地质学报2023，Vol.97Issue(11)：3715-3736,中插36-中插43,30.DOI:10.19762/j.cnki.dizhixuebao.2023034
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
摘要
Abstract
The Jinchuan magmatic Cu-Ni(PGE)sulfide deposit is the most important strategic metal treasure-house 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-Ⅰ and 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 distributed in olivine and sulfide in net-vein.It is speculated that the fluid component may be a C-rich and Cl-rich fluid with high oxygen fugacity.The high contents of Ti and Nb and Nb/Ta ratio of chromite,magnetite-Ⅰ,siderite and other minerals in the Jinchuan deposit suggest that the fluid may be a high-temperature supercritical fluid.The above characteristics indicate that this fluid plays a key role in controlling the super-enrichment of PGE and other key metal elements in the Jinchuan Cu-Ni sulfide deposit:when the volatile fluid interacted with the residual sulfide melt and altered the preexisting sulfide and olivine,it not only promotes the further activation and enrichment of Os,Ir,Ru,Rh,Pt and Pd,but also leads to the strong enrichment of PGE in the fluid,which increases the content of Pd,Se,Te,Bi and Pt in the fluid,and finally forms most PGMs.In conclusion,we conclude that there may be an acidic,high oxygen fugacity,Cl-rich and C-rich derived from deep mantle fluid in the late stage of magma evolution,which plays a key role in controlling the migration and super-enrichment of PGE and Co.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Key words
Jinchuan/Cu-Ni(PGE)sulfide deposit/platinum group metals/enrichment process/enrichment mechanism引用本文复制引用
陈学根,苏尚国,施南,王跃,张雅南,郝金华,刘翠,杨宗锋..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[J].地质学报,2023,97(11):3715-3736,中插36-中插43,30.基金项目
本文为国家自然科学基金项目(编号92162213)资助的成果. （编号92162213）
