云南白马寨铜镍硫化物矿床铂族元素地球化学及其对矿床成因的制约  

Platinum Group Elements (PGE) Geochemistry of Baimazhai Ni-Cu Sulfide Deposit and Its Constraints on the Ore Genesis

作　　者：王生伟[1] 孙晓明[1] 石贵勇[1] 熊德信[1] 翟伟[1] 

机构地区：[1]中山大学地球科学系,广州510275

出　　处：《地质学报》2006年第9期1474-1486,共13页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划"973"项目(编号2002CB412610);国家自然科学基金项目(编号40173025);国家教育部跨世纪优秀人才培养计划基金;南京大学壳幔演化与成矿作用国家重点实验室开放基金资助的成果

摘　　要：采用镍硫火试金ICP—MS法分析了白马寨铜镍硫化物矿床矿石及其主要围岩铂族元素（PGE）含量，结果表明铂族元素总量（EPGE）普遍较低，且EPGE由矿床核部的块状矿石（78．15×10^-9～555．92×10^-9）向外围矿化橄榄岩（6．77×10^-9～70．95×10^-9）至辉长岩（3．02×10^-9）逐步降低。煌斑岩脉岩的EPGE也较低，为6．86×10^-9～17．03×10^-9。ΣPGE与Ni含量呈明显的正相关。不同种类岩石和矿石的PGE原始地幔配分模式明显不同，块状矿石为PtPd配分型，Ir较明显亏损；矿化橄榄岩配分曲线较平坦，IPGE和PPGE分异不明显，但均出现Ru正异常。辉长岩样品和煌斑岩PGE配分模式几乎一致，也均出现明显的Ru正异常。矿石和围岩的Cu／Pd值远高于原始地幔，表明原生岩浆发生了较强的硫化物熔离作用。块状富镍矿石的（Pt＋Pd）／（Os＋Ir＋Ru）和Pd／Ir分别为138．24和24．7，指示其母岩浆为演化较为彻底的玄武质岩浆，而矿化橄榄岩的相应值分别为3．02和16．09，具有科马提质岩浆的特征参数，因此白马寨块状矿石和矿化橄榄岩之间可能没有成因联系。块状硫化物熔体侵位前，其母岩浆经历过长时间强烈的硫化物熔离作用，硫化物熔浆作为独立的侵入相而侵入于III号岩体核部。这个过程反映了峨眉山地幔柱尾部岩浆演化和成矿可能经历过高度的S饱和过程。白马寨矿床形成过程中可能受到地壳物质的混染。Concentrations of platinum group elements （PGE） of ores and related rocks from Baimazhai Ni-Cu sulfide deposit were determined by using an ICP-MS with nickel sulfide fire assay pre-concentration. The results show that the total PGE （EPGE） in the Baimazhai ores and the around rocks are quite low, which decreases gradually from central massive ores （78.15 × 10^-9-555.92 × 10^-9） to the mineralized peridotite （6.77× 10^-9 70.95 × 10^-9） and gabbro （3.02 × 10^-9）. The lamprophyre dykes also show low Y.PGE （6.86 × 10^-9- 17.03 × 10^-9 ）. Besides, the ΣPGE show obvious direct correlation with Ni contents. Primitive mantle normalized PGE patterns of various rocks and ores from Baimazhai mine are quite different, the massive ores possess Pt-Pd type with relatively Ir depleted patterns, while the mineralized peridotite show relatively flat with positive Ru patterns. The gabbro and lamprophyre dykes show nearly same PGE patterns with marked positive Ru anomaly. Cu/Pd ratios of the Baimazhai rocks and ores are greatly higher than that of the primitive mantle, implying that the parental magmas might have undergone strong sulfide segregation. （Pd＋Pt）/（Os＋Ir＋Ru） and Pd/Ir ratios of the massive ores are 138.24 and 24.7, indicating that its parental magma is of gabbroic or basaltic and underwent exhaustively complete sulfide segregation. On the contrary, the corresponding ratios of the mineralized peridotite are 3.02 and 16.09 respectively, which are similar to those of komatiitic magma, implying that the massive ores has no genetic relationship with the mineralized peridotite. Before intrusion of the sulfide liquid of massive ores, its parental magma might have undergone long-term and strong sulfide segregation, and the sulfide liquid might have intruded into the core of the rock body No. 3 of the Baimazhai mine as an isolated intrusive phase. The PGE parameters of Baimazhai Ni-Cu deposit suggest that evolution and mineralization of the late part of the Emei mantle plume might have

关 键 词：铂族元素 岩浆铜镍矿床 白马寨 峨嵋大火成岩省 金平 云南 

分 类 号：P618.53[天文地球—矿床学]