Geological characteristics of gold deposits in the Ailaoshan gold belt, western Yunnan Province, China

Through detailed research of regional alteration types and stages of the gold deposition in the Ailaoshan gold belt, combined with analysis of regional geochemistry, mineral chemistry, stable isotopes and fluid inclusions microthermometry in gold deposits, four genetic types of gold deposits in the Ailaoshan belt have been established for the first time in this paper. The distribution of gold deposits in Ailaoshan is controlled by NW-trencling deep fracture zones.The intersection of the NW-trending deep fractures, and EW- and NS-trending thrusts control the distribution and localization of goldfields,and their secondary faults and the interlayered clecollement structure control the local distribution of gold orebodies. Fluid inclusions in quartz of gold deposits, indicate that pressure and temperature increased gradually from the north to the south of the belt. Sulfur isotopes indicate that the sulfur source of the gold deposits is mainly characterized by mantle source in the northern part of the belt, whereas mainly by a mixture of stratum and mantle sulfur in the southern part of the belt. H and O isotope composition of the gold deposits suggests that the ore-forming fluid is a mixture dominated by metamorphic or magmatic hydrothermal fluids and a meteoric fluid component. Lead isotopes indicate that the ore lead comprise a mixture of crustal and mantle leads. The ore-forming process in the belt lasted for a prolonged period from Late Yanshannian period to Himalayan period.