TY - CONF TI - Sub-Seafloor Sulfide Mineralization in the Saldanha Hydrothermal Field, Mid-Atlantic Ridge (MAR) AU - Dias, Ágata AU - Qiu, Wenhong AU - Barriga, Fernando J A S AU - Tao, Chunhui T2 - Goldschmidt2020 C3 - Goldschmidt Abstracts DA - 2020/// PY - 2020 DO - 10.46427/gold2020.44 DP - DOI.org (Crossref) SP - 44 EP - 44 LA - en PB - Geochemical Society UR - https://goldschmidtabstracts.info/abstracts/abstractView?doi=10.46427/gold2020.44 Y2 - 2021/03/30/07:36:23 ER - TY - CONF TI - Ore-Forming Process of the Menez Gwen Hydrothermal Field: In situ S Isotopes and Trace Metals Constraints AU - Dias, Ágata AU - Qiu, Wenhong AU - Costa, Isabel Maria Amaral AU - Barriga, Fernando J A S T2 - Goldschmidt2020 C3 - Goldschmidt Abstracts DA - 2020/// PY - 2020 DO - 10.46427/gold2020.2143 DP - DOI.org (Crossref) SP - 2143 EP - 2143 LA - en PB - Geochemical Society ST - Ore-Forming Process of the Menez Gwen Hydrothermal Field UR - https://goldschmidtabstracts.info/abstracts/abstractView?doi=10.46427/gold2020.2143 Y2 - 2021/03/30/07:36:55 ER - TY - JOUR TI - Constraints of Fe-S-C stable isotopes on hydrothermal and microbial activities during formation of sediment-hosted stratiform sulfide deposits AU - Qiu, Wenhong Johnson AU - Zhou, Mei-Fu AU - Li, Xiaochun AU - Huang, Fang AU - Malpas, John T2 - Geochimica et Cosmochimica Acta AB - Microbial and hydrothermal venting activities on the seafloor are important for the formation of sediment-hosted stratiform sulfide (SHSS) deposits. Fe isotopic compositions are sensitive to both microbial and hydrothermal activities and may be used to investigate the formation of these deposits. However, to the best of our knowledge, no Fe isotopic studies have been conducted on SHSS deposits. In the Devonian Dajiangping SHSS-type pyrite deposit (389 Ma), South China, laminated pyrite ores were precipitated from exhalative hydrothermal fluids, whereas black shales were deposited during intervals with no exhalation. Pyrite grains from black shales mostly display positive δ56Fe-py (0.01–0.73‰), higher than marine sediments (ca. 0‰), due to pyrite deriving Fe from basinal shuttled Fe(III) (hydr-)oxides and slowly crystallizing in pores of sediments with equilibrium fractionation, except for negative δ56Fe-py (−0.17‰ to −0.24‰) of two samples caused by mixing of Fe from underlain laminated ores. The positive δ34S-py (3.50–24.5‰) of black shales reflect that sulfur of pyrite originated from quantitative reduction of sulfate in closed pores of sediments. In contrast, pyrite grains of laminated ores have negative δ56Fe-py (−0.60‰ to −0.21‰), which were not only inherited from the negative δ56Fe of hydrothermal fluids but also caused by kinetic fractionation during rapid precipitation of a pyrite precursor (FeS) in hydrothermal plumes. These ores have negative δ34S-py (−28.7‰ to −1.82‰), because H2S for pyrite mineralization was produced by bacterial sulfate reduction (BSR) in a sulfate-rich seawater column or shallow sediments. The δ56Fe-py values of laminated ores co-vary positively with δ34S-py and δ13C-carbonate along the ore stratigraphy, with δ13C-carbonate values ranging from −12.0‰ to −2.50‰. However, they correlate negatively with aluminum-normalized total organic carbon (TOC/Al2O3). Organic carbon is thus considered to enhance the production of H2S by BSR activities, increase pyrite precipitation rates and promote the expression of kinetic fractionation of Fe isotopes. Intriguingly, in the ore units with vigorous hydrothermal venting activities, δ56Fe-py, δ34S-py and δ13C-carbonate values display a consistently increasing trend. Such results suggest that venting hydrothermal fluids significantly inhibited the H2S production of BSR, which then reduced the pyrite crystallization rate and decreased the kinetic fractionation of Fe isotopes. Our study reveals that the formation of SHSS deposits relies on H2S from microbial activities and metals from hydrothermal exhalation on the seafloor, but that vigorous exhalation can inhibit microbial activities and thus sulfide precipitation rates. The integrated use of Fe, S, and C isotopes can effectively elucidate these dynamic interactions between hydrothermal venting and microbial activities during the formation of SHSS deposits. DA - 2021/11/15/ PY - 2021 DO - 10.1016/j.gca.2021.07.036 DP - ScienceDirect VL - 313 SP - 195 EP - 213 J2 - Geochimica et Cosmochimica Acta LA - en SN - 0016-7037 UR - https://www.sciencedirect.com/science/article/pii/S0016703721004634 Y2 - 2023/04/11/13:56:26 KW - Iron isotope KW - Isotope fractionation KW - Sediment-hosted stratiform sulfide deposit KW - Sulfur isotope ER - TY - JOUR TI - Origin of the Qiyugou gold deposit in the southern margin of the North China Craton: Insights from trace elements of pyrite and mineralogy of Bi-minerals AU - Wu, Qiang AU - Zhao, Tai-Ping AU - Chen, Wei Terry AU - Gao, Xin-Yu AU - Meng, Lei AU - Qiu, Wenhong Johnson T2 - Ore Geology Reviews AB - The Qiyugou gold deposit, located in the Xiong’ ershan area of the North China Craton, contains abundant bismuth-sulfosalts that are closely associated with gold mineralization. Pyrite is the dominant Au-hosted mineral, and has been formed in three generations (Py1, Py2, and Py3). Py1 grains, generally intergrown with milky quartz, are coarse (>1 mm), euhedral in shape, and Au-depleted in composition. In contrast, subhedral Py2 grains, associated with light gray quartz, are medium to coarse (0.2–3 mm) and are enriched in gold that is both invisible and visible. Py3 grains (0.1–0.5 mm), intergrown with abundant sulfide minerals, are relatively fine and Au-depleted. The time-resolved LA-ICP-MS depth profiles of the Py2 grains indicate that invisible gold occurs as either solid solution or nano-particles of native gold and electrum. Visible gold occurs as small blebs in the Py2 grains where inclusions of native bismuth, galenobismutite, lillianite homologs, tetradymite, and galena are also present. In addition, it is common that electrum in microfracture infillings or along grain boundaries of the Py1 and Py2, are intergrown with bismuthinite derivatives, Bi-Cu sulfosalts, emplectite, tetradymite, chalcopyrite, galena, and Py3. Based on textural relationships and mineral assemblages, calculation of physicochemical conditions show that gold was formed in conditions of fTe2 = ~10−11 and fS2 = ~10−11 to 10−12 for Py2, and fTe2 = ~10−9 to 10-11and fS2 = ~10−10 to 10−11 for Py3. We thus proposed that such physicochemical conditions may have triggered the precipitation of Bi melt, and sulfidation driven by cooling or increase in sulfur content results in the transformation of the Au-Bi liquid into a stable assemblage of native gold and bismuthinite. These bismuth minerals are associated with native gold/Au-bearing minerals, indicating that the Au mineralization of the Qiyugou gold deposit might be genetically associated with Bi melt. The present study highlights the role of Bi as important gold scavengers in arsenic-deficient ore-forming fluid. DA - 2021/06/01/ PY - 2021 DO - 10.1016/j.oregeorev.2021.104085 DP - ScienceDirect VL - 133 SP - 104085 J2 - Ore Geology Reviews LA - en SN - 0169-1368 ST - Origin of the Qiyugou gold deposit in the southern margin of the North China Craton UR - https://www.sciencedirect.com/science/article/pii/S0169136821001104 Y2 - 2023/04/11/13:54:18 KW - Bi melts scavenging Au KW - Bismuth minerals KW - Qiyugou gold deposit KW - The southern margin of the North China craton KW - Trace element of pyrite ER - TY - CONF TI - Variability of the hydrothermal fields within the Portuguese seafloor (MAR) AU - Dias, Ágata AU - Relvas, J.M.S.Relvas AU - Marques, A. F. AU - Qiu, Wenhong AU - Barriga, F J A S AU - Ribeiro, L AU - Calado, A T2 - Goldschmidt 2022 UR - https://conf.goldschmidt.info/goldschmidt/2022/meetingapp.cgi/Paper/11686 ER -