胶东金矿床碳酸盐矿物的碳-氧和锶-钕同位素地球化学研究  

C-O and Sr-Nd isotopic geochemistry of carbonate minerals from gold deposits in East Shandong, China.

作　　者：刘建明[1] 叶杰[1] 徐九华[2] 孙景贵[3] 沈昆 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]北京科技大学,北京100083 [3]吉林大学地球科学院,长春130061 [4]山东省地质科学实验研究院,济南250013

出　　处：《岩石学报》2003年第4期775-784,共10页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程重大项目(KZCX1-07)的研究成果;国家自然科学基金(49873022);科技部基础研究重大项目(G1999043210)的资助

摘　　要：对胶东四类金矿床(盆地边缘砾岩型、斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型)矿石中的碳酸盐矿物开展了系统的碳-氧同位素和锶-钕同位素地球化学研究。研究结果表明,与宏观的成矿地质条件和矿床地质特征相对应,山东金矿床可能有亲岩浆岩和亲沉积盆地两个不同的成矿系统。前者包括斑岩型-浅成热液型、石英脉型和破碎带蚀变岩型三类金矿床,后者指盆地边缘砾岩型金矿床,二者具有不同的碳-氧和锶-钕同位素地球化学特征。山东亲岩浆岩系列的金矿床。其锶-钕同位素与同时代的幔源岩浆岩一致,碳同位素显示幔源碳和岩浆碳的特征,氧同位素则显示初生水与大气降水不同比例混合的可能性,因此有可能是以CO-2为主、富含成矿金属的地幔流体与浅部下渗大气降水相互作用的结果。而与岩浆岩关系不密切、主要受盆地边缘断裂控制的盆地边缘砾岩型金矿床,其碳-氧和锶-钕同位素组成均较分散,可能主要与地壳浅部下渗 大气降水对上地壳各种岩石淋滤萃取演化而成的成矿流体有关。There are four types of gold deposits in East Shandong: 1) altered breccia-type along basin-marginal faults, 2) porphyryepithermal type, 3) quartz vein type, 4) altered tectonite-type. Systematical research on C-O and Sr-Nd isotopes of carbonate minerals in the four deposit types was carried out. This research demonstrates that, corresponding to geological settings and features of the gold deposits, there might be two ore-forming fluid systems, namely, magma-affinitive and basin-affinitive. The former one is related to porphyry-epithermal type, quartz vein type, and altered tectonite-type, the later one is related to altered gold-bearing breccia-type along basin-marginal faults. They show different C-O and Sr-Nd isotopic characteristics. Carbonate minerals from the magma-affinitive gold deposits manifest similar Sr-Nd isotopic features as the coeval mantle-derived igneous rocks in Shandong, and their carbon isotope compositions exhibit characters of mantle-derived or magma-derived carbon. Their oxygen isotope compositions imply possibility of mixing from primary water and meteoric water. All these together suggest that the ore-forming fluids principally carried characteristics of metal-rich mantle fluids that were probably diluted by circulated meteoric water as the ascending mantle fluids reached the upper part of the crust. The basin-affinitive gold deposits, on the other hand, contain carbonate minerals whose C-O and Sr-Nd isotopic compositions are typically heterogeneous, characteristic of ore-forming fluids resulted from circulating and heated meteoric water that obtained ore-forming materials mainly from fluid-rock interaction during its circulation in the upper part of the crust.

关 键 词：金矿床 碳酸盐矿物 碳-氧同位素 锶-钕同位素 胶东 

分 类 号：P597[天文地球—地球化学] P618.51[天文地球—地质学]