作　　者： ; ; ; ; ; (张兴国）;

机构地区： 西藏地勘局区域地质调查大队西藏拉萨851400

出　　处： 《大地构造与成矿学》 2010年第2期291-297,共7页

摘　　要： 对汤不拉钼铜矿床斑岩体进行了LA-ICPMS锆石U-Pb同位素定年,获得其成岩年龄为(19.88±0.38)Ma,表明斑岩体与矿化的形成时间一致,为中新世中期;含矿斑岩元素地球化学特征表明,其与冈底斯成矿带其它斑岩型矿床的含矿斑岩类似,具有埃达克质岩的地球化学属性,并同时具有高钾、高铝特征,与起源于俯冲洋壳熔融形成的埃达克岩构造背景不同。本文认为汤不拉含矿斑岩为新生增厚下地壳在上涌软流圈热流影响下部分熔融的产物,同时上升的埃达克质岩浆萃取源区金属元素,在后碰撞伸展构造环境下由于温度、压力的释放形成斑岩型矿床。 The discovery of the Tangbula porphyry Mo-Cu deposit makes the Gangdese porphyry copper belt extent to the east more than one hundred kilometers,so that it is close to a world class porphyry copper belt. The ore-bearing porphyries of the Tangbula deposit are granitic porphyry,quartz porphyry and granodioritic porphyry. The wall rocks in contact zone,porphyraceous biotite adamellites,are the major ore-hosted rocks. In this paper,zircon U-Pb dating on the Tangbula ore-porphyry is performed by LA-ICPMS dating technique. The mean ^206Pb/^238U age is 19.88±0.38Ma,which means that the ore-bearing porphyry intruded in middle Miocene,it also implies that the formation of the ore-bearing porphyry was simultaneous with the Mo-Cu mineralization. Geochemical analyses of the dating samples show that they have the characteristics similar to adakite,the same as ore-bearing porphyries in other deposits of the Gangdese belt. However,Al and K are higher in these rocks,which is different from the adakites generated from subducting oceanic slab. According to these results,we deduced that the magma forming the adakitic ore porphyry was generated by the partial melting of the thickened new lower crust under the heating of the ascending asthenosphere,this adakitic magma extracted ore elements from its origin and formed the porphyry Mo-Cu deposit in a shallow extension structural environment due to the decreasing of temperature and pressure.

关 键 词： 汤不拉斑岩铜矿 锆石 同位素定年 含矿斑岩

领　　域： [天文地球] [天文地球]