东昆仑东段中元古代小庙岩组岩石组合、地球化学特征及构造环境分析!  

Rock Association,Geochemical Characteristics and Tectonic Setting of the Xiaomiao Formation,East Region of East Kunlun Orogenic Belt

作　　者：陈有炘[1] 裴先治[1,2] 李瑞保[1,2] 李佐臣[1,2] 裴磊[3] 刘战庆[4] 陈国超[1] 刘成军[1] 杨杰[1] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]西部矿产资源与地质工程教育部重点实验室,西安710054 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]桂林理工大学地球科学学院,广西桂林541004

出　　处：《地质学报》2014年第6期1038-1054,共17页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41172186;40972136;40572121);高等学校博士学科点专项科研基金项目(编号20110205110004);中央高校基本科研业务费专项资金项目(编号CHD2011TD020;2013G1271091);青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金项目(中铝基金200801)联合资助成果

摘　　要：小庙岩组是东昆仑造山带前寒武纪变质结晶基底的重要组成部分,是一套中元古代角闪岩相变质地层。详细的野外地质和室内观察表明,小庙岩组主要为一套长英质变质岩夹基性变质岩,长英质变质岩可分为4种岩石组合:石英岩组合、富铝片麻岩组合、长英质片麻岩组合、石英岩—长石石英岩组合。岩石学和地球化学研究表明:含富铝矿物石英片岩和片麻岩的原岩为一套泥质岩,石英岩—长石石英岩原岩为砂岩、杂砂岩或硅质岩,角闪岩和斜长角闪岩原岩为拉斑玄武岩;变沉积岩物源区经历中—低风化程度,处于寒冷干旱的气候区,可能为构造活动区;物源区主要为长英质岩石并且母岩中碱性长石含量较少,或混合有基性火山岩;变沉积岩形于陆壳拉张的裂陷槽或裂谷盆地,变基性岩形成于初始裂解或稍晚期的大陆裂谷环境,二者均指示小庙岩组形成于陆内裂谷环境。The Xiaomiao Formation is a set of Mesoproterozoic amphibolite facies metamorphic strata,which are an important part of Precambrian basement exposed in the East Kunlun orogenic belt. The detailed field geological mapping and petrologic studies show that the Xiaomiao Formation is mainly composed of felsic metamorphic rocks,which can be subdivided into four units：quartzite unit,Al-rich gneiss unit, felsic gneiss unit and quartzite-arkose-quartzite unit. Minor basic metamorphic rocks are also included in the felsic metamorphic rocks. Petrologic and geochemical characteristics indicate that the protoliths of quartz-schist and Al-rich gneiss are pelitic rocks,and the protoliths of quartzite and arkose-quartzite are sandstones or greywackes or silicalites,and the protolith of amphibolite is tholeiite. The provenance of metasediment is characterized by mid-low weathering degree which belongs to the cold or drought zone（maybe tectonically active region）. The provenance rocks are dominatly felsic rocks bearing few alkali-feldspar,and possiblely some basic volcanic rock. Taking all factors into account, the metasediment from the Xiaomiao Formation was formed in intra-continental extensional taphrogenic trough or rift basin, and the metabasite was formed in a continental rift environment during initial or late period,which suggested that the Xiaomiao Formation was formed in intra-continental rift environment.

关 键 词：东昆仑东段 小庙岩组 变质岩系 地球化学 原岩恢复 构造背景 

分 类 号：P587[天文地球—岩石学] P583[天文地球—地质学]