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Sample records for allanite

  1. Allanite behaviour during incipient melting in the southern Central Alps

    DEFF Research Database (Denmark)

    Gregory, C.J.; Rubatto, D.; Hermann, J.;

    2012-01-01

    in metamorphic allanite with low Th/U (Gabudianu et al., 2009). All of these effects have significant implications for allanite geochronology. This paper details the response of allanite to incipient melting and its performance as a chronometer by examining its occurrence, trace element composition, and age...... to amphibolite-grade rocks of the SSB (Burri et al., 2005). In situ melting of granitic gneisses occurred in the mid-crust at temperatures close to the wet granite solidus (~630 °C) and in some cases produced up to ~30 vol.% leucosomes (Burri et al., 2005). At outcrop, leucosomes are variably deformed...... of allanite was conducted over five separate sessions using the SHRIMP II and SHRIMP RG (Reverse Geometry) ion microprobes at the Research School of Earth Sciences, ANU. Analyses were performed on allanite in polished grain mounts with a 2.0–3.5 nA, 10 kV primary beam focused through a ~100 µm aperture...

  2. Preservation of Permian allanite within an Alpine eclogite facies shear zone at Mt Mucrone, Italy: Mechanical and chemical behaviour of allanite during mylonitization

    DEFF Research Database (Denmark)

    Cenki-Tok, Benedicte; Oliot, E.; Berger, Alfons;

    2011-01-01

    This study addresses the mechanical and cehmical behavior of allanite during shear zone formation under high-pressure metamorphism. Understanding physico-chemical processes related to the retention or resetting of Pb isotopes in allanite during geological processes is essential for robust......, and they were thus chemically and mechanically shielded during Alpine mylonitization. In undeformed samples (8a and 8b), two populations of epidote group minerals were found. Allanite forms either coronas around Permianmonazite or individual grains with patchy zoning. Both types yield Permian ages...... (208Pb/232Th age: 291±5 Ma). On the other hand, grains of REE-rich clinozoisite of Cretaceous age are found in undeformed rocks. These grains appear as small fragments with embayed surface outlines and minute satellites or rims around Permian allanite. These (re)crystallized grains are Sr-rich and show...

  3. Annealing induced recrystallization of radiation damaged titanite and allanite

    International Nuclear Information System (INIS)

    in the titanite structure. Hence, the planes containing Si-O-Ti-O bond rings are less susceptible to a self-accumulation of radiation-induced defects resulting in the development of amorphous regions as compared to the perpendicular plane containing Ti-O bond chains. Multistep annealing gradually suppresses the structural defects in the crystalline fraction of the titanite as the improvement of the SiO4-TiO6 connectivity within planes near perpendicular to the TiO6 chains reaches saturation near 900 K. Annealing-induced recrystallization of the radiation-induced amorphous nanoregions takes place in the temperature range between approximately 650 and 950 K, with a maximum near 750 K. To determine the influence of radiation damage on the behavior of the elastic material properties of titanite, nanoindentation measurements were performed on partially metamict titanite (sample E2312) and for comparison additionally on nearly undamaged crystalline titanite (Rauris sample) and titanite glass. Metamict titanite E2312 shows hardness (H) and elastic modulus (E) values close to those of titanite glass. Rauris titanite shows strong anisotropy and the H and E values are clearly larger than those of E2312. Thermally induced stepwise recrystallization of metamict titanite E2312 leads to a decrease in the hardness until approximately 950 K and afterwards to an increase at higher temperatures, while the elastic modulus increases continuously (H and E values measured always at room temperature). Changes of the hardness and elastic modulus are related to increasing long-range order and vanishing amorphous interface areas in the titanite structure. In further studies the structural recovery of the metamict epidot group mineral allanite (sample number R1) produced by thermal annealing was followed by powder X-ray diffraction, single-crystal synchrotron X-ray diffraction and infrared spectroscopy. Allanite contains in contrast to titanite structural OH groups. But no evidences for a

  4. Direct spectrographic determination of major amounts of some rare earths and thorium in allanite

    International Nuclear Information System (INIS)

    A d.c. arc spectrographic method for direct estimation of Ce, Eu, Gd, La, Th and Y quantitatively and Nd and Sm semi-quantitatively in allanite, a complex rare-earth silicate mineral, is described. Using 3.4 m. Jarrell-Ash grating spectrograph, spectra of synthetic standards and samples mixed with specpure graphite-internal standard mixture in 1:5 ratio, are photographed on Kodak SA-1 emulsion from 2720 A to 3330 A. Pd is used as an internal standard. The determination range of most of the elements cover the range of their natural abundance in allanites. The average standard deviation of the method is +- 15%. The analysis results of one natural allanite sample by the present method are compared with those obtained by XRF method. (author)

  5. Spectrographic determination of some non-rare-earth trace elements in allanite

    International Nuclear Information System (INIS)

    An emission spectrographic method for estimating traces of Be, Pb, Sn, Ga, Mn, Nb, Ti, Mo, V, Zr, Cu and Sc in allanite, a complex rare earth mineral, is described. Using 3.4 m Jarrell-Ash grating spectrograph, the spectra of standards and samples mixed with specpure graphite-internal standard mixture, are photographed in the spectral region 2275-3525 A in first order. Silicon and palladium are used as internal standard elements, for the estimation of these elements. Most of the trace elements are determined in the range of their natural abundance in allanites. The mean standard deviation of the method is found to be +- 14%. (author)

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

    Science.gov (United States)

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

    2012-12-01

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

  7. Resolving the age of Wilson Creek Formation tephras and the Mono Lake excursion using high-resolution SIMS dating of allanite and zircon rims

    Science.gov (United States)

    Vazquez, J. A.; Lidzbarski, M. I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and interbedded rhyolitic tephras yield discordant 14C and 40Ar/39Ar results due to open-system effects, carbon reservoir uncertainties, as well as abundant xenocrysts entrained during eruption. Ion microprobe (SIMS) 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yields ages that effectively date eruption of key tephra beds and resolve age uncertainties about the Wilson Creek stratigraphy. To date the final several micrometers of crystal growth, individual allanite and zircon crystals were embedded in soft indium to allow sampling of unpolished rims. Isochron ages derived from rims on coexisting allanite and zircon (± glass) from hand-selected pumiceous pyroclasts delimit the timing of Wilson Creek sedimentation between Ashes 7 and 19 (numbering of Lajoie, 1968) to the interval between ca. 27 to ca. 62 ka. The interiors of individual allanite and zircon crystals sectioned in standard SIMS mounts yield model 238U-230Th ages that are mostly Mono Craters volcanism and/or intrusions. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields a rim isochron age of ca. 41 ka indicating that the recorded event is instead the Laschamp excursion. The results are consistent with a depositional chronology from correlation of relative paleointensity (Zimmerman et al., 2006) that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to climate change

  8. Late Paleozoic evolution of the South Tien Shan: Insights from P-T estimates and allanite geochronology on retrogressed eclogites (Chatkal range, Kyrgyzstan)

    Science.gov (United States)

    Loury, Chloé; Rolland, Yann; Cenki-Tok, Bénédicte; Lanari, Pierre; Guillot, Stéphane

    2016-05-01

    In the South Tien Shan range (Kyrgyzstan), the Late Paleozoic geodynamic evolution remains debated especially to the west of the Talas-Fergana fault (TFF) fault where suture-related high-pressure (HP) rocks are scarce. We provide new petrological and geochronological data on garnet amphibolites from the Chatkal range, to the west of the TFF, northwest of the South Tien Shan suture. These rocks are retrogressed eclogites. We used a micro-mapping approach combined with forward modeling and empirical thermobarometry to decipher the P-T path of these amphibolitized eclogites. The metamorphic peak conditions culminated at 490 ± 50 °C and 18.5 ± 2 kbar and were followed by higher temperature retrogression (∼560 °C at 11-7 kbar). In order to constrain the age of the HP stage, we dated allanite crystals texturally coeval to the HP mineral assemblage. Allanite grains dated in situ with a U-Pb LA-ICPMS methodology yield an age of 301 ± 15 Ma. Compared with previously published data for the east of the TFF, these P-T constraints allow improving the understanding of the Late Paleozoic geodynamic evolution of the South Tien Shan. To the east of TFF, the Turkestan Ocean closed around 320 Ma with the collision of the Tarim Craton with the Kazakh microcontinent. To the west of TFF, the Turkestan Ocean closed around 300 Ma, when the Alai block collided with the Kazakh microcontinent. This later collision involved nappe-stacking and intense subvertical folding in the western South Tien Shan. This complex folding explains the S-shape of the suture to the west of the TFF that cannot be observed in the eastern part. These new data allow us to propose a distinct tectonic evolution of the two sides of the TFF, which suggests that this fault was a major transform fault before being a strike-slip intra-continental fault.

  9. Experimental constraints on the monazite-fluorapatite-allanite and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote phase relations as a function of pressure, temperature, and Ca vs. Na activity in the fluid

    Science.gov (United States)

    Budzyń, Bartosz; Harlov, Daniel E.; Majka, Jarosław; Kozub, Gabriela A.

    2014-05-01

    Stability relations of monazite-fluorapatite-allanite and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote are strongly dependent on pressure, temperature and fluid composition. The increased Ca bulk content expands stability field of allanite relative to monazite towards higher temperatures (Spear, 2010, Chem Geol 279, 55-62). It was also reported from amphibolite facies Alpine metapelites, that both temperature and bulk CaO/Na2O ratio control relative stabilities of allanite, monazite and xenotime (Janots et al., 2008, J Metam Geol 26, 5, 509-526). This study experimentally defines influence of pressure, temperature, high activity of Ca vs. Na in the fluid, and high vs. moderate bulk CaO/Na2O ratio on the relative stabilities of monazite-fluorapatite-allanite/REE-rich epidote and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote. This work expands previous experimental study on monazite (Budzyń et al., 2011, Am Min 96, 1547-1567) to wide pressure-temperature range of 2-10 kbar and 450-750°C, utilizing most reactive fluids used in previous experiments. Experiments were performed using cold-seal autoclaves on a hydrothermal line (2-4 kbar runs) and piston-cylinder apparatus (6-10 kbar runs) over 4-16 days. Four sets of experiments, two for monazite and two for xenotime, were performed with 2M Ca(OH)2 and Na2Si2O5 + H2O fluids. The starting materials included inclusion-free crystals of monazite (pegmatite, Burnet County, TX, USA) or xenotime (pegmatite, Northwest Frontier Province, Pakistan) mixed with (1) labradorite (Ab37An60Kfs3) + K-feldspar + biotite + muscovite ± garnet + SiO2 + CaF2 + 2M Ca(OH)2 or (2) albite (Ab100) + K-feldspar + biotite + muscovite ± garnet + SiO2 + CaF2 + Na2Si2O5 + H2O. 20-35 mg of solids and 5 mg of fluid were loaded into 3x15 mm Au capsules and arc welded shut. The monazite alteration is observed in all runs. Newly formed REE-rich fluorapatite and/or britholite are stable in all experimental P-T range in the

  10. Precambrian crustal evolution and Cretaceous–Palaeogene faulting in West Greenland: 207Pb-206Pb dating of magnetite, monazite and allanite in the central and northern Nagssugtoqidian orogen, West Greenland

    Directory of Open Access Journals (Sweden)

    Frei, Robert

    2006-12-01

    Full Text Available Pb-isotopic data for magnetite from amphibolites in the Nagssugtoqidian orogen, central West Greenland, have been used to trace their source characteristics and the timing of metamorphism. Analyses of the magnetite define a Pb-Pb isochron age of 1726 ± 7 Ma. The magnetite is metamorphic in origin, and the 1726 Ma age is interpreted as a cooling age through the closing temperature of magnetite at ~600°C. Some of the amphibolites in this study come from the Naternaq supracrustal rocks in the northern Nagssugtoqidian orogen, which host the Naternaq sulphide deposit and may be part ofthe Nordre Strømfjord supracrustal suite, which was deposited at around 1950 Ma ago.Pb-isotopic signatures of magnetite from the Arfersiorfik quartz diorite in the central Nagssugtoqidian orogen are compatible with published whole-rock Pb-isotopic data from this suite; previous work has shown that it is a product of subduction-related calc-alkaline magmatism between 1920 and 1870 Ma. Intrusion of pegmatites occurred at around 1800 Ma in both the central and the northernparts of the orogen. Pegmatite ages have been determined by Pb stepwise leaching analyses of allanite and monazite, and source characteristics of Pb point to an origin of the pegmatites by melting of the surrounding late Archaean and Palaeoproterozoic country rocks. Hydrothermal activity took place after pegmatite emplacement and continued below the closure temperature of magnetite at 1800–1650 Ma. Because of the relatively inert and refractory nature of magnetite, Pb-isotopic measurements from this mineral may be of help to understand the metamorphic evolution of geologicallycomplex terrains.

  11. Pegmatitas con allanita-(Ce vinculadas al ortogneispiroxénico de la Quebrada del Río Suquía, Sierras Chicas de Córdoba Pegmatites with allanite-(Ce related tothe orthopyroxene-bearing orthogneiss of the Quebrada del Río Suquía, SierrasChicas de Córdoba

    Directory of Open Access Journals (Sweden)

    Francisco Locati

    2009-06-01

    /(Fe total+Mg de 0.48 a0.47], allanite-(Ce, and occasionally microcline with an orderedstructural state. Allanite-(Ce occurs as euhedral black crystals up to 16 cmlong bounded by the forms {001} and {100}. It is metamict due to its Th contentand shows optical and chemical zoning. LaN/YbN and LaN/GdNratios show a core-to-rim decrease (34-19 and 3.1-2.1 respectively, while Thincreases towards the rim (1.66-2.59% ThO2. Dominant substitutionmechanisms are Ca2+ + Fe3+ ETR3+ + Fe2+, Si4++ M2+ Al3+ + Fe3+ and probably 2ETR3+ Ca2++ Th4+ (where REE stands for rare-earth elements and M2+is a divalent cation. The pyroxenebearing orthogneiss and the pegmatitesderive from the same magma. The presence of allanite-(Ce is a consequence ofREE enrichment in the pegmatite melt induced by the delay or suppression ofmonazite crystallization, this itself being partially due to the earlyprecipitation of apatite which takes up P from the melt.

  12. Allanite-monazite-xenotime-zircon-apatite assemblage in two-mica granites of the Moldanubian (South Bohemian) batholith

    Czech Academy of Sciences Publication Activity Database

    René, Miloš

    -, - (2010), s. 460. ISSN 0365-8066. [IMA. 21.08.2010-27.08.2010, Budapest] R&D Projects: GA MŠk ME10083 Institutional research plan: CEZ:AV0Z30460519 Keywords : granite * accessory minerals * Bohemian Massif Subject RIV: DB - Geology ; Mineralogy

  13. Physico-chemical control on the REE minerals in chloritoid-grade metasediments from a single outcrop (Central Alps, Switzerland)

    DEFF Research Database (Denmark)

    Janots, Emilie; Berger, Alfons; Engi, Martin

    2011-01-01

    detrital core rimmed by newly formed monazite. Significant arsenic contents are found in newly formed monazite, xenotime and apatite. Monazite texture and composition suggest (re)crystallization by pressure solution, at an oxygen fugacity sufficient to partly oxidize As, S, U, and Fe. Whether or not......This study assesses the effects of fluid, whole-rock composition and oxygen fugacity, on the texture and composition of monazite, allanite, and xenotime. For this purpose, these were investigated in 13 monometamorphic metasediments from a single locality of the Central Alps (Switzerland), which......). Allanite formation is texturally coeval with apatite, chloritoid and xenotime, during the main tectono-metamorphic stage. Allanite formation implies significant mass transfer of Ca and P via a fluid phase, which is not clearly related to advective transport. In Ga06, elongate monazite grains have a...

  14. Některé informace z koncentrátů těžkých minerálů z melechovského masivu

    Czech Academy of Sciences Publication Activity Database

    Procházka, V.; Žáček, M.; Chlupáčová, M.; Matějka, D.; Korbelová, Zuzana; Klementová, Mariana

    2011-01-01

    Roč. 2011, - (2011), s. 172-176. ISSN 0514-8057 Institutional research plan: CEZ:AV0Z30130516; CEZ:AV0Z40320502 Keywords : heavy minerals * uraninite * tourmaline * allanite Subject RIV: DB - Geology ; Mineralogy http://www.geology.cz/zpravy/obsah/2010/zpravy-2010-39.pdf

  15. 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

  16. Genesis of the central zone of the Nolans Bore rare earth element deposit, Northern Territory, Australia

    Science.gov (United States)

    Schoneveld, Louise; Spandler, Carl; Hussey, Kelvin

    2015-08-01

    The Nolans Bore rare earth element (REE) deposit consists of a network of fluorapatite-bearing veins and breccias hosted within Proterozoic granulites of the Reynolds Range, Central Australia. Mineralisation is divided into three zones (north, central, and south-east), with the north and south-east zones consisting of massive REE-bearing fluorapatite veins, with minor brecciation and carbonate infill. The central zone is distinctively different in mineralogy and structure; it features extensive brecciation, a high allanite content, and a large, epidote-rich enveloping alteration zone. The central zone is a reworking of the original solid apatite veins that formed during the Chewings Orogeny at ca. 1525 Ma. These original apatite veins are thought to derive from phosphate-rich magmatic-hydrothermal fluid exsolved from as-yet unrecognised alkaline magmatic bodies at depth. We define four ore breccia types (BX1-4) in the central zone on the basis of detailed petrological and geochemical analysis of drillcore and thin sections. BX1 ore comprises fluorapatite with minor crackle brecciation with carbonate infill and resembles ore of the north and south-east zones. Breccia types BX2, BX3, and BX4 represent progressive stages of ore brecciation and development of calc-silicate mineral (amphibole, epidote, allanite, calcite) infill. Comparison of bulk ore sample geochemistry between breccia types indicates that REEs were not mobilised more than a few centimetres during hydrothermal alteration and brecciation. Instead, most of the REEs were partitioned from the original REE fluorapatite into newly formed allanite, REE-poor fluorapatite and minor REE carbonate in the breccias. Negative europium (Eu) anomalies in the breccia minerals are accounted for by a large positive Eu anomaly in epidote from the alteration zones surrounding the ore breccias. This observation provides a direct link between ore recrystallisation and brecciation, and the formation of the alteration halo in

  17. Fluid-induced dissolution breakdown of monazite from Tso Morari complex, NW Himalayas: evidence for immobility of trace elements

    Science.gov (United States)

    Upadhyay, Dewashish; Pruseth, Kamal Lochan

    2012-08-01

    Primary igneous monazite from the Polokongka La granite of the Tso Morari complex in the western Himalayas has been partially replaced by a three-layered corona of metamorphic fluor-apatite, allanite + U- and Th-bearing phases (huttonite + brabantite), and epidote. The alteration is related to high-pressure amphibolite-facies (10-11 kbar and 587-695 °C) fluid-induced retrogression of the ultra-high-pressure granite during exhumation after India-Asia collision. The corona textures can be explained by pseudomorphic partial replacement of the original monazite to apatite and allanite via a fluid-mediated coupled dissolution-reprecipitation process. Mass balance calculations using the volume proportions and compositions of coronal minerals show that the REE, U, Th, Pb, Ba and P were conserved and not transported outside the alteration corona. The formation of fluor-apatite, allanite, huttonite and coffinite from monazite and the immobility of REE, U and Th require an influx of alkali- and F-bearing, Ca-rich fluid having high Ca/Na into the corona. We are aware of only two other occurrences of such alteration textures, and these have several similarities in terms of geodynamic setting and P-T histories of the host rocks. We suggest that there may be a common mechanism of exhumation style, and source and composition of fluids during retrogression of granitoid rocks in collisional orogens and that such breakdown textures can be used to identify metagranites that have experienced high-P metamorphism in continental collision zones, which is otherwise difficult to constrain due to the high variance of the mineral assemblages in these rocks.

  18. Accessory mineral U-Th-Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

    Science.gov (United States)

    Simon, J.I.; Vazquez, J.A.; Renne, P.R.; Schmitt, A.K.; Bacon, C.R.; Reid, M.R.

    2009-01-01

    We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ??? 230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ???85 ka rhyolites yielded ages between ???100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ???200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (???10's to 100's ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies. ?? The Author(s) 2009.

  19. Application of Alpha-Track Mapping to Genesis of Uranium-Mineralization, Gabal El-Bakriya, Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    The Solid State Nuclear Track Detector (SSNTD) Kodak-CN-85 was used to show the genesis and distribution of the radioactive element in Gabal El-Bakriya different granitic and U-mineralized granitic varieties. In the non mineralized granites the track mapping showed that U and Th are confined mostly to the accessory U-bearing minerals such as epidote (allanite), zircon and opaque. In the U-mineralized hydrothermally altered granites, the alpha tracks showed that the u and Th are displayed by (Fe, Mn) oxides filling the grain fractures, interstitial micas and associated fluorite and amorphous silica filling vugs and fractures. Fluorite may also display alpha-tracks probably due to minute radioactive inclusions. Uranium-fixation followed the hydrothermal stages causing desilicification and muscovitization of biotite and feldspars and accordingly U, F, Fe and Ca were liberated. The Fe-oxides adsorb U and Ca reacts with F to form fluorite. Excess Ca reacts with uranyl ions presence of amorphous silica to form uranophane, which is deposited as thin films along fractures. Also the minute radioactive inclusions such as zircon, columbine and allanite are liberated from micas and may later be included into the newly formed fluorite

  20. Rare-earths and yttrium mineral stream sands at Rangampeta, North Arcot district, Tamil Nadu

    International Nuclear Information System (INIS)

    Radiometric survey along the Goddaru Vanka stream near Rangampeta of North Arcot district, Tamil Nadu has brought to light an appreciable concentration of rare-earths (RE) - and yttrium-minerals (allanite, monazite and xenotime) in the stream sands with feed samples assaying 0.034-0.35% CeO2 and 0.003-0.34% Y2O3, and their non-magnetic table concentrates (1-10 wt% of feed) assaying 1.13-10.30% CeO2 and 0.25-1.37% Y2O3. Of the different heavy minerals, magnetite shows positive correlation (r=0.93 to 0.99) with allanite, xenotime, total RE- and Y-minerals, total heavy minerals, CeO2 and Y2O3 of the feed samples. The results also confirm the effectiveness of radiometric and magnetic surveys in delimiting RE- and Y-minerals in the stream sands. (author). 4 refs., 1 fig., 1 tab

  1. Fluid components in accessory minerals of Pan-African granitoids in the S(o)r Rondane Mountains, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    LI Zi-long; CHEN Han-lin; YANG Shu-feng; TAINOSHO Yoshiaki; SHIRAISHI Kazuyuki; OWADA Masaaki

    2007-01-01

    Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids(Group-Ⅰ granitoids, Group-Ⅱ granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mountains, East Antarctica were precisely measured by an electronic microprobe analyzer in this study. Apatites in the granites have commonly high fluorine contents. However, fluorine contents from the Group-Ⅰ, Group-Ⅱ granitoids and Mefjell Plutonic Complex (MPC) are of important variation, which F contents (3.21~7.20 wt%) in apatite from the Group-Ⅱ granitoids are much higher than those from the Group-Ⅰ granitoids (1.22~3.60 wt%) and the MPC (3.21~4.11 wt%). Titanite in the MPC has a low fluorine content (0.23~0.50 wt%), being less than those in the Group-Ⅰ granitoids (2.28 wt%) and Group-Ⅱ granitoids (1.85~2.78 wt%). Fluorine in allanite in the Group-Ⅱ granitoids seems to have much lower contents than those from the Group-Ⅰ granitoids and the MPC. Higher fluorine contents in the titanite from the Group-Ⅱ granitoids may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt, but may not be indicative of original magma contents based on its petrographic feature. Due to very lower chlorine contents from all of accessory minerals, the authors suggest that titanite and apatite with higher fluorine contents in the Group-Ⅱ granitoids have much lower H2O (OH) contents compared with those in the Group-Ⅰ granitoids according to the partition among (F, Cl, OH).Fluorine contents in whole-rock samples show a variation from the higher in the Group-Ⅰ granitoids to the lower in the Group-Ⅱ granitoids and the MPC, which are consistent with the changes of those from the biotite and hornblende as well as fluorite occurred in the Group-Ⅰ granitoids reported previously. Based on the above study of fluorine in accessory minerals and combined with the previous fluorine contents from biotites and

  2. Stability of some La-bearing minerals in metapelites : textural and thermochemical constraints

    Science.gov (United States)

    Janots, E.; Bollinger, L.; Brunet, F.; Grevel, K. D.; Goffé, B.; Bouybaouène, M. L.; Saddiqi, O.

    2003-04-01

    Textural relations between REE-minerals have been studied (by SEM, EMP) in HP-LT metapelites of the Federico unit (Rif, Morocco) as well as in metapelites from Far Western Nepal lesser himalayas. In the Rif samples, the main REE-bearing minerals are monazite, REEPO_4, allanite (10 wt.% REE_2O_3) and synchisite, CaREE(CO_3)_2F. Phase relations between these minerals imply a CO_2-bearing fluid phase for textural and mass balance reasons. In the himalayan samples, allanite (15 wt.% REE_2O_3) crystals are partially or totally replaced by newly formed monazites. Based on U-Th-Pb SIMS data, we believe that newly formed monazites have grown on the retrograde P-T path. Fluid-mineral equilibria seem to dictate the appearance and disappearance of the LREE-minerals in the studied cases. Although thermochemical data are available for some LREE aqueous species, there is a severe lack of thermodynamic properties for LREE-minerals. Along with textural relationships, we will present measured or approximated preliminary thermochemical data (volume, formation enthalpy and third-law entropy) obtained on phases of the La_2O_3-CaO-MgO-Al_2O_3-SiO_2-MgO-P_2O_5-H_2O system. (Mg-La)-allanite and (La)-britholite were synthesized hydrothermally from TEOS gels at 873 K and 150 MPa. High-temperature drop-solution calorimetry was carried out in a Tian-calvet twin calorimeter (Bochum, Germany) at 975 K using lead borate as solvent. Formation enthalpies were retrieved from the dissolution enthalpy (Δ Hdiss) obtained for MgCO_3, Al_2O_3, CaCO_3 et SiO_2. The Δ Hdiss value of La_2O_3 was taken from Bularzik et al., 1991. Third-law entropy data were obtained either from low-temperature adiabatic calorimetry measurements (LCP, Orsay) in the 20-300K range or from approximation methods (oxide summation). Bularzik, J., Navrotsky, A., Dicarlo, J., Bringley, J., Scott, B., and Trail, S. (1991) Energetics of La2-Xsrxcuo4-Y Solid-Solutions (0.0-Less-Than-or- Equal-to-X-Less-Than-or-Equal-to-1.0). Journal

  3. 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.

  4. Geochemical characterization of niobium (Nb) bearing granites in and around Kanigiri, Prakasham district, A.P.: implications for RMRE mineral exploration

    International Nuclear Information System (INIS)

    A number of granite bodies of Mesoproterozoic age occur intermittently over a stretch of about 300 km from Vinukonda (Guntur district) in the north to Sri Kalahasthi (Chittoor district) in the south, proximal to the eastern margin of the Cuddapah basin. Notable among them are the Vinukonda granite, Darsi granite, Podili granite, Kanigiri granite and Anumalakonda granite. Columbite-tantalite, fergusonite, bastnaesite, samarskite, allanite, monazite and thorite are the rare metal and rare earth bearing minerals in the Kanigiri pluton. Based on the geochemical analysis of sixty (60) granite samples by Wavelength Dispersive X-ray Fluorescence Spectrometry (WDXRFS), the samples were grouped into Nb rich and Nb poor varieties. The present study attempts geochemical characterization of Nb-rich and normal granitoids (Nb poor) in and around Kanigiri, Prakasham dist, A.P.

  5. Geochemical and Mineralogical Characterization of Natash Volcanics, South Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    The two ring structures of Western Ghurfa and Gaziret Khashm Natash as well as the ring dyke, G. El Ghurfa have extruded through the volcanic flows. The three rings range in composition from volcanic flows, represented by trachybasalt, trachyandesite, normal trachyte and alkaline trachyte and pyroclastic rocks (agglomerates, tuffs, pumice and scoria). The rings are semicircular to circular in outline range from 1 km to 0.6 km. The high contents of uranium in the studied rocks are due to the presence of secondary uranium minerals such as meta-autunite and kasolite as well as the accessory minerals bearing uranium such as monazite, xenotime, zircon and allanite. The geochemical studies of the volcanic rocks revealed that the rock samples fall in the trachyte, trachyandesite , trachybasalt and basalt fields. These rocks were originated from alkaline magma, and developed in continental basalt environment. The enrichment of the LREEs (182-391 ppm) is most due to the presences of garnet in the source.

  6. Contribution to The Radioactivity, Mineralogy and REES Distribution in the Granitoids of Gebel El Nekeiba, South Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    Gebel El Nekeiba is composed mainly of quartz-syenite surrounding syenogranite. Syenogranite is characterized by the presence of allanite, zircon and fluorite. quartz-syenite is more radioactive and characterized by the presence of violet and deep violet fluorite, zircon and columbite besides thorium minerals (thorite and orangite). The latter were transformed to thorogummite by hydrolysis. The studied rocks are characterized by low Th/U ratio. Quartz syenite and syenogranite rocks show high concentrations of REEs; the former is characterized by higher concentration of HREEs than LREEs. Distribution of REEs in Gebel El Nekeiba is controlled by the elements concentration in the parent magma, and degree of fractionation in the hosting rocks and minerals.

  7. Dating emplacement and evolution of the orogenic magmatism in the internal Western Alps

    DEFF Research Database (Denmark)

    Berger, Alfons; Thomsen, Tonny B.; Ovtcharova, Maria;

    2012-01-01

    Miagliano tonalite. The latter is of special interest, because it is located in the south-eastern side of the Canavese Line, in contrast to most Periadriatic Plutons. The dioritic to tonalitic rocks of the Miagliano Pluton represent an intermediate stage of a calc-alkaline differentiation, demonstrated by...... relics of two different pyroxenes as well as the texture of allanite. Hornblende barometry indicates pressures of similar to 0.46 GPa consistent with the presence of magmatic epidote. Field relationships between the two Plutons, the volcanic and volcaniclastic rocks of the Biella Volcanic Suite and......The Canavese Line in the Western Alps represents the position in the Alpine chain, where alkaline and calc-alkaline magmatism occur in close spatial and temporal association. In addition to available data on the alkaline Valle del Cervo Pluton, we present petrological and geochemical data on the...

  8. 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.

  9. 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).

  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. The Nolans Bore rare-earth element-phosphorus-uranium mineral system: geology, origin and post-depositional modifications

    Science.gov (United States)

    Huston, David L.; Maas, Roland; Cross, Andrew; Hussey, Kelvin J.; Mernagh, Terrence P.; Fraser, Geoff; Champion, David C.

    2016-08-01

    Nolans Bore is a rare-earth element (REE)-U-P fluorapatite vein deposit hosted mostly by the ~1805 Ma Boothby Orthogneiss in the Aileron Province, Northern Territory, Australia. The fluorapatite veins are complex, with two stages: (1) massive to granular fluorapatite with inclusions of REE silicates, phosphates and (fluoro)carbonates, and (2) calcite-allanite with accessory REE-bearing phosphate and (fluoro)carbonate minerals that vein and brecciate the earlier stage. The veins are locally accompanied by narrow skarn-like (garnet-diopside-amphibole) wall rock alteration zones. SHRIMP Th-Pb analyses of allanite yielded an age of 1525 ± 18 Ma, interpreted as the minimum age of mineralisation. The maximum age is provided by a ~1550 Ma SHRIMP U-Pb age for a pegmatite that predates the fluorapatite veins. Other isotopic systems yielded ages from ~1443 to ~345 Ma, implying significant post-depositional isotopic disturbance. Calculation of initial ɛNd and 87Sr/86Sr at 1525 Ma and stable isotope data are consistent with an enriched mantle or lower crust source, although post-depositional disturbance is likely. Processes leading to formation of Nolans Bore began with north-dipping subduction along the south margin of the Aileron Province at 1820-1750 Ma, producing a metasomatised, volatile-rich, lithospheric mantle wedge. About 200 million years later, near the end of the Chewings Orogeny, this reservoir and/or the lower crust sourced alkaline low-degree partial melts which passed into the mid- and upper-crust. Fluids derived from these melts, which may have included phosphatic melts, eventually deposited the Nolans Bore fluorapatite veins due to fluid-rock interaction, cooling, depressurisation and/or fluid mixing. Owing to its size and high concentration of Th (2500 ppm), in situ radiogenic heating caused significant recrystallisation and isotopic resetting. The system finally cooled below 300 °C at ~370 Ma, possibly in response to unroofing during the Alice Springs

  12. The Nolans Bore rare-earth element-phosphorus-uranium mineral system: geology, origin and post-depositional modifications

    Science.gov (United States)

    Huston, David L.; Maas, Roland; Cross, Andrew; Hussey, Kelvin J.; Mernagh, Terrence P.; Fraser, Geoff; Champion, David C.

    2016-01-01

    Nolans Bore is a rare-earth element (REE)-U-P fluorapatite vein deposit hosted mostly by the ~1805 Ma Boothby Orthogneiss in the Aileron Province, Northern Territory, Australia. The fluorapatite veins are complex, with two stages: (1) massive to granular fluorapatite with inclusions of REE silicates, phosphates and (fluoro)carbonates, and (2) calcite-allanite with accessory REE-bearing phosphate and (fluoro)carbonate minerals that vein and brecciate the earlier stage. The veins are locally accompanied by narrow skarn-like (garnet-diopside-amphibole) wall rock alteration zones. SHRIMP Th-Pb analyses of allanite yielded an age of 1525 ± 18 Ma, interpreted as the minimum age of mineralisation. The maximum age is provided by a ~1550 Ma SHRIMP U-Pb age for a pegmatite that predates the fluorapatite veins. Other isotopic systems yielded ages from ~1443 to ~345 Ma, implying significant post-depositional isotopic disturbance. Calculation of initial ɛNd and 87Sr/86Sr at 1525 Ma and stable isotope data are consistent with an enriched mantle or lower crust source, although post-depositional disturbance is likely. Processes leading to formation of Nolans Bore began with north-dipping subduction along the south margin of the Aileron Province at 1820-1750 Ma, producing a metasomatised, volatile-rich, lithospheric mantle wedge. About 200 million years later, near the end of the Chewings Orogeny, this reservoir and/or the lower crust sourced alkaline low-degree partial melts which passed into the mid- and upper-crust. Fluids derived from these melts, which may have included phosphatic melts, eventually deposited the Nolans Bore fluorapatite veins due to fluid-rock interaction, cooling, depressurisation and/or fluid mixing. Owing to its size and high concentration of Th (2500 ppm), in situ radiogenic heating caused significant recrystallisation and isotopic resetting. The system finally cooled below 300 °C at ~370 Ma, possibly in response to unroofing during the Alice Springs

  13. Th-REE- and Nb-Ta-accessory minerals in post-collisional Ediacaran felsic rocks from the Katerina Ring Complex (S. Sinai, Egypt): An assessment for the fractionation of Y/Nb, Th/Nb, La/Nb and Ce/Pb in highly evolved A-type granites

    Science.gov (United States)

    Moreno, J. A.; Molina, J. F.; Bea, F.; Abu Anbar, M.; Montero, P.

    2016-08-01

    The relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios in A-type felsic rocks from the Ediacaran Katerina Ring Complex, northernmost Arabian-Nubian Shield (ANS; S. Sinai, Egypt), are investigated in this work to understand their behavior during generation of highly evolved granitic magmas and to explore the nature of magma sources. Textural and compositional relationships of cognate Th-REE- and Nb-Ta-accessory minerals in Katerina felsic rocks show that chevkinite-group minerals (CGM), monazite, thorite, allanite and xenotime formed from residual liquids in quartz syenite porphyries, quartz monzonites and peralkaline granites, whereas in aluminous granites, allanite and monazite crystallized early, and thorite and columbite formed from residual liquids. Relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios with Zr/Hf ratios in the aluminous granites and with Be abundances in the peralkaline granites suggest a decrease in La/Nb and Ce/Pb ratios in the former, and in Y/Nb and La/Nb ratios in the latter with crystallization progress. This contrasts with absence of systematic variations of Th/Nb and Ce/Pb ratios in the peralkaline compositions and of Y/Nb ratio in the aluminous ones. In this latter, Th/Nb ratio can present a significant decrease only in highly evolved compositions. An analysis of Y/Nb, Th/Nb, La/Nb and Ce/Pb relationships in worldwide OIB and subduction-related magmatic suites reveals that A-type felsic rocks with (Th/Nb)N 1 may have A1-type affinity, and those with (Th/Nb)N > 2, (La/Nb)N > 2, and (Ce/Pb)N fractionation of Th-LREE- and Nb-Ta-accessory minerals and mixing of components derived from the two granite groups may cause deviations from these compositional limits that can be evaluated using constraints imposed by Th/Nb-La/Nb, Ce/Pb-Th/Nb and Ce/Pb-La/Nb relationships in OIB and subduction-related magmatic suites. Three mantle sources might have been involved in the Ediacaran alkaline magmatism from northernmost ANS that are chemically similar

  14. Experimentally determined distribution of fluorine and chlorine upon hydrous slab melting, and implications for F-Cl cycling through subduction zones

    Science.gov (United States)

    Van den Bleeken, Greg; Koga, Kenneth T.

    2015-12-01

    Fluorine and chlorine are volatile elements known to be enriched in primitive arc magmas, and variations of F/Cl ratios can carry information about slab devolatilization processes. Recent experiments on the fractionations of these elements suggest that aqueous fluid has limited capacity to enrich the magma source region in F. Hence, it is difficult to explain observations of primitive arc magmas particularly rich in F. To complement previous experimental studies, we examined the fractionation of fluorine and chlorine during hydrous partial melting of subducting slab. Element-doped phase equilibria experiments were carried out in a complex chemical system at conditions equivalent to potential slab melting temperatures (750-1000 °C) across the amphibolite to eclogite facies transition (1.3-3 GPa). Partition coefficients of F and Cl between hydrous silicic melts and minerals were determined by electron microprobe and/or ion probe. Fluorine is compatible in amphibole (DFamp/glass = 1.18-1.85), and incompatible in garnet (0.034-0.140), clinopyroxene (0.059-0.505), and allanite (0.205-0.504). Hence, amphibole is an important F host, and can retain significant quantities of F in the solid residue of partial melting. On the contrary, Cl is incompatible, with DClmineral/glass generally decreasing from amphibole (0.079-0.625; one outlier at 1.87) to allanite (0.163), clinopyroxene (0.066-0.158), and garnet (0.031-0.153; outlier at 0.492). As a result, Cl is easily mobilized during partial melting. Fluorine and chlorine release during slab melting have been quantified by applying our partition coefficients to a non-modal batch melting model. The model shows that amphibole plays a key role in F/Cl fractionation during partial melting, while F/Cl is close to that of source for the melting of amphibole free eclogite. Moreover, the results from a flux-melting model employing several source compositions are compared to F and Cl abundances in primitive arc magmas. The observed

  15. 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

  16. The recovery of rare earth elements (REE) from beach sands

    International Nuclear Information System (INIS)

    This preliminary study describes a metallurgical process that will extract, recover and produce REE oxides from beach sands obtained from Ombo, San Vicente, northern Palawan. The beach sands contain REE minerals of allanite and small amounts of monazite. Allanite is a sorosilicate mineral containing rare earths, thorium and uranium. Monazite is the anhydrous phosphate of cerium and the lanthanum group of rare earths with thorium commonly present in replacement for cerium and lanthanum. Collected beach sand were first pan-concentrated in-situ to produce heavy mineral concentrates. Screening using a 32 mesh (0.500 mm) sieve was done at the Nuclear Materials Research Laboratory to remove oversize sand particles. The -32 mesh fraction was treated with bromoform (sp. gr. 2.89) to separate the heavy minerals from siliceous gangue. Grinding to -325 mesh size (0.044mm) followed to liberate the minerals prior to leaching. Two acids leachants were used - concentrated HCl for the first trial and a mixture of concentrated HCl and HNO3 (10:1 volume ratio) for the second trial. Both leaching trials were carried out at 180oC for 7 hours or until dry. The resulting leached residues were re-dissolved in concentrated HCl and filtered. IonquestR 801, an organophosphorous extractant, was added to the filtrate to separate the radioactive thorium from REE. Sodium hydroxide was added to the aqueous phase to precipitate the REE. After filtering the precipitate, it was dissolved in HCl. The acid solution was repeatedly extracted three (3) times with IonquestR 801 to remove iron and other contaminants. Ammonium hydroxide was added to the final solution to precipitate the REE, which was then dried in the oven. The precipitate was calcined/roasted in the furnace at two different temperatures for different periods of time to burn off the organic matter and to form oxides. Results of the XRD analysis showed peaks of the calcined precipitate matching with the peaks of lanthanum oxide standard

  17. Partitioning of actinides, rare earth elements, and other trace elements in titanium-rich veins from Adamello, Italy

    International Nuclear Information System (INIS)

    Extensive mineralogical and chemical studies have been carried out on the Ti-rich hydrothermal veins emplaced within the contact aureole of the Adamello batholith. In addition to other actinide and rare earth element host phases, the veins contain both zirconolite and betafite and provide information relevant to ceramic wasteforms designed for the disposal of actinide-rich nuclear wastes. In this paper, we describe the results of element partitioning studies based on dissolution experiments using 9M HCl. Generally, the acid-resistant minerals include allanite, baddeleyite, betafite, chalcopyrite, geikielite, titanite, spinel, and zirconolite. We also found that the major silicate minerals forsterite, phlogopite, and titanian clinohumite and the sulfide mineral pyrrhotite are partially dissolved by the acid treatment, whereas calcite and apatite are highly soluble (as expected). In particular, the distributions of Th and U between the acid-resistant and acid-soluble fractions indicate that they partition mainly between zirconolite, titanite, betafite, and apatite. However, there is a considerable increase in the amounts of Zr, Nb, Th, and U released in certain actinide-rich samples that may result from enhanced dissolution following radiation damage. Copyright (2001) Material Research Society

  18. Complete Alpine reworking of the northern Menderes Massif, western Turkey

    Science.gov (United States)

    Cenki-Tok, B.; Expert, M.; Işık, V.; Candan, O.; Monié, P.; Bruguier, O.

    2016-07-01

    This study focuses on the petrology, geochronology and thermochronology of metamorphic rocks within the northern Menderes Massif in western Turkey. Metasediments belonging to the cover series of the Massif record pervasive amphibolite-facies metamorphism culminating at ca. 625-670 °C and 7-9 kbars. U-Th-Pb in situ ages on monazite and allanite from these metapelites record crustal thickening and nappe stacking associated with the internal imbrication of the Anatolide-Taurides platform during the Eocene. In addition, new 39Ar/40Ar single muscovite grain analyses on deformed rocks were performed in three localities within the northern Menderes Massif and ages range from 19.8 to 25.5 Ma. These mylonites may be related to both well-known detachments, Simav to the north and Alaşehir to the south, which accommodate Oligo-Miocene exhumation of the Menderes core complex. U-Th-Pb data on monazite grains (22.2 ± 0.2 Ma) from migmatites emplaced within the Simav detachment confirm these ages.

  19. Geology, Geochemistry and Radioactivity of Gabal Hamrat Al Jirjab area, Esh El Melaha range, North Eastern Desert, Egypt

    International Nuclear Information System (INIS)

    Gabal Hamrat Al Jirjab area is located in the northern part of Esh El Melaha range, north Eastern Desert. The area is covered mainly by Dokhan volcanic rocks (andesite, dacite and their pyroclastics) intruded by alkali feldspar granites of G. Hamrat A1 Jiijab with some dyke swarms of various composition, felsic dykes (granophyres and rhyolite), intermediate dykes (andesite) and basic dykes (dolerite). The studied Dokhan volcanics are considered as medium-K rocks originated from calc-alkaline magma in island arc to active continental margin environment. On the other hand, the studied granites are classified as alkali feldspar granites and considered as I-type, originated from peraluminous calc-alkaline highly fractionated magma. They are post-orogenic and formed under an extensional regime suggesting crystallization during relaxation stage that following collision. They-are intruded in a crust of thickness> 30 Km and crystallized at temperature < 800°C. Alkali feldspar granites of G. Hamrat A1 Jiijab can be described as uraniferous granite. The average values (16 ppm eU and 32 ppm eTh) are attributed to the presence of U and Th bearing accessory minerals namely; thorite, uranothorite, monazite, zircon, fluorite and allanite. Stream sediments of G. Hamrat A1 Jiijab area exhibit mixture of detritus components, represented by pebble, granules, sand and sizes less than very coarse silt. These sediments are considered the natural trap for the accessory and some radioactive minerals for the surrounding country rocks.

  20. Behaviour of rare-earth elements in highly evolved granitic systems: Evidence from Proterozoic molybdenite mineralized aplites and associated granites in northern Sweden

    Science.gov (United States)

    Öhlander, Björn; Billström, Kjell; Hålenius, Elke

    1989-10-01

    Field relations, mineralogy, major- and trace-element contents (including REE analyses of whole-rock samples and minerals) of three Proterozoic granites and their associated molybdenite mineralized aplites have been studied at Allebuoda, Munka and Kåtaberget in northern Sweden. The granites crystallized from melts that were not saturated with water. The mineralized potassic aplites formed by quenching of residual melts caused by sudden pressure drop, H 2O saturation and vapour escape during tectonic rupturing. Leucogranites with higher {Na 2O }/{K 2O } ratios from Allebuoda and Munka crystallized during H 2O-saturated equilibrium conditions in which the exsolved vapour could continuously migrate away. The pressure was probably ˜ 3 kbar at Munka, and somewhat lower at Allebuoda. The granites have REE patterns characterized by LREE enrichments and negative Eu anomalies. In comparison, the potassic aplites and the more sodic leucogranites are depleted in LREE, enriched in HREE and have larger negative Eu anomalies. Allanite and monazite are the most important REE carriers in the granites. These minerals are strongly enriched in LREE, whereas fluorite and xenotime, which are more abundant in the aplites, are most enriched in HREE. Due to the strong control of accessory minerals on the REE balance, REE are of limited use in petrogenetic modelling of highly evolved granitic systems.

  1. Alochtónne jemnozrnné sedimenty a ich vztah ku genéze Liskovskej jaskyne (Chočské podhorie, severné Slovensko

    Directory of Open Access Journals (Sweden)

    Katarína Bónová

    2014-12-01

    Full Text Available A combination of sedimentological and mineralogical methods with emphasis on heavy mineral assemblage research applied to allochthonous sediments in the Liskovská Cave located in the western part of the Liptovská Basin (in the tectonic horst composed of Triassic limestones at foothills of the Chocské vrchy Mts. were used for the identification their provenance and sedimentary history. Allochthonous fine-grained mud was studied in three profiles (LI-1 to LI-3. The sediments originated from the suspension in slow water flow to stagnant water (slackwater facies. This material could be later redeposited during the younger flooding event and small-scale slumps and gravity flows (mudflows have been locally generated on steeper cave floors. Based on mineralogical study the cave sediments are composed of quartz, muscovite, calcite, chlorite, K-feldspar, plagioclase and dolomite. A heavy mineral assemblage is formed by garnet, zircon, apatite, monazite, tourmaline, staurolite, amphibole, rutile, titanite, epidote, sillimanite, allanite, andalusite, pyroxene and xenotime. Opaque minerals are represented by ilmenite, pyrite, magnetite, Cr-spinel, hematite, Cu-sulfides and Feoxyhydroxides. Their mineralogical character indicates the heterogenous source material which was transported by the Váh River. The results are significant for a more accurate reconstruction of origin and development of the cave, mainly its sedimentary phases in Middle and Late Pleistocene related to floods from the adjacent river bed.

  2. Fluid inclusion study of radioactive granite and cherty cataclasite in the Southeastern part of Nanded district, Maharashtra: implications for the uranium mineralisation

    International Nuclear Information System (INIS)

    Southeastern part of Nanded district, Maharashtra exposes Palaeoproterozoic granitoids, representing the younger phase of Peninsular Gneissic Complex (PGC), mark the northeastern extension of Eastern Dharwar Craton. These granitoids are predominantly pink/grey granites, which are traversed by younger phosphatic cherty cataclasites close to the Deccan Trap capping. They are also affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations, especially close to fault/shear zones. A number of N-S to NNE-SSW, NE-SW, NW-SE and E-W trending lineaments marked by faults/fractures/shear zones and dykes are delineated in this granitic terrain. Among these, NE-SW and NNE-SSW faults/shear zones affecting granitoids and cherty cataclasites in Shahpur-Sujayatpur and Thadisaoli area have recorded significant uranium anomalies (Granitoids: upto 1% U3O8 and 0.20% ThO2; Cherty cataclasites upto 0.11% U3O8 and <0.005% ThO2) and enrichment in rare metal and rare earth element content (Nb-77ppm, Y-111 ppm, Zr-432ppm; n=9 and total REE-1167ppm; n=3). Presence of discrete uranium/thorium minerals (uraninite, b-uranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite are responsible for radioactivity in granitoids while phosphatic material accounts for radioactivity in cherty cataclasites

  3. Heavy mineral distribution in stream sediment of Tapah area, Perak, Malaysia

    Science.gov (United States)

    Sibon, Mahat Hj; Jamil, Habibah; Umor, Mohd Rozi; Hassan, Wan Fuad Wan

    2013-11-01

    This paper aims to provide the overview of occurrence, distribution and origin of the heavy minerals in the study area. A total of 45 selected stream sediment heavy mineral concentrate samples were panned using standard dulangs, dried and separated from other light minerals using bromoform. The heavy minerals were separated into different fractions at different amperes using Frantz Isodynamic magnetic separator. Mineral identification was done using binocular microscope augmented by X-ray diffraction analyses. Mineral abundance data were analysed graphically using triangular diagrams to show their origin. Dominant minerals present in the heavy mineral samples collected are ilmenite, cassiterite, tourmaline, zircon, topaz, and magnetite. The less common minerals, present in trace amounts are hematite, xenotime, allanite, monazite, rutile, anatase, leucoxene, chromite, garnet and olivine. Examination of the heavy mineral assemblage shows that they originated from granite batholiths of the Main Range, Changkat Rembian as well as from the metasedimentary rock in the area. The gold flakes present are found together with cassiterite and topaz indicating that gold originates from the mineralized veins contact-metamorphosed metasedimentary rocks. Almost all samples collected contain cassiterite grains in various amounts. From the mineral assemblage, the source of cassiterite originates from the mineralized quartz veins that cut granitic rocks of Main Range, Changkat Rembian as well as the metasedimentary rock in the area. Greisenized veins containing quartz, mica and tourmaline with the presence of wolframite and arsenopyrite also contribute to the presence of cassiterite in this study area.

  4. Trace and major elements in geological samples from Itingusssu River Basin, Sepetiba Bay - Rio de Janeiro

    International Nuclear Information System (INIS)

    The Itingussu drainage basin is situated at 22 deg 44' - 22 deg 55' SL and 44 deg 53' - 43 deg 55' WL, in Coroa-Grande district, Sepetiba Bay, southwest of Rio de Janeiro, Brazil. Its total area is less than 10 km2 and includes a waterfall with three drop offs. The study area is located in a granitic pre-Cambrian embasement, discharging in a mangrove forest fringe. This work attempts to investigate the influence of lithology types in the elemental composition of soil of region and sediments of related mangrove. Instrumental neutron activation analysis and subsequent gamma-ray spectrometry were used. This technique enabled the measurement of at least twenty-one chemical elements. The more representative soil samples were enriched with U and Th. Multivariate Statistical Analysis showed that the soil and sediments formed in this area have been influenced by the leucocratic rocks, enriched with LREE and Th. The factorial analysis enables the identification of five factors of influence in the ordination of elements: presence of iron minerals (biotite); presence of allanite; marine influence in the sediment; differentiated kinetic of transport and diagenesis. (author)

  5. Large partition coefficients for trace elements in high-silica rhyolites

    Energy Technology Data Exchange (ETDEWEB)

    Mahood, G. (Stanford Univ., CA); Hildreth, W.

    1983-01-01

    The partitioning of 25 trace elements between high-silica rhyolitic glass and unzoned phenocrysts of potassic and sodic sanidine, biotite, augite, ferrohedenbergite, hypersthene, fayalite, titanomagnetic, ilmenite, zircon, and allanite has been determined by INAA on suites of samples from the mildly peralkaline lavas and tuff of the Sierra La Primavea, Mexico, and the metaluminous, compositionally zoned, Bishop Tuff, California. The partition coefficients are much larger than published values for less silicic compositions; the range of values among Primavera samples that differ only slightly in temperature or bulk composition approaches that previously reported from basalts to rhyodacites. Intrinsic temperature dependence of the crystal/liquid partitioning is apparently small. The high values of partition coefficients reflect principally the strongly polymerized nature of the alkali-aluminosilicate liquid, whereas the marked variability of values for partition coefficients is attributed to differences in the concentration of complexing ligands and/or different degrees of melt polymerization. Great variation in the values of partition coefficients that are potentially applicable to early stages in the partial melting of crustal rocks complicates assessment of (1) source regions for granitic melts and (2) contributions by crustal-melt increments to andesites.

  6. Natural radionuclides content and radiological hazard of commercial ornamental stones: An integrated radiometric and mineralogical-petrographic study

    International Nuclear Information System (INIS)

    Twenty samples of natural building materials commonly employed as ornamental stones in the international market have been investigated for natural radioactivity. External (gamma), as defined and used by the European Commission, and internal (alpha) hazard indexes were calculated and radon specific exhalation rate and emanation fraction were measured. The radiological investigation was complemented by an integrated mineralogical-petrographic and rock characterization approach. The most common radioactive accessory minerals occurring in the investigated samples are apatite, zircon and allanite, with minor monazite, thorite, thorianite, REE and Zr-oxides. Significant correlations with total activity concentration have been observed for K2O, Th and Ce concentrations. The emanation fraction is also influenced by both total porosity and porosity distribution. Radon exhalation rate and emanation fraction are very variable ranging from 0.0011 to 0.64 Bq kg-1 h-1 and from 0.2 to 62%, respectively. Most of the materials have radiological hazard indexes that do not exceed the European Commission limit values when used as ornamental or paving or flooring stones. However, three volcanic (Tufo Giallo Riano, Tufo Grigio Riano and Peperino Viterbese) samples could cause significant exposure both from excess radon indoor concentration (>200 Bq m3) and from gamma radiation (>1 mSv y-1) when used as structural materials. This study further indicates that limit values for hazard indexes based on natural activity concentration and Rn emanation should take into account the lithological properties and use of the materials.

  7. Presence of radioactive minerals in ornamental granitic rocks

    International Nuclear Information System (INIS)

    In this work, we report on results of studies to determine the presence of radioactive minerals in ornamental granitic rocks used as revestiment, originated from several quarries in Brazil, predominantly those from the states of Espirito Santo and Minas Gerais. To develop this work, one hundred samples were collected from commercial stones in Belo Horizonte. In the study of the radioactive materials, techniques of autoradiography were used, as well as optical microscopy, diffractometry and chemical analysis (X-ray spectrometry, X-ray fluorescence, neutronic activation, gravimetry and electron microanalysis) to determine the associated minerals and litotypes. Results obtained with autoradiographs of several samples show the shape, size and intensity of irregularly distributed dark spots which, when checked through an optical microscope and an electron microprobe, highlight mainly monazite, allanite and zircon. By using chemical analysis, concentrations of up to 30 ppm of uranium and 130 ppm of thorium were found, preferably associated to high concentrations of light rare earths in silicate rocks of granitic composition. In the future, further results about the ornamental granitic rocks with radioactive minerals will be applied, where possible implications to the environment and damages to the health due to contact with these rocks will be discussed. (author)

  8. RADIOACTIVITY DOSAGE OF ORNAMENTAL GRANITIC ROCKS BASED ON CHEMICAL, MINERALOGICAL AND LITHOLOGICAL DATA

    Energy Technology Data Exchange (ETDEWEB)

    Salas, H.T.; Nalini, H.A. Jr.; Mendes, J.C.

    2004-10-03

    One hundred samples of granitic rock were collected from granite traders in Belo Horizonte. Autoradiography, optical microscopy, diffractometry, and chemical analysis (X-ray spectrometry, X-ray fluorescence, neutron activation, gravimetry and electron probe microanalysis) were used to determine the mineral assemblages and lithotypes. Autoradiographic results for several samples showed the presence of monazite, allanite and zircon. Chemical analysis revealed concentrations of uranium of {le} 30ppm, and thorium {le} 130ppm. Higher concentrations generally correlated with high concentrations of light rare earths in silica-rich rocks of granitic composition. Calculations were made of radioactive doses for floor tiles in a standard room for samples with total concentration of uranium and thorium greater than 60ppm. On the basis of calculations of {sup 232}Th, {sup 40}K and {sup 226}Ra from Th, K and U analysis, the doses calculated were between 0.11 and 0.34 mSv/year, which are much lower than the acceptable international exposure standard of 1.0 mSv/year.

  9. Presence of radioactive minerals in ornamental granitic rocks; Ocorrencia de minerais radioativos em rochas graniticas ornamentais

    Energy Technology Data Exchange (ETDEWEB)

    Salas, Humberto Terrazas [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil)]. E-mail: salasht@cdtn.br; Nalini Junior, Herminio Arias; Mendes, Julio Cesar [Ouro Preto Univ., MG (Brazil). Escola de Minas. Dept. de Geologia

    2002-07-01

    In this work, we report on results of studies to determine the presence of radioactive minerals in ornamental granitic rocks used as revestiment, originated from several quarries in Brazil, predominantly those from the states of Espirito Santo and Minas Gerais. To develop this work, one hundred samples were collected from commercial stones in Belo Horizonte. In the study of the radioactive materials, techniques of autoradiography were used, as well as optical microscopy, diffractometry and chemical analysis (X-ray spectrometry, X-ray fluorescence, neutronic activation, gravimetry and electron microanalysis) to determine the associated minerals and litotypes. Results obtained with autoradiographs of several samples show the shape, size and intensity of irregularly distributed dark spots which, when checked through an optical microscope and an electron microprobe, highlight mainly monazite, allanite and zircon. By using chemical analysis, concentrations of up to 30 ppm of uranium and 130 ppm of thorium were found, preferably associated to high concentrations of light rare earths in silicate rocks of granitic composition. In the future, further results about the ornamental granitic rocks with radioactive minerals will be applied, where possible implications to the environment and damages to the health due to contact with these rocks will be discussed. (author)

  10. Radioactivity dosage evaluation of Brazilian ornamental granitic rocks based on chemical data, with mineralogical and lithological characterization

    Science.gov (United States)

    Salas, Humberto Terrazas; Nalini, Hermínio Arias; Mendes, Júlio César

    2006-02-01

    One hundred samples of granitic rock were collected from granite traders in Belo Horizonte. Autoradiography, optical microscopy, diffractometry, and chemical analysis (X-ray spectrometry, X-ray fluorescence, neutron activation, gravimetry, and electron probe microanalysis) were used to determine the mineral assemblages and lithotypes. Autoradiographic results for several samples showed the presence of monazite, allanite, and zircon. Chemical analysis revealed uranium concentrations ≤30 ppm and thorium ≤130 ppm. Higher concentrations generally correlated with high concentrations of light rare earths in silica-rich rocks of granitic composition. Calculations were made of radioactive doses for samples, of floor tiles in a standard room, with total concentration of uranium and thorium greater than 60 ppm. On the basis of calculations of 232 Th, 40 K, and 226 Ra from analysis of Th, K, and U, the doses calculated were between 0.11 and 0.34 mSv/year, which are much lower than the acceptable international exposure standard of 1.0 mSv/year.

  11. Petrography and geochemistry of granites with reference to their potentiality for RMRE mineralisation, Dirsavancha-Kammavaripalle, Prakasam district, Andhra Pradesh

    International Nuclear Information System (INIS)

    Proximal to the eastern margin of the Cuddapah Basin, number of granite bodies of Meso-Proterozoic age occur intermittently over a stretch of about 300 km from Vinukonda in the north to Sri Kalahasthi in the south, The granitic plutons of Dirsavancha-Kammavaripalle located NW of Kanigiri are petrographically characterised as alkali feldspar granite with accessory biotite, sphene, zircon, apatite, allanite and fluorite. Magnetite, ilmenite, galena, rutile, hematite, pyrite, molybdinite, goethite, limonite and gold are the opaque minerals observed. Radioactivity is attributed to U-bearing columbite-tantalite and labile uranium. The granites are per alkaline to meta aluminous, within-plate granites with high content of REE and the chondrite normalised pattern shows negative europium anomaly. The incompatible element enriched granite with the presence of elements like Nb, Ta, Zr, U Tb and high Rh, LREE indicates low degree partial melting of rocks from lower to middle crustal depths. The enrichment of Large Ion Lithopile Elements indicates fertile nature of these granites and are potential hosts of RMRE minerals. (author)

  12. Enrichment of trace elements in garnet amphibolites from a paleo-subduction zone: Catalina schist, southern California

    Energy Technology Data Exchange (ETDEWEB)

    Sorensen, S.S. (Smithsonian Institution, Washington, DC (USA)); Grossman, J.N. (Geological Survey, Reston, VA (USA))

    1989-12-01

    The abundance, P-T stability, solubility, and element-partitioning behaviour of minerals such as rutile, garnet, sphene, apatite, zircon, zoisite, and allanite are critical variables in models for mass transfer from the slab to the mantle wedge in deep regions of subduction zones. The influence of these minerals on the composition of subduction-related magmas has been inferred (and disputed) from inverse modelling of the geochemistry of island-arc basalt, or by experiment. Although direct samples of the dehydration + partial-melting region of a mature subduction zone have not been reported from subduction complexes, garnet amphibolites from melanges of circumpacific and Caribbean blueschist terranes reflect high T (>600{degree}C) conditions in shallower regions. Such rocks record geochemical processes that affected deep-seated, high-T portions of paleo-subduction zones. In the Catalina Schist, a subduction-zone metamorphic terrane of southern California, metasomatized and migmatitic garnet amphibolites occur as blocks in a matrix of meta-ultramafic rocks. This mafic and ultramafic complex may represent either slab-derived material accreted to the mantle wedge of a nascent subduction zone or a portion of a shear zone closely related to the slab-mantle wedge contact, or both. The trace-element geochemistry of the complex and the distribution of trace element among the minerals of garnet amphibolites were studied by INAA, XRF, electron microprobe, and SEM.

  13. Uraniferous pegmatites of the Sharlot Lake area, Ontario

    International Nuclear Information System (INIS)

    Reconnaissance airborne gamma ray spectrometric data covering the southern Grenville Province clearly indicate four anomalous zones, namely Mont Laurier and Huddersfield Township in western Quebec, and the Bancroft and Sharbot Lake areas in eastern Ontario. These surveys show that the Sharbot Lake area has a distinctly higher average eU/eTh ratio compared to the other Grenville pegmatite districts. Detailed surveys in the Sharbot Lake area have been particularly useful in providing a comprehensive picture of the pegmatite distribution. The majority of the pegmatites occur as conformable to semiconformable sill-like bodies ranging from bands less than 1 metre wide to bodies exceeding 500 by 50 metres. They are generally white to pale pink, massive to locally foliated and coarse grained. The principal radioactive mineral is uraninite commonly associated with biotite. Other radioactive phases include allanite, monazite, thorite, uranothorite, zircon and apatite. Average equivalent uranium concentrations measured by in situ gamma ray spectrometry range from a low of 3 ppm (averaging 36 ppm eTh) for pegmatites hosted by pink leucogranite gneiss to amphibolite-hosted pegmatite with an averge of 41 ppm (averaging 24 ppm eTh). Locally, equivalent uranium concentrations exceeding 5000 ppm may be found. Field evidence suggests that the pegmatites may have been developed by partial melting of Grenville Supergroup paragneisses. In places the pegmatites show evidence of mobilization and emplacement into adjacent granite gneisses and metasediments

  14. Geochemistry of U-Th- REE bearing minerals, in radioactive pegmatite in Um Swassi-Dara area, north eastern desert, Egypt

    International Nuclear Information System (INIS)

    Some of the pegmatites in the north Eastern Desert of Egypt have high radioactive values, between them the studied radioactive pegmatites which are clustered just in the western margin of Um Swassi-Dara hosted monzogranites. In zoned pegmatite the alteration zones locate between quartz core and intermediate zone are characterizing with the abundance of rare-earth minerals, anderbergite, cenosite, Y-allanite and uranium, thorium minerals such as euxenite, ferro-columbite and complex titanium-yetrum oxides (Kobbite). This zone is a result of many alteration processes developed from volatile-rich magmatic fluids and/or hydrothermal solution which evolved from late differentiated magmatic fluid and lead to increase of U, Th, Zr, Nb, Ti and REE bearing minerals. Such a distinctive alkaline mineralization suite, possibly related to an alkali fluid phase, is superimposed on a more normal, less alkaline group of minerals such as cassiterite, chalcopyrite, and galena. Nb-Ta-Ti minerals bearing U and Th, define a sequence of oxide, cyclosilicate and silicate minerals, showing the effect of hydrothermal overprinting with extreme REE enrichment of the fluids. It can be concluded that the studied mineralization took place in three overlapping stages

  15. 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).

  16. 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)

  17. Quaternary evolution of the rivers of northeast Hainan Island, China: Tracking the history of avulsion from mineralogy and geochemistry of river and delta sands

    Science.gov (United States)

    Pe-Piper, Georgia; Piper, David J. W.; Wang, Ying; Zhang, Yongzhan; Trottier, Corwin; Ge, Chendong; Yin, Yong

    2016-03-01

    The mineralogy and geochemistry of sands were investigated in the Nandu and Wanquan rivers, Hainan Island, China, to determine the history of avulsion in the lower reaches of the Nandu River. The study also provided the opportunity to assess the utility of geochemical analysis of sands as a provenance tool. Much of the heavy mineral fraction in the rivers consists of subangular Fe-Ti oxide and Fe-(hydr)oxide minerals, and less stable minerals such as amphibole, epidote, and andalusite, whereas rounded resistant ilmenite, rutile, tourmaline and zircon predominate on the deltaic coast. Mineral assemblage and chemical composition of individual samples are related to specific source areas and river tributaries. The results demonstrate northwestwards flow of the Nandu River during the mid-Holocene and earlier avulsion of the river to the northeast coast, probably during a Late Pleistocene marine highstand. Minor basement tilting, producing little relief, was sufficient to divert the lower reaches of rivers, and this effect was enhanced where basalt flows dammed former river courses. Bulk sample REE geochemistry is largely controlled by the relative abundance of monazite, allanite, titanite, zircon and epidote, derived principally from granites. Detrital geochemistry alone shows too much variability to interpret provenance. However, a smaller number of heavy mineral analyses provide an understanding of the mineralogical origins of geochemical variation, thus enabling interpretations of provenance.

  18. Semi-detailed geochemical exploration for rare earths in San Vicente-Roxas, Northern Palawan

    International Nuclear Information System (INIS)

    A semi-detailed geochemical survey for rare earths was undertaken in San Vicente and Roxas, Palawan as a follow-up survey of the reconnaissance exploration previously conducted in Northern Palawan. The area covered was about 300 sq. km.. The survey included the collection of panned heavy mineral concentrate and stream sediment samples along streams and rivers. Soil from the stream bank and rocks were also taken as needed. The sampling density was 2-3 samples per sq. km. Mineralogical analysis was done on a total of 756 heavy minerals samples. Selected samples were analyzed for rare earth elements (REE) using x-ray fluorescence and instrumental neutron activation analysis. Other samples were analyzed for associated elements using atomic absorption spectrometry and fluorimetry for uranium. Gamma-ray spectrometry was used on selected panned concentrates for thorium and uranium. Results of the survey indicated at least 2 significant geomineralogical anomalies each in San Vicente and Roxas area. These anomalies delineate the possible extent of rare earth mineralization for possible more detailed surveys. Mineralogical analysis of the heavy minerals revealed that allanite is the principal REE mineral with minor associated igneous monazite present in San Vicente. In Roxas, nodular gray monazite is the only REE mineral present. The occurrence of gold particles and nodular monazite could make the prospect quite attractive for further studies. (Author)

  19. High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims

    Science.gov (United States)

    Vazquez, Jorge A.; Lidzbarski, Marsha I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

  20. Sr and Nd isotopic signature of the high-K calc-alkaline magmatism of the central Ribeira belt: the Sao Pedro Granite in Lumiar, RJ

    International Nuclear Information System (INIS)

    In the central-northern Ribeira belt there are many granitic to granodioritic bodies showing varied shape and size, characterizing a late- to post-collisional Ca-alkaline, cordilleran I-type province. The Sao Pedro Granite occurs in the mountain region of Rio de Janeiro State as small post-collisional bodies. It presents isotropic fabric, equigranular to seriate inequigranular texture, as well as local concentration of allanite, which gives discrete composition and texture variation to the rock. The granite has a high-K calcalkaline to alkali-calcic character and weakly peraluminous nature. Despite its short geochemical variation, high Ba, Zr and Th contents besides low concentrations of MgO and CaO are noticeable. High REE contents are associated with fractionated REE patterns showing strong negative Eu anomalies. A crustal origin for the granite can be assumed by its very negative and positive .Nd and .Sr values, respectively, as well as by 87Sr/86Sr initial ratios ranging from 0,718 to 0,740. TDM ages point to paleoproterozoic source, which agrees with geological time of intensive crust generation. (author)

  1. Sm/Nd isotopic data for the Santana do Ipanema high-K mega dykes as evidence for Brasiliano decompression melting at the Pernambuco-Alagoas (PE-AL) Massif, Borborema province

    International Nuclear Information System (INIS)

    This work deals with the Sm-Nd signatures of some mega dykes located close to the Northern limit of the batholith in the Santana do Ipanema plutonic complex (SIC), which comprises 6 intrusive suites. Their composition ranges from syenites to quartz syenites. They are mesocratic to leucocratic, usually equigranular but sometimes porphyritic. Their accessory mineralogy is comprised of sphene, opaque, amphibole, ± pyroxene, apatite, zircon, biotite, allanite and epidote. The main minerals are microcline, plagioclase and quartz. The SIC rocks are metaluminous and intermediate to acid, with Si O2 ranging from 55,6 wt% to 66.4 wt% and Ba ranging from 3889 ppm to 10253 pp,. The K2 O/Na2 O ratio ranges widely as well, from 0,59 to 2.07, making these rocks a quite heterogeneous suite. The diagram shows two patterns, one with troughs at Nb, Zr and Ti, while the other one shows troughs at Nb, Hf and Eu. The Zr data available show a wide range, from 133 ppm to 314 ppm, suggesting this suite was the result of different degrees of partial melting of a same enriched LIL protolith. Five isotope Sm-Nd data has been obtained for these rocks, yielding epsilon Nd (0.60 Ga) values which ranges from -9.3 to -3.6, and Tdm which ranges from 2.34 Ga to 1.26 Ga. The isotope data agree with the heterogeneous character showed by the trace elements

  2. Sr and Nd isotopic signature of the high-K calc-alkaline magmatism of the central Ribeira belt: the Sao Pedro Granite in Lumiar, RJ; Assinatura isotopica de Sr e Nd do magmatismo calcio-alcalino de alto-K na Faixa Ribeira central: o exemplo do Granito Sao Pedro em Lumiar, RJ

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Julio Cezar; Medeiros, Silvia Regina de; Chaves, Eduardo Amorim, E-mail: julio@geologia.ufrj.br, E-mail: silvia@geologia.ufrj.br, E-mail: edupc2@yahoo.com.br [Departamento de Geologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ) (Brazil)

    2011-09-15

    In the central-northern Ribeira belt there are many granitic to granodioritic bodies showing varied shape and size, characterizing a late- to post-collisional Ca-alkaline, cordilleran I-type province. The Sao Pedro Granite occurs in the mountain region of Rio de Janeiro State as small post-collisional bodies. It presents isotropic fabric, equigranular to seriate inequigranular texture, as well as local concentration of allanite, which gives discrete composition and texture variation to the rock. The granite has a high-K calcalkaline to alkali-calcic character and weakly peraluminous nature. Despite its short geochemical variation, high Ba, Zr and Th contents besides low concentrations of MgO and CaO are noticeable. High REE contents are associated with fractionated REE patterns showing strong negative Eu anomalies. A crustal origin for the granite can be assumed by its very negative and positive .Nd and .Sr values, respectively, as well as by 87Sr/86Sr initial ratios ranging from 0,718 to 0,740. TDM ages point to paleoproterozoic source, which agrees with geological time of intensive crust generation. (author)

  3. 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.

  4. The U resources inventory at Tebalungkang sector, west Kalimantan systematic prospection stage

    International Nuclear Information System (INIS)

    The systematic prospection at Tebalungkang sector, West Kalimantan was carried out to characterize the occurrence of U mineralization and to invent the potential U resources at the area. The investigation was done on the basis of previous results, i.e. radiometric anomalous outcrops and boulders of 1000-7000 C/s. The methods for the investigation was systematic geological mapping and radiometric measurements of soil and tranced rocks and supported by mineralogical and geochemical analyses. The results of the investigation show that this area consists of metamorphic rocks, intruded by granite quartz-diorite batholites and dike of andesite and lamprophyre. From geological structure this is 30o plunging from anticlin NE-SW and NNW-SSE, is crossed by NE-SW and E-W normal faults and NW-SE and WNW-ESE strike slip faults. Uranium mineralization appears in quartz-schist brecciated and quachitite (lamprophyre). The radioactive minerals were thorite and monazite, associated with rutile, ilmenite, magnetite, hematite, pyrite, calcopyrite, muscovite, apatite and allanite. The U content from rock samples has been found to be 4,5-54,75 ppm U

  5. 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.

  6. Application of Scanning Electron Microscopy/Energy-Dispersive X-Ray Spectroscopy for Characterization of Detrital Minerals in Karst Cave Speleothems.

    Science.gov (United States)

    Zupančič, Nina; Miler, Miloš; Šebela, Stanka; Jarc, Simona

    2016-02-01

    Micro-scale observations in karst caves help to identify different processes that shaped local morphology. Scanning electron microscopy/energy-dispersive X-ray spectroscopy inspection of speleothems from two karst caves in Slovenia, Predjama and Črna Jama, confirmed the presence of sub-angular to sub-rounded detrital fragments of clay minerals, feldspars, quartz, Fe-oxides/hydroxides, rutile and Nb-rutile, xenotime, kassite, allanite, fluorapatite, epidote, ilmenite, monazite, sphene, and zircon, between 2 and 50 μm across. These occur in porous layers separating calcite laminae in the clayey coating on the layer below the surface of the speleothems, and are also incorporated within actual crystals. It is likely that they are derived from the weathered rocks of the Eocene flysch. Probably they were first transported into the caves by floodwaters forming cave sediments. Later, depending upon the climate conditions, they were moved by air currents or by water to the surface of active speleothems. They might also be redeposited from overlying soils enriched with wind-transported minerals from the flysch, or from higher passages filled with weathered flysch sediment, by drip water percolating through the fissured limestone. As some of the identified minerals are carriers of rare earth elements, Ti and Zr, their presence could affect any palaeoclimatic interpretations that are based upon the geochemical composition of the speleothems. PMID:26914996

  7. Mineralogy and geochemistry of the Late Neoproterozoic rare metal granitoids of Gabal El-Ineigi pluton, Northern Arabian-Nubian Shield, Egypt

    Science.gov (United States)

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

    2016-04-01

    Gabal El-Ineigi granitoid pluton is situated in the Central Eastern Desert of Egypt and is considered as one of the good examples of the fluorite bearing rare metal granites in the Arabian Nubian Shield (ANS). It constitutes a multiphase pluton consists of porphyritic syenogranites (SG) and coarse to medium grained highly evolved alkali-feldspar granites (AFG) intruded into the older granodiorites and metagabbro-diorite rocks. Petrographic features indicate that quartz, K-feldspar (perthite, Or97‑99), plagioclase (albite, An0‑6) and biotite are the major mineral phases of both granitic types with subordinate muscovite that is observed only in the AFG. Columbite, rutile, fluorite, zircon and thorite are the significant accessory minerals in the AFG while, allanite is exclusively encountered in the SG. Mineral chemistry study reveals that Nb-Ta-Ti-bearing oxides [columbite-group minerals (CGM)] and Nb-bearing oxides (ilmenorutile) represent the most common Nb-Ta host in the AFG. The CGM are represented mostly by complex zoned columbite-(Fe) and rarely by yttrocolumbite-(Y), with Mn/(Mn+Fe) ratios ranging from 0.17 to 0.31. Xenomorphic fluorite (F=46-51 wt%) is commonly filling the spaces between the major mineral phases and sometimes host rare metal minerals, e.g. columbite and thorite. Euhedral zoned allanite (Ce-Nd) is the common REE bearing mineral encountered in the SG. Geochemically, Gabal El-Ineigi granitoids are metaluminous (A/CNK= 0.95-0.99) related to post-collosional A2-type granites. The late phase AFG have distinctive geochemical features typical of rare-metal granites. They are highly fractionated calc-alkaline granitoids characterized by high Rb, Nb, Y, U and many HFSE contents, and extremely low Sr and Ba contents (4-35 and 13-18 ppm, respectively). Moreover, their REE patterns show pronounced negative Eu anomalies (Eu/Eu*=0.03 - 0.05) and tetrad effect (TE1,3=1.16 and 1.42), implying extensive fractionation via fluid-rock interaction that

  8. Garnet cannibalism provides clues to extensive hydration of lower crustal fragments in a subduction channel (Sesia Zone, Northwestern Alps)

    Science.gov (United States)

    Giuntoli, Francesco; Lanari, Pierre; Engi, Martin

    2015-04-01

    the expense of earlier Alpine rims. In the same samples that show porphyroclastic garnet, atoll garnet occurs, filled with quartz, and the same Alpine overgrowth zones are observed in both types of garnet. Similar features of garnet zoning are present in various lithotypes, allowing the evolution of this continental domain during subduction to be traced. Modeling the different garnet growth zones is challenging, each growth step demanding an estimate the effective bulk composition. According to the XRF analyses of the bulk sample, the core is found to have formed at 900°C, 0.9 GPa. Based on effective bulk compositions, the successive Alpine rims are found to reflect an increase from 600°C, 1.55-1.60 GPa for rim 1 to 630-640°C, 1.9-2.0 GPa for rim 2. Allanite crystals contain inclusions of Alpine garnet; in situ geochronology (U-Th-Pb by LA-ICP-MS) on allanite yields a (minimum) age of ~69 Ma for the main growth of garnet. In summary, the textures and mineral compositions clearly reflect reactive interaction of major amounts of hydrous fluids with dry protoliths. The source of these fluids responsible for converting granulites back to micaschists at eclogite facies conditions within the Sesia subduction channel is being investigated.

  9. Contribution to uranium geochemistry in intrusive granites; Contribution a la geochimie de l'uranium dans les granites intrusifs

    Energy Technology Data Exchange (ETDEWEB)

    Coulomb, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-01-15

    This work aims to define the position of a certain number of French granitic deposits within the field of the geochemistry of granites in general, and of the geochemistry of uranium in particular. The regions concerned are: - 3 French Hercynian ranges, in the Vendee, in Brittany and in the Morvan, - 1 African range, probably precambrian, of the Hoggar. For each range, the petrochemical framework is first of all determined and then the degree of chemical homogeneity of the rocks is evaluated. In the petrochemical groups thus obtained the geochemical behaviour of the uranium is studied. From a point of view of the geochemistry of the granites under investigation, a comparison of the laws of distribution of the major elements in the 4 ranges shows up a convergence of average composition which was not anticipated by geological and petrographic considerations alone. The statistical and geochemical distribution laws of the total uranium as a function of the petrochemical variations are established. A study of the chemical forms of uranium in the rocks has drawn an attention to the qualitative and quantitative importance of the fraction of this uranium soluble in dilute acids. We have therefore reconsidered on the one hand, the laws of distribution of the insoluble uranium, which represents essentially the uranium fixed in crystalline structures (zircon, allanite...), and we have justified on the other hand the interest presented by the soluble uranium: this, although more complex in character, presents a geochemical unity in post magmatic phenomena which makes possible to find a genetic connection between the uraniferous deposits and the intrusive massifs. Finally we have given a plan of the geochemical cycle of uranium, in which we hope to have provided some more accurate data on the igneous phase. (author) [French] Le but du travail presente est de situer sur le plan de la geochimie des granites en general, sur le plan de la geochimie de l'uranium en particulier

  10. Geology and Geochemistry of the Early Proterozoic Kortejärvi and Laivajoki Carbonatites, Central Fennoscandian Shield, Finland

    Directory of Open Access Journals (Sweden)

    Nykänen, J.

    1997-12-01

    Full Text Available This paper provides for the first time extensive petrological, mineralogical and geochemical data on the early Proterozoic Kortejärvi and Laivajoki carbonatites, northern Finland, which form metamorphosed and highly strained bodies 2 and 4 km long within a Svecokarelian shear zone in central Fennoscandian Shield. They are not exposed, but have been penetrated by a couple of deep drill holes. In terms of modal mineralogy, both intrusions contain calcite carbonatite and dolomite-calcite carbonatite as their main rock types, but Kortejärvi also contains dolomite carbonatite and calcite-dolomite carbonatite, some glimmerite and olivine-magnetite rock and Laivajärvi tremolite-calcite carbonatite, tremolite-dolomite carbonatite, serpentine-talc-dolomite rock and glimmerite. The main country rock is an amphibolite which is not fenitized. No alkaline rocks have been detected in these intrusions. Calcite is most common mineral in both occurrences. Other carbonate minerals include dolomite with minor ankerite and occassional siderite. In addition to low-Ti phlogopite, tetraferriphlogopite is also encountered. Fresh olivine is rare, and its alteration products include titaniferous clinohumite. The amphiboles are mainly calcic amphiboles, including actinolite, tremolite and edenite. The only sodic-calcic amphibole is accessory richterite. Other essential minerals are Ti-poor magnetite with ilmenite exsolutions, fluorapatite (3.95-4.89 wt. % F, monazite, and allanite-(Ce. Geochemically, the Kortejärvi rocks are mostly magnesiocarbonatites, whereas those of Laivajärvi, due to their higher magnetite content, are ferrocarbonatites. Of the trace elements, Nb is much lower (8-30 ppm in proper carbonatites than the average for carbonatites and U and Th (<0.9 ppm and<2.4 pm, respectively lower than average. Sr is typical, but not high (1830-3480 ppm, and Ba is rather low (27-348 ppm. The REEs are hosted by allanite and monazite and their concentrations in the

  11. La asociacion Monzonitica del Domo Anatectico del Tormes: geoquimica y petrogenesis

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    López Plaza, M.

    2001-08-01

    Full Text Available In certain peripheral zones of the Anatectic Tormes Dome there exists a group of rocks, which are from basic to acid as well as rich in alkali feldspar, apatite and allanite. Such an unusual mineralogy makes the rocks to be enriched in K20, P2O5, LREE and other elements of low ionic potential. Their geochemical signature is related to the volcanic shoshonites, to the vaugnerites of the French Central Massif as well as to the monzonitic series of Ballon, being, in turn, almost exceptional in the iberian variscan. The least evolved terms are rather fractionated, therefore, they are not primary melts. During the differentiation, the saturation of accessory phases such as apatite, allanite and zircon exerts an important effect in the evolution of the residual liquid giving rise to an inflection point in the Harker diagrams. From the good adjustments obtained in mass balance and Rayleigh fractionation modelling, we can infer that the process of fractional crystallization is the dominant one. In this respect, the porphyritic granitoids can be derived from a liquid of monzodioritic composition, being rocks genetically to the associated acid rocks. The corroded cores of plagioclase and the spatial relations suggest the existence of different pulses of magma from basic to acid coming from the same magmatic chamber.En dos bandas del Domo anatéctico del Tormes aparece un conjunto de rocas plutónicas desde básicas a ácidas ricas en feldespato potásico, apatito y allanita. Esta mineralogía tan particular hace que estén enriquecidas en K20, P205, LREE y otros elementos de bajo potencial iónico. Su quimismo es afín a las shoshonitas volcánicas, a las vaugneritas del Macizo Central francés y a las series monzoníticas de Ballon, siendo, a su vez, casi excepcional en el varisco ibérico. Los términos menos evolucionados están bastante fraccionados por lo que no se trata de fundidos primarios. Durante la diferenciación existen fases accesorias como

  12. Geochemistry of hydrothermal veins containing zirconolite and betafite at Adamello, Italy

    International Nuclear Information System (INIS)

    Hydrothermal veins containing zirconolite and betafite occur in dolomite marbles at the contact with a tonalite intrusion of the Adamello batholith, Italy. The veins display four distinct mineral zones and are highly enriched in Th, U, Ti, Zr, Nb, and rare earth elements (REE) relative to their host rock .Wide ranges in concentration of these elements and distinct inter-element fractionation trends exist across the four vein zones. The behavior of Th closely reflects that of P, Ti, Nb, and heavy REE, but was distinct from that of U, Zr and light REE (La to Sm). The presence and composition of refractory minerals such as zirconolite, betafite, uraninite, thonanite, baddeleyite, rutile, allanite, and aeschynite provide evidence for the transport of Ti, Zr, Nb, REE, and actinides by a fluid, which was further characterized by a low pH and high contents of F, P, Cl and H2S. Thermodynamic analysis of these veins indicates that they were formed at 550-600 deg C, 200 MPa total pressure, and from a fluid derived from the tonalite. Mineralogical and textural observations suggest that crystallization of the refractory minerals was in part induced by precipitation of fluorapatite and sulfides. The geochemical data further indicate that precipitation of light REE was induced by the fluid/wall-rock interaction which led to a significant dilution of the fluid by CO2. The studied veins provide an example of high-temperature transport of actinides and REE in the Earth's crust and show that these elements can be precipitated from a fluid and subsequently immobilized by zirconolite and betafite, two important actinide hosts in ceramic nuclear waste forms. Copyright (2001) Material Research Society

  13. Geology and rare-earth element geochemistry of highly evolved, molybdenite-bearing granitic plutons, Southeastern Desert, Egypt

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The field relations, mineralogy, and major and trace elements (including REE analyses of whole-rock samples and minerals) of granites and their associated molybdenite + uranium mineralized aplites in Southeastern Desert, Egypt, have been studied. The granites are leucocratic and mostly peraluminous in nature with muscovite increasing at the expense of biotite. The chemical and mineralogical characteristics of the granitic rocks indicate that their melts originated from the LILE-enriched mantle wedge by partial melting and are contaminated by crustal melts, followed by thermogravitational processes. Leucogranites with higher Na2O/K2O ratios from Um Dargag and Um Maiat crystallized under H2O-saturated equilibrium conditions in which the exsolved vapor continuously migrated away. The REE patterns of the granites studied are characterized by LREE enrichments and negative Eu anomalies. In comparison, the potassic aplites and the more sodic leucogranites are depleted in LREE, enriched in HREE and show more remarkable negative Eu anomalies. Allanite and monazite are the most important REE carriers in the granites. These minerals are strongly enriched in LREE, whereas fluorite and xenotime, which are more abundant in the aplites, are enriched in HREE. The average Lu/Ce ratio represents the fractionation trend with respect to HREE. It is 0.71 for radioactive fluorite, and it increases to 1.22 for non-radioactive fluorite. The high REE contents of molybdenite represent re-deposition of the mobilized Mo and REE. Due to the strong control of accessory minerals, the REEs are of limited use in petrogenetic modelling of highly evolved granitic systems.

  14. Preliminary study of prospect monazite minerals in Kendawangan West Kalimantan

    International Nuclear Information System (INIS)

    Kendawangan areas is included in the regional geological coverage area of Ketapang that is identified have monazite deposits with radioactive minerals contain is uranium (U), thorium (Th) and rare earth element (REE). Results of grain counting analysis shows the content of the mineral monazite and zircon in heavy mineral grains reached 63% to 40% (of total grains). the analysis of rock samples contained grains of 0.11% monazite. The study was conducted on secondary data covering aspects of geology, source rock, traps and interpretation of heavy mineral distribution placer contain monazite and zircon. Objectives to be obtained is information about the character of the geology and distribution of monazite mineral resources with Thorium-contain and zircon. Source rock of monazite minerals is a granite 77-150 million age (Jurassic - Late Cretaceous), including the S type of the alkaline granites. formed in pegmatitic stage which advanced differentiated at a temperature 550-600° Celsius . The anomalous radioactivity of Granite has a value of 400 c/s-9200 c/s with the characterized minerals are K-feldspar, quartz and plagioclase. minerals accompanying the form as thorite, monazite zircon and allanite. Uranium range of the granitic rocks is 2.5 ppm - 64.8 ppm. The lateral distribution of alluvial deposits containing monazite placer occupy at flood plains valley between of hilly land area 225,040 Ha, obeying the distribution pattern of granitic rocks. Monazite prospect area lies in the valley flood plain of the watershed at Sungai Kendawangan (107.800 Ha), Sungai Air tanah dingin (27.610 Ha), Sungai Tapah (42.010 Ha) dan Sungai Naning (45.010 Ha). The potential is area target to ore deposit prospective at the next stage field investigation. (author)

  15. Uranium potential of precambrian rocks in the Raft River area of northwestern Utah and south-central Idaho. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Black, B.A.

    1980-09-01

    A total of 1214 geochemical samples were collected and analyzed. The sampling media included 334 waters, 616 stream sediments, and 264 rocks. In addition, some stratigraphic sections of Elba and Yost Quartzites and Archean metasedimentary rock were measured and sampled and numerous radiation determinations made of the various target units. Statistical evaluation of the geochemical data permitted recognition of 156 uranium anomalies, 52 in water, 79 in stream sediment, and 25 in rock. Geographically, 68 are located in the Grouse Creek Mountains, 43 in the Raft River Mountains, and 41 in the Albion Range. Interpretation of the various data leads to the conclusion that uranium anomalies relate to sparingly and moderately soluble uraniferous heavy minerals, which occur as sparse but widely distributed magmatic, detrital, and/or metamorphically segregated components in the target lithostratigraphic units. The uraniferous minerals known to occur and believed to account for the geochemical anomalies include allanite, monazite, zircon, and apatite. In some instances samarskite may be important. These heavy minerals contain uranium and geochemically related elements, such as Th, Ce, Y, and Zr, in sufficient quantities to account for both the conspicuous lithologic preference and the generally observed low amplitude of the anomalies. The various data generated in connection with this study, as well as those available in the published literature, collectively support the conclusion that the various Precambrian W and X lithostratigraphic units pre-selected for evaluation probably lack potential to host important Precambrian quartz-pebble conglomerate uranium deposits. Moreover it is also doubted that they possess any potential to host Proterozoic unconformity-type uranium deposits.

  16. The Life and Times of Supervolcanoes: Inferences from Long Valley Caldera

    Science.gov (United States)

    Simon, Justin

    2014-01-01

    Cataclysmic eruptions of silicic magma from "supervolcanoes" are among the most awe-inspiring natural phenomena found in the geologic record, in terms of size, power, and potential hazard. Based on the repose intervals between eruptions of this magnitude, the magmas responsible for them could accumulate gradually in the shallow crust over time scales that may be in excess of a million years (Smith, 1979; Spera and Crisp, 1981; Shaw, 1985). Pre-eruption magma residence time scales can also be inferred from the age difference between eruption (i.e., using 40Ar/39Ar dating to determine the time when hot erupted material cools to below its Ar closure temperature, 200 to 600 degC) and early pre-eruption crystallization (i.e., zircon saturation temperatures; Reid et al., 1997). I will discuss observations from Long Valley a Quaternary volcanic center in California. Long Valley is a voluminous, dominantly silicic caldera system. Based on extensive dating of accessory minerals (e.g., U-Th-Pb dating of zircon and allanite) along with geochemical and isotopic data we find that silicic magmas begin to crystallize 10's to 100's of thousands of years prior to their eruption and that rhyolites record episodes of punctuated and independent evolution rather than the periodic tapping of a long-lived magma. The more punctuated versus more gradual magma accumulation rates required by the absolute and model ages, respectively, imply important differences in the mass and heat fluxes associated with the generation, differentiation, and storage of voluminous rhyolites and emphasize the need to reconcile the magmatic age differences.

  17. 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.

  18. Geochemistry of the Neoarchaean Volcanic Rocks of the Kilimafedha Greenstone Belt, Northeastern Tanzania

    Directory of Open Access Journals (Sweden)

    Charles W. Messo

    2012-01-01

    Full Text Available The Neoarchaean volcanic rocks of the Kilimafedha greenstone belt consist of three petrological types that are closely associated in space and time: the predominant intermediate volcanic rocks with intermediate calc-alkaline to tholeiitic affinities, the volumetrically minor tholeiitic basalts, and rhyolites. The tholeiitic basalts are characterized by slightly depleted LREE to nearly flat REE patterns with no Eu anomalies but have negative anomalies of Nb. The intermediate volcanic rocks exhibit very coherent, fractionated REE patterns, slightly negative to absent Eu anomalies, depletion in Nb, Ta, and Ti in multielement spidergrams, and enrichment of HFSE relative to MORB. Compared to the other two suites, the rhyolites are characterized by low concentrations of TiO2 and overall low abundances of total REE, as well as large negative Ti, Sr, and Eu anomalies. The three suites have a εNd (2.7 Ga values in the range of −0.51 to +5.17. The geochemical features of the tholeiitic basalts are interpreted in terms of derivation from higher degrees of partial melting of a peridotite mantle wedge that has been variably metasomatized by aqueous fluids derived from dehydration of the subducting slab. The rocks showing intermediate affinities are interpreted to have been formed as differentiates of a primary magma formed later by lower degrees of partial melting of a garnet free mantle wedge that was strongly metasomatized by both fluid and melt derived from the subducting oceanic slab. The rhyolites are best interpreted as having been formed by shallow level fractional crystallization of the intermediate volcanic rocks involving plagioclase and Ti-rich phases like ilmenite and magnetite as well as REE-rich phases like apatite, zircon, monazite, and allanite. The close spatial association of the three petrological types in the Kilimafedha greenstone belt is interpreted as reflecting their formation in an evolving late Archaean island arc.

  19. 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.

  20. 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.

  1. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Saudi Arabia

    International Nuclear Information System (INIS)

    Saudi Arabia occupies most of the Arabian Peninsula and has an area of 872,722 sq miles, or 2,260,350 sq km. The ancient Arabian Shield of igneous and metamorphic rocks comprises most of the western third of the country. The shield contains many extinct volcanoes surrounded by lava beds. Sloping eastwards are the newer sedimentary areas in which rich oil fields are found. In Saudi Arabia oil is paramount and less effort has been put into searching for mineral deposits than in other countries of similar size and geology. Pour aerial radiometric surveys have been undertaken and some of the anomalies discovered in the earlier ones were ground checked by an IAEA expert in 1963-64. Two anomalies warranted more detailed work, these were the Jabal Said anomaly in the Central Shield area and the Al Ghrayyat in Wadi Sawawin about 70 miles from the Jordan border. The Jabal Said anomaly consists of a zone of altered rocks consisting largely of pegmatite and pegmatite granite= Allanite, pyrochlore, cyrtolite, xenotime and monazite are the ore minerals,, The deposit was estimated to have 2.2 million tons of ore grading 0.2 - 0.3 percent Nb2O5 and 0.03 - 0,05% U3O8. The other occurrence at Al Ghrayyat is similar but with much lower grade uranium content. In view of the huge size of Saudi Arabia, the existence of many geologically favourable rock types and the poor coverage by sophisticated uranium exploration techniques, the Speculative Potential is placed between 10,000 and 50,000 Tonnes uranium. (author)

  2. Element redistribution and mobility during upper crustal metamorphism of metasedimentary rocks: an example from the eastern Mount Lofty Ranges, South Australia

    Science.gov (United States)

    Hammerli, Johannes; Spandler, Carl; Oliver, Nicholas H. S.

    2016-04-01

    We present a detailed study on element mobility during prograde metamorphism of metasedimentary rocks of the eastern Mt. Lofty Ranges, South Australia. Mineral and bulk rock compositions were monitored across a regional metamorphic gradient from ≈350-400 °C to migmatite grade (≈650-700 °C) at ≈0.3-0.5 GPa, where pervasive up-temperature fluid flow during metamorphism has been proposed previously. Major and most trace elements (including rare earth elements) are isochemical during metamorphism as they are effectively redistributed into newly formed major and/or accessory minerals. Monazite or allanite and xenotime control the whole rock concentration of rare earth elements (REEs), whereas apatite and titanite are minor REE hosts. The only non-volatile elements that are demonstrably mobilized by metamorphic fluids are Zn, Pb, Ag, Cs, Sb, Bi and As, whose concentrations decreased with increasing metamorphic grade. Depletion of Zn, Sb and Pb was progressive with increasing temperature in staurolite-absent psammopelites, with losses of ≈80 % of the original Zn and >80 % of the protolithic Sb and ≈50 % of the original Pb from the rocks from high-grade metamorphic zones. Pronounced depletion of As and Cs occurs at the greenschist/amphibolite facies boundary and the transition to migmatite grade, respectively, while Ag and Bi contents decrease between 500 and 550 °C where >50 % of the original Ag and Bi is lost. While for most elements, unmetamorphosed sedimentary sequences can be considered chemical equivalents of metasedimentary rocks occupying deeper crust levels, in some cases, such as the extensive flow of Cl-rich fluid documented here, metals such as Zn, Pb and Ag may be stripped and may serve as a metal source for orebody formation. The decrease of As, Bi and Sb contents during prograde metamorphism might be a more universal feature that is linked with sulphide phase transitions.

  3. Spatial distribution and compositional variation of APS minerals related to uranium deposits in the Kiggavik-Andrew Lake structural trend, Nunavut, Canada

    Science.gov (United States)

    Riegler, Thomas; Quirt, Dave; Beaufort, Daniel

    2016-02-01

    The Kiggavik-Andrew Lake structural trend consists of four mineralized zones, partially outcropping, lying 2 km south of the erosional contact with the unmetamorphosed sandstone and basal conglomerates of the Paleoproterozoic Thelon Formation. The mineralization is controlled by a major E-W fault system associated with illite and sudoite alteration halos developed in the Archean metagraywackes of the Woodburn Lake Group. Aluminum phosphate sulfate (APS) minerals from the alunite group crystallized in association with the clay minerals in the basement alteration halo as well as in the overlying sandstones, which underwent mostly diagenesis. APS minerals are Sr- and S-rich (svanbergite end-member) in the sedimentary cover overlying the unconformity, whereas they are light rare earth elements (LREE)-rich (florencite end-member) in the altered basement rocks below the unconformity. The geochemical signature of each group of APS minerals together with the petrography indicates three distinct generations of APS minerals related to the following: (1) paleoweathering of continental surfaces prior to the basin occurrence, (2) diagenetic processes during the burial history of the lower unit of the Thelon sandstones, and (3) hydrothermal alteration processes which accompanied the uranium deposition in the basement rocks and partially overlap the sedimentary-diagenetic mineral parageneses. In addition, the association of a first generation of APS minerals with both detrital cerium oxide and aluminum oxy-hydroxide highlights the fact that a part of the detrital material of the basal Thelon Formation originated from eroded paleolaterite (allochthonous regolith). The primary rare earth element (REE)-bearing minerals (e.g., monazite, REE carbonates, and allanite) of the host rocks were characterized to identify the potential sources of REE. The REE chemical composition highlights a local re-incorporation of the REE released from the alteration processes in the APS minerals of

  4. Petrogenesis and tectonic implications of the high-K Alamas calc-alkaline granitoids at the northwestern margin of the Tibetan Plateau: Geochemical and Sr-Nd-Hf-O isotope constraints

    Science.gov (United States)

    Zhang, Qichao; Liu, Yan; Huang, He; Wu, Zhenhan; Zhou, Qing

    2016-09-01

    The Alamas granitoid pluton in the eastern part of the Western Kunlun Orogen, the northwestern margin of the Tibetan Plateau, is composed of quartz diorite. Zircon separates from the pluton has SIMS U-Pb age of ∼446 Ma. Rocks from the pluton have a narrow range of SiO2 (56.84-62.57 wt%), MgO (1.76-2.94 wt%), and total alkalis (Na2O + K2O = 5.14-9.59 wt%), and are metaluminous and high-K calc-alkaline to shoshonitic in composition. They are enriched in light rare earth elements (LREEs), with (La/Yb)N = 14-25, and show weakly negative Eu anomalies. These rocks are relatively enriched in Sr (472-676 ppm) and Ba (435-2388 ppm), and depleted in Nb, Ta, Th, and Ti. Their εNd(t) values range from -6.4 to -8.4, and (87Sr/86Sr)i = 0.7184-0.7200. Zircons from the pluton show εHf(t) values of -1.4 to -8.8, and δ18O = 6.4-9.0‰. Geochemical data indicate that the granitoids were likely derived from the reworking of an ancient, deep crustal source, influenced by a minor mantle-derived component. Magmatic differentiation was dominated by the fractional crystallization of hornblende, biotite, and accessory minerals such as apatite, allanite, and Fe-Ti oxides. In summary, the Late Ordovician Alamas pluton is an I-type granitoid that was emplaced in a post-collisional environment, suggesting that this tectonic stage had already initiated prior to ∼445 Ma.

  5. Critical Zone Weathering and Your Smartphone: Understanding How Mineral Decomposition and Colloid Redistribution Can Generate Rare Earth Element Deposits

    Science.gov (United States)

    Bern, C.; Foley, N.

    2014-12-01

    Rare earth elements (REE's) are crucial in the manufacture of smartphones and many other high tech devices. Increasing global demand and relatively narrow geographic sourcing have promoted interest in understanding REE deposit genesis and distribution. Highly weathered, clay-hosted, ion-exchange type deposits in southern China are the source of much of the world's production of the more valuable heavy REEs. Such deposits form as REE-bearing minerals weather and REEs released to solution in ionic form are retained by negatively charged exchange sites on clay minerals. We are investigating the potential for ion-exchange REE deposits in the Piedmont of the southeastern United States, where slow erosion rates have preserved thick (up to 20 m) regolith, as required for such deposits. The Liberty Hill pluton outcrops as coarse-grained biotite-amphibole granite and quartz monzonite over nearly 400 km2 in South Carolina, and has an age of 305 Ma (new SHRIMP ion microprobe zircon age). In weathered profiles over the pluton, ion-exchangeable REE content ranges from 8 to 580 ppm and accounts for 2 to 80% of bulk REE content. Elemental and heavy mineral distributions suggest the wide ranging differences in leachability may be attributable to the amount and distribution of resistant REE-bearing phases (e.g., monazite) relative to more easily weathered phases (e.g., allanite) in the parent granite. The REEs show little mobility within the regolith, indicating the effectiveness of the ion-exchange retention mechanism. In contrast, vertical redistribution of colloidal material shows maximum accumulations at ~1 m depth, as traced by the newly developed dual-phase (colloids vs. solution) mass balance model. The contrast suggests redistributed colloidal material has minimal influence on REE mobilization or retention. Conditions and processes necessary for ion-exchange REE deposit development exist in the Piedmont, but their presence will depend upon favorable parent rock mineralogy.

  6. "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.

  7. The petrogenesis of metamorphosed carbonatites in the Grenville Province, Ontario

    Energy Technology Data Exchange (ETDEWEB)

    Moecher, D.P.; Anderson, E.D.; Cook, C.A. [Univ. of Kentucky, Dept. of Geological Sciences, Lexington, Kentucky (United States)]. E-mail: moker@pop.uky.edu; Mezger, K. [Max-Planck-Institut fuer Chemie, Mainz (Germany)

    1997-09-15

    Veins and dikes of calcite-rich rocks within the Central Metasedimentary Belt boundary zone (CMBbz) in the Grenville Province of Ontario have been interpreted to be true carbonatites or to be pseudocarbonatites derived from interaction of pegmatite melts and regional Grenville marble. The putative carbonatites have been metamorphosed and consist mainly of calcite, biotite, and apatite with lesser amounts of clinopyroxene, magnetite, allanite, zircon, titanite, cerite, celestite, and barite. The rocks have high P and rare earth element (REE) contents, and calcite in carbonatite has elevated Sr, Fe, and Mn contents relative to Grenville Supergroup marble and marble melange. Values of {delta}{sup 18}O{sub SMOW} (9.9 - 13.3o/oo) and {delta}{sup 13}C{sub PDB} (-4.8 to -1.9o/oo) for calcite are also distinct from those for marble and most marble melange. Titanites extracted from clinopyroxene -calcite-scapolite skarns formed by metasomatic interaction of carbonatites and silicate lithologies yield U-Pb ages of 1085 to 1035 Ma. Zircon from one carbonatite body yields a U-Pb age of 1089 {+-} 5 Ma; zircon ages from two other bodies are 1170 {+-} 3 and 1143 {+-} 8 Ma, suggesting several carbonatite formation events or remobilization of carbonatite during deformation and metamorphism around 1080 Ma. Values of {epsilon}{sub Nd}(T) are 1.7 - 3.2 for carbonatites, -1.5 -1.0 for REE-rich granite dikes intruding the CMBbz, and 1.6 - 1.7 for marble. The mineralogy and geochemical data are consistent with derivation of the carbonatites from a depleted mantle source. Mixing calculations indicate that interaction of REE-rich pegmatites with regional marbles cannot reproduce selected major and minor element abundance, REE contents, and O and Nd isotope compositions of the carbonatites. (author)

  8. Assessment of gamma radiation exposure and distribution of natural radioactivity in beach sands associated with plutonic rocks of Greece

    Science.gov (United States)

    Papadopoulos, Argyrios; Koroneos, Antonios; Christofides, Georgios; Stoulos, Stylianos

    2016-04-01

    This study aims to evaluate the activity concentrations of 238U, 226Ra, 232Th, 228Th and 40K along beaches of Greece associated with plutonic rocks. They range from 6-940, 1-2292, 5-10143, 5-9953 and 27-1319 Bq/kg respectively, with some of them representing the highest values of natural radioactivity measured in sediments in Greece. The investigated beaches include Sithonia peninsula (Chalkidiki, N. Greece), some islands of the Aegean Sea (Mykonos, Paros, Naxos, Serifos, Ikaria), the area of Kavala (N. Greece), Samothraki island, NE Chalkidiki and Maronia (NE Greece). Several of these places are associated with high touristic activity such as Mykonos, Naxos, Paros, Serifos, Ikaria, Sithonia and Kavala. The (% wt.) heavy magnetic fraction (HM) (allanite, amphibole, mica, clinopyroxene, magnetite and hematite), the heavy non-magnetic fraction (HNM) (monazite, zircon, titanite and apatite) and the total heavy fraction (TH), were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of 238U and 232Th of all the samples, showing some local differences in the main 238U and 232Th mineral carrier. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which are their most probable parental rocks, so as to provide data upon their enrichment or depletion. The highest values of the equivalent dose have been reported in Mykonos, Naxos, Kavala and Sithonia. The annual equivalent dose which should be limited to at least 1 mSv y-1, varies between 0.003 and 0.759 mSv y-1 for tourists and from 0.012 to 3.164 mSv y-1 for local people working on the beach.

  9. Uranium potential of precambrian rocks in the Raft River area of northwestern Utah and south-central Idaho. Final report

    International Nuclear Information System (INIS)

    A total of 1214 geochemical samples were collected and analyzed. The sampling media included 334 waters, 616 stream sediments, and 264 rocks. In addition, some stratigraphic sections of Elba and Yost Quartzites and Archean metasedimentary rock were measured and sampled and numerous radiation determinations made of the various target units. Statistical evaluation of the geochemical data permitted recognition of 156 uranium anomalies, 52 in water, 79 in stream sediment, and 25 in rock. Geographically, 68 are located in the Grouse Creek Mountains, 43 in the Raft River Mountains, and 41 in the Albion Range. Interpretation of the various data leads to the conclusion that uranium anomalies relate to sparingly and moderately soluble uraniferous heavy minerals, which occur as sparse but widely distributed magmatic, detrital, and/or metamorphically segregated components in the target lithostratigraphic units. The uraniferous minerals known to occur and believed to account for the geochemical anomalies include allanite, monazite, zircon, and apatite. In some instances samarskite may be important. These heavy minerals contain uranium and geochemically related elements, such as Th, Ce, Y, and Zr, in sufficient quantities to account for both the conspicuous lithologic preference and the generally observed low amplitude of the anomalies. The various data generated in connection with this study, as well as those available in the published literature, collectively support the conclusion that the various Precambrian W and X lithostratigraphic units pre-selected for evaluation probably lack potential to host important Precambrian quartz-pebble conglomerate uranium deposits. Moreover it is also doubted that they possess any potential to host Proterozoic unconformity-type uranium deposits

  10. Mineralogy and Radioactivity of the Acidic Dokhan Volcanics of Gabal Nuqara, Central Eastern Desert. Egypt

    International Nuclear Information System (INIS)

    The present work aims to study the mineralogy as well as the radioactivity of the acidic Dokhan volcanic in Gabal Nuqara area to identify the minerals that responsible for the radioactivity. The Dokhan volcanic of Gabal Nuqara, Central Eastern Desert are related to fissure-type eruption and are subdivided into intermediate and acidic volcanics. The acidic Dokhan volcanics rocks are located as two elongated flows of rhyolite, dacite and their tuffs, trending NW-SE direction and cut by younger granites and younger gabbros. Radiomatically, tuffs and dacite rocks show low radioactivity, while the concerned rhyolite exhibits relatively high eTh and eU contents (140 ppm and 89 ppm in average respectively). Moreover, an anomalous content was recorded in rhyolite rocks where eTh and eU contents are 745 ppm and 280 ppm in average, respectively. The detailed mineralogical studies, using ESEM and XRD techniques, indicate the presence of some primary radioactive minerals that are responsible for the radioactivity of the Nuqara rhyolites (e.g. thorite and uranothorite). Furthermore, samarskite, zircon and allanite occur as uraniferous accessory minerals. The mineral chemistry by EPMA analysis of thorite reflects the main following components; ThO2 (38 %), SiO2 (33 %) and UO2 (6 %), while the main constituents of uranothorite are ThO2 (40 %), SiO2 (20 %), and UO2 (12 %). Beside, the studied zircon crystals display a large chemical variability between core and rim. Zircon and thorite from Nuqara rhyolite are demonstrably magmatic origin, can be attributed concentrated in the rhyolite extrusive

  11. The contribution of geochronology to determination of burial and exhumation rates of (U)HP rocks

    Science.gov (United States)

    Parrish, R. R.; Cottle, J.; Condon, D.

    2008-12-01

    The seemingly extraordinary rapid and deep subduction of buoyant continental crust and its return to the surface is proving rather more the rule than the exception in continental collision zones, notwithstanding the patchy preservation of such rocks. Modelling and buoyancy contrasts suggest that following rapid subduction and ductile de-coupling from the downgoing slab, the rate of exhumation is first very rapid within the mantle but slower as the buoyancy contrast is reduced in the crust. One test of models is the quantitative determination of the P-t path of real samples. Geochronology is pivotal in this regard and with rapid exhumation (˜1 cm/a), it is paramount to produce precise and robust mineral growth and cooling ages of a variety of pressure- and temperature-sensitive minerals, ideally in their petrographic context, using a variety of chronometers, so that the geochronology can resolve the rapid rates. Issues of high relevance to this application of geochronology are (1) resolving and applying the ~0.5-1.0% decay constant bias between (40K)40Ar-39Ar dates and U-Pb dates, especially critical for older orogen exhumation rates (i.e. Caledonides); (2) correctly interpreting U-Pb ages when complex U-Pb systematics are likely to be present; (3) using prograde mineral chronology during cool subduction with minerals of high closure temperature (allanite-epidote, garnet, monazite, zircon, titanite); (3) determining P-T conditions of growth of these minerals using metamorphic modelling and chemical mapping; dating minerals in their petrographic context wherever possible; (5) making the most of minerals like zircon through innovative dating and inclusion petrology in very thin overgrowths; (5) and assessing growth v. closure temperature interpretation of dated minerals using experimental and empirical diffusion data. These points will be illustrated by examples of studies from Kaghan Himalayan, Caledonide and Chinese UHP rocks to suggest fruitful multi

  12. Preliminary geological assessment for rare earths at Ombo Area, San Vicente, Northern Palawan

    International Nuclear Information System (INIS)

    A preliminary geological assessment for rare earths was conducted along Ombo beach area, San Vicente, northern Palawan to evaluate the potential geologic reserve and to determine the relative concentration of REE, thorium and uranium. This investigation also aims to establish the distribution of heavy minerals. The study area, covering, about 6500 m2 is comprised of the undisturbed beach sand deposits confined between the high tide line and the base of the mountains that borders the coastline. The investigation involved the establishment of shallow test pits with depths varying from one meter ot less than three meters. A total of 23 heavy mineral panned concentrates were collected. All the samples were analyzed for REE, Th and U using the portable X-MET 820 x-ray fluorescence and GR-320 gamma ray spectrometer. Radiometric measurements were also taken along the stretch of Ombo beach to establish the natural background radioactivity. The radiometric values vary from 27 cps to 420 cps. The high readings could be attributed to the presence of radioactive rare earth bearing minerals, principally allanite. This initial investigation indicates a positive geologic reserve of approximately 19,000 metric tons beach sand deposits, containing an average grade of 22.19% REE (Ce, La), 0.85% Th and 0.55% U. The average distribution of heavy minerals is 3600 gm heavies per cubic meter. Moreover, a probable geologic reserve of about 41,000 metric tons with an average grade of 22.13% REE (Ce, La), 0.85% Th and 0.55% U was also determined. The average distribution of heavy minerals is about 3300 gm heavies per cubic meter. (Author)

  13. Inferences on the Mesozoic evolution of the North Aegean from the isotopic record of the Chalkidiki block

    Science.gov (United States)

    Kydonakis, Konstantinos; Brun, Jean-Pierre; Poujol, Marc; Monié, Patrick; Chatzitheodoridis, Elias

    2016-07-01

    The Chalkidiki block is a major domain in the North Aegean that, contrary to other domains in the region, largely escaped thermal perturbations during Tertiary extension. As a result, the Chalkidiki block is an ideal candidate to glean information related to the timing of Mesozoic thermal events using appropriate geochronological techniques. We have undertaken a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study (U-Th-Pb on monazites and U-Pb on zircons) coupled with 40Ar/39Ar dating on nine samples from various structural levels within the thrust system of the Chalkidiki block. The eastern, and structurally lower part of the system revealed a complete isotopic reset of Carboniferous - Early Triassic monazites coeval with partial monazite destruction, REE-mobilisation and formation of apatite-allanite-epidote coronas at ~ 132 Ma, a reaction that is commonly observed in amphibolite-facies rocks. These coronas formed after crystallisation of garnet (i.e., at T > 580 °C) and, in all probability, either close to the peak-temperature conditions (~ 620 °C) on a prograde path or during retrogression between the peak-temperature and the low-temperature boundary of the amphibolite facies. Cooling of these rocks and arrival at mid-crustal levels occurred at 95-100 Ma. By contrast, the western, and structurally uppermost part of the system went through the same event by 120-125 Ma. Further structural considerations with respect to medium-temperature geochronology data imply that syn-metamorphic thrusting must have ceased by early Late Cretaceous. We emphasize that, with the sole exception of the Chalkidiki block, no pre-45 Ma medium-temperature geochronology data are preserved in other North Aegean domains, a feature that is clearly related to the extension-induced thermal perturbation of the region during the Tertiary.

  14. Natural radionuclide concentrations in granite rocks in Aswan and Central-Southern Eastern Desert (Egypt)) and their radiological implications

    International Nuclear Information System (INIS)

    Different types of granites, used extensively in local construction, were collected from five localities in Egypt, namely: Abu Ziran (Central Eastern Desert), Gabal El Maesala (Aswan) and three areas from Wadi Allaqi, (Gabal Abu Marw, Gabal Haumor and Gabal um Shalman), in the South Eastern Desert. Granite samples were studied radiologically, petrographically and geochemically. The contents of natural radionuclides 226Ra, 232Th and 40K) were measured in investigated samples by using gamma spectrometry [NaI (Tl) 3'x3']. The activity concentrations of 226Ra, 232Th and 40K in the selected granite samples ranged from 9±0.5 to 111±7, 8±1 to 75±4 and 100±6 to 790±40 Bq kg-1, respectively. The external hazard index (Hex), absorbed dose and annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The calculated radium equivalents were lower than the values recommended for construction materials (370 Bq kg-1). The excess lifetime cancer risks were also calculated. Petrographically, the granites studied are varied in the form of potash-feldspar, quartz, plagioclase, mica and hornblende. The accessory minerals are zircon, apatite and allanite. Geochemically, the chemical composition of the granite is studied especially for major oxides. They are characterized to have SiO2, K2O, Na2O and Al2O3 with depletion in CaO, MgO, TiO2 and P2O5. (authors)

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

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    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

  16. The petrogenesis of metamorphosed carbonatites in the Grenville Province, Ontario

    International Nuclear Information System (INIS)

    Veins and dikes of calcite-rich rocks within the Central Metasedimentary Belt boundary zone (CMBbz) in the Grenville Province of Ontario have been interpreted to be true carbonatites or to be pseudocarbonatites derived from interaction of pegmatite melts and regional Grenville marble. The putative carbonatites have been metamorphosed and consist mainly of calcite, biotite, and apatite with lesser amounts of clinopyroxene, magnetite, allanite, zircon, titanite, cerite, celestite, and barite. The rocks have high P and rare earth element (REE) contents, and calcite in carbonatite has elevated Sr, Fe, and Mn contents relative to Grenville Supergroup marble and marble melange. Values of δ18OSMOW (9.9 - 13.3o/oo) and δ13CPDB (-4.8 to -1.9o/oo) for calcite are also distinct from those for marble and most marble melange. Titanites extracted from clinopyroxene -calcite-scapolite skarns formed by metasomatic interaction of carbonatites and silicate lithologies yield U-Pb ages of 1085 to 1035 Ma. Zircon from one carbonatite body yields a U-Pb age of 1089 ± 5 Ma; zircon ages from two other bodies are 1170 ± 3 and 1143 ± 8 Ma, suggesting several carbonatite formation events or remobilization of carbonatite during deformation and metamorphism around 1080 Ma. Values of εNd(T) are 1.7 - 3.2 for carbonatites, -1.5 -1.0 for REE-rich granite dikes intruding the CMBbz, and 1.6 - 1.7 for marble. The mineralogy and geochemical data are consistent with derivation of the carbonatites from a depleted mantle source. Mixing calculations indicate that interaction of REE-rich pegmatites with regional marbles cannot reproduce selected major and minor element abundance, REE contents, and O and Nd isotope compositions of the carbonatites. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-15

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

  18. Uranium cycle and tectono-metamorphic evolution of the Lufilian Pan-African orogenic belt (Zambia)

    International Nuclear Information System (INIS)

    tectonic accretion in the internal zone of the Lufilian orogenic belt. During these syn-metamorphic fluid-rock interactions, uranium has been leached from U-bearing minerals such as allanite or monazite hosted by the reworked and partially molten gneissic basement. (author)

  19. Varena suite in the crystalline crust of the Southern Lithuania: implication to the genesis and mineralization

    Science.gov (United States)

    Kirkliauskaite, Vaida; Motuza, Gediminas; Skipityte, Raminta

    2016-04-01

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

  20. Geochemistry and mineralogy of the radioactive minerals associated with some pegmatite veins of the Ukma-Nawahatu Hursi sector, Purulia district, 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 min - 26 sec N, 86° 02 min - 04 sec E) in Purulia dist., West Bengal, have association of radioactive minerals in the form of coarse-grained pitchblack lumps and irregular patches. The present author and his associates first reported the occurrence of this radioactive belt along a ENE-WSW shearzone during their fieldwork in November, 1978. Groundborne radiometric survey and isorad mapping has established a radioactive high zone of about 15 km length running through Ukma, Nawahatu and Hursi areas. Mineralogical studies of the radioactive minerals have revealed the occurrence of Chevkinite, Aeschynite, Brannerite, Allanite, Uraninite, Tyuyamunite, Davidite, Euxenite, Samarskite, Thorutite, Autunite, Cerianite, in association with quartz, barite, microcline as the principal minerals and various minor minerals like biotite, vermiculite, hornblende, augite, orthoclase, celsian, muscovite, calcite, epidote, zoisite, ilmenite, sphene, rutile, hematite, magnetite, anatase, galena and sodic plagioclase. 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 the footwall amphibolite and hangingwall garnetiferous schist. The pegmatite veins have followed mainly schistosity of the host rock and dip at 70°-80° towards south. Chemical analyses of individual radioactive minerals by SEM-EDX and also of the bulk radioactive lumps by ICP-MS have shown significant concentration of U, Tb and Rare earths. Minor and trace element analyses also record notable contents of Zr, Ga, Sc, Pb, Zn, Nb, Cu, Ni, V, Cr, As, W, Pd, Ag and TI. Details of chemical analytical data are presented here. Chemically active fluids generated during metamorphism, metasomatism and granitic activity appear to have played a significant role in the

  1. Eruptive history, petrology, and petrogenesis of the Joe Lott Tuff Member of the Mount Belknap Volcanics, Marysvale volcanic field, west-central Utah

    Science.gov (United States)

    Budding, Karin E.

    1982-01-01

    The Joe Lott Tuff Member of the Mount Belknap Volcanics is the largest rhyolitic ash-flow tuff sheet in the Marysvale volcanic field. It was erupted 19 m.y. ago, shortly after the changeover from intermediate-composition calc-alkalic volcanism to bimodal basalt-rhyolite volcanism. Eruption of the tuff resulted in the formation of the Mount Belknap Caldera whose pyroclastic intracaldera stratigraphy parallels that in the outflow facies. The Joe Loft Tuff Member is a composite ash-flow sheet that changes laterally from a simple cooling unit near the source to four distinct cooling units toward the distal end. The lowest of these units is the largest and most widespread; it is 64 m thick and contains a basal vitrophyre. Eruption of the lower unit led to the initial collapse of the caldera. The lower unit is followed upward by a 43 m middle unit, a 26 m pink-colored unit which is separated by a prominent air- fall layer, and a 31 m upper unit. The Joe Loft Tuff Member is an alkali rhyolite with 75.85-77.31 wt. % silica and 8.06-9.32 wt. % K2O+Na2O; the agpaitic index (Na2O+ K2O/Al2O3) is .77-.98. The tuff contains about I% phenocrysts of quartz, sanidine, oligoclase, augite, apatite, zircon, sphene, biotite, and oxidized Fe-Ti oxides. The basal vitrophyre contains accessory allanite, chevkinite, and magnesiohastingsite. The main cooling units are chemically and mineralogically zoned indicating that the magma chamber restratified prior to each major eruption. Within each of the two thickest cooling units, the mineralogy changes systematically upwards; the Or content and relative volume of sanidine decreases and An content of plagioclase increases. The basal vitrophyre of the lower unit has a bulk composition that lies in the thermal trough near the minima of Or-Ab-Q at 1 kb PH2O. Microprobe analyses of feldspar and chemical modeling on experimental systems indicate that pre-eruption temperatures were near 750?C and that the temperature increased during the eruption of

  2. Kimberlite, lamproite, ultramafic lamprophyre, and carbonatite relationships on the Dharwar Craton, India; an example from the Khaderpet pipe, a diamondiferous ultramafic with associated carbonatite intrusion

    Science.gov (United States)

    Smith, C. B.; Haggerty, S. E.; Chatterjee, B.; Beard, A.; Townend, R.

    2013-12-01

    Are kimberlites, lamproites, ultramafic lamprophyres and carbonatites genetically associated or not? There are strong opinions for and against any relationship. The 20 Ha Khaderpet pipe, discovered by Rio Tinto Exploration, is an unusual diamondiferous carbonatite-kimberlite clan rock (KCR) association in the Anumpalle Cluster of the Wajrakarur Kimberlite Field in the Dharwar Craton of Peninsular Indian. The Khaderpet pipe has a discrete sovite phase intrusive into KCR breccia, not noticed elsewhere in the Wajrakarur kimberlite field. Petrographically, the KCR is a clast-supported lithic breccia and crystal lithic tuff, with occasional pelletal lapilli. Clasts show a weak horizontal imbrication. The overall appearance of the tuffs and breccias is suggestive of terminal-blocked, vent accumulations that formed by under pressure, with spallation of country rock causing an abundance of granitoid debris. The sovite phase has up to 95% calcite, occasionally showing flow textured polycrystalline laths set in a minor saponite matrix. There are mineralogical gradations from an olivine-rich ultramafic to a calcite-dominant rock resembling pure carbonatite. Rare REE mineral phases in the carbonatite include allanite and other REE-rich unidentified mineral phases. Xenocrystic high pressure phases in both ultramafic and carbonatite include mantle-derived diamonds, lherzolitic-, eclogitic- and subcalcic-pyrope, Ti-poor andradite, chrome diopside, picrochromite and picroilmenite. Extensive metasomatism in the form of reddening of country rock feldspars by hematite, introduction of green chlorite, and saponitic alteration of breccia clasts and the ultramafic phase is common. The chemistry of the Khaderpet ultramafic component, suggests that the KCR is transitional between kimberlite and ultramafic lamprophyres, like certain other pipes in the Wajrakarur Kimberlite Field, with strong enrichment in LREE, CaO and CO2. However, low MgO (~ 13%) and high CaO (~ 10%) values are more

  3. W-Au skarns in the Neo-Proterozoic Seridó Mobile Belt, Borborema Province in northeastern Brazil: an overview with emphasis on the Bonfim deposit

    Science.gov (United States)

    Souza Neto, João Adauto; Legrand, Jean Michel; Volfinger, Marcel; Pascal, Marie-Lola; Sonnet, Philippe

    2008-02-01

    The Seridó Mobile Belt (SMB) is located in the Borborema Province in northeastern Brazil and consists of a gneiss basement (Archean to Paleo-Proterozoic), a metasedimentary sequence (marble, quartzites, and schists), and the Brasiliano igneous suite (both of Neo-Proterozoic age). In this region, skarns occur within marble and at the marble-schist contact in the metasedimentary sequence. Most of the skarn deposits have been discovered in the early 1940s, and since then, they have been exploited for tungsten and locally gold. Recently, the discovery of gold in the Bonfim tungsten skarn has resulted in a better understanding of the skarn mineralization in this region. The main characteristics of the SMB skarns are that they are dominantly oxidized tungsten skarns, with the exception of the Itajubatiba and Bonfim gold-bearing skarns, which are reduced based on pyrrhotite as the dominant sulfide, garnet with high almandine and spessartine component, and elevated gold contents. In the Bonfim deposit, pressure estimates indicate that the skarns formed at 10- to 15-km depth. The mineralized skarns present the prograde stage with almandine, diopside, anorthite, and actinolite-magnesio-hornblende, and titanite, apatite, allanite, zircon, and monazite as accessory minerals. The retrograde stage is characterized by alkali feldspar, clinozoisite-zoisite-sericite, calcite, and quartz. Scheelite occurs in four ore-shoots distributed within the marble and at the marble-schist contact. The main ore body is 5-120 cm wide and contains an average of 4.8-wt.% WO3, which occurs in the basal marble-schist contact. Fold hinges appear to control the location of high-grade scheelite. The late-stage gold mineralization contains bismite (Bi2O3), fluorine-bearing bismite, native bismuth, bismuthinite (Bi2S3), and joseite [Bi4(Te,S)3], and also chlorite, epidote, prehnite, chalcopyrite, and sphalerite. This gold-bismuth-tellurium mineralization exhibits a typical late character and occurs as a

  4. Hydrothermal Concentration of Zr, Y + HREE in the Lake Zone of the Thor Lake Rare Metal Deposit, Northwest Territories

    Science.gov (United States)

    Sheard, E. R.; Heiligmann, M.; Williams-Jones, A. E.

    2009-05-01

    The Thor Lake rare-metal (Zr, Y, REE, Nb, Ta, Be, Ga) deposit in Northwest Territories contains Canada's largest resource of Zr, Y and HREE and is one of the largest resources of these elements on the planet. Much of the mineralization was clearly concentrated by hydrothermal processes, providing compelling evidence for Zr mobility. Geologically, the deposit is situated at the southern edge of the Slave Province of the Canadian Shield, within the 2150 Ma alkaline to peralkaline Blachford Lake complex consisting of an early suite of gabbro, quartz syenite and granite, which was intruded by the Grace Lake granite and, in turn, by the Thor Lake syenite [1]. A layered alkaline intrusion dominated by nepheline syenite occurs below the Thor Lake syenite and is thought to represent the youngest phase of the complex. This intrusion comprises numerous sub- horizontal layers of sodalite syenite, alkali syenite and lujavrite. Evidence of cumulate and adcumulus textures, cyclic magmatic differentiation and rhythmic layering of mafic and felsic units on scales ranging from tens of centimetres to several metres indicate a complex history of pulsed injection of magma and magmatic differentiation. The upper part of the layered intrusion and the overlying Thor Lake syenite contain the bulk of the rare metal mineralization, with Zr hosted primarily by zircon, Nb primarily by ferrocolumbite and fergusonite, and Y + HREE by fergusonite and zircon. The LREE are hosted by monazite, allanite, bastnaesite and synchisite/parisite. The precursor rocks to the ore were pervasively altered by Fe- and K-rich hydrothermal fluids, which replaced much of the primary mineralogy by magnetite, biotite and K-feldspar and redistributed/concentrated the rare metals including Zr (as secondary zircon). This alteration was overprinted locally by intense sodic alteration. In other rare-metal-rich alkaline complexes such as Strange Lake, Ilimaussaq and Lovozero, the Zr, Nb, Y + REE mineralization has been

  5. Origin of postcollisional intrusions in NW Anatolia, Turkey: Implications for magma chamber processes

    Science.gov (United States)

    Aysal, Namık

    2013-04-01

    Post-collisional magmatic activities of NW Anatolia are represented by a series of granitic intrusions and volcanic successions in the Biga Peninsula, NW Turkey. These plutonic rocks have distinct textures, chemical compositions and Sr-Nd isotope characteristics. They consist of coarse grained, equigranular and/or hypidiomorphic textured granite, gronodiorite, monzogranite, quartz-monzonite, pyroxene-monzonite and leucocratic alkali feldspar granites. These intrusions are composed of quartz, K-feldspar, plagioclase, hornblende, pyroxene and biotite. However, leucocratic facies rocks contain tourmaline with minor amount of mafic minerals. Accessory phases are represented by zircon, apatite, monozite, magnetite, sphene and rarely allanite. ASI values of the plutonic rocks vary between 0.7 and 1.24. These intrusive rocks are therefore classified as metaluminous-peraluminous with I-type affinity. K2O contents show that the intrusive rock samples show calc-alkaline, high K-calc-alkaline and shoshonitic character. Initial 87Sr/86Sr(t) (0.69980-0.70835), 143Nd/144Nd(t) (0.51238-0.51247) isotope ratios and negative ɛNd(t) (-4.4 - -2.6) values imply that these intrusive rocks could have been derived from enriched mantle sources. N-MORB normalized spidergrams of NW Anatolian plutonic rocks display enrichments in large ion lithophile elements (LILE), light rare earth elements (LREE) and depletion in high field strength elements (HFSE) indicating hydrous melting of a mantle wedge in a subduction zone and/or enrichment of the mantle source with an inherited subduction component from an ancient arc magmatism. Chondrite-normalized Rare Earth Element spidergrams are indicative of the importance of plagioclase and amphibole fractionation. On tectonic discrimination diagrams, all granite samples fall into the volcanic arc granite, syn and post-collisional granite fields. The geochemical data also indicate that a number of magma chamber processes involving magma mixing, fractional

  6. To the origin of Icelandic rhyolites: insights from partially melted leucocratic xenoliths

    Science.gov (United States)

    Gurenko, Andrey A.; Bindeman, Ilya N.; Sigurdsson, Ingvar A.

    2015-05-01

    We have studied glass-bearing leucocratic (granitic to Qz-monzonitic) crustal xenoliths from the Tindfjöll Pleistocene volcanic complex, SW Iceland. The xenoliths consist of strongly resorbed relicts of anorthitic plagioclase, K-rich feldspar and rounded quartz in colorless through pale to dark-brown interstitial glass. Spongy clinopyroxene and/or rounded or elongated crystals of orthopyroxene are in subordinate amount. Magnetite, ilmenite, zircon, apatite, allanite and/or chevkinite are accessory minerals. The xenoliths more likely are relicts of earlier-formed, partially melted Si-rich rocks or quartz-feldspar-rich crystal segregations, which suffered latter interaction with hotter and more primitive magma(s). Icelandic lavas are typically low in δ 18O compared to mantle-derived, "MORB"-like rocks (~5.6 ± 0.2 ‰), likely due to their interaction with, or contamination by, the upper-crustal rocks affected by rain and glacial melt waters. Surprisingly, many quartz and feldspar crystals and associated colorless to light-colored interstitial glasses of the studied xenoliths are not low but high in δ 18O (5.1-7.2 ‰, excluding three dark-brown glasses of 4-5 ‰). The xenoliths contain abundant, low- to high- δ 18O (2.4-6.3 ‰) young zircons (U-Pb age 0.2-0.27 ± 0.03 Ma; U-Th age 0.16 ± 0.07 Ma), most of them in oxygen isotope equilibrium with interstitial glasses. The δ 18O values >5.6 ‰ recorded in the coexisting zircon, quartz, feldspar and colorless interstitial glass suggest crystallization from melts produced by fusion of crustal rocks altered by seawater, also reflecting multiple melting and crystallization events. This suggests that "normal"- δ 18O silicic magmas may not be ultimately produced by crystallization of mafic, basaltic magmas. Instead, our new single-crystal laser fluorination and ion microprobe O-isotope data suggest addition of diverse partial crustal melts, probably originated from variously altered and preconditioned crust.

  7. Los granitos peraluminosos de las Sierras de Vinquis, Cerro Negro y Zapata (Sierras Pampeanas, provincia de Catamarca, Argentina

    Directory of Open Access Journals (Sweden)

    Medina, M. E.

    1992-12-01

    Full Text Available The studied plutons are close to several batholiths of this region, as Sierra de Mazán and other, but with some mineralogical peculiarities. The magmatic cordierite, common in proximate places, is scarce, as sillimanite, while the andalusite is very rare, with few tourmaline. Fluorite and allanite are also typical accasories only in the granites of the Sierra de Zapata. All plutons are peraluminous of potassic tendency, with cortical affinity.The interpretation of the geochemical values distinguishes between granites of different maturity, emplaced under a predominant influence of active margin for Cerro Negro and Vinquis, while the batholith of Zapata has, below these concepts, a marked feature of within plate.The mineralogical associations suggest that the granites of Cerro Negro and Vinquis were emplaced to pressures of 2 kb or less and temperature of 650º C, while the granites of Zapata had done under conditions of lesser pressure, between 1.5 and 2.0 kb and lower temperature, 600-650º C.A grandes rasgos, los plutones estudiados tienen semejanzas con otros del entorno regional, tal como los de la Sierra de Mazán, pero con peculiaridades mineralógicas. La cordierita magmática, que en lugares próximos es muy abundante, es aquí escasa, al igual que la sillimanita, mientras que la andalucita es muy rara y la turmalina poco frecuente. La fluorita y allanita son accesorios comunes y de cierta abundancia sólo en los granitos de la Sierra de Zapata.Todos los plutones son peralumínicos y de tendencia potásica, con neta afinidad cortical. El estudio estadístico de datos geoquímicos seleccionados, permite diferenciar agrupaciones que tienen un reflejo satisfactorio en los plutones caracterizados, por encima de las variaciones de facies. La interpretación de los valores geoquímicos distingue granitos de desigual madurez, emplazados bajo una influencia predominante de margen activo o intraplaca de características continentales, en

  8. Petrological, geochemical and isotopic investigations on a carbonate-dyke and enclosed pyroxenite xenoliths from Val Mastallone (Ivrea-Verbano Zone): evidence of a cumulate carbonatite in the lower crust?

    Science.gov (United States)

    Galli, Andrea; Grassi, Daniele; Burg, Jean-Pierre; Schwab, Leo; Rickli, Jörg; Gianola, Omar

    2016-04-01

    The Ivrea-Verbano Zone (Italy/Switzerland) represents one of the best exposed mantle-crust sections worldwide. Its geological evolution has been governed by the Permian underplating of mantle-derived basic magmas („Mafic Complex") into the high-grade basement of the Southern Alps. In the Ivrea-Verbano Zone, marbles occur as concordant bodies or partly discordant carbonate-dykes. Generally, these dykes are constituted of calcite, diopside, scapolite, contain enclave of the host rocks and display sharp contacts to the host lithologies without evidences of alteration zones. In Val Mastallone, an up to 40 m thick carbonate-dyke with different characteristics occurs within mafic granulites. This dyke is composed of calcite, clinopyroxene and subordinate allanite and zircon. No scapolite is observed. The contacts to the host granulites are characterized by alteration zones composed of actinolite, chlorite, clinozoisite, plagioclase and calcite. The carbonate-dyke bears enclave of phlogopite-amphibole-apatite-rutile-ilmenite ± garnet or spinel clinopyroxenites. These rock type is not outcropping elsewhere in the proximity of the dyke, suggesting a significant transport. Host mafic granulite enclave are found exclusively at the margin of the dyke. Calcite dykelets rich in zircon, baddeleyite and other Ba, U, Th, REE-rich phases cut across the enclave. The carbonate-dyke shows an enrichment of LREE over HREE ((La/Yb)N = 14), with a Σ REE = 338 and Y/Ho = 27. On the chondrite-normalized REE abundances diagram, no Eu anomaly is observed. Mantle-normalized pattern shows strong negative anomalies at Cs, Rb, K, Pb, P, Zr, Hf, Ti and positive Ba, Th, Sr, Nd anomalies, similarly to the "world average carbonatites". Measured absolute trace element concentrations are lower than average carbonatites but significantly higher than typical limestones and similar to cumulate carbonatites found elsewhere in the world (e.g. India, China, Brazil). Grt-bearing clinopyroxenite enclave

  9. 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

  10. REE potential of the Nordkinn Peninsula, North Norway: A comparison of soil and bedrock composition

    International Nuclear Information System (INIS)

    Highlights: • Soil geochemistry outlines an extensive REE anomaly on the Nordkinn Peninsula, North Norway. • Soil and bedrock geochemistry are compared with respect to REE and other HFSE. • Petrology of soil and rock samples reveals that the economic potential is limited. • Poor condition of REE minerals causes elevated REE concentrations in AR-digested soil samples. - Abstract: Regional-scale, low-density sampling, geochemical surveys using a variety of different sample materials have repeatedly indicated the Nordkinn Peninsula (northern Norway) as a substantial rare earth element (REE) anomaly. Recently, a more detailed soil geochemical survey, covering about 2000 km2 at a sample density of 1 site per 2 km2, was carried out in the area. The new geochemical survey outlined a large area (several hundred km2) where the soil samples contained several hundred and up to over 2000 mg/kg aqua regia extractable REE. In the surroundings of the highest soil anomalies, bedrock samples were collected for a mineralogical and compositional characterisation of the metasedimentary bedrock with focus on the possible economic potential. The REE concentrations obtained for aliquots of bedrock following aqua regia extraction, 4-Acid digestion and Li-borate fusion/decomposition closely match the results from soil pulps after an aqua regia extraction. Total contents for the REE determined in bedrock using the above methods range between 19 and 429 mg/kg, indicating an overall limited economic REE potential and the predominance of the light REE over the heavy REE. In terms of petrography, essentially all the bedrock samples are characterised by the presence of detrital, altered and locally even decomposed allanite (a LREE-incorporating, epidote-group mineral) and minor xenotime (a HREE-incorporating phosphate) while texturally stable REE phases are scarce. It is the poor condition of the REE minerals that makes them prone towards acidic leaching and, given similar results for

  11. 华阳川铀多金属矿床碳酸岩脉矿化特征%Mineralization Characteristic of Carbonatite Veins in Huayangchuan U-polymetal Deposit,Shanxi Province

    Institute of Scientific and Technical Information of China (English)

    惠小朝; 何升

    2016-01-01

    Huayangchuan U-polymetal deposit is quite unique in Xiaoqinling metallogenetic belt,the frac-trure in the carbonatite vein is an important storing space for the deposit. Carbonatite extensively distrib-ute in deposit and intruded into metamorphic rock,pegmatite as vein and stockwork vein along NW-tren-ding tensional fracture,tensional-shear fracture and the subsidiary crack. The gangue mineral in mineral-ized vein carbonatite is mainly calcite and some hornblende,quartz,magnetite,K-feldspar and the ore minerals include betafite,monazite,allanite,barite and celestine. Betafite is the main uranium mineral, the average contents of U,Nb,Ba,Sr,REE are respectively 2554.20×10 6 ,1836.80×10 6 ,4145.78 ×10 6 ,4412.80×10 6 ,7348.44×10 6 which can be comprehensive utilized.%华阳川铀多金属矿床是小秦岭成矿带中成矿特征最为独特的矿床,其碳酸岩脉破碎带是重要的成矿空间.区内碳酸岩分布很广泛,沿 NW 向张性和张扭性断裂及其伴生的次级裂隙充填,呈单脉状和网脉状穿插于变质岩、伟晶岩中.矿化碳酸岩脉中,脉石矿物大部分为方解石,少量为角闪石、石英、磁铁矿、碱性长石等;矿石矿物为铌钛铀矿、独居石、褐帘石、重晶石、天青石.铌钛铀矿是最主要的赋铀矿物,矿化元素铀、铌、钡、锶、稀土等平均含量分别为2554.20×106、1836.80×106、4145.78×106、4412.80×106、7348.44×106,可以综合开发利用.

  12. Geology, petrology and U-Pb geochronology of Serra da Rajada Granitic Pluton: implications about ediacaran magmatic evolution in NE portion of the Rio Piranhas-Serido Domain (NE of Borborema Province)

    International Nuclear Information System (INIS)

    The Ediacaran plutonic activity, related to the Brazilian/Pan-African orogeny, is one of the most important geological features in the Borborema Province, formed by batholiths, stocks and dikes. The Serra da Rajada Granitic Pluton (SRGP), located in the central portion of the Rio Piranhas-Serido Domain, is an example of these bodies. This site is the target of cartographic, petrographic, lithochemical and geochronological studies. Its rocks are described as monzogranites consisting of K-feldspar, plagioclase (oligoclase-An23-24%), quartz and biotite (main mafic), having as accessory minerals opaque, titanite, allanite, apatite and zircon. Chlorite, white mica and carbonate are alteration minerals. Lithochemical data from 15 samples show quite evolved rocks (SiO2 , 69% to 75%), rich in alkalis (Na2O + K2O ≥ 8.0%), depleted in MgO (≤ 0.45%), CaO (≤ 1.42%) and TiO2 (≤ 0.36%), and displaying moderate levels of Fe2O3 t (2.16 to 3.53%). These rocks present a transitional nature between metaluminous and peraluminous (predominance of the latter) and have subalkaline/monzonitic affinity (high-K Calc-alkaline). Harker diagrams represent negative correlations in Fe2O3t, MgO and CaO, indicating fractionation of mafic and plagioclase. The REE spectrum show enrichment of light in relation to heavy REE (LaN/YbN = 23.70 to 10.13), with negative anomaly in Eu (Eu/ Eu* = 0.70 to 10.13) suggesting fractionation or accumulation in the feldspars source (plagioclase). Data integration allows correlating the SRGP rocks with those described as Equigranular high-K Calc-alkaline Suite. The U-Pb geochronology and Sm-Nd isotope dating indicate that the biotite monzogranite have a crystallization age of 557 ± 13 Ma and TDM model age of 2.36 Ga, respectively, and εNd value of - 20.10 for the crystallization age, allowing to infer a crustal source for the magma generated in the Paleoproterozoic age. (author)

  13. Impact of volcanism on the evolution of Lake Van (eastern Anatolia) III: Periodic (Nemrut) vs. episodic (Süphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka

    Science.gov (United States)

    Schmincke, Hans-Ulrich; Sumita, Mari

    2014-09-01

    Fifteen Lateglacial to Holocene rhyolitic, dominantly primary tephra layers piston-cored and drilled (ICDP Paleovan drilling project) in western Lake Van (eastern Anatolia, Turkey) were precisely correlated to either of the two adjacent and active large volcanoes Nemrut and Süphan based on shard textures, mineralogy and mineral and glass compositions. The young peralkaline (comenditic to pantelleritic) primary rhyolitic Nemrut tephras are characterized by anorthoclase, hedenbergitic to augitic clinopyroxene, fayalitic olivine, minor quartz, and rare accessory chevkinite and zircon. Phenocrysts in subalkaline primary rhyolitic Süphan tephras are chiefly oligoclase-labradorite, with minor K-rich sanidine in some, biotite, amphibole, hypersthene, rare augitic clinopyroxene, relatively common allanite and rare zircon. Two contrasting explosive eruptive modes are distinguished from each other: episodic (Süphan) and periodic (Nemrut). The Lateglacial Süphan tephra swarm covers a short time interval of ca. 338 years between ca. 13,078 vy BP and 12,740 vy BP, eruptions having occurred statistically every ca. 42 years with especially short intervals between V-11 (reworked) and V-14. Causes for the strongly episodic Süphan explosive behavior might include seismic triggering of a volcano-magma system unable to erupt explosively without the benefit of external triggering, as reflected in pervasive faulting preceding the Süphan tephra swarm. Seismic triggering may have caused the rise of more mafic ("trachyandesitic") parent magma, heating near-surface pockets of highly evolved magma - that might have formed silicic domes during this stage of volcano evolution - resulting in ascent and finally explosive fragmentation of magma essentially by external factors, probably significantly enhanced by magma-water/ice interaction. Explosive eruptions of the Nemrut volcano system, interpreted to be underlain by a large fractionating magma reservoir, follow a more periodic mode of (a

  14. Microstructural observation and chemical dating on monazite from the Shilu Group, Hainan Province of South China: Implications for origin and evolution of the Shilu Fe-Co-Cu ore district

    Science.gov (United States)

    Xu, Deru; Kusiak, Monika A.; Wang, Zhilin; Chen, Huayong; Bakun-Czubarow, Nonna; Wu, Chuanjun; Konečný, Patrik; Hollings, Peter

    2015-02-01

    New monazite chemical U-Th-total-Pb (CHIME) ages, combined with microstructural observations, mineral compositions, and whole-rock geochemistry, indicate that the large-scale, banded iron formation (BIF)-type Shilu Fe-Co-Cu ore district in Hainan Province, South China is a multistage product of sedimentation, metamorphism, and hydrothermal-metasomatic alteration associated with multiple orogenies. Two types of monazite, i.e. "polygenetic" and "metamorphic", were identified. The "polygenetic monazite" comprises a magmatic and/or metamorphic core surrounded by a metamorphic rim, and shows complex zoning. Breakdown corona structure, with a core of monazite surrounded by a mantle of fluorapatite, allanite, and/or epidote as concentric growth rings, is commonly observed. This type of monazite yielded three main CHIME-age peaks at ca. 980 Ma, ca. 880 Ma and ca. 450 Ma. The ages which range up to ca. 880 Ma for detrital cores, record a pre-deformational magmatic and/or metamorphic event(s), and is considered to be the depositional time-interval of the Shilu Group and interbedded BIFs in a marine, back-arc foreland basin likely due to the Grenvillian or South China Sibao orogeny. After deposition, the Shilu district was subjected to an orogenic event, which is recorded by the syndeformational metamorphic monazite with ca. 560-450 Ma population. Probably this event not only caused amphibolite facies metamorphism and associated regional foliation S1 but also enriched the original BIFs, and most likely corresponds to the "Pan-African" and/or the South China Caledonian orogeny. The post-deformational "metamorphic" monazite occurs mostly as inclusions in garnet and shows ca. 260 Ma age. It likely represents the Late Permian post-magmatic hydrothermal and related retrograde event(s) initiated by the Indosinian orogeny due to the closure of the Paleo-Tethys. The breakdown of monazite to secondary coronal mineral phases as well as the Fe-remobilization and associated skarnization

  15. Epidote-Bearing Veins in the State 2-14 Drill Hole: Implications for Hydrothermal Fluid Composition

    Science.gov (United States)

    Caruso, L. J.; Bird, D. K.; Cho, M.; Liou, J. G.

    1988-11-01

    Epidote-bearing veins in State 2-14 drill core from 900 to 2960 m depth were examined using backscattered electron microscopy and electron probe microanalysis to characterize the mineralogy, parageneses, texture, and composition of vein minerals. In order of decreasing abundance, minerals in epidote-bearing veins are pyrite, calcite, K-feldspar, quartz, anhydrite, hematite, chlorite, Fe-Cu-Zn sulfides, actinolite, titanite, and allanite. The downhole distribution of minerals in epidote-bearing veins (+ pyrite and quartz) varies as a function of depth and includes: (1) calcite above ˜2000 m, (2) K-feldspar between 1700 and 2745 m, (3) anhydrite between 2195 and 2745 m, (4) hematite ± sulfides above 2773 m, and (5) actinolite below ˜2890 m. Where present, K-feldspar was the first mineral to precipitate in veins followed by epidote. In all other veins, epidote was the earliest vein mineral to form. Calcite, quartz, anhydrite, hematite, and sulfides were paragenetically later. Compositional zoning, common in most vein epidotes, is typically symmetric with Al-rich cores and Fe3+ -rich rims. The minimum mole fraction of Ca2Fe3Si3O12(OH) (XPs) in vein epidotes decreases systematically with increasing depth from ˜0.33 at 906 m to ˜0.21 at 2900 m, and the maximum XPs at any given depth is greater than 0.33. Thermodynamic analyses of phase relations among vein-filling minerals and aqueous solutions at depths near 1867 m and 300°C indicate that the modern reservoir fluid in the Salton Sea geothermal system is in equilibrium with calcite + hematite + quartz + epidote (XPs = 0.33) ± anhydrite. The predicted fugacity of CO2 (˜14 bars) for the modern Salton Sea brine is in close agreement with the calculated value of fCO2 for the 1867 m production fluid. Theoretical phase diagrams in the system CaO-K2O-Fe2O3-Al2O3-SiO2-H2O-O2-S2-CO2 demonstrate that the mineralogies and mineral parageneses recorded hi epidote-bearing veins and the observed variations in Al-Fe3+ content of

  16. Genesis of jadeite-quartz rocks in the Yorii area of the Kanto Mountains, Japan

    Science.gov (United States)

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

    2013-02-01

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

  17. 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

  18. Geology, petrology and U-Pb geochronology of Serra da Rajada Granitic Pluton: implications about ediacaran magmatic evolution in NE portion of the Rio Piranhas-Serido Domain (NE of Borborema Province); Geologia, petrologia e geocronologia U-Pb do Pluton Granitico Serra da Rajada: implicacoes sobre a evolucao magmatica ediacarana na porcao do Dominio Rio Piranhas-Serido (NE da Provincia Borborema)

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Alan Pereira da; Dantas, Alexandre Ranier, E-mail: alan.costa@cprm.gov.br, E-mail: alexandre.dantas@cprm.gov.br [Servico Geologico do Brasil (CPRM), Natal, RN (Brazil). Nucleo de Apoio de Natal/Superintendencia Regional de Recife; Nascimento, Marcos Antonio Leite do; Galindo, Antonio Carlos, E-mail: marcos@geologia.ufrn.br, E-mail: galindo@geologia.ufrn.br [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Departamento de Geologia

    2015-12-15

    The Ediacaran plutonic activity, related to the Brazilian/Pan-African orogeny, is one of the most important geological features in the Borborema Province, formed by batholiths, stocks and dikes. The Serra da Rajada Granitic Pluton (SRGP), located in the central portion of the Rio Piranhas-Serido Domain, is an example of these bodies. This site is the target of cartographic, petrographic, lithochemical and geochronological studies. Its rocks are described as monzogranites consisting of K-feldspar, plagioclase (oligoclase-An{sub 23-24%}), quartz and biotite (main mafic), having as accessory minerals opaque, titanite, allanite, apatite and zircon. Chlorite, white mica and carbonate are alteration minerals. Lithochemical data from 15 samples show quite evolved rocks (SiO{sub 2} , 69% to 75%), rich in alkalis (Na{sub 2}O + K{sub 2}O ≥ 8.0%), depleted in MgO (≤ 0.45%), CaO (≤ 1.42%) and TiO{sub 2} (≤ 0.36%), and displaying moderate levels of Fe{sub 2}O{sub 3} t (2.16 to 3.53%). These rocks present a transitional nature between metaluminous and peraluminous (predominance of the latter) and have subalkaline/monzonitic affinity (high-K Calc-alkaline). Harker diagrams represent negative correlations in Fe{sub 2}O{sub 3}t, MgO and CaO, indicating fractionation of mafic and plagioclase. The REE spectrum show enrichment of light in relation to heavy REE (LaN/YbN = 23.70 to 10.13), with negative anomaly in Eu (Eu/ Eu* = 0.70 to 10.13) suggesting fractionation or accumulation in the feldspars source (plagioclase). Data integration allows correlating the SRGP rocks with those described as Equigranular high-K Calc-alkaline Suite. The U-Pb geochronology and Sm-Nd isotope dating indicate that the biotite monzogranite have a crystallization age of 557 ± 13 Ma and TDM model age of 2.36 Ga, respectively, and ε{sub Nd} value of - 20.10 for the crystallization age, allowing to infer a crustal source for the magma generated in the Paleoproterozoic age. (author)

  19. Environmental review of the Mary Kathleen uranium minesite, Northwest Queensland

    International Nuclear Information System (INIS)

    Full text: The Mary Kathleen uranium deposit, in northwest Queensland, was discovered in 1954 and mined in 19561963 and 1976-1982. Rehabilitation of the site was completed in 1985 and the work won an award for environmental excellence. In 1999 gamma-ray data, plus stream sediment, soil, rock chip, mineral efflorescence, vegetation and water samples were collected from selected sites to assist in the examination of the current environmental status of the rehabilitated area. This paper presents preliminary results and interpretations. In the Mark Kathleen open pit, skarn type U-Th-REE mineralisation is hosted in amphibolite grade metamorphosed calc-silicate, mafic to intermediate igneous and sedimentary rocks. Remnant ore zones are composed of medium to coarse grained garnet and clinopyroxene, with accessory allanite, plagioclase, pyrrhotite, chalcopyrite and uraninite. Later retrograde alteration to chlorite, calcite, sericite, epidote and scapolite occurs. Fine grained uraninite is enclosed in allanite, and is partly replaced by metamict products nd traces of galena. Elevated gamma-ray readings in the open pit correspond to exposed ore lenses, the former haul road and abandoned ore stockpiles (up to 16 mSv/year). Surficial oxidation of ore and adjacent sulphide-bearing calc-silicate rocks has led to contemporary precipitation of yellow, orange, green and white mineral efflorescences on the pit walls. Wallrock oxidation of reactive sulphides (mainly pyrrhotite breakdown) produces acidic solutions, however, buffering reactions of these fluids with gangue calc-silicates and carbonate phases prevent low pH conditions from developing. The open pit lake is approximately 40m deep and contains saline (0.15%) surface waters which are Ca-, SO4-rich with elevated Cu, Fe, Mn, Ni, U and Zn at a pH of 6.11. Waste rock piles are up to 30m thick and have been covered by a thin veneer of benign waste. However, there are high radiation levels on several waste rock piles (up to 20 m

  20. Fluid source and pressure temperature conditions of high-salinity fluids in syn-tectonic veins from the Northeastern Apuan Alps (Northern Apennines, Italy)

    Science.gov (United States)

    Montomoli, Chiara; Ruggieri, Giovanni; Carosi, Rodolfo; Dini, Andrea; Genovesi, Marianna

    Structural studies on syn-tectonic veins cropping out in the northeastern sector of the Apuan Alps metamorphic complex (Northern Apennines, Italy) revealed two sets of veins: (1) type A fibrous veins within the “Scisti sericitici Formation”, related to a late-D1 tectonic phase; (2) B-veins, within the “Diaspri Formation” that developed between late-D1 and D2 tectonic phases. The mineralogy of the A (quartz, chlorite, hematite with minor amounts of apatite, allanite-(Ce), thorite and synchysite) and B-veins (quartz only) reflects the mineralogical composition of the host-rocks: quartz, chlorite, white mica and accessory minerals (apatite, zircon, titanite) occur in the “Scisti sericitici Formation”, while quartz is the main phase in the “Diaspri Formation”. The study of fluid inclusions trapped in quartz crystals of the syn-tectonic veins shows that the inclusions are always oversaturated in NaCl at room temperature and their salinities range from 29.5 to 37 wt.% NaCl equiv. The isochore of the earliest trapped fluid inclusions (type IA; primary inclusions in fiber quartz of A veins), coupled with mineralogical geothermometric data, constrains the pressure-temperature conditions to around 325-300 MPa and 370-380 °C during the late-D1 phase. Subsequent trapping of inclusion types IIA, IIB, IIIA, IIIB and VB in the two vein sets probably occurred during a pressure-temperature decrease (down to 220-245 MPa and 260-270 °C) at a lithostatic thermal gradient of 30 °C/km. Type IVB inclusions, on the other hand, were probably trapped at lower pressure (between lithostatic and hydrostatic conditions) during a transient pressure drop resulting from fault-valve action. SEM/EDS analyses on salts precipitated within opened inclusions confirmed the NaCl-rich compositions of the trapped fluids and also revealed the presence of minor amounts of Ca, K and Mn in the salts. A fluid circulation model, based on mineralogical and fluid inclusion data, was proposed for

  1. Adakitic magmatism in post-collisional setting: An example from the Early-Middle Eocene Magmatic Belt in Southern Bulgaria and Northern Greece

    Science.gov (United States)

    Marchev, Peter; Georgiev, Stoyan; Raicheva, Raya; Peytcheva, Irena; von Quadt, Albrecht; Ovtcharova, Maria; Bonev, Nikolay

    2013-11-01

    Post-collisional (56.0-40.4 Ma) adakitic magmatism in the Rhodope Massif and the Kraishte region, including W. Srednogorie, in South Bulgaria followed the collision of the Rhodope and Pelagonian Massifs. It forms a 250 km NW trending belt which continues into the 1000 km long belt of Eocene magmatism in northern Turkey and Iran. The rocks are represented by felsic subvolcanic dykes and sills in the Kraishte and plutons in the Rhodopes. Here, we synthesize new chemical (whole-rock major and trace elements, and Sr and Nd isotopes) and LA-ICP/MS mineral and U-Pb zircon age data along with published similar data in order to constrain the genesis of this magmatism and the early Cenozoic geodynamic evolution of the central Balkan Peninsula. The rocks display typical subduction-related characteristics with enrichment in LILE and LREE and depletion in HFSE (Nb, Ta and Ti). In the Kraishte and western Srednogorie Zones these are calc-alkaline to high-K calc-alkaline rhyolites, displaying a typical adakitic signature, i.e. high La/Yb and Sr/Y ratios. The studied Rhodope Massif rocks are predominantly high-K calc-alkaline and subordinate calc-alkaline granites and granodiorites with a minor amount of tonalites. Petrographically, they are H2O- and accessory-rich (allanite, epidote, titanite, apatite) rocks, showing geochemical affinities from non-adakitic tonalites and mafic granodiorites to adakitic granodiorites and granites. Similarity of Sr and Nd isotopic compositions of the Kraishte subvolcanic and Rhodope intrusive adakitic rocks with the neighboring and coeval NW Anatolian basaltic to dacitic volcanics and plutons suggests that the most likely source for the South Bulgarian adakitic rocks is the subduction-enriched depleted lithospheric mantle. The nearby and contemporaneous East Serbian alkaline basalts are isotopically and compositionally different and, probably, originate from an OIB-like mantle source. Subsequent fractionation within an isotopically similar lower

  2. Rare earth element mineralogy and geochemistry in a laterite profile from Madagascar

    International Nuclear Information System (INIS)

    Highlights: • Secondary REE-mineralogy depend on redox conditions inside a laterite. • Detailed mineralogy in different layers of a laterite is given. • A Gd-sulfate is described. • Change in bulk rock chemistry control REE mineralogy. - Abstract: In this study, rare earth element (REE) distribution has been investigated in a weathering profile from central Madagascar. Combination of bulk rock geochemical data (elements and isotopes) with mineral characterization reveals a remarkable evolution of the REE abundances and REE-minerals in the vertical weathering profile. In the fresh tonalite (bedrock), REE + Y concentrations are typical of granitoids (299–363 ppm) and the main REE-minerals are allanite and chevkinite. In the C-horizon (saprolite), primary REE-minerals disappear and REEs are transported via fluid to precipitate rhabdophane group minerals in cracks and pores. The presence of sulfate ligands, produced by sulfide oxidation, may be responsible for the REE speciation, as suggested by the composition of the secondary REE-minerals. Rhabdophane group minerals contain up to 9 wt% SO3 and 7 wt% CaO, indicating a mixture between rhabdophane sensu stricto, (REE)PO4·H2O, and tristamite, (Ca,U,Fe(III))(PO4,SO4)·2H2O. Due to intense Ca-leaching, rhabdophane disappears and Al-phosphates (alunite–jarosite group) are found in the soil. Cerianite (Ce(IV)O2) also precipitates in the B-horizon of the soil. Mass transfer calculations based on immobile Ti indicate significant REE leaching in A-horizon with preferential leaching of the heavy REE. REEs accumulate partly in the B-horizon. The uniform Nd isotope compositions and the constant proportion of immobile elements do not reveal external input. In the B-horizon, total REE + Y reach 2194 ppm with high Ce concentrations (1638 ppm; 9*Cebedrock) compared to other REE (3–4*REEbedrock). Tetravalent Ce state is dominant in the B-horizon and requires oxidizing conditions that likely account for the accumulation

  3. Geochemical, zircon U-Pb dating and Sr-Nd-Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China

    Science.gov (United States)

    Yang, Shui-Yuan; Jiang, Shao-Yong; Jiang, Yao-Hui; Zhao, Kui-Dong; Fan, Hong-Hai

    2011-01-01

    , may indicate involvement of a subordinate younger mantle-derived magma in its origin. Geochemical data indicate that the various rocks show variable REE patterns and negative anomalies of Ba, Nb, Sr, P, Eu and Ti in the trace element spidergrams, suggesting that these rocks may have undergone advanced fractional crystallization with separation of plagioclase, K-feldspar and accessory minerals such as allanite. We suggest that this Cretaceous volcanic-intrusive complex formed in an extensional environment, and the formation of the Xiangshan mafic microgranular enclaves can be explained by the injection of mafic magma from a deeper seated mantle magma chamber into a hypabyssal felsic magma chamber at the crustal emplacement levels.

  4. 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

    (Au/Ag >10) forms hematite-stained sericite-dolomite-albite lodes in stacked D2 reverse faults, which offset skarn, syenite, and the biotite-calcite veins by up to 25 m. The molybdenite Re-Os age (2,661 ± 10 Ma) of the ore suggests a genetic link to intrusive activity but is in apparent conflict with a monazite-xenotime U-Pb age (2,651 ± 6 Ma), which differs from that of the skarn at the 95% confidence level. The time relationships at both gold deposits are inconsistent with orogenic models invoking a principal role for metamorphic fluids released during the main phase of compression in the fold belt. Instead, mineralization is related in space and time to late-orogenic, magnetite-series, high-Mg monzodiorite-syenite intrusions of mantle origin, characterized by Mg/(Mg + FeTOTAL) = 0.31-0.57, high Cr (34-96 ppm), Ni (22-63 ppm), Ba (1,056-2,321 ppm), Sr (1,268-2,457 ppm), Th (15-36 ppm), and rare earth elements (total REE: 343-523 ppm). At Wallaby, shared Ca-K-CO2 metasomatism and Th-REE enrichment (in allanite) link Au-Ag mineralization in biotite-calcite veins to the formation of the giant epidote skarn, implicating a Th + REE-rich syenite pluton at depth as the source of the oxidized hydrothermal fluid. At Granny Smith, lead isotope data and the Rb-Th-U signature of early hematite-bearing wall-rock alteration point to fluid released by the source pluton of the differentiated alkali granite dikes.

  5. Eocene magmatic processes and crustal thickening in southern Tibet: Insights from strongly fractionated ca. 43 Ma granites in the western Gangdese Batholith

    Science.gov (United States)

    Wang, Qing; Zhu, Di-Cheng; Cawood, Peter A.; Zhao, Zhi-Dan; Liu, Sheng-Ao; Chung, Sun-Lin; Zhang, Liang-Liang; Liu, Dong; Zheng, Yuan-Chuan; Dai, Jin-Gen

    2015-12-01

    This study reports zircon U-Pb age and Hf isotope, whole-rock major and trace element, and Sr-Nd-Pb-Hf isotope data for the Dajia pluton, western Gangdese Batholith, in southern Tibet. These data indicate that the pluton consists of moderately (Group 1) and strongly (Group 2) fractionated granites that were emplaced synchronously at ca. 43 Ma. Group 1 samples have SiO2 contents of 69-72 wt.% and vary in terms of the differentiation index (DI = 84-93). These rocks are depleted in Ba, Nb, Sr, P, and Ti, with moderate negative Eu anomalies, and display low heavy rare earth elements (HREEs) and Y abundances. Group 2 samples are characterized by high SiO2 (75-78 wt.%) and DI (95-97); significantly negative Eu anomalies; marked concave-upward middle REE (Gd-Ho) patterns; and Ba, Sr, P, and Ti anomalies that are significantly more negative than those of Group 1 samples. Group 1 samples have whole-rock εNd(t) (- 5.9 to - 6.0), εHf(t) (- 4.0 to - 4.5), and zircon εHf(t) (- 6.0 to + 5.8) values identical to those of Group 2 samples [εNd(t) = - 5.7 to - 6.7, εHf(t) = - 3.5 to - 2.9, and zircon εHf(t) = - 2.0 to + 4.2], as well as similar initial Pb isotopic compositions. These data indicate that the two groups were derived from a common source region with garnet as a residual mineral phase. Group 1 samples were most likely derived from partial melting of garnet-bearing amphibolite (rather than eclogite) within the juvenile southern Lhasa crust and mixed with the enriched components from the subducting ancient Indian continental crust and/or the ancient central Lhasa basement. Group 2 samples are interpreted as the products of extensive fractional crystallization (plagioclase, K-feldspar, biotite, apatite, allanite, titanite, monazite, and ilmenite) of the melts represented by Group 1 samples. Low HREEs and Y abundances of the Dajia pluton, together with the presence of strongly fractionated granites (Group 2) identified for the first time in the Gangdese Batholith

  6. Gneiss wastes as secondary raw material for the ceramic industry: an example from the Verbano Cusio Ossola district (Piedmont, north-western Alps, Italy)

    Science.gov (United States)

    Cavallo, Alessandro

    2015-04-01

    The Verbano Cusio Ossola province (VCO, Piedmont, north-western Italy) is one of the most important Italian quarrying districts, due to the peculiarity and variety of its exploited rock types, mainly orthogneisses such as Serizzo and Beola, and subordinately granites, marbles and other rocks. The most important and extensively exploited ornamental stone from the VCO province is surely the Serizzo, commercialized in four main varieties, and representing about 70% of all the stone production from the VCO area. The protholith of the Serizzo is a Permian granite - granodiorite metamorphosed during the alpine events, and the rock-forming minerals are mainly quartz, K-feldspar, plagioclase (andesine), biotite, with variable amounts of muscovite and epidote (allanite). The other important ornamental stone of the VCO province is the Beola, a series of heterogeneous materials (mainly orthogneisses) with marked (mylonitic) foliation and strong mineralogical lineation, occurring in the median Ossola Valley; its production (15% of the whole stones of the VCO) is subordinated with respect to that of Serizzo. The mineralogical composition of the Beola varieties is similar to Serizzo, consisting of quite homogeneous quartz, K-feldspar (orthoclase or microcline), plagioclase, biotite and muscovite. The main differences relate to the grain size, the rock fabric (generally mylonitic) and to the presence of accessory/secondary minerals. Recent regulatory developments and the growing environmental awareness, require an increasing reuse of wastes deriving from the extraction and processing of dimension stones (up to 50 % of the extracted gross volume). Granite wastes from the VCO (Baveno pink granite and Montorfano white granite), after specific industrial treatments (crushing, sieving, drying, magnetic separation of biotite and hornblende), are used successfully as quartz-feldspars mix in the ceramic industry, with very low FeOtot content. On the other hand, other quartzose

  7. Origin of the magmatic varieties of the Serdán-Oriental Basin, eastern Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Mori, L.; Gomez-Tuena, A.; Becerra Torres, E.; Landa-Piedra, L.

    2013-12-01

    metasomatic agent involved in the petrogenesis is a partial melt of the eclogite-facies subducting oceanic plate. Specifically, strong HREE depletions and fractionations, high Nb/Ta ratios and negative Zr-Hf anomalies in these rocks provide evidence for the presence of residual garnet and rutile in the slab; whereas preferential breakdown of white mica and allanite/monazite may account for the marked LILE-LREE enrichments. The contribution of this high-pressure subduction agent is consistent with the steep geometry and great depth of the Cocos plate beneath the SOB. In lower proportions, this slab melt component also appears to contribute to the genesis of the typical calc-alkaline rocks that coexist with the high-K suite at the arc front; and it becomes progressively more diluted in the transitional products emplaced along the central and northern sectors of the basin. On the other hand, the high-Nb suite was likely produced by low degrees of decompression melting of a drier mantle, with negligible contributions from the deeply subducting slab. Work supported by PAPIIT-UNAM IB100912-2 grant.

  8. Early Cretaceous Erlangmiao Metaluminous A-type Granite in the Eastern Qinlin Orogen, central China: Geochronological and Geochemical Constraints

    Science.gov (United States)

    Zhang, J.; Ma, C.; Sher, Z.; Wang, S.; Wang, L.; Cao, Y.

    2007-12-01

    depleted mantle model ages are 1.5-1.7 Ga. Geochemistry and modal calculations suggest the EGGs are metaluminous A-type granites, underwent fractional crystallization of plagioclase, allanite and apatite, and formed in extensive background. We suggest the formation of the EGG is related to Early Cretaceous asthenosphere upwelling and lithosphere extension in Eastern China. The GGs-wall rocks of the EGG, crystallized at 128±2 Ma according to LA-ICPMS zircon U-Pb method, display metaluminous and high- K calc-alkaline characteristics. The GGs have high ΣREE, Sr/Y and (La/Yb)N ratios, show middle negative Eu anomaly, are enriched in Light REE, Rb, Sr, Ba and depleted in Ta, Nb, Zr, Hf, Ti, P, Y. The isotope is homogeneous, Initial 87Sr/86Sr ratios of the whole rocks are 0.707, the ɛ Nd(130Ma) values are -11.2 and Nd depleted mantle model ages are about 1.9 Ga. It suggested that partial melting of crustal rocks may form high-temperature A-type granites. Comparing the characteristics of the EGGs and the GGs, we suggest that partial melting of the GGs formed the EGGs influenced by asthenosphere upwelling.

  9. Petrochronological investigations to unravel the tectono-metamorphic history of Alpine subduction (Briançonnais, Queyras, Western Alps)

    Science.gov (United States)

    Lanari, Pierre

    2015-04-01

    The study of the tectonic and metamorphic history of the Alpine metamorphic belt involving oceanic and continental subduction processes requires knowledge of detailed Pressure-Temperature-time-deformation (P-T-t-ɛ) paths recorded by different tectono-metamorphic units across the belt. This task is particularly challenging in low-grade rocks, e.g. metapelites, (a) for thermobarometry, and (b) for geochronology. Metapelites at greenschist facies metamorphic conditions show a narrow spectrum of metamorphic minerals, notably quartz, chlorite and K-white mica, in addition to commonly detrital relics inherited from previous metamorphic rocks. To obtain reliable P-T estimates, a multi-method approach is required, which usefully combines Raman study of Carbonaceous Material (RSCM), chemical analysis in standardized X-ray maps, and multi-equilibrium inverse thermodynamic modelling of chlorite and white mica. In order to be able to link each assemblage to a specific metamorphic stage and determine the time scales and rates of metamorphism, it is critical to use in situ dating techniques. In this study, high-resolution geochronology was conducted including single-grain 40Ar/39Ar dating (step heating), where possible in combination with U-Th-Pb age-dating of allanite by LA-ICP-MS analysis. In the French western Alps, the Briançonnais zone is a remnant of the continental subduction wedge, while the Liguro-Piedmontais zone is a fossil oceanic subduction wedge. Metapelites from these two complexes were investigated to constrain the individual P-T-t paths recorded in each tectonic slice. This study focussed on deciphering four tectono-metamorphic units in the Briançonnais zone: (B1) The Internal basement; (B2) the Lower and (B3) Upper Zone Houillère; (B4) the Mesozoic Nappe Stack. These continental units recorded green-schist Alpine metamorphic conditions. In the Liguro-Piedmontais zone, five tectono-metamorphic units are identified: (LP1) the Péouvou; (LP2) Saint-Véran; (LP

  10. Geochemical characteristics of rare earth elements in soil of the Ditru Massif, Eastern Carpathians, Romania

    Science.gov (United States)

    Ion, Adriana

    2013-04-01

    is 273.14 μg g-1. The chemical analysis of soil showed an enrichment in LREE (from La to Eu) and a depletion in HREE (from Gd to Lu). Relatively high levels of LREE concentration in soil are genetically associated with REE mineralization. The soil samples developed on the syenite and nephelin syenite are enriched in HREE. The REE chondrite - normalized plots showed for most soils in the sampling area strongly negative anomalies for cerium and europium, positive anomalies for gadolinium and dysprosium. The distribution of REE in soil is given and controlled by the presence of primary minerals (potasic and plagioclase feldspars) and accessory minerals (zircon, monazite, titanite, allanite, apatite, xenotime, thorite, bastnäsite) in bedrock.

  11. Caracterización petrográfica y geoquímica del batolito Cerro Aspero-Alpa Corral (32°34'-32°42' LS y 64°43'-64°52' LO, provincia de Córdoba, Argentina

    Directory of Open Access Journals (Sweden)

    Porta, G.

    1992-12-01

    Full Text Available The Cerro Aspero-Alpa Corral (CA-AC batholith is a 440 km2 granite body present in the Southern edge of the Eastern Pampean Ranges, Córdoba province, central Argentina. The intrusive body of probably paleozoic age shows both post-tectonic and epizonal character. Country rocks include Upper Precambrian-Lower Paleozoic metasedimentary rocks mainly represented by mica-schists, gneisses and migmatites, locally interrupted by minor amphibolite and marble outcrops.This paper deals with representative petrographic and geochemical data that characterize a 150 km2 central stripe between 32°34'-32°42'S and 64°43'-64°52'W.Three granitic facies have been distinguished based on their distinctive modal mineralogy and texture, and upon well known chemical parameters.A K-feldspar megacryst porphydic-type is the areally prevalent facies, but dykes of micro- leucogranites and biotite-phenocryst bearing granite are also well represented. They are all monzogranites of subalkaline and peraluminous chemistry. Their mineralogy shows variable proportions of QAP constituents and micas, with minor phases represented by Fe-Ti oxides, apatite (Ap, titanite (Tt, allanite (Aln.Microgranular enclaves, abundantly distributed in the porphydic facies, provide valuable information for a better understanding of parental magma evolution.The high-Ca content of the melt makes this body quite distinctive compared to its larger northern neighbour, the Achala batholith.Pegmatite and aplite bodies, as well as fluorite bearing breccias and quartz veins, barren or mineralized, are also present within the CA-AC batholith.El batolito Cerro Aspero-Alpa Corral (CA-AC es un cuerpo granítico que aflora en el extremo sur de las Sierras Pampeanas Orientales, en la provincia de Córdoba, República Argentina, cubriendo una superficie cercana a los 440 km2.Es un cuerpo intrusivo postcinemático de probable edad paleozoica. Las rocas encajantes son metamorfitas correspondientes al Prec

  12. Felsic magmatism and uranium deposits

    International Nuclear Information System (INIS)

    The strongly incompatible behaviour of uranium in silicate magmas results in its concentration in the most felsic melts and a prevalence of granites and rhyolites as primary U sources for the formation of U deposits. Despite its incompatible behavior, U deposits resulting directly from magmatic processes are quite rare. In most deposits, U is mobilized by hydrothermal fluids or ground water well after the emplacement of the igneous rocks. Of the broad range of granite types, only a few have U contents and physico-chemical properties that permit the crystallization of accessory minerals from which uranium can be leached for the formation of U deposits. The first granites on Earth, which crystallized uraninite, dated at 3.1 Ga, are the potassic granites from the Kaapval craton (South Africa) which were also the source of the detrital uraninite for the Dominion Reef and Witwatersrand quartz pebble conglomerate deposits. Four types of granites or rhyolites can be sufficiently enriched in U to represent a significant source for the genesis of U deposits: per-alkaline, high-K met-aluminous calc-alkaline, L-type peraluminous and anatectic pegmatoids. L-type peraluminous plutonic rocks in which U is dominantly hosted in uraninite or in the glass of their volcanic equivalents represent the best U source. Per-alkaline granites or syenites are associated with the only magmatic U-deposits formed by extreme fractional crystallization. The refractory character of the U-bearing minerals does not permit their extraction under the present economic conditions and make them unfavorable U sources for other deposit types. By contrast, felsic per-alkaline volcanic rocks, in which U is dominantly hosted in the glassy matrix, represent an excellent source for many deposit types. High-K calc-alkaline plutonic rocks only represent a significant U source when the U-bearing accessory minerals (U-thorite, allanite, Nb oxides) become metamict. The volcanic rocks of the same geochemistry may be

  13. Tracing Nile sediment sources by Sr and Nd isotope signatures (Uganda, Ethiopia, Sudan)

    Science.gov (United States)

    Padoan, Marta; Garzanti, Eduardo; Harlavan, Yehudit; Villa, Igor Maria

    2011-06-01

    Strontium and neodymium isotopes, measured on diverse mud and sand fractions of sediment in transit along all major Nile branches, identify detritus sourced from Precambrian basements, Mesozoic strata, and Tertiary volcanic rocks exposed along the shoulders of the East African rift and in Ethiopian highlands. Sr and Nd isotopic ratios reflect the weighted average of detrital components generated in different catchments, allowing us to discriminate provenance, calculate sediment budgets, and investigate grain-size and hydraulic-sorting effects. 87Sr/ 86Sr and 143Nd/ 144Nd range, respectively, from as high as 0.722 and as low as 0.5108 for sediment derived from Archean gneisses in northern Uganda, to 0.705 and 0.5127 for sediment derived from Neoproterozoic Ethiopian and Eritrean basements. 87Sr/ 86Sr and 143Nd/ 144Nd, ranging 0.705-0.709 and 0.5124-0.5130 for Blue Nile tributaries, are 0.704-0.705 and 0.5127-0.5128 for largely volcaniclastic sediments of River Tekeze-Atbara, and 0.705-0.706 and 0.5126-0.5127 for main Nile sediments upstream Lake Nasser. Model mantle derivation ages ( tDM), oldest in Uganda where sediment is principally derived from the Congo Craton (3.4-3.0 Ga for Victoria and Albert Nile), progressively decrease northward across the Saharan Metacraton, from 2.6 Ga (Bahr el Jebel in South Sudan), to 2.4-2.2 Ga (Bahr ez Zeraf across the Sudd), and finally 1.6-1.3 Ga (White Nile upstream Khartoum). Instead, tDM ages of Sobat mud increase from 0.9 to 1.5 Ga across the Machar marshes. TDM ages are younger for sediments shed by Ethiopian (1.2-0.7 Ga) and Eritrean basements (1.5-1.2 Ga), and youngest for sediments shed from Ethiopian flood basalts (0.3-0.2 Ga). Integrated geochemical, mineralogical, and settling-equivalence analyses suggest influence on the Nd isotopic signal by volcanic lithic grains and titanite rather than by LREE-rich monazite or allanite. Because contributions by ultradense minerals is subordinate, intrasample variability of Sr and

  14. Reaction zone between pre-UHP titanite and host rock: insights into fluid-rock interaction and deformation mechanisms during exhumation of deeply subducted continental crust (Dabie Shan UHP unit, China)

    Science.gov (United States)

    Wawrzenitz, N.; Romer, R. L.; Grasemann, B.; Morales, L. F. G.

    2012-04-01

    titanite grains are patchy zoned and replace, along with rutile, calcite, quartz, and apatite, the old titanite megacryst. This reaction reflects the changing CO2 versus fluorine activity in the available fluid phase, rather than changing P-T conditions. The Sr isotope composition of the phases formed by these fluid-mediated reactions is variable and depends on the reaction-history and origin of the fluids. (iii) Brittle deformation of the titanite megacryst induced the formation of fractures, enhancing fluid transport and precipitation of new titanite, allanite, calcite ± rutile, and albite (locally anorthite), as well as Zn(Fe) - and Cu - sulphides along the vein walls. Dislocation creep is indicated by subgrains in local zones of high differential stress within the rim of the titanite megacryst. However, dissolution precipitation creep has been much more effective in changing the (isotope)chemical composition of titanite compared to dislocation creep. Romer, R.L., Wawrzenitz, N., Oberhänsli, R., 2003. Terra Nova 15, 5, 330-336. Wawrzenitz, N., Romer, R.L., Oberhänsli, R., Dong, S., 2006. Lithos 89, 1-2, 174-201.

  15. Orogenic development of the Adrar des Iforas (Tuareg Shield, NE Mali): New geochemical and geochronological data and geodynamic implications

    Science.gov (United States)

    Bosch, Delphine; Bruguier, Olivier; Caby, Renaud; Buscail, François; Hammor, Dalila

    2016-05-01

    Laser-ablation U-Th-Pb analyses of zircon and allanite from magmatic and metamorphic rocks of the Adrar des Iforas in Northern Mali allow re-examining the relationships between the different crustal units constituting the western part of the Tuareg Shield, as well as the timing of magmatic and metamorphic events in the West Gondwana Orogen. Granulite-facies metamorphism in the Iforas Granulitic Unit (IGU) and at In Bezzeg occurred at 1986 ± 7 Ma and 1988 ± 5 Ma respectively. This age is slightly younger, but consistent with that of the HT granulite facies event characterizing the In Ouzzal granulitic unit (IOGU), thereby substantiating the view that these units once formed a single granulitic belt of c. 800 km long. High-grade metamorphic basement units of the Kidal terrane surrounding the IGU contain Paleoproterozoic magmatic rocks crystallized between 1982 ± 8 Ma and 1966 ± 9 Ma. Inherited components in these rocks (2.1 Ga and 2.3-2.5 Ga) have ages similar to that of detrital zircons at In Bezzeg and to that of basement rocks from the IGU. This is taken as evidence that the Kidal terrane and the IGU formed a single crustal block at least until 1.9 Ga. East of the Adrar fault, the Tin Essako orthogneiss is dated at 2020 ± 5 Ma, but escaped granulite facies metamorphism. During the Neoproterozoic, the Kidal terrane underwent a long-lived continental margin magmatism. To the west, this terrane is bounded by the Tilemsi intra-oceanic island arc, for which a gneissic sub-alkali granite was dated at 716 ± 6 Ma. A synkinematic diorite extends the magmatic activity of the arc down to 643 ± 4 Ma, and, along with literature data, indicates that the Tilemsi arc has a life span of about 90 Ma. Backward docking to the western margin of the Kidal terrane is documented by migmatites dated at 628 ± 6 Ma. Subduction related processes and the development of the Kidal active margin was responsible for the development of a back-arc basin in the Tafeliant area, with

  16. Black and red granites in the Egyptian Antiquity Museum of Turin. A minero-petrographic and provenance study.

    Science.gov (United States)

    Serra, M.; Borghi, A.; Vaggelli, G.; D'Amicone, E.; Vigna, L.

    2009-04-01

    materials used for two of the best known masterpieces of Egyptian art. As regards to red granites, it has been observed that most of the exposed sculptures were made of rocks closely akin to Aswan granite. Just in one case, the Ram headed sphinx (cat. 836), macroscopic differences in colour index, grain size and isoorientation of feldspar phenocrysts, suggested a different provenance of the source material and determined the choice of picking up a small fragment for minero-petrographic analysis. The sample collected from the sarcophagus of Nefertari (suppl. 5153) during the recent restoration of the sculpture, was analysed in order to test the accuracy of the results, as the provenance of the material used for its realization was already certain. Petrographic observations and chemical analysis were undertaken by a scanning electron microscope equipped with an energy-dispersive spectrometer. Minero-petrographic data primarily showed that all samples vary in composition from granite (red granites) to granodiorite and tonalite (black granites). The main sialic phases are represented by plagioclase (albite to oligoclase), alkali-feldspar (microcline) and quartz, while femic phases are amphibole (green horneblende) and biotite (Fe- to Mg-biotite), always coexisting in variable relative percentages. Minor amount of apatite (≈ 1 wt.%), magnetite, ilmenite, often associated to sphene, zircon, pyrite and allanite also occur. The identification of some compositional markers in all samples suggested a common provenance for all the rocks used for the sculptures. Thus, it was supposed that they could all have been quarried in the famous district of Aswan, well known at least since Dynastic period. This provenance hypothesis was confirmed by geological literature and archeological evidences, considering the relative proximity of Aswan quarries to Nile river and to the key centres of power in the New Kingdom. Therefore, several geological samples were collected in Aswan area, in order

  17. 内蒙古赵井沟大型铌钽矿床地质特征及成因%Geological features and origin of Zhaojinggou Nb-Ta deposit in Wuchuan County, Inner Mongolia

    Institute of Scientific and Technical Information of China (English)

    聂凤军; 王丰翔; 赵宇安; 孙艳; 柴华

    2013-01-01

    Located in the central-eastern section of the Yinshan Precambrian uplift in the western segment of the Inner Mongolian Axis of the Northern China craton,the newly discovered Zhaojinggou deposit is one of the largest Nb-Ta deposits in northern China.During the Hercynian orogeny,intense tectonic and igneous activities resultedin the large-scale granitoid magmatism in Zhaojinggou and its neighboring areas.The Zhaojinggou alkaline feldspar granitoid (AFG) intrusive complex was emplaced in the meta-sedimentary sequence of the Middle Carboniferous Shuanmazhuang Group,controlled by NE-,NNE-and NW-trending fault zones.The AGI complex has an outcrop area of 0.05 km2,and consists mainly of alkaline feldspar granite (AFG),AFG pegmatite and AFG aplite that have no difference in mineral assemblage.Rock-forming minerals are mainly quartz,amazonite and albite associated with minor biotite,muscovite and sericite.Accessory minerals are rutile,apatite,zircon,topaz,fluorite,allanite and columbite.The AFG intrusive complex is petrochemically characterized by relatively high Al2O3,SiO2,Na2O,Rb,Nb,Ta and Hf,obviously low CaO,Fe2O3,FeO,MgO,Sr,Ba,Zr and REE,belonging to silicon-high,sodium-rich rock of calc-alkaline series.Nb-and Tamineralization occurs entirely within the Zhaojinggou AFG intrusive complex as veinlets and disseminated blocks.Nb-and Ta-ores consist of parisite,columbotantalite,cassiterotantalite (ixiolite),monazite,bismuthinite,chevkinite,laplandite,rutile,topaz,apatite,amazonite,Li-Rb-bearing biotite,Li-Rb-bearing muscovite,epidote,fluorspar,hornblende,zircon,quarzt,barite,albite and calcite.As the most important economic Nb-and Taminerals,columbotantalite,cassiterotantalite (ixiolite) and parisite occur in the forms of impregnation,very fine grains,thin films,aggregated fine grains in the AFG intrusive complex.LA-ICP-MS U-Pb isotopic dating of the zircon separates from the AFG intrusive complex has given the ages varying from (277.14 ± 0.82) Ma to (276.6 ± 2.1) Ma

  18. Uranium and thorium in granitic rocks of northeastern Washington and northern Idaho, with comments on uranium resource potential

    Science.gov (United States)

    Nash, J. Thomas

    1979-01-01

    possibly as minute uraninite grains, whereas in the hornblende suite uranium resides primarily in sphene, zircon, and allanite. Many muscovite-bearing plutons are considered fertile by the following two criteria: high uranium content, and uranium residence in labile phases. The hornblende-bearing granitic plutons are not considered fertile, regardless of uranium content, because uranium resides in refractory phases. Twenty-one sample localities in four plutons are considered highly anomalous according to one or more of the following attributes: (1) Uranium content =115.8 ppm (total population mean plus 1 d). (2) Thorium content =30.3 ppm (mean plus 1 d) and uranium =8.8 ppm (mean). (3) Th/U lower than 1.68 (mean minus 1 d) and uranium content -18.8 ppm. The four identified highly anomalous plutons are, from southwest to northeast, (1) Cretaceous porphyritic quartz monzonite of the Midnite mine; (2) Cretaceous muscovite quartz monzonite east of Deer Lake; (3) Cretaceous quartz monzonite of Hungry Mountain, and (4) Cretaceous quartz monzonite of Granite Pass. The study area is favorable for at least five types of uranium deposits including: intragranitic hydrothermal veins as in the Massif Central, France; intragranitic supergene veins, as at the Daybreak mine; contact zone deposits, as at the Midnite mine; and basal-type sandstone deposits, as at the Sherwood mine. The fifth type is Rossing-type deposits for which the high-grade metamorphic terrane of the Kettle River Range, Ferry County, seems favorable, if sufficient volume of low-tenor rock can be located. The first four deposit types seem most likely in or adjacent to uraniferous plutons, as no other uranium source rocks have been identified in the area. Contact zone deposits and intragranitic hydrothermal veins, both possibly supergene-enriched, and basal-type deposits in Tertiary sandstone and conglomerate, seem most likely to be of economic importance. Exploration and discovery of potential uranium depositions

  19. 大兴安岭岔路口矿区中生代多期岩浆活动与钼成矿作用%Mesozoic multiple magmatic activities and molybdenum mineralization in the Chalukou ore district, Da Hinggan Mountains

    Institute of Scientific and Technical Information of China (English)

    聂凤军; 孙振江; 刘翼飞; 吕克鹏; 赵宇安; 曹毅

    2013-01-01

    minor biotite and sericite. Accessory minerals are magnetite, apatite, zircon, sphene and allanite. The two porphyry stocks are petrochemically characterized by relatively high SiO2, K2O, F, Rb, Nb, U, Th,Y and Yb and obviously low CaO, Fe2O3+FeO, MgO, Sr, Ba and REE, with positive ?Nd (t) value. Molybdenum mineralization occurs within the Chalukou porphyry stocks and volcanic rocks as stockwork, veins, veinlets and disseminated blocks. The molybdenum ore consists of pyrite, chalcopyrite, molybdenite, sphalerite, galena, magnetite, pyrrhorite, K-feldspar, fluorite, quartz, sericite and chlorite. As the most important economic molybdenum mineral, molybdenite occurs in the forms of impregnation, radioflake, thin film, aggregated flakes and veinlet. Re-Os isotopic age dating of eight molybdenite separates from the Chalukou deposit yielded an isochron age of 146.9±0.8 Ma and model ages ranging from 146.2 to 149.1Ma with an average value of 147.4Ma. As the Re-Os isochron age is in agreement with field geological evidence, the authors hold that the Re -Os isochron age represents the major ore -forming time of the Chalukou deposit, which corresponded to geodynamical setting of intracontinental extension after the collision of the Siberian plate and North China -Mongolian tract. Hydrothermal alteration at Chalukou shows rough zonation of K feldspathization, greisenization, silicification, and propylitization from the two porphyry stocks outwards. Of these alterations, silicification and greisenization are well developed, and have intimate relationship with molybdenum mineralization. Studies show that all these ore-forming materials, dynamic forces and fluids might have been provided by the Yanshanian granitoid magma. Moreover, the accumulation conditions of the ore-forming materials were offered by the NW - and NE -trending lineament and ring fractured zone as well as Jurassic volcano -sedimentary rocks. A comparative analysis indicates that the Chalukou deposit belongs to

  20. Re-Os isotopic dating of molybdenite separates from Chalukou porphyry Mo polymetallic deposit in Heilongjiang Province%黑龙江岔路口钼多金属矿床辉钼矿铼-锇同位素年龄及地质意义

    Institute of Scientific and Technical Information of China (English)

    聂凤军; 孙振江; 李超; 刘翼飞; 吕克鹏; 张可; 刘勇

    2011-01-01

    岔路口矿床是迄今为止在中国北方发现的最大规模钼多金属矿床,钼、铅锌和银的储量分别为134万t、37万t和4200 t.考虑到大规模地质勘查工作仍在进行中,金属储量的增加只是个时间问题.为了进一步查明岔路口矿床的形成时间,笔者对主要钼多金属矿体8件辉钼矿样品进行了铼-锇同位素分析,所获同位素等时线年龄为(146.96±0.79) Ma(2σ),其MSWD值为1.2.鉴于辉钼矿呈浸染状和团块状分布于花岗斑岩岩株中,并且与部分黄铁矿和黄铜矿呈共生结构关系,可以推测岔路口地区钼多金属矿床及花岗斑岩的形成时间均为晚侏罗世,属燕山中期构造-岩浆活动的产物.岔路口钼多金属矿床形成时代的厘定对于提高该矿床的理论研究水平和指导隐伏金属矿床的找矿勘查工作均具有重要意义.%Located at the northernmost corner of the Deerbugan metallogenic belt and in the northeastern part of the Mongolian-Hinggan amalgamated massif, the newly found Chalukou ore deposit is the largest molybdenum poly-metallic deposit ever discovered in China. It contains 1.34 Mt of Mo (metal), 0.37 Mt of Pb-Zn and 4 200 t of Ag. As a part of the evaluation project of the molybdenum deposit, mineral exploration around Chalukou is still underway. During the Mesozoic Yanshanian orogeny, intense extensional tectonic and igneous activities resulted in the formation of large-scale acid volcanic rocks and granitoid intrusions at Chalukou and its neighboring areas. The Chalukou granite porphyry and quartz porphyry stocks were emplaced in the Jurassic volcano-sedimentary sequence controlled by NE-and NW-trending fault zones. Rock-forming minerals of the two porphyry stocks are mainly quartz, microcline, microperthite and plagioclase associated with minor biotite and sericite. Accessoryminerals include magnetite, apatite, zircon, sphene, and allanite. Molybdenum mineralization occurs within the Chalukou porphyry stocks