Ore-forming Fluids And Genesis Of The Dongchuan Copper Deposit, Yunan Province

The Dongchuan copper deposit in Yunnan is located in the Kunyang rift on the western margin of the Yangtze Block.The Dongchuan region has experienced complex geological evolution,favorable metallogenic conditions,and received extensive attention of geoscientists as one of the important production of copper resources in China.Based on lithology,geochemistry,microthermometry,Laser Raman Spectroscopy,achievements has made to undersand the ore-forming fluid and genesis of the Dongchuan copper deposit:?1?The Dongchuan copper deposit is obviously stratabound,and ore bodies are hosted in the mainly exists sandstone and breccia Xikuangshan-type copper-iron deposit in the Yinmin Formation,sandy dolomite of the Dongchuan-type copper deposit in the Luoxue Formation,and carbonaceous slate of the Taoyuan-type copper deposit in the Heishan Formation.?2?Metal minerals of the Xikuangshan-type ore are chalcopyrite,bornite,magnetite,specularite,pyrite,with chalcopyrite,bornite,chalcocite in the Dongchuan-type ore,and chalcopyrite and minor bornite in the Taoyuan-type ore.?3?The ore-forming fluids of the Xikuangshan-type ore are medium temperature and high salinity fluids,with medium-low temperature and medium-high salinity fluids of the Dongchuan-type ore and low temperature and medium salinity fluids of the Taoyuan-type ore.The ore-forming fluids are the Na⁺?K⁺?Ca²⁺—SO₄^2-?Cl^-?type,with organic gases.They have similarities to some extent.The anhydrite found in the ore-forming fluid inclusion of the Xikuangshan-type ore is the product of the dissolution of gypsum rock of the Yinmin Formation.?4?The ore-forming fluids of the Dongchuan copper deposit transport by the fracture structure and concentrate and mineralize along particular strata in the reducing environment.The Dongchuan copper deposit resulted from multi-stage epigenetic enrichment,the embodiment of the same metallogenic system in different layers.?5?The Dongchuan copper deposit has a high similarity with the world's typical marine sandstone deposits in metallogenic elements,mineral combinations,host rocks,ore body morphology,ore-forming fluid characteristics.This paper suggensts that the Dongchuan copper deposit is a marine sandstone deposit.