Fluid inclusion study of Fankou Pb-Zn ore deposit,Fankou, Guangdong,China

The Fankou Pb-Zn ore deposit occurs in Devonian and Carboniferous carbonate rocks. This deposit was thought to be a hydrothermal ore deposit related to a granite, but the present research suggests it is a stratabound, stratiform mineral deposit. As a result of geological studies, primary sedimentary and later replacement features were found. Part of some ore bodies are concordant with the host rocks, but most are discordant lenses and veins in the carbonate rocks. Thus there are two types of ores, primary sedimentary and later replacement. The replacement type is very common. Isotopic studies indicate that most of the Pb and S are of sedimentary origin, but part of Pb is of radioactive origin, possibly introduced during later replacement. A regional geochemical survey indicates that the Pb and Zn contents of the Fankou region are respectively 1.5 and 3 times the primary sedimentary type. Gas-liquid fluid inclusions were found in the replacement type ore but not in the primary sedimentary type. The fluid which replaced the primary sedimentary rocks had temperatures of 100–200°C, with a salinity of 3–6 wt. % NaCl equiv. Under the action of such fluid the original sedimentary rocks were replaced to form the present ore deposit.