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Liu C.,Fifth Institute of Geology and Mineral Resources of Qinghai Province | Li S.,Qinghai Geological Survey | Chen Y.,China University of Geosciences | Li D.,China University of Geosciences | And 4 more authors.
Geotectonica et Metallogenia | Year: 2015

The Duocaima ultra-large-scale Pb-Zn deposit is located in the northern Qiangtang terrane of the northeastern Qinghai-Tibetan Plateau, in-between the Kekexili-Jinsha River and Longmucuo-Shuanghu-Lancang River suture zones. The Duocaima Pb-Zn deposit is controlled by NW-trending fault structure, whose ore bodies are vein-like and lenticular. The ore-hosting rocks are the Permian limestone of the Jiushidaoban Formation. The ore mineral assemblage is simple, which commonly show structures such as disseminated, brecciated, lumpy and vein-like types. The metallic minerals mainly consist of galena, sphalerite and pyrite, and the gangue minerals mainly consist of calcite, dolomite, barite and quartz. On the basis of field geological observation, we have carried out inclusion temperature study on the gangue minerals. The primary fluid inclusions trapped in calcite and quartz can be divided into three types, i.e., gas-liquid phase inclusion, gas-rich gas-liquid phase inclusion and pure gas inclusion. The three types of inclusions are commonly concurrence and have similar homogenization temperatures. The gas-liquid phase inclusion is the major type of fluid inclusions of in the gangue minerals. The results of inclusion temperature show that the freezing point temperature of ore-forming fluid is -19.3--0.5℃ and the homogenization temperature vary in range of 97-497℃ with peak range of 120-180 ℃. The fluid salinity vary from 0.9% to 21.9% NaCleq with an average of 9.2% NaCleq. The fluid density is 0.70-1.00 g/cm3 and the average density is 0.94 g/cm3. The estimated ore-forming pressure is 5-10 MPa, corresponding to depth of 0.5-1 km. The characteristics of the ore-forming fluid show that the ore mineralization was took place under shallow depth via ore-forming fluids of low temperature, low salinity, and middle density. Combining with the characteristics of regional ore-forming background, deposits geology and fluid inclusion, we propose that the Duocaima Pb-Zn deposit is a MVT Pb-Zn deposit formed in the orogenic thrust-nappe belt. ©, 2015, Science Press. All right reserved. Source

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