塔里木北缘欧西达坂岩体锆石LA-ICP-MSU-Pb年龄和地球化学特征及构造意义

Zircon U-Pb ages, geochemical characteristics and its tectonic significance of the Oxidaban pluton in the northern Tarim basin.

欧西达坂岩体位于塔里木盆地北缘,通过岩石学、地球化学和年代学研究,探讨了该岩体的形成环境及构造意义。LA-ICP-MS锆石U-Pb测量获得该岩体年龄为(408.7±3.1)Ma,形成于早泥盆世。地球化学特征显示:Si O_2含量为60.29%～63.02%,Al_2O_3为14.92%～15.85%,A/NCK值为0.853～0.956,属准铝质岩石;稀土元素球粒陨石标准化曲线显示轻稀土富集,重稀土亏损,轻重稀土分馏明显,La_N/Yb_N值6.80～8.59,δEu值0.71～0.81;原始地幔蛛网图上,Rb、Th、K、Ba等大离子亲石元素和Hf十分富集,而高场强元素Nb、Ta、Ti、P等相对亏损。结合区域地质特征,推断欧西达板岩体形成于板块边缘环境。

Located in the northern margin of Tarim Basin, the Oxidaban pluton has been studied by petrology, geochemistry and chronology. The formation environment and tectonic significance of his pluton are discussed preliminarily. The age value of the pluton obtained by LA-ICP-MS zircon U-Pb measurement is 408.7 ±3.1Ma, which was formed in the early Devonian. Geochemical Characteristics show that SiO2 content is 60.29%~ 63.02%, Al2O3 is 14.92%~15.85%, A/NCK value is 0.853 ~ 0.956, which is a quasi-aluminous rock. The standardized curve of chondrite of rare earth elements shows that light rare earth elements is rich, heavy rare earth elements is deficient, light and heavy rare earth elements fractionation is obvious, LaN/YbN value is 6.80 - 8.59,δEu value is 0.71~0.81;On the original mantle spider web map, Rb, Th, K, Ba and other big ion lithophile elements and Hf are very rich, while the high field strength element Nb, Ta, Ti, P is relatively deficient. Combined with the regional geological characteristics, it is concluded that the Oxidaban pluton was formed in the plate margin environment.