Molybdenum isotopic composition as a tracer for low-medium temperature hydrothermal ore-forming systems:A case study on the Dajiangping pyrite deposit,western Guangdong Province,China  

作　　者：SONG ShiMing HU Kai WEN HanJie ZHANG YuXu LI Kuang FAN HaiFeng 

机构地区：[1]State Key Laboratory for Mineral Deposits Research,School of Earth and Engineering,Nanjing University,Nanjing 210093,China [2]State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550002,China [3]Wuxi Research Institute of Experimental Geology,SINOPEC Exploration and Production Research Institute,Wuxi 214000,China

出　　处：《Chinese Science Bulletin》2011年第21期2221-2228,共8页

基　　金：supported by the National Natural Science Foundation of China (40638042, 40572056, 40873014 and 40930425);the "West Light" of the Chinese Academy of Sciences

摘　　要：Little is known about the range or controls on the molybdenum isotopic composition of low-medium temperature hydrothermal ore-forming systems.We present molybdenum isotope data from 12 hydrothermal syndepositional silicalite and carbonaceous slate samples from the Dajiangping pyrite deposit in western Guangdong Province,South China.The δ 97/95Mo values from Orebody III range from ?0.02‰ to 0.29‰,with an average of 0.18‰.In contrast,the composition values from Orebody IV display a larger variation from ?0.70‰ to 0.62‰.However,the five samples from the main ore bed all show strong negative values.This indicates that the significant variation in molybdenum isotopic composition supports different hydrothermal ore-forming metallogenesis and a metallogenic environment between the two orebodies.Orebody III is likely to have been deposited from submarine exhalative hydrothermal fluids under a relatively strong reducing environment and Orebody IV may have also been influenced by hydrothermal superimposition in a more oxidized disequilibrium condition.In addition,the δ 97/95Mo values of Orebody IV are clearly negative,together with the values increasing stratigraphically upward in the ore beds,suggesting that the metallogenic environment of Orebody IV is different from the open oceanic systems.There might be dynamic fractionation in this restricted environment.Therefore,the molybdenum isotope can be used as an effective tracer for the ore-forming fluid and metallogenic environment.Little is known about the range or controls on the molybdenum isotopic composition of low-medium temperature hydrothermal ore-forming systems.We present molybdenum isotope data from 12 hydrothermal syndepositional silicalite and carbonaceous slate samples from the Dajiangping pyrite deposit in western Guangdong Province,South China.The δ 97/95Mo values from Orebody III range from ？0.02‰ to 0.29‰,with an average of 0.18‰.In contrast,the composition values from Orebody IV display a larger variation from ？0.70‰ to 0.62‰.However,the five samples from the main ore bed all show strong negative values.This indicates that the significant variation in molybdenum isotopic composition supports different hydrothermal ore-forming metallogenesis and a metallogenic environment between the two orebodies.Orebody III is likely to have been deposited from submarine exhalative hydrothermal fluids under a relatively strong reducing environment and Orebody IV may have also been influenced by hydrothermal superimposition in a more oxidized disequilibrium condition.In addition,the δ 97/95Mo values of Orebody IV are clearly negative,together with the values increasing stratigraphically upward in the ore beds,suggesting that the metallogenic environment of Orebody IV is different from the open oceanic systems.There might be dynamic fractionation in this restricted environment.Therefore,the molybdenum isotope can be used as an effective tracer for the ore-forming fluid and metallogenic environment.

关 键 词：同位素组成 黄铁矿矿床 热液成矿 成矿系统 中国西部 中高温 广东省 示踪 

分 类 号：P597[天文地球—地球化学]