西昆仑慕士塔格岩体的岩石地球化学特征、岩石成因及其构造意义  

Geochemical characteristics and petrogenesis of Muztagata intrusion in Western Kunlun orogenic belt and their tectonic significance

作　　者：康磊[1] 校培喜[1] 高晓峰[1] 奚仁刚[1] 过磊[1] 董增产[1] 

机构地区：[1]西安地质矿产研究所,陕西西安710054

出　　处：《地质通报》2012年第12期2001-2014,共14页Geological Bulletin of China

基　　金：中国地质调查局项目<西昆仑-阿尔金成矿带基础地质综合研究>(编号:1212011085034);国家自然科学基金项目<西准噶尔克拉玛依岩体中多种岩浆混合产物的矿物成因及岩浆混合过程的反演>(批准号:41202044);陕西省自然科学基金项目<岩浆混合各阶段产物的锆石微区分析:对西准噶尔花岗岩和铜钼矿的成因以及地壳生长的启示>(编号:2012JM5004)

摘　　要：慕士塔格岩体是西昆仑造山带出露面积最大的侵入岩体,主要由石英二长岩、花岗闪长岩和二长花岗岩组成。岩石地球化学特征显示,该岩体具有较高的SiO2含量和碱度率,低的Al2O3、Fe2O3、MgO、P2O5,稀土元素总量较低,总体上轻重稀土元素分馏明显,富集Rb、Th、K和LREE等大离子亲石元素,亏损Nb、Ta、Sr、P、Ti和HREE等高场强元素,应为高钾钙碱性准铝质—弱过铝质岩石,属于未分异I型-分异I型花岗岩。通过对源岩性质、成因和构造环境的研究,结合区域地质资料,认为该岩体是古特提斯后碰撞伸展环境下,在高温(>839.6℃)低压(<15kbar)环境中壳源变玄武岩发生部分熔融,并伴随着幔源岩浆的参与,经历了以斜长石、磷灰石和钛铁矿为主的分离结晶作用的产物。The Muztagata pluton, the largest granitic intrusion in Western Kunhin orogenic belt, is composed of quartz monzonite, granodiorite and monzonitic granite. The intrusion is characterized by high SiO2 and alkali, low Al2O3, Fe2O3, MgO, P2O5 and ∑REE, enrichment of LILE （Rb, Th, K, LR.EE）, and depletion of HFSE （Nb, Ta, Sr, P, Ti, HREE）. The intrusion can thus be classified as the high-K calc-alkaline series with metahiminous to slightly perahiminous features, belonging to undifferentiated and fractionated I- type granite. Based on a comprehensive analysis of the source region as well as genetic process and tectonic setting of this intrusion, in combination with the regional geological data, it is held that Muztagata intrusion was most likely derived from partial melting of basaltic rocks in the lower crust under the condition of high temperature （〉839.6℃） and low pressure （〈15kbar） in the transitional pe- riod from primary collision to post-collision, and subsequently it underwent the crystallization of plagioclase, apatite and ilmenite to- gether with the injection of mantle-derived magma. In addition, the Western Kunlun granites had the evolutionary characteristic of conversion from I-type to A-type granite during the post-collision of Paleo-Tethys.

关 键 词：岩石地球化学 岩石成因 构造意义 慕士塔格岩体 西昆仑 

分 类 号：P581[天文地球—岩石学]