金川岩浆铜镍(铂)硫化物矿床铂族金属富集过程及富集机制  

Enrichment processes and mechanism of platinum group element in Jinchuan magmatic Cu-Ni(PGE)sulfide deposit

作　　者：陈学根 苏尚国[1] 施南 王跃 张雅南 郝金华 刘翠[1] 杨宗锋[1] CHEN Xuegen;SU Shangguo;SHI Nan;WANG Yue;ZHANG Yanan;HAO Jinhua;LIU Cui;YANG Zongfeng(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083

出　　处：《地质学报》2023年第11期3715-3736,共22页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号92162213)资助的成果。

摘　　要：金川岩浆铜镍(铂)硫化物矿床是我国最主要的铂族等战略性关键金属宝库。金川矿床中铂族金属的富集过程和富集机制还存在很多争论。本文通过详细的矿物学及矿床学研究,厘定了金川矿床成矿阶段。成矿阶段可划分为硫化物矿浆结晶阶段、挥发分流体作用阶段及热液改造阶段。其中硫化物矿浆结晶阶段的主要矿物组合为镍黄铁矿(Pn-a)-磁黄铁矿(Po-a)-黄铜矿(Ccp-a);挥发分流体作用阶段的主要矿物组合为镍黄铁矿(Pn-b)-磁黄铁矿(Po-b)-黄铜矿(Ccp-b)-黄铁矿(Py-Ⅰ)-磁铁矿(Mag-Ⅰ)-菱铁矿-叶蛇纹石-磷灰石-铬铁矿-白云石-方解石(Cal-Ⅰ)-金云母。热液改造阶段的矿物组合为透闪石-绿泥石-蛇纹石-方解石(Cal-Ⅱ)-磁铁矿(Mag-Ⅱ)。高倍电子探针镜下发现,金川矿床铂族矿物与磁铁矿(Mag-Ⅰ)、黄铁矿(Py-Ⅰ)、铬铁矿、磷灰石、黄铜矿、磁黄铁矿、镍黄铁矿及菱铁矿等共生。金川铜镍硫化物矿床中铂族元素(PGM)矿物主要包括硫砷铱矿(IrAsS)、钯的铋化物、碲化物和硒化物、钯的金属互化物(PdAu_(2))、砷铂矿(PtAs_(2))、铂单质以及铂的金属合金(Pt-Fe)。其中大量的PGM分布于镍黄铁矿的裂隙中,或产于镍黄铁矿、磁黄铁矿及蛇纹石裂隙中。与磁铁矿、菱铁矿、铬铁矿、黄铜矿、磷灰石以及叶蛇纹石等矿物共生,指示PGE富集与氧化性流体加入密切相关。金川矿石镍黄铁矿(Pn-b)、磁黄铁矿(Pob)、黄铜矿(Ccp-b)、黄铁矿(Py-Ⅰ)、磁铁矿(Mag-Ⅰ)以及菱铁矿中高Co含量,表明流体在Co的超常富集过程中也起到了决定性作用。金川矿石中大量碳酸盐矿物、叶蛇纹石、金云母、磁铁矿、黄铁矿、铬铁矿以及富Cl磷灰石的出现;S、Mg元素呈网脉状分布于蚀变橄榄石和硫化物中,推测流体组分可能是一种富C富Cl的富含挥发分的高氧逸度流体。金川铬铁矿、磁铁矿(Ⅰ)、菱铁矿等矿物中高Ti、高Nb含The Jinchuan magmatic Cu-Ni(PGE)sulfide deposit is the most important strategic metal treasurehouse of platinum group.The enrichment process and mechanism of platinum group metals(PGEs)in Jinchuan deposit are still controversial.Based on detailed mineralogical and deposit studies,it is found that the mineralization stage of Jinchuan deposit can be divided into sulfide melt crystallization stage,interaction stage of volatile fluid-sulfide melt and hydrothermal alteration stage.The mineral paragenetic assemblages in the sulfide melt crystallization stage are pentlandite(Pn-a)+pyrrhotite(Po-a)+chalcopyrite(Ccp-a).The mineral paragenetic assemblages in the interaction stage of volatile fluid-sulfide melt are pentlandite(Pn-b)+pyrite(Py-Ⅰ)+chalcopyrite(Ccp-b)+magnetite(Mag-Ⅰ)+siderite+serpentine+apatite+dolomite+calcite(Cal-Ⅰ)+phlogopite.In the hydrothermal alteration stage,the mineral paragenetic assemblages are tremolite+chlorite+serpentine+calcite(Cal-Ⅱ)+magnetite(Mag-Ⅱ).It is found that platinum group minerals are paragenetic with magnetite(Mag-Ⅰ),pyrite(Py-Ⅰ),chromite,chalcopyrite(Ccp-b),apatite,pentlandite,pyrrhotite and siderite in Jinchuan deposit under high-power electron probe microscopy.The study of PGMs in Jinchuan Cu-Ni sulfide deposit shows that the types of PGM include sulfoarsenide(IrAsS),bismuth of palladium,telluride and selenide of palladium,metal complexes of palladium(PdAu2),platinum and its metal alloy(Pt-Fe).Among them,most PGMSs are distributed in the cracks of pentlandite,pyrrhotite and altered olivine,and paragenetic with magnetite,siderite,chromite,chalcopyrite,apatite and antigorite,indicating that PGE enrichment is closely related to fluid addition.The high contents of Co in Pn-b,Ccp-b,Py-Ⅰ,Mag-Ⅰand siderite in Jinchuan ores indicates that fluid also plays a decisive role in the super-enrichment of Co.The occurrence of a large number of carbonate minerals,antigorite,phlogopite,magnetite,pyrite,chromite and Cl-rich apatite in the Jinchuan ores,S and Mg elements are distrib

关 键 词：金川 Cu-Ni(PGE)硫化物矿床 铂族金属 富集过程 富集机制 

分 类 号：P618.2[天文地球—矿床学]