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Abstract:In the Youjiang basin, South China, numerous sediments-hosted micro-disseminated gold (SMG) deposits occur mainly in Permian-Triassic chert and siliciclastic rocks. Systematic geological, fabric and geochemical researches were carried out. The Youjiang basin is a Devonian-Triassic rift basin on the southern margin of the Yangtze Craton in South China. Strong syndepositional faulting defined the basin-and- range style paleo-topography that further developed into isolated carbonate platforms surrounded by siliciclastio-filled depressions. SMG ores are often auriferous sedimentary rocks with relatively low sulfide contents and moderate to weak alteration. Most of the SMG deposits are remarkably distributed around the carbonate platforms. Accordingly, there are platform- proximal and platform-distal SMG deposits. In the ores and host rocks there are abundant synsedimentary-syndiagenetic fabrics such as lamination, convolute bedding, slump texture, and soft-sediment deformation, indicating submarine hydrothermal deposition and syndepositional faulting. Numerous fluidescape and liquefaction fabrics imply strong fluid migration during the evolution of sedimentary basin. Magmatic intrusive rocks are rarely found in Youjiang region. Such large-scale geological and fabric evidence implies that SMG ores were formed during basin evolution, probably in connection with basinal fluids. The isolated carbonate platform ( as abasin paleo-high) and related syndepositional fault system, together with the unconformity- related facies succession, may have controlled the migration pathway of ore-forming basinal fluids and subsequently determined the location of SMG deposits in the Youjiang basin. SMG mineralization in the Youjiang basin may represent an integral aspect of the dynamic evolution of extensional basins along divergent continental margins. Geochemical study supports this model to various degrees.
keywords:Micro-disseminated gold, carbonate platform, syndepositional faulting, basinal fluids, Youjiang basin
.2001.Relationship Betvveen Sediments-hosted Micro-disseminated Gold Deposits and Basin Evolution: Case Study in Youjiang Basin, South China[J].Mineral Deposits20(4):367~377