西天山阿吾拉勒西段木汗巴斯陶侵入岩体的地球化学特征、时代及地质意义

Pluton from Muhanbasitao in the western of Awulale,Western Tianshan: Geochemistry,geochronology and geological implications

阿吾拉勒山西段出露大量古生代侵入岩体。其中木汗巴斯陶岩体由角闪辉长岩和花岗岩组成。它们均富集大离子亲石元素(Rb、Ba、Sr等)、强烈亏损高场强元素(Nb、Ta、Ti),不具明显的轻重稀土分异和铕异常,类似于大陆弧钙碱性岩浆岩的地球化学特征。LA-ICP-MS锆石U-Pb测年结果表明角闪辉长岩和花岗岩的侵位时代分别为317.0±2.2Ma和319.1±2.4Ma。木汗巴斯陶侵入岩体的地球化学和年代学表明包括阿吾拉勒山西段在内的整个伊犁-中天山地块南缘在早石炭世晚期至晚石炭世早期处于一个活动大陆边缘环境。

A number of Paleozoic intrusions are exposed in the western segment of Awulale Mountains. Among them, the Muhanbasitao pluton consists of hornblende gabbros and granites. They are enriched in large ion lithophile elements （ LILE, Rb, Ba, Sr） and intensively depleted in high field strength elements （HSFE, Nb, Ta, Ti） without obvious REE fractionation and Eu anomaly, similar to the geochemical characteristics of calc-alkline magmatites in a continental arc setting. LA-ICP-MS zircon U-Pb ages of hornblende gabbro and granite are 317. 0 ＋- 2. 2Ma and 319. 1 ＋- 2.4Ma respectively. The geochronology and geochemistry of the Muhanbasitao pluton suggest that all the southern margin of the Yili-Central Tianshan block including the western segment of Awulale Mountains is an active continental margin environment at the latest of Early Carboniferous to earliest of Late Carboniferous.