西准噶尔达尔布特SSZ型蛇绿杂岩的地球化学证据及构造意义  

Geochemical Evidences and Tectonic Significances of Dalabute SSZ-type Ophiolitic Mélange,Western Junggar Basin

作　　者：辜平阳[1,2] 李永军[2] 王晓刚[3] 张洪伟[3] 王军年[3] 

机构地区：[1]中国地质调查局西安地质矿产研究所,西安710054 [2]长安大学地球科学与资源学院,西部矿产资源与地质工程教育部重点实验室,西安710054 [3]新疆地质矿产勘查开发局地质七队,新疆乌苏833000

出　　处：《地质论评》2011年第1期36-44,共9页Geological Review

基　　金：国家青年基金项目(编号41002063);中国地质调查局“青藏高原前寒武纪地质和古生代构造-古地理综合研究”项目(编号1212010610102);新疆维吾尔自治区地质矿产调查项目(编号XJZBKD2006-3)的成果

摘　　要：西准噶尔达尔布特蛇绿杂岩中的蛇纹岩,表现为低TiO2、Al2O3、CaO和全碱,富MgO、Mg#值高,稀土总量(∑REE)低、LREE富集、稀土配分曲线呈"凹"型或"U"型,是原始地幔发生部分熔融的亏损地幔岩。辉长岩、玄武岩特征为稀土总量(∑REE)较低、轻稀土(LREE)亏损、高场强元素不分异,类似于N-MORB;同时不同程度地富集大离子亲石元素LILE,亏损Nb、Ta等。表明该蛇绿杂岩是较为典型的消减带(SSZ)型蛇绿岩,结合新获得的391±6Ma的同位素年龄分析,在中泥盆世,西准噶尔主洋盆已开始消减,大陆板块已开始汇聚。The serpentinite of Dalabute ophiolitic mélange shows low TiO2,Al2O3,CaO and total alkali,high MgO,Mg^#; and has low ∑REE,is enriched in LREE,the rare earth element distribution patterns appear ＂凹＂ or ＂U＂. It is a depletion pyrolite form primitive mantle which had undergone partial melting. The geochemical of gabbo and basalt characteristics of low ∑REE,depleted in LREE and unfractionated in HSF elements indicate that it is similar to a normal mid-ocean basalt （N-MORB）,meanwhile,the samples are enriched in large-ion lithophile elements（LILE）,depeleted in Nb and Ta on different degrees. It is indicated that the Dalabute ophiolitic mélange is a typical SSZ-type ophiolite,associating with the new isotope age （391±6Ma）,it is concluded that the main Western Junggar oceanic basin has begun to eliminate,and the continental plate has begun to converge in Middle Devonian.

关 键 词：达尔布特蛇绿杂岩 地球化学 构造环境 弧后盆地 西准噶尔 新疆 

分 类 号：P588.323[天文地球—岩石学]