西天山伊犁地块北缘桦木沟高分异I型花岗岩年代学、地球化学及其构造意义  

Geochronology,Geochemistry and Tectonic Significance of Huamugou Highly Fractionated I-type Granitoid Pluton in Northern Yili Block,Western Tianshan

作　　者：王永文[1,2] 颜丹平[1] 刘红旭[1,2] 潘澄雨[2] 陈峰[1,2] 孟云飞[1,2] 丁波[2] 刘涛[2] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]核工业北京地质研究院,北京100029

出　　处：《现代地质》2015年第3期529-541,共13页Geoscience

基　　金：国家"973"项目(2015CB453004);国家"863"项目(2012AA061801)

摘　　要：古生代晚期天山造山带经历了洋壳消减及地块拼合的过程,西天山伊犁地块周缘拼合带的花岗岩岩浆记录可以为俯冲造山作用时限提供有效的约束。岩石地球化学和年代学分析显示,位于伊犁地块北缘的桦木沟花岗岩体高硅,富碱,贫铁,富集HFSE,具强烈铕负异常,亏损Ba、Sr、P、Ti,富集Cs、Rb、U、K,与高分异I型花岗岩地球化学特征一致;Pb同位素指示花岗岩源区为造山带下地壳;LA-ICP-MS锆石U-Pb测年结果表明,该岩体结晶年龄为(330.2±5.7)Ma,说明桦木沟岩体产于汇聚大陆边缘,天山北部洋壳在早石炭世晚期仍在向南俯冲,准噶尔地块与伊犁地块还未碰撞拼合,天山地区可能正处于俯冲消减阶段。The Tianshan orogenic belt experienced a subduction and split plots during Late Paleozoic. Records of granite magma records provide important constraints on timing of subduction. The geochemical and chronological results show that Huamugou pluton is consistent with highly fractionated I-type granite of high silicon,rich alkali,poor iron. Ba,Sr,P,Ti are poorly concentrated and Cs,Rb,U,K are well concentrated. Pb isotope studies suggest crustal source with added mantle material. The LA-ICP-MS zircon U-Pb dating on zircons yields age of（ 330. 2 ± 5. 7） Ma,belonging to the late Early Carboniferous. These geochemical characteristics indicate that the Huamugou pluton formed in a continental arc setting. Northern Tianshan oceanic crust still southward subducted in the late Early Carboniferous and Junggar plate is not collided with Yili plate,which shows that the Tianshan region is in the subduction stage.

关 键 词：天山 伊犁地块 高分异I型花岗岩 锆石U-PB定年 桦木沟岩体 俯冲 

分 类 号：P588.1[天文地球—岩石学]