The disseminated gold deposits in southwestern Guizhou: mineralization model and its correlation with oil-generation theories

The disseminated gold deposits in southwestern Guizhou are hosted in the claystones,siltstones and impure carbonate rocks of the Permian to Triassic strata in the transitional zones between the semi-restricted platform and platform-margin shoal oolitic limestones,isolated platform margins and basinal turbidites.The ore-controlling structures are represented by the axes of anticlines and their plunging ends,interformational and intraformational faults or karst unconformities and the fractured structures associated with anticlines.The ore-forming flows include formation water,(hydrothermal brines) or oil-field water trapped during deposition and diagenesis.The source rocks were initiated during deposition.And during diagenesis,gold,mercury,antimony and arsenic elements were removed together with the fluids from the strata under the conditions of compression and high temperatures.Subsequent tectonic activity resulted in the generation of accommodation spaces such as anticlines and faults,variations in pressure equilibrium conditions,and migration and trapping of ore-forming fluids.The weathering and erosion of the trapped structures during epidiagenetic stages,in turn,gave rise to the physical and chemical changes of the ore-bearing fluids.Finally these fluids were concentrated and precipitated to form gold deposits.