试论与布什维尔德杂岩体有关的铂族元素-铬铁矿矿床成矿系列及其对中国西南部的意义

    THE PLATINUM GROUP ELEMENT CHROMITE METALLOGENIC SERIES RELATED TO THE BUSHVELD COMPLEX IN SOUTH AFRICA: its inspiration to exploration for PGE in Southwest China

    • 摘要: 布什维尔德杂岩体中铂族元素成矿作用具有多样性的特点,既有主岩体岩浆结晶分异形成的UG2和Merensky层,有晚期小岩体结晶分异产生的块状铜镍硫化物矿石中伴生的铂族元素矿床(如Nkomati),也有岩体侵入过程中产于接触带的热液成因硫化物-铂族元素矿床(如Potgietersrust),以及岩筒型矿床(如Mooihoek和Driekop)、剪切带热液型硫化物矿床(如TweefonteinHill)和石英脉型铂族元素矿床.这些矿床虽然产出部位不同(矿体可以分布在岩体内部也可以出现在接触带甚至远离岩体),矿石类型也不同(有的是铬铁矿型,有的是硫化物型,有的是硅酸盐型,甚至还有石英脉型),但铂族元素的富集都与布什维尔德基性超基性岩杂岩体密切有关,实际上构成一个完整的由布什维尔德地幔柱形成的矿床成矿系列。类似的矿床成矿系列在深受峨眉地幔柱影响的我国西南部地区也存在,这对于在我国寻找多种类型的铂族元素矿床无疑具有重要的启示意义.除了金宝山和杨柳坪等地的岩浆型铂矿外,近年来在杨柳坪、大岩子等地也先后发现了热液型铂族元素矿床.

       

      Abstract: Multi-types of PGE mineralization have been proved to be associated with the Bushveld complex in South Africa, including the UG2 and Merensky reefs formed by crystallization and differentiation of the major magma body,the massive sulfide Cu-Ni-PGE deposits related to small intrusive bodies of later stage such as the Nkomati deposit,the hydrothermal sulfide-PGE deposits formed in contact zone such as the Potgietersrust deposit,as well as pipe-type PGE deposits such as the Mooihoek pipe and the Driekop pipe, shear zone-type of hydrothermal PGE deposits such as the Tweefontein hill deposit, and quartz vein-type PGE deposits such as the Naboomspruit deposit. Even these deposits show different modes of geological occurrences (within mafic-ultramafic rocks, at contact zone, or even in shear zone or quartz vein away from the main intrusive complex) and different types of ores (chromite-type, massive sulfide-type, silicate-type, or quartz vein-type), the enrichment or mineralization process of PGE was genetically related to the Bushveld mafic-ultramafic complex and resulted in a metallogenic series of PGE deposits, chromite deposits, massive sulfide Cu-Ni-PGE deposits, asbestos deposits, magnesite deposits and other kinds of deposits. This metallogenic series of PGE-Cu-Ni-Cr deposits were originated from the Proterozoic Bushveld mantle plume. It provides a good lesson to the exploration of new types of PGE deposits in Southwest China, where exist similar metallogenic series of PGE-Cu-Ni deposits formed on the western margin of the Yangtze platform and genetically related to the Emei mantle plume of Paleozoic. Besides the magma type PGE deposits at Jinbaoshan and Yangliuping, hydrothermal deposits have also been found recently in Yangliuping, Dayanzi and other areas.

       

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