +/, the general crystallization trends shown by all elements considered are similar in NS and S. Qoroq pyroxenes. Sparse biotite and the absence of amphibole in NS indicate an H/sub 2/O-poor parent magma compared with those of the Coldwell and S. Qoroq nepheline syenites, which contain these phases. Mg-rich biotites and pyroxenes in IJ indicate that it formed from a less evolved liquid than NS.

  3. 3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    Science.gov (United States)

    Kampmann, Tobias C.; Stephens, Michael B.; Weihed, Pär

    2016-06-01

    Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the south-western part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D1 and D2) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D1 and D2, and even after D2. F2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone- to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

  4. Cesium sorption and desorption behavior of clay minerals

    International Nuclear Information System (INIS)

    Cesium sorption and desorption of clay minerals (montmorillonite, beidellite, nontronite, weathered biotite, rectorite and illite) were investigated by consecutive sorption-desorption (CSD) experiments. In batch sorption experiment, two solutions with different Cs concentration 10-3 and 10-7 mol/L) were used. In batch desorption experiments, Cs sorbed samples in sorption experiments were treated 5 times with 1 mol/L ammonium acetate solution. In the case of CSD experiments using 10-3 mol/L Cs solution, the exchangeable cations (Na, Ca, and K) in the clay samples affected to the sorption ratio of Cs, and this effect depended on the type of clay mineral. The desorption ratios of untreated, Na-exchanged and Ca-exchanged weathered biotite ranged from 23 to 33%, while that of other samples was over 80%. In the case of CSD experiments using 10-7 mol/L Cs solution, the sorption ratio of montmorillonite was smaller than that of the other clay samples. In desorption experiments, more than 10-9 mol sorbed Cs remained in 1.0 g of the sample after 5 extraction times. These results indicate that all examined clay samples are able to strongly adsorb Cs with a capacity of more than 10-9 mol/g. (author)

  5. A model that helps explain Sr-isotope disequilibrium between feldspar phenocrysts and melt in large-volume silicic magma systems

    Science.gov (United States)

    Duffield, Wendell A.; Ruiz, Joaquin

    1998-12-01

    Feldspar phenocrysts of silicic volcanic rocks are commonly in Sr-isotopic disequilibrium with groundmass. In some cases the feldspar is more radiogenic, and in others it is less radiogenic. Several explanations have been published previously, but none of these is able to accommodate both senses of disequilibrium. We present a model by which either more- or less-radiogenic feldspar (or even both within a single eruptive unit) can originate. The model requires a magma body open to interaction with biotite- and feldspar-bearing wall rock. Magma is incrementally contaminated as wall rock melts incongruently. Biotite preferentially melts first, followed by feldspar. Such melting behavior, which is supported by both field and experimental studies, first contaminates magma with a relatively radiogenic addition, followed by a less-radiogenic addition. Feldspar phenocrysts lag behind melt (groundmass of volcanic rock) in incorporating the influx of contaminant, thus resulting in Sr-isotopic disequilibrium between the crystals and melt. The sense of disequilibrium recorded in a volcanic rock depends on when eruption quenches the contamination process. This model is testable by isotopic fingerprinting of individual feldspar crystals. For a given set of geologic boundary conditions, specific core-to-rim Sr-isotopic profiles are expectable. Moreover, phenocrysts that nucleate at different times during the contamination process should record different and predictable parts of the history. Initial results of Sr-isotopic fingerprinting of sanidine phenocrysts from the Taylor Creek Rhyolite are consistent with the model. More tests of the model are desirable.

  6. The petrogenesis of sodic island arc magmas at Savo volcano, Solomon Islands

    Science.gov (United States)

    Smith, D. J.; Petterson, M. G.; Saunders, A. D.; Millar, I. L.; Jenkin, G. R. T.; Toba, T.; Naden, J.; Cook, J. M.

    2009-12-01

    Savo, Solomon Islands, is a historically active volcano dominated by sodic, alkaline lavas, and pyroclastic rocks with up to 7.5 wt% Na2O, and high Sr, arc-like trace element chemistry. The suite is dominated by mugearites (plagioclase-clinopyroxene-magnetite ± amphibole ± olivine) and trachytes (plagioclase-amphibole-magnetite ± biotite). The presence of hydrous minerals (amphibole, biotite) indicates relatively wet magmas. In such melts, plagioclase is relatively unstable relative to iron oxides and ferromagnesian silicates; it is the latter minerals (particularly hornblende) that dominate cumulate nodules at Savo and drive the chemical differentiation of the suite, with a limited role for plagioclase. This is potentially occurring in a crustal “hot zone”, with major chemical differentiation occurring at depth. Batches of magma ascend periodically, where they are subject to decompression, water saturation and further cooling, resulting in closed-system crystallisation of plagioclase, and ultimately the production of sodic, crystal and feldspar-rich, high-Sr rocks. The sodic and hydrous nature of the parental magmas is interpreted to be the result of partial melting of metasomatised mantle, but radiogenic isotope data (Pb, Sr, Nd) cannot uniquely identify the source of the metasomatic agent.

  7. Isotopic age determinations in Bergslagen, Sweden. 2

    International Nuclear Information System (INIS)

    This paper reports the isotopic dating of a Filipstad-type granite with rapakivi facies, exposed around the village of Rockesholm, about 20 km S of Grythyttan. Ten samples were taken from the river bed at Rockesholm dam site and two from nearby exposures. The Rb and Sr concentrations and Rb/Sr ratios of the whole-rocks were determined by X-ray fluorescence spectrometry. All samples were measured as pressed-powder pellets; the mass-absorption corrections for both sample and external standard are based upon the Compton scattering of the Mo-Kα primary beam. The biotite was analysed for Rb and Sr by mass-spectrometric isotope dilution. Sr isotopic compositions were determined directly on unspiked Sr for whole-rocks and calculated from the isotope dilution runs for the biotite. From the Rb-Sr whole-rock data it is concluded that the Filipstad-type granite at Rockesholm has been emplaced about 1700 Ma ago. (Auth.)

  8. Isotopic age determinations in Bergslagen, Sweden. 2. The Filipstad-type granite of Rockesholm, Grythyttan area

    Energy Technology Data Exchange (ETDEWEB)

    Oen, I.S. (Amsterdam Univ. (Netherlands). Geologisch Inst.)

    1982-09-01

    This paper reports the isotopic dating of a Filipstad-type granite with rapakivi facies, exposed around the village of Rockesholm, about 20 km S of Grythyttan. Ten samples were taken from the river bed at Rockesholm dam site and two from nearby exposures. The Rb and Sr concentrations and Rb/Sr ratios of the whole-rocks were determined by X-ray fluorescence spectrometry. All samples were measured as pressed-powder pellets; the mass-absorption corrections for both sample and external standard are based upon the Compton scattering of the Mo-K..cap alpha.. primary beam. The biotite was analysed for Rb and Sr by mass-spectrometric isotope dilution. Sr isotopic compositions were determined directly on unspiked Sr for whole-rocks and calculated from the isotope dilution runs for the biotite. From the Rb-Sr whole-rock data it is concluded that the Filipstad-type granite at Rockesholm was emplaced about 1700 Ma ago.

  9. Geochronological evidence of Indosinian(high-pressure) metamorphic event and its tectonic significance in Taxkorgan area of the Western Kunlun Mountains,NW China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The CL images,LA-ICP-MS in situ trace elements analysis,and U-Pb dating for zircons indicate that the metamorphic ages of the sillimanite-garnet-biotite gneiss and the garnet-amphibole gneiss from eastern Taxkorgan of the Western Kunlun Mountains are 220±2 and 220±3 Ma respectively,and their protolith ages are younger than 253±2 and 480±8 Ma respectively.Two samples were collected at the same outcrops with HP mafic granulite and HP pelitic granulite.Mineral assemblage of the sillimanite-garnet-biotite gneiss(Grt+Sill+Per+Q) is consistent with that of HP pelitic granulite at early high amphibolite-granulite facies stage.Mineral assemblage of the garnet-amphibole gneiss(Grt+Amp+Pl+Q) is consistent with retro-metamorphic assemblage of HP mafic granulite at amphibolite facies stage.The dating results suggest that these HP granulites underwent peak metamorphism at 220±2 to 253±2 Ma.Thus,the Kangxiwar tectonic zone was probably formed by subduction and collision of the Paleo-Tethys Ocean during Indosinian.Protolith ages of the two samples,together with previously published U-Pb zircon dating age,suggest that the sillimanite-garnet schist-quartzite unit is a late Paleozoic unit,not a part of the Paleoproterozoic Bulunkuole Group.

  10. Oxygen isotope geochemistry of the Omeo Metamorphic complex, Victor: implications for metamorphic fluid flow, mineralisation and anatexis

    Energy Technology Data Exchange (ETDEWEB)

    Cartwright, I.; Harper, S. [Monash University, Clayton, VIC (Australia). Victorian Institute of Earth and Planetary Sciences

    1998-12-01

    Metamorphosed turbidites from the Omeo Metamorphic Complex show only minor changes in {delta}{sup 18}O values with increasing metamorphic grade from 13.4 {+-} 1.7 per mill in the chlorite and biotite zones to 12.3 {+-} 1.0 per mill in the sillimanite + K-feldspar zone. Rocks within 5 km of the S-type granite at Hume Dam have {delta}{sup 18}O values of 6.8-8.1 per mill that probably reflect interaction with heated meteoric-igneous fluids. Interaction with igneous fluids has also occurred close to other I- and S-type granites in this region. However, pervasive metamorphic fluid-rock interaction in this terrain did not occur, which limits the region`s potential for hydrothermal mineralisation. Anatexis at high grades was probably via dehydration-melting reactions that consumed muscovite and biotite, which is consistent with there being little fluid present during metamorphism. Small (kilometre scale or less) S-type granites in the sillimanite + K-feldspar zone have {delta}{sup 18}O values similar to those of the surrounding metasediments and probably formed by melting of those rocks. By contrast, larger (tens of kilometres scale) Ca-rich. peraluminous, S-type granites have lower {delta}{sup 18}O values than the surrounding metasediments, and may represent melts of underlying middle to lower crust . Copyright (1998) Blackwell Science Asia 31 refs., 1 tab., 3 figs.

  11. Long-lived high-temperature granulite-facies metamorphism in the Eastern Himalayan orogen, south Tibet

    Science.gov (United States)

    Zhang, Zeming; Xiang, Hua; Dong, Xin; Ding, Huixia; He, Zhenyu

    2015-01-01

    The Namche Barwa Complex exposed in the Eastern Himalayan Syntaxis, south Tibet, underwent high-pressure (HP) and high-temperature (HT) granulite-facies metamorphism and associated anatexis. The HP pelitic granulites contain garnet, kyanite, sillimanite, cordierite, biotite, quartz, plagioclase, K-feldspar, spinel, ilmenite and graphite. These minerals show composite reaction texture and varying chemical compositions and form four successive mineral assemblages. Phase equilibrium modeling constrains the P-T conditions of 10-12 kbar and 550-700 °C for the prograde stage, 13-16 kbar and 840-880 °C for the peak-metamorphic stage, and 5-6 kbar and 830-870 °C for the late retrograde stage, indicating that the HP granulites recorded a clockwise P-T path involving the early heating burial and anatexis through dehydration melting of both muscovite and biotite, and the late isothermal decompression and gradual melt crystallization under HT granulite-facies conditions. The zircon U-Pb dating reveals that the HT granulite-facies metamorphism probably initiated at ca. 40 Ma, and lasted to ca. 8 Ma. Therefore, the present study provides robust evidence for a long-lived HT metamorphism and associated anatexis in the deeply buried Indian continent and important constraints on the leucogranite generation and tectonic evolution of the Himalayan orogen.

  12. Petrographical and geochemical characterization and deformation conditions of the San Cristobal pluton, Sierra de Velasco, La Rioja, Argentina; Caracterizacion petrografica y geoquimica y condiciones de deformacion del pluton San Cristobal, Sierra de Velasco, La Rioja, Argentina

    Energy Technology Data Exchange (ETDEWEB)

    Bellos, L.I.; Toselli, A.J.; Rossi, J.N.; Grosse, P.; Rosa, J.D. de la; Castro, A.

    2010-07-01

    The San Cristobal pluton is a 35 km2 granitic body that outcrops at the southestern tip of the Sierra de Velasco, located west of La Rioja city, Argentina. It is formed by monzogranites and syenogranites, together with scarce granodiorites, with medium to fine-grained, equigranular to slightly porphyritic textures. Their mineral assemblage consists of quartz + microcline + plagioclase + biotite {+-} muscovite + zircon + apatite + magnetite. The granite contains dioritic to tonalitic mafic enclaves. The central and eastern parts of the granite have been deformed by the NNW-SSE trending South Mylonitic shear zone formed by mylonitic rocks. The metamorphic host-rock is represented by scarce greenschist facies xenoliths and hornfels with the high T/P assemblage K-feldspar - cordierite - biotite {+-} sillimanite. The granites are calc-alkaline, weak- to moderately peraluminous, and formed as part of a continental magmatic arc developed along the active margin of western Gondwana during the Early Paleozoic. The depth of emplacement of the San Cristobal pluton is estimated at {approx}12 km. (Author).

  13. Incineration of ion-exchange resins in fluidized bed. Part of a coordinated programme on treatment of spent ion exchange resins

    International Nuclear Information System (INIS)

    Incineration of ion-exchange resins in a fluidized bed was studied on the pilot plant scale. The test programme performed consisted of the testing of various bed materials and finding the optimal conditions of incineration of spent resins. Granular resins were incinerated in an ethanol-water mixture. Incinernation converts the organic resin into inert oxide material, which can be solidified for instance with cement. The weight of the ash was 1...20% and the volume 2...30% of the original resins, which contained 15...25% moisture. When solidified with cement the volume of the ash-concrete is 4...22% of the concrete of equal compressive strength acquired by direct solidification. Water immersion and heat tests of solidified ash showed satisfactory results. The absorption of Cs and Co in various bed materials was studied by means of inactive tracer materials. Biotite and chamotte absorbed significantly, but this absorption does not drastically help on the off gas side. The sintering of the bed materials in the presence of sodium was studied. Corundum, chamotte and biotite have a safety limit of 5% sodium of the bed's weight at 8500C

  14. Insights into the P–T evolution path of TsoMorari eclogites of the north-western Himalayas: Constraints on the geodynamic evolution of the region

    Indian Academy of Sciences (India)

    Preeti Singh; Ashima Saikia; Naresh Chandra Pant; Pramod Kumar Verma

    2013-06-01

    The present study is on the Ultra High Pressure Metamorphic rocks of the Tso Morari Crystalline Complex of the northwestern Himalayas. Five different mineral associations representative of five stages of P–T (pressure–temperature) evolution of these rocks have been established based on metamorphic textures and mineral chemistry. The pre-UHP metamorphic association 1 of Na-Ca-amphibole + epidote ± paragonite ± rutile ± magnetite with T–P of ∼500° C and 10 kbar. This is followed by UHP metamorphic regime marked by association 2 and association 3. Association 2 (Fe< Mg< Ca-garnet + omphacite + coesite + phengite + rutile ± ilmenite) marks the peak metamorphic conditions of atleast 33 kbar and ∼750° C. Association 3 (Fe< Mg< Ca-garnet + Na-Ca amphibole + phengite ± paragonite ± calcite ± ilmenite ± titanite) yields a P–T condition of ∼28 kbar and 700°C. The post-UHP metamorphic regime is defined by associations 4 and 5. Association 4 (Fe< Ca< Mg-garnet + Ca-amphibole + plagioclase (An05) + biotite + epidote ± phengite yields a P–T estimate of ∼14 kbar and 800°C) and association 5 (Chlorite + plagioclase (An0.5) + quartz + phengite + Ca- amphibole ± epidote ± biotite ± rutile ± titanite ± ilmenite) yields a P–T value of ∼7 kbar and 350°C.

  15. Garnet-sillimanite bearing gneisses from Darjeeling, eastern Himalaya: Textural relationship and P–T conditions

    Indian Academy of Sciences (India)

    Divya Prakash; Suparna Tewari

    2015-08-01

    The area around Darjeeling consists of medium grade metamorphic rocks and provides a classic example of inverted Himalayan metamorphism. The area under investigation shows upper amphibolite facies metamorphism (sillimanite-muscovite subfacies), rocks are intimately associated with the migmatites and granites. The presence of quartzite, calc-silicate rocks, graphitic schist and abundance of aluminous minerals like kyanite or sillimanite in these rocks indicate their metasedimentary character. Granetsillimanite bearing gneisses occupy most of the area of Darjeeling but not persistent throughout. Textural relationship suggests sequential growth of progressively higher-grade metamorphic minerals during D1 and D2 deformation. The relative XMg in the minerals varies in the order: biotite>staurolite>garnet, and the XMn decreases in the order: garnet>staurolite>biotite. The P–T evolution of these garnetsillimanite gneiss has been constrained through the use of conventional geothermobarometry, internally consistent TWEEQU programme and Perple_X software in the KFMASH model system, the combination of these three approaches demonstrates that the Darjeeling gneisses experienced peak pressure and temperature at 7.0 ± 0.3 kbar and 700 ± 30°C. The observation in this study has important bearing on the inverted metamorphism in the Himalayan metamorphic belt.

  16. Preliminary study on features of mineralogical zoning of epigenetic alteration at sandstone-type uranium deposit, Dongsheng area, Ordos basin

    International Nuclear Information System (INIS)

    Sandstone-type uranium deposits located in Dongsheng area, northern Ordos basin, occur in Zhiluo Formation, Middle Jurassic. The Zhiluo Formation is divided into two members. The lower member is further divided into two submembers. The lower submember is dominantly composed of grey sandstone being the ore-hosting horizon; the upper submember consists of grey-green sandstone and mudstone. The upper member of Zhiluo Formation is made of mottled medium-fine grained sandstone and mudstone. Through the microscopic observation and study on sandstones of Zhiluo Formation, authors have established a vertical zonation of epigenetic alteration (from the top to the bottom): the limonitization + clayization + carbonation in the mottled fine-grained sandstone of the upper member of Zhiluo Formation; the green alteration (II) (mainly the chloritization of biotite, as well as the chloritization and epidotization of feldspar) + clayization + carbonation in the grey-green sandstone of the upper submember of the lower member of Zhiluo Formation; and the green alteration (I) (mainly the epidotization of feldspar) + carbonation in grey, grey-white sandstone of the lower submember. The epigenetic alteration basically occurs in grey-green sandstone. The sandstone shows grey-green color because it contains much green biotite (not chlorite). The epigenetic alteration in sandstone layer is closely associated with the uranium ore-formation

  17. Proterozoic geology east and southeast of Commonwealth Bay, George V Land, Antarctica, and its relationship to that of adjacent Gondwana terranes

    International Nuclear Information System (INIS)

    Rock samples from coastal outcrops of Commonwealth Bay, and inland nunataks southeast of it, include metapelites (garnet-cordierite-biotite-sillimanite-K-feldspar -(plagioclase) -(orthopyroxene)), felsic gneiss (intermediate plagioclase, quartz, biotite, K feldspar, hypersthene, garnet), and mafic dikes (calcic plagioclase-hypersthene-clinopyroxene-(hornblende)-(garnet)). A range of metamorphic conditions from early T=c. 800 degrees C and P=6-7 kbar to retrograde T=500 degrees C and P=5 kbar is manifested by hornblende and garnet after orthopyroxene and clinopyroxene in the mafic rocks and zoned garnet, plus garnet after hypersthene, in the felsics and metapelites. From SHRIMP U-Pb analyses or zircons from metapelite and felsic gneisses, initial metamorphic crystallisation is thought to have taken place at c. 2500 Ma and retrograde metamorphism at c. 1710 Ma. The age of protoliths to the mafics is unknown. The above outlined combination of ages and metamorphic conditions is restricted in the Adelie Land-George V Land coastline to what is regarded as a north-south fault-bounded sliver. This sliver can be matched to some extent with metamorphic mineralogies and chemistries in similar lithologies within similar north-south-bounded segments at the southern end of Eyre Peninsula. (author). 25 refs., 5 figs., 2 tabs

  18. The role of phosphorus, magnesium and potassium availability in soil fungal exploration of mineral nutrient sources in Norway spruce forests.

    Science.gov (United States)

    Rosenstock, Nicholas P; Berner, Christoffer; Smits, Mark M; Krám, Pavel; Wallander, Håkan

    2016-07-01

    We investigated fungal growth and community composition in buried meshbags, amended with apatite, biotite or hornblende, in Norway spruce (Picea abies) forests of varying nutrient status. Norway spruce needles and soil collected from forests overlying serpentinite had low levels of potassium and phosphorus, those from granite had low levels of magnesium, whereas those from amphibolite had comparably high levels of these nutrients. We assayed the fungal colonization of meshbags by measuring ergosterol content and fungal community with 454 sequencing of the internal transcribed spacer region. In addition, we measured fine root density. Fungal biomass was increased by apatite amendment across all plots and particularly on the K- and P-deficient serpentinite plots, whereas hornblende and biotite had no effect on fungal biomass on any plots. Fungal community (total fungal and ectomycorrhizal) composition was affected strongly by sampling location and soil depth, whereas mineral amendments had no effect on community composition. Fine root biomass was significantly correlated with fungal biomass. Ectomycorrhizal communities may respond to increased host-tree phosphorus demand by increased colonization of phosphorus-containing minerals, but this does not appear to translate to a shift in ectomycorrhizal community composition. This growth response to nutrient demand does not appear to exist for potassium or magnesium limitation. PMID:26996085

  19. Formation of tectonic peperites from alkaline magmas intruded into wet sediments in the Beiya area, western Yunnan, China

    Science.gov (United States)

    Xu, X.-W.; Cai, X.-P.; Zhong, J.-Y.; Song, B.-C.; Peters, S.G.

    2007-01-01

    Tertiary (3.78 Ma to 3.65 Ma) biotite-K-feldspar porphyritic bodies intrude Tertiary, poorly consolidated lacustrine sedimentary rocks in the Beiya mineral district in southwestern China. The intrusives are characterized by a microcrystalline and vitreous-cryptocrystalline groundmass, by replacement of some tabular K-feldspar phenocrysts with microcrystalline chlorite and calcite, and by Fe-rich rings surrounding biotite phenocrysts. Peculiar structures, such as contemporary contact faults and slickensides, ductile shear zones and flow folds, foliation and lineations, tension fractures, and banded and boudin peperites, are developed along the contact zones of the intrusives. These features are related to the forceful intrusion of the alkaline magmas into the wet Tertiary sediments. The partially consolidated magmas were deformed and flattened by continued forceful magma intrusion that produced boudinaged and banded peperites. These peperites characterized by containing oriented deformation fabrics are classified as tectonic peperites as a new type of peperite, and formation of these tectonic peperites was related to fracturing of magmas caused by forceful intrusion and shear deformation and to contemporary migration and injection of fluidized sediments along fractures that dismembered the porphyritic magma. Emplacement of the magma into the wet sediments in the Beiya area is interpreted to be related to a large pressure difference rather than to the buoyancy force. ?? 2007 Elsevier Ltd. All rights reserved.

  20. Mineral Type and Solution Chemistry Affect the Structure and Composition of Actively Growing Bacterial Communities as Revealed by Bromodeoxyuridine Immunocapture and 16S rRNA Pyrosequencing.

    Science.gov (United States)

    Kelly, L C; Colin, Y; Turpault, M-P; Uroz, S

    2016-08-01

    Understanding how minerals affect bacterial communities and their in situ activities in relation to environmental conditions are central issues in soil microbial ecology, as minerals represent essential reservoirs of inorganic nutrients for the biosphere. To determine the impact of mineral type and solution chemistry on soil bacterial communities, we compared the diversity, composition, and functional abilities of a soil bacterial community incubated in presence/absence of different mineral types (apatite, biotite, obsidian). Microcosms were prepared containing different liquid culture media devoid of particular essential nutrients, the nutrients provided only in the introduced minerals and therefore only available to the microbial community through mineral dissolution by biotic and/or abiotic processes. By combining functional screening of bacterial isolates and community analysis by bromodeoxyuridine DNA immunocapture and 16S rRNA gene pyrosequencing, we demonstrated that bacterial communities were mainly impacted by the solution chemistry at the taxonomic level and by the mineral type at the functional level. Metabolically active bacterial communities varied with solution chemistry and mineral type. Burkholderia were significantly enriched in the obsidian treatment compared to the biotite treatment and were the most effective isolates at solubilizing phosphorous or mobilizing iron, in all the treatments. A detailed analysis revealed that the 16S rRNA gene sequences of the OTUs or isolated strains assigned as Burkholderia in our study showed high homology with effective mineral-weathering bacteria previously recovered from the same experimental site. PMID:27138048

  1. Possibility of tracing the geothermal history by Moessbauer study on heat treated micas

    International Nuclear Information System (INIS)

    Various samples of biotite and phlogopite were heated ranging from room temperature to 1000 deg C, in atmosphere for 4 to 6 hours. The Moessbauer spectra of such heated samples were taken at room temperature in transmission geometry. As expected, Fe2+ goes to Fe3+ as the samples are heated. It is easy to separate out the Fe2+ and Fe3+ intensities by studying the variation in the absorption spectra with the angle of γ. Since efg principal axis for Fe2+ and Fe3+ are opposite to each other, the intensity ratios of the quadrupole doublets are the inverse of each other for them. Using this constraint, the spectra of heat treated micas have been analyzed to obtain the ratios Fe2+/Fe3+ for each site at various temperatures. It was found that: (1) the Fe2+ goes to Fe3+ rather sharply, essentially only samples heated to above 700 deg C or so exhibiting the transition, (2) in natural phlogopite, even prior to heat treatment Fe3+ is dominant, it was found that the spectra of heat treated biotites resemble those of phlogopite. This may have a bearing on the geothermal history of these micas. Results of Fe2+/Fe3+ as well as IS, OS and widths of lines for various heat treated specimens are reported and their possible implications are discussed. (author)

  2. 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

  3. Sorption processes of radiocesium in soil and bedrock

    Energy Technology Data Exchange (ETDEWEB)

    Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

    2015-06-01

    Three recent studies on cesium sorption in soil and bedrock are reviewed. {sup 137}Cs, originating from fallouts of nuclear weapons tests and the Chernobyl accident was found to decrease in an exponential manner in forest soil, and the highest fraction in soil profiles was found in the organic layer. Also, the mineral layer below the organic layer contained a large fraction of cesium inventory but at depths below 20 cm only a very small fraction was observed. In the bedrock of Olkiluoto, where the final repository for spent nuclear fuel from the Finnish nuclear power plants will be constructed, mica mineral biotite plays the most important role in cesium sorption. The selectivity of biotite decreases in the order Cs > K > Na > Ca and the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange reactions, respectively. Ion exchange isotherms for Cs/Na and Cs/K exchange were modelled by assuming three different ion exchange sites: frayed edge sites (FES), basal plane sites and intermediate sites. The selectivity coefficients derived for these sites were successfully used to predict cesium sorption in a mica gneiss rock. Sorption of cesium in mineral soil layers from the Olkiluoto overburden were studied using three different approaches: model batch experiments, an in-situ method and calculations. All three approaches gave the same trend but the distribution coefficient values varied in range of one order of magnitude.

  4. 湘赣地洼型煤田中岩浆岩的岩石学及地球化学特征

    Institute of Scientific and Technical Information of China (English)

    童玉明; 邱明

    1982-01-01

    Commonly seen in Mesozoic coal fields of Diwa type in Hunan and Jiangxi are basic, intermediate and acidic intrusive and volcanic rocks. The sequence of magmatism is from acidic to basic. The rocks show a tendency to become younger in age from west to east. Biotite granite porphyry-quartz diorite porphyrite, diorite porphyrite-diabase, diabase-porphyrite and spilite are the main rock types. These rocks are geochemically eharacterized by an evolutionary sequence from acidic to basic and by the enrichment in alkaline elements (except for biotite granite porphyry which has undergone intense alteration). In the acidic rocks K2O> Na2O whereas in the basic rocks K2O < Na2O. All the rocks are rich in non-ferrous metals and rare dements. The majority of the magmatic rocks were emplaced during the most intensive pariod of Diwa development. The rocks generally run parallel with the strike of coal basins. They were emplaced mostly along the layers or cut across coal seams. The above data on tectono-magmatic activity in coal fields of Diwa type lend great support to Prof. Chert Guoda's proposal that the history of crustal evolution is divided into three major stages -- geosyncline, platform snd Diwa.

  5. A chlorite mineral surface actively drives the deposition of DNA molecules in stretched conformations

    International Nuclear Information System (INIS)

    Muscovite mica is commonly used to immobilize DNA molecules onto a flat surface. This method, however, requires either the use of divalent cations in the buffer solution or the chemical modification of the surface. Here we show that DNA molecules have different binding affinities and assume different conformations when adsorbed to different layered minerals. In particular, the effect of biotite, muscovite, talc, brucite and chlorite upon DNA binding is investigated. Using atomic force microscopy it is possible to quantify the amount of DNA deposited onto a flat surface and it is experimentally confirmed that biotite, talc and brucite have a much higher affinity than muscovite (7-, 20- and 25-fold more volume of DNA deposited, respectively). The deposition of DNA onto chlorite presents areas (brucite-like) with high DNA coverage and areas (mica-like) where DNA molecules are absent. We regularly observed isolated DNA molecules that became stretched across these regions of low affinity. The stretching is not induced by the deposition procedure but is driven by the surface potential gradient between brucite-like and mica-like regions in chlorite. The active stretching of DNA on chlorite is a clear indication of the technological potential carried by these materials when used as substrates for biomolecules

  6. Sorption processes of radiocesium in soil and bedrock

    International Nuclear Information System (INIS)

    Three recent studies on cesium sorption in soil and bedrock are reviewed. 137Cs, originating from fallouts of nuclear weapons tests and the Chernobyl accident was found to decrease in an exponential manner in forest soil, and the highest fraction in soil profiles was found in the organic layer. Also, the mineral layer below the organic layer contained a large fraction of cesium inventory but at depths below 20 cm only a very small fraction was observed. In the bedrock of Olkiluoto, where the final repository for spent nuclear fuel from the Finnish nuclear power plants will be constructed, mica mineral biotite plays the most important role in cesium sorption. The selectivity of biotite decreases in the order Cs > K > Na > Ca and the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange reactions, respectively. Ion exchange isotherms for Cs/Na and Cs/K exchange were modelled by assuming three different ion exchange sites: frayed edge sites (FES), basal plane sites and intermediate sites. The selectivity coefficients derived for these sites were successfully used to predict cesium sorption in a mica gneiss rock. Sorption of cesium in mineral soil layers from the Olkiluoto overburden were studied using three different approaches: model batch experiments, an in-situ method and calculations. All three approaches gave the same trend but the distribution coefficient values varied in range of one order of magnitude.

  7. Preliminary paragenetic interpretation of the Quaternary topaz rhyolite lava domes of the Blackfoot volcanic field, southeastern Idaho

    Science.gov (United States)

    Lochridge, W. K., Jr.; McCurry, M. O.; Goldsby, R.

    2015-12-01

    The Quaternary topaz rhyolite lava domes of the bimodal, basalt-dominated Blackfoot volcanic field (BVF), SE Idaho occur in three clusters. We refer to these as the China Hat lava dome field (southernmost; ~ 57 ka), and the 1.4 to 1.5 Ma Sheep Island and White Mountain (northernmost) lava dome fields. The rhyolites and surrounding, more voluminous basalt lavas closely resemble coeval Quaternary rocks erupted to the north along the Eastern Snake River Plain segment of the Yellowstone-Snake River Plain volcanic track. However rhyolites in BVF are distinguished by having more evolved Sr- and Nd-isotopic ratios, as well as having phenocryst assemblages that includes hydrous phases (biotite and hornblende), thorite, and vapor-phase topaz. This study seeks to improve our understanding of the unique conditions of magma evolution that led to these differences. We focus on textural features of major and accessory phenocrysts as a basis for inferring paragenesis for rhyolites from the China Hat lava dome field. Preliminary work indicates that there are three sequentially formed populations of textures among magmatic phases: 1. population of anhedral quartz and plagioclase; 2. population of euhedral grains that includes quartz, sandine, plagioclase, biotite, hornblende, Fe-Ti oxides, zircon and apatite; 3. boxy cellular (skeletal?) sanidine and quartz. We speculate that the first population are resorbed antecrysts, the second formed prior to eruption as autocrysts (at or near equilibrium?), and the third formed soon before or during eruption.

  8. Geochemical evidence for contribution of ore-forming materials from peraluminous granite basement-- Taking Fucheng pluton and No. 6722 uranium deposit in southern Jiangxi Province as examples

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Bangtong(章邦桐); CHEN; Peirong(陈培荣); YANG; Dongsheng(杨东生); KONG; Xinggong(孔兴功)

    2003-01-01

    Using the induced fission-track method, mobile uranium leaching and lead isotope analysis, this work obtianed geochemical features of the peraluminous Fucheng granite basement and the host rock (shoshonite) of the No. 6722 uranium deposit in southern Jiangxi Province. (i) Uranium contents of the leucocratic rock-forming minerals (0.18 ?g/g for quartz, 0.36 ?g/g for feldspar) are lower than the uranium content of the whole rock (4.6 ?g/g). Biotite and some accessory mineral inclusions (zircon, monazite and uraninite) are the main uranium carriers of the Fucheng granite pluton. The fissure uranium in altered minerals (hydromica and chlorite) increased evidently. (ii) Leachable rate of mobile uranium in the biotite granite is 10.4%, while that in the altered granite increased to 31%. (iii) Caculation based on lead isotopes shows that during alteration the Fucheng granite lost uranium (?U = ?37% - ?65%), whereas the Caotaobei shoshonite gained uranium (?U = +37%- +58%). These features suggest that the ore-forming material of the No. 6722 uranium deposit was mainly derived from the altered peraluminous granite basement of Fucheng pluton.

  9. Evolution of the Geysers (US) - Data From Fluid-Inclusion Microthermometry and Gas Geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Moore, J.N.; Hulen, J.B.; Norman, D.I.

    1995-01-01

    The Geysers, California, is the site of an active hydrothermal system that initially developed between about 1.5 and 2 Ma in response to intrusion of a hypabyssal granitic pluton. Mineralogic and fluid-inclusion data demonstrate that the present vapor-dominated regime evolved from an earlier and more extensive, liquid-dominated hydrothermal system. Circulation of these early fluids produced veins characterized by tourmaline and/or biotite {+-} actinolite {+-} clinopyroxene within the pluton and adjacent biotite-rich hornfels, actinolite {+-} ferroaxinite {+-} epidote, and epidote {+-} chlorite {+-} wairakite within the intermediate parts of the thermal system, and calcite in the outer parts. Potassium feldspar and quartz are present in all assemblages. Maximum pressure-corrected homogenization temperatures and apparent salinities of fluid-inclusions in these veins range from 440 C and 44 weight percent NaCl equivalent within the hornfels (<600 m from the pluton) to 325 C and 5 weight percent NaCl equivalent at approximately 1500 m from the intrusion. We suggest that the shallow, moderate-salinity fluids are crustal waters modified by water-rock interactions and that the high-salinity fluids are magmatic brines. The formation of vapor-dominated conditions is reflected in the abrupt appearance of low salinity (0.0 to 0.4 weight percent NaCl equivalent) fluid inclusions with homogenization temperatures near 265 C. These inclusion fluids are thought to represent steam condensate formed as the liquid-dominated system boiled off.

  10. The chemistry, mineralogy, and petrology of the George Ashley Block pegmatite body

    Science.gov (United States)

    Kleck, W.D.; Foord, E.E.

    1999-01-01

    The George Ashley Block (GAB) is a rockslide block located in the Pala pegmatite district of Southern California. It is layered, asymmetric, pocket containing, and peraluminous. The GAB consists of quartz (42 vol%), Na-rich plagioclase (27%), potassium feldspar (24%), muscovite (7%), Mn-rich garnet (2%), biotite (1%), and a trace of tourmaline and gahnite. It contains only small amounts of the incompatible elements that characterize differentiated pegmatite bodies. P2O5, MnO, and F are present in amounts of < 1 wt% each; B, Be, Ce, Li, Nb, Nd, and Th are < 100 ppm each. More than 90% of the garnet grains in the GAB are zoned toward Mn-rich rims, and a symmetrical change in garnet-core composition occurs across the body. The mean X site contents for garnet (in at%) are 57% Fe, 40% Mn, 3.1% Mg, and 0.4% Ca. The Mn contents of garnet range from 30 to 55 at%; Fe contents vary inversely with Mn and range from about 66 to 43 at%. It is concluded that the bulk chemistry yields little information about fractionation, but the garnet, muscovite, and biotite mineral chemistry is more useful. There may have been two separate injections of magma to form the GAB.

  11. Mineralogic Investigation into Occurrence of High Uranium Well Waters in Upstate South Carolina, USA

    International Nuclear Information System (INIS)

    High levels of U (up to 5570 (micro)g/L) have been discovered in well waters near Simpsonville, South Carolina, USA. In order to characterize the mineralogical source of the U and possible structural controls on its presence, a deep (214 m) well was cored adjacent to one of the enriched wells. The highest gamma-ray emissions in the recovered core occur in coarse biotite granite at a depth just below 52 m. A slickenlined fault plane at 48.6 m and narrow pegmatite layers at depths of 113, 203 and 207 m also yield high gamma-ray counts. Thin sections were made from the above materials and along several subvertical healed fractures. Uraninite and coffinite are the principal U-rich minerals in the core. Other U-bearing minerals include thorite and thorogummite, monazite, zircon and allanite. Primary uraninite occurs in the biotite granite and in pegmatite layers. Secondary coffinite is present as tiny (6+) hydroxyl-carbonate complex. Later reduction resulted in secondary precipitation along fractures as a U4+ mineral (i.e., coffinite).

  12. A tin-mineralized topaz rhyolite dike with coeval topaz granite enclaves at Qiguling in the Qitianling tin district, southern China

    Science.gov (United States)

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

    2013-06-01

    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.

  13. Petrology and geochemistry of the Eastern Loma de Cabrera Batholith, Dominican Republic

    Energy Technology Data Exchange (ETDEWEB)

    Cribb, J.W.; Lewis, J.F.

    1985-01-01

    The Eastern Loma de Cabrera Batholith, located in the NW Cordillera Central, Dominican Republic, is a heterogeneous intrusive complex composed of a zoned ultramafic-mafic core surrounded by tonalite and diorite. The batholith intrudes metasbasaltic rocks of the Duarte Complex of early Cretaceous age. The ultramafic-mafic core consists of peridotite, olivine-pyroxenite, pyroxenite, and augite-hypersthene gabbro-norite. Pyroxenites and gabbro-norites exhibit large scale interlayering and small scale layering involving a regular variation in the proportions of ortho- and clinopyroxene. Tonalities and diorites are mafic to leucocratic, some being porphyritic. Petrographic types include hornblende, hornblende-pyroxene, hornblende-biotite, and muscovite-biotite types. Aplites are abundant. Intrusive relations suggest that ultramafic-mafic complex is the oldest intrusive phase, and was partially amphibolitized during later intrusion of the felsic rocks. Ultramafic-mafic rocks contain 43-54% SiO/sub 2/ and MgO ranges from 8-45%. Trace and REE in these rocks are relatively depleted. Tonalitic rocks range in SiO/sub 2/ from 53-76%, with K/sub 2/O varying from 0.15-2.9%. In addition, they are LREE enriched. A small Eu anomaly is best explained by fractionation of plagioclase and hornblende. Trends shown by Rb-Sr data suggest that fractional crystallization of hornblende and plagioclase, that is high level fractionation, is the important factor in controlling chemical variation in the tonalites.

  14. Early and Late Alkali Igneous Pulses and a High-3He Plume Origin for the Deccan Flood Basalts.

    Science.gov (United States)

    Basu, A R; Renne, P R; Dasgupta, D K; Teichmann, F; Poreda, R J

    1993-08-13

    Several alkalic igneous complexes of nephelinite-carbonatite affinities occur in extensional zones around a region of high heat flow and positive gravity anomaly within the continental flood basalt (CFB) province of Deccan, India. Biotites from two of the complexes yield (40)Ar/(39)Ar dates of 68.53 +/- 0.16 and 68.57 +/- 0.08 million years. Biotite from a third complex, which intrudes the flood basalts, yields an (40)Ar/(39)Ar date of 64.96 +/- 0.1 1 million years. The complexes thus represent early and late magmatism with respect to the main pulse of CFB volcanism 65 million years ago. Rocks from the older complexes show a (3)He/(4)He ratio of 14.0 times the air ratio, an initial (87)Sr/(86)Sr ratio of 0.70483, and other geochemical characteristics similar to ocean island basalts; the later alkalic pulse shows isotopic evidence of crustal contamination. The data document 3.5 million years of incubation of a primitive, high-(3)He mantle plume before the rapid eruption of the Deccan CFB. PMID:17783739

  15. Chronology and geochemistry of Mesozoic granitoids in the Bengbu area, central China: Constraints on the tectonic evolution of the eastern North China Craton

    Science.gov (United States)

    Yang, De-Bin; Xu, Wen-Liang; Wang, Qing-Hai; Pei, Fu-Ping

    2010-01-01

    We performed zircon U-Pb dating and analyses of major and trace elements, and Sr-Nd-Pb isotopes for granitoids in the Bengbu area, central China, with the aim of constraining the magma sources and tectonic evolution of the eastern North China Craton (NCC). The analyzed zircons show typical fine-scale oscillatory zoning, indicating a magmatic origin. Zircon U-Pb dating reveals granitoids of two ages: Late Jurassic and Early Cretaceous ( 206Pb/ 238U ages of 160 Ma and 130-110 Ma, respectively). The Late Jurassic rocks (Jingshan intrusion) consist of biotite-syenogranite, whereas the Early Cretaceous rocks (Huaiguang, Xilushan, Nushan, and Caoshan intrusions) are granodiorite, syenogranite, and monzogranite. The Late Jurassic biotite-syenogranites and Early Cretaceous granitoids have the following common geochemical characteristics: SiO 2 = 70.35-74.56 wt.%, K 2O/Na 2O = 0.66-1.27 (mainly Nushan and Xilushan granitoids, suggests that the primary magmas were derived from partial melting of the Yangtze Craton (YC) basement. In contrast, the occurrence of Paleoproterozoic and Paleoarchean inherited zircons within the Huaiguang granitoids indicates that their primary magmas mainly originated from partial melting of the NCC basement. The occurrence of YC basement within the lower continental crust of the eastern NCC indicates that the YC was subducted to the northwest beneath the NCC, along the Tan-Lu fault zone, during the early Mesozoic.

  16. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil; Petrologia e geocronologia (U/Pb-Sm/Nd) do Granito Passagem, Complexo Granitoide Pensamiento, SW do Craton Amazonico (MT)

    Energy Technology Data Exchange (ETDEWEB)

    Jesus, Gisely Carmo de, E-mail: giselycarmo@hotmail.co [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Programa de Pos-Graduacao em Geociencias; Sousa, Maria Zelia Aguiar de, E-mail: mzaguiar@terra.com.b [Universidade Federal de Mato Grosso(ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Recursos Minerais; Ruiz, Amarildo Salina; Matos, Joao Batista de, E-mail: asruiz@gmail.co, E-mail: jmatos@cpd.ufmt.b [Universidade Federal de Mato Grosso (ICET/UFMT), Cuiaba, MT (Brazil). Inst. de Ciencias Exatas e da Terra. Dept. de Geologia Geral

    2010-09-15

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  17. Petrography and geochronology (U/Pb-Sm/Nd) the Passagem Granite, Pensamiento Granitoid Complex, Paragua Terrane, SW Amazon Craton, Mato Grosso, Brazil

    International Nuclear Information System (INIS)

    The Passagem granite includes stocks, plugs and dikes located in the Ricardo Franco hill - Vila Bela da Santissima Trindade region - state of Mato Grosso, central Brazil. The Passagem Granite is included in the Paragua terrane - SW Amazonian Craton. It consists of isotropic monzogranite, sienogranite and more rarely granodiorites with leucocratic dark gray to white color. These rocks range from hypidomorphic inequigranular to xenomorphic texture, fine to medium grained. Biotite is the only primary mafic present as essential phase and characterize an expanded slightly acid sequence formed by a sub-alkaline magmatism of high-potassium calc-alkaline, slightly peraluminous composition from arc magmatic tectonic environment during a post-collisional period. Mechanism of fractional crystallization of plagioclase, biotite, titanite, apatite and zircon associated with simultaneous crustal assimilation are suggested for the evolution of these rocks. The results support the hypothesis of a post-collisional magmatism in the Paragua terrane at 1284 +- 20 Ma corresponding to the crystallization age of the Passagem granite. This paper propose that Passagem Granite represents as an extension in Brazilian terrane of the Pensamiento Granitoid Complex. (author)

  18. Evidences of a transamazonic cycle in Cabo Frio region, RJ, Brazil and its correlation with the craton of Angola, Africa

    International Nuclear Information System (INIS)

    The U-Pb dating in zircon based on air-abrasion method, whole rock Rb-Sr one, and K-Ar ones in biotite and amphibole of the samples collected from the Cabo Frio Region, Ribeira Orogenic Belt, have been carried out. The concordia diagram of the U-Pb dating indicates 2 different ages: 1981 ± 18 Ma for the upper intersect corresponding to the Transamazonic Cycle, and 488 ± 55 Ma for the lower one, Brazilian Cycle. The former is interpreted as age of zircon formation and the latter, as the time elapsed since epsodic lead loss. The whole rock Rb-Sr dating also shows Transamazonic age: 1799 ± 62 Ma, IR=0.706, and MSWD+0.570. The K-Ar age in amphibole is 571 ± 44 Ma and that in biotite is 474 ± 6 Ma. These data lead to the conclusion that the rocks of this region was formed in the Trasamazonic Cycle and remetamorphosed in the Brazilian Cycle. (author)

  19. 40Ar/39 Ar and paleomagnetic results from the Guapore shield: further implications for the nature of middle-late proterozoic mobile belts of Gondwana land

    International Nuclear Information System (INIS)

    Twenty sites in diverse rock units of the Serra dos Carajas region provide the first paleomagnetic poles from the Guapore shield of the Amazonian Craton. The most reliable results were obtained from the Pium Complex and the Carajas and Seringa granites. The ages of magnetization of these units are reasonably well constrained by isotopic data: 40 Ar/39 Ar data on a Pium hornblende indicate an Archean (>2.7 Ga) age for high grade metamorphism, but biotite and plagioclase from the same sample, plus biotite from another, all record a trans-Amazonian overprint. Thus the trans-Amazonian orogeny in this area produced temperatures between ca. 300 and 500 o C, apparently sufficient to re magnetize these rocks, and was followed by relatively rapid cooling uninterrupted by significant later regional metamorphism. Emplacement of the Carajas and Seringa granites, members of an extensive suite of anorogenic granitoids of the craton, is reasonably well constrained by previous studies at 1.70 to 1.83 Ga. A F and thermal demagnetization of specimens from three sites in the Pium complex and one in each of the granites reveals multicomponent behavior, but characteristic direction with moderately high coercivity and/or blocking temperature were isolated from all five sites. (author)

  20. First evidence for expressive neoproterozoic intraplated mafic rocks and magma mixing in post-collisional A-PA type granites, Southern Brazil: Geochemistry and U-Pb (zircon), Nd-Sr-18O(zircon) isotope investigations

    International Nuclear Information System (INIS)

    New and recent geological investigations around Pien-Tijucas suture zone, between Luis Alves and Curitiba Microplates (Basei et al.2000) led to mapping of Palermo, Agudos do Sul and Rio Negro A-PA type Granites with expressive expositions of alkaline felsic ans mafic rocks and, associated mafic and felsic hybrid rocks. The suture zone is formed by subduction arc-related Pien-Mandirituba deformed calc-alkaline I-type granite belt and serpentinized supra subduction zone (SSZ) obducted mantle rocks with intrusive Neoproterozoic (650-630 Ma) very high Cr and Ni tholeitic gabbros. The Pien-Mandirituba calc-alkaline I-type Granite Belt is constituted by three main granite suites. The older emplaced pre-collisional suite is constituted by deformed to highly deformed amphibole and biotite-rich, magmatic epidote-absent quartz-monzodiorites and granodiorites formed between 620 and 610 Ma. The second sincollisional granite suite is constituted by deformed and slightly deformed low content amphibole-biotite-magmatic epidote-bearing, quartz-monzodiorites, granodiorites and leucogranodiorites emplaced between 605 and 595 Ma. The third, also sincollisional, granite suite is deformed to highly deformed biotite ± amphibole monzogranites. The deformation age of the three non-cogenetic granite suites of this granite belt is between 605-595 Ma. The granite rocks of the Pien-Mandirituba Granite Belt are meta-aluminous to slightly peraluminous, high K calc-alkaline, generally with high Ba, high Sr and low Rb contents. Palermo, Agudos do Sul and Rio Negro Granites are components of the expressive Neoproterozoic volcanic and plutonic alkaline-peralkaline Serra do Mar Suite (Kaul 1997), emplaced in extensional post-collisional and anorogenic settings along the central portion and northern border of the Luis Alves Microplate and southern border of the Curitiba Microplate. Magma mixing evidence is rare ou absent in the other components of the Serra do Mar volcanic and plutonic suite. The

  1. Magmatic epidote, hornblende barometric estimates, and emplacement of the Conceicao das Creoulas pluton, Alto Pajeu Terrane, NE Brazil

    International Nuclear Information System (INIS)

    The Brasiliano-age magmatic epidote-bearing Conceicao das Creoulas batholith, in the Transversal Zone superterrane in northeastern Brazil, intruded migmatites and metagranitoids of the Riacho do Forno/Recanto Formations. This pluton is composed of porphyritic granodiorite and porphyritic monzogranite. Hornblendes in this pluton solidified between 6-7 Kbar in mafic enclaves and around 8 Kbar for porphyritic granodiorite as estimated by its Al contents. Temperatures for zircon saturation are in the 790-830 deg C range for the mafic enclaves and 800-850 deg C for the porphyritic granodiorite, whereas hornblende-plagioclase pairs yielded temperatures in the 670-690 de C range. In this pluton, epidote, undoubtedly of magmatic origin, with or without allanite cores, included in plagioclase, is rimmed by biotite or is partially resorpted by the magma. Sometimes, patches of hornblende and biotite are present inside epidote. Magmatic epidote compositions vary in the interval 20-25% mole of pistacite, and always exhibit Ti O2 < 0.20% by weight. This compositional range suggested crystallization along the NNO buffer. High initial ratio suggest a significant crustal component in the magma genesis. The magma probably was transported upward by diking and inflated outwards near or at its final site of emplacement, giving to the pluton a diapiric appearance. (author)

  2. Science Letters: Discovery of ultrahigh-T spinel-garnet granulite with pure CO2 fluid inclusions from the Altay orogenic belt, NW China

    Institute of Scientific and Technical Information of China (English)

    厉子龙; 陈汉林; SANTOSHM.; 杨树锋

    2004-01-01

    We first report discovery of the spinel-garnet-orthopyroxene granulite with pure CO2 fluid inclusions from the Fuyun region of the late Paleozoic Altay orogenic belt in Central Asia, NW China. The rock is characterized by an assemblage of garnet, orthopyroxene, spinel, cordierite, biotite, plagioclase and quartz. Symplectites of orthopyroxene and spinel, and orthopyroxene and cordierite indicate decompression under UHT conditions. Mineral chemistry shows that the orthopyroxenes have high XMg and Al2O3 contents (up to 9.23 wt%). Biotites are enriched in TiO2 and XMg and are stable under granulite facies conditions. The garnet and quartz from the rock carry monophase fluid inclusions which show peak melting temperatures of around -56.7℃, indicating a pure CO2 species being presented during the ultrahigh-T metamorphism in the Altay orogenic belt. The inclusions homogenize into a liquid phase at temperatures around 15.3-23.8℃ translating into CO2 densities of the order of 0.86-0.88g/cm3. Based on preliminary mineral paragenesis, reaction textures and petrogenetic grid considerations, we infer that the rock was subjected to UHT conditions. The CO2-rich fluids were trapped during exhumation along a clockwise P-T path following isothermal decompression under UHT conditions.

  3. 3D modelling and sheath folding at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit and implications for exploration in a 1.9 Ga ore district, Fennoscandian Shield, Sweden

    Science.gov (United States)

    Kampmann, Tobias C.; Stephens, Michael B.; Weihed, Pär

    2016-01-01

    Altered and mineralized rocks at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, situated in the Palaeoproterozoic Bergslagen ore district in the south-western part of the Fennoscandian Shield, have been metamorphosed at low-pressure, amphibolite-facies conditions and affected by ductile deformation. Using combined surface mapping of lithology and structure, drill core logging and microstructural work, the polyphase (D1 and D2) ductile deformation is demonstrated and a 3D model for the deposit created. Mineral associations include quartz, biotite, cordierite, anthophyllite, and minor almandine, andalusite and chlorite in silicate-rich altered rock, calcite or dolomite in marble and tremolite-actinolite or diopside-hedenbergite in skarn. The silicate minerals show varying growth patterns during the different phases of the tectonothermal evolution, with considerable static grain growth occurring between D1 and D2, and even after D2. F2 sheath folding along axes that plunge steeply to the SSE, parallel to a mineral stretching lineation and the dip direction of the S2 foliation, is suggested as a key deformation mechanism forming steeply plunging, cone- to rod-shaped mineralized bodies. This contrasts with a previous structural model invoking fold interference. A major shear zone with talc-chlorite-(quartz-biotite) mineral association separates the northern and southern structural domains at the deposit and bounds the polymetallic massive sulphides to the north.

  4. 40Ar/39Ar ages of granitoids from the Truong Son fold belt and Kontum massif in Laos

    International Nuclear Information System (INIS)

    Geochemical and geochronological studies were conducted on granitoids in central-southern Laos. S-type ilmenite-series granitoids associated with Sn mineralization are distributed in the Truong Son fold belt of central Laos. Plateau ages determined by 40Ar/39Ar incremental heating method for biotite and muscovite of the granitoids range from 253 Ma to 247 Ma and from 244 Ma to 199 Ma in the southwest and northeast of the fold belt, respectively. During this period, the fractionated granites in the early stage are related to mineralization of medium-large Sn deposits. The granitoids of the Truong Son fold belt formed in the Indosinian orogeny are contemporaneous with the Late Permian-Early Jurassic Sn-bearing granites in the Southeast Asian Sn Belt. In contrast, I-type magnetite-series granitoids are distributed in the Kontum massif of southeasternmost Laos. Plateau ages for biotite and previously reported mineral ages of the magnetite-series granitoids range widely from 414 Ma to 252 Ma. The Carboniferous-Permian granitoids represents adakitic characteristics and the Permian adakitic granodiorites are associated with Cu ± Au mineralized quartz veins. (author)

  5. The Cananeia Alkaline Body in the South Coast of São Paulo State: Mineral Chemistry

    Directory of Open Access Journals (Sweden)

    Celso de Barros Gomes

    2009-01-01

    Full Text Available The Cananeia alkaline occurrence of Late Cretaceous age (Ar-Ar, 83.6 Ma lies in the Ribeira Valley and it is representedby two small bodies: Morro de São João (1.8 km2 in Cananeia Island, and Morrete (0.4 km2, in the neighboringComprida Island. It is covered by Quaternary sediments and mostly constituted by intrusive rocks of syenitic composition,assembled into two principal groups: alkali feldspar syenites and quartz-alkali feldspar syenites. Microsyenites of variabletexture are subordinate. Regarding the mineralogy, the rocks are very rich in feldspars, mesoperthite being the most abundantphase, and plagioclase is only occasionally found as isolated crystals. Mafi c minerals consist dominantly of clinopyroxenesand amphiboles, both belonging to the calcic, calcic-sodic and sodic groups and showing signifi cant chemicalvariations, such as the increase in the Fe/Mg ratio and Na content, and the decrease in Ca, as a function of the degree ofevolution of the rocks. Textural relationships show that clinopyroxene reacts to form amphibole. Biotite is common, mainlyin association with amphibole and opaques. Biotite and opaques together are found at the borders of amphibole grainsor concentrated along their fractures and cleavage planes. Fayalitic olivine is rarely preserved. Most common accessoriesinclude opaques, mainly magnetite with exsolved ilmenite lamellae, apatite, titanite and zircon. Late to post-magmatic alterationprocesses can explain the replacement textures shown by the principal primary minerals and the exsolution structuresfound in feldspars and opaques.

  6. Ion microprobe 207Pb/206Pb zircon ages for gneiss-granitoid rocks from Bundelkhand massif: evidence for Archaean components

    International Nuclear Information System (INIS)

    Radiometric 207Pb/206Pb ages of individual zircons from the Bundelkhand massif, central India, have been determined by an ion microprobe. Samples from various major litho-units, viz. the granite gneiss, hornblende-, biotite- and leuco-granitoid are included in this study. The results provide evidence for the presence of Archaean crustal components within this massif. Zircons with ages of 3.0 to 3.2 Ga occur as xenocrysts in a sample of granite gneiss from Lalitpur having a minimum formation age of 2.5 Ga. Another sample of a highly deformed gneiss from Babina has a well-defined age of 2.7 Ga. Emplacement of hornblende-granitoid and biotite-granitoid took place in quick succession at ∼ 2.5 Ga. No firm age for the youngest plutonic component, the leuco-granitoid, could be obtained due to poor recovery of zircons suitable for analysis. The geochronological data confirm the suggestion, based on geochemical studies, that the gneisses and the granitoids in this region represent Archaean and post-Archaean components respectively. (author)

  7. Geological, geochemical and isotopic characteristics of the Archaean Kaap Valley pluton, Barberton mountain land, South Africa

    International Nuclear Information System (INIS)

    The Kaap Valley pluton consists predominantly of a homogeneous weakly foliated, hornblende-bearing tonalite. It is among the oldest granitoid bodies yet recognized in the environs of the Barberton greenstone belt, yielding 207Pb/206Pb mineral ages of about 3300 Ma and a Rb-Sr whole rock isochron age of about 3500 Ma. The Kaap Valley pluton is distinctive in many respects. Whereas all other gneiss plutons in the area are characterized by a trondhjemitic bulk composition with mafic mineralogies dominated by biotite, the Kaap Valley pluton is tonalitic in bulk composition with hornblende (plus minus minor biotite) as its major mafic phase. In this paper, the results of a detailed geological, geochemical and Pb-isotopic study of the Kaap Valley pluton are presented. Questions relating to the origin of the body are considered, with an emphasis on the formation of a tonalitic magma which is more mafic than those typically encountered in the region. Although exposure does not permit a detailed structural study of the gneiss pluton consideration is given to its mode of emplacement

  8. Magnetic properties of sheet silicates

    International Nuclear Information System (INIS)

    Susceptibility, magnetisation and Moessbauer measurements are reported for a representative selection of 2:1 layer phyllosilicates. Eight samples from the mica, vermiculite and smectite groups include examples diluted in iron which are paramagnetic at all temperatures, as well as iron-rich silicates which order magnetically below 10 K. Anisotropic susceptibility of crystals of muscovite, biotite and vermiculite is quantitatively explained with a model where the Fe2+ ions lie in sites of effective trigonal symmetry, the trigonal axis lying normal to the sheets. The ferrous ground state is an orbital singlet. Ferric iron gives an isotropic contribution to the susceptibility. Fe2+-Fe2+ exchange interactions are ferromagnetic with Gapprox. equal to2 K, whereas Fe3+-Fe3+ coupling is antiferromagnetic in the purely ferric minerals. A positive paramagnetic Curie temperature for glauconite may be attributable to Fe2+ → Fe3+ charge transfer. Magnetic order was found to set in inhomogeneously for glauconite at 1-7 K. One biotite sample showed an antiferromagnetic transition at Tsub(N) = 7 K marked by a well-defined susceptibility maximum. Its magnetic structure, consisting of ferromagnetic sheets with moments in their planes coupled antiferromagnetically by other, weak interactions, resembles that found earlier for the 1:1 mineral greenalite. (orig.)

  9. Cesium adsorption/desorption behavior of clay minerals considering actual contamination conditions in Fukushima

    Science.gov (United States)

    Mukai, Hiroki; Hirose, Atsushi; Motai, Satoko; Kikuchi, Ryosuke; Tanoi, Keitaro; Nakanishi, Tomoko M.; Yaita, Tsuyoshi; Kogure, Toshihiro

    2016-02-01

    Cesium adsorption/desorption experiments for various clay minerals, considering actual contamination conditions in Fukushima, were conducted using the 137Cs radioisotope and an autoradiography using imaging plates (IPs). A 50 μl solution containing 0.185 ~ 1.85 Bq of 137Cs (10-11 ~ 10-9 molL-1 of 137Cs) was dropped onto a substrate where various mineral particles were arranged. It was found that partially-vermiculitized biotite, which is termed “weathered biotite” (WB) in this study, from Fukushima sorbed 137Cs far more than the other clay minerals (fresh biotite, illite, smectite, kaolinite, halloysite, allophane, imogolite) on the same substrate. When WB was absent on the substrate, the amount of 137Cs sorbed to the other clay minerals was considerably increased, implying that selective sorption to WB caused depletion of radiocesium in the solution and less sorption to the coexisting minerals. Cs-sorption to WB continued for about one day, whereas that to ferruginous smectite was completed within one hour. The sorbed 137Cs in WB was hardly leached with hydrochloric acid at pH 1, particularly in samples with a longer sorption time. The presence/absence of WB sorbing radiocesium is a key factor affecting the dynamics and fate of radiocesium in Fukushima.

  10. The Encantada Granite: registration of a peraluminous intrusion in the Rondonian Province - San Ignacio, in SW Amazonic Craton, Mato Grosso, Brazil

    Directory of Open Access Journals (Sweden)

    Brena Verginassi do Nascimento

    2015-06-01

    Full Text Available The Encantada Granite occurs on the extreme southwest of the state of Mato Grosso, SW of the Amazonian Craton, near the border of Brasil/Bolívia. It corresponds to an body oriented to NNW direction that intruded metasedimentary and metavolcanic rocks. It consists of leucogranites with monzo- to sienogranitic composition, marked by prominent schistosity. It is characterized by equigranular to porphyritic inequigranular texture, and composed of quartz, K-feldspar, plagioclase, muscovite and biotite with garnet, zircon, allanite and opaque minerals. Chlorite and epidote are the most common secondary minerals. The geochemical study allows the classification of the magmatism as having acid character, sub-alkaline, high-potassium-calc-alkaline to shoshonitic type. These rocks have alumina index saturation higher than 1, with normative corundum, and thus classified as peraluminous granite. Due to the reflection of the excess of aluminium, they have various aluminous phases, mainly muscovite, biotite and garnet; presents typical pattern of calc-alkaline rocks rich in potassium with enrichment of light ETRs over the heavy ones. The collected data allows to consider that the Encantada Granite rocks were generated from the partial melting of crustal rocks of pelitic composition.

  11. Geology and uranium mineralisation in the Deccan trap-lameta-crystalline basement at Lalbarra, Mandla district, Madhya Pradesh, India

    International Nuclear Information System (INIS)

    Proterozoic crystalline rocks of Lalbarra area comprise banded migmatites, biotite granites, and two-mica granites carrying components of pre-existing Sausar group metasediments. The biotite schists of the Sausar group had inherent anomalous radioelement contents mainly within the silicate bound structures of zircon and epidote. On being subjected to migmatisation and granitisation, the uranium has been partially re-distributed. Consequent to the emplacement of volatile rich two-mica granite (TMG) along shears, uranium is by and large partitioned from thorium and got enriched in TMG in labile state. A hiatus of long duration intervened before the Infratrappean (lametas) fresh water, sedimentary rocks with its provenance area comprising among others, the fertile TMG, were laid. Basalt flows of Deccan trap age which had covered the lametas and the basement are presently found as thin (<20 m) outliers. Uranium mineralisation is found at the Deccan trap (basalt)-lameta-crystalline basement contact zone hosted in ferruginous chert veins occupying fractures in the basal part of the flow as well as in pseudo quartzites in the lameta formation. Radioactivity is largely due to uranophane associated with ferruginous cherty matter. (author). 11 refs., 2 tabs., 2 figs

  12. Change from calc-alkaline to adakitic magmatism recorded in the Early Cretaceous Darran Complex, Fiordland, New Zealand

    International Nuclear Information System (INIS)

    The Early Cretaceous Darran Complex of the Median Tectonic Zone near Milford, South Island, New Zealand, consists dominantly of biotite - two-pyroxene diorites cut by biotite-hornblende microdiorite and quartz monzodiorite dikes. The host diorite gives a 138 ± 2.9 Ma SHRIMP age on zircons, which is interpreted to be the age of igneous crystallisation. The calc-alkaline geochemistry of the host diorites and the microdiorites is attributed to melting of a mantle wedge source fluxed by slab-derived fluids. Ductile deformation (D1) of the host diorite and the microdiorite dikes took place at mid-upper amphibolite facies conditions, with extension lineations indicating a top to the NNE sense of shear. A SHRIMP age of 136 ± 1.9 Ma on zircons from a quartz monzodiorite dike injected along D1 shears is statistically indistinguishable from that of the host diorite. This suggests that D1 was synmagmatic and that subduction, during or shortly after magma emplacement, was oblique to the Gondwana margin at c. 138 Ma. The quartz monzodiorite dikes are enriched in Na2O, Al2O3, and Sr, depleted in Y, and have a distinctly adakitic geochemistry. The change in chemistry from calc-alkaline magmas to alkali-calcic adakitic magmas reflects the melting of a mafic, garnet-bearing, essentially plagioclase-free source in the root of a volcanic arc system. (auth)

  13. Sr isotope evolution during chemical weathering of granites -- impact of relative weathering rates of minerals

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Sr isotopic systematics in the weathering profiles of biotite granite and granite porphyry in southern Jiangxi Province were investigated. The results showed that during the chemical weathering of granites, remarked fractionation occurred between Rb and Sr. During the early stages of chemical weathering of granites, the released Sr/Si and Sr/Ca ratios are larger than those of the parent rocks, and the leaching rate of Sr is higher than those of Si, Ca, K, Rb, etc. Dynamic variations in relative weathering rates of the main Sr-contributing minerals led to fluctuation with time in 87Sr/86Sr ratios of inherent and released Sr in the weathering crust of granite. Successive weathering of biotite, plagioclase and K-feldspar made 87Sr/86Sr ratios in the weathering residues show such a fluctuation trend as to decrease first, increase, and then decrease again till they maintain stable. This work further indicates that when Sr isotopes are used to trace biogeochemical processes on both the catchment and global scales, one must seriously take account of the prefer-ential release of Sr from dissolving solid phase and the fluctuation of 87Sr/86Sr ratios caused by the variations of relative weathering rates of Sr-contributing minerals.

  14. Relationship between the isotopic composition of strontium in newly formed continental clay minerals and their source material

    International Nuclear Information System (INIS)

    The 87Sr/86Sr ratios of recent montmorillonites and kaolinites newly formed in weathering profiles of western and central Africa and of Nosy Be and La Reunion islands near Madagascar are directly related to the composition and age of the parent rocks or minerals. They may, therefore, be used as a genetic tracer. The 87Sr/86Sr ratios are about 0.704 when these clays crystallise from recent basalts and they are higher than 0.715 when the parent rocks are of sialic composition and old in age. Kaolinites newly formed in situ from feldspars contain small amounts of Sr with abnormally high 87Sr/86Sr ratios: in this study they are higher than 1.094. When these minerals crystallize from biotites, their 87Sr/86Sr ratios are much lower and can be close to the value of the primary Sr trapped in the biotites during their crystallization. On the other hand, the 87Sr/86Sr of continental montmorillonites are less scattered: they range, in this study, between 0.704 and 0.722. These low values, as well as the high adsorption capacities of these minerals in the sedimentary environment, allow the assumption that they frequently have 87Sr/86Sr ratios close to that of marine Sr during sedimentation. Therefore, montmorillonites are able to form homogeneous authigenic minerals by synsedimentary alterations. (Auth.)

  15. Time constraint based on zircon dating for the Jacareacanga group (Tapajos province, Amazon craton, Brazil)

    International Nuclear Information System (INIS)

    During long time the Jacareacanga meta-volcano sedimentary sequence have been interpreted as Archean greenstone belt terrain. However, recent data are indicating younger U-Pb ages about 2.1 Ga. In the Tapajos Province (Amazon Craton), the Cuiu-Cuiu Complex (2.00-2.03 Ga), Creporizao granitoids (1.99-1.96 Ga) and Jacareacanga Group are the oldest rocks. The Jacareancaga Group is composed by quartzmica schists, quartzites, ferruginous quartzite, metachert, and minor talc-tremolite-chlorite schist, actinolite-epidote schist, hornfels, metargilites and metawackes metamorphosed in low to medium-grade conditions. The aim of the present paper is to estabilish the maximum age of Jacareacanga sedimentation and identify probable sources in Espirito Santo region (Espirito Santo muscovite-biotite schist). In this research, similar and new results are obtained by zircon evaporation methodology. This research shows geochronological data about the Espirito Santo muscovite-biotite schist related to Jacareacanga Group (Ferreira et al., 2000) in Tapajos Province (Amazon Craton). The area is located near Amazonas and Para States boundary (Northern Brazil) and the sample was obtained at Espirito Santo (garimpo) small-scale gold mine (06o00min.48seg.S,58o08min.17seg.W) (au)

  16. 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

    Science.gov (United States)

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

    2015-04-01

    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

  17. Low-rhenium molybdenite by metamorphism in northern Sweden: Recognition, genesis, and global implications

    Science.gov (United States)

    Stein, Holly J.

    2006-04-01

    episodic melting of Archean-Paleoproterozoic supracrustal gneisses related to the Svecofennian orogeny. Petrographic traverses across the boundary between widespread, foliation-parallel units of aplitic to pegmatitic pink granite and hosting biotite gneiss directly capture the process of ore formation. Dehydration breakdown of zircon-rich biotite aligned with the foliation in the gneiss is accompanied by formation of new pristine, post-deformational biotite plus sulfides, oxides, hydrothermal zircon and fluorite, all associated with microcline-dominant leucosomes. This process has profound implication for the traditional leucogranite, intrusion-related genesis attributed to the broad classification of Mo-W-Sn-base and precious metal mineralization (e.g., South Mountain Batholith, Nova Scotia; Okiep, Namaqualand, South Africa; Mactung, Yukon; Pogo-Liese, Tintina, Alaska; Carajás and Goiás-Rio Tocantins, Brazil; New England Batholith, NSW, Australia; Bergslagen, Sweden; Nevoria, Western Australia; Alpeinerscharte, Austria; Erzgebirge, Germany; Sardinia-Corsica Batholith). In addition to biotite, metallogenic contributions (e.g., Mo, W, Sn, U, Bi, Cu, Pb, Zn, Fe, Ni, Co, Au, Ag, Te, As, Sb, REE) in various combinations may also be controlled by breakdown of amphibole. In effect, the trace element composition of dehydrating or recrystallizing components in a gneissic rock essentially defines the local and district metallogenic suite. In the absence of focusing structures (e.g., shear zones, sheeted vein development), this process will generally form small and disconnected subeconomic deposits with erratic and unpredictable grades. Low Re content in associated molybdenite is a key indicator for a subeconomic origin by local melting of biotite gneiss (Mo-W) or muscovite schist (Sn-W).

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

    Science.gov (United States)

    Prakash, Abhishek; Saha, Lopamudra; Sarkar, Saheli

    2016-04-01

    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

  19. 浙西南八都群泥质麻粒岩的变质演化与pT轨迹%The metamorphic evolution and pT path of pelitic granulite from the Badu Group in southwestern Zhejiang Province

    Institute of Scientific and Technical Information of China (English)

    赵磊; 周喜文

    2012-01-01

    浙西南古元古界八都群是目前华夏地块最古老的变质基底,以往研究认为其变质程度仅达角闪岩相.近来在对遂昌地区八都群富铝片麻岩的研究过程中,发现了具有“石榴石+夕线石+正/反条纹长石+黑云母”特征组合的泥质麻粒岩,表明该地体曾经历麻粒岩相变质改造.通过岩相学与矿物化学分析,确定该岩石经历了3个阶段的演化过程,即:早期进变质阶段(M1),形成“石榴石+黑云母+白云母+夕线石+斜长石+石英”的矿物组合;变质峰期阶段(M2-3),形成“石榴石+夕线石+三元长石+黑云母+石英”的矿物组合;峰期后降压冷却阶段(M4),形成“黑云母+白云母+新生斜长石+石英”的矿物组合.岩石中石榴石普遍发育与降温过程有关的扩散成分环带和与降压过程有关的斜长石后生合晶.通过石榴石-黑云母温度计和GASP压力计估算变质峰期的温压条件为800~850℃、0.6~0.7 GPa,峰期后退变质阶段的温压条件为560~590℃、0.25~0.33 GPa,具有顺时针样式的PT演化轨迹,反映一种陆壳碰撞增厚、后又拉伸减薄的动力学过程.%The Paleoproterozoic Badu Group in southwestern Zhejiang Province is the oldest metamorphic basement in the Cathaysia block, and its metamorphic grade was previously considered to be only of amphibolite facies. Recently, pelitic granulite with the typical mineral assemblage of garnet + sillimanite + perthite + antiperthite + biotite was discovered in the Al-rich gneiss of Suichang area. According to petrographic observation, micro-mineral composition and calculating results from garnet-biotite thermometer and GASP barometer, three stages of metamorphism were recognized in the pelitic granulite. The early prograde metamorphic stage (M1) was detected on the basis of inclusions of biotite, muscovite and sillimanite in garnet. The peak metamorphic stage (M2.3) is characterized by the presence of garnet, biotite

  20. 贺兰山北段贺兰山岩群富铝片麻岩碎屑锆石LA-ICP-MS U-Pb定年及区域对比%LA-ICP-MS U-Pb detrital zircon geochronology of alumina-rich gneiss of the Helanshan complex-group in the northern segment of Helanshan Mountains and regional comparison

    Institute of Scientific and Technical Information of China (English)

    校培喜; 由伟丰; 谢从瑞; 李平; 白生明

    2011-01-01

    贺兰山北段贺兰山岩群中发育一套富铝片麻岩,AlO含量较高,总体与粘土质岩石化学成分相似,显示孔兹岩系的特征,变质矿物组合主要为石榴子石、堇青石、硅线石、十字石、紫苏辉石等,变质级别迭角闪岩相一麻粒岩相.从宗别立岩组含石榴矽线黑云二长片麻岩中选取100粒各种类型的锆石进行了LA-ICP-MS U-Pb同位素测年.获得47个测年数据,锆石年龄多数介于1.80~2.15Ga之间,峰值为2.00~2.05Ga.碎屑锆石年龄频谱图与鄂尔多斯地块北缘的集宁岩群和乌拉山岩群十分相似,总体与吕粱构造运动的时限一致,为华北克拉通成熟陆壳演化阶段的产物.证明孔兹岩系形成于古元古代,之后长期处于稳定状态,很少受到构造热事件的干扰.%The Helanshan Group exposed in the northern segment of Helangshan mountains is high-grade metamorphosed rocks which are mainly composed of grey-biotite-sillimanite-cordierite-monzonitic-gneiss, sillimanite-garnet-biotite-plagioclase-gneiss,garnet-biotite-plagioclase-leptynite, sillimanite-garnet-monzonitic-leptite, sillimanite-biotite- plagioclase-leptynite, graphite-marble and hypersthene-plagioclase-gneiss. The gneiss of Helanshan Group belongs to khondalite series characterized by rich in Al2O3 and similar geochemistry to clay rocks, and its protolith rocks assemblages are alumina rich pelite and siltstone, which indicate that the gneiss is a suite of stable continental margin terrigenous clastic rock, the metamorphosed mineral assemblages of gneiss consist of garnet,cordierite, sillimanite, staurolite, hypersthene and so on. Forty-seven U-Pb data were obtained by LA-ICP-MS method for the detrital zircons of four garnet- sillimanite-biotite-monzonitic-gneiss from the Helanshan Group in this study. The majority ages of the grains from these four samples are clustered in the 1.80-2.15Ga, with characteristic age probability peaks at 2.00-2.05Ga. The detrital zircons ages

  1. A complex magma reservoir system for a large volume intra- to extra-caldera ignimbrite: Mineralogical and chemical architecture of the VEI8, Permian Ora ignimbrite (Italy)

    Science.gov (United States)

    Willcock, M. A. W.; Bargossi, G. M.; Weinberg, R. F.; Gasparotto, G.; Cas, R. A. F.; Giordano, G.; Marocchi, M.

    2015-11-01

    Intra-caldera settings record a wealth of information on caldera-forming processes, yet field study is rarely possible due to lack of access and exposure. The Permian Ora Formation, Italy, preserves > 1000 m of vertical section through its intra-caldera succession. This provides an excellent opportunity to detail its mineralogical and geochemical architecture and gain understanding of the eruption evolution and insight into the pre-eruptive magma system. Detailed juvenile clast phenocryst and matrix crystal fragment point count and image analysis data, coupled with bulk-rock chemistry and single mineral compositional data, show that the Ora ignimbrite succession is rhyolitic (72.5-77.7% SiO2), crystal-rich (~ 25-57%; average 43%) and has a constant main mineral population (volcanic quartz + sanidine + plagioclase + biotite). Although a seemingly homogeneous ignimbrite succession, important subtle but detectable lateral and vertical variations in modal mineralogy and bulk-rock major and trace elements are identified here. The Ora Formation is comprised of multiple lithofacies, dominated by four densely welded ignimbrite lithofacies. They are crystal-rich, typically lithic-poor (divided into two depo-centres: Southern and Northern, with proximal extra-caldera deposits preserved to the south and north of the system. The Southern and Northern intra-caldera ignimbrite successions are discriminated by variations in total biotite crystal abundance. Detailed mineralogical and chemical data records decreases across the caldera system from south to north in biotite phenocrysts in the groundmass of juvenile clasts (average 12-2%), matrix biotite (average 7.5-2%) and plagioclase crystal fragments (average 18-6%), and total crystal fragment abundance in the matrix (average 47-37%); a biotite compositional change to iron-rich (0.57-0.78 Fe); and bulk-rock element decreases in Fe2O3, MgO, P2O5, Ce, Hf, V, La and Zr, and increases in SiO2, Y and Nb, with TiO2. Together, the

  2. Geochemistry and geochronology of Paleozoic intrusions in the Nalati (Narati) area in western Tianshan, Xinjiang, China: Implications for Paleozoic tectonic evolution

    Science.gov (United States)

    Xu, Xue-Yi; Wang, Hong-Liang; Li, Ping; Chen, Jun-Lu; Ma, Zhong-Ping; Zhu, Tao; Wang, Ning; Dong, Yun-Peng

    2013-08-01

    The Nalati (Narati) area in the Chinese western Tianshan is characterized by abundant Paleozoic intrusions, including granites, diorites and gabbros. They are not only indicators of the interaction between crust and mantle, but also useful clues for tracing the tectonic history of the Tianshan Orogen. Most Early Paleozoic granitoids (biotite monzonitic granites and muscovite granites) of this study are from the Yili Block. The biotite monzonitic granites (mixed-source-derived I-type granites) have a zircon U-Pb age of 497.0 ± 5.9 Ma, indicating the time of the subduction of the Terskey Oceanic crust in the Late Cambrian. The 427.2 ± 5.7 Ma Zircon U-Pb age of the S-type muscovite granites let us interpret that these granites may have been formed during the crust thickening process after the collision between the Yili Block and the Nalati Block. In western Tianshan the Late Paleozoic biotite granites, muscovite granites, quartz diorites, biotite monzonitic granites, granodiorites and alkali granites have respectively a LA-ICPMS zircon U-Pb age of 371.8 ± 6 Ma, 357.2 ± 7.5 Ma, 313.9 ± 2.5 Ma and 296.9 ± 2.4 Ma. The biotite granites display I-type geochemical features and are considered to have been derived from a lower continental crust source. The muscovite granites have a pronounced S-type affinity and are considered to have been formed by the partial melting of thickened continental crust after the collision between the Central Tianshan Belt and the South Tianshan Belt. The quartz-diorites are adakite-like and have an I-type affinity, which are considered to have been formed by partial melting of a delaminated lower crust in a post-orogenic extension setting. The granodiorites also show some typical geochemical features of adakite. Their formation is considered to be related to the lower crustal delamination and the ascending of asthenosphere after the collision event. The alkali granites show an A-type granite affinity. They may have been formed in a within

  3. El plutón de Serrezuela: Evento magmático del Carbonífero en el sector norte de la sierra de Pocho, Córdoba, República Argentina The Serrezuela Pluton: Carboniferous magmatic event in the northerm sector of the Sierra de Pocho, Córdoba, Argentina

    Directory of Open Access Journals (Sweden)

    GM Gómez

    2003-09-01

    . El plutón de Serrezuela de edad carbonífera (321+7,4 Ma y 303+2MA, K/Ar, representa uno de los pulsos magmáticos graníticos mas jóvenes en este sector de las Sierras Pampeanas Orientales. Este cuerpo posiblemente registre el final del ciclo magmático generador de los vecinos batolito de Achala y plutón de La Playa bajo un régimen colisional.The Serrezuela granite is located at the Sierra de Serrezuela in the northern Sierra de Pocho, northwest Córdoba. It is a 16 km2 body, divided into two sectors by metamorphic outcrops. Structurally it is confined by several fractures related to major N-S regional lineaments. The Serrezuela pluton is composed of two main facies: biotite + muscovite monzogranite (BMM, and biotite tourmaline monzogranite (BTM. Both facies are calcalkaline peraluminous, with minor occurrences of a metaluminous biotite aplite. The BTM overlies the BMM facies with sharp contact, in a layer-like occurrence. The Serrezuela granitic stock is characterized by the presence of miarolitic cavities and widespread tourmalinization. A late quartz vein of considerable dimensions intrudes at the pluton boundary. Major element geochemistry shows some dispersion, whereas trace elements show a trend from biotite + muscovite monzogranite toward biotite tourmaline monzogranite. All rocks are strongly differentiated with the biotite + muscovite monzogranite being the least evolved and the most areally extended unit. A liquid fractionation mechanism is proposed for the differentiation and emplacement of the biotite tourmaline monzogranite. Changes in the foliation direction of the country rock, the presence of banded plagioclase and miarolitic cavities, suggests that the Serrezuela pluton had a forced emplacement into the country rocks at shallow crustal depth, along preexisting lineaments. Serrezuela pluton, is a Carboniferous K/Ar age granite (321± 7.4 Ma and 303± 2 Ma. It represents one of the youngest granitic magma pulses of this sector of the Eastern

  4. Garnet ships in a quartzite sea

    Science.gov (United States)

    Rogowitz, Anna; Rice, A. Hugh N.; Grasemann, Bernhard; Huet, Benjamin

    2016-04-01

    During progressive deformation, a strong inclusion in a weaker matrix causes a stress concentration that may result in strain localization, seen in a matrix grain-size reduction. A superb example of this phenomena, but rather more complex, has been observed in north Norwegian Caledonides. A probably subvertical metadolerite dyke has been rotated to lie parallel to the penetrative regional low-angled foliation during the emplacement of the overlying nappe. The metadolerite, now only ~1.4 cm thick and lying between two quartzite layers has been retrogressed to a biotite schist with an assemblage of biotite, titanite, epidote group, garnet and quartz. Garnets are from 0.2 mm to 4 cm in size, subhedral and have two growth zones, with inclusions of predominantly titanite and rare amphibole. The country-rock metasedimentary schists contain staurolite, indicating mid-amphibolite-facies conditions (~550 °C and 6 kbar). During late deformation, some garnets were forced into the quartzite, resulting in the development of pronounced gouges (tectoglyphs), up to 70 mm long, 14 mm wide and 14 mm deep, deepening in the direction of movement. Quartz was pushed up at the sides of the gouges and forms a pronounced bow-wave at the front of the garnets. Where garnets are gouged into the quartzite, intense strain localization occurs. Both in front of and under the garnet, a up to 18 mm wide zone of quartz mylonite developed. The mylonitic foliation curves around the garnet, with a relatively sharp boundary to the adjacent quartzite that preserves an older random fabric. Deformation in the mylonite, which shows a strong crystallographic preferred orientation, seems to have occurred by (1) intense dislocation glide followed by (2) subgrain rotation resulting in an almost foam-like fabric. The grain size of the mylonite (at the quartzite-biotite schist interface) increases with increasing distance behind the present position of the garnets. This observation is consistent with an expected

  5. Geological characteristics of the Moshanhe iron deposit in Shandong%山东磨山河铁矿矿床地质特征

    Institute of Scientific and Technical Information of China (English)

    张朋朋; 张燕挥; 郭强

    2013-01-01

    The Moshanhe iron deposit belongs to a low grade sedimentary metamorphic iron deposit,and its ore-bearing host rock is mainly magnetic biotite schist.The iron ore bodies occur mainly in forms of bands,and lenticular shape.It is characterized with the small size of iron orebody,stable thickness and iron grade,and less harmful components.The main ore textures are granoblastic texture or hypidiomorphic granular texture and flake texture.The main ore mineral is magnetite.The industrial ore type belongs to weak magnetic type iron ore which could be processed.There is no clear boundary between the iron ore bodies and the bottom host rock of the biotite granulite or biotite schist,it needs the analysis results of the samples to determine the boundary.The ore body is an integrated component of Liuhang formation of Taishan Group,and has the same evolution history as Taishan Group.%磨山河铁矿床为磁铁黑云片岩型低品位磁铁矿床,成因属沉积变质型铁矿床.矿体以条带状、透镜状为主;规模较小,厚度、品位变化小,有害成分含量低.矿石主要呈鳞片花岗变晶结构或半自形晶粒结构,片状构造;主要矿石矿物为磁铁矿.矿石工业类型为弱磁性需选铁矿石.矿体与底板黑云变粒岩、黑云片岩界限模糊,需通过样品分析确定.矿体为新太古界泰山岩群柳杭组的组成部分,与泰山岩群的形成与演化过程一致.

  6. Geochemical and isotopic evidence for the petrogenesis and emplacement tectonics of the Serra dos Órgãos batholith in the Ribeira belt, Rio de Janeiro, Brazil

    Science.gov (United States)

    Machado, Rômulo; Philipp, Ruy Paulo; McReath, Ian; Peucat, Jean Jacques

    2016-07-01

    The Serra dos Órgãos batholith in the State of Rio de Janeiro (Brazil) is a NE-SW-trending elongated body that occupies ca. 5000 km2 in plan view. It is a foliated intrusion, especially at its borders and is crosscut by syn-magmatic shear zones, with foliations that are moderately-to steeply-dipping to the northwest and moderately-to shallow-dipping in the center and to the southeast, in a configuration of a large laccolith. It was emplaced between 560 and 570 Ma, during an extensional episode that was part of a series of events that comprise the Brasiliano Orogeny in SE Brazil, and which includes deformation, metamorphism and granite intrusion during the interval between 630 and 480 Ma. The two main rock types in the batholith are biotite-hornblende monzogranite, and biotite leucogranite, with subordinate tonalite, granodiorite, diorite, quartz diorite (enclaves), aplite and pegmatite. Harker-type diagrams help show two rock groups with similar trends of evolution: a dioritic and a granitic. The first one is tholeiitic, whereas the second is calc-alkaline, with medium-to high-K calc-alkaline affinity and metaluminous to slightly peraluminous character. In both groups strong decrease in Al2O3, MgO, FeOT and CaO relative to silica contents are observed, which is compatible with trends of fractional crystallization involving clinopyroxene and/or hornblende, plagioclase, opaque minerals, apatite, microcline and biotite. The Sr and Nd isotopic data suggest recycling of a Paleoproterozoic crust as an important petrological process to generate the batholith rocks. Geothermometry (amphibole composition) and geobarometry (saturation in zircon and apatite) indicate that most of the batholith solidified at mid to lower crustal levels at about 750 °C and between 5 and 5.5 kbar. We consider that Serra dos Órgãos crustal protoliths underwent melting caused by the interaction with hotter mafic magma at the base of the crust. These two magmas, with distinct initial

  7. Permo-Carboniferous granitoids with Jurassic high temperature metamorphism in Central Pontides, Northern Turkey

    Science.gov (United States)

    Gücer, Mehmet Ali; Arslan, Mehmet; Sherlock, Sarah; Heaman, Larry M.

    2016-04-01

    In the northern part of the Central Pontides (N Turkey) there are different metamorphic rocks exposed, notably the Devrekani metamorphic rocks. Here, upper amphibolite-lower granulite facies metamorphic rocks contain predominantly paragneiss, orthogneiss and metacarbonate, and to a lesser extent, amphibolite and quartzite, with cross-cutting aplite, pegmatite and granite veins. This is the first report of these rocks and includes new data on the petrochemistry, geochronology and metamorphic evolution of the Devrekani orthogneisses from the Central Pontides. The orthogneisses show five different mineral parageneses with the characteristic mineral assemblage quartz + K-feldspar + plagioclase + biotite ± hornblende ± opaque (± ilmenite and ± magnetite), and accessory minerals (zircon, sphene and apatite). These metamorphic rocks exhibit generally granoblastic, lepidogranoblastic and nematolepidogranoblastic with locally migmatitic and relic micrographic textures. They have well-developed centimeter-spaced gneissic banding and display gneissose structure with symmetric, asymmetric and irregular folds. The petrographic features, mineralogical assemblages and weak migmatization reflect high temperature conditions. Thermometric calculations in the orthogneisses indicate metamorphic temperatures reached 744 ± 33 °C. Field relations, petrography and petrochemistry suggest that the orthogneisses have predominantly granodioritic and some granitic protoliths, that show features of I-type, medium to high-potassic calc-alkaline volcanic arc granitoids. The orthogneisses have high contents of LILEs and low contents of HFSEs with negative Nb and Ti anomalies, which are typical of subduction-related magmas. The orthogneisses also show significant LREE enrichment relative to HREE with negative Eu anomalies (EuN/Eu* = 0.33-1.07) with LaN/LuN = 6.98-20.47 values. Based on U-Pb zircon dating data, the protoliths are related to Permo-Carboniferous (316-252 Ma) magmatism. It is

  8. Metamorphic petrology of Olkiluoto

    Energy Technology Data Exchange (ETDEWEB)

    Tuisku, P.; Kaerki, A. (Kivitieto Oy, Oulu (Finland))

    2010-06-15

    The bedrock of Olkiluoto consists mostly of pelitic migmatites, and lesser amounts of biotite and hornblende gneisses, granite gneisses and granodiorite gneisses. The metapelites underwent partial dehydration melting through decomposition of biotite, sillimanite, plagioclase and quartz during the peak of regional metamorphism, producing the migmatites. Simple model systems were used to estimate the conditions of melting in metapelites and in quartzofeldspathic and granitic rocks. Pressure and temperature conditions of metamorphism in Olkiluoto have also been calculated by TWQ-thermobarometer and predicted from mineral assemblages of different rock types in the area. Regional metamorphism of Olkiluoto culminated with a voluminous migmatization of pelitic gneisses, in the temperature exceeding 660 deg C and relatively low pressure of about 3.5 - 4 kbar. The temperature may have risen up to approx 700 deg C producing granitic melt, which later crystallized to leucosomes. The mineral assemblages produced during the peak of regional metamorphism overprint the earlier S2 foliation. Granitic leucosomes associated with the culmination of the metamorphism were deformed by D3 deformation. Accordingly, the peak of metamorphism took place between D2 and D3 deformation phases. Muscovite-bearing shear bands of some granite pegmatites indicate that D3 deformation took place during subsequent cooling. Because granodiorite gneisses, having an age of about 1.86 Ga, are deformed by D2 deformation, the peak of regional metamorphism may be dated somewhere between 1.86 and 1.82 Ga, the latter being the minimum age of granite deformed by D3 deformation. The culmination of metamorphism is seen also in the mineral assemblages of more resistant rocks as biotite gneisses, hornblende gneisses and granodiorite gneisses. The cooling phase took place in low pressure, which is seen from some retrograde reaction products as andalusite, chlorite and muscovite replacing cordierite. Calculated

  9. Genetic Mechanism of Mineral Inclusions in Zircons from the Khondalite Series, Southeastern Inner Mongolia

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The early Precambrian khondalite series is widely distributed in the Jining-Zhuozi-Fengzhen- Liangcheng area, southeastern Inner Mongolia. The khondalite series mainly consists of sillimanite garnet potash feldspar (or two-feldspar) gneiss and garnet biotite plagioclase gneiss. These gneissic rocks have commonly experienced granulite-facies metamorphism. In zircons separated from sillimanite garnet potash feldspar gneisses, many mineral inclusions, including Sil, Grt, Ky, Kfs, Qtz and Ap, have been identified by the Laser Raman spectroscopy. Generally, prograde metamorphic mineral inclusion assemblages such as Ky + Kfs + Qtz + Ap and Ky + Grt + Kfs + Qtz are preserved in the core of zircon, while peak granulite-facies metamorphic minerals including Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap are identified in the mantle and rim of the same zircon. However, in some zircons are only preserved the peak metamorphic minerals such as Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap from core to rim, and in others are inherited the primary cores with minor mineral inclusions of Kfs + Qtz, with peak metamorphic mineral inclusions around the inherited cores. These data indicate that the mineral assemblage evolution of sillimanite garnet potash feldspar gneisses in the study are did experience a polymorphic transformation of kyanite to sillimanite. In garnet biotite plagioclase gneisses, secondary electron microscopic images reveal that most zircons display distinct zoning textures, which comprise cores and rims, each with distinctive inclusion assemblages. The inherited mineral inclusions, mainly consisting of Kfs + Pl + Qtz, Kfs + Qtz and Kfs + Qtz + Ap, are preserved in the primary cores, while peak granulite-facies mineral asemblages, including Grt + Bt + Pl + Qtz + Ap, Grt + Bt + Pl + Qtz and Grt + Bt + Pl + Qtz + Rt, are identified on the rims. The occurrence of peak metamorphic mineral inclusions in zircons indicates that these gneissic rocks, including

  10. Evolution of high-pressure mafic granulites and pelitic gneisses from NE Madagascar: Tectonic implications

    Science.gov (United States)

    Ishwar-Kumar, C.; Sajeev, K.; Windley, B. F.; Kusky, T. M.; Feng, P.; Ratheesh-Kumar, R. T.; Huang, Y.; Zhang, Y.; Jiang, X.; Razakamanana, T.; Yagi, K.; Itaya, T.

    2015-11-01

    The occurrence of high-pressure mafic-ultramafic bodies within major shear zones is one of the indicators of paleo-subduction. In mafic granulites of the Andriamena complex (north-eastern Madagascar) we document unusual textures including garnet-clinopyroxene-quartz coronas that formed after the breakdown of orthopyroxene-plagioclase-ilmenite. Textural evidence and isochemical phase diagram calculations in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2 system indicate a pressure-temperature (P-T) evolution from an isothermal (780 °C) pressure up to c. 24 kbar to decompression and cooling. Such a P-T trajectory is typically attained in a subduction zone setting where a gabbroic/ultramafic complex is subducted and later exhumed to the present crustal level during oceanic closure and final continental collision. The present results suggest that the presence of such deeply subducted rocks of the Andriamena complex is related to formation of the Betsimisaraka suture. LA-ICPMS U-Pb zircon dating of pelitic gneisses from the Betsimisaraka suture yields low Th/U ratios and protolith ages ranging from 2535 to 2625 Ma. A granitic gneiss from the Alaotra complex yields a zircon crystallization age of ca. 818 Ma and Th/U ratios vary from 1.08 to 2.09. K-Ar dating of muscovite and biotite from biotite-kyanite-sillimanite gneiss and garnet-biotite gneiss yields age of 486 ± 9 Ma and 459 ± 9 Ma respectively. We have estimated regional crustal thicknesses in NE Madagascar using a flexural inversion technique, which indicates the presence of an anomalously thick crust (c. 43 km) beneath the Antananarivo block. This result is consistent with the present concept that subduction beneath the Antananarivo block resulted in a more competent and thicker crust. The textural data, thermodynamic model, and geophysical evidence together provide a new insight to the subduction history, crustal thickening and evolution of the high-pressure Andriamena complex and its link to the terminal

  11. Petrography, Geochemistry and Rb-Sr geochronology of the basement granitoids from Umthongkut area, West Khasi Hills district, Meghalaya, India: implications on petrogenesis and uranium mineralization

    International Nuclear Information System (INIS)

    The basement granitoids from Umthongkut, West Khasi Hills district, Meghalaya is exposed in a very small area (1.5 km x 0.5 km) and unconformably overlain by Mahadek sandstone of upper Cretaceous age and successively followed by rocks of Tertiary age. Megascopically, granitoids are leucocratic, mesocratic to mild melanocratic and differ in texture and mineral abundance without any definite contact relation in field. The leucocratic granitoid is medium-grained, designated as granite (syenogranite and monzogranite) with appreciable content of biotite and garnet and has peraluminous to mild metaluminous character (mol. Al2O3/mol. CaO+Na2O+K2O = 0.9-1.17). However, mesocratic granitoid is relatively fine-grained, identified as quartz monzonite with abundant biotite, minor hornblende and opaque like magnetite, ilmenite, anatase, pyrite and chalcopyrite and metaluminous to mild peraluminous (mol. A/CNK = 0.76-1.02) in nature. The presence of characteristic minerals and textural replacement features point towards S-type signature for granite and I-type for quartz monzonite. On the other hand, mixed S and I-type characters are observed in geochemical plot of SiO2 vs. A/CNK. The coexistence of granite and quartz monzonite with former being more evolved, S-type signature and presence of garnet with biotite suggests that the granite appears to be generated from melting of lower crustal source of monzonitic composition. The Rb-Sr dating is also attempted and the errorchron age of 1130±53 with low initial 87Sr/86Sr ratio of 0.7063±0.001 Ma appears to be the emplacement age for these coexisting phases of granitoid. Considering the Meghalaya plateau being northeastern extension of Chhotanagpur granite-gneiss complex (CGGC), the calculated age for the studied samples corresponds to the 1200-1000 Ma. which is defined as fourth tectono-magmatic thermal event of CGGc. Interestingly, these granitoids are considered as the probable source for uranium in the sandstones of Mahadek

  12. 广西DC矿田成矿作用和物质成分研究

    Institute of Scientific and Technical Information of China (English)

    章振根; 李锡林

    1981-01-01

    DC, a multi-metal ore field, is an important and well known producer of tin in China. Besides tin, also mined are zinc, lead, antimony, copper, arsenic, tungsten,mercury, silver and many other metals most of the deposits in this region occur in Devonian limestones and siliceous shales. The ore deposits in this field are predominated by cassiterite sulphide type. As to the origin of those deposits, they seem closely related to biotite granite. The oreforming material is mainly derived from magmatie rocks, and part of it may come from the host rocks. The appearance of horizontal zoning of ore deposits in this field is extremely distinct, with LXG biotite granite as the core. Found in the magmatie rocks is the molybdenum mineralization. From the biotite granite outwards there dlsplays such an occurring sequence as the following: copper (zinc) skarn ore deposits, seheelite ore deposits, wolframite ore deposits, eassiterite sulphide ore deposits, lead-zinc (antimony)ore deposits and mercury or arsenic ore deposits. In this region the mineralizingtemperature zoning is also distinguishable, basically in agreement with the horizontal zoning of ore deposits. In other words, the formation temaperature of ore deposits occurring around the granite is higher than that farther away from the granite. The following mineralization periods and stages can be divided: the first period,ineluding skarn sub-stage, eassiterite-quartz sub-stage, cassiterite-sulphide sub-stage,eassiterite-calcite sub-stage; the second period, including ferrosphalerite (galena)-franckeite sub-stage, jamesenite-boulangerite sub-stage; and the third period, including pyrite-calcite sub-stage. The characters of the material composition are as follows: ore minerals are characterized by great variety, perfect crystallinity, large grain-size and abundant sulfosalts. More than 90 species of minerals have been identified. What is more interesting is that lead and antimony in some of the cassitierite-sulfide deposits

  13. Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

    Science.gov (United States)

    Rye, R.O.; Schuiling, R.D.; Rye, D.M.; Jansen, J.B.H.

    1976-01-01

    At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700??C. The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The ??18O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated ??18OH2O values of the metamorphic fluids in the schist-rich zones decrease from about 15??? in the lower grades to an average of about 8.5??? in the migmatite. The ??D values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated ??DH2O values for the metamorphic fluid decrease from -5??? in the glaucophane zone to an average of about -70??? in the migmatite. The ??D values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend. The??18O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The ??D values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism. Detailed data on 20 marble units show systematic variations of ??18O values which depend upon metamorphic grade. Below the 540??C isograd very steep ??18O gradients at the margins and large ??18O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540??C isograd lower ??18O values occur in

  14. The spatial variation of initial 87Sr/86Sr ratios in the Toki granite, Central Japan. Implications for the intrusion and cooling processes of a granitic pluton

    International Nuclear Information System (INIS)

    The spatial variation in initial 87Sr/ 86Sr ratios (SrI) in the Toki granite, Central Japan, shows heterogeneity ranging from 0.708942 to 0.710069, which provides information on the intrusion and cooling processes of plutons. The Toki granite has three mineralogy-based rock facies: muscovite-biotite granite (MBG), hornblende-biotite granite (HBG) and biotite granite (BG). Large SrI values were found to be distributed at the western margin (west MBG) and the lithologically central region (central BG), while small SrI values were found at the northeast margin (northeast MBG). Regions with high and low Sr concentrations were also found in the Toki granite. In the Sr-rich samples, SrI (0.708942-0.709789) increases with 100/Sr (0.7-1.5). This geochemical trend extends towards the country sedimentary rocks of the Mino Terrane, which can be interpreted to result from assimilation and fractional crystallization (AFC) between the original granitic magma and the Mino sedimentary rocks. The SrI values in the Sr-rich regions show a correlation with the Alumina Saturation Index (ASI). In particular, the west MBG, with large SrI values, is classified as a peraluminous granitoid with large ASI, suggesting that the western margin of the pluton was strongly affected by assimilation during the intrusion process. The Sr-poor samples are present both in the central BG, with large SrI values, and in the northeast MBG, with small SrI values. The Sr-poor samples have small ASI and large differentiation indices, indicating that the central BG and the northeast MBG were generated either by different AFC process with different amounts of contaminants or by the intrusion and fractionation of different source magma with different SrI values. Overall, the geochemical spatial variations found in the Toki granite can be explained by various degrees of assimilation and fractional crystallization in the magma chamber and/or multi-stage intrusions with different degrees of crystallization of plural

  15. Petrogenesis of Garnet-bearing Rocks in the Grandfather Mountain Window, Blue Ridge Province, Western North Carolina

    Science.gov (United States)

    Frushour, A. M.; Abbott, R. N.

    2014-12-01

    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.

  16. Metamorphism and gold mineralization of the Kenticha Katawicha area: Adola belt, southern Ethiopia

    Science.gov (United States)

    Tsige, Lulu

    2006-05-01

    I present geological and mineral chemistry results aiming at understanding the relationship between metamorphism and gold mineralization in the N-trending Neoproterozoic Kenticha-Katawicha area in the Adola belt of southern Ethiopia. The Kenticha-Katawicha area comprises low-grade metamorphic rocks including pelitic schists, marble, graphite schists and Fe-Mn quartzites (Kenticha marine metasedimentary rocks) and serpentinites and talc-tremolite-chlorite schists with podiform chromites (Kenticha ophiolite). Lenses of high-grade amphibolite schist are also locally present within the Kenticha-Katawicha area. These rocks are sandwiched between high-grade para- and ortho-gneisses, migmatites, schists and amphibolites. Post-orogenic granites intrude the metamorphic sequences. Mineral assemblages and textural data obtained from the high-grade rocks indicate that the dominant metamorphic condition is of upper amphibolite facies. Garnet-biotite (garnet-core-matrix-biotite) and amphibole-plagioclase geothermometry gave estimates for peak metamorphic temperatures of 630-650 °C and pressure of 7 kbar for the high-grade rocks. On the other hand, the low-grade rocks recrystallized in the greenschist facies conditions. The estimated peak T- P values for the high-grade rocks suggest a burial to ˜25 km depth and a clockwise P- T path is deduced from mineral thermometry and the textural and paragenetic relations. This combined with the geochemistry of the magmatic rocks and clockwise P- T is consistent with a collision setting in which rocks of the calc-alkaline, volcanic-arc, and oceanic fragments are assembled. In the study area, gold occurs in quartz veins and veinlets in lenses of biotite schists within ultramafic rocks that are confined to shear zones. Fluid inclusion studies of gold quartz veins and veinlets indicate a H 2O- and CO 2-rich fluid with low salinity (<5 wt% NaCl equivalent). The gold mineralization in the area is post-peak regional metamorphism and is

  17. Sources of granite magmatism in the Embu Terrane (Ribeira Belt, Brazil): Neoproterozoic crust recycling constrained by elemental and isotope (Sr-Nd-Pb) geochemistry

    Science.gov (United States)

    Alves, Adriana; Janasi, Valdecir de Assis; Campos Neto, Mario da Costa

    2016-07-01

    Whole rock elemental and Sr-Nd isotope geochemistry and in situ K-feldspar Pb isotope geochemistry were used to identify the sources involved in the genesis of Neoproterozoic granites from the Embu Terrane, Ribeira Belt, SE Brazil. Granite magmatism spanned over 200 Ma (810-580 Ma), and is dominated by crust-derived relatively low-T (850-750 °C, zircon saturation) biotite granites to biotite-muscovite granites. Two Cryogenian plutons show the least negative εNdt (-8 to -10) and highest mg# (30-40) of the whole set. Their compositions are strongly contrasted, implying distinct sources for the peraluminous (ASI ∼ 1.2) ∼660 Ma Serra do Quebra-Cangalha batholith (metasedimentary rocks from relatively young upper crust with high Rb/Sr and low Th/U) and the metaluminous (ASI = 0.96-1.00) ∼ 630 Ma Santa Catarina Granite. Although not typical, the geochemical signature of these granites may reflect a continental margin arc environment, and they could be products of a prolonged period of oceanic plate consumption started at ∼810 Ma. The predominant Ediacaran (595-580 Ma) plutons have a spread of compositions from biotite granites with SiO2 as low as ∼65% (e.g., Itapeti, Mauá, Sabaúna and Lagoinha granites) to fractionated muscovite granites (Mogi das Cruzes, Santa Branca and Guacuri granites; up to ∼75% SiO2). εNdT are characteristically negative (-12 to -18), with corresponding Nd TDM indicating sources with Paleoproterozoic mean crustal ages (2.0-2.5 Ga). The Guacuri and Santa Branca muscovite granites have the more negative εNdt, highest 87Sr/86Srt (0.714-0.717) and lowest 208Pb/206Pb and 207Pb/206Pb, consistent with an old metasedimentary source with low time-integrated Rb/Sr. However, a positive Nd-Sr isotope correlation is suggested by data from the other granites, and would be consistent with mixing between an older source predominant in the Mauá granite and a younger, high Rb/Sr source that is more abundant in the Lagoinha granite sample. The

  18. Studies of microstructures of deformed charnockitic rocks in Telsiai deformation zone, Lithuania

    Science.gov (United States)

    Vejelyte, Irma

    2010-05-01

    The Telsiai Deformation Zone (TDZ), a regional scale Precambrian deformation zone in the crystalline basement of Lithuania, transects the WLGD in the E-W direction and is approximately 15-20 km wide as mirrored by a belt of gravity and magnetic lows. As indicated by petrological and geophysical data the TDZ crosscuts a 1.82 Ga charnockitic pluton in a ductile manner. In turn, the TDZ appears to have been intruded by or accommodated a 1.46 Ga granitoid intrusion, defining at least its age in-between of these two magmatic events. The mesoanalyses and microanalyses of drillcores have been carried out on augen mylonite and ultramylonite, which were formed at upper amphibolite facies. The temperature during the deformation was 650-750 C° at pressure between 3.0 and 4.7 kbar. The deformed charnockites have a prominent foliation marked mainly by feldspar, biotite, quartz, orthopyroxene, garnet and ± clinopyroxene. Porphyroclasts of plagioclase are elongated and banded. They are partly recrystallized to fine-grained polygonal aggregates as a result of high temperature deformation. In places, plagioclase has been truncated by plagioclase-rich microshears. Quartz grains are in three manners: large old grains with deeply indented boundaries and undulate extinction; medium polygonal grains and ribbons grains. Large biotite grains are locally kinked, some of them have been partly neocrystallized to much smaller new grains of biotite parallel to the foliation. Garnet crystals are elongated and oriented to the foliation. Individual grains of them in the highest strain areas have been recrystallized to many small garnet grains. Large crystals of orthopyroxene are deformed and elongated, on their sheared rims tails of fine grained orthopyroxene and clinopyroxene have been formed. The subgrain rotation, grain-boundary migration recrystallization and recovery processes predominate in all minerals. Near residual plagioclase also are visible myrmekites. They formed along those sides

  19. The Lost Gardar Intrusion: Critical Metal Exploration at the Paatusoq Syenite Complex, South East Greenland

    Science.gov (United States)

    Stacey, Mark; Finch, Adrian; Hughes, Josh; Christiansen, Ole

    2014-05-01

    Regional mapping by GEUS (Garde, 1998) of the Paatusoq region, South-East Greenland, defined two intrusive centres, the Paatusoq Gabbro (~23km2) and the Paatusoq Syenite (~240km2). These intruded the lithospherically weak boundary between Ketilidian meta-sedimentary rock to the East and to the West the Pelite-Psammite zone sediments unconformably overlying the Julianehåb batholith. Following the discovery of high rare earth element (REE=La-Yb+Y) anomalies in stream sediments (Steenfeldt, 2012) in the Paatusoq region, Paatusoq was the target of exploration by Nuna Minerals A/S in June 2013. The objective was to provide an assessment of the critical metal potential of the region. Exploration involved helicopter reconnaissance and sampling. The Paatusoq syenite (1144±1 Ma) was recognised by Garde (2002) as part of the Gardar Alkaline Igneous Province (1300-1140 Ma). Gardar centres are predominantly found on the South-Western coast and represent products of magmatism associated with repeated Mesoproterozoic rifting. Globally significant critical metal deposits are associated with the province including Motzfeldt (Ta-Nb) and Ilímaussaq (REE-Zr-Nb). Gardar intrusions with significant critical metal mineralisation often record interaction with late-stage fluorine-bearing fluids.Analysis integrated petrography and geochemistry, supplemented by two indicators of fluid interaction with the syenite; the cathodoluminescence textures of feldspars and the halogen content of biotite. The Paatusoq Gabbro showed heterogeneous primary layering and pegmatite schlieren to the West against the syenite. A Gardar Lamprophyre dyke cuts the Gabbro. Petrology showed; subhedral olivine, labradorite, biotite and quartz. Incompatible element geochemistry showed the gabbro has a Zr/Nb ratio >15 consistent with a Ketilidian affinity and the lamprophyre has a Zr/Nb ratio ~5, comparable with other Gardar lamprophyres. The Paatusoq syenite showed lithological variation from quartz

  20. P-T path fluid evolution in the Gross Spitzkoppe granite stock, Namibia

    Directory of Open Access Journals (Sweden)

    Stephen Frindt

    2002-01-01

    Full Text Available The Gross Spitzkoppe granite stock (GSS is a zoned 30 km^2 epizonal intrusion that consists of three main granites: 1 medium-grained biotite granite (marginal, 2 a coarse-grained biotite granite, and 3 a central, porphyritic granite. The stock contains pegmatites as banded marginal stockscheiders and isolated pockets composed of large alkali feldspar and quartz, dark mica, interstitial fluorite, and euhedral topaz and beryl crystals. In the porphyritic granite there are local wolframite-bearing greisens and hydrothermal fluorite and topaz-rich veins.Fluid inclusion studies were conducted on: 1 topaz and quartz crystals from the marginal stockscheider; 2 quartz, topaz, fluorite and beryl crystals from isolated pegmatites; 3 topaz from a miarolitic pegmatite; 4 beryl and quartz veins from greisenized porphyritic granite; and 5 fluorite from a late fluorite vein inthe coarse-grained biotite granite. Preliminary data indicate the presence of three compositionally distinct primary and pseudosecondary inclusion types that are of late magmatic-hydrothermal origin.Type 1. Low salinity (0–10 eq. wt% NaCl H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 550˚C. These inclusions are from quartz, topaz and beryl. Inclusions in fluorite from the fluorite vein homogenize at ~170˚C and have a salinity of ca. 1–2 eq. wt% NaCl.Type 2. Saline (25–30 eq. wt% NaCl halite-bearing H2O (± CO2 inclusions that homogenize to the liquid phase in the temperature range of 300 to 400˚C. These inclusions are from quartz.Type 3. Low salinity (0–3 eq. wt% NaCl H2O-CO2 inclusions that homogenize to vapor phase in the temperature range of 330 to 550˚C. These inclusions are from quartz and topaz.Hydrothermal fluids from greisen minerals are represented by type 1 and type 2 H2O inclusions. They are predominantly of low salinity (~8 eq. wt% NaCl and homogenize to the liquid phase in the temperature range of 300 to 500

  1. Petrogenesis, geochronology, and tectonic significance of granitoids in the Tongshan intrusion, Anhui Province, Middle-Lower Yangtze River Valley, eastern China

    Science.gov (United States)

    Zhang, Zhi-Yu; Du, Yang-Song; Teng, Chuan-Yao; Zhang, Jing; Pang, Zhen-Shan

    2014-01-01

    The Tongshan copper deposit in Anhui Province is a typical mid-sized skarn and porphyry type deposit in the Anqing-Guichi district along the Middle-Lower Yangtze River Valley, eastern China. The Tongshan intrusion is closely related to this mineralization. The intrusion mainly comprises rocks that are quartz diorite porphyry, quartz monzonite porphyry, and granodiorite porphyry. Plagioclase in these rocks is mostly andesine (An = 31.0-42.9), along with minor oligoclase. Biotite is magnesium-rich [Mg/(Mg + Fe) = 0.52-0.67] and aluminum-poor (Al2O3 = 12.32-14.09 wt.%), and can be classified as magnesio-biotite. Hornblende is TiO2-poor ( 0.60], and is magnesio-hornblende or edenite. The SHRIMP zircon U-Pb age of the quartz monzonite porphyry is 145.1 ± 1.2 Ma, which corresponds to the middle Yanshanian period. Whole-rock geochemical results show that the rocks are silica-rich (SiO2 = 60.23-66.23 wt.%) and alkali-rich (K2O + Na2O = 4.97-8.72 wt.%), and low in calcium (CaO = 2.61-5.66 wt.%). Trace element results show enrichments in large ion lithophile element (e.g., K, Rb, and Ba) and depletions in some high field strength elements (e.g., Nb, Ta, P, and Ti). The total rare earth element (REE) content of the rocks is low (ΣREE 10] and small positive Eu anomalies (average δEu = 1.16). These mineralogical, geochronological, and geochemical results show that the intrusion has a mixed crust-mantle source. The Tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust. Hornblende thermobarometry yielded magmatic crystallization temperatures of 652-788 °C and an average crystallization pressure of 1.4 kbar, which corresponds to a depth of approx. 4.7 km. Biotite thermobarometry yielded similar temperatures and lower pressures of 735-775 °C and 0.6 kbar (depth 2.1 km), respectively. The parental magma had a high oxygen fugacity and was

  2. Petrology and radiogeology of the Stripa pluton

    Energy Technology Data Exchange (ETDEWEB)

    Wollenberg, Harold; Flexser, Steve; Andersson, Lennart

    1980-12-01

    To better define the character of the rock encompassing the thermomechanical and hydrological experiments at the Stripa mine in central Sweden, and to help determine the size of the Stripa pluton, detailed studies were conducted of the petrology and radiogeology of the quartz monzonite and adjacent rocks. Petrologic studies emphasized optical petrography, with supplementary X-ray diffraction, X-ray fluorescence and microprobe analyses. Radiogeologic investigations were based primarily on surface and underground gamma-ray spectrometric measurements of uranium, thorium and potassium, supplemented by laboratory gamma spectrometric analyses and fission-track radiographic determinations of the locations and abundance of uranium in the rock matrix. Both the quartz monzonite and the metavolcanic leptite which it intruded are strongly fractured. Two stages of fracture filling are evident; an earlier stage encompassing quartz, sericite, feldspar, epidote, and chlorite, and a later stage dominated by carbonate minerals. The Stripa quartz monzonite is chemically and mineralogically distinct from other plutons in the region. Muscovite is the predominant mica in the quartz monzonite; biotite has been altered to chlorite, hornblende is absent, and accessory minerals are scarce. In contrast, in other plutons in the Stripa region biotite and hornblende are prominent mafic minerals and accessory minerals are abundant. The Stripa quartz monzonite is also considerably more radioactive than the leptite and other plutons in the region. Uranium and thorium abundances are both- 30 ppm, considerably higher than in "normal" granitic rocks where the thorium-to-uranium ratio generally exceeds 2. Potassium-argon dating of muscovite from the Stripa quartz monzonite indicates that this rock may be older, at 1691 million years than granitic rock of the neighboring Gusselby and Kloten massifs, whose ages, based on K-Ar dating of biotite, are respectively 1604 and 1640 m.y. Heat flow and heat

  3. K-Ar geochronology of basement rocks on the northern flank of the Huancabama deflection, Ecuador

    Science.gov (United States)

    Feininger, Tomas; Silberman, M.L.

    1982-01-01

    The Huancabamba deflection, a major Andean orocline located at the Ecuador-Peru border, constitutes an important geologic boundary on the Pacific coast of South America. Crust to the north of the deflection is oceanic and the basement is composed of basic igneous rocks of Cretaceous age, whereas crust to the south is continental and felsic rocks of Precambrian to Cretaceous age make up the basement. The northern flank of the Huancabamba Deflection in El Oro Province, Ecuador, is underlain by Precambrian polymetamorphic basic rocks of the Piedras Group; shale, siltstone, sandstone, and their metamorphosed equivalents in the Tahuin Group (in part of Devonian age); concordant syntectonic granitic rocks; quartz diorite and alaskite of the Maroabeli pluton; a protrusion of serpentinized harzburgite that contains a large inclusion of blueschist-facies metamorphic rocks, the Raspas Formation, and metamorphic rocks north of the La Palma fault. Biotite from gneiss of the Tahuin Group yields a Late Triassic K-Ar age (210 ? 8 m.y.). This is interpreted as an uplift age and is consistent with a regional metamorphism of Paleozoic age. A nearby sample from the Piedras Group that yielded a hornblende K-Ar age of 196 ? 8 m.y. was affected by the same metamorphic event. Biotite from quartz diorite of the mesozonal Maroabeli pluton yields a Late Triassic age (214 ? 6 m.y.) which is interpreted as an uplift age which may be only slightly younger than the age of magmatic crystallization. Emplacement of the pluton may postdate regional metamorphism of the Tahuin Group. Phengite from politic schist of the Raspas Formation yields an Early Cretaceous K-Ar age (132 ? 5 m.y.). This age is believed to date the isostatic rise of the encasing serpentinized harzburgite as movement along a subjacent subduction zone ceased, and it is synchronous with the age of the youngest lavas of a coeval volcanic arc in eastern Ecuador. A Late Cretaceous K-Ar age (74.4 ? 1.1 m.y.) from hornblende in

  4. The distribution of rare earth elements in tropical granitic soil: a case study from Malaysia

    Science.gov (United States)

    Mohamad, Hamzah; Ghani Rafek, Abdul

    A total of 93 samples of rock, altered soil representing various weathering grades from an ideal granite weathering profile exposed at a road cut along the Kuala Lumpur-Karak highway, Peninsular Malaysia, were studied. The fresh, unaltered parent rock is petrographically distinguished into two types: (1) coarse grained porphyritic biotite-muscovite granite, and (2) medium grained biotite-muscovite granite. The rock has undergone some degree of brittle deformation. A weathering index map based on the procedures suggested by Ibrahim Komoo et al. Warta Geologi17(3), 105-109 (1991) shows the spatial distribution of unaltered to slightly altered rocks (index 2-4), weathered rocks (5-8) and residual soil (9 and 10) for the profile under study. For each sample, 11 major elements were determined using X-ray fluorescence technique (XRF) and nine rare earth elements, La, Ce, Nd, Sm, Eu, Tb, Dy, Yb and Lu, by the instrumental neutron activation analysis (INAA). All REEs decrease with increasing weathering grade, suggesting a depletion of the REEs due to weathering. The depletion rate is variable, the fastest being Sm and La. A Masuda-Coryell diagram for the three groups of samples, that is (1) fresh to slightly weathered rocks, (2) moderately to highly weathered rocks, and (3) residual soils, shows three curves with a similar pattern of negative Eu anomalies. The concentration of elements is in the order 1>2>3, suggesting strongly that the REEs diminish gradually in the course of the weathering. A rock-soil interface has been recognised to exist at weathering index 4. It is believed that at this interface, most REEs leave their primary carriers which undergo rapid breakdown, most probably plagioclase, biotite and hornblende and possibly ilmenite and apatite, into weathering solution, together with Fe 2+, Ca 2+, K +, Mn 2+ and Mg 2+. Anomalously low concentration of REEs in index 4 material supports this idea. The leached-out REEs are temporarily incorporated into newly formed

  5. Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania

    Science.gov (United States)

    Bonin, Bernard; Tatu, Mihai

    2016-01-01

    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).

  6. EMSP Project 70070: Reactivity of Primary Soil Minerals and Secondary Precipitates Beneath Leaking Hanford Waste Tanks - Final Report

    International Nuclear Information System (INIS)

    Since the late 1950s, leaks from 67 single-shell tanks at the Hanford Site have released about 1 million curies to the underlying sediments. The radioactive material was contained in water-based solutions generally characterized as having high pH values (basic solutions), high nitrate and nitrite concentrations, and high aluminum concentrations. The solutions were also hot, in some cases at or near boiling, as well as complex and highly variable in composition reflecting solutions obtained from multiple methods of reprocessing spent nuclear fuel. In order to understand the observed and probable distribution of radionuclides in the ground at Hanford, major reactions that likely occurred between the leaked fluids and the sediment minerals were investigated in laboratory experiments simulating environmental conditions. Reactions involving the dissolution of quartz and biotite and the simultaneous formation of new minerals were quantified at controlled pH values and temperature. Result s show that the dissolution of quartz and formation of new zeolite-like minerals could have altered the flow path of ground water and contaminant plumes and provided an uptake mechanism for positively-charged soluble radionuclides, such as cesium. The dissolution of biotite, a layered-iron-aluminum-silicate mineral, provided iron in a reduced form that could have reacted with negatively-charged soluble chromium, a toxic component of the wastes, to cause its reduction and precipitation as a new reduced-chromium mineral. The quantity of iron released in the experiments is sufficient to explain observations of reductions in dissolved chromium concentration in a plume beneath one Hanford tank. Fundamental data obtained in the project are the rates of the reactions at variable temperatures and pHs. Fundamental data were also obtained on aspects of the surface reactivity of clay or layered-silicate minerals, a small proportion of the total mass of the sediment minerals, but a large proportion

  7. El Ventorrillo, a paleostructure of Popocatépetl volcano: insights from geochronology and geochemistry

    Science.gov (United States)

    Sosa-Ceballos, G.; Macías, J. L.; García-Tenorio, F.; Layer, P.; Schaaf, P.; Solís-Pichardo, G.; Arce, J. L.

    2015-10-01

    Volcán Popocatépetl (México) was constructed over the remains of a volcanic paleostructure. Based on fieldwork, 40Ar/39Ar dating, U-Pb dating, and geochemistry, we have determined the age, chemistry, and location of this paleostructure and named it El Ventorrillo. Most remnants of El Ventorrillo are covered by deposits from subsequent activity of Popocatépetl, except for the El Abanico scarp and the Barranca de Nexpayantla, where the stratigraphy of El Ventorrillo eruptive products can be investigated. Inception of volcanism at El Ventorrillo occurred at 331 ± 10 ka with emission of the Nexpayantla andesitic lavas, and continued with extrusion of the Yoloxochitl (267 ± 31 ka) and microwave (227 ± 6 ka) domes. Intrusion of dikes occurred at 298 ± 94 and 230 ± 3 ka. Activity at El Ventorrillo continued with the emission of lavas that built the El Abanico scarp (193 ± 29 to 96 ± 8 ka) and continued until the Tutti Frutti eruption destroyed the cone 14.1 kyr ago. El Ventorrillo magmas produced rocks divided into two mineralogical groups. The first group contains biotite-amphibole-rich rocks and the second group consists of biotite-amphibole-free lavas. The rocks that contain biotite and amphibole are older than 198 ± 13 ka, whereas the rocks with no hydrous phases are younger than 227 ± 6 ka and contain skarn and granodiorite xenoliths. We interpret the change to an anhydrous mineral assemblage and the occurrence of skarn and granodiorite xenoliths as evidence for the formation of a new, shallower reservoir. A granodiorite xenolith was chosen for 40Ar/39Ar dating and U-Pb zircon analyses. The U-Pb method yielded an age of 540 ± 110 ka and the 40Ar/39Ar an age of 109 ± 24 ka. These ages are interpreted to indicate granodiorite crystallization (540 ± 110 ka), which metamorphosed the calcareous basement beneath Popocatépetl into skarn and an influx of magma (109 ± 24 ka) that reheated the granodiorite. Major and trace elements, Sr, Nd, and Pb isotopic

  8. Granitoids of the Dry Valleys area, southern Victoria Land : geochemistry and evolution along the early Paleozoic Antarctic Craton margin

    International Nuclear Information System (INIS)

    Field relationships and geochemistry indicate granitoid plutons of the Dry Valleys area comprise at least three petrogenetically distinct suites. The older Dry Valleys 1a (DV1a) suite, comprising the Bonney, Catspaw, Denton, Cavendish, and Wheeler Plutons and hornblende-biotite orthogneisses, and Dry Valleys 1b (DV1b) suite, comprising the Hedley, Valhalla, St Johns, Dun, Calkin, and Suess Plutons, biotite granitoid dikes and biotite orthogneisses, were emplaced before prominent swarms of Vanda mafic and felsic dikes. Both the DV1a and DV1b suites are time transgressive, with older intrusions in each suite being emplaced during the later stages of deformation of the Koettlitz Group. Younger granitoids that postdate the majority of the Vanda dikes include: the Dry Valleys 2 (DV2) suite, comprising the Pearse and Nibelungen Plutons plus several smaller, unnamed plugs; and the Harker, Swinford, Orestes, and Brownworth Plutons with identical field relationships and enclaves but distinct chemistries. Chemical characteristics and limited Rb-Sr isotopic dating indicate plutonism before c. 500 Ma was dominated by the Cordilleran I-type DV1a suite, inferred to have developed during melting above a west-dipping subduction zone along the Antarctic Craton margin. The chemical characteristics of the DV1b suite indicate large-scale melting of a quartzo-feldspathic protolith lacking residual plagioclase, but containing refractory garnet. Potential DV1b suite source rocks include metamorphosed immature sediments, possibly underplated along the subduction zone associated with DV1a magmatism, or older granitoid orthogneisses. Major DV1b plutonism at 490 Ma marks the end of subduction-related plutonism in southern Victoria Land. Younger DV2 alkali-calcic, Caledonian I-type plutonism is inferred to have formed in response to uplift and extension between 480 and 455 Ma. Lack of DV2 suite correlatives and Vanda mafic and felsic dikes in northern Victoria Land suggests significantly

  9. 40Ar/39Ar Dating of the Shaxi Porphyry Cu-Au Deposit in the Southern Tan-Lu Fault Zone, Anhui Province

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaoyong; ZHENG Yongfei; XIAO Yilin; DU Jianguo; SUN Weidong

    2007-01-01

    Four samples of plagioclase and biotite from the Shaxi porphyry in the lower part of the Yangtze metallogenic belt were analyzed for age determination with the 40Ar/39Ar method. The results yield reproducible ages of 126 Ma to 135 Ma with a high level of confidence according to the agreement between isochron and plateau ages. The four Ar-Ar ages are relatively consistent within the analytical error. These ages are also consistent with, but more precise than, previous K-Ar and Rb-Sr ages and thus provide better constraints on the time of porphyry formation and associated Cu-Au mineralization along the middle to lower part of the Yangtze metallogenic belt. The ages of 126 to 135 Ma are interpreted to represent the intrusive time of the Shaxi porphyry, so that the Cu-Au mineralization should have occurred later due to the post-magmatic hydrothermal event.

  10. Contribution to the geochemical knowledge of the uranium-radium and thorium families in the southern Vosges. Applications of some results in the prospecting of uranium deposits

    International Nuclear Information System (INIS)

    This work's aim is to lead to a more accurate knowledge of the geochemistry of the Uranium-Radium and Thorium families in the Southern Vosges and to apply some of the results to the prospecting of uraniferous deposits: It has been showed: a bond between Calcium-Magnesium and Uranium-Thorium in the calco-alkaline granites. The host minerals of Uranium and Thorium are hornblende, biotite, titanite and epidote. a concentration of Uranium, at present time with secular disequilibrium in a thermal zone where the satellite mineralizations form an epithermal paragenesis. a disequilibrium of the Uranium-Radium family in the supergene minerals of the lead (phosphate and vanadate) showing the present circulations of Uranium. a bond between the radon grade of the spring waters and Uranium-Radium of the rocks. Such a relation allow to realize a prospecting method based on the determination of radioactive gases from the cold spring-waters of a common country. (author)

  11. Chronology and cooling history of the Tianmenshan pluton in South Jiangxi Province and their geological significance

    Institute of Scientific and Technical Information of China (English)

    ZENG Qingtao; MAO Jianren; HU Qing; ZHAO Xilin; YE Haimin

    2008-01-01

    Geochronological studies on the crust-derived Tianmenshan pluton were undertaken by SHRIMP zircon U-Pb dating and Ar-Ar dating of biotite, muscovite and K-feldspar, giving a petrogenetic age of 167 Ma. Owing to the closure systems in different minerals, the cooling history of the pluton can be determined with an age-temperature diagram. The late hydrothermal event has been recognized, which is related probably with mineralization. In terms of the comparative geochronological and petrologic records, it is concluded that there are some constrains on tectonic evolution and that the formation of the Tianmenshan pluton proceeded in a transition period from lndosinian post-orogeny extension to strong compressive tectonics. And the timing of the hydrothermal event matches the compressive climax of the Yanshanian orogeny. The temporal gap between granite emplacement and wolframite mineralization could last 10-20 Ma owing to the low cooling rate of the pluton.

  12. Chemical characteristics of zircon from A-type granites and comparison to zircon of S-type granites

    Science.gov (United States)

    Breiter, Karel; Lamarão, Claudio Nery; Borges, Régis Munhoz Krás; Dall'Agnol, Roberto

    2014-04-01

    The trace element content in zircons from A-type granites and rhyolites was investigated by using back-scattered electron images and electron microprobe analyses. The studied Proterozoic (Wiborg batholith, Finland and Pará, Amazonas and Goiás states, Brazil) and Variscan (Krušné Hory/Erzgebirge, Czech Republic and Germany) plutons cover a wide range of rocks, from large rapakivi-textured geochemically primitive plutons to small intrusions of F-, Li-, Sn-, Nb-, Ta-, and U-enriched rare-metal granites. While zircon is one of the first crystallized minerals in less fractionated metaluminous and peraluminous granites, it is a late-crystallized phase in peralkaline granites and in evolved granites that may crystallize during the whole process of magma solidification. The early crystals are included in mica, quartz, and feldspar; the late grains are included in fluorite or cryolite or are interstitial. The zircon in hornblende-biotite and biotite granites from the non-mineralized plutons is poor in minor and trace elements; the zircon in moderately fractionated granite varieties is slightly enriched in Hf, Th, U, Y, and HREEs; whereas the zircon in highly fractionated ore-bearing granites may be strongly enriched in Hf (up to 10 wt.% HfO2), Th (up to 10 wt.% ThO2), U (up to 10 wt.% UO2), Y (up to 12 wt.% Y2O3), Sc (up to 3 wt.% Sc2O3), Nb (up to 5 wt.% Nb2O5), Ta (up to 1 wt.% Ta2O5), W (up to 3 wt.% WO3), F (up to 2.5 wt.% F), P (up to 11 wt.% P2O5), and As (up to 1 wt.% As2O5). Metamictized zircons may also be enriched in Bi, Ca, Fe, and Al. The increase in the Hf content coupled with the decrease in the Zr/Hf value in zircon is one of the most reliable indicators of granitic magma evolution. In the zircon of A-type granites, the Zr/Hf value decreases from 41-67 (porphyritic granite) to 16-19 (equigranular granite) in the Kymi stock, Finland, and from 49-52 (biotite granite) to 18-36 (leucogranite) in the Pedra Branca pluton, Brazil. In the in situ strongly

  13. Trace elements in zircon from rocks of the Katugin rare-metal deposit

    Science.gov (United States)

    Levashova, E. V.; Skublov, S. G.; Marin, Yu. B.; Lupashko, T. N.; Ilchenko, E. A.

    2015-12-01

    The Katugin deposit of economic Ta, Nb, Zr, U, REE, Y, and cryolite (Na3AlF6) ores is located in the Kalar district of the Chita region and classified as unique in Nb, Ta, and Y reserves hosted in rare-metal alkali granite. The distribution of trace elements (including REE) in zircon was studied for ore-bearing arfvedsonite-aegirine, biotite-riebeckite rocks, and zones of late recrystallization with nodular zircon clusters. The outer rims and marginal zones of zircon grains are depleted in almost all trace elements except for hafnium as compared with cores and central zones. Compositional features of zircon cores indicate their magmatic origin and do not prove metasomatic nature of the deposit. The similar REE patterns of zircon rims and cores, as well as other attributes assume postmagmatic or metamorphic origin of the rims.

  14. U-Pb dating of zircon from the bed parallel anatectic granitic intrusion in the Baoban group in Hainan Island and the tectonic implication

    Institute of Scientific and Technical Information of China (English)

    DING Shijiang; HU Jianmin; SONG Biao; CHEN Mulun; XIE Shengzhou; FAN Yuan

    2005-01-01

    The petrological and geochemical features of the bed parallel granitic intrusion in the Pre-Cambrian Baoban group in Hainan Island attest to the anatexis origin of the granites. U-Pb dating analyses of zircons from the anatectic granite and the biotite two-feldspar gneiss in the Baoban group, using SHRIMP II in the Beijing Ion-probe Center, acquire 206Pb/238U ages of 368±3.5 Ma (of granite, 95% confidence level, MSDW=1.23) and 362.9±6.1 Ma (of gneiss, 95% confidence level, MSDW = 2.04) respectively. The two late Devonian ages indicate consistently a tectonic- thermal event experienced in Hainan Island, and are the first discovered record of the Devonian geological process in the district. This event possibly resulted from the deep thermal-dynamic process when the Gondwana continent began to break up in the Devonian period.

  15. The XPS study of physical and chemical forms of neptunium group on the surface of minerals

    Directory of Open Access Journals (Sweden)

    Teterin Anton Yu.

    2010-01-01

    Full Text Available The sorption behavior and the physical and chemical forms of neptunium on the surface of minerals of the two chlorate samples, biotite and kaolin, with different contents of Fe(II was studied. The liquid-liquid extraction and the X-ray photoelectron spectroscopy were employed to identify the valence forms of neptunium. On the basis of the obtained data the quantitative elemental composition of the surface of the studied minerals, as well as the ionic composition of the formed neptunium complexes was determined. It was shown that the Np(IV and Np(VI containing compounds did not form, while the complexes Np(VO+ -hydroxyl did form on the surface. The oxygen ions bonded with iron and oxygen belonging to water and/or of carboxyl were suggested to be present in the equatorial plane of the neptunyl group NpO+.

  16. Petrology of plagiogranite from Sjenica, Dinaridic Ophiolite Belt (southwestern Serbia)

    Science.gov (United States)

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

    2012-04-01

    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.

  17. Prograde P-T path of garnet-orthamphibole-gneiss from the Rhuys peninsula (Southern Brittany, France): evidence for a pre-carboniferous collisional stage in the Variscan orogeny

    International Nuclear Information System (INIS)

    A large lens of a magnesian garnet-orthamphibole gneiss with garnets up to 10 cm in diameter has been discovered within the Carboniferous Sarzeau leucogranite (Kerlin quarry, Rhuys peninsula). The garnets of a metamorphosed former magnesio-potassic lamprophyre have core-rim zonations with increasing Mg at constant Ca, and inclusions displaying a staurolite-breakdown reaction structure. Pressure and temperature estimates from garnet-biotite geo-thermometers and garnet-rutile-ilmenite-plagioclase-quartz geo-barometers indicate crystallization during increasing temperature and moderately increasing pressure along a prograde clockwise P-T path from 500 deg. C / 4 kbar to > 750 deg. C / 9 kbar. This prograde path identifies a major tectonic-metamorphic event during a pre-Carboniferous collisional stage in the Variscan orogeny. (authors). 14 refs., 3 figs., 1 tab

  18. Petrology and geochemistry of greywackes of Middle Aravalli supergroup, NW India: evidence for active margin processes

    International Nuclear Information System (INIS)

    Aravalli Mountain Belt (AMB) of Northwestern, India represents one of the major Proterozoic accretionary orogens of the world, preserving two Wilson cycles; viz. Paleoproterozoic Aravalli Supergroup and Mesoproterozoic Delhi Supergroup. Although two gross Wilson cycles involving opening and closing of Paleoproterozoic Aravalli ocean and Mesoproterozoic Delhi ocean are recognized, the finer details of the evolution of the orogen are still poorly understood. We have carried out geochemical and petrological study of the well-preserved greywacke horizon of the 'Middle Aravalli Supergroup' in order to place constraints on early evolution of the Aravalli basin. These greywackes are enriched in Fe, Mg and K; and depleted in Na in comparison to normal greywackes and can be classified as ferroan potassic sandstone. Petrographic examination indicate that the greywacke samples contain about 30 to 50% matrix that is mainly composed of biotite/chlorite and interspersed with fine Fe-Ti rich opaque mineral phases

  19. Petrology, composition, and age of intrusive rocks associated with the Quartz Hill molybdenite deposit, southeastern Alaska.

    Science.gov (United States)

    Hudson, T.; Smith, James G.; Elliott, R.L.

    1979-01-01

    A large porphyry molybdenum deposit (Quartz Hill deposit) was recently discovered in the heart of the Coast Range batholithic complex about 70 km E of Ketchikan, SE Alaska. Intrusive rocks associated with the mineral deposit form two composite epizonal to hypabyssal stocks and many dikes in country rocks. All observed metallization and alteration is within the Quartz Hill stock. Molybdenite forms fracture coatings and occurs in veins with quartz. Alteration is widespread and includes development of secondary quartz, pyrite, K-feldspar, biotite, white mica, chlorite, and zeolite. Field relations indicate that the stocks were emplaced after regional uplift and erosion of the Coast Range batholithic complex, and K-Ar data show that intrusion and alteration took place in late Oligocene time, about 27 to 30 Ma ago. Data from the Ketchikan quadrangle indicate that porphyry molybdenum metallization in the Coast Range batholithic complex is associated with regionally extensive but spotty, middle Tertiary or younger, felsic magmatism. -from Authors

  20. The sulphur springs geothermal field, St. Lucia, lesser Antilles: Hydrothermal mineralogy of wells SL-1 and SL-2

    Science.gov (United States)

    Battaglia, S.; Gianelli, G.; Rossi, R.; Cavarretta, G.

    Two wells have been drilled to depths of 1413 and 2213 meters in the geothermal field of Sulphur Springs, St. Lucia, and reveal a complex volcanic sequence characterized by collapse episodes followed by the emplacement of dacite domes. The geothermal reservoir consists of fractured volcanic rocks and produces superheated steam. Well-bottom temperatures are around 270-290°C. The hydrothermal alteration found in both the productive SL-2 well and the non-productive SL-1 is strongly reminiscent of that of porphyry copper deposits, with (1) an inner, high-temperature potassic zone characterized by the occurrence of dravitic tourmaline, quartz, and biotite, (2) an outer propylitic alteration zone that is partly superimposed on (3) a potassic alteration zone. The alteration mineral assemblages indicate that the hydrothermal system has cooled at the levels sampled.

  1. METARHYOLITES OF VRANICA MOUNTAIN IN PALEOZOIC OF CENTRAL BOSNIA

    Directory of Open Access Journals (Sweden)

    Vladimir Majer

    2001-12-01

    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.

  2. Geochemical, petrological, geo dynamic and radiometric age dating investigation of Aqdarreh intrusion massive (north of Takab) northwest of Iran

    International Nuclear Information System (INIS)

    Aqdarreh intrusi body with an area of 30 km 2 is located in 34 km north of Takab, northwest of Iran. This batholith is situated in Central Iran, cutting Paleozoic rocks. Radiometric age of Aqdarreh batholith by K-Ar method is 48.38 m. a.,corresponding to Eocene magmatism. Aqdarreh intrusive body consists of tonalite, granodiorite, alkali feldspar granite and monzogranite in which the main mafic mineral is biotite. Further more, there is not any enclave in these rocks. Study of the investigated samples shows that Aqdarreh intrusive rocks have two different generations. Part of the collected samples belongs to I-type granite (calc-alkaline) and others represent the A-type granite (alkaline). It seems that this process is created by the contamination of alkaline magma by crustal materials. Geochemistry of the rare earth elements shows that the tectonic setting of the body is compatible with Post Orogenic Granitoids

  3. LA-ICP-MS zircon U-Pb dating,geochemistry of the Mishuling intrusion in western Qinling and their tectonic significance.%西秦岭糜署岭花岗岩体年代学、地球化学特征及其构造意义

    Institute of Scientific and Technical Information of China (English)

    李佐臣; 裴先治; 李瑞保; 裴磊; 胡波; 刘成军; 陈国超; 陈有炘

    2013-01-01

    An EW trending Indosinian granitoide belt distributes near the Mianlue Suture Zone in the southern margin of the Qinling Orogenic Belt.The Mishuling intrution is one of the Indosinian granitoids located in the western Qingling and north to the Mianlue Suture Zone.This article studies the LA-ICP-MS zircon U-Pb ages and geochemistry characteristics of the Mishuling biotite quartz monzonite and monzodiorite enclaves.The results show that the crystallization age of the Mishuling biotite quartz monzonite is 214.5 ±1.6Ma(MSWD =0.24).The A/CNK ratios of the Mishuling biotite quartz monzonite and monzodiorite enclaves range from 0.64 to 0.97,indicating that the granitoids are metaluminous rocks.The Σ REE of the granitoides are 197.3 × 10-6 ~ 246.6 × 10-6.The REE patterns show rightward incline and moderate negative Eu anomaly.The trace element geochemistry is characterized evidently by negative anomaly of Ta,Nb,P,Ti,Ba,Sr,etc.and positive anomaly of Rb,U,La,Zr,Hf,Nd,Y,etc.The host rock biotite quartz monzonite and enclaves monzodiorite are Ⅰ-type granitoids,which may originate from a single magma.The magma was formed by partial melting of basic rocks.The Mishuling intrusions are post-orogenic granitoids which were formed in a transitional tectonic setting from syn-(compressional setting) to post-collision (extensional setting).They were products formed by partial melting of thicken lower crust resulting from the collision between the North China plate and Yangtze plate.%秦岭造山带南缘勉略缝合带附近发育东西向展布的印支期花岗岩带,位于西秦岭地区勉略缝合带北侧的糜署岭岩体是该花岗岩带的一部分.本文对糜署岭岩体寄主岩及二长闪长质包体进行LA-ICP-MS锆石U-Pb定年和地球化学特征研究.结果表明,糜署岭岩体的结晶年龄为214.5±1.6Ma(MSWD =0.24).糜署岭岩体寄主岩和二长闪长质包体A/CNK在0.64~0.97之间,具有准铝质特征.稀土元素总量(ΣREE)为197.3×10-6

  4. Petrochemistry and petrology of I-type granitoids in an arc setting: the composite Torul pluton, Eastern Pontides, NE Turkey

    Science.gov (United States)

    Kaygusuz, Abdullah; Siebel, Wolfgang; Şen, Cüneyt; Satir, Muharrem

    2008-07-01

    The Upper Cretaceous Torul pluton, located in the Eastern Pontides, is of sub-alkaline affinity and displays features typical of volcanic arc granitoids. It is a composite pluton consisting of granodiorite, biotite hornblende monzogranite, quartz monzodiorite, quartz monzonite and hornblende biotite monzogranite. The oldest syenogranite (77.9 ± 0.3 Ma) and the youngest quartz diorite form small stocks within the pluton. Samples from the granodiorites, biotite hornblende monzogranites, quartz monzodiorites, quartz monzonites and hornblende biotite monzogranites have SiO2 between 57 and 68 wt% and display high-K calc-alkaline, metaluminous to peraluminous characteristics. Chondrite-normalized REE patterns are fractionated (Lacn/Lucn = 6.0-14.2) with pronounced negative Eu anomalies (Eu/Eu* = 0.59-0.84). Initial ɛNd(i) values vary between -3.1 and -4.1, initial 87Sr/86Sr values between 0.7058 and 0.7072, and δ18O values between +4.4 and +7.3‰. The quartz diorites are characterized by relatively high Mg-number of 36-38, low contents of Na2O (2.3-2.5 wt%) and SiO2 (52-55 wt%) and medium-K calc-alkaline, metaluminous composition. Chondrite-normalized REE patterns are relatively flat [(La/Yb)cn = 2.8-3.3; (Tb/Yb)cn = 1.2] and show small negative Eu anomalies (Eu/Eu* = 0.74-0.76). Compared to the other rock types, radiogenic isotope signatures of the quartz diorites show higher 87Sr/86Sr (0.7075-0.7079) and lower ɛNd(i) (-4.5 to -5.3). The syenogranites have high SiO2 (70-74 wt%) and display high-K calc-alkaline, peraluminous characteristics. Their REE patterns are characterized by higher Lacn/Lucn (12.9) and Eu/Eu* (0.76-0.77) values compared to the quartz diorites. Isotopic signatures of these rocks [ɛNd(i) = -4.0 to -3.3; 87Sr/86Sr(i) = 0.7034-0.7060; δ18 O = + 4.9 to + 8.2] are largely similar to the other rock types but differ from that of the quartz diorites. Fractionation of plagioclase, hornblende, pyroxene and Fe-Ti oxides played an important role in the

  5. K-Ar and Rb-Sr minerals ages of skarns and associated metabasites and leptites in the Hjulsjoe area of the Bergslagen ore province, central Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Moorman, A.C.; Andriessen, P.A.M.; Boelrijk, N.A.I.M.; Hebeda, E.H.; Priem, H.N.A.; Verdurmen, E.A.T.; Verschure, R.H. (Z.W.O. Laboratorium voor Isotopen-Geologie, De Boelaan (Netherlands)); Oen, I.S. (Universiteit van Amsterdam (Netherlands)); Wiklander, U. (Sveriges Geologiska Undersoekning, Uppsala (Sweden))

    1982-10-25

    K-Ar analyses of 20 hornblendes from skarns and associated metabasites in the Hjulsjoe area of the Bergslagen ore province, central Sweden, define an age of 1.83+-0.05 Ga. This age is interpreted in terms of the geological relationships as signalling a period of skarn-formation and metamorphism along with episodes of shearing and basic dike intrusion. Following the hypothesis that the skarn ores were formed by sea-floor hydrothermal metamorphism, this age should also be attributed to the deposition of the enclosing volcano-sedimentary leptite-haelleflinta sequence and the injection and extrusion of basic magma. Analyses of 13 biotites from the skarns and enclosing metavolcanic leptites produce K-Ar and Rb-Sr ages of 1.69+-0.05 Ga and 1.65+-0.04 Ga, respectively; these are related to an episode of mild crustal heating associated with nearby post-orogenic granite intrusion dated at 1.70 Ga.

  6. Characteristics and significance of ductile shear zone in Tianli, Jiangxi Province and Youxi, Zhejiang Province

    International Nuclear Information System (INIS)

    The result of experiment show that 40Ar/39Ar plateau age of muscovite which is from Tianli petrofabric in Guanfeng county, Jiangxi Province is 1019 +- 0.9 Ma, and 40Ar/39Ar plateau age of biotite which is from migmatite in Youxi petrofabric Jiangshan county, Zhejiang Province is 501.2 +- 2.2 Ma, and the heat event age is 127 Ma. The research shows that they are two larger scale ductile shear zones. The 40Ar/39Ar plateau ages represent respectively the forming time of Tianli ductile shear zone and Youxi ductile shear zone. According to the age data and regional geological investigation analysis, they belong separately to the part of two tectonic units of Yangtze and south China. It also shows that Jiang-Shao tectonic zone undergoes multiphase orogeny which are Jinning, Caledonian, Indosinian and Yanshanian epoch. It is of geological significance for re-understand again the crust evolution of south China

  7. Confirmation of pelitic granulite in the Altai orogen and its geological significance

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; WEI ChunJing; WANG Tao; LOU YuXing; CHU Hang

    2009-01-01

    The existence of pelitic granulite in the Altai orogen was confirmed for the first time by detailed petro-graphic research and P-T pseudosection modeling. The pelitic granulite has the assemblage of garnet + cordierite + K-feldspar + biotite + sillimanite + plagioclase + quartz with some samples containing the paragenesis of cordierite + spinel. Peak conditions of the pelitic granulite determined from the P-T pseudosection involved P= 0.5-0.6 GPa, T= 780-800?*, belonging to medium-to low-pressure type. SHRIMP U-Pb dating of zircon presented a metamorphic age of 292.8 ± 2.3 Ma. The discovery of pelitic granulite reflects an extensional environment with high heat flow in the southern margin of the Altai orogen during the Early Permian, which provides an important petrological constraint on the evolution of the Altai orogen.

  8. Kyanite-garnet gneisses of the Kåfjord Nappe - North Norwegian Caledonides: P-T conditions and monazite Th-U-Pb dating

    Science.gov (United States)

    Ziemniak, Grzegorz; Kośmińska, Karolina; Majka, Jarosław; Janák, Marian; Manecki, Maciej

    2016-04-01

    The Kåfjord Nappe is the part of the Skibotn Nappe Complex traditionally ascribed to the Upper Allochthon of the North Norwegian Caledonides. Pressure-temperature (P-T) conditions and metamorphic age of the Kåfjord Nappe are not well constrained, geochronological data are limited to a single Rb-Sr age of c. 440 Ma (Dangla et al. 1978). Metamorphic evolution of kyanite-garnet gneisses of the Kåfjord Nappe is presented here. The kyanite-garnet gneisses are associated with a few meters thick amphibolite lenses. The gneisses mainly consist of quartz, plagioclase, biotite, muscovite, garnet, kyanite, and rutile. Retrograde minerals are represented by sillimanite and chlorite. Garnet occurs as two textural types. Garnet-I forms euhedral porphyroblasts with multiple small inclusions. Profiles through garnet-I show chemical zonation in all components. The composition varies from Alm64-68Prp11-16Grs13-18Sps2-8 in the core to Alm68-70Prp17-18Grs10-13Sps1-3 in the rim. Garnet-II is subhedral to anhedral, its core is inclusion-rich, whereas rim contains only single inclusions. Chemical composition of garnet-II is similar to that of the garnet-I rim. P-T conditions have been estimated using the garnet-biotite-muscovite-plagioclase (GBPM) geothermobarometer (Holdaway, 2001; Wu, 2014). Calculated peak P-T metamorphic conditions are 610-625 °C and 7.6-8.2 kbar corresponding to the amphibolite facies conditions. Phase equilibrium modelling in the NCKFMMnASH system yields peak metamorphic conditions of c. 620 °C at 8 kbar. Growth conditions of garnet-I core modelled in the NCKFMMnASH system are c. 570 °C at 9.7 kbar. Chemical Th-U-total Pb monazite dating has been performed. Preliminary dating results from the kyanite-garnet gneiss of the Kåfjord Nappe yield an array of dates from 468 Ma to 404 Ma. There is a correlation between an increase of yttrium content and decrease of monazite single dates. Compositional maps confirm an increase of yttrium towards the rim of the

  9. A Palaeoproterozoic multi-stage hydrothermal alteration system at Nalunaq gold deposit, South Greenland

    DEFF Research Database (Denmark)

    Bell, Robin-Marie; Kolb, Jochen; Waight, Tod Earle;

    2016-01-01

    Nalunaq is an orogenic, high gold grade deposit situated on the Nanortalik Peninsula, South Greenland. Mineralisation is hosted in shear zone-controlled quartz veins, located in fine- and medium-grained amphibolite. The deposit was the site of Greenland’s only operating metalliferous mine until its...... closure in 2014, having produced 10.67 t of gold. This study uses a combination of field investigation, petrography and U/Pb zircon and titanite geochronology to define a multistage hydrothermal alteration system at Nalunaq. A clinopyroxene-plagioclase-garnet(-sulphide) alteration zone (CPGZ) developed in...... the Nanortalik Peninsula, close to regional peak metamorphism and prior to gold-quartz vein formation. The ca. 1783–1762-Ma gold-quartz veins are hosted in reactivated shear zones with a hydrothermal alteration halo of biotite...

  10. K/Ar ages from basal gneiss region

    International Nuclear Information System (INIS)

    K/Ar and 40Ar/39Ar geochronology of minerals from the Stadlandet region, Norway, is complicated by the presence of excess 40Ar in many samples. There is a correlation between excess 40Ar concentration and textural occurrence of samples. Amphiboles and micas closely accociated with eclogite pods are likely to contain significant concentrations of excess 40Ar, while samples from the country rocks are not. K/Ar and 40Ar/39Ar ages for hornblende from the country rocks suggest that post-metamorphic cooling through 5000C occured about 410 Ma ago, shortly after eclogite formation. Biotites containing no excess 40Ar cooled through 3000C about 370 Ma ago. A post-metamorphic cooling rate of about 50C/Ma can be inferred

  11. Grenvillian thermal event and remnant charnockite: Isotopic evidence from the Chilka Lake granulite-migmatite suite in the Eastern Ghats belt, India

    Indian Academy of Sciences (India)

    S Bhattacharya; M P Deomurari; W Teixeira

    2002-12-01

    Spectacular exposures of granulite-migmatite occur in the Chilka Lake area of the Eastern Ghats belt. The garnetiferous granite gneiss of peraluminous granitic composition, often contains restitic metapelite inclusions and is demonstrably a product of biotite-dehydration melting in pelitic rocks. On the other hand, older layers and bands of charnockitic rocks frequently occur as dismembered patches within the peraluminous granite, thus imparting a measled appearance of the granite exposures. The partial melting and emplacement of the peraluminous granite represent the Grenvillian thermal event, as evidenced by Rb-Sr whole rock and Pb-Pb zircon dating. On the other hand, minor patches of charnockite represent migmatized relict, as evidenced by some older zircons, in addition to those of Grenvillian age.

  12. Complex electric conductivity of rocks

    International Nuclear Information System (INIS)

    Laboratory measurements of complex conductivity were made on 28 drill-core samples from area MM1-Prospect 1 of the Carajas Mining District. The objective of this research was to help interpret field geophysical survey of the area using Induced Polarization and AFMAG methods. A petrographic study of the samples was done, using thin sections, polished sections and X-ray diffraction. Copper content, in the form of sulfides, was determined using atomic absorption. As a result of the petrographic study, the samples were classified in five distinct groups: granite, biotite schist, amphibolite and magnetite quartzite-iron formation. The grade of Cu was variable in the five groups, ranging from 50 ppm to 6000 ppm. In conclusion, these measurements show that the field Induced Polarization and AFMAG anomalies near these three drill holes (F1, F2 and F3) are due primarily to the magnetic iron formation, and secondarily due to associated low-grade chalcopyrite mineralization. (author)

  13. Shoshonitic intrusion magmatism in Pajeu-Paraiba belt: the Bom Jardim complex

    International Nuclear Information System (INIS)

    The Bom Jardim complex is a multi phase intrusion emplaced within the basement of the Pajeu-Paraiba belt, in the Borborema province, N.E., Brazil, during the Pan African (Brasiliano) orogeny, 600 Ma ago. The Bom Jardim complex is primarily composed of monzonites and syenites with subordinated granites. The major and trace elements geochemistry has established a shoshonitic affinity for the monzonite-syenite assemblages, whereas the granites are clearly of a high-K calc-alkaline character. The main geochemical trends determined for the complex are the result of fractionation of mainly amphibole, biotite, alkali feldspar ±clinopyroxene within the developing magmas. The enrichment in transition metal elements, LILE and high LILE/HSFE ratios, coupled with an initial Sr sup(87)/Sr sup(86) ratio of 0.70709 is consistent with a subduction related magma source. (author)

  14. 斑岩铜(钼)矿成矿作用的地球化学特征

    Institute of Scientific and Technical Information of China (English)

    朱炳球; 徐外生

    1984-01-01

    Dealt with in this paper are some geochemical characteristics of mineralization of porphyry copper deposits, especially those observed in intrusive bodies, wa11 rocks, alteration zones, ores and individual pyrites. Productive intrusions have been correlated with barre nones from such aspects as major and trace elements, copper contents of biotite and pyrite,and distribution pattern of copper. In the mineralized rocks, trace elements show apparent zoning surrounding ore bodies; major and trace dements seem to show some reguIarity of variation in the process of alteration, and as a result each alteration zone displays its own peculiar element combination. Trace dements in ores can provide information on the genesis of ore deposits, thus of great help in distinguishing ore types while those in pyrites may be indicative of mineralization, provide dues for distinguishing orebearing from barren rocks,and reflect the degree of erosion of ore bodies.

  15. Sur l'origine par altération du substratum schisteux de la minéralisation chlorurée des eaux d'une nappe côtière sous climat semi-aride (Chtouka-Massa, Maroc)

    Science.gov (United States)

    Krimissa, Samira; Michelot, Jean-Luc; Bouchaou, Lhoussaine; Mudry, Jacques; Hsissou, Youssef

    2004-11-01

    The origin of chloride ions in groundwater from the Chtouka-Massa plain (Morocco) was studied by using chemical and isotopic analyses of water, and petrographic and chemical analyses of rocks. It appears that the schist formation, which forms the basement of the studied aquifer, is the main source of the high Cl - concentrations in groundwater. In these schists, chloride is, for a part, probably contained in biotites, and is released into groundwater through the weathering of these minerals. However, the exceptionally high chloride contents of these schists are difficult to explain if one does not assume that they also contain evaporitic-type minerals. To cite this article: S. Krimissa et al., C. R. Geoscience 336 (2004).

  16. A study on the U speciation in groundwater of a hard rock aquifer in South India

    International Nuclear Information System (INIS)

    Speciation of uranium indicates the contribution of this ion into different species. An attempt has been made to study the spatial and temporal variations of U speciation in the hard rock aquifer of South India. The major rock types have granulite facies with high grade metamorphic rocks and younger intrusive. It also comprises of Fissile hornblende biotite gneiss, Charnockite, Quartzite, Granite and Flood Plain Alluvium. A total of 108 samples were collected from the handpumps of the study area for two seasons (Pre monsoon and South West monsoon). The groundwater samples were analysed for U and other ions like Ca2+, Mg2+, Na+ and K+, HCO3-, Cl-, SO42-, PO43-, NO3-, F-, H4SiO4, pH, EC and TDS using standard procedures

  17. The Laramide Mesa formation and the Ojo de Agua caldera, southeast of the Cananea copper mining district, Sonora, Mexico

    Science.gov (United States)

    Cox, Dennis P.; Miller, Robert J.; Woodbourne, Keith L.

    2006-01-01

    The Mesa Formation extends from Cananea, Mexico, southeast to the Sonora River and is the main host rock of Laramide porphyry copper deposits in the Cananea District and at the Alacran porphyry prospect to the east. The Mesa consists of two members-a lower andesite and an upper dacite. The lowest part of the dacite member is a crystal tuff about 100 m thick. This tuff is the outfall of a caldera centered near the village of Ojo de Agua, dated by 40Ar/39Ar at 65.8 Ma ?0.4. The Ojo de Agua Caldera is about 9 km in diameter and is filled by a light gray biotite dacite tuff with abundant flattened pumice fragments. The volume of the caldera is estimated to be 24 km3.

  18. 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)

  19. Surprising discovery of high-grade pelitic schist on Cavalli Seamount, offshore Northland

    International Nuclear Information System (INIS)

    Serendipity waits in the world's unexplored places. In March 1999, GNS's ONSIDE expedition to the South Fiji Basin made two dredge hauls on Cavalli seamount expecting to recover Miocene oceanic volcanic rocks. Instead dredge DIA recored 1 kg of 10 cm slickensided and chloritised schist pieces and dredge DIB, which was 1.1 km distant, 100 kg of well-foliated biotite schist, mainly in the form of two large subangular boulders. The presence of calsilicate bands initially suggested a correlation with Buller or Takaka Terranes, but whole rock chemical composition of the schist is more consistent with Murihiku, Waipapa or Pahau Terranes. U-Pb TIMS gheochronometry of individual detrital zircons indicates a maximum 170Ma depositional age for the schist protolith, thus clearly ruling out a Buller or Takaka correlation. Rb-Sr whole rock data suggest a young (Cenozoic?) metamorphic age. (author)

  20. Sorption experiments at oxic and anoxic conditions

    International Nuclear Information System (INIS)

    Sorption of U, Pu, Np, Th and Tc at anoxic conditions were studied using radionuclides 233U, 236Pu, 237Np, 234Th and 99Tc. Samples were selected to represent common rocks and minerals in Finnish bedrock. The determinations of K-values and sorption percents in quartz plagioclase, potassium feldspar, honrnblende, biotite, mica gneiss, tonalite, granodiorite, porphyritic granite, granitic gneiss and rapakivi granite were performed by the autoradiographic method. The sorpion of these elements was studied under anoxic conditions using synthetic granitic ground water and synthetic bentonite water containing ferrous iron. For redox-sensitive U, Np and Pu experiments were made by spiking samples with water containing the radioactive isotope at one specified oxidation state

  1. The Paranagua Batholith: proposition, age, petrogenetic considerations and tectonics implication

    International Nuclear Information System (INIS)

    The Paranagua Batholith comprises the major portion of the Costeiro Domain which is one of the three internal tectonic unities of the Joinville Massif in the southern Brazil (Mantiqueira Province). U-Pb in zircon (614 ± 10 Ma) and Rb-Sr whole rock isochron (543 ± 21 Ma) data are interpreted respectively as ages of the mineral crystallization and granitoid emplacement for the main igneous phase of the Paranagua Batholith. Sr, Pb and Nd analyses carried on this coarse biotite-microcline granitoid reveals its crustal melt origin with a source in the lower crust. It is here proposed the association of this Costeiro Domain (Parana), the Costeiro Complex (Sao Paulo) and Brusque Belt (or Tijucas Belt, Santa Catarina) as parts of the same collisional structure of the southern region of South America. (author)

  2. Assessment of groundwater potential based on aquifer properties of hard rock terrain in the Chittar-Uppodai watershed, Tamil Nadu, India

    Science.gov (United States)

    Kumar, T. Jeyavel Raja; Balasubramanian, A.; Kumar, R. S.; Dushiyanthan, C.; Thiruneelakandan, B.; Suresh, R.; Karthikeyan, K.; Davidraju, D.

    2014-07-01

    Aquifer performance was tested in 24 locations to assess the groundwater potential of the hard rock terrain in the Chittar-Uppodai watershed of the Tambaraparani River basin. Geologically, the area consists of biotite gneiss, charnockite, and quartzite. The aquifer characteristics, such as transmissivity (T), the storage coefficient, specific capacity, optimum yield, and the recovery rate were calculated. The drawdown transmissivity was determined using Jacob's straight-line method, while the recovery transmissivity was determined by the Theis method. The drawdown transmissivity was low in the western areas, particularly at Kadayanallur, and was higher in the other areas. The recovery transmissivity was high in the western area, and, with the exception of Gangaikondan, was low at other locations. The assessment indicates that there is groundwater potential in the western part of the study area because of favorable results for recovery drawdown, aquifer thickness, and specific capacity.

  3. Sphene-centered ocellar texture as a petrological tool to unveil the mechanism facilitating magma mixing

    Science.gov (United States)

    Gogoi, Bibhuti; Saikia, Ashima; Ahmad, Mansoor

    2015-04-01

    The sphene-centered ocellar texture is a unique magma mixing feature characterized by leucocratic ocelli of sphene enclosed in a biotite/hornblende-rich matrix (Hibbard, 1991). The ocelli usually consist of plagioclase, K-feldspar and quartz with sphene crystals at its centre. Although geochemical and isotopic data provide concrete evidence for the interaction between two compositionally distinct magmas, the exact processes by which mixing takes place is yet uncertain. So, textural analysis can be used to decipher the behaviour of two disparate magmas during mixing. Presented work is being carried out on the sphene ocelli, occurring in hybrid rocks of the Nimchak Granite Pluton (NGP), to understand its formation while two compositionally different magmas come in contact and try to equilibrate. The NGP is ca. 1 km2in extent which has been extensively intruded by number of mafic dykes exhibiting well preserved magma mixing and mingling structures and textures in the Bathani Volcano-Sedimentary Sequence (BVSS) located on the northern fringe of the Proterozoic Chotanagpur Granite Gneiss Complex (CGGC) of eastern Indian Shield. From petrographic and mineral chemical studies we infer that when basaltic magma intruded the crystallizing granite magma chamber, initially the two compositionally different magmas existed as separate entities. The first interaction that took place between the two phases is diffusion of heat from the relatively hotter mafic magma to the colder felsic one followed by diffusion of elemental components like K and incompatible elements from the felsic to the mafic domain. Once thermal equilibrium was attained between the mafic and felsic melts, the rheological contrasts between the two phases were greatly reduced. This allowed the felsic magma to back-vein into the mafic magma. The influx of back-veined felsic melt into the mafic system disrupted the equilibrium conditions in the mafic domain wherein minerals like amphibole, plagioclase and biotite

  4. Geochemistry and mineralogy of the radioactive minerals associated with some pegmatite veins of the Ukma-Nawahatu-Hursi sector, Purulia Dist., W.B., in the precambrian Chhotanagpur gneissic complex

    International Nuclear Information System (INIS)

    Some barite-bearing pegmatites in the Ukma-Nawahatu-Hursi sector (23° 25'-26'N, 86° 02'-04'E) of the Purulia dist., West Bengal, have association of radioactive minerals in the form of coarse grained pitchblack lumps and irregular patches. This radioactive belt of about 15 km length running through Ukma, Nawahatu and Hursi areas follows ENE-WSW trending shear zone. The barite-bearing pegmatites occur as lenses or lenticular veins hosted by garnetiferous sillimanite-biotite-quartz-schist or occasionally by migmatite. Near Nawahatu the radioactive barite-pegmatite vein occurs at or near the junction between footwall amphibolite and hangingwall garnetiferous schist. The pegmatite veins have mainly followed the schistosity of the host rock and dip 70°-80° towards south

  5. Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups

    Science.gov (United States)

    Hulsbosch, Niels; Hertogen, Jan; Dewaele, Stijn; André, Luc; Muchez, Philippe

    2014-05-01

    This study presents a general model for the evaluation of Rayleigh fractional crystallisation as the principal differentiation mechanism in the formation of regionally zoned common and rare-element pegmatites. The magmatic evolution of these systems from a granitic source is reconstructed by means of alkali element and rare earth element (REE) analyses of rock-forming minerals (feldspars, micas and tourmaline), which represent a whole sequence of regional pegmatite zonation. The Gatumba pegmatite field (Rwanda, Central Africa) is chosen as case study area because of its well-developed regional zonation sequence. The pegmatites are spatially and temporally related to peraluminous G4-granites (986 ± 10 Ma). The regional zonation is developed around a G4-granite and the proximal pegmatites grade outwardly into biotite, two-mica and muscovite pegmatites. Rare-element (Nb-Ta-Sn) pegmatites occur most distal from the granite.

  6. Mineralogical Description of the Skarn from Mraconia Valley, Almaj Mountains, Romania

    Science.gov (United States)

    Anason, Maria Angela; Stefan, Marincea; Delia Georgeta, Dumitras

    2014-05-01

    The purpose of this paper is to update knowledge of the investegated area. The research are overlaps of the hidrographic basin of the Mraconia Valley, at north is bounded by the alignment Poiana Mraconia and Lugojistea; at east by the Satului Valley; souther limit is constitutes by the Ponicova Valley and the western limit is Cracul Radului-Cracul Urzicea. The skarn was described for the first time in the 1934 by the A. Streckeisan with the name Catramat Series; this series was a kata-mezonal character, which is the debris of an old canvas with Upper Carbonifer age. The crystalline schist of the Poiana Mraconia Series, are studied by Al. Codarcea, I. Bercia, E. Bercia (1934) and suffered a progressive metamorphism in the amphibolites with alamandine facies and the disten-alamandine-muscovite subfacies, together revealed the metapelithe paragenesis including disten, green hornblende, andezine and alamandine.The primar metamorphism were followed to the regressive metamorphism by the Assyntic orogene and Varisc cycles (I. Bercia, E. Bercia, 1975). Petrografically exceed the amphibolites paragnaice and the micacee paragnaice, with biotite and garnet, associated with the quartz-feldspar gneiss and feldspar quartzite, affected by the arthritic migmatization. Fine grain, sharp sistuozity, the muscovite are frequent and the pegmatite absence leading to the Poiana Mraconia crystalline differentiation by the Ielova crystalline, bud both are included in the Almaj complex. Mineralogical and petrographic study of the Mraconia skarns serves in predicting the relations between the magmatite form the upper basin of the valley (with the mineralization of the W and Mo), and the adjacent formations. This paper wants to emphasize the next petrographic types following: 1. the micacee paragnais are characterized by the existing of the quartz, plagioclase, microcline, muscovite, biotite, chlorite and epidote; 2. The micacee paragnais with garnet are definite by the paragenisis: quartz

  7. The biodegradation of layered silicates under the influence of cyanobacterial-actinomycetes associations

    Science.gov (United States)

    Ivanova, Ekaterina

    2013-04-01

    The weathering of sheet silicates is well known to be related to local and global geochemical cycles. Content and composition of clay minerals in soil determine the sorption properties of the soil horizons, water-holding capacity of the soil, stickiness, plasticity, etc. Microorganisms have a diverse range of mechanisms of minerals' structure transformation (acid- and alkali formation, biosorption, complexing, etc). One of the methods is an ability of exopolysaccharide-formation, in particular the formation of mucus, common to many bacteria, including cyanobacteria. Mucous covers cyanobacteria are the specific econiches for other bacteria, including actinomycetes. The objective was to analyze the structural changes of clay minerals under the influence of the cyanobacterial-actinomycetes associative growth. The objects of the study were: 1) the experimental symbiotic association, consisting of free-living heterocyst-formative cyanobacterium Anabaena variabilis Kutz. ATCC 294132 and actinomycete Streptomyces cyaneofuscatus FR837630, 2) rock samples obtained from the Museum of the Soil Science Department of the Lomonosov Moscow State University: kaolinite, consisting of kaolin (96%) Al4 (OH) 8 [Si4O10]; mixed with hydromica, chlorite and quartz; vermiculite, consisting of vermiculite (Ca, Mg, ...)*(Mg, Fe)3(OH)2[(Si, Al)4O10]*4H2O and trioctahedral mica (biotite). The mineralogical compositions of the rocks were determined by the universal X-ray Diffractometer Carl Zeiss Yena. The operationg regime was kept constant (30 kv, 40 mA). The cultivation of the association of actinomycete S. cyanoefuscatus and cyanobacterium A. variabilis caused a reduction in the intensity of kaolinite and hydromica reflexes. However, since both (mica and kaolinite) components have a rigid structure, the significant structural transformation of the minerals was not revealed. Another pattern was observed in the experiment, where the rock sample of vermiculite was used as the mineral

  8. A desk study of surface diffusion and mass transport in clay

    International Nuclear Information System (INIS)

    The concept of a geological barrier to radionuclide migration from theoretical radioactive waste repositories has drawn attention to the physico-chemical properties of clays, which are traditionally regarded as retarding media. This report addresses the different mechanisms of transport of radionuclides through clay and in particular focuses on the surface diffusion movement of sorbed cations. The relative contributory importance of the different transport mechanisms is governed by the pore size distributions and interconnections within the clay fabric. Surface diffusion data in the literature have been from experiments using compacted montmorillonite and biotite gneiss. A possible programme of laboratory work is outlined, based on diffusion experiments, which describes the way of measuring the effect of surface diffusion more accurately in clays, mudstones and shales. (author)

  9. Trachytic Rock and Associated Fenitization in the Bayan Obo Ore Deposit, Inner Mongolia, China: Evidence for Magmatic-Hydrothermal Mineralization Related to a Carbonatitic Complex

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Trachytic rock and its altered rock-FONT-fenite-in the Bayan Obo ore district, Inner Mongolia, China, were referred to as slate or feldspar rock before, and identified by the authors for the first time (in 1992). In the paper the mineral assemblages, structures and textures and petrochemical compositions of the rocks, as well as the electron microprobe analysis of feldspars in the rocks are described. The Sm-Nd isochron age of the trachytic rock is 1096±56 Ma, with INd=0.51100±4 (2σ) and e Nd(t)= - 4.4±0.7. Alterations of the trachytic rock, including microclinization, riebeckitization, aegirinization and biotitization, and accompanied rare element and REE mineralizations are discussed. Based on the occurrence of the trachytic rock and associated fenitization it is deduced that the Bayan Obo Fe-Nb-REE ore deposit is genetically related to magmatic-hydrothermal activity of an alkali carbonatite complex.

  10. Deep-seated geology of the granite intrusions at the Soultz EGS site based on data from 5 km-deep boreholes

    Energy Technology Data Exchange (ETDEWEB)

    Hooijkaas, Gerridina R. [Departments of Petrology and Isotope Geochemistry, Institute of Earth Sciences, Vrije Universiteit, De Boelelaan 1085, NL 1081 HV, Amsterdam (Netherlands); Genter, Albert; Dezayes, Chrystel [French Geological Survey, BRGM, 3 Avenue Claude Guillemin, BP6009, F-45060 Orleans Cedex 2 (France)

    2006-10-15

    The petrographic model for the deep-seated geology at the Soultz-sous-Forets Enhanced Geothermal System (EGS) site in the Rhine Graben, France, was revised on the basis of data from 5 km-deep wells. Several types of granite and sub-facies were characterized through thin-section analysis of drill cuttings. Various datalogs were studied to correlate them with petrography. The new geological model of the Soultz site is made up of a massive porphyritic granite that shows some paleo-weathering at its top, overlain by about 1400 m of Mesozoic and Tertiary sediments. Between 2700 and 3200 m depth, the same granite is highly fractured and hydrothermally altered. Below this zone, the granite is less fractured and is very rich in biotite and amphibole. Starting at 4700 m depth is a younger, fine-grained, two-mica and amphibole-rich granite that intrudes into the porphyritic granite. (author)

  11. Age of Anzishan granulites in the Mianxian-Lueyang suture zone of Qingling orogen: With a discussion of the timing offinal assembly of Yangtze and North China craton blocks

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Many granulite blocks have been recently discovered in the Anzishan area, Mianxian County, Shaanxi Province, in the central segment of the Mianxian-Lueyang suture zone. Sm-Nd isochron and 40Ar/39Ar ages of mineral samples of granulites from this area are reported in the note. The granulite mineral samples give a Sm-Nd isochron age of t=(206 ( 55) Ma (2(), with INd = 0.51302(7(2() and MSWD = 1.6, and a biotite 40Ar/39Ar plateau age of (199.7(1.7) Ma (2(). The formation and uplift of the granulites were related to subduction of the Yangtze block beneath the South Qinling microcontinent and their collision and the final amalgamation of the Yangtze and Sino-Korean craton blocks in the Indosinian, and their age is consistent with or close to those of the Dabie ultrahigh-pressure and high-pressure metamorphic rocks, so have great tectonic significance.

  12. Investigation of silicate surface chemistry and reaction mechanisms associated with mass transport in geologic media

    International Nuclear Information System (INIS)

    The concentration and rate of transport of radionuclides through geologic media can be strongly influenced by the extent of sorption on aquifer surfaces. Over time intervals relevant to such transport processes, rock and mineral surfaces cannot be considered as inert, unreactive substrates but rather as groundwater/solidphase interfaces which are commonly in a state of natural or artificially induced disequilibrium. The goal of the present research is to define experimentally the type of water/rock interactions that will influence surface chemistry and hence sorption characteristics and capacities of natural aquifers. As wide a range of silicate minerals as possible was selected for study to represent rock-forming minerals in basalt, tuff, and granite. The minerals include K-feldspar, plagioclase feldspar, olivine, hornblende, biotite, and volcanic glass

  13. Impact of gneissic layering and localized incipient melting upon melt flow during experimental deformation of migmatites

    Science.gov (United States)

    Ganzhorn, A. C.; Trap, P.; Arbaret, L.; Champallier, R.; Fauconnier, J.; Labrousse, L.; Prouteau, G.

    2016-04-01

    In this study, we test experimentally the role of compositional layering as a key parameter for controlling melt flow in a natural migmatite during coaxial deformation. We performed in - situ pure-shear experiments on two natural gneisses. The first gneiss is weakly foliated with minerals homogenously distributed. The second gneiss shows a pronounced compositional layering of alternating quartz - feldspar - rich and biotite - muscovite - rich layers. Experimental conditions were selected to obtain homogeneous melt distribution in the homogeneous gneiss and heterogeneous melt distribution in the layered gneiss. Initial melt distribution is not modified by deformation in experiments on the homogeneous gneiss, implying that melting products did not migrate from their initiation sites. In contrast, melt flowed in shear zones or in inter-boudin positions during experimental deformation of the heterogeneous gneiss. These experiments attest to the strong influence of initial gneissic layering on melting pattern, melt segregation and flow during deformation of partially molten rocks.

  14. Petrographic characteristic of the sandstones of the upper paleocene-middle eocene aged in the Yildizli-Aydinkent (Ereğli-Konya area

    Directory of Open Access Journals (Sweden)

    A. Müjdat Özkan

    2002-03-01

    Full Text Available In the study area, Upper Paleocene - Middle Eocene aged Halkapınar formation, was formed in a shallow and deep marine environment. The lithologies of this formation are medium - thick bedded conglomerate, thin - thick bedded sandstone, thin - very thick bedded shale, thin - medium bedded marl with chert nodules and bands. In addition olistolithes of ophiolitic melange are found at the top of the sandstones, which includes basalt interbands. Yellowish gray, greenish gray, beige, gray colored sandstones include some sedimentary structures, namely ripple - marks, graded bedding, laminate, convolute lamination, current ripple, tool marks. Constituents of the sandstones are quartz, plagioclase, sanidine, orthoclase, fragments of sedimentary and methamorphic rocks, biotite, muscovite, opaque mineral and glauconite. The sandstones, which are not matured in terms of mineralogy and texture, are mainly cemented by calcite, clay matrix and minor iron oxide and glauconite matrix. The sandstones are named lithic arenite, lithic graywacke, feldspathic litharenite and litharenite.

  15. A study of uranium series disequilibrium in core profiles and mineral separates from the samples of Lac du Bonnet granite from the URL site, Pinawa, Manitoba, Canada

    International Nuclear Information System (INIS)

    Uranium series disequilibrium measurements of actinide activities and activity ratios have been used to study the geochemical history of Lac du Bonnet granite, from the URL site, Pinawa, Canada. Measurements on core profiles between fractured surfaces and the parent rock show that the granite underwent high temperature events several million years ago, followed by more recent low temperature events within the last million years. The main locations for the rock/water interaction and exchange of actinides are the fracture surfaces. The results of similar measurements on separated mineral phases show that the 'soft' minerals such as biotite and feldspar are more vulnerable to weathering than the 'hard' accessory minerals such as zircon. (author)

  16. Influence of microwaves on the leaching kinetics of uraninite from a low grade ore in dilute sulfuric acid.

    Science.gov (United States)

    Madakkaruppan, V; Pius, Anitha; T, Sreenivas; Giri, Nitai; Sarbajna, Chanchal

    2016-08-01

    This paper describes a study on microwave assisted leaching of uranium from a low-grade ore of Indian origin. The host rock for uranium mineralization is chlorite-biotite-muscovite-quartzo-feldspathic schist. The dominant presence of siliceous minerals determined leaching of uranium values in sulfuric acid medium under oxidizing conditions. Process parametric studies like the effect of sulfuric acid concentration (0.12-0.50M), redox potential (400-500mV), particle size (600-300μm) and temperature (35°-95°C) indicated that microwave assisted leaching is more efficient in terms of overall uranium dissolution, kinetics and provide relatively less impurities (Si, Al, Mg and Fe) in the leach liquor compared to conventional conductive leaching. The kinetics of leaching followed shrinking core model with product layer diffusion as controlling mechanism. PMID:27045621

  17. Geochemical, microtextural and petrological studies of the Samba prospect in the Zambian Copperbelt basement: a metamorphosed Palaeoproterozoic porphyry Cu deposit.

    Science.gov (United States)

    Master, Sharad; Mirrander Ndhlovu, N.

    2015-04-01

    Ever since Wakefield (1978, IMM Trans., B87, 43-52) described a porphyry-type meta-morphosed Cu prospect, the ca 50 Mt, 0.5% Cu Samba deposit (12.717°S, 27.833°E), hosted by porphyry-associated quartz-sericite-biotite schists in northern Zambia, there has been controversy about its origin and significance. This is because it is situated in the basement to the world's largest stratabound sediment-hosted copper province, the Central African Copperbelt, which is hosted by rocks of the Neoproterozoic Katanga Supergroup. Mineralization in the pre-Katangan basement has long played a prominent role in ore genetic models, with some authors suggesting that basement Cu mineralization may have been recycled into the Katangan basin through erosion and redeposition, while others have suggested that the circulation of fluids through Cu-rich basement may have leached out the metals which are found concentrated in the Katangan orebodies. On the basis of ca 490-460 Ma Ar-Ar ages, Hitzman et al. (2012, Sillitoe Vol., SEG Spec. Publ., 16, 487-514) suggested that Samba represents late-stage impregnation of copper mineralization into the basement, and that it was one of the youngest copper deposits known in the Central African Copperbelt. If the Samba deposit really is that young, then it would have post-dated regional deformation and metamorphism (560-510 Ma), and it ought to be undeformed and unmetamorphosed. The Samba mineralization consists of chalcopyrite and bornite, occurring as disseminations, stringers and veinlets, found in a zone >1 km along strike, in steeply-dipping lenses up to 10m thick and >150m deep. Our new major and trace element XRF geochemical data (14 samples) show that the host rocks are mainly calc-alkaline metadacites. Cu is correlated with Ag (Cu/Ag ~10,000:1) with no Au or Mo. Our study focused on the microtextures and petrology of the Samba ores. We confirm that there is alteration of similar style to that accompanying classical porphyry Cu mineralization

  18. Characterization of mineral phases of agricultural soil samples of Colombian coffee using Mössbauer spectroscopy and X-ray diffraction

    Science.gov (United States)

    Rodríguez, Humberto Bustos; Lozano, Dagoberto Oyola; Martínez, Yebrayl Antonio Rojas; Pinilla, Marlene Rivera; Alcázar, German Antonio Pérez

    2012-03-01

    Soil chemical analysis, X-ray diffraction (XRD) and Mössbauer spectrometry (MS) of 57Fe were used to characterize mineral phases of samples taken from the productive layer (horizon A) of agricultural coffee soil from Tolima (Colombia). Chemical analysis shows the chemical and textural parameters of samples from two different regions of Tolima, i.e., Ibagué and Santa Isabel. By XRD phases like illite (I), andesine (A) and quartz (Q) in both samples were identified. The quantity of these phases is different for the two samples. The MS spectra taken at room temperature were adjusted by using five doublets, three of them associated to Fe + 3 type sites and the other two to Fe + 2 type sites. According to their isomer shift and quadrupole splitting the presence of phases like illite (detected by DRX), nontronite and biotite (not detected by XRD) can be postulated.

  19. Evidence of heterogeneous crustal origin for the Pan-African Mbengwi granitoids and the associated mafic intrusions (northwestern Cameroon, central Africa)

    Science.gov (United States)

    Mbassa, Benoît Joseph; Kamgang, Pierre; Grégoire, Michel; Njonfang, Emmanuel; Benoit, Mathieu; Itiga, Zénon; Duchene, Stéphanie; Bessong, Moïse; Nguet, Pauline Wonkwenmendam; Nfomou, Ntepe

    2016-02-01

    The Mbengwi plutonics consist of intermediate to felsic granitoids forming a continuous magmatic series from monzonite to granite and mafic intrusions. Their mineralogical composition consists of quartz, plagioclases, K-feldspars, biotite, muscovite, and amphibole. The accessory phase includes opaque minerals + titanite ± apatite ± zircon, while secondary minerals are pyrite, phengite, chlorite, epidote, and rarely calcite. These plutonics are assigned high-K calc-alkaline to shoshonitic series, metaluminous to weakly peraluminous and mostly belong to an I-type suite (A/CNK = 0.63-1.2). They are typically post-collisional, with a subduction signature probably being inherited from their protoliths emplaced during the subduction phase. The Sr and Nd isotopic data evidence that these plutonics result from melting of the lower continental crust with variable contribution of the oceanic crust. Their geochemical features are similar to those of western Cameroon granitoids related to the Pan-African D1 event in Cameroon.

  20. Preservation of ancient impact ages on the R chondrite parent body: 40Ar/39Ar age of hornblende-bearing R chondrite LAP 04840

    Science.gov (United States)

    Righter, K.; Cosca, M. A.; Morgan, L. E.

    2016-07-01

    The hornblende- and biotite-bearing R chondrite LAP 04840 is a rare kind of meteorite possibly containing outer solar system water stored during metamorphism or postshock annealing deep within an asteroid. Because little is known regarding its age and origin, we determined 40Ar/39Ar ages on hornblende-rich separates of the meteorite, and obtained plateau ages of 4340(±40) to 4380(±30) Ma. These well-defined plateau ages, coupled with evidence for postshock annealing, indicate this meteorite records an ancient shock event and subsequent annealing. The age of 4340-4380 Ma (or 4.34-4.38 Ga) for this and other previously dated R chondrites is much older than most impact events recorded by ordinary chondrites and points to an ancient event or events that predated the late heavy bombardment that is recorded in so many meteorites and lunar samples.

  1. Petrographic and mineralogical features of the uraniferous pink granites in the north eastern desert of egypt

    International Nuclear Information System (INIS)

    The present work is concerned with the petrological, mineralogical and geochemical studies of some uranium bearing younger granites in the north eastern desert of egypt particularly Gebel Gattar area. The area around Gebel Gattar comprises the following rock units (starting from the oldest): meta volcanic, diorite-grano-diorite complex- Dokhan volcanics- Hammamat sediments, younger granites and dykes. The most significant structural features are represented by NNE-ENE dominantly trending faults and joints. Petrographicaly, the pink granites are divided into normal and mineralized (uraniferous) granites. Normal granites are classified into three types; a) leucocratic perthitic granite, b) hornblende- biotite perthitic granite and c) two feldspars perthitic granite. Mineralized granites are sheared, deformed, pinkish brown in colour and strongly altered. A remarkable secondary uranium mineralization has been recorded along fault and fracture zones

  2. K-Ar ages of plutonic rocks in the Lassiter Coast area, Antarctica

    Science.gov (United States)

    Mehnert, Harald H.; Rowley, Peter D.; Schmidt, Dwight L.

    1975-01-01

    Numerous middle Cretaceous stocks and small batholiths intruded Middle and Upper Jurassic sedimentary and volcanic rocks in the Lassiter Coast area of the southern Antarctic Peninsula. To establish the age of the quartz diorite and granodiorite plutonic events, five plutons were dated by the K-Ar method. The results indicate a timespan of about 20 m.y. for the emplacement of the plutons and a minimum age of 120 m.y. for the deformation of the sedimentary (Latady Formation) and volcanic rocks. Three of the more silicic plutons have concordant biotite and hornblende ages of 100 and 106 m.y.; two discordant ages of about 118 m.y. were obtained on the more mafic plutons. Petrographically, chemically, and geochronologically, the plutons of the southern to central Lassiter Coast are similar to the calc-alkaline suite of igneous rocks of the Andes of Patagonia, the Antarctic Peninsula, and eastern Ellsworth Land.

  3. Characterization of mineral phases of agricultural soil samples of Colombian coffee using Moessbauer spectroscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Humberto Bustos, E-mail: hbustos@ut.edu.co; Lozano, Dagoberto Oyola; Martinez, Yebrayl Antonio Rojas; Pinilla, Marlene Rivera [Universidad del Tolima, Grupo Ciencia de Materiales y Tecnologia en Plasma (Colombia); Alcazar, German Antonio Perez [Universidad del Valle, Grupo Metalurgia Fisica y Teoria de las Transiciones de Fase (Colombia)

    2012-03-15

    Soil chemical analysis, X-ray diffraction (XRD) and Moessbauer spectrometry (MS) of {sup 57}Fe were used to characterize mineral phases of samples taken from the productive layer (horizon A) of agricultural coffee soil from Tolima (Colombia). Chemical analysis shows the chemical and textural parameters of samples from two different regions of Tolima, i.e., Ibague and Santa Isabel. By XRD phases like illite (I), andesine (A) and quartz (Q) in both samples were identified. The quantity of these phases is different for the two samples. The MS spectra taken at room temperature were adjusted by using five doublets, three of them associated to Fe{sup + 3} type sites and the other two to Fe{sup + 2} type sites. According to their isomer shift and quadrupole splitting the presence of phases like illite (detected by DRX), nontronite and biotite (not detected by XRD) can be postulated.

  4. Tectono-metamorphic evolution of a hot orogen during Gondwanaland assembly: a case study from Palni hills metapelite granulite, south India

    Science.gov (United States)

    Bhadra, S.; Nasipuri, P.

    2012-04-01

    This study deals with the tectono-metamorphic evolution of Sapphirine-cordierite-bearing metapelite granulite at Perumalmalai, south India, that occurs as enclave within deformed migmatitic enderbite gneiss of Kodaikanal massif, Madurai granulite block (MB), south India. Pre-peak mineral paragenesis is represented by an inclusion assemblage of sillimanite + plagioclase + Ti-rich biotite ±quartz in Al-rich orthopyroxene. Dehydration melting of biotite marked the onset of ultra-high temperature metamorphism (M1A, ~1000 °C, 10 Kbar). Early stage of retrograde metamorphism (M1B) is characterized by the development of type1-symplectite and corona textures. In type1-symplectite an innermost vermicular sapphirine (Spr - XMg: 0.90, Al/Si: 6.17) - cordierite (Crd) symplectite on sillimanite is followed by cordierite (XMg: 0.94) moat. A meso-perthitic layer laced the interface between cordierite moat and orthopyroxene porphyroblast, the latter showing prominent rim-ward decrease in Al2O3 (up to 3 wt%). The cordierite rim at the interface between sillimanite and orthopyroxene characterizes corona texture. Type1-symplectite and corona domains are circumnavigated by Ti-poor biotite (TiO2: ~3.2 wt%) showing shape preferred alignment, and set in a feldspar matrix showing wide compositional range. By implication, leucosome crystallization was possibly prolonged and enhanced by deformation. Type1-symplectite and corona textures were resulted from melt-solid interaction or silica-metasomatism during early stage of retrogression, Opx+Sil = Spr+Crd → Opx+Sil+melt = Crd. The retrograde metamorphism is constrained at 9 kbar and 950°C, implying an early stage of near-isothermal decompression. Late stage retrograde metamorphism (M2) is also characterized by symplectite textures, type2-symplectite, with innermost sapphirine-cordierite symplectite followed by cordierite corona. Sapphirine in type2-symplectite domain (XMg: 0.89; Al/Si: 5.92), which occurs as inclusion in Opx, is

  5. Correlation of upper Llandovery–lower Wenlock bentonites in the När (Gotland, Sweden and Ventspils (Latvia drill cores: role of volcanic ash clouds and shelf sea currents in determining areal distribution of bentonite

    Directory of Open Access Journals (Sweden)

    Tarmo Kiipli

    2012-11-01

    Full Text Available Study of volcanic ash beds using biostratigraphy, sanidine composition and immobile elements within bentonites has manifested several well-established and some provisional correlations between Gotland and East Baltic sections. Energy dispersive X-ray fluorescence microanalysis of phenocrysts has revealed bentonites containing Mg-rich or Fe-rich biotite. Sanidine phenocrysts contain, in addition to a major Na and K component, often a few per cent of Ca and Ba. On the basis of new correlations the mapping of the distribution areas of bentonites has been extended from the East Baltic to Gotland. The bentonite distribution can be separated into two parts in North Latvia–South Estonia, indicating the existence of shelf sea currents in the Baltic Silurian Basin.

  6. The mafic dyke swarm of Uaua (Brazil): geological and petrographical aspects

    International Nuclear Information System (INIS)

    The Uaua mafic dike swarm stands out as one of the most extensive swarms in the Sao Francisco craton. These dikes crop out around the town of Uaua (State of Bahia) and to the east near the Rio Capim greenstone belt. The dikes intrude the Archean basement which is composed of medium-to high-grade gneisses and migmatites. Table 1 shows the geochronological results for basement rocks, which have yielded ages between 2,730-3,016 m.y. (Tb-Sr,whole rock isochron) indicating a Late Archean evolution for these rocks. On the other hand, available 40 Ar-39 Ar (biotite) and K-Ar (amphibole) determinations for basement rocks yield Early Proterozoic ages, the result of overprinting of the Transamazonico orogenic cycle. (author)

  7. Amphiboles of basic schists in the Sanbagawa metamorphic terrain of the Kodama-Nagatoro area, Kanto mountains. Kanto sanchi Kodamater dot Nagatoro chiiki no Sanbagawa enkisei hengan no kakusenseki

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, M.; Funakoshi, R. (Hitachi Ltd., Tokyo (Japan))

    1991-10-01

    On the basis of mineral parageneses and the graphitizing degrees of pelitic and psammitic schists, the Sambagawa metamorphic terrain of the Kodama-Nagatoro area in Kanto mountains is divided into three zones, i.e. Zone l (chlorite zone), Zone 2 (garnet zone) and Zone 3 (biotite zone) in the order of lower temperature. Amphibole of basic schists is actinolite in Zone 1. The range of composition variance widens gradually with the increase in the temperature, ranging from actinolite to hornblend in Zone 2, and from actinolite to barroisite through actinolitic hornblend in Zone 3. The amount of Al in amphiboles increases gradually with the increase in temperature. The lowest value becomes higher with the widening of the range of variation towards higher side. The metamorphosis in this area is assumed to have taken place principally under increasing temperature with slight increase in pressure. 21 refs., 8 figs.

  8. Tephra records from abyssal sediments off western Sumatra in recent 135 ka:evidence from Core IR-GC1

    Institute of Scientific and Technical Information of China (English)

    QIU Zhongyan; HAN Xiqiu; JIN Xianglong; WANG Yejian; ZHU Jihao

    2014-01-01

    Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with theδ18O-based age, it is suggested that ash Layer A is cor-related to the youngest Toba tuff (YTT), Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic erup-tion event.

  9. The infrared use on boron characterization from pegmatites ores

    International Nuclear Information System (INIS)

    The study of minerals of zoned pegmatites outcroping near of Governador Valadares, Minas Gerais State, using infrared absorption spectrometry and X-ray diffraction, allowed the identification of B proxing for Si in the tetrahedral sites of some minerals, such as muscovite, biotite, feldspars, quartz and garnets. The valence balancing was achieved with one monolayer of water in the structure as revealed by infrared absorption too. Infrared absorption is a very important research tool to disclose the proxing of B for Si in geological systems where this element occurs only at traces levels as we found in samples from the Ferreirinha pegmatite quarry. Only the mineral phases collected close to the quartz core show the absorption bands linked to the stretching of the B-O bond and to the H2O monolayer. (author)

  10. Microstructures, deformation mechanisms and seismic properties of a Palaeoproterozoic shear zone: The Mertz shear zone, East-Antarctica

    Science.gov (United States)

    Lamarque, Gaëlle; Bascou, Jérôme; Maurice, Claire; Cottin, Jean-Yves; Riel, Nicolas; Ménot, René-Pierre

    2016-06-01

    The Mertz shear zone (MSZ) is a lithospheric scale structure that recorded mid-crustal deformation during the 1.7 Ga orogeny. We performed a microstructural and crystallographic preferred orientation (CPO) study of samples from both mylonites and tectonic boudins that constitute relics of the Terre Adélie Craton (TAC). The deformation is highly accommodated in the MSZ by anastomosed shear bands, which become more scattered elsewhere in the TAC. Most of the MSZ amphibolite-facies mylonites display similar CPO, thermal conditions, intensity of deformation and dominant shear strain. Preserved granulite-facies boudins show both coaxial and non-coaxial strains related to the previous 2.45 Ga event. This former deformation is more penetrative and less localized and shows a deformation gradient, later affected by a major phase of recrystallization during retrogression at 2.42 Ga. Both MSZ samples and granulite-facies tectonic boudins present microstructures that reflect a variety of deformation mechanisms associated with the rock creep that induce contrasted CPO of minerals (quartz, feldspar, biotite, amphibole and orthopyroxene). In particular, we highlight the development of an "uncommon" CPO in orthopyroxene from weakly deformed samples characterized by (010)-planes oriented parallel to the foliation plane, [001]-axes parallel to the stretching lineation and clustering of [100]-axes near the Y structural direction. Lastly, we computed the seismic properties of the amphibolite and granulite facies rocks in the MSZ area in order to evaluate the contribution of the deformed intermediate and lower continental crust to the seismic anisotropy recorded above the MSZ. Our results reveal that (i) the low content of amphibole and biotite in the rock formations of the TAC, and (ii) the interactions between the CPO of the different mineralogical phases, generate a seismically isotropic crust. Thus, the seismic anisotropy recorded by the seismic stations of the TAC, including the

  11. Comparison of inorganic ion exchange materials for removing cesium, strontium, and transuranic elements from K-basin water

    International Nuclear Information System (INIS)

    The work presented in this report was conducted by the Pacific Northwest National Laboratory (PNNL) under the Efficient Separations and Crosscutting Program (ESP), Office of Science and Technology, U.S. Department of Energy (DOE). The objective of this work was to investigate radionuclide uptake by several newly produced ion exchange materials under actual waste conditions, and to compare the performance of those materials with that of commercially available ion exchangers. The equilibrium uptake data presented in this report are useful for identifying potential materials that are capable of removing cesium and strontium from 105-KE Basin water. The data show the relative selectivities of the ion exchange materials under similar operating conditions. Additional flow studies are needed to predict material capacities and to develop complete ion exchange process flow sheets. The materials investigated in this study include commercially available ion exchangers such as IONSIV reg-sign IE-911 (manufactured by UOP), clinoptilolite (a naturally occurring zeolite), and materials produced on an experimental basis by AlliedSignal (biotites and nonatitanates), 3M (hexacyanoferrates), Selion Technologies, Inc. (hexacyanoferrates and titanates), and Texas A ampersand M University (pharmacosiderites, biotites, and nonatitanates). In all, the performance of 14 ion exchange materials was evaluated at two solution-to-exchanger mass ratios (i.e., 104 and 105) using actual 105-KE Basin water. Evaluation consisted of determining cesium and strontium batch distribution coefficients, loading, and decontamination factors. Actual 105-KE Basin water was obtained from a sample collected during the sludge dissolution work conducted by PNNL in FY 1996. This sample was taken from the bottom of the basin and contained significantly higher concentrations of the radioactive constituents than do samples taken from the top of the basin

  12. Comparison of inorganic ion exchange materials for removing cesium, strontium, and transuranic elements from K-basin water

    Energy Technology Data Exchange (ETDEWEB)

    Brown, G.N.; Bontha, J.R.; Carson, K.J.; Elovich, R.J.; DesChane, J.R.

    1997-10-01

    The work presented in this report was conducted by the Pacific Northwest National Laboratory (PNNL) under the Efficient Separations and Crosscutting Program (ESP), Office of Science and Technology, U.S. Department of Energy (DOE). The objective of this work was to investigate radionuclide uptake by several newly produced ion exchange materials under actual waste conditions, and to compare the performance of those materials with that of commercially available ion exchangers. The equilibrium uptake data presented in this report are useful for identifying potential materials that are capable of removing cesium and strontium from 105-KE Basin water. The data show the relative selectivities of the ion exchange materials under similar operating conditions. Additional flow studies are needed to predict material capacities and to develop complete ion exchange process flow sheets. The materials investigated in this study include commercially available ion exchangers such as IONSIV{reg_sign} IE-911 (manufactured by UOP), clinoptilolite (a naturally occurring zeolite), and materials produced on an experimental basis by AlliedSignal (biotites and nonatitanates), 3M (hexacyanoferrates), Selion Technologies, Inc. (hexacyanoferrates and titanates), and Texas A&M University (pharmacosiderites, biotites, and nonatitanates). In all, the performance of 14 ion exchange materials was evaluated at two solution-to-exchanger mass ratios (i.e., 10{sup 4} and 10{sup 5}) using actual 105-KE Basin water. Evaluation consisted of determining cesium and strontium batch distribution coefficients, loading, and decontamination factors. Actual 105-KE Basin water was obtained from a sample collected during the sludge dissolution work conducted by PNNL in FY 1996. This sample was taken from the bottom of the basin and contained significantly higher concentrations of the radioactive constituents than do samples taken from the top of the basin.

  13. Leucogranites of the Teton Range, Wyoming: A record of Archean collisional orogeny

    Science.gov (United States)

    Frost, Carol D.; Swapp, Susan M.; Frost, B. Ronald; Finley-Blasi, Lee; Fitz-Gerald, D. Braden

    2016-07-01

    Leucogranitic rocks formed by crustal melting are a prominent feature of collisional orogens of all ages. This study describes leucogranitic gneisses associated with an Archean collisional orogeny preserved in the Teton Range of northwestern Wyoming, USA. These leucogneisses formed at 2.68 Ga, and initial Nd isotopic compositions suggest they are derived from relatively juvenile sources. Two distinct groups of leucogneisses, both trondhjemitic, are identified on the basis of field relations, petrology, and geochemistry. The Webb Canyon gneiss forms large, sheet-like bodies of hornblende biotite trondhjemite and granodiorite. This gneiss is silica-rich (SiO2 = 70-80%), strongly ferroan, comparatively low in alumina, and is characterized by high Zr and Y, low Sr, and high REE contents that define "seagull"-shaped REE patterns. The Bitch Creek gneiss forms small sills, dikes, and plutons of biotite trondhjemite. Silica, Zr, Y, and REE are lower and alumina and Sr are higher than in the Webb Canyon gneiss. These differences reflect different melting conditions: the Webb Canyon gneiss formed by dehydration melting in which amphibole and quartz breaks down, accounting for the low alumina, high FeO, high silica content and observed trace element characteristics. The Bitch Creek gneiss formed by H2O-excess melting in which plagioclase breaks down leaving an amphibole-rich restite, producing magmas higher in alumina and Sr and lower in FeO and HREE. Both melt mechanisms are expected in collisional environments: dehydration melting accompanies gravitational collapse and tectonic extension of dramatically thickened crust, and water-excess melting may occur when collision places a relatively cool, hydrous lower plate beneath a hotter upper plate. The Archean leucogranitic gneisses of the Teton Range are calcic trondhjemites and granodiorites whereas younger collisional leucogranites typically are true granites. The difference in leucogranite composition reflects the

  14. Mineral deformation and subglacial processes on ice-bedrock interface of Hailuogou Glacier

    Institute of Scientific and Technical Information of China (English)

    LIU GengNian; CHEN YiXin; ZHANG Yue; FU HaiRong

    2009-01-01

    Hailuogou Glacier is located in a warm and humid maritime environment. It is large and moves very fast.The bottom of the glacier slides intensively and the temperature at the bottom approaches the pressure melting point. Therefore,there are abundant melting water and debris which act as effective "grinding tools"for glacial abrasion. Polarizing microscope is used to observe the mineral deformation characteristics on the ice-bedrock interface. It is found that feldspar,quartz,hornblende and biotite are exposed to deformation,fracture and chemical alteration to various extents. Bending deformation is common for biotite,due to their lattice characteristics,and the bending orientations are mostly the same as the glacier flow. Bending deformation also occurs in a few hornblendes. High-angle tension fracture and low-angle shear fracture are common for quartz and feldspar,some of them are totally crushed (mylonizations) due to their rigidity. Thus,all the abrasion,quarrying,subglacial water action and subglacial dissolution processes at the bottom of the glacier are verified at the micro-scale level.Mineral deformation and fracture are the basic subglacial erosion mechanisms. The abrasion thickness is 30-90 μm for each time and the average is 50 μm. Most of the debris are silt produced by glacial abrasion. The extent of mineral deformation and fracture decreases drastically downwards beneath the bedrock surface. The estimated erosion rate is about 2.2-11.4 mm/a,which is similar to that of other maritime alpine glaciers,smaller than that of large-scale piedmont glaciers In Alaska (10-30 mm/a),and larger than that of continental glaciers (0.1-1.0 mm/a). The type and size of a glacier are the main factors that influence its erosion rate.

  15. Fluoride abundance and controls in fresh groundwater in Quaternary deposits and bedrock fractures in an area with fluorine-rich granitoid rocks.

    Science.gov (United States)

    Berger, Tobias; Mathurin, Frédéric A; Drake, Henrik; Åström, Mats E

    2016-11-01

    This study focuses on fluoride (F(-)) concentrations in groundwater in an area in northern Europe (Laxemar, southeast Sweden) where high F(-) concentrations have previously been found in surface waters such as streams and quarries. Fluoride concentrations were determined over time in groundwater in the Quaternary deposits ("regolith groundwater"), and with different sampling techniques from just beneath the ground surface to nearly -700m in the bedrock (fracture) groundwater. A number of potential controls of dissolved F(-) were studied, including geological variables, mineralogy, mineral chemistry and hydrology. In the regolith groundwater the F(-) concentrations (0.3-4.2mg/L) were relatively stable over time at each sampling site but varied widely among the sampling sites. In these groundwaters, the F(-) concentrations were uncorrelated with sample (filter) depth and the water table in meters above sea level (masl), with the thicknesses of the groundwater column and the regolith, and with the distribution of soil types at the sampling sites. Fluoride concentrations were, however, correlated with the anticipated spatial distribution of erosional material (till) derived from a F-rich circular granite intrusion. Abundant release of F(-) from such material is thus suggested, primarily via dissolution of fluorite and weathering of biotite. In the fresh fracture groundwater, the F(-) concentrations (1.2-7.4mg/L) were generally higher than in the regolith groundwater, and were uncorrelated with depth and with location relative to the granite intrusion. Two mechanisms explaining the overall high F(-) levels in the fracture groundwater were addressed. First, weathering/dissolution of fluorite, bastnäsite and apophyllite, which are secondary minerals formed in the fractures during past hydrothermal events, and biotite which is a primary mineral exposed on fracture walls. Second, long water-residence times, favoring water-rock interaction and build-up of high dissolved F

  16. Identification and characterization of phyllosilicate minerals from Republic of Macedonia by vibrational spectroscopy

    International Nuclear Information System (INIS)

    Identification and characterization of several phyllosilicate minerals collected from the Republic of Macedonia: Mg3Si2O5(OH)4; antigorite, (Mg,Fe2+)3Si2O5(OH)4; talc, Mg3Si4O10(OH)2; clinochlore, (Mg,Fe2+)5Al(Si3Al)O10(OH)8; cymrite, BaAl2Si2O8·H2O; muscovite, KAl2(Si3Al)O10(OH,F)2; phlogopite, KMg3(Si3Al)O10(F, OH)2; montmorillonite, (Na,Ca)0..33(Al, Mg)2Si4O10(OH)2·nH2O; sherindanite, (Mg,Al)6(Si,Al)4O10(OH)8 and biotite, K(Mg,Fe2+)3AlSiO10(OH,F)2 is performed using their infrared and Raman vibrational spectra. In contrast to Raman spectra, the above-mentioned minerals showed IR spectral similarities in the region bellow 1200 cm-1 mainly due to their common structural characteristics. The bands appearing in the 1100-900 cm-1 spectral region were prescribed to ν(Si-O-Si)modes, whereas most of the lower-frequency bands were interpreted as either δ(OH) or δ(Si-O-Si) vibrations. The presence of sharp peak at 1630 cm-1, registered only in the infrared spectra of cymrite and montmorillonite, enables to discriminate between hydroxide and water-containing minerals. Various types of ion substitutions, which appear in this group of minerals, sometimes could led to wrong identification. Therefore, the authenticity of the three samples, muscovite (Nezhlevo), biotite (Chanishte) and sherindanite (Sivets), was checked with results obtained from chemical composition analysis. (Author)

  17. A study on the ground water flow and hydrogeochemical interaction in fractured rock masses

    International Nuclear Information System (INIS)

    A study site, the Precambrian gneiss complex in the vincinity of Chungyang has been investigated by geologic surface mapping, tunnel mapping and core drilling with chemical analysis and microscopic observation of rock samples and fracture filling materials. Four boreholes at depths between 50 and 200m were drilled. They are located in a potential fracture zone, which was selected based on the topographic characterisitcs and the fracture survey data. The hydraulic characteristics are described based on the results of constant pressure injection test and cross hole test. In the single hole test, the test sections varied between 1 and 5 m. The hydraulic conductivity of local fracture zones ranges from 1xlO-5 to lxlO-7 m/sec whereas that of the intact rock within the depth of 50 m is in the range of 7xlO-8 to 8xlO-9 m/sec. The field dispersivity values obtained from an injection phase range from 0.15 to 4.5 m at varying depths. The whole thickness dispersivity on the 18 m section obtained from a withdrawal phase is 0.4 m. The dispersion test in two well non-circulation mode was carried out along a single fracture set at depth between 11.5-14.5m. The longitudinal dispersivity obtained from the two well test is 8.14 m. The identified minerals of host rocks are quartz, K-feldspar,plagioclase, biotite, muscovite, sericite, chlorite, calcite, pyrite, zircon and opaque minerals. The primary minerals such as feldspar and biotite are highly altered into sericite and chlorite respectively. The fracture-filling materials from core samples identified by as calcite, kaolinite, smectite, chlorite, illitite, quartz, pyrite with fe- and Mn-oxides. (Author)

  18. Contrasted crustal sources as defined by whole-rock and Sr-Nd-Pb isotope geochemistry of neoproterozoic early post-collisional granitic magmatism within the Southern Brazilian Shear Belt, Camboriú, Brazil

    Science.gov (United States)

    Florisbal, Luana Moreira; de Assis Janasi, Valdecir; de Fátima Bitencourt, Maria; Stoll Nardi, Lauro Valentim; Heaman, Larry M.

    2012-11-01

    The early phase of post-collisional granitic magmatism in the Camboriú region, south Brazil, is represented by the porphyritic biotite ± hornblende Rio Pequeno Granite (RPG; 630-620 Ma) and the younger (˜610 Ma), equigranular, biotite ± muscovite Serra dos Macacos Granite (SMG). The two granite types share some geochemical characteristics, but the more felsic SMG constitutes a distinctive group not related to RPG by simple fractionation processes, as indicated by its lower FeOt, TiO2, K2O/Na2O and higher Zr Al2O3, Na2O, Ba and Sr when compared to RPG of similar SiO2 range. Sr-Nd-Pb isotopes require different sources. The SMG derives from old crustal sources, possibly related to the Paleoproterozoic protoliths of the Camboriú Complex, as indicated by strongly negative ɛNdt (-23 to -24) and unradiogenic Pb (e.g., 206Pb/204Pb = 16.0-16.3; 207Pb/204Pb = 15.3-15.4) and confirmed by previous LA-MC-ICPMS data showing dominant zircon inheritance of Archean to Paleoproterozoic age. In contrast, the RPG shows less negative ɛNdt (-12 to -15) and a distinctive zircon inheritance pattern with no traces of post-1.6 Ga sources. This is indicative of younger sources whose significance in the regional context is still unclear; some contribution of mantle-derived magmas is indicated by coeval mafic dykes and may account for some of the geochemical and isotopic characteristics of the least differentiated varieties of the RPG. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas despite their emplacement within a low-strain zone. It may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of Paleoproterozoic orthogneisses from the Camboriú Complex.

  19. Post-collisional potassic granitoids from the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review

    Science.gov (United States)

    Küster, Dirk; Harms, Ulrich

    1998-12-01

    Potassic metaluminous granitoids with enrichments of HFS elements constitute part of widespread post-collisional magmatism related to the Late Neoproterozoic Pan-African orogeny in northeastern Africa (Sudan, Ethiopia, Somalia) and Madagascar. The plutons were emplaced between 580 and 470 Ma and comprise both subsolvus and hypersolvus biotite-granite, biotite-hornblende-granite, quartz-monzonite and quartz-syenite. Pyroxene-bearing granitoids are subordinate. Basic dikes and enclaves of monzodioritic composition are locally associated with the granitoid plutons. Granitoids emplaced in pre-Neoproterozoic crust have Sr i-ratios between 0.7060 and 0.7236 and ɛNd( t) values between -15.8 and -5.6 while those emplaced in, or close to the contact with, juvenile Neoproterozoic crust have lower Sr i-ratios (0.7036-0.7075) and positive ɛNd( t) values (4.6). However, it is unlikely that the potassic granitoids represent products of crustal melting alone. The association with basic magmas derived from subduction-modified enriched mantle sources strongly suggests that the granitoids represent hybrid magmas produced by interaction and mixing of mantle and crust derived melts in the lower crust. The most intense period of this potassic granitoid magmatism occurred between 585 and 540 Ma, largely coeval with HT granulite facies metamorphism in Madagascar and with amphibolite facies retrogression in northeastern Africa (Somalia, Sudan). Granitoid magmatism and high-grade metamorphism are probably both related to post-collisional lithospheric thinning, magmatic underplating and crustal relaxation. However, the emplacement of potassic granites continued until about 470 Ma and implies several magmatic pulses associated with different phases of crustal uplift and cooling. The potassic metaluminous granites are temporally and spatially associated with post-collisional high-K calc-alkaline granites with which they share many petrographical, geochemical and isotopical similarities

  20. Alkali-calcic and alkaline post-orogenic (PO) granite magmatism: petrologic constraints and geodynamic settings

    Science.gov (United States)

    Bonin, Bernard; Azzouni-Sekkal, Abla; Bussy, François; Ferrag, Sandrine

    1998-12-01

    The end of an orogenic Wilson cycle corresponds to amalgamation of terranes into a Pangaea and is marked by widespread magmatism dominated by granitoids. The post-collision event starts with magmatic processes still influenced by subducted crustal materials. The dominantly calc-alkaline suites show a shift from normal to high-K to very high-K associations. Source regions are composed of depleted and later enriched orogenic subcontinental lithospheric mantle, affected by dehydration melting and generating more and more K- and LILE-rich magmas. In the vicinity of intra-crustal magma chambers, anatexis by incongruent melting of hydrous minerals may generate peraluminous granitoids bearing mafic enclaves. The post-collision event ends with emplacement of bimodal post-orogenic (PO) suites along transcurrent fault zones. Two suites are defined, (i) the alkali-calcic monzonite-monzogranite-syenogranite-alkali feldspar granite association characterised by [biotite+plagioclase] fractionation and moderate [LILE+HFSE] enrichments and (ii) the alkaline monzonite-syenite-alkali feldspar granite association characterised by [amphibole+alkali feldspar] fractionation and displaying two evolutionary trends, one peralkaline with sodic mafic mineralogy and higher enrichments in HFSE than in LILE, and the other aluminous biotite-bearing marked by HFSE depletion relative to LILE due to accessory mineral precipitation. Alkali-calcic and alkaline suites differ essentially in the amounts of water present within intra-crustal magma chambers, promoting crystallisation of various mineral assemblages. The ultimate enriched and not depleted mantle source is identical for the two PO suites. The more primitive LILE and HFSE-rich source rapidly replaces the older orogenic mantle source during lithosphere delamination and becomes progressively the thermal boundary layer of the new lithosphere. Present rock compositions are a mixture of major mantle contribution and various crustal components

  1. The production of intermediate magmas through magma mixing and commingling: Evidence from the Hoover Dam Volcanics, Mohave County, Arizona and Clark County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Mills, J.G. Jr. (Univ. of Nevada, Las Vegas, NV (United States). Dept. of Geoscience)

    1993-04-01

    The Hoover Dam Volcanic section ([approximately]14 Ma) is composed of the reversely-zoned dacitic tuff of Hoover Dam, Switchyard basaltic andesite, Sugarloaf dacite, Black Canyon dacite and Kingman Wash basaltic andesite (Mills, 1985). The origin of this suite is best explained by the commingling and mixing of end-member mafic and felsic magmas. These end-member magmas were most likely formed by partial melting of the mantle and subsequent advective heating and melting of the crust respectively. Textural evidence for these processes is observed in the Black Canyon dacite which contains enclaves of basaltic andesite, and, in the Paint Pots pluton which contains commingled basaltic andesite and monzonite. The Black Canyon dacite is a biotite (4%), homblende (1%) and plagioclase 10% phyric dacite flow which contains up to 5% enclaves of basaltic andesite. The enclaves contain 54 wt% SiO[sub 2], 7.22 ppm Tl, 65 ppm Rb, 1,274 ppm Sr and 1,810 ppm Ba. The gray to purplish-red enclaves have crenulate margins, are commonly vesiculated and contain phenocrysts of biotite (< 1%), hornblende ([much lt]1%), plagioclase (1%) and clinopyroxene( ) (2%). Chemically, the enclaves are distinct from the Switchyard and Kingman Wash basaltic andesites. The enclaves most likely represent a more primitive magma from which the Switchyard and Kingman Wash basaltic andesites were derived. These two units were subsequently chemically modified by mixing with crustal melt and/or crystal fractionation. The presence of a small, clinopyroxenite xenolith (clinopyroxene 90%, garnet 5%, plagioclase 4%) within one of the enclaves indicates an upper mantle source for the enclave magma.

  2. Genetic relationship of high-Mg dioritic pluton to iron mineralization: A case study from the Jinling skarn-type iron deposit in the North China Craton

    Science.gov (United States)

    Jin, Ziliang; Zhang, Zhaochong; Hou, Tong; Santosh, M.; Han, Liu

    2015-12-01

    The Jinling complex is spatially and temporally associated with the Jinling skarn-type iron deposit. The complex is composed of biotite diorite, hornblende diorite, monzonite and quartz diorite. U-Pb dating of zircons from the biotite diorite and monzonite using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yields ages of 126 ± 1.9 Ma and 128 ± 1.4 Ma, respectively. The unaltered rocks in the complex are characterized by variable contents of SiO2 (54.6-65.3 wt.%), MgO (2.7-9.2 wt.%), total FeO (3.5-8.8 wt.%), Na2O + K2O (5.2-8.9 wt.%), high Mg# values (73-88), Cr (103-452 ppm) and Ni (49-212 ppm) contents. The altered monzonite has lower MgO (2.1-3.7 wt.%), total FeO (1.2-2.6 wt.%) and higher Na2O + K2O (8.5-9.9 wt.%) contents. The initial (87Sr/86Sr)t ranges from 0.70450 to 0.70555 and εNd(t) shows a range of -3.0 to -8.0. The geochemical characteristics suggest that the primary magma witnessed the interaction between the partial melts of relatively oxidized delaminated ancient crust and mantle peridotite. Fractional crystallization and crustal contamination during the magmatic ascent and emplacement are also indicated. The Jinling skarn-type Fe deposit is of hydrothermal origin and the Fe enrichment can be ascribed to multiple factors. The delaminated ancient crustal source contributed to the high oxygen fugacity of the primary magma. Two-stage Fe-enrichment process involving fractional crystallization of the primary magma giving rise to high Cl and Fe contents in the magmatic hydrothermal fluid and later Fe-leaching process, accounts for the high-grade ore bodies.

  3. Geochronology, geochemistry and tectonic implications of Late Triassic granites in the Mongolian Altai Mountains

    Science.gov (United States)

    Dash, Batulzii; Boldbaatar, Enkhjargal; Zorigtkhuu, Oyun-Erdene; Yin, An

    2016-03-01

    Although the closure of the Paleo-Asian Ocean in western China and western Mongolia occurred in the Late Carboniferous and Early Permian, widespread intra-continental magmatism continued to occur across this region from the Late Permian to the end of the Triassic. In this study we document field relationships and geochemical characterization of a Late Triassic felsic intrusive complex in the western Mongolian Altai. The plutonic complex occurs as sills, dikes, and small stocks and its composition varies from biotite granite, two-mica granite, to leucogranite. Structurally, the plutonic complex occurs in the hanging wall of a segment of the regionally extensively (>1500 km long) Irtysh-Ertix-Bulgan thrust zone. As the plutonic bodies both cut and are deformed by the shear fabrics in this regional thrust shear zone, the duration of felsic magmatism and regional thrusting was temporally overlapping. This suggests that magmatism was coeval with crustal thickening. Major- and trace-element data and isotopic analysis of granitoid samples from our study area indicate that the felsic intrusions were derived from partial melting of meta-sediments, with the biotite and two-mica granite generated through vapor-absent melting and the leucogranite from flux melting. Although the Mongolian Altai intrusions were clearly originated from anatexis, coeval granite in the Chinese Altai directly west of our study area in the hanging wall of the Irtysh-Ertix-Bulgan thrust was derived in part from mantle melting. To reconcile these observations, we propose a Himalayan-style intracontinental-subduction model that predicts two geologic settings for the occurrence of felsic magmatism: (1) along the intracontinental thrust zone where granite was entirely generated by anatexis and (2) in the hanging wall of the intracontinental thrust where convective removal and/or continental subduction induced mantle melting.

  4. SHRIMP U-Pb age and high temperature conditions of the collisional metamorphism in the Várzea do Capivarita Complex: Implications for the origin of Pelotas Batholith, Dom Feliciano Belt, southern Brazil

    Science.gov (United States)

    Philipp, Ruy Paulo; Bom, Francisco Molina; Pimentel, Márcio Martins; Junges, Sérgio Luiz; Zvirtes, Gustavo

    2016-03-01

    The Várzea do Capivarita Complex is composed of pelitic gneisses with subordinate calc-silicate rock, marble and rare quartzite. It is part of the neoproterozoic Dom Feliciano Belt, in southern Brazil. The gneisses are associated to veins and tabular leucogranite bodies, which are the product of anatexis of the pelitic gneiss. The paragneisses of the Várzea do Capivarita Complex are tectonically juxtaposed to orthogneisses of the Arroio dos Ratos Complex. This complex is exposed as megaxenoliths in granites of the Encruzilhada do Sul Suite and as smaller fragments in the Quitéria and Cordilheira Granites, all part of the Pelotas Batholith. The metamorphic foliation is oriented to N30°W, with dips between 35 and 55° to the SW and mineral lineation is suborizontal with rake ranging from 15° to 30° and down dip to NW and SE, suggesting deformation associated with a transpressive system. Based on the paragenesis garnet-cordierite-sillimanite-biotite, metamorphism occurred at 720-820° C and pressure of 8-9 kbar, characterizing it as of intermediate pressure and high temperature series. Zircon grains of one sample of garnet-cordierite-sillimanite-biotite gneiss and one of peraluminous leucogranite was dated by the U-Pb SHRIMP method. The paragneiss metamorphic zircon yielded an age of 619 ± 4.3 Ma interpreted as an age of the main metamorphic event, whereas igneous zircon grains from the leucogranite indicates that magma crystallization took place at 620 ± 6.3 Ma. The main metamorphic foliation (S2) of the paragneiss and the leucogranite magmatic foliation (S0) are parallel to each other, indicating that they were formed during the same event. This suggests that anatexis of the paragneisses of the Várzea do Capivarite Complex generated the peraluminous leucogranites right after the climax of the collisional metamorphism.

  5. Permo-Triassic and Paleoproterozoic metamorphism related to continental collision in Yangpyeong, South Korea

    Science.gov (United States)

    Oh, Chang Whan; Imayama, Takeshi; Lee, Seung Yeol; Yi, Sang-Bong; Yi, Keewook; Lee, Byung Choon

    2015-02-01

    Gneisses and migmatites exposed in the Yangpyeong area in the northern Gyeonggi Massif provide insight into the Paleoproterozoic and Triassic metamorphic events in South Korea. Garnet-biotite gneiss and sillimanite-garnet-biotite gneiss in the western part of the area reveal Paleoproterozoic metamorphism (1888-1871 Ma) at P-T conditions of 760-820 °C and 8-10 kbar and 710-750 °C and 5-7 kbar, respectively. These rocks were overprinted by low-P/T type metamorphism (590-650 °C, 3-4 kbar) during the Triassic (ca. 237 Ma). In contrast, a cordierite-rich migmatite near the post-collisional Triassic igneous complex in the eastern part of the area was strongly metamorphosed during the Triassic (ca. 235 Ma) at 750-790 °C and 7-8 kbar. The similar Triassic ages in the western and eastern areas suggest that low-P/T type metamorphism occurred as a second stage of regional metamorphism, which is characterized by the production of cordierite with an irregularly shaped garnet. The metamorphic grade of the Triassic metamorphism decreases spatially towards the west from granulite facies to amphibolite facies metamorphic conditions, and the Paleoproterozoic metamorphism is well preserved in the western part with low grade Triassic metamorphism. The new discovery of the Triassic metamorphic event in the Yangpyeong area, in addition to the previously reported Triassic post-collision igneous event, supports the idea that the continental collision belt between the North and South China blocks extends from the Hongseong area into the Odesan area through the Yangpyeong area in South Korea.

  6. Petrology and U/Pb geochronology of the Santa Maria Ipalapa region in the southeastern part of the Xolapa Complex, Mexico: Constrains of the metamorphic evolution of the Xolapa Terrane

    Science.gov (United States)

    Gutiérrez Aguilar, F.; Victoria Morales, A.; Maldonado, R.

    2015-12-01

    The Xolapa Complex is a metamorphic-plutonic basement that forms a large belt with more than 600 km length and 50-100 km wide along the Pacific coast of southeastern Mexico. This Complex is constituted by a high grade sequence of meta-sedimentary and meta-igneous rocks, locally migmatisized, and which are intruded by strongly deformed plutonic rocks. Because of their representative characteristics, two samples were analyzed: 1) Para-schist: this rocks present a mineral assemblage composed of biotite, sillimanite, plagioclase, k-feldspar and garnet, and 2) Amphibolite: which are constituted by amphibole, plagioclase, biotite and garnet. The garnet porphydoblasts in the para-schist are subhedral, presents retrograde compositional zoning, with almandine and pyrope rich core (Alm74-75Sps7.-10.1Pyr12.1-12.5Grs3.8-3.9) and spessartine rich rim (Alm69-71Sps14-19Pyr7.9-9.6Grs3.6-3.7). The garnet in amphibolite, presents a prograde growth zoning with a slight increase in spessartine in the core (Alm59-60Grs24-25Pyr8.0-8.3Sps7.3-7.6), and low content of spessartine component toward the rim (Alm60-62Grs23-24Pyr8.8-9.6Sps5.4-5.5). In order to constrain the P-T evolution of the region, multiequilibria thermobarometry was applied to both samples, the para-schist unit presents P-T data from 706 (ºC) and 7.5 (kbar), in the other hand the garnet amphibolite unit shows P-T data from 734 (ºC) and 7 (kbar). This study provides new geochronological data (U/Pb in zircons) for the amphibolite facies metamorphism and for the migmatitic event in the region that contributes to the understanding of the tectonic evolution of southeastern Mexico.

  7. Hydrological and geochemical constraints on the mechanism of formation of arsenic contaminated groundwater in Sonargaon, Bangladesh

    International Nuclear Information System (INIS)

    The geochemical characteristics and hydrological constraints of high As groundwater in Sonargaon, in mid-eastern Bangladesh were investigated in order to ascertain the mechanism of As release into the groundwaters from host sediments in the Ganges-Brahmaputra delta. Samples of groundwater were collected from ca. 230 tube wells in both the rainy and dry seasons. Similar to previous studies, high As groundwater was found in the Holocene unconfined aquifer but not in the Pleistocene aquifer. Groundwaters in the Holocene aquifer were of the Ca-Mg-HCO3 type with major solutes derived from chemical weathering of detrital minerals such as plagioclase and biotite. Groundwater with high As was generally characterized by high NH4+, possibly derived from the agricultural application of fertilizer as suggested by the small variation of δ15NNH4 (mostly 2-4 per mille ). Concentrations of Fe changed between the rainy and dry seasons by precipitation/dissolution of Fe oxyhydroxide and siderite, whilst there was not an apparent concomitant change in As. Inhomogeneous spatial distribution of δ18O in the Holocene unconfined aquifer indicates poor mixing of groundwater in the horizontal direction. Spatial variation of redox conditions is associated with localized variations in subsurface permeability and the recharge/discharge cycle of groundwater. Hydrogeochemical data presented in this paper suggest that reduction of Fe oxyhydroxide is not the only mechanism of As mobilization, and chemical weathering of biotite and/or other basic minerals in the Holocene aquifer could also be important as a primary cause of As mobilization

  8. Paleoproterozoic, High-Metamorphic, Metasedimentary Units of Siberian Craton

    Institute of Scientific and Technical Information of China (English)

    Lena URMANTSEVA; Olga TURKINA

    2009-01-01

    Sensitive, high-resointion ion microprobe zircon U-Pb ages of Paleoproterozoic, high-grade,metasedimentary rocks from the south-western part of the Siberian Craton are reported. Early Precambrian, high-grade complexes, including garnet-biotite, hypersthene-biotite, and cordierite-bearing gneisses compose the Irkut terrane of the Sharyzhalgay Uplift. Protoliths of studied gneisses correspond to terrigenous sediments, ranging from greywacke to shale. The paragneiss model Nd ages of 2.4-3.1 Ga indicate Archean-to-Paleoproterozoic source provinces. Zircons from gneisses show core-rim textures in cathodoluminescence (CL) image. Round or irregular shaped cores indicate detrital origin. Structureless rims with low Th/U are metamorphic in origin. The three age groups of detrital cores are: ≥2.7, -2.3, and 1.95-2 Ga. The ages of metamorphic rims range from 1.86 to 1.85 Ga;therefore, the sediments were deposited between 1.95 and 1.86 Ga and derived from Archean and Paleoproterozoic source rocks. It should be noted that Paleoproterozoic metasedimentary rocks of the Irkut Block are not unique. High-grade metaterrigenons sediments, with model Nd ages ranging from 2.3 to 2.5 Ga, are widely distributed within the AIdan and Anabar Shields of the Siberian Craton. The same situation is observed in the North China Craton, where metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 to 2.1 Ga (Wan et al., 2006). All of these sedimentary units were subjected to Late Paleoproterozoic metamorphism. In the Siberian Craton, the Paleoproterozoic sedimentary deposits are possibly marked passive margins of the Early Precambrian crustal blocks, and their high-grade metamorphism was related to the consolidation of the Siberian Craton.

  9. Petrological and geochemical studies of ultramafic-mafic rocks from the North Puruliya Shear Zone (eastern India)

    Science.gov (United States)

    Mandal, Aditi; Ray, Arijit

    2015-12-01

    Ultramafic and mafic rocks occur within a linear belt, trending nearly E-W along North Puruliya Shear Zone of the Chhotanagpur Gneissic Complex (CGC). These rocks are classified as gabbro, norite, gabbro-norite, dolerite, diorite, olivine-websterite and lherzolite. Mafic rocks (Group 1) often occur in association with ultramafic variants (Group 2) and sometimes in isolation. A genetic link has been established between these mafic and ultramafic rocks using disposition of ultramafic and mafic rocks in the outcrop, systematic variation in modal mineralogy, co-linearity of plots in biaxial chemical variation diagram. Chemical composition of biotite and clinopyroxene reveal calc-alkaline nature and arc signature in these mafic-ultramafic rocks and whole rock geochemical characters indicate similarity with arc magma in subduction zone setting. The high values of Mg no. (47-81) and Al 2 O 3 (5.5-17.9) of mafic rocks indicate primitive, aluminous nature of the parental melt and presence of amphibole and biotite indicate its hydrous nature. The parent mafic melt evolved through fractionation of olivine, spinel, clinopyroxene and plagioclase. The crystal cumulates gave rise to the ultramafic rocks and the associated mafic rocks formed from residual melt. Crustal contamination played an important role in magmatic evolution as evident from variation in abundance of Rb in different lithomembers. Mafic-ultramafic rocks of the present study have been compared with intra-cratonic layered complexes, mafic-ultramafic rocks of high grade terrain, Alaskan type ultramafic-mafic complex and ophiolites. It is observed that the ultramafic-mafic rocks of present study have similarity with Alaskan type complex.

  10. Geochemistry of Central Atlantic Magmatic Province (CAMP) sills from deep boreholes in the Amazonas and Solimões basins, Brazil

    Science.gov (United States)

    Hatlen Heimdal, Thea; Svensen, Henrik H.; Pereira, Egberto; Planke, Sverre

    2016-04-01

    The Central Atlantic Magmatic Province (CAMP) is one of the most extensive Large Igneous Provinces (LIPs), and is associated with the breakup of Pangea and the subsequent opening of the central Atlantic Ocean. A large part of the province, including > 1 M km2 basins containing sill intrusions, is located in Brazil but has received limited attention due to the lack of outcrops. We have studied CAMP sills from seven deep boreholes (up to 3100 m deep) in the Amazonas and Solimões basins, northern Brazil. The boreholes contain up to ~ 482 m of sills (18 % of the stratigraphy), with a maximum individual sill thickness of 140 m. The sills were partly emplaced into thick Carboniferous evaporites. The main mineral phases of the sills include plagioclase and pyroxene, with accessory apatite, biotite, ilmenite and quartz. The majority of the sills are low-Ti dolerites (TiO2 rocks range from basalt to basaltic andesite and plot in the tholeiitic field defined within the total alkali versus silica (TAS) classification. C1 chondrite normalized Rare Earth Element (REE) patterns for both Ti-groups show increasing LREE compared to HREE (La/Lu = 2.2 - 4.1) with no major anomalies, and attest to a relatively evolved nature (La = 17-65 ppm). Primitive mantle normalized patterns for low-Ti rocks show negative anomalies for Nb, Ta, P and Ti and positive for K, whereas the high-Ti rocks show generally opposite anomalies. Late stage patches in the dolerites contain apatite, quartz and Cl-bearing biotite, suggesting the presence of halogens that may partly derive from the host sedimentary rocks.

  11. Petrological and geochemical studies of ultramafic–mafic rocks from the North Puruliya Shear Zone (eastern India)

    Indian Academy of Sciences (India)

    Aditi Mandal; Arijit Ray

    2015-12-01

    Ultramafic and mafic rocks occur within a linear belt, trending nearly E–W along North Puruliya Shear Zone of the Chhotanagpur Gneissic Complex (CGC). These rocks are classified as gabbro, norite, gabbronorite, dolerite, diorite, olivine-websterite and lherzolite. Mafic rocks (Group 1) often occur in association with ultramafic variants (Group 2) and sometimes in isolation. A genetic link has been established between these mafic and ultramafic rocks using disposition of ultramafic and mafic rocks in the outcrop, systematic variation in modal mineralogy, co-linearity of plots in biaxial chemical variation diagram. Chemical composition of biotite and clinopyroxene reveal calc-alkaline nature and arc signature in these mafic–ultramafic rocks and whole rock geochemical characters indicate similarity with arc magma in subduction zone setting. The high values of Mg no. (47–81) and Al2O3 (5.5–17.9) of mafic rocks indicate primitive, aluminous nature of the parental melt and presence of amphibole and biotite indicate its hydrous nature. The parent mafic melt evolved through fractionation of olivine, spinel, clinopyroxene and plagioclase. The crystal cumulates gave rise to the ultramafic rocks and the associated mafic rocks formed from residual melt. Crustal contamination played an important role in magmatic evolution as evident from variation in abundance of Rb in different lithomembers. Mafic–ultramafic rocks of the present study have been compared with intra-cratonic layered complexes, mafic–ultramafic rocks of high grade terrain, Alaskan type ultramafic–mafic complex and ophiolites. It is observed that the ultramafic–mafic rocks of present study have similarity with Alaskan type complex.

  12. A Palaeoproterozoic multi-stage hydrothermal alteration system at Nalunaq gold deposit, South Greenland

    Science.gov (United States)

    Bell, Robin-Marie; Kolb, Jochen; Waight, Tod Earle; Bagas, Leon; Thomsen, Tonny B.

    2016-07-01

    Nalunaq is an orogenic, high gold grade deposit situated on the Nanortalik Peninsula, South Greenland. Mineralisation is hosted in shear zone-controlled quartz veins, located in fine- and medium-grained amphibolite. The deposit was the site of Greenland's only operating metalliferous mine until its closure in 2014, having produced 10.67 t of gold. This study uses a combination of field investigation, petrography and U/Pb zircon and titanite geochronology to define a multi-stage hydrothermal alteration system at Nalunaq. A clinopyroxene-plagioclase-garnet(-sulphide) alteration zone (CPGZ) developed in the Nanortalik Peninsula, close to regional peak metamorphism and prior to gold-quartz vein formation. The ca. 1783-1762-Ma gold-quartz veins are hosted in reactivated shear zones with a hydrothermal alteration halo of biotite-arsenopyrite-sericite-actinolite-pyrrhotite(-chlorite-plagioclase-löllingite-tourmaline-titanite), which is best developed in areas of exceptionally high gold grades. Aplite dykes dated to ca. 1762 Ma cross-cut the gold-quartz veins, providing a minimum age for mineralisation. A hydrothermal calcite-titanite alteration assemblage is dated to ca. 1766 Ma; however, this alteration is highly isolated, and as a result, its field relationships are poorly constrained. The hydrothermal alteration and mineralisation is cut by several generations of ca. 1745-Ma biotite granodiorite accompanied by brittle deformation. A ca. 1745-Ma lower greenschist facies hydrothermal epidote-calcite-zoisite alteration assemblage with numerous accessory minerals forms halos surrounding the late-stage fractures. The contrasting hydrothermal alteration styles at Nalunaq indicate a complex history of exhumation from amphibolite facies conditions to lower greenschist facies conditions in an orogenic belt which resembles modern Phanerozoic orogens.

  13. Geologic study of Kettle dome, northeast Washington. Final report

    International Nuclear Information System (INIS)

    This geologic study of Kettle dome, northeast Washington, encompasses an area of approximately 800 square miles (2048 sq km). The evaluation of uranium occurrences associated with the igneous and metamorphic rocks of the dome and the determination of the relationship between uranium mineralization and stratigraphic, structural, and metamorphic features of the dome are the principal objectives. Evaluation of the validity of a gneiss dome model is a specific objective. The principal sources of data are detailed geologic mapping, surface radiometric surveys, and chemical analyses of rock samples. Uranium mineralization is directly related to the presence of pegmatite dikes and sills in biotite gneiss and amphibolite. Other characteristics of the uranium occurrences include the associated migmatization and high-grade metamorphism of wallrock adjacent to the pegmatite and the abrupt decrease in uranium mineralization at the pegmatite-gneiss contact. Subtle chemical characteristics found in mineralized pegmatites include: (1) U increase as K2O increases, (2) U decreases as Na2O increases, and (3) U increases as CaO increases at CaO values above 3.8%. The concentration of uranium occurrences in biotite gneiss and amphibolite units results from the preferential intrusion of pegmitites into these well-foliated rocks. Structural zones of weakness along dome margins permit intrusive and migmatitic activity to affect higher structural levels of the dome complex. As a result, uranium mineralization is localized along dome margins. The uranium occurrences in the Kettle dome area are classified as pegmatitic. Sufficient geologic similarities exist between Kettle dome and the Rossing uranium deposit to propose the existence of economic uranium targets within Kettle dome

  14. Post-collisional Pan-African granitoids and rare metal pegmatites in western Nigeria: Age, petrogenesis, and the 'pegmatite conundrum'

    Science.gov (United States)

    Goodenough, K. M.; Lusty, P. A. J.; Roberts, N. M. W.; Key, R. M.; Garba, A.

    2014-07-01

    The Minna area of western Nigeria lies within a Pan-African orogenic belt that extends along the margin of the West African Craton, from Algeria southwards through Nigeria, Benin and Ghana, and into the Borborema Province of Brazil. This belt is characterised by voluminous post-collisional granitoid plutons that are well exposed around the city of Minna. In this paper we present new information about their age and petrogenesis. The Pan-African plutons around Minna can be divided into two main groups: a group of largely peraluminous biotite-muscovite granites that show varying levels of deformation in late Pan-African shear zones; and a younger group of relatively undeformed, predominantly metaluminous hornblende granitoids. Pegmatites, including both barren and rare-metal types, occur at the margins of some of the plutons. New U-Pb zircon dating presented here, in combination with published data, indicates an early phase of magmatism at c. 790-760 Ma in the Minna area. This magmatism could be related either to continental rifting, or to subduction around the margins of an existing continent. The peraluminous biotite-muscovite granites were intruded at c. 650-600 Ma during regional shearing in the orogenic belt, and are likely to have formed largely by crustal melting. Subsequent emplacement of metaluminous granitoids at c. 590 Ma indicates the onset of post-orogenic extension in this area, with a contribution from mantle-derived magmas. The rare-metal pegmatites represent the youngest intrusions in this area and thus are likely to have formed in a separate magmatic episode, post-dating granite intrusion.

  15. Hydrothermal alterations and O, H, C isotopic characterization of fluids and minerals in uraniferous massif of Saint Sylvestre (France). Extension to other French intragranitic uranium deposits

    International Nuclear Information System (INIS)

    Petrographical, mineralogical, geochemical and stable isotope (18O/16O, D/H, 13C/12C) studies have been performed on the leucogranitic massif of St Sylvestre (Limousin, Massif Central francais), particularly on the different hydrothermal alterations. The oxygen isotope geochemistry of granites confirms the unicity of the different facies and their sialic origin (delta18O whole rocks = +11.0 +- 0.5 per mill), with a major contribution of detritic sediments rich in organic matter and poor in carbonate (delta13C magm. CO2 = -10.6 per mill). Late lamprophyres have a deep-seated origin (delta18O = + 6 per mill). The pervasive chloritization of granitic biotites occurs during the convective circulation of a fluid of meteoric origin, at temperatures around 350-4500C. The chemical composition of chlorite which is buffered by that of biotite and the large 18O-shift of fluid towards high delta values indicate that water-rock ratio was not very high. Chloritization takes place in high permeability zones. In regions where porosity is generally low, fluids are ''canalised'' in localised micro-fissured zones. Very high water/rock ratios lead to the dissolution of quartz, and the formation of the ''feldspathic episyenite'' alteration facies. The isotopic features of this fluid (delta18O approximately - 8 per mill, deltaD approximately - 50 per mill) indicate an elevated altitude. An isotopically similar fluid is responsible for the later ''micaceous episyenite'' alteration facies, found in fractured zones. Mixing of this fluid with a sedimentary fluid (delta18O approximately + 10 per mill, deltaD approximately - 30 per mill, delta13C approximately - 18 per mill) yielded the conditions necessary for the deposit of primary economic ore. Such fluids, sedimentary or metamorphic in origin, have been recognized in most hercynian intragranitic U and Sn-W deposits

  16. Mafic granulite xenoliths in the Chilka Lake suite, Eastern Ghats Belt, India: evidence of deep-subduction of residual oceanic crust

    Directory of Open Access Journals (Sweden)

    S. Bhattacharya

    2012-11-01

    Full Text Available Granulite xenoliths preserve key geochemical and isotopic signatures of their mantle source regions. Mafic granulite and pyroxinite xenoliths within massif-type charnockitic rocks from the Eastern Ghats Belt have recently been reported by us. The mafic granulite xenoliths from the Chilka Lake granulite suite with abundant prograde biotite are geochemically akin to Oceanic Island Basalt (OIB. They can be distinguished from the hornblende-mafic granulite xenoliths with signatures of Arc-derived basalt occurring in the other suites of the Eastern Ghats Belt. These two groups of xenoliths in the Paleoproterozoic Eastern Ghats Province have quite distinct Nd-model ages- 1.9 Ga and 2.5 Ga respectively, which may be interpreted as their crustal residence ages. Strong positive Nb anomalies, indicating subducted oceanic crust in the source, LREE enrichment and strongly fractionated REE pattern are key geochemical signatures attesting to their origin as OIB-type magma. Also low Yb and Sc contents and high (La / YbN ratios can be attributed to melting in the presence of residual garnet and hence at great depths (> 80 km. The variable enrichment in radiogenic 87Sr, between 0.70052 and 0.71092 at 1.9 Ga and less radiogenic 143Nd between ε-1.54 and 7.46 are similar to those of the OIBs compared to MORBs. As OIBs commonly contain some recycled oceanic crust in their sources, we suggest that the residue of the oceanic crust from a previous melting event (~ 2.5 Ga that produced the Arc-derived basalts (protoliths of hornblende-mafic granulite xenoliths could have subducted to great depths and mechanically mixed with the mantle peridotite. A subsequent re-melting event of this mixed source might have occurred at ca. 1.9 Ga as testified by the crustal residence ages of the biotite-mafic granulite xenoliths of the Chilka Lake granulite suite.

  17. Mafic granulite xenoliths in the Chilka Lake suite, Eastern Ghats Belt, India: evidence of deep-subduction of residual oceanic crust

    Science.gov (United States)

    Bhattacharya, S.; Chaudhary, A. K.; Saw, A. K.; Das, P.; Chatterjee, D.

    2012-11-01

    Granulite xenoliths preserve key geochemical and isotopic signatures of their mantle source regions. Mafic granulite and pyroxinite xenoliths within massif-type charnockitic rocks from the Eastern Ghats Belt have recently been reported by us. The mafic granulite xenoliths from the Chilka Lake granulite suite with abundant prograde biotite are geochemically akin to Oceanic Island Basalt (OIB). They can be distinguished from the hornblende-mafic granulite xenoliths with signatures of Arc-derived basalt occurring in the other suites of the Eastern Ghats Belt. These two groups of xenoliths in the Paleoproterozoic Eastern Ghats Province have quite distinct Nd-model ages- 1.9 Ga and 2.5 Ga respectively, which may be interpreted as their crustal residence ages. Strong positive Nb anomalies, indicating subducted oceanic crust in the source, LREE enrichment and strongly fractionated REE pattern are key geochemical signatures attesting to their origin as OIB-type magma. Also low Yb and Sc contents and high (La / Yb)N ratios can be attributed to melting in the presence of residual garnet and hence at great depths (> 80 km). The variable enrichment in radiogenic 87Sr, between 0.70052 and 0.71092 at 1.9 Ga and less radiogenic 143Nd between ɛ-1.54 and 7.46 are similar to those of the OIBs compared to MORBs. As OIBs commonly contain some recycled oceanic crust in their sources, we suggest that the residue of the oceanic crust from a previous melting event (~ 2.5 Ga) that produced the Arc-derived basalts (protoliths of hornblende-mafic granulite xenoliths) could have subducted to great depths and mechanically mixed with the mantle peridotite. A subsequent re-melting event of this mixed source might have occurred at ca. 1.9 Ga as testified by the crustal residence ages of the biotite-mafic granulite xenoliths of the Chilka Lake granulite suite.

  18. The zinc stable isotope signature of waste rock drainage in Arctic Canada

    Science.gov (United States)

    Matthies, Romy; Blowes, David

    2014-05-01

    Leachate emerging from a pilot-scale waste rock pile of the Diavik diamond mine, Northwest Territories, was monitored. The well-characterized waste rock consists of granite, pegmatitic granite and biotite schist with an average total sulfur and carbonate carbon concentration of 0.053 and 0.027 wt. %, respectively. During the field seasons of 2011 and 2012, the Zn stable isotope footprint was characterized alongside standard monitoring parameters. pH ranged between 4.3 and 6.8 and carbonate alkalinity was low or undetectable. Al and Fe concentrations averaged 6.78 mg L-1 and 175 µg L-1, respectively. The pH and metal mobility were governed by sulfide oxidation and sorption and co-precipitation onto iron and aluminium hydroxides. The main processes controlling zinc mobility in the range of 0.4 and 4.7 mg L-1 was the oxidative dissolution of sphalerite (ZnS) in the biotite schist and the attenuation of zinc onto secondary iron and aluminium hydroxides and desorption upon the pH declining below the pHpzc. The isotope ratios between -0.16 and +0.19 ‰ (δ66Zn, avg = +0.05 ‰, n = 43) are consistent with values reported from other sphalerite containing deposits. Zn isotope ratios and concentrations were largely uncorrelated suggesting that the processes affecting Zn mobility had little or no impact on the Zn isotope signature. Data indicate, that the Zn isotope ratios of the waste rock leachate may be used as a fingerprint to track anthropogenic, mine-derived Zn sources under varying environmental conditions.

  19. Can the Metamorphic Basement of Northwestern Guatemala be Correlated with the Chuacús Complex?

    Science.gov (United States)

    Cacao, N.; Martens, U.

    2007-05-01

    The Chuacús complex constitutes a northward concave metamorphic belt that stretches ca. 150 km south of the Cuilco-Chixoy-Polochic (CCP) fault system in central and central-eastern Guatemala. It represents the basement of the southern edge of the Maya block, being well exposed in the sierra de Chuacús and the sierra de Las Minas. It is composed of high-Al metapelites, amphibolites, quartzofeldspathic gneisses, and migmatites. In central Guatemala the Chuacús complex contains ubiquitous epidote-amphibolite mineral associations, and local relics of eclogite reveal a previous high-pressure metamorphic event. North of the CCP, in the Sierra de Los Cuchumatanes area of western Guatemala, metamorphic rocks have been considered the equivalent of the Chuacús complex and hence been given the name Western Chuacús group, These rocks, which were intruded by granitic rocks and later mylonitized, include chloritic schist and gneiss, biotite-garnet schist, migmatites, and amphibolites. No eclogitic relics have been found within metamorphic rocks in northwestern Guatemala. Petrographic analyses of garnet-biotite schist reveal abundant retrogression and the formation of abundant zeolite-bearing veins associated with intrusion. Although metamorphic conditions in the greenschist and amphibolite facies are similar to those in the sierra de Chuacús, the association with deformed intrusive granites is unique for western Guatemala. Hence a correlation with metasediments intruded by the Rabinal granite in the San Gabriel area of Baja Verapaz seems more feasible than a correlation with the Chuacús complex. This idea is supported by reintegration of the Cenozoic left-lateral displacement along the CCP, which would place the metamorphic basement of western Guatemala north of Baja Verapaz, adjacent to metasediments intruded by granites in the San Gabriel-Rabinal area.

  20. Petrogenesis of subvolcanic rocks from the Khunik prospecting area, south of Birjand, Iran: Geochemical, Sr-Nd isotopic and U-Pb zircon constraints

    Science.gov (United States)

    Samiee, Somayeh; Karimpour, Mohammad Hassan; Ghaderi, Majid; Haidarian Shahri, Mohammad Reza; Klöetzli, Urs; Santos, José Francisco

    2016-01-01

    The Khunik prospecting area is located 106 km south of Birjand in eastern Iran, and is considered as an epithermal gold prospecting area. The mineralization is related to subvolcanic rocks. There are several outcrops of subvolcanic intrusions in the area which intruded into Paleocene-Eocene volcanic rocks (andesite, trachy-andesite and pyroclastic rocks). Petrographic studies indicate that subvolcanic rocks consist mainly of diorite, monzonite, quartz-monzonite, monzodiorite and quartz-monzodiorite. Mineralogically, these rocks contain plagioclase, K-feldspar, amphibole, pyroxene, biotite and quartz. Geochemically, they have features typical of high-K calk-alkaline to shoshonitic and are metaluminous, and also belong to magnetite granitoid series (I-type). Primitive mantle normalized trace element spider diagrams display enrichment in LILE, such as Rb, Ba, and Cs, compared to HFSE. Chondrite-normalized REE plots show moderately LREE enriched patterns (7.45 diagrams also show affinities with modern convergent margin magmas, suggesting that magmas of Khunik area formed in volcanic arc setting related to subduction of the oceanic crust under the Lut Block plate. The initial 87Sr/86Sr ratios (0.704196-0.704772) and εNdi values (+1.3 to +3.3) are compatible with an origin of the parental melts in a supra-subduction mantle wedge. Zircon U-Pb dating by LA-ICP-MS indicates the age of 38 ± 1 Ma (late Eocene) for subvolcanic units that are related to mineralization. A biotite granodiorite porphyry is the testimony of the youngest magmatic activity in the area, with an age of 31 ± 1 Ma (early Oligocene). The represented dates are interpreted as magmatic crystallization ages of subvolcanic intrusions.

  1. Clay minerals as alteration products in acidic igneous rocks from Oued Belif structure (Nefza, North Tunisia)

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Full text of publication follows: The Oued Belif structure is located in the north of Tunisia, seven kilometers north of Nefza city. It is part of the widespread Northern Tunisian 'Nappe Zone' composed of thrust sheets. This structure is delimited by a breccia rim, which encloses Triassic salt-related rocks and Serravallian to Tortonian (8.3 to 12.9 Ma) magmatic bodies (rhyodacite and granodiorite) associated with skarn deposits. Microscopic observation, chemical analyses, XRD, SEM and TEM investigations reveal that the mineral paragenesis of magmatic rocks consists mainly of clay minerals associated with other minerals such as quartz, biotite, feldspar and iron oxide. The outcropping magmatic rocks (granodiorite and rhyodacite) show an argillaceous paragenesis. The latter is made up of illite, kaolinite, smectite. The occurrence of these minerals is related to the meteoric weathering processes. Buried magmatic rocks, crossed by Oued Belif 45 borehole, show a considerable mobilization and removal of feldspar materiel and primary glass. This borehole crosses 370 m of the succession attributed to late Miocene. From bottom to top, we can identify (i) safe granodiorite; (ii) altered granodiorite; (iii) an alternation of altered rhyodacite and clayey unit rich in pyrite and (iiii) a very clayey rhyodacite unit. The clay fraction of the OB 45 borehole samples consists mainly of illite, kaolinite and smectite. These clay minerals were formed by the hydrothermal circulations through micro-fractures in magmatic rocks, which are forced by the high thermal gradient. The weathering of biotites, feldspars and primary glass contained both in buried and in outcropping magmatic rocks, produces illite, smectite and kaolinite. This is the result of the combined effect of subsurface oxidizing meteoric fluids and deep reducing hydrothermal fluids. (authors)

  2. Fluid inclusion and sulfur isotope thermometry of the Inkaya (Simav-Kütahya) Cu-Pb-Zn-(Ag) mineralization, NW TURKEY

    Science.gov (United States)

    Özen, Yeşim; Arik, Fetullah

    2013-09-01

    The Inkaya Cu-Pb-Zn-(Ag) mineralization, located about 20 km west of the Simav (Kütahya-Turkey), is situated in the northern part of the Menderes Massif Metamorphics. The mineralization is located along an E-W trending fault in the Cambrian Simav metamorphics consisting of quartz-muscovite schist, quartz-biotite schist, muscovite schist, biotite schist and the Arıkayası formation composed of marbles. Mineralized veins are 30-35 cm in width. The primary mineralization is represented by abundant galena, sphalerite, chalcopyrite, pyrite, fahlore and minor amounts of cerussite, anglesite, digenite, enargite, chalcocite, covellite, bornite, limonite, hematite and goethite with gangue quartz. Fluid inclusion studies on the quartz samples collected from the mineralized veins indicate that the temperature range of the fluids is 235°C to 340°C and the salinities are 0.7 to 4.49 wt. % NaCl equivalent. The wide range of homogenization temperatures indicates that two different fluid generations were trapped in quartz. Sulfur isotope studies of the sulfide minerals showed that all of the δ 34S values are between -2.1 and 2.6 per mil. These values are a typical range for hydrothermal sulfide minerals that have sulfur derived from a magmatic source. Pyrite-galena and pyrite-chalcopyrite sulfur isotope fractionation is consistent with an approach to isotopic equilibrium, and calculated temperatures are 254.6 and 277.4°C for pyrite-galena and 274.7°C for pyrite-chalcopyrite. The microthermometric data and sulfur isotope thermometry indicate the existence of a hydrothermal fluid that circulated along the fault crossing the Simav metamorphics and Arıkayası formation. Fluid inclusion and sulfur isotope thermometry can be used in combination with ore petrographical and geological information to provide site-specific targets for meso-hypothermal metal concentrations.

  3. Magmatic and tectonic evolution of the Ladakh Block from field studies

    Science.gov (United States)

    Raz, U.; Honegger, K.

    1989-04-01

    The Ladakh Block is in an intermediate position between the Indian plate in the south and the Karakorum-Tibetan plate in the north. To the west it is separated from the Kohistan Arc by the Nanga Parbat Syntaxis, to the east it is cut off from the Lhasa Block by the Gartok-Nubra Fault. Present data, together with previously published results, show, that the Ladakh Block consists of an island arc in the south and a calc-alkaline batholith in the north with remnants of a continental crust. Migmatitic gneisses and metasedimentary sequences, such as quartzites and metapelites, interbedded with basaltic volcanics and overlain by thick platform carbonates were found as evidence of a continental crust. Remnants of megafossils ( Megalodon and Lithiotis) within the high-grade metamorphic marbles indicate a probable age of Late Triassic to Early Jurassic. These sediments were intruded by a faintly layered hornblende-gabbro, which preceded the calc-alkaline magmatic episode. Gabbro and gabbronorites are found as roof pendants and large inclusions within diorites and granodiorites. The major part of the batholith consists of granodiorite and biotite-granite plutons, ranging from Late Cretaceous to Tertiary. Associated with the intrusives are volcanic rocks with trachyandesite to alkalibasalt and basalt-andesite to rhyolite compositions. Garnet-bearing leucogranites succeeded the emplacement of the major plutons. The magmatic stage ended, finally, by intense fracturing and injections of NE-SW striking andesitic dykes. The southernmost unit of the Ladakh Block is formed by oceanic crust with serpentinized peridotite and hornblende-gabbro and is covered by volcanics of an island-arc type (Dras volcanics). These units are intruded by gabbronorite, as well as Middle and Upper Cretaceous granodiorite and coarse-grained biotite-granite. In a plate tectonic view the Ladakh Block represents a transitional sector between the pure island arc of Kohistan in the west and the Andean type

  4. Zircon dating and mineralogy of the Mokong Pan-African magmatic epidote-bearing granite (North Cameroon)

    Science.gov (United States)

    Tchameni, R.; Sun, F.; Dawaï, D.; Danra, G.; Tékoum, L.; Nomo Negue, E.; Vanderhaeghe, O.; Nzolang, C.; Dagwaï, Nguihdama

    2015-12-01

    We present the mineralogy and age of the magmatic epidote-bearing granite composing most of the Mokong pluton, in the Central Africa orogenic belt (North Cameroon). This pluton intrudes Neoproterozoic (~830 to 700 Ma) low- to high-grade schists and gneisses (Poli-Maroua group), and is crosscut or interleaved with bodies of biotite granite of various sizes. The pluton is weakly deformed in its interior, but solid-state deformation increases toward its margins marked by narrow mylonitic bands trending NNE-SSW. The magmatic epidote granitic rocks are classified as quartz monzodiorite, granodiorite, monzogranite, and syenogranite. They are medium- to coarse-grained and composed of K-feldspar + plagioclase + biotite + amphibole + epidote + magnetite + titanite + zircon + apatite. In these granites, the pistacite component [atomic Fe+3/(Fe3+ + Al)] in epidote ranges from 16 to 29 %. High oxygen fugacity (log ƒO2 - 14 to -11) and the preservation of epidote suggest that the magma was oxidized. Al-in hornblende barometry and hornblende-plagioclase thermometry indicate hornblende crystallization between 0.53 and 0.78 GPa at a temperature ranging from 633 to 779 °C. Zircon saturation thermometry gives temperature estimates ranging from 504 to 916 °C, the latter being obtained on samples containing inherited zircons. U/Pb geochronology by LA-ICP-MS on zircon grains characterized by magmatic zoning yields a concordia age of 668 ± 11 Ma (2σ). The Mokong granite is the only known occurrence magmatic epidote in Cameroon, and is an important milestone for the comparison of the Central Africa orogenic belt with the Brasiliano Fold Belt, where such granites are much more abundant.

  5. Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

    Science.gov (United States)

    Dusel-Bacon, C.; Lanphere, M.A.; Sharp, W.D.; Layer, P.W.; Hansen, V.L.

    2002-01-01

    We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon-Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215-212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ???188-186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ???135-115 Ma, and muscovite and biotite ???110-108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

  6. Geology, alteration, mineralization and geochemical study in Kalateh Taimour area, NE Iran

    Directory of Open Access Journals (Sweden)

    Zahra Alaminia

    2010-11-01

    Full Text Available The area is located 20 km northwest of Kashmar and about 4 km of Kalateh Taimour in Khorasan Razavi province. The study area is part of Tertiary volcanic-plutonic belt north of Daruneh fault and its situation in tectonic inliers between two important active faults, Doruneh and Taknar. Volcanic rocks are mainly intermediate to acid pyroclastic type. They formed during early Tertiary. The volcanic rocks of the Kalateh Taimour area are predominantly andesitic basalt, andesite, latite, trachyte, dacite and rhyodacite and are observed as lava, tuff, lapilli tuff and agglomerate. Field evidences and study show several subvolcanic bodies including quartz hornblende biotite monzodiorite porphyry, quartz biotite monzodiorite porphyry, quartz diorite porphyry and microdiorite which are intruded sometime in mid-Tertiary. In this belt, new methods of image processing were used for enhancing the alteration zones to help near infra red and short wavelength infrared and bands example band ratios and principle component method. Propylitic, sericitic and argillic are the main alteration types. Minor silicification is found in some areas. Alteration is extent but mineralization is limited. Mineralization is mainly controlled by fault system. Several mineralized faults are being discovered. Open space filling features are abundant. In the study area, disseminate and stock work mineralization are abundant. The amount of sulfide minerals is very small. Ancient mining is present in the area. Stream sediment geochemical study shows a very broad and high level of gold anomaly. Rock geochemical study show very high levels of Au, Ag, Cu, Pb, Zn and Au value is correlative to Cu, Pb, Zn and Ag values. Due to alteration modeling, non uniformity in mineralization and low abundance of sulfide mineralization suggest study in low sulphidation Au-Cu deposit.

  7. Petrology and U-Pb zircon dating of intrusive rocks from A, C-south, and Dardvay districts, Sangan iron stone mine, Khaf

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    Abbas Golmohammadi

    2013-10-01

    Full Text Available Sangan magnetite skarn mine is located 300 km southeast of Mashhad, along the eastern part of Khaf-Drouneh volcanic-plutonic belt. Granitoids from three areas within the Sangan mine A, C-North and Dardvay were studied. Within the study area, three intrusive rocks including biotite-hornblende monzonite porphyry, biotite syenite and syenogranite were recognized. Based on field cross cutting, absence of garnet-magnetite skarn around the contact, and alteration by younger hydrothermal fluids, these granitoids are older than the magnetite skarn. U-Pb zircon age of the granitoid is 42 Ma (Middle Eocene. Magnetic susceptibility of the granitoids are 310-900 × 10-5 (SI units and therefore, they are classified as belonging to the magnetite-series (oxidant type I-type. Chemically, these granitoids are metaluminous, alkali-calcic to alkali and shoshonite to ultrapotassic. Enrichment of LREE, relative to HREE and enrichment of LILE (Sr, Cs, Rb, K and Ba relative to HFSE (Nb, Ta, Ti, Hf and Zr indicate that the magma formed in island arc setting. This magma originated from low partial melting (<1% of garnet-spinel lherzolite (low garnet and was contaminated in the continental crust. Based on the ratio of (La/YbN 6.23-34.73, indicate that small amount of garnet was left in the source rock. High ration of Rb/Sr, LILE/HFSE and high content of K2O, Th and Nb indicative of continental crust contamination. Petrognesis and geochronology of Sangan granitoid will help to know more about tectonomagmatic of Khaf-Kashmar-Drouneh volcanic-plutonic belt and their mineralization.

  8. Increasing potassium (K release from K-containing minerals in the presence of insoluble phosphate by bacteria

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    Mohammad Reza Sarikhani

    2016-03-01

    Full Text Available Introduction: Phosphorus and potassium are major essential macronutrients for biological growth and development. Application of soil microorganisms is one approach to enhance crop growth. Some bacteria are efficient in releasing K and solubilizing P from mineral sources but their behavior was not studied more in presence together. Materials and methods: In this study the ability of seven bacterial strains, including Pseudomonas putida P13, P. putida Tabriz, P. fluorescens Tabriz, P. fluorescens Chao, Pantoea agglomerans P5, Azotobacter sp. and Bacillus megaterium JK3 to release mineral K from muscovite and biotite with application of insoluble (Ca3(PO42 or soluble (Na2HPO4 P-sources was investigated. Nutrient Broth was used to prepare an overnight culture of bacteria to inoculate in Aleksandrov medium, which was used to study the dissolution of silicate minerals. It should be mentioned that Aleksandrov medium was used to determine the amount of released P from tricalcium phosphate (TCP while muscovite was added to the medium as a sole source of potassium. Concentration of P was determined spectrophotometrically by ammonium-vanadate-molybdate method and K was determined by flame photometry. Results: The insoluble P-source led to a significantly increased released K into assay medium (66%, and the net release of K from the biotite was significantly enhanced. Among bacterial strains, the highest mean of released K was observed with P. putida P13 which released more K (27% than the control. The amounts of released K from micas in the presence of insoluble and soluble phosphate by P. putida P13 were 8.25 and 4.87 mg/g, respectively. Discussion and conclusion: Application of insoluble phosphate could increase K release from mica minerals. The enhanced releasing of mineral K might be attributed to the release of organic acids from the bacteria, a mechanism which plays a pivotal role in solubilizing phosphate from inorganic source of phosphate.

  9. Early Paleozoic Magmatism and Gold Mineralization in the Northern Altun, NW China

    Institute of Scientific and Technical Information of China (English)

    CHEN Xuanhua; WANG Xiaofeng; George GEHRELS; YANG Yi; QIN Hong; CHEN Zhengle; YANG Feng; CHEN Bailin; LI Xuezhi

    2004-01-01

    This paper discusses the relationships between granitic magmatism and gold mineralization and the exhumation history of the Dapinggou gold deposit in northern Altun, NW China based on the geochronological data,including zircon U-Pb ages, Rb-Sr isochron age and 40Ar-39Ar dating and MDD modeling data. The main granitic magmatism age in this area is attained from the ID TIMS U-Pb geochronology of zircons from the Kuoshibulak granite,the biggest granite in the northern Altun area, which gives a concordant age of 443±5 Ma in the Late Ordovician. Zircon ID TIMS U-Pb geochronology of the West Dapinggou biotite granite west of the Dapinggou gold deposit gives concordant ages around 485±10 Ma, representing the early stage of Ordovician magmatism. The Rb-Sr isochron age (487±21 Ma) of 6 quartz inclusion samples from quartz veins in this gold deposit is very close to that of the West Dapinggou granite. MDD modeling of step heating 40Ar- 39Ar data of K-feldspar from the same West Dapinggou biotite granite gives a rapid cooling history from 300℃ to 150℃ during 200-185 Ma. According to the age data and the geological setting of this area, we conclude that the Dapinggou gold deposit was formed at the early stage of the Early Paleozoic granitic magmatism in northern Altun, and exhumed in the Early Jurassic due to the normal faulting of the Lapeiquan detachment. The Early Paleozoic magmatism may provide heat source and produce geological fluids, which are very important for gold mineralization. Exhumation in the Mesozoic caused the uplift of the deposit towards the ground surface.

  10. 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

  11. Granitoids of the Dry Valleys area, southern Victoria Land, Antarctica : plutons, field relationships, and isotopic dating

    International Nuclear Information System (INIS)

    Detailed mapping throughout much of the Dry Valleys area indicates the region is underlain by 15 major granitoid plutons and numerous smaller plugs and dikes. Intrusive relationships of these plutons and dikes indicate repeated intrusion of superficially similar granitoids at different times. Sufficient internal lithologic variation occurs within individual plutons, to allow correlation with several of the previously defined granitoid units based on lithologic character. Consequently, previous subdivision schemes based on lithology are no longer tenable and are here replaced with a subdivision scheme based on the identification of individual plutons. The elongate, concordant Bonney, Denton, Cavendish, and Wheeler Plutons, which range in composition between monzodiorite and granodiorite, are the oldest relatively undeformed plutons in the Dry Valleys area. Each pluton is characterised by flow alignment of K-feldspar megacrysts, hornblende, biotite, and mafic enclaves. Field relationships and radiometric dating indicate these are deep-level plutons, emplaced synchronous with upper amphibolite facies metamorphism of the adjacent Koettlitz Group between 589 and 490 Ma ago. Elongate, discordant plutons of equigranular homogeneous biotite granodiorite and granite (Hedley, Valhalla, St Johns, Suess) were subsequently emplaced by stoping at a relatively high crustal level at 490 Ma. These eight plutons are cut by numerous swarms of Vanda mafic and felsic porphyry dikes. The ovoid, discordant, high level Pearse, Nibelungen, Orestes, Brownworth, Swinford, and Harker Plutons, emplaced between c. 486 and 477 Ma, display mutually crosscutting relationships with the youngest of the Vanda dikes. These younger plutons range in composition between monzonite and granite. Some are characterised by K-feldspar megacrystic textures superficially similar to some of the oldest concordant plutons. (author). 57 refs.; 2 tabs.; 4 figs

  12. Uranium in the Copper King Mine, Black Hawk No. 1 Claim, Larimer County, Colorado

    Science.gov (United States)

    Granger, Harry Clifford; King, Robert Ugstad

    1951-01-01

    Radioactive rock was discovered on the dump of the Copper King mine, sec. 8, T. 10 N., R. 72 W., Larirrier County, Colo., in the summer of 1949. The mine had been prospected intermittently for copper and zinc since 1,916, but there is no record that ore was produced. The country rock is pre-Cambrian granite containing many schist inclusions and narrow pegmatite dikes. Pitchblende disseminated in chlorite and sulfides was deposited in an obscure vein system during an intermediate stage of mineralization. This stage was preceded by biotitic alteration of amphiboles and sulfide deposition. The latest stage of mineralization is represented-by the limonitic dense quartz vein followed during mining. The uranium-bearing vein is about 2-3 feet wide and the dense quartz vein is less than 6 inches wide. Both veins are bordered by 1-3 feet of biotite- and sulfide-bearing granite and arriphibole schist. The uranium content of 26 samples taken in the mine and on the dump ranges from 0.002 to 1.40 percent. These samples contained as much as 2.97 percent copper and 5.96 percent zinc. The general outlook for further prospecting near the Copper King shaft is not favorable, because much of the 'immediately surrounding area has been thoroughly investigated without finding abnormal radioactivity. The most favorable environment for concentration of uranium minerals appears to have been in or near schist inclusions in granite, and further exploration in nearby prospects may result in the discovery of other uranium-bearing deposits. In the Copper King mine, additional exploration would aid in determining the extent of the uranium-bearing material.

  13. Infrared microspectroscopy analysis of water distribution in deformed and metamorphosed rocks

    Science.gov (United States)

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

    1995-05-01

    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.

  14. New data on the paleocene section in Blateshnitsa Graben (Kraishte region, Western Bulgaria)

    International Nuclear Information System (INIS)

    Blateshnitsa Graben is superimposed upon a basement of allohtonous Palaeozoic anhimetamorphics and paraautohtonous Triassic and Jurassic sediments. According to the data from the Zemen borehole, the Graben is filled mainly by alluvial conglomerates and breccia conglomerates (in the lower part of the section) with rare interbeds, of sandstones, fine layered shales and three acid (to intermediate?) pyroclastic beds (in the upper part). K-Ar age of biotite crystalloclasts from the upper part (1.2 m) of the first pyroclastic bed was used to date the Blateshnitsa section. The data obtained (33.12 ± 1.50 Ma) indicate a Late Priabonian, Early Rupelian (or close to Priabonian - Rupelian boundary) age of the pyroclastic emission and accumulation. This first direct dating confirms the existing ideas on the age of Blateshnitsa Graben fill. The dated pyroclastics are transformed into zeolite rocks containing up to 35 % zeolite of heulandite type. They are formed at the expense of acid (to intermediate?) fine ash pumice fragments and glass shards, containing also a high amount (20-40 %) of crystalloclasts (mainly plagioclase and biotite, together with amphibole and quartz) and rare lithic fragments. The source of the pyroclastic component is under discussion. Redeposition of a loose fresh ash tephra by winds or current water is the most probable mechanism of its accumulation in fresh water Paleogene lake. It is supposed that the zeolitization took place in a hydrologically open system at shallow burial depths and in conditions, of humid and moderately warm climate. The Blateshnitsa zeolite rocks are a new find of such type of rocks for the territory of Bulgaria and the first Bulgarian occurrence formed in fresh water environment. Some problems on the Western Bulgaria Paleogene chrono- and lithostratigraphy are discussed. (Original)

  15. Geochemical Constraints For The Genesis Of A-type Granite From Southeastern Korea

    Science.gov (United States)

    Koh, J.; Yun, S.

    2008-12-01

    Mineralogical, geochemical characteristics and Sr-Nd isotopic data are presented for the Namsan A-type granite and Gyeongju I-type granitic rocks in Gyeongju area, Gyeongsan Basin, Korea. The Namsan A-type granite is alkali feldpar granite and consists of quartz, perthite, sodic amphibole (riebeckitic arfvedsonite), annite, and fluorite. Quartz and perthite occurs as early crystallized phase, and others as interstitial phase. The Gyeongju I-type granitic rocks are divided into four plutons based on their petrographical features; The Maseoksan biotite granite(MBG), Tohamsan biotite granite(TBG), Gyeongju hornblende biotite granodiorite(GHBGd), and Gyeongju biotite porphyritic granite(GBPG). Aplitic dykes intrude these granite rocks. Petrochemically, the Namsan alkali feldspar granite is distinctly different from other I-type granites, and is characterized by higher Fe2O3, Fe2O3T, Na2O, Rb, Nb, Y, Ce, Ga, Zr contents and Ga/Al2O3 ratio, and lower TiO2, Al2O3, MgO, CaO, P2O5, Ba and Sr contents. The rocks show flat chondrite-normalized REE patterns with strong Eu negative anomaly. The MBG and TBG, the GHBGd, and the GBPG show the geochemistry of general calc-alkaline I-type granitic rocks, and they have almost constant Ga/Al2O3 ratio and LREE-enriched pattern. Although the aplitic dykes of the Maseoksan and Tohamsan biotite granites are extensively fractionated, compared with the Namsan A-type granite, the former has significantly lower large highly charged cations such as Nb, Y, Ce, Ga, Zr. This geochemical feature suggests that the Namsan A-type granite can not be derived from MBG and TBG magma by fractional crystallization process. Geochemical data indicate that the GBPG was derived from the GHBGd magma by fractionation of amphibole, biotite, plagioclase, sphene, and magnetite. On discrimination diagrams, the Namsan A-type granite is plotted in the field of anorogenic, within plate granites, whereas I-type granitic rocks in the field of subduction-related, volcanic

  16. Provenance of the heavy metals in sand sediments of the Oman Sea (Sistan and Baluchestan district

    Directory of Open Access Journals (Sweden)

    Maryam Soleimani

    2015-04-01

    Full Text Available Introduction Mineral composition of source rock is one of the most important factors for concentration and distribution of heavy metals in sediments. Therefore, study on distribution of these elements and the related minerals in sediments provides information about natural origin of elements. Moreover, the interpretation of origin and distribution of sandy sediments is considerably enhanced by mineralogical and geochemical studies of these sediments. The main objective of this research is to evaluate distribution of Zn, Cu, Sr, Cd, Fe and Mn in sand sediments of the Oman Sea, their relationship with mineral composition of the sediments and also determining their provenance. Materials and Methods Sampling of surface sediments of the Oman Sea was performed in 16 sampling stations. Heavy minerals and rock fragments of the sediments in fine and coarse sand sizes respectively were qualitatively and quantitatively studied by polarizing microscope (Folk, 1974; Pettijohn et al., 1981; Tucker, 1988. Concentration of the heavy metals were also analyzed by AAS method (Mico et al., 2008. Result Mineralogical composition of the studied sediments contain quartz, feldspars and heavy minerals in their order of abundances. The rock fragments consist of sedimentary, igneous and metamorphic in their order of frequencies as well. The concentrations of the studied heavy metals (in ppm in the sediments are Cd (1.42, Cu (9.99, Zn (36.72, Sr (181.18, Mn (377.33 and Fe (20247.55 in their order of abundances. Distribution of the Zn concentration generally shows decreasing trend from west of the study area to the Guatr Bay. The concentrations of Zn and Cu show close relationship with the frequencies of biotite and muscovite. The Cu concentration also shows positive correlation with the Zn and Fe concentrations. Distribution of the Sr and Cd concentrations is similar to variation of the calcium carbonate content. The Cd and Sr concentrations also show positive correlation

  17. An interpretation of the metamorphic history of the Alpine Schist, northern Westland

    International Nuclear Information System (INIS)

    This thesis presents results of an investigation into the metamorphism of a section of the Alpine Schist in North Westland, between the Crooked River in the north and Griffin Creek in the south. The Alpine Schist is a narrow belt of dominantly quartzofeldspathic schist that has been rapidly extruded along the Alpine Fault. The schist is at its highest grade (garnet-oligoclase) immediately east of the Alpine Fault and grades to biotite zone facies at a distance of c. 3 km west of the fault in this study. Field mapping, optical microscopy, whole-rock analyses, mineral chemistry and zoning, geothermobarometry, stable isotopes and Sm-Nd age determinations for garnet growth zones have enabled a well constrained metamorphic history to be interpreted. As part of this an estimate for the timing and P-T conditions of the peak of Alpine Schist metamorphism in the study area has also been possible. Large polyphase garnet porphyroclasts sampled from mylonitised Alpine Schist at Macs Creek record up to five zones of garnet growth. Textures within these garnets indicate that at least some garnet growth predated the development of the alpine foliation and that garnet growth occurred at least sporadically through most of the Cenozoic, finishing with garnet rims overgrowing the developing mylonitic foliation. Garnet separates were prepared and sent to VIEPS Radiogenic Isotope Laboratory, La Trobe University, Melbourne, Australia for Sm-Nd garnet growth age determinations. For the core (zone 1), a two pint garnet-whole rock age of 98 ± 8.1 Ma indicates garnet growth in the mid-Cretaceous, during a time of widespread extension with scattered plutonism and volcanism in the New Zealand region, which predates the opening of the Tasman Sea by c. 20 Ma. A second Sm-Nd garnet growth age was obtained from zone 4, just inside the synmylonitic outermost rim (zone 5) and show that Alpine Schist garnet growth occurred in the Late Cenozoic. The broad age of 12 ± 37 M (MSWD = 0.89) for zone 4

  18. Unravelling the complex interaction between mantle and crustal magmas encoded in the lavas of San Vincenzo (Tuscany, Italy). Part I: Petrography and Thermobarometry

    Science.gov (United States)

    Ridolfi, Filippo; Braga, Roberto; Cesare, Bernardo; Renzulli, Alberto; Perugini, Diego; Del Moro, Stefano

    2016-02-01

    The San Vincenzo Volcanic Complex was emplaced ~ 4.4 Ma. ago and consists of cordierite-bearing lavas which are the result of a complex interaction between mantle-derived and crustal anatectic magmas. The lavas are mostly characterized by porphyritic, glassy peraluminous rhyolites hosting variable contents of magmatic enclaves (clinopyroxene-bearing latites and amphibole-bearing clinopyroxene crystal mushes), sialic and ultramafic cognates (syenogranites, anorthosites, cordierite-biotite and pyroxenite inclusions), and crustal rocks (sillimanite-cordierite xenoliths, cordierite and biotite xenocrysts) of centimetric-to-millimetric size. Mineral chemistry shows large variations as well. Plagioclase and sanidine are represented respectively by An21-79Or1-13 and An≤ 1Or57-77. Cordierite has a Mg# of 51-78%, while garnet shows almandine compositions with low CaO (≤ 2 wt.%) and variable MnO contents (1-5 wt.%). Clinopyroxene indicates large ranges of Mg# (68-92%) and Al2O3 (0.5-6.3 wt.%), and relatively high CaO contents (up to 24 wt.%); orthopyroxene shows both ferroan enstatite (Mg# = 60-78%) and magnesian ferrosilite (Mg# = 39-44%) compositions; whereas amphibole shows only Mg-rich calcic compositions. On the basis of textural characteristics, as well as Ti and XMg variations, we have identified six different types of biotite associated with oxide minerals such as ilmenite and spinels of both aluminium (Al > 1 in Y site) and iron (Fe > 1 in Y site) subgroups. Compositional/textural relationships indicate crystallization at both equilibrium and disequilibrium conditions. Minerals with euhedral habits and homogeneous compositions usually occur in the same thin sections of partly-equilibrated crustal xenoliths (and xenocrysts) and zones of "active" mixing between mantle-derived and crustal magmas characterized by "needle-like" and skeletal microlites, and subhedral microphenocrysts of amphibole and biotite. These hybrid-mixed features, as well as the occurrence of

  19. The petrography, geochemistry, petrogenesis, and geochronology of the Singo Granite, Western Central Uganda

    International Nuclear Information System (INIS)

    As for all other Ugandan granites/granitoids, information regarding the geochemical characteristics, petrogenesis, tectonic setting, classification, and formation age of the Singo granite is limited, or in some cases, lacking. In this study, field relationships and modern petrographic, geochemical, and geochronogical techniques were employed to obtain more information for the Singo granite on the above topics. X-ray fluorescence spectrometry and neutron activation analysis were used to obtain whole-rock major and trace element abundances, electron microprobe and a scanning electron microscope for mineral chemistry and thermal ionization mass spectrometry for isotopic ratio measurements and age determinations of selected samples from the Singo granite. The results show that the Singo granite is a batholithic body intruded into sediments that have experienced low-grade regional and contact metamorphism. It occurs in a number of texturally and compositionally different subtypes: (a) a pink, very coarse-grained, and porphyritic granite (PPG), (b) a pinkish gray very coarse-grained granite, (c) a pinkish gray medium-grained granite, (d) a pinkish fine/aplitic to medium-grained muscovite granite (MG), and (e) a fine- to medium-grained biotite granite (BG). The PPG forms the largest part of the Singo batholith and the phenocrysts occasionally show magmatic flow alignment. The BG has mafic enclaves, is richer in biotite, calcic plagioclase, and zircon relative to other varieties, and forms most of the pluton margin, but is occasionally found within the main body itself. The Singo granite, therefore, shows zonation in texture, colour, and mineral composition. The mineralogy is generally uniform: K-feldspar, plagioclase (An0.4-38.3), quartz, biotite, muscovite and opaques. K-feldspars, plagioclase and quartz constitute both the phenocrysts and the matrix. Minor phases include zircon, apatite, sphene, monazite, xenotime, opaques and thorite, most of which are inclusions in

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

    Science.gov (United States)

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

    2011-01-01

    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