Abstract

The Tuwaishan, Baoban, Erjia, Bumo and other gold deposits in western Hainan occur in Precambrian metamorphic clastic rocks and are structurally controlled by the Gezhen shear zone. Fluid inclusion studies have been carried out of the gold deposits mentioned above. The homogenization temperatures of the whole fluid inclusion population range from 140°C to 370°C, indicating that gold was precipitated mainly at 240–250°C. The salinities are within the range of 2.0–9.2 wt% NaCl equiv. and the pressure of formation of the deposits was estimated at about 270×105−500×105Pa, corresponding to a depth of about 1.1–2.0 km under lithostatic confinement. Chemical studies show that the ore fluid is of the Na+(K+)-Ca2+-Cl−(F−) type. Theδ18O andδD values of the fluid vary from −2.7‰- +4.4‰ and −50‰–−87‰ Evidence developed from fluid inclusions and geological setting indicates that the ore fluid was a mixture of magmatic and meteoric-hydrothermal waters. Changes in chemical composition andδ18O andδD of fluid inclusions from one ore field to another seem to be related with regional tectonism, metamorphism and magmatism.

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