西藏邦铺钼铜矿区花岗斑岩成岩年龄研究

DATING OF MONZONITIC GRANITE PORPHYRY IN THE BANGPU MO-CU DEPOSIT,TIBET

邦铺钼铜矿床是发育于冈底斯成矿带的大型斑岩型钼铜矿床,矿区内岩浆岩发育,(二长)花岗斑岩为成矿母岩。利用斑岩中锆石离子探针U-Pb法和全岩Rb-Sr法测定邦铺含矿斑岩的年龄,以确定含矿斑岩的形成时代。花岗斑岩中锆石SHRIMP U-Pb法测定其年龄为14.2 Ma±0.2 Ma(MSWD=0.79);二长花岗斑岩中锆石SHRIMP U-Pb法测试值为13.9 Ma±0.3 Ma(MSWD=3.05);全岩Rb-Sr等时线年龄为13.88 Ma±0.38 Ma(MSWD=1.7)。因此14.2 Ma^3.9 Ma年龄值可以作为邦铺矿区含矿斑岩体的结晶年龄。

The Bangpu Mo-Cu deposit is a large scale porphyry type deposit in the Gangdese ore-forming zone,Tibet,where the igneous rocks are well developed.Granite porphyry and monzonitic granite porphyry are closely related to the formation of Mo-Cu deposit.Methods of zircon SHRIMP U-Pb dating and whole-rock Rb-Sr dating are used to determine the ages of ore-bearing porphyry for the Bangpu Granite porphyry.It is showed that the zircon U-Pb age is 14.2±0.2 Ma（MSWD=0.79） for granite porphyry,and the second long granite porphyry zircon U-Pb age is 13.9 Ma±0.3 Ma（MSWD = 3.05） for the monzonitic granite porphyry.Meanwhile,the Rb-Sr isotopic Isochron age of whole rock is 13.88 Ma±0.38 Ma（MSWD=1.7）.So the 14.2 Ma^13.9 Ma is considered as the crystallizing age of the ore-bearing porphyry in the Bangpu Mo-Cu ore area.