新疆沙尔布拉克蛇绿岩岩石地球化学特征及形成时代

Geochemical Characteristics and Geochronology of Sherbulake Ophiolite in Xinjiang

介绍了沙尔布拉克蛇绿岩物质组成、岩石地球化学特征及形成时代,并探讨其就位机制。该蛇绿岩套包括蛇绿岩残片、上覆岩系、外来岩块3部分,其中镁铁质火山岩具亏损高场强元素和富集大离子亲石元素特征,稀土元素球粒陨石标准化曲线总体平坦,分馏程度较弱,说明岩浆地幔源区可能卷入岛弧火山岩和洋中脊玄武岩成份,获得玄武岩中锆石SHRIMP U-Pb年龄为(322±9)Ma,认为沙尔布拉克蛇绿岩与库尔提蛇绿岩形成环境较相似,均形成于弧后盆地。就位过程应包括俯冲过程中的侵位、碰撞过程的侵位、地壳缩短期的侵位和阿尔泰南缘二叠纪地壳伸展减薄阶段的改造等。

The article mainly introduces the material composition, geochemical characteristics, geochronology and Em- placement mechanism of Sherbulake ophiolite. The ophiolite includes ophiolite fragment, overlying rocks and exotic block, the mafic volcano rock with loss of high field elements and enrichment of large ion lithophile elements, chondrite normalized REE curves generally flat, fractionation of the weaker, indicate the magma of mantle source region may be involved in island-arc volcano rock and mid-ocean ridge basalt composition, and get the basalt SHRIMP zircon U-Pb age of （322±9） Ma. Therefore, we think that the formation environment of Sherbulake and Kuerti ophiolite are relatively sim- ilar, formed in the back arc basin. Emplacement process should be included four stages, emplacement during subduction, emplacement of collision process, emplacement of crustal shortening and transformation of the crustal extension of south- ern crustal margin of the Altai basin.