西藏日土县松西地区过铝质花岗岩的地球化学特征及构造背景

Geochemical characteristics and tectonic setting of peraluminous granite in the Songxi area, Rutog County, Tibet, China.

西藏羌塘北部松西地区分布有白云母二长花岗岩,岩石以高Al、K和低Fe、Mg组分为特征,ANKC值平均1.16,大于1.1,属典型的过铝质花岗岩类。CaO/Na2O在0.257～0.516之间,平均0.386,地球化学特征显示其是泥质岩局部熔融所形成的。40Ar-39Ar年龄为101.42Ma±0.18Ma,形成时代为早白垩世晚期。它的出现标志着班公湖-怒江结合带闭合后继续向北发生陆内俯冲,是后碰撞构造环境形成的花岗岩。

Peraluminous muscovite monzogranite is distributed in the Songxi area, northern Qiangtang, Tibet. The rock is characterized by high A1 and K.and low Fe and Mg, with the ANKC=1.16 （〉1.1）; so it belongs to typical peraluminous granite. The CaO/ Na2O ratios range from 0.257 to 0.516 with an average of 0.386. The geochemical characteristics show that the rock originated by partial melting of argillaceous rocks. Its 40^Ar-39^Ar age is 101.42±0,18 Ma, suggesting an late Early Cretaceous age. Its appearance indicates that intracontinental subduction took place as the Bangong Co-Nujiang junction zone continued to move northward after its closing. The authors think that the granite formed in a post-collisional setting.