Re-Os molybdenite ages of granitoid-hosted Mo–Cu occurrences from central Anatolia (Turkey)

The Central Anatolian Crystalline Complex (CACC), where many granitoids are emplaced and related ore occurrences/deposits occur, is tectonically located in the Alpine–Himalayan Belt. The CACC hosts numerous ore occurrences/deposits (Cu, Mo, Fe, Pb and Zn) that are spatially associated with granitoids. The calc-alkaline Karacaali, Baliseyh and Başnayayla granitoids that form the northern granitoid belt of the CACC host important Mo–Cu occurrences. In this paper, we document Re–Os isotopic age data in molybdenites to determine the timing of the granitoid-hosted mineralizations in the CACC. content of molybdenite in the Başnayayla is significantly higher (108.9–148.5 ppm) than molybdenites from the Karacaali (16.3–74.8 ppm) and Balışeyh (4.2 ppm). Two molybdenite samples from Karacaali and two samples from Başnayayla occurrences give Re–Os ages ranging from 73.8 ± 0.4 to 76.2 ± 0.4 Ma and 77.1 ± 0.4 to 78.0 ± 0.4 Ma, respectively. Furthermore, one molybdenite sample from Balışeyh gives a 73.6 ± 0.4 Ma Re–Os age. These ages are consistent with those of post-collisional granitoids and indicate close relationship between mineralization events and granitic magma differentiation–crystallization processes. The new Re–Os age data obtained from this study show that mineralization events developed earlier (78–77 Ma) in the East (Başnayayla) as compared with the West (76–73 Ma) (Karacaali and Baslışeyh) of central Anatolia. Moreover, one molybdenite sample from Karacaali gives 76.2 Ma, which is very close to the Başnayala ages (78 and 77.1 Ma). According to these data, one possible explanation is that older molybdenite ages in Karacaali and Başnayayla probably represent the mineralization period related to crystallization–differentiation processes. On the other hand, the younger molybdenite age (73.8 Ma) in the Karacaali may represent prolongation of the life of magmatic–hydrothermal processes/cycles and/or the remobilization of molybdenum within the solidified granitic system by the intrusion of the basic magma.