Hydrothermal metallogeny of the Tangjiaping molybdenum deposit, Henan Province

Abstract：The Tangjiaping Mo deposit in Henan Province is located in the Dabie orogenic belt. In quartz three types of fluid inclusions can be observed, namely CO2-rich (bearing) fluid inclusions, aqueous solution fluid inclusions and daughter-crystal-bearing fluid inclusions, based on the petrography, microthermometric measurement and Laser Raman microprobe analysis. The homogenization temperatures vary from 126.7°C to 472.1°C, the calculated fluid salinities cluster in two ranges, i.e., (0.18-14.21) wt% NaCl.eqv and (33.10-54.37) wt% NaCl.eqv, with densities changing from 0.38 to 1.21 g/cm3. Daughter minerals, mainly halite and metallic sulfide, can be recognized in fluid inclusions. The homogenization temperature and salinity of fluid inclusions reduce gradually outward from the center of ore-forming porphyry system. From early to late the fluid system evolved from and high temperature and high salinity to low temperature, and low salinity; and the trapped pressure reduced, indicating the mineralization depth became shallower gently. The Re-Os isotopic model ages of molybdenite are between 113 Ma and 118 Ma, about 10 Ma later than the crystalline age of the Tangjiaping granite porphyry. The ore-system was formed in waning stage extension setting of the inter-continental collision between Yangtze Block and North China Block.