A Preliminary Study on Silver Isotopic Composition in Polymetallic Ore Deposits in Eastern China

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A preliminary survey of silver isotopic composition in four polymetallic ores in eastern China shows a larger variation in δ109Ag from-0.014‰to+0.983‰, which is within the total ranges for the entire respective ore deposit types worldwide. The diversity of silver isotopic compositions in ore-deposits reported here and previous studies seemed to preclude simple isotopic links to particular sources, but reflected the silver isotope fractionation in transport- and deposit-related processes in-stead. The δ109Ag values in supergene samples from the Qixiashan Pb-Zn-Ag polymetallic deposit are more positive, in consistent with the statisticalδ109Ag distribution from-0.4‰to+2.2‰in 36 pieces of supergene ore samples around the World, which reflects the diverse controls on silver isotope fraction-ation from the first-order thermodynamic effect, reduction-mediated reaction, remobilization of silver with surficial low-temperature weathering processes. The hypogene samples in Dazhuangzi orogenic Au-Ag ore deposit, have δ109Ag values close to 0, which implies that equilibrium partitioning associated with metal sources at the high-temperature does not result in a resolvable difference in silver isotopic compositions. By contrast, the hypogene samples which are dominated by pyrite without visible silver minerals (i.e., skarn iron ore deposit in Edongnan) have shown the largest variation range of δ109Ag, fol-lowed by that from the porphyry copper ore in Zijinshan. It could be concluded that the surface ad-sorption and/or lattice substitution are important factors to control Ag isotope fractionation in ore-forming processes, especially for skarn deposits with only pyrite. The perspective of silver isotope shows great potentials to understand the processes that lead to the concentrations of metals to economic levels and to constrain the physicochemical conditions during ore-mineralization in metallic ore-deposits.
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2021年12月18-19日,由中国行政区划与区域发展促进会*(以下简称促进会)主办,中国科学院地理科学与资源研究所(以下简称地理资源所)承办的“中国行政区划与区域发展促进会第三次会员代表大会暨2021年学术年会”,以线上腾讯会议的方式举行,来自国内外近百所教学科研机构的专家学者、学生及各界研究人员500余人线上参会.大会会期一天半,分为会员代表大会和2021年学术年会两大板块.
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