青海驼路沟钴(金)矿床成矿物质来源的黄铁矿氦氩硫铅同位素示踪  

Helium,Argon,Sulfur and Lead Isotope Tracing for Sources of Ore-forming Material in the Tuolugou Cobalt (Gold) Deposit,Golmud City, Qinghai Province,China

作　　者：丰成友[1] 佘宏全[1] 张德全[1] 李大新[1] 李进文[1] 崔艳合[1] 

机构地区：[1]中国地质科学院矿产资源研究所

出　　处：《地质学报》2006年第9期1465-1473,共9页Acta Geologica Sinica

基　　金：国家重点基础研究规划"973"项目(编号2002CB412609);国家自然科学基金项目(编号40302019)资助的成果

摘　　要：为查明青海驼路沟新型独立钴(金)矿床的成因和成矿物质来源,文章对矿区发育的块状、条带状和浸染状黄铁矿矿石进行了黄铁矿流体包裹体氦氩同位素和黄铁矿硫、铅同位素测试。结果表明,不同类型矿石的成矿流体氦、氩同位素组成基本一致,3He/4He介于0.10~0.31Ra(平均0.21Ra),40Ar/36Ar比值为302~569(平均373),反映钴矿化流体主要来源于在赋矿岩系中深循环的大气降水;矿石黄铁矿硫同位素值分布集中且接近于零,δ34S变化于-4.5‰^+1.5‰,集中在-1.8‰^-0.2‰,显示深部来源;矿石铅以高放射性成因为特征(206Pb/204Pb>19.279、207Pb/204Pb>15.691、208Pb/204Pb>39.627),且自地层围岩→区域早古生代火山岩→矿石依次明显增大,可能指示高放射性成因矿石铅主要是由以深循环大气降水来源为主的热液不断从围岩地层中淋取而来。In order to study the genesis and sources of ore-forming material in the newly discovered Tuolugou cobalt （gold） deposit in Qinghai Province, this paper analyzed the helium and argon isotopic compositions of fluid inclusions, and sulfur and lead compositions in pyrite from massive, banded and disseminated ores. The result indicates that helium and argon isotopic compositions of the Tuolugou cobalt （gold） deposit are consistent. The 3He/4He ratios are 0.10 to 0.31Ra with a mean of 0.21 Ra, the ^40Ar/^39Ar ratios vary from 302 to 569 with a mean of 373, indicating that ore fluids were deeply circulating meteoric water. Near zero δ^34S values of pyrite concentrating in the range of --1.8‰ to --0.2‰ indicate a deep source for S and largely exhalative origin. Lead isotope of ores is characterized by high radioactivity with 2^206Pb/^204pb〉 19. 279, ^207Pb/^204Pb〉 15. 691 and ^208Pb/^204pb〉 39. 627. Moreover, the lead isotope ratios increase from wall-rocks, through regional volcanic rocks to ores, it is inferred that the ore lead was leached predominantly from wall-rocks by deeply circulating meteoric water.

关 键 词：氦氩硫铅同位素 成矿物质来源 黄铁矿 大气降水 钴矿床 青海驼路沟 

分 类 号：P618.51[天文地球—矿床学]