西昆仑西段库尔干退变榴辉岩地球化学特征及大地构造意义  

Geochemistry and Tectonic Significance of Degraded Eclogites in Kuergan Area,Western Part of the West Kunlun

作　　者：杜保峰[1,2] 张荣臻 胡红雷 何玉良 刘品德[1] 程兴国 Du Baofeng;Zhang Rongzhen;Hu Honglei;He Yuliang;Liu Pinde;Cheng Xingguo(Henan Institute of Geological Survey,Zhengzhou,henan,450001,China;Henan Key Laboratory of Metal Mineral Mineralization Geological Processes and Resource Utilization,Zhengzhou,henan,450001,China;Henan Institute of Geological Sciences,Zhengzhou,henan,450001,China)

机构地区：[1]河南省地质调查院,河南郑州450001 [2]河南省金属矿产成矿地质过程与资源利用重点实验室,河南郑州450001 [3]河南省地质科学研究所,河南郑州450001

出　　处：《新疆地质》2022年第2期168-175,共8页Xinjiang Geology

基　　金：中央返还新疆地质勘查基金基础类项目(K15-1-LQ01)资助。

摘　　要：西昆仑西段库尔干一带新识别出退变榴辉岩,呈透镜状、团块状被三叠纪花岗岩包裹,岩石中发育石榴子石+辉石+金红石+石英的高压变质矿物组合,可见减压分解结构和“白眼圈”结构。岩石地球化学显示,退变榴辉岩SiO2含量45.19%~48.23%,Na2O+K2O为1.44%~3.82%,Al2O3为14.0%~17.19%,TiO2为0.48%~1.94%,原岩属拉斑玄武岩系列。稀土分布模式具轻稀土富集的弱Eu异常、右倾斜特征,微量元素Th,U明显富集,Ti,Nb呈亏损,具岛弧玄武岩特征。原岩为基性火山岩或侵入岩,形成于大陆边缘环境,经地壳物质混染。退变榴辉岩LA-ICP-MS锆石U-Pb年龄分为两组:429 Ma左右限制了西昆仑地区原特提斯洋闭合后陆壳深俯冲-碰撞时代不晚于中志留世;228.4 Ma左右代表三叠纪古特提斯洋闭合后的一次强烈构造-岩浆活动事件。该认识对深入探索西昆仑造山带构造演化具重要意义。Several degraded eclogites were recently recognized in the Kurgan area,in western part of West Kunlun.In the field,Degraded eclogites occurs in lenticular and massive surrounded by granites in Triassic.Typical high-pressure metamorphic mineral assemblage in the eclogites consists of garnets+clinopyroxene+rutile+quartz,and also decompres-sion texture and"white eye"texture can be seen.The degraded eclogites geochemistry analyses shows that SiO2 contents range from 45.19%to 48.23%,Na2O+K2O contents range from 1.44%to 3.82%,Al2O3 contents range from 14.0%to 17.19%,TiO2 contents range from 0.48%to 1.94%,and their protolith are tholeiitic basalt.The REE distribution patterns mainly shows the weak Eu anomaly and right-leaning characteristics of LREE enrichment.Th and U of trace elements are obviously enriched,but Ti and Nb are depleted.The degraded eclogites should be the characteristics of IAB in the continental marginal setting,and protolith may be basic intrusive or volcanic rock and contaminated with crustal materi-al.The LA-ICP-MS zircon U-Pb age of degraded eclogite is divided into two groups:429 Ma limits that the deep-sub-duction or collision of the continental crust was not later than Middle-Silurian after the closure of the Proto-Tethys Ocean in the West Kunlun.Approximately 228.4 Ma represents a powerful tectonic-magma thermal events following the closure of the Paleo-Tethys Ocean in Triassic.This achievement has been a important significance for the subsequent study of the tectonic evolution in the West Kunlun Orogenic Belt.

关 键 词：西昆仑西段 退变榴辉岩 岩石地球化学 年代学 构造意义 

分 类 号：P588.3[天文地球—岩石学]