西昆仑胜利桥一带晚三叠世侵入岩年代学、岩石地球化学特征及其地质意义

Geochronology,Geochemistry and Geological Implication of the Late Triassic Intrusive Rocks from Shengliqiao Erea,Western Kunlun

研究区内侵入岩主要分布于麻扎构造混杂岩带北部,其产状严格受康西瓦结合带控制,岩性主要有黑云母花岗岩、花岗岩、黑云母二长花岗岩和二长花岗岩。锆石U-Pb定年结果表明,黑云母花岗岩成岩年龄为(216.48±0.62)Ma,为早中生代印支期岩浆作用的产物。岩石REE含量为(113.9~191.55)×10^(-6),LREE含量为(104.96~172.09)×10^(-6),HREE含量为(8.94~19.4)×10^(-6)。轻稀土元素较为富集,轻、重稀土元素分馏明显,具有较弱的负铕异常。岩石相对富集Rb、Ba、K、LREE等大离子亲石元素,亏损Nb、Ta、P、Ti和HREE等高场强元素。晚三叠侵入岩属于高钾钙碱性系列和准铝-过铝质花岗岩S型和I型花岗岩;源区物质以壳源物质为主,并有部分幔源物质的参与。结合锆石定年结果及岩体产出的区域地质背景,认为晚三叠世西昆仑地区已进入碰撞造山过程的后碰撞阶段,区内侵入岩是在岩石圈伸展环境下形成的产物。

The intrusive rock of the study area mainly distribute at the north of Mazha Tectonic Melange, its atti-tude are control by Kangxiwa suture zone strictly, and the rock mainly include biotite granite, granite, monzonitic granite, biotite adamellite. The outcome of the zircon U-Pb dating indicate that the age of the biotite granite is （216. 48 ± 0.62 ） Ma, and it is the product of magmatism in Indosinian. The content of Z REE in rock is （113. 9-191. 55） ×10^-6, the content of LREE was （104.96 - 172.09） ×10^-6, the content of HREE was （8. 94 - 19. 4）×10^-6. The light rare earth element is rich, and the distinction of the the light rare earth element and the heavy rare earth element in fractionation are obvious, and they are slight Eu negative abnormality. Rb,Ba, K and LREE, etc which large-ion lithophile elements are rich in the rock,and it has low contents of Nb,Ta,P,Ti and HREE, etc which high field strength elements. The intrusive rock of Late Triassic belong to high-K calc-alkaline series and aluminous-peraluminous granite S or I-type granite; The matter of this area are mainly derived from thecrust, and partially from the depth, according to the zircon U-Pb dating and the geological background of this area, Western Kunlun area has enter post-collision stage of collision orogeny in late Triassic epoch. The intrusive rock is the product of the extension environment of lithosphere.