Re-Os age for molybdenite from SW Sardinia (Italy): A comparison with ~(40)Ar/~(39)Ar dating of Variscan granitoids

摘要

Molybdenites from two small deposits in late Variscan granites from SW Sardinia, have been dated at 288.7 +- 0.5 and 288.8 +- 0.5 with the Re-Os method. This age is interpreted as the emplacement age of the hosting, highly altered leucogranite-type porphyry stocks, typical of post-orogenic, shear-zone related magmatism. These results are compared with ~(40)Ar/~(39) Ar intrusion ages of the previously segregated Variscan leucogranites (310 →300 Ma). We suggest that there are at least two ages of leucogranites and that only the younger A-type generation (289 Ma), associated with the last stages of collapse of the Variscan chain, is carrying the Mo-mineralization.