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西藏狮泉河地区仁温斜长花岗岩主要由更长石、石英等组成,Si O2含量为72.05%~72.83%,Al2O3含量12.72%~13.54%(<15%),Mg O含量1.19%~1.24%,Mg#值35.73~42.27(<50),Na2O含量介于4.56%~4.74%之间,K2O含量较低,在0.34%~0.57%之间,Na2O/K2O值为8.32~13.41,属低钾钙碱性系列岩石。斜长花岗岩与变质基性岩的地球化学特征表明,仁温斜长花岗岩可能是变质基性岩部分熔融形成的,该岩石中Sr、Rb、Ba等大离子亲石元素富集,Nb、Ta、Ti等高场强元素明显亏损,具有岛弧型火山岩的特征。用LA-ICP-MS法测得斜长花岗岩锆石U-Pb年龄为162.5±2.6Ma,表明狮泉河结合带(北亚带)在中侏罗世已发生俯冲作用。
The Renwen plagioclase granulite in Shiquanhe area of Tibet is mainly composed of feldspar and quartz. The content of Si O2 is 72.05% -72.83%, the content of Al2O3 is 12.72% -13.54% (<15%), the content of MgO is 1.19% -1.24 %, Mg # 35.73 ~ 42.27 (<50), Na2O content is between 4.56% ~ 4.74%, K2O content is low between 0.34% ~ 0.57%, Na2O / K2O is 8.32 ~ 13.41, Potash calcium alkaline series rocks. The geochemical characteristics of the plagiogranite and metamorphic basement rocks indicate that the Ren-Wen-plagioclase granulite may be partly melted by metamorphic basic rocks, in which large ion lithophile elements such as Sr, Rb and Ba are enriched and Nb and Ta , Ti field elements such as obvious loss, with island arc volcanic characteristics. The zircon U-Pb age of the plagiogranite was 162.5 ± 2.6 Ma measured by LA-ICP-MS, indicating that the Shiquanhe belt (North subtropical zone) had subducted during the Middle Jurassic.