南秦岭铧厂沟金矿床硫、铅同位素组成特征与金属物质来源探讨  

Characteristics of sulfur and lead isotopic compositions and its constraints for metal source of Huachanggou Gold Deposit,South Qinling

作　　者：林振文 秦艳[2] 庄文明[1] 岳素伟 周振菊 郭峰[1] LIN Zhen-wen;QIN Yan;ZHUANG Wen-ming;YUE Su-wei;ZHOU Zhen-ju;GUO Feng(Guangdong Marine Geological Survey,Guangzhou 510080,China;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Guangzhou College of South China University of Technology,Guangzhou 510800,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)

机构地区：[1]广东省海洋地质调查院,广东广州510080 [2]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [3]华南理工大学广州学院,广东广州510800 [4]中国地质科学院地质力学研究所,北京100081

出　　处：《地球化学》2020年第1期62-75,共14页Geochimica

基　　金：国家自然科学基金(41502070,41403032)。

摘　　要：铧厂沟金矿床赋存于新元古界碧口群细碧岩和泥盆系踏坡群灰岩中。矿体受高角度逆冲断层和韧-脆性剪切带控制,呈似层状、透镜状产出,是南秦岭典型的造山型金矿床。根据赋矿围岩不同,该矿床划分为细碧岩矿带和灰岩矿带。细碧岩矿带矿石中黄铁矿的δ^34S值范围为-1.3‰~4.7‰,呈塔式分布,具岩浆硫特征;灰岩矿带矿石中黄铁矿的δ^34S值为-14.8‰~1.9‰,离散度强,具有生物成因硫和地层硫的特征。矿石黄铁矿的δ^34S值均落入碧口群细碧岩(2.1‰~4.7‰)和踏坡群(-22.5‰~6.6‰)的δ^34S值范围,指示硫源主要为碧口群和踏坡群。Pb同位素组成中,细碧岩矿带矿石中黄铁矿206Pb/204Pb、207Pb/204Pb和208Pb/204Pb范围分别为18.017~17.856、15.530~15.585和38.150~38.413,灰岩矿带矿石中黄铁矿206Pb/204Pb、207Pb/204Pb和208Pb/204Pb范围分别为18.202~18.491、15.624~15.659和38.690~39.401。细碧岩矿带矿石黄铁矿与围岩细碧岩全岩的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb值相近,灰岩矿带矿石黄铁矿Pb同位素投影点全部落入踏坡群灰岩地层范围内。以上S和Pb同位素结果表明,铧厂沟金矿床金属物质来源于新元古代碧口群细碧岩及泥盆系踏坡群。The Huachanggou gold deposit,found in the spilite of the Neoproterozoic Bikou Group and limestone of the Devonian Tapo Group,is a typical orogenic gold deposit in South Qinling.Bedded and lenticu lar ore bodies are restricted to high-angle reverse faults or ductile-brittle shear zones.Based on the differences of wall-rocks,two orebody types are present:spilite-hosted Au lodes and limestone-hosted Au lodes.The sulfur isotope studies indicate that theδ^34S values of the pyrite from the spilite-hosted Au lodes range from-1.3‰~4.7‰,distributed in a tower-like shape,which is suggestive of the mixing source of the sulfur.Theδ^34S values of the pyrite from the limestone-hosted Au lodes range from-14.8‰~1.9‰,with a high discretization,suggesting that the sulfur was mainly sourced from bioclastic limestone strata.The 206Pb/204Pb,207Pb/204Pb,and 208Pb/204Pb ratios of the pyrite from the spilite-hosted Au lodes range within 18.017–17.856,15.530–15.585,and 38.150–38.413,respectively,while those from limestone-hosted Au lodes range within 18.202–18.491,15.624–15.659,and 38.690–39.401,respectively.The 206Pb/204Pb,207Pb/204Pb,and 208Pb/204Pb ratios of the spilite and pyrite from the spilite-hosted Au lodes are similar;both of them,together with the pyrite from the limestone-hosted Au lodes,lie on the same lines in the diagrams of 208Pb/204Pb vs.206Pb/204Pb and 207Pb/204Pb vs.206Pb/204Pb.For the mixing line,the two end members are spilite and an orogenic belt,respectively.All the evidence indicates that the metallogenic elements are sourced from the spilite of the Neoproterozoic Bikou Group and Devonian Tapo Group.

关 键 词：硫、铅同位素 金属物质来源 铧厂沟金矿床 造山型金矿床 南秦岭 

分 类 号：P597[天文地球—地球化学]