西藏多巴—班戈地区燕山晚期花岗岩的成因与找矿前景

探讨西藏多巴—班戈地区燕山晚期花岗岩类岩体的成因,评价找矿前景.通过对花岗岩类岩体的地质、地球化学、成分演化程度、分异程度和氧化状态的分析,结果表明,早白垩世花岗岩的岩石组合为英云冈长岩-花岗闪长岩-二长花岗岩,属偏铝质—过铝质高钾钙碱性I型,具弱的斜长石分离结晶,形成于火山弧环境,角闪岩部分熔融而来； SiO2含量低...

Genesis of late Yanshanian granites and the ore-search prospectin the Duoba-Bange area, Gangdise Belt, Tibet, China

The geology and geochemistry of the late Yanshanian granitoids in the Duoba-Bange area are systematically studied.The results indicate that the rock association of Early Cretaceous granites is tonalite-granodiorite-monzonitic granite,it is the metaluminous-peraluminous and high-K calc-alkaline I-type with weak fractional crystallization of plagioclase,high content of Rb,Th,Ce,Hf and low content of Ba,Nb,Y,and the product of amphibolic fractional melting,which forms in the volcanic arc.The Late Cretaceous granites is monzonitic granite.It is peraluminous high-K calc-alkaline S-type with strong fractional crystallization of plagioclase,high content of Rb,Th,Ce,Hf and low content of Ba,Nb,Sr.It is generated by fractional melting of metasandstone and greywacke,which forms in the tectonic settings of post-collision environment.The maturity of volcanic arc and the emigration of granitoids imply that the subduction direction of Tethys ocean crust in late Yanshan is the north.The analysis of the type of granites,the degree of compositional evolution,differentiation degree and oxidation state in the study area show that the Early Cretaceous granites are with lower SiO2 content and composition evolution,moderate differentiation,ilmenite series,and the metallogenic potential types are the Fe-Cu-Au deposits.The Late Cretaceous granites are with higher SiO2 content and degree of compositional evolution,strong differentiation,ilmenite series,and the potential mineralization types are W-Sn-Mo deposits.Combined with the tin abnormality near the south of Dongga,the tungsten abnormality near Bange County and also the sericite,chloritization alteration,it can be educed that the Late Cretaceous granites have the potential to generate tin and tungsten.