西藏嘎拉勒铜金矿床成矿物质来源探讨——来自硫、铅、碳和氢氧同位素地球化学特征的证据  

Source of Ore-forming Materials in the Galale Copper-gold Deposit of Tibet: Evidence from Geochemical Characteristics of Sulfur,Lead,Carbon and Hydrogen-Oxygen Isotopes

作　　者：李志军[1] 赵润东[1] 何子轩 张志[2] 李丕蓉[1] 尤孟 何珊[1] 郭奇奇 欧俊 LI Zhi-jun;ZHAO Run-dong;HE Zi-xuan;ZHANG Zhi;LI Pi-rong;YOU Meng;HE Shan;GUO Qi-qi;OU Jun(Chengdu University of Technoloy, Chengdu, Sichuan 610059;Chengdu Center, China Geological Survey, Chengdu, Sichuan 610081)

机构地区：[1]成都理工大学,四川成都610059 [2]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《地球学报》2017年第5期651-658,共8页Acta Geoscientica Sinica

基　　金：中国地质调查局基础性公益性地质矿产调查项目(编号:DD20160026);四川省科技计划项目(编号:2017JY0143);四川省教育厅一般项目(编号:14ZB0062)联合资助~~

摘　　要：西藏嘎拉勒铜金矿床位于班公湖—怒江成矿带西段,是近年来发现的一个大型镁质矽卡岩型铜金矿床。本文在野外地质调查的基础上,通过S-Pb-C-H-O同位素分析,对嘎拉勒铜金矿床的物质来源进行了探讨。结果表明:(1)矽卡岩型矿石中黄铜矿的δ^(34)S_(V-CDT)值在硫同位素直方图上呈塔式分布,变化范围为–4.4‰~6‰,有少许样品值变化范围较大,表明嘎拉勒矿床硫同位素主要以幔源硫为主,有少量壳源的混染;(2)^(208)Pb/^(204)Pb变化范围为38.427‰~39.008‰,^(207)Pb/^(204)Pb变化范围为15.588‰~15.701‰,^(206)Pb/^(204)Pb变化范围为18.330‰~18.871‰,显示矿区铅同位素来源以造山带铅为主,少量上地壳铅相结合的特征;嘎拉勒矿床形成于碰撞的造山带环境;(3)含辉钼矿石英脉中δ^(18)O_(V-SMOW)值范围为12.2‰~12.8‰,平均值12.5‰,δD_(V-SMOW)范围为–103.3‰~–95.3‰,平均值为–99.3‰,δ^(18)O_(V-PDB)值范围为–18.1‰~–17.6‰,平均值为–17.85‰,显示受到大气降水加入明显;(4)矽卡岩中方解石C-O同位素测试结果δ^(13)C_(V-PDB)为–2‰,δ^(18)O_(V-PDB)为–15.1‰,δ^(18)O_(V-SMOW)为15.4‰,显示嘎拉勒铜金矿床碳酸盐为海相碳酸盐并经历了溶解作用。综合表明,嘎拉勒铜金矿床是由幔源成矿流体作用形成的,成矿过程中有大气降水的加入,成矿流体与碳酸盐岩发生接触交代作用形成矽卡岩型铜金矿床。The Galale copper and gold deposit in Tibet is located in the western part of the Bangong Co–Nujiangmetallogenic belt.It is a large-sized magnesia skarn type copper gold deposit discovered in recent years.Based onfield geological survey,the authors investigated the material source of the Galale gold deposit on the basis ofS-Pb-C-H-O isotope analysis.Some conclusions have been reached:①Theδ34SV-CDT values of chalcopyrite inskarn-type ore exhibit tower-type distribution on the sulfur isotope histogram,and the variation range is–4.4‰~6‰,with a few samples showing rather wide variation range.Isotopes are mainly mantle-derived sulfur,with themixture of a small amount of crustal source.②The variation range of208Pb/204Pb ratios is38.427‰~39.008‰,the variation range of207Pb/204Pb ratios is15.588‰~15.701‰,and the variation range of206Pb/204Pb ratios is18.330‰~18.871‰,which indicates that the lead isotopic source in the mining area was dominated by orogeniclead.The crustal lead is characterized by the combination;the Galale deposit was formed in a collisional orogenicenvironment;③Theδ18OV-SMOW range in the quartz vein is12.2‰~12.8‰,with an average value of12.5‰,whereas theδDV-SMOW values vary from–103.3‰to–95.3‰,with an average of–99.3‰;δ18OV-PDB values varyin the range of–18.1‰~–17.6‰,with an average value of–17.85‰,indicating that the precipitation wassignificant.④The isotope analytical results of calcite in skarn areδ13CV-PDB of–2‰,δ18OV-PDB of–15.1‰andδ18OV-SMOW of15.4‰,which shows that the carbonate of the Galale copper-gold deposit was marine carbonateand experienced the dissolution.It is shown that the Galale copper-gold deposit was formed by the mantle-derivedore-forming fluid,and the meteorite was added in the mineralization process.The ore-forming fluid interactedwith the carbonate rocks to form the skarn-type copper-gold deposit.

关 键 词：班公湖-怒江成矿带西段 同位素地球化学 幔源物质 矽卡岩型 铜金矿床 嘎拉勒 

分 类 号：P618.41[天文地球—矿床学] O611.7[天文地球—地质学]