Re-Os Isotopic Dating of Molybdenite from the Fu′anpu Molybdenum Deposit of Jilin Province and Discussion on Its Metallogenesis

The Fu′anpu molybdenum deposit is a newly discovered medium-scale porphyry molybdenum deposit in central Jilin Province and has great potential in deep prospecting. A precise Re-Os isotopic dating for five molybdenite samples from the Fu′anpu molybdenum deposit was carried out. The Re content in the samples varied from 9.94 μg/g to 15.12 μg/g and the model age of the molybdenite from (165.3±2.4) Ma to (167.0±2.3) Ma with the average model age of (166±1) Ma and the isochron age of (166.9±6.7) Ma,MSWD=0.60. The results indicate that the mineralization in the Fu′anpu molybdenum deposit took place at the Early Yanshanian period. The comparatively low Re content shows that ore-forming materials mainly came from a crustal source. Because of the movement of Palaeo-Pacfic Plate in the Early Yanshanian period,ore-bearing granites invaded in the intersection regions of the NE and NW direction faults,and the ore formed at post magmatic stage. The Early Yanshanian period is the major metallogenic epoch of the Jizhong-Yanbian metallogenic belt of the Jilin-Heilongjiang metallogenic province. Study on the magma intrusion at Early Yanshanian period in this region is of important significance for further prospecting of molybdenum ore.