Re-Os DATING OF MOLYBDENITE FROM THE BANGPU POLYMETALLIC DEPOSIT OF TIBET, AND ITS GEOLOGICAL SIGNIFICANCE

For the purpose of unravellng the mineralization time of the porphyry type molybdenum deposit in the Gangdese metallogenic belt,Tibet,five molybdenite samples from the Bangpu Mo-Cu polymetallic deposit are selected to carry out the Re-Os dating.The analysis yields an isochrone age of 14.92Ma±0.18Ma(MSWD=1.3)with a weighted mean age of 14.56Ma±0.18 Ma(MSWD=6.0),consistent with the Re-Os isochron age of 14.67Ma±0.54Ma performed and provided by previous workers.It was shown that the rock-forming age mainly concentrated in 13 Ma～18Ma in the Gangdese belt,while the ore-forming age is in 13Ma～16Ma with a peak progress age of 15Ma.So,the age of 14.54Ma±0.093Ma presented the age of ore-forming of Mo and Cu of the Bangpu porphyry deposit,consistent with the mineralization of Gangdese metallogenic belt,indicating that mineralization occurred in the extension setting after the collision event of Gangdese belt.