Origin of the Dongbulage Mo-Pb-Zn deposit in the Great Hinggan Range, northeast China: Geological, molybdenite Re-Os dating, fluid inclusion, and C-H-O-S-Pb isotope constraints

The Dongbulage porphyry Mo-Pb-Zn deposit is located in the Huanggang-Ganzhuermiao polymetallic district (HGD) in the southern part of the Great Hinggan Range in northeast China. The Dongbulage deposit is hosted by granite porphyry, and the wall rock alteration can be divided into quartz-potassic, quartz-sericite, and propylitic zones. The hydrothermal activity in the deposit can be divided into five stages, with molybdenite and Pb-Zn ore occurring mainly as veins and veinlets in stages II and III, respectively. The fluid inclusion (FI) types include liquid-rich (L-type), vapor-rich (V-type), and daughter mineral-bearing (S-type) FIs. Based on the combination of FI types and their temperatures and salinities, it is inferred that fluid boiling and incorporation of meteoric water were key factors in the precipitation of Mo and Pb-Zn, respectively. Hydrogen and O isotope data for quartz, and C and O isotope data for calcite indicate that the ore-forming fluids were primarily magmatic in origin, and were mixed with meteoric waters during their evolution. The S and Pb isotope data, along with the mineral paragenesis, suggest that molybdenite and chalcopyrite which precipitated during stage II were derived mainly from magmatic-hydrothermal fluids, whereas arsenopyrite, sphalerite, and pyrite that precipitated during stage III were strongly affected by the incorporation of surrounding strata materials. Rhenium-Os dating of molybdenite indicates that mineralization in the Dongbulage deposit occurred at 162.1 +/- 1.3 Ma (n = 6; MSWD = 1.4). The results, combined with data from other deposits in the region of this age, indicate that important mineralization occurred in the HGD during 165-155 Ma.