Studies on the genesis of adjacent Changkeng gold- and Fuwang silver-deposits, Guangdong Province, China

Abstract

The Changkeng Au- and Fuwang Ag-deposits represent an economically significant and distinct member of the Au-Ag deposit association in China. The two deposits are immediately adjacent, but the Au- and Ag-orebodies separated from each other. Changkeng is hosted in brecciated cherts and jasperoidal quartz and is characterized by disseminated ore minerals. Fuwang, hosted in the Lower Carboniferous Zimenqiao group bioclastic limestone, has vein and veinlet mineralization associated with alteration comprised of quartz, carbonate, sericite, and sulfides. The Changkeng gold and Fuwang silver deposits overlap in homogeneous temperature and salinity of fluid inclusions. The δD_H2O, δ¹⁸O_H2O, δ¹³C_CO2 and ³He/⁴He values of the fluid inclusions suggest the ore fluids of the Changkeng Au-ore come from the meteoric water and the ore fluids of the Fuwang Ag-ore are derived from mixing of magmatic water and meteoric water. The Changkeng gold- and the Fuwang silver deposits show different Pb isotope signatures, suggesting different sources of ore-forming material. Rb-Sr isochron are (68±6 Ma) and ⁴⁰Ar-³⁹Ar age (64.3±0.1 Ma) of the ore-related quartz veins from the Ag-deposit indicate that the Fuwang deposit formed during the Cenozoic Himalayan tectono-magmatic event. The adjacent Changkeng and Fuwang deposits could, however, represent a single evolved hydrothermal system. The deposits are alternatively the product of the superposition of two different geological events. Our work indicates that the Pacific Coastal Volcanic Belt in the South China Fold Belt has greater potential for Himalayan precious metal mineralization than previous realized.