Characteristics of the superlarge Yangshan Carlin and Carlin-like compound type gold deposit in Gansu

Abstract：The Yangshan gold deposit is a very finely disseminated gold deposit, which was explored at the turn of the century and expanded into a superlarge deposit. The deposit was controlled by superposition and modification of many factors such as strata, hypabyssal granite-porphyry, brittle-ductile shear and hydrothermal activities. The gold deposit has the characteristics of both Carlin type and Carlin-like type mineralization. The Carlin-type mineralization occurred during the early, early-middle and late stages of ductile shearing, when there appeared the As-bearing pyrite-arsenopyrite-submicroscopic gold-dolomite-quartz assemblage and pyrite-stibnite-quartz-calcite assemblage, as well as the Au-As-Sb-Hg geochemical assemblage. The Carlin-like type mineralization took place during the middle-late stage of brittle shearing, which is characterized by the pyrite-arsenopyrite-native gold-tellurobismuthite-submicroscopic gold-dolomite-quartz assemblage (with chalcopyrite, chalcopyrite and chalcopyrite) and the Au-As-Cu-Pb-Zn-Te-Bi geochemical assemblage. The δ34S values are -24.6‰ to -29.0‰ for sedimentary diagenetic pyrite in ore-bearing strata of the gold deposit, 5.0 to 7.0‰ for the metal sulfide formed during the early and early-middle stage of brittle-ductile shearing and -2.9 to -2.1‰ for the metal sulfide in altered granite porphyry of the middle-late mineralization stage, suggesting the multi-source features of mixing with biogenic sulfur in strata, crustal sulfur in strongly deformed orogenic belts and a little magmatic sulfur. The hydrogen and oxygen isotopes in fluid inclusions show nearly sympathetic variations with δ34S, and hydrothermal ore fluids are the mixture of underground fluids, strongly modified meteoric water and a little magmatic water.