Fluid inclusions in coexisting cassiterite and quartz from the Tongmushan tin deposit, eastern Hunan, China

The Tongmushan greisen type tin deposit is an important deposit in Xitian tin polymetallic ore field at eastern Hunan. Based on detailed field investigation and experimental studies upon the ore texture and the fluid inclusion petrographic properties of the Fluid Inclusion Assemblage (FIA), we carried out microthermometric and Raman microspectroscopic studies upon fluid inclusions in cassiterite and coexisting quartz in greisen type ore samples and quartz veins cutting the orebodies. The results show that significantly differences exist on the constituents, homogenization temperatures and salinities between the cassiterite and intergrowth quartz, suggesting that the P-T-X conditions related to the formation of cassiterite and intergrowth quartz are different. Quartz veins which cut the ore bodies are the products of fluid action after magmatism and mineralization. Fluids related to tin mineralization are from a NaC1-H2O system with medium to high temperatures and medium to low salinities, while fluids associated with the formation of quartz are from a carbon containing system. This study indicate that water rock reaction and the cooling of fluid are the main mechanisms for tin precipitation in the fluid,and the fluid immiscibility maybe led to the formation of the quartz.

Automated summary

The Tongmushan greisen type tin deposit in eastern Hunan is an important deposit within the Xitian tin polymetallic ore field. Through detailed field investigation and experimental studies, it was found that there are significant differences in the composition and formation conditions between cassiterite and intergrowth quartz in the deposit. The quartz veins cutting the ore bodies are likely formed by fluid activity following magmatism and mineralization. Fluids related to tin mineralization are from a NaCl-H2O system, while fluids associated with the formation of quartz are from a carbon containing system.