藏南定结淡色花岗岩——基底隆升降压熔融成因的地质证据

Leucogranites-geological proof of uplifting, decompressing and melting of the basement, Dingjie, South Tibet

西藏南部定结地区高喜马拉雅结晶基底中淡色花岗岩体紧靠藏南拆离断层内部产出,野外地质和岩相学特征显示其为S型、分两期侵入的淡色花岗岩体——早期的黑云母淡色花岗岩和晚期的白云母淡色花岗岩。基底副变质岩中广泛分布淡色花岗岩脉体,在基底副变质岩中的淡色花岗岩脉体中发现紫苏辉石暗色麻粒岩残留体,这表明本区高喜马拉雅淡色花岗岩源岩为基底副变质岩,且基底副变质岩是在基底快速隆升降压的条件下发生缺水熔融生成的淡色花岗岩岩浆。

Located immediately in the inner Southern Tibet detachment in the Dingjie region, South Tibet, leucogranites in the High Himalayan crystalline basement are S-type granites and intruded with two different periods, earlier biotite leucogranites and later muscovite leucogranites. The leucogranites veins occurred widespreadly in the para-metamorphic rocks, in which the hypersthene mela-granulite distributed. That suggests the source rocks of leucogranites of the High Himalaya are para-metamorphic rocks. For the basement was uplifting, pressure relieved and lacked water, source rocks were melting partly and formed the leucogranite magma.