THE ISOTOPIC STUDY OF MAJOR TYPES OF GOLD DEPOSITS OF CHINA
Wang Yiwen (Research Institute, Jilin Provincial Metallurgical Geological Exploration Dorporation)
According to 1364 data of sulfur isotopes, 47 data of lead isotopes and a large number Of K-At and U-Pb age data from more than 100 gold deposits distributed in 14 provinces (or regions) in China, this paper first discusses the characteristics of sulfur and lead isotopes and the metallogenic epochs of different types of gold deposits, and then approaches some problems concerning the genesis of gold deposits. The sulfur isotopic composition of metamorphic hydrothermal gold deposits is controlled by the sulfur isotopic background value of gold source beds and the metamorphic facies belts. Ore lead is either older (related to Archean greenstone belts) or younger (related to specific Phanerozoic horizons)anomalous lead, The lead mineralizing age calculated by the secondary isochron curves coincides with the age of metamorphism-migmatization of the strata. The age of source lead is equivalent to the formation age of the source-beds.The sulfur isotopic composition of sedimentary-metamorphic (transformation) gold deposits is controlled by stratigraphic levels. The δS~(34) values are highly variable and often remote from the meteorite values. Ore lead is ancient ordinary lead with a model age of 500-700m. y.. Its metallogenic epoch belongs to the Proterozoic. The sulfur isotopic composition of migmatized hydrothermal gold deposits is identical to that of their parent rocks, and both are controlled by the source-beds and characterized by the enrichment of S~(34). Ore lead is younger ordinary lead and the metallogenic epoch is Mesozoic. The sulfur isotopic composition of regeneration-anatectic magmatic hydrothermal gold deposits is characterized by the δS~(34) values that are close to that of meteorite and less varied. Their parent rocks are mostly assigned to the Yanshanian stage, but the ore lead is ancient anomalous lead, which indicates its regeneration nature. Gold's conspicuous siderophile property, the close relationship between gold mineralization and Archean greenstone belts, the distinct stratabound feature and the inheritance and regeneration of gold mineralization-all these show that gold has the unique mineralization feature distinct from other metallic elements.