湖南古台山金锑矿床成矿流体He-Ar、Sr同位素地球化学及深部找矿意义  

He-Ar-Sr Isotope Geochemistry of Ore-forming Fluids in the Gutaishan Au-Sb Deposit in Hunan Province and Its Significance for Deep Prospecting

作　　者：孙骥 周超 陆文 郭爱民 肖荣 隗含涛 谭仕敏 贾朋远 SUN Ji;ZHOU Chao;LU Wen;GUO Ai-min;XIAO Rong;WEI Han-tao;TAN Shi-min;JIA Peng-yuan(Hunan Institute of Geological Survey,Changsha,Hunan 410116;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037;School of Geosicences and Info-physics,Central South University,Changsha,Hunan 410083)

机构地区：[1]湖南省地质调查院,湖南长沙410116 [2]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [3]中南大学地球科学与信息物理学院,湖南长沙410083

出　　处：《地球学报》2020年第2期267-279,共13页Acta Geoscientica Sinica

基　　金：国家重点研发计划“深地资源勘查开采”重点专项课题(编号:2017YFC0601506);湖南省自然资源厅科研项目(编号:2017-03;2019-02);湖南省地质院科研项目(编号:201701,2017-01-01,201902-01,201912)联合资助。

摘　　要：古台山矿床是雪峰弧形构造带中段颇具代表性的石英脉型金锑矿床。矿床位于白马山复式岩体的外接触带,主要赋存于南华系长安组和板溪群五强溪组。本文对古台山矿床载金矿物毒砂流体包裹体氦、氩同位素和含矿石英流体包裹体铷、锶同位素进行了分析。He-Ar同位素分析显示,成矿流体的3He/4He为0.011~0.038 Ra,40Ar/36Ar值为414.4~732.6,表明成矿流体主要为地壳流体,同时有部分大气降水的加入。Sr同位素分析显示,含矿石英流体包裹体87Rb/86Sr变化于0.013~0.956,87Sr/86Sr变化于0.72529~0.73245;利用前人获得的成矿年龄(223.6 Ma)进行了初始锶同位素组成的返算,获得其ISr-223.6变化于0.72360~0.73167,平均0.72744。通过与印支期白马山岩体、板溪群等相关地质体锶同位素组成对比,认为古台山矿床成矿流体不可能单独来源于岩浆,而是岩浆流体运移过程中与来自基底具有高锶同位素比值的碎屑岩水岩相互作用的结果。He-Ar同位素揭示矿区深部及周缘地区板溪群具有更好的资源潜力。The Gutaishan quartz vein type gold-antimony deposit is a representative deposit in the middle of Xuefeng arc structure belt.The deposit,located in the external contact zone of Baimashan composite granite mass,is hosted within Nanhua Changan Formation and Qingbaikouan Wuqiangxi Formation.This paper reports He-Ar and Sr isotopic data of fluid inclusions trapped by arsenopyrite and quartz,respectively.It is shown that the 3He/4He ratios are in the range of 0.011~0.038 Ra,and 40Ar/36Ar ratios vary from 414.4 to 732.6.The results suggest that the ore-forming fluids were dominated by continental crust fluids and some meteoric water in the metallogenic process.87Rb/86Sr ratios are in the range of 0.013~0.956,and 87Sr/86Sr ratios are in the range of 0.72529~0.73245.Calculation shows that the initial 87Rb/86Sr ratio was 223.6 Ma(i.e.ISr-223.6)when the deposit was formed.The ISr-223.6 values range from 0.72360 to 0.73167,with an average of 0.72744.A comparison with the associated lithologies of Baimashan granite mass,Banxi Group and Lengjiaxi Group shows that the ore-forming fluids could not merely sourced from the Indosinian granitoids.Instead,it is shown that Indosinian granitoids provided ore fluids which upwardly moved and interacted with the underlying sedimentary rocks to form the Gutaishan Au-Sb deposit.The isotope geochemical characteristics of He-Ar reveal that,in prospecting for resources in Banxi Group,the underlying strata of the Chang’an Formation have better potential than the upper strata.

关 键 词：深部找矿 HE-AR同位素 SR同位素 成矿流体来源 古台山金锑矿床 雪峰弧形构造带 

分 类 号：P595[天文地球—地球化学]