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Study on fluid inclusion of Nongruri gold deposit, Tibet, China

2011; Science Press; Linguagem: Inglês

2095-8927

Yun Liu,

Geochemistry and Geochronology of Asian Mineral Deposits

The Nongruri gold deposit located in the Riduo Town, Maizhokunggar County, Tibetan Autonomous Region, is an epithermal Au-Sb deposit firstly found in the eastern section of southern Gangdese metallogenic belt. Based on the results of field geological survey, and fluid inclusion measurements including petrography, homogenization temperature analysis, composition of liquid and vapor by laser Raman analysis (LRM) and daughter mineral by X-ray analysis (SEM/EDS), the characteristics, the evolution of ore-forming fluid and mechanism of Au precipitation were discussed in this paper. Its hydrothermal ore-forming process includes several stages: (1) the early stage forming pyrite-quartz assemblage, includes daughter minerals fluid inclusions, with homogenization temperatures clustering 256~335℃, and the salinities clustering 29.7%~38.9% NaCleqv; (2) the main stage forming arsenopyrite-pyrite-quartz assemblage, includes CO2-rich fluid inclusions, with homogenization temperatures clustering 230~357℃, the salinities clustering 1.81%~9.74% NaCleqv, and the density of CO2 clustering 0.16~0.29g·cm-3; (3) the late stage forming stibnite-quartz, realgar-quartz and carbonate veinlets assemblage, includes aqueous fluid inclusions, with homogenization temperatures clustering 134~245℃, and the salinities clustering 1.91%~8.95% NaCleqv. The ore-forming fluid related to gold mineralization is intermediate temperature, low salinity and CO2-rich fluid. The fluid immiscibility caused by the decreasing of temperature and pressure of fluid, and the fractionation of CO2 from the fluid are the major factors controlling gold precipitation.