Elements' migration during ore-forming process, Yata gold deposit, Southwestern Guizhou, China

Located at Youjiang basin, southwest margin of Yangtze block, the Yata gold deposit is a Carlin-type gold deposit hosted by a series of Triassic thick basin-face flysch formation and controlled by the high angle thrust-fault system. Based on detailed study of relationship of ore minerals and alteration, the ore-forming process of Yata gold deposit can be divided into three stages, including the Fe-dolomite-pyrite stage, the dolomite-pyrite-jasperoid-polymetallic minerals stage, and the asenopyrite-orpiment-realgar-calcite-quartz stage. In order to figure out the elements’ migration during ore-forming process, we have collected samples with different degrees of mineralization and conducted mass balance quantitative calculation using Isocon graphic method. The results show that mineralization is companied by clear increase of SiO₂ content and decrease of CaO content, which represents the existence of ore-related silification and decarbenation. The contents of K₂O and TFe₂O₃ change with slight fluctuation, suggesting the deposition of gold-bearing pyrite and clay minerals. The average contents of TiO₂ and Al₂O₃ are stable and relatively high in different stages. As, Sb, W, Hg, Ag, Cu, Zn, and Tl have showed intimate relationship in mineralization while trace elements migrate between host rock and ore-fluid during fluid-host rock reaction, polymetallic minerals e.g. chalcopyrite, sphalerite, routhierite are deposited while gold entered the crystal framework of As-pyrite as Au(HS)⁰ or Au(HS)^2-.