西昆仑精尼克盖曼南岩体年代学、地球化学特征及其地质意义

Geochronology,Geochemistry and Geological Implication of Jinnikegaiman Pluton in Western Kunlun

精尼克盖曼南岩体岩性为中细粒二长花岗岩,锆石LA-ICP-MS U-Pb定年结果表明,二长花岗岩成岩年龄为(516.5±0.8)Ma,时代为早寒武世;岩石属于钙碱性系列准铝-过铝质花岗岩;轻稀土元素较为富集,轻、重稀土元素分馏明显,具有明显的负Eu异常;岩石相对富集Rb、K等大离子亲石元素,亏损Nb、Ta、P、Ti和HREE等高场强元素;为下地壳火成岩熔融形成。结合锆石定年结果及岩体产出的区域地质背景,研究认为精尼克盖曼南岩体是在后碰撞伸展拉张型裂谷环境下的产物;在早寒武世西昆仑造山带处于后碰撞伸展拉张背景。

The lithology of Jinnikegaiman pluton is mid -fine grained monzonitic granite. The zir- con U-Pb dating indicate that the age of monzonitic granite is （516.5±0. 8） Ma, belongs to Early Cambrian. This monzonitic granite belongs to aluminous- peraluminous granite of calc- al- kaline series. It is enriched in light rare earth element, with obvious fractionation between LREE and HREE. It has slight negative Eu anomaly, which is enriched in Rb, K and other large - ion lithophile elements, with depletion of high field strength elements, such as Nb, Ta, P, Ti and HREE. It was derived from lower crust and formed by the melting of igneous rock. According to the zircon U- Pb dating and regional geological background, it＇s believed that this pluton was formed in the environment of rift valley of Post - COLG and the west Kunlun has experienced a Post - COLG extension environment in Early Cambrian.