Fluid inclusion studies of zoning in the Dachang tin-polymetallic ore field, People's Republic of China

Abstract

The Dachang tin-polymetallic ore field, Guangxi, is one of the largest in the world. These are hosted by Devonian carbonate-rich sediments metamorphosed to hornblende hornfels facies near the underlying Yanshanian Longxianggei granite (91 Ma). Hydrothermal alteration is grossly zoned outward from the granite contact. There is a zonal pattern of both temperatures and ore fluid compositions deduced from fluid inclusions. Thermodynamic calculations based on fluid composition and measured temperature show that f02 values of the ore-forming stages were very low, well below the FMW buffer and increased from early to later stages. Tin precipitation was affected by a low oxygen fugacity of ore fluids partly resulting from the occurrence of black shale, and a decrease in temperature. -from Authors Show more