东天山图拉尔根镁铁—超镁铁质岩体辉石矿物学特征及其地质意义  

Mineralogical Characteristics of Pyroxenes from Tulargen Mafic-ultramafic Intrusion in East Tianshan, China and Their Geological Significance

作　　者：刘艳荣 吕新彪[3] 刘民武[1,2] 栾燕[1,2] 王富贵[4] LIU Yan-rong;LYU Xin-biao;LIU Min-wu;LUAN Yan;WANG Fu-gui(School of Earth Science and Resources,Chang an University,Xi'an 710054,Shaanxi,China;Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education,Chang an University,Xi'an 710054,Shaanxi,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,Hubei,China;The Third Institute of Geological and Mineral Exploration,Gansu Provincial Bureau of Geology and Mineral Resources,Lanzhou 730050,Gansu,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]中国地质大学(武汉)资源学院,湖北武汉430074 [4]甘肃省地质矿产勘查开发局第三地质矿产勘查院,甘肃兰州730050

出　　处：《地球科学与环境学报》2019年第4期445-458,共14页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41702062);中央高校基本科研业务费专项资金项目(CHD300102278103)

摘　　要：东天山图拉尔根镁铁—超镁铁质岩体主要包含角闪橄榄岩相、辉石橄榄岩相和辉长岩相,辉石为各岩相主要造岩矿物之一。采用电子探针和LA-ICPMS技术对不同岩相中辉石的主量、微量元素进行测试分析,以探讨岩体的性质、来源和演化过程。东天山图拉尔根镁铁—超镁铁质岩体中斜方辉石属古铜辉石,而单斜辉石则为透辉石和顽透辉石。辉石温压计算表明其结晶温度为978℃~1059℃,结晶压力主要为0.71~4.80kbar。岩体母岩浆为亚碱性拉斑玄武质岩浆,是被俯冲板片交代过的亏损地幔发生13%~20%部分熔融的产物。岩体内不同岩相中辉石的化学成分变化较小,表明岩体的结晶分异程度较低,其中辉长岩相的结晶程度较角闪橄榄岩相和辉石橄榄岩相略高;岩浆上侵过程中,角闪橄榄岩相和辉石橄榄岩相受到富硅地壳物质的混染,而辉长岩相受到富铝围岩的混染。结晶分异作用和富硅地壳的混染是引起图拉尔根岩体硫饱和及硫化物熔离的重要因素。Tulargen mafic-ultramafic intrusion in East Tianshan is composed mainly of amphibole peridotite facies, pyroxene peridotite facies and gabbro facies. Pyroxene, the major rock-forming mineral of the intrusion, is present in almost every lithofacies. In order to have a better understanding of the nature, origin and evolution of the intrusion, the compositions of pyroxene by EPMA and LA-ICPMS were analyzed. The orthopyroxenes from Tulargen mafic-ultramafic intrusion in East Tianshan are bronzites, and the clinopyroxenes are composed of diopside and endiopside. The crystallization temperatures of the pyroxene are from 978 ℃ to 1 059 ℃, and the crystallization pressures range mainly from 0.71 kbar to 4.80 kbar. The primary magma of Tulargen intrusion is sub-alkaline tholeiitic magma, and is the production of 13%-20% partial melting of the depleted mantle metasomated by a subducted slab. The chemical compositions of pyroxenes in different lithofacies change slightly, indicating that Tulargen intrusion experiences a low degree of fractional crystallization, and the crystallization degree of the gabbro facies is slightly higher than that of the amphibole peridotite facies and pyroxene peridotite facies. The gabbro facies and peridotite facies are contaminated by Al-rich and Si-rich rocks, respectively. The fractional crystallization and contamination of Si-rich rocks could be responsible for the sulfur saturation and sulfide segregation.

关 键 词：镁铁-超镁铁质岩体 辉石 地质温压计 母岩浆 部分熔融 结晶分异 地壳混染 东天山 

分 类 号：P588.12[天文地球—岩石学] P57[天文地球—地质学]