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Zhengbing Zhou - One of the best experts on this subject based on the ideXlab platform.
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the genesis of the dahebian zn pb deposit and associated barite mineralization implications for hydrothermal fluid venting events along the nanhua basin south china
Ore Geology Reviews, 2018Co-Authors: Han-jie Wen, Zhengbing Zhou, Chaojian Qin, Jeffrey De Fourestier, Ling Liu, Qingpeng ShiAbstract:Abstract The Dahebian stratiform barite deposit, which is situated in the Nanhua Basin, is one of the world’s largest and most important barite deposits. This deposit was formed through sedimentary exhalative processes in the early Cambrian stage. Recently, beneath stratiform barite ore, stratabound Zn-Pb-(Fe-bearing) sulfide mineralization, which is hosted by the Doushantuo Formation, was discovered. Ores that represent Zn-Pb sulfide mineralization are mainly discordant but stratabound. The Doushantuo Formation consists of laminated interbedded layers of micritic dolomite and carbonaceous mudstone, associated with phosphorite and chert. The sulfide ores consist primarily of sphalerite, pyrite and galena. The associated gangue minerals are barite, quartz, minor calcite, as well as trace amounts of apatite and hyalophane. Hyalophane found in the stratiform barite ore is richer in barium but poorer in potassium than that associated with the sulfide ores. This outcome corresponds to ascending hydrothermal fluids that are richer in barium along with sulfide mineralization. Investigation of the ore fluid reveals relatively high temperature (142–368 °C) with scattered salinity (0.53–25.62 wt% NaCl eq.). This finding suggests that fluid cooling and/or mixing with seawater could be the primary mechanisms that prompted the ore formation. Sulfides selected from the zinc-lead sulfide ores and stratiform barite ore have similar sulfur isotopic compositions, with δ34S values ranging from 13.5‰ to 30.0‰; δ34S values of barite from these ores are analogous, with δ34S values ranging from 29.5‰ to 55.1‰. The sulfur isotopic fractionation between minerals (barite and sulfide) and the early Cambrian seawater is ΔBarite-Seawater = 7.8‰ and ΔSulfide-Seawater = −12.1‰, respectively, demonstrating that the sulfur in the Dahebian zinc-lead deposit and the stratiform barite deposit were derived from the early Cambrian stratified seawater column. Lead isotopic compositions of sulfide ores indicate that these ore metals are mainly sourced from rocks of the Doushantuo Formation and the underlying fold basement. Therefore, the Dahebian zinc-lead deposit and stratiform barite deposit probably arose from Selwyn-Type sedimentary exhalative hydrothermal fluids. Zn-Pb sulfides were mineralized in the feeder zone of these hydrothermal fluids, and the stratiform barite ore deposits represent the upper sedimentary-exhalative mineralization. This finding points to intensive Zn-Pb-Fe-Ba hydrothermal fluid venting into the Nanhua Basin and to relatively oxic deep ocean waters during the early Cambrian.
Mingjin Zhu - One of the best experts on this subject based on the ideXlab platform.
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Forming Mechanism Analysis of the Abnormally High δ34S Baryte Deposits: A Case Study from the Zhenning–Ziyun Large Devonian Baryte Deposits, Guizhou Province, China
Geomicrobiology Journal, 2017Co-Authors: Junbo Gao, Ruidong Yang, Lulin Zheng, Wei Cheng, Jun Chen, Mingjin ZhuAbstract:ABSTRACTStratiform Baryte deposits are widespread in Cambrian and Devonian strata in China and around the world. In this article, the authors studied the sulfur isotopic features and forming mechanism of the stratiform Baryte deposits occurring within the Upper Devonian cherts of the Zhenning-Ziyun county, Guizhou province, located in the Southwestern margin of the Yangtze Platform. The sulfur isotopic data from 18 Baryte ore samples of the Leji section of Zhenning county are presented herein with values that range from +41.9‰ to +68.4‰ (AVG = +59.9‰). The δ34S values of the Baryte ore from the Mohao section of Ziyun county are stable and show a narrow range from +41.3‰ to +47.0‰ (AVG = +44.0‰). In the Luocheng section of Ziyun county, the δ34S values of the Baryte ore vary from +27.6‰ to +36.4‰ (AVG = +32.7‰). The δ34S values of all samples are higher than those of the coeval seawater sulfates (+25‰). The scanning electron microscope analysis indicates that spherical, dumbbell-shaped, clavate bacterial a...
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forming mechanism analysis of the abnormally high δ34s Baryte deposits a case study from the zhenning ziyun large devonian Baryte deposits guizhou province china
Geomicrobiology Journal, 2017Co-Authors: Junbo Gao, Ruidong Yang, Lulin Zheng, Wei Cheng, Jun Chen, Mingjin ZhuAbstract:ABSTRACTStratiform Baryte deposits are widespread in Cambrian and Devonian strata in China and around the world. In this article, the authors studied the sulfur isotopic features and forming mechanism of the stratiform Baryte deposits occurring within the Upper Devonian cherts of the Zhenning-Ziyun county, Guizhou province, located in the Southwestern margin of the Yangtze Platform. The sulfur isotopic data from 18 Baryte ore samples of the Leji section of Zhenning county are presented herein with values that range from +41.9‰ to +68.4‰ (AVG = +59.9‰). The δ34S values of the Baryte ore from the Mohao section of Ziyun county are stable and show a narrow range from +41.3‰ to +47.0‰ (AVG = +44.0‰). In the Luocheng section of Ziyun county, the δ34S values of the Baryte ore vary from +27.6‰ to +36.4‰ (AVG = +32.7‰). The δ34S values of all samples are higher than those of the coeval seawater sulfates (+25‰). The scanning electron microscope analysis indicates that spherical, dumbbell-shaped, clavate bacterial a...
H. Kurt - One of the best experts on this subject based on the ideXlab platform.
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Mineralogy and Genesis of the Çanakçi (Ulukisla-Nigde) Baryte Vein Deposits, Central Turkey
Mineralogical Magazine, 1998Co-Authors: H. KurtAbstract:The studied area is located around (~anakqi (Ulukisla) Village in the north of Bolkardag Unit, Central Turkey. The Baryte mineralization occurs within Elmali vulcanite member belonging to UpperPalaeocene aged ~iftehan complex which overlies unconformably the Alihoca ophiolites. The complex on the basis of lithological features can be divided into four members; Kodak shale-sandstone, Elmali volcanite, Aktastepe limestone and Ugtepe monzonite-diorite. The Elmali volcanites consists of basalt, andesite and trachyte lava flows, hypabyssal rocks, pillow lava and agglomerate. The lava flows have a E W strike and are cut by hypabyssal rocks of different phases. The Baryte mineralizations occur nearly 2km southeast-east and 3km southwest of ~anakgi village. The Baryte mineralization in SW of ~anakgi village has nearly lm thick and 33m length. Many small veins of Baryte, nearly parallel to the main ore, are also present in the surrounding areas. Baryte veins contain mainly some galena. Minerals were identified by ore microscopy, and major and trace element analyses were performed by the XRF method. Mineralogy Megascopically, Baryte ore is crystall ine, white and p ink i sh white in colour . Microscopically, small amount of quartz is accompanied with Baryte mineral. Baryte occurs mainly as euhedral but sometimes anhedral crystals. Baryte crystals are colourless, perpendicular sets of cleavage and greyish interference colours indicating small brefringence. Crystals are characterised by polysynthetic twinning, undulatory extinction due to mechanic terrain in common. Mechanic twinning and like moiler texture are also observed in minerals. Baryte is cut by very thin quartz, sphalerite and galena veins and some Baryte inclusion formed in some quartz crystals, all of which indicates that Baryte is formed early than quartz, sphalerite and galena. The Baryte crystals may also show fibrous or prismatic habit with patchy extinction reflecting the presence of considerable stresses during or after the deposition of Baryte. The common opaque minerals are mainly galena, and rare sphalerite, chalcopyrite, pyrite, covellite, ilmenite and fahlore. Secondary minerals are anglesite, malachite, azurite, smitsonite, iron oxide and cerussite. The gangue minerals are represented by quartz, calcite chlorite and muscovite. Chemistry Selected 4 samples from Baryte occurrences were analysed for major and trace elements (Table 1). As seen in Table 1, there is a negative correlation between the Ba and Al203. Feldspar, muscovite and possibly some clay minerals are present in order to account for the A1203 content that ranges between 3.07-12.35%. FeO is very low (0 .1-0 .5%), suggesting that Baryte mineralization occurred at very low temperatures. Extremely low Na20 and CaO contents show clearly that calcium and sodium enriched fluids did not come to deposition environment during the Baryte mineralization. Na20 and K20 occur principally as soluble salts mostly taking the form of chlorides, MgO does not behave as a soluble salt. The main impurity is SiO2 (mainly in the form of quartz mineral) and ranges between 2.1-17.81%. High ratio of Cu (109-161ppm) and TiO2 (0.12-1.56 %) reveals that the mineralising fluids are of hydrothermal origin and mineralising fluids came up from through volcanics and intrusive rocks. S content of the Baryte minerals are between 63984 and 74306 ppm suggesting that the Baryte mineralization is epithermal in origin. In addition, the high Sr values (9605-13603ppm) reflect that the origin of Sr is related with volcanic activity. The very high BaJSr ratio implies that the origin of Ba is the hydrothermal (especially epithermal) origin (Werner, 1958; Starke, 1969). Zn content ranges from 2 to 793 ppm, suggesting that the Baryte occurrence is related with volcanic activity (Marchig et al., 1985). Pb
Reiner Botz - One of the best experts on this subject based on the ideXlab platform.
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the Baryte bearing beryl phosphate pegmatite plossberg a missing link between pegmatitic and vein type barium mineralization in ne bavaria germany
Chemie Der Erde-geochemistry, 2011Co-Authors: Harald G. Dill, Berthold Weber, Reiner BotzAbstract:Abstract Pegmatites and aplites enriched in P, Be, Nb, Ta and Li occur in the high-temperature metamorphic lithological units of the NE Bavarian Basement, SE Germany. They are accompanied by Ba mineralization, in vein-type deposits in the basement as well as in its foreland. Locally, Ba minerals are encountered in the late Variscan pegmatites and aplites too. The shallow discordant stock-like pegmatites (Hagendorf-type) are barren as to Ba, but in the tabular, concordant aplites and pegmatites Ba was concentrated (Plossberg-type). These concordant pegmatites and aplites are supposed to be the root zone of the intrusive pegmatites. In the rare case of low sulfur fugacity, Ba forms Ba–Zr–K–Sc phosphates/silicates in the pegmatites (transition of magmatic into the hydrothermal stages I/II). Under high sulfur fugacity, Ba is accommodated within the same stages in the structure of Baryte. Barium is not accommodated in the lattice of phosphates during or in the immediate aftermaths of the emplacement of these Be–P–Nb–Ta pegmatites (stage III). This element shows up again in APS minerals during supergene alteration under acidic conditions (stage IV). Considering the host rocks of Baryte mineralization, the Sr contents of Baryte increased from the early Paleozoic to the Late Triassic. The Sr contents of Baryte are a function of the depth below ground in the vein-type deposits and in the shear-zones bounding the tabular concordant pegmatites. Beryl is not only a marker mineral for the shear-zone-hosted pegmatites but can also be used as a tool for the geodynamic positioning of these pegmatites using its oxygen isotopes. A subdivision of the pegmatites into intrusive and shear-zone hosted may be achieved by its REE and minor elements.
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The Baryte-bearing beryl-phosphate pegmatite Plössberg—A missing link between pegmatitic and vein-type barium mineralization in NE Bavaria, Germany
Geochemistry, 2011Co-Authors: Harald G. Dill, Berthold Weber, Reiner BotzAbstract:Abstract Pegmatites and aplites enriched in P, Be, Nb, Ta and Li occur in the high-temperature metamorphic lithological units of the NE Bavarian Basement, SE Germany. They are accompanied by Ba mineralization, in vein-type deposits in the basement as well as in its foreland. Locally, Ba minerals are encountered in the late Variscan pegmatites and aplites too. The shallow discordant stock-like pegmatites (Hagendorf-type) are barren as to Ba, but in the tabular, concordant aplites and pegmatites Ba was concentrated (Plossberg-type). These concordant pegmatites and aplites are supposed to be the root zone of the intrusive pegmatites. In the rare case of low sulfur fugacity, Ba forms Ba–Zr–K–Sc phosphates/silicates in the pegmatites (transition of magmatic into the hydrothermal stages I/II). Under high sulfur fugacity, Ba is accommodated within the same stages in the structure of Baryte. Barium is not accommodated in the lattice of phosphates during or in the immediate aftermaths of the emplacement of these Be–P–Nb–Ta pegmatites (stage III). This element shows up again in APS minerals during supergene alteration under acidic conditions (stage IV). Considering the host rocks of Baryte mineralization, the Sr contents of Baryte increased from the early Paleozoic to the Late Triassic. The Sr contents of Baryte are a function of the depth below ground in the vein-type deposits and in the shear-zones bounding the tabular concordant pegmatites. Beryl is not only a marker mineral for the shear-zone-hosted pegmatites but can also be used as a tool for the geodynamic positioning of these pegmatites using its oxygen isotopes. A subdivision of the pegmatites into intrusive and shear-zone hosted may be achieved by its REE and minor elements.
Elizabeth M. Griffith - One of the best experts on this subject based on the ideXlab platform.
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Stable strontium isotope fractionation in synthetic barite
Geochimica et Cosmochimica Acta, 2014Co-Authors: Inoka H. Widanagamage, Edwin A. Schauble, Howie D Scher, Elizabeth M. GriffithAbstract:Abstract The mineral barite (BaSO4) accommodates strontium (Sr) in its crystal structure, providing an archive of Sr-isotopes (87Sr/86Sr and δ88/86Sr) in the highly stable sulfate mineral. We investigated mass dependent stable Sr-isotope fractionation (Δ88/86Sr = δ88/86Srsolid − δ88/86Srsolution) during inorganic precipitation of barite from a barium-rich solution by addition of sulfate under controlled conditions and compared this to equilibrium isotopic fractionation calculated using Density Functional Theory modeling. Sr-substituted barite is predicted to have lower 88Sr/86Sr than any other studied species, and at 25 °C will be about 0.6–0.7‰ lower than the two modeled Sr(H2O)82+-bearing salts that could approximate aqueous Sr2+. This agrees in direction and order of magnitude with experimental results that estimate equilibrium Sr-isotope fractionation in barite to be 0.3‰ lower than aqueous Sr2+ at ∼20 °C. The high ionic strength of some of the precipitating solutions (up to 1 M) and potential differences in the average coordination number of aqueous Sr2+ add to uncertainty in a direct comparison of the calculated equilibrium isotopic fractionation values with the experimental results. Stable Sr-isotope fractionation varied along with the distribution coefficient of Sr [Kd(Sr) = [Sr/Ba]barite/[Sr/Ba]solution], which is a function of both temperature and barite saturation state. However the relationship between mass dependent isotopic fractionation and Kd(Sr) is different for conditions of changing temperature versus barite saturation state. With increasing temperature (from 5 to 40 °C), the barite phase became isotopically lighter (Δ88/86Sr = −0.29‰ to −0.41‰). Conversely, with increasing saturation state (saturation index of barite = 3.0–4.3) the barite phase became isotopically heavier (Δ88/86Sr = −0.25‰ to −0.10‰). These observations suggest chemical kinetic effects control isotopic fractionation rather than equilibrium temperature effects. The relationship with saturation state indicates the potential presence of a diffusive boundary layer. Barite crystal morphology appears to be affected by the diffusion rate of solute (sulfate) to the growing crystal surface relative to the overall growth rate of barite crystals during precipitation.
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barite in the ocean occurrence geochemistry and palaeoceanographic applications
Sedimentology, 2012Co-Authors: Elizabeth M. Griffith, Adina PaytanAbstract:The mineral barite (BaSO4) can precipitate in a variety of oceanic settings: in the water column, on the sea floor and within marine sediments. The geological setting where barite forms ultimately determines the geochemistry of the precipitated mineral and its usefulness for various applications. Specifically, the isotopic and elemental composition of major and trace elements in barite carry information about the solution(s) from which it precipitated. Barite precipitated in the water column (marine or pelagic barite) can be used as a recorder of changes in sea water chemistry through time. Barite formed within sediments or at the sea floor from pore water fluids (diagenetic or cold seeps barite) can aid in understanding fluid flow and sedimentary redox processes, and barite formed in association with hydrothermal activity (hydrothermal barite) provides information about conditions of crust alteration around hydrothermal vents. The accumulation rate of marine barite in oxic-pelagic sediments can also be used to reconstruct past changes in ocean productivity. Some key areas for future work on the occurrence and origin of barite include: fully characterizing the mechanisms of precipitation of marine barite in the water column; understanding the role and potential significance of bacteria in barite precipitation; quantifying parameters controlling barite preservation in sediments; determining the influence of diagenesis on barite geochemistry; and investigating the utility of additional trace components in barite.
