Geology And Geochemistry Of Hydrothermally Altered Deformed-Rock Type Ag-Au Deposits And Their Resource Potential

The Pangxidong-Jinshan Ag-Au mineralization belt is located along the boundary zone of Guangdong and Guangxi,southern Chnia,It is part of the famous Yunkai metamorphic block in term of tectonics. The latter has a Au-Ag-rich basement,and the studied Lianjiang - Bobai region is specially high in the ratio of Ag/Au in contrast with other areas of the Yunkai block.The Ag-Au deposits are distributed along the Pangxidong-Jinshan fault system,and compsed mainly of hydrothermally altered deformed-rocks and quartz veins. There are four mineralization phases,including the silicification - quartz phase (I),the quartz - pyrite phase (II),the multiple metallic sulfide phase (III) and the quartz-calcite phase (IV). Si and Ag,Au and the like are included among the introduced elements during hydrothermal wall-rock alteration .The deposits resulted from multiple phases of geological and geochemical evolution. A source formation rich in noble metals was formed during the Precambrian-Cambrian period,and the mineralization elements were redistributed with the source rocks during the Jinning and Caledonia regional metamorphic period. Magmatism and deformatiom were developed during the Yanshan stage,followed by hydrothermal alteration,of which final mineralization is an integral part.The regional abundance method and the fractal model are used to estimate the resource potentiality of noble metals in the studied region,and the result indicates that the region has a sound prospect in reserve of Ag and Au.