Geological and geochemical characteristics of the Baimazhai Ni-Cu-(PGE) sulphide deposit in Yunnan, China  

作　　者：PU Chuanjie QIN Dexian NIAN Hong ZHANG Xueshu Franco PIRAJNO FAN Zhuguo 

机构地区：[1]Kunming University of Science and Technology, Kunming 650093, China [2]Yunnan Non-Ferrous Metals Geological Bureau, Kunming 650051, China [3]Geological Survey of Western Anstralia, 100 Plain Street, WA 6004, Australia

出　　处：《Chinese Journal Of Geochemistry》2007年第4期374-383,共10页中国地球化学学报

摘　　要：The sulphide ores of the Baimazhai deposit, although typically orthomagmatic, locally exhibit peculiar textural features and are intimately associated with hydrothermal minerals, such as biotite, amphibole and chlorite. This association suggests that the magmatic sulphide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in the observed textural features. Geochemically, the Baimazhai sulphide ores are enriched in Cu, Pd and Au, which,according to previous studies, reflects the action of hydrothermal fluids. Interestingly, Ar-Ar dating yielded the plateau ages of about 160–170 Ma, which are at odds with the established Permian age of the Emeishan large igneous province. We interpreted these younger ages as due to thermal resetting during post-Permian tectonothermal events. We have proposed a model in which tectonic movements and hydrothermal fluids related to these events modified the pre-existing magmatic sulphides. Given the degree of overprint, we suggested two possible scenarios: 1) the sulphide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and 2) there were both magmatic massive and disseminated sulphides, in which case the scale and relocation of remobilization would have been smaller, but still detectable.The sulphide ores of the BaJmazhai deposit, although typically orthomagmatic, locally exhibit peculiar textural features and are intimately associated with hydrothermal minerals, such as biotite, amphibole and chlorite. This association suggests that the magmatic sulphide ores were subjected to hydrothermal alteration and subsequent redistribution, resulting in the observed textural features. Geochemically, the Baimazhai sulphide ores are enriched in Cu, Pd and Au, which, according to previous studies, reflects the action of hydrothermal fluids. Interestingly, At-At dating yielded the plateau ages of about 160-170 Ma, which are at odds with the established Permian age of the Emeishan large igneous province. We interpreted these younger ages as due to thermal resetting during post-Permian tectonothermal events. We have proposed a model in which tectonic movements and hydrothermal fluids related to these events modified the pre-existing magmatic sulphides. Given the degree of overprint, we suggested two possible scenarios： 1） the sulphide disseminations that surround the massive magmatic ores are the result of deformation and hydrothermal alteration; and 2） there were both magmatic massive and disseminated sulphides, in which case the scale and relocation of remobilization would have been smaller, but still detectable.

关 键 词：白马寨 矿化作用 云南 硫化物 

分 类 号：P59[天文地球—地球化学]