The Experts below are selected from a list of 27 Experts worldwide ranked by ideXlab platform
Zhou You-qin - One of the best experts on this subject based on the ideXlab platform.
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Primary Discussion of Au Secondary Enrichment Regularity in Zhijinshan Deposit
Guizhou Geology, 2015Co-Authors: Zhou You-qinAbstract:Zijinshan Cu- Au deposit bears high- sulphur low temperature shallow- seated Hydrothermal Feature. The gold ore body occurs in oxidation zone,it is secondary- enrichment gold deposit which is formed by hypergenesis in the primary gold- riched sulfide deposit. The main composition of the host rocks and wall rocks in Zijinshan Cu- Au deposit is the middle- fine grained granit,the second is the concealed explosion breccia and dacite porphyry. The concealed explosion breccia and dacite porphyry outcrop on the surface spread the northwest and southeast of Zijinshan volcanic pipe like a crab. The gold ore body only enriches where the concealed explosion breccia and dacite porphyry occurs. After studying the spatial distribution form of the gold ore deposit,Zijinshan volcanic apparatus and the oxidation characteristics of metal sulfide in Zijinshan Cu- Au deposit comparatively. In this paper,it puts forward the perspective that there are close relations between secondary- enrichment rule in Zijinshan Cu- Au deposit and the morphological characteristics of cryptoexplosive breccia and dacite- porphyrite formed after intruding into or crop out the earth's surface.
Jan P Amend - One of the best experts on this subject based on the ideXlab platform.
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Sulfur and oxygen isotope insights into sulfur cycling in shallow-sea Hydrothermal vents, Milos, Greece
Geochemical Transactions, 2014Co-Authors: William P Gilhooly, David A Fike, Gregory K Druschel, Fotios-christos A Kafantaris, Roy E Price, Jan P AmendAbstract:Shallow-sea (5 m depth) Hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction. Seafloor vent Features include large (>1 m^2) white patches containing Hydrothermal minerals (elemental sulfur and orange/yellow patches of arsenic-sulfides) and cells of sulfur oxidizing and reducing microorganisms. Sulfide-sensitive film deployed in the vent and non-vent sediments captured strong geochemical spatial patterns that varied from advective to diffusive sulfide transport from the subsurface. Despite clear visual evidence for the close association of vent organisms and Hydrothermalism, the sulfur and oxygen isotope composition of pore fluids did not permit delineation of a biotic signal separate from an abiotic signal. Hydrogen sulfide (H_2S) in the free gas had uniform δ^34S values (2.5 ± 0.28‰, n = 4) that were nearly identical to pore water H_2S (2.7 ± 0.36‰, n = 21). In pore water sulfate, there were no paired increases in δ^34S_SO4 and δ^18O_SO4 as expected of microbial sulfate reduction. Instead, pore water δ^34S_SO4 values decreased (from approximately 21‰ to 17‰) as temperature increased (up to 97.4°C) across each Hydrothermal Feature. We interpret the inverse relationship between temperature and δ^34S_SO4 as a mixing process between oxic seawater and ^34S-depleted Hydrothermal inputs that are oxidized during seawater entrainment. An isotope mass balance model suggests secondary sulfate from sulfide oxidation provides at least 15% of the bulk sulfate pool. Coincident with this trend in δ^34S_SO4, the oxygen isotope composition of sulfate tended to be ^18O-enriched in low pH (75°C) pore waters. The shift toward high δ^18O_SO4 is consistent with equilibrium isotope exchange under acidic and high temperature conditions. The source of H_2S contained in Hydrothermal fluids could not be determined with the present dataset; however, the end-member δ^34S value of H_2S discharged to the seafloor is consistent with equilibrium isotope exchange with subsurface anhydrite veins at a temperature of ~300°C. Any biological sulfur cycling within these Hydrothermal systems is masked by abiotic chemical reactions driven by mixing between low-sulfate, H_2S-rich Hydrothermal fluids and oxic, sulfate-rich seawater.
Bernard Bingen - One of the best experts on this subject based on the ideXlab platform.
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Geochronology and palaeomagnetism of the Hunnedalen dykes, SW Norway: implications for the Sveconorwegian apparent polar wander loop
Earth and Planetary Science Letters, 1999Co-Authors: H. J. Walderhaug, Trond H. Torsvik, Elizabeth A. Eide, Bjørn Sundvoll, Bernard BingenAbstract:The post-Sveconorwegian Hunnedalen dyke swarm intrudes the high-grade Proterozoic gneiss complex of SW Norway. The dykes yield a Sm‐Nd whole-rock-mineral date of 855 " 59 Ma and a 40 Ar= 39 Ar biotite plateau date of 848 " 27 Ma (2! ). The consistency of these two age determinations suggests that 850 Ma approximates the intrusion age of the swarm. Palaeomagnetic data from the dykes match palaeomagnetic directions obtained from Late Sveconorwegian massive-type anorthosites (932‐929 Ma) in SW Norway. The collective palaeomagnetic data (mean pole: latitude D 43.7oS, longitude D 213.3oE, A95 D 4:6o) have uniform magnetic polarity, and, when considered in the context of the new geochronologic data, require that remanence acquisition in Sveconorwegian rocks (massif-type anorthosites and gneissic basement) of SW Norway is, in fact, not Sveconorwegian in age, but rather younger and related to a regional metamorphic=Hydrothermal Feature at ca. 850 Ma. The new age data question the validity of a counter-clockwise Sveconorwegian apparent polar wander loop in the Baltic data-sets and therefore require a critical re-evaluation of Rodinia Supercontinent fits based on palaeomagnetic data. 1999 Elsevier Science B.V. All rights reserved.
Liu Xing-zhong - One of the best experts on this subject based on the ideXlab platform.
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Stable Isotopic Characteristics of the Chagangnuoer Iron Deposit in Western Tianshan,Xinjiang and Its Geological Significance
Rock and Mineral Analysis, 2012Co-Authors: Liu Xing-zhongAbstract:Situated in the Awulale metallogenic belt of Western Tianshan,the large-sized Chagangnuoer magnetite deposit is contained within volcanic-sedimentary rocks of the Carboniferous Dahalajunshan Formation.According to ore fabrics and mineral assemblages,the mineralization events of this deposit were divided into the magmatic stage and the Hydrothermal stage(including the prograde sub-stage).Due to the lack of studies in ore deposit geochemistry for this deposit,this paper aimed to conduct systematic stable isotope analyses of C,O and S by isotope mass spectrometry method for minerals of magnetite,pyrite,chalcopyrite and calcite chosen from various mineralization stages.Those data indicated that δ18OSMOW values of magnetite mainly showed a magmatic Hydrothermal Feature,and a decreasing trend(1.9‰-2.4‰) from the magmatic stage to the prograde stage,which reflected that wall rock alteration may change the compositions of ore-forming fluid.Both the sulfur isotopic components(0.8‰-7.3‰) at the magmatic stage and prograde stage were predominantly the magmatic Feature.However,a small amount of S from strata or sea water was mixed into the ore-forming fluid in the magmatic stage as the δ34SV-CDT was larger than 10‰.During the late ore-forming stage,the δ13CPDB-δ18OSMOW ratios of calcite showed a positive linear correlation,probably attributing to the mixture of different concentrations of NaCl fluid or the water-rock reaction between ore-forming fluid and wall rocks.The partial mineralization materials were derived from marble wall rock.Therefore,crystallization differentiation of magmatic fluid was the dominant mineralization on the early ore-forming stage,whereas prograded and retrograded alterations were the crucial factors in iron enrichment and mineralization on the later stage.
William P Gilhooly - One of the best experts on this subject based on the ideXlab platform.
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Sulfur and oxygen isotope insights into sulfur cycling in shallow-sea Hydrothermal vents, Milos, Greece
Geochemical Transactions, 2014Co-Authors: William P Gilhooly, David A Fike, Gregory K Druschel, Fotios-christos A Kafantaris, Roy E Price, Jan P AmendAbstract:Shallow-sea (5 m depth) Hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction. Seafloor vent Features include large (>1 m^2) white patches containing Hydrothermal minerals (elemental sulfur and orange/yellow patches of arsenic-sulfides) and cells of sulfur oxidizing and reducing microorganisms. Sulfide-sensitive film deployed in the vent and non-vent sediments captured strong geochemical spatial patterns that varied from advective to diffusive sulfide transport from the subsurface. Despite clear visual evidence for the close association of vent organisms and Hydrothermalism, the sulfur and oxygen isotope composition of pore fluids did not permit delineation of a biotic signal separate from an abiotic signal. Hydrogen sulfide (H_2S) in the free gas had uniform δ^34S values (2.5 ± 0.28‰, n = 4) that were nearly identical to pore water H_2S (2.7 ± 0.36‰, n = 21). In pore water sulfate, there were no paired increases in δ^34S_SO4 and δ^18O_SO4 as expected of microbial sulfate reduction. Instead, pore water δ^34S_SO4 values decreased (from approximately 21‰ to 17‰) as temperature increased (up to 97.4°C) across each Hydrothermal Feature. We interpret the inverse relationship between temperature and δ^34S_SO4 as a mixing process between oxic seawater and ^34S-depleted Hydrothermal inputs that are oxidized during seawater entrainment. An isotope mass balance model suggests secondary sulfate from sulfide oxidation provides at least 15% of the bulk sulfate pool. Coincident with this trend in δ^34S_SO4, the oxygen isotope composition of sulfate tended to be ^18O-enriched in low pH (75°C) pore waters. The shift toward high δ^18O_SO4 is consistent with equilibrium isotope exchange under acidic and high temperature conditions. The source of H_2S contained in Hydrothermal fluids could not be determined with the present dataset; however, the end-member δ^34S value of H_2S discharged to the seafloor is consistent with equilibrium isotope exchange with subsurface anhydrite veins at a temperature of ~300°C. Any biological sulfur cycling within these Hydrothermal systems is masked by abiotic chemical reactions driven by mixing between low-sulfate, H_2S-rich Hydrothermal fluids and oxic, sulfate-rich seawater.
