西藏邦铺斑岩型钼铜多金属矿床含钼铜脉石英的激光显微探针^(40)Ar/^(39)Ar年龄及地质意义

LASER MICROPROBE ^(40)Ar/^(39)Ar DATING ON VEIN QUARTZ CONTAINING Mo AND Cu IN THE BANGPU PORPHYRY-TYPE Mo-Cu POLYMETALLIC DEPOSITS,TIBET

采用激光显微探针40Ar/39Ar微区定年方法,对西藏邦铺钼铜多金属矿床中含矿脉石英进行微区年代测定,获得等时线年龄为13.9 Ma±0.9 Ma(MSWD=29),其下限(13 Ma)代表了成矿年龄。该年龄略晚于二长花岗斑岩结晶年龄(13.9 Ma±0.3 Ma,MSWD=3.05),表明邦铺矿床成岩成矿作用是一个连续的岩浆作用过程。同时对冈底斯斑岩铜矿带成岩-成矿年龄进行统计学研究,获得冈底斯斑岩铜矿带成岩-成矿作用高峰期为15 Ma,成岩-成矿年龄线性方程为Y岩=1.291X矿+7.785(R2=0.291),充分说明邦铺矿床与冈底斯斑岩铜矿一样,是一次大规模爆发成矿的过程,成矿事件发生具有高度的统一性与集中性。

Continuous laser microprobe 40Ar/39Ar technique has been used to analyze the ore-bearing vein quartz,in the Bangpu porphyry-type Mo-Cu polymetallic deposits.A 40Ar/39Ar isochron gives out an age of 13.9 Ma±0.9 Ma（MSWD=29）,representing the age of mineralization which is somewhat lower than the crystallization age（13.9 Ma±0.9 Ma,MSWD=3.05） of monzonite granite-porphyry,and indicating that the rock-forming and ore-orming process is a continuous magmatic process.Meanwhile,a statistic study of rock-forming and ore-forming ages of Gangdese porphyry copper belt shows that its peak progress age is 15 Ma with the linear equation of Yrock=1.291Xore＋7.785（R2=0.291）,suggesting that the formation of Bangpu deposit is the same as the Gangdese belt,characterized by explosive ore-forming progress with uniform and intensive ore-forming events.