2012年12月，第18卷，第4期，661-675页 December2012，Vol.18，No.4，p.661-675
高校地质学报
Geological Journal of China Universities
新疆尾亚蛇绿混杂岩与镁铁质麻粒岩地球
化学特征及构造意义陈希节，舒良树，马绪宣
南京大学内生金属矿床成矿机制研究国家重点实验室，地球科学与工程学院，南京210093
摘要：在中天山北缘断裂带的哈密尾亚地区出露有蛇绿混杂岩和镁铁质麻粒岩。蛇绿混杂岩呈近东西带状分布，在约2km 宽度范围内见有蛇纹岩、辉绿岩、辉长岩以及硅质岩等，均呈构造岩块裹换在强烈剪切的泥砂质基质中镁铁质麻粒岩呈透镜状出现在片岩和片麻岩、花岗质片麻岩中，并被后期君浆岩侵人。岩石地球化学测试数据表明，辉长岩与辉绿岩成分相近，
LREE轻微富集，HFSE分异差，不相容元素较富集。总体上具有富集型洋脊玄武岩（EMORB）地球化学特征。镁铁质麻粒岩的Si0，含量为45%~47%，K,0+Na,0为0.26%~0.79%，Ca0为22.9%~24.3%，Al,0,含量介于10.9%~13.9%之间。在TAS图中，落在亚碱性辉长-辉绿岩区，Ti0，含量在1.18%~1.47%之间，与岛弧和活动大陆边缘玄武岩相当，其原岩为不成熟岛弧环境下形成的拉斑玄武岩。在微量元素上，5组镁铁质麻粒岩均有较高的REE，REE配分曲线呈平坦型，LREE富集。在主量和微量元索构造环境判别图解中，9件辉长岩-辉绿岩和5件麻粒岩分别落在EMORB和岛弧拉斑玄武岩（IAT）区域。综合区域地质、岩石学和地球化学研究结果，认为尾亚东的镁铁质-超镁铁质岩石组合属于构造肢解的EMORB型蛇绿岩成员，形成于古洋盆初始裂解阶段的洋中脊构造环境，可能是属于古天山洋盆的岩石圈残片。尾亚西的镁铁质麻粒岩其原岩形成于不成熟的岛弧环境。它们的存在表明中天山北缘曾发生古板块俯冲消减机制，其分布位置可以代表古天山洋闭合后的缝合线。
关键词：蛇绿混杂岩；镁铁质麻粒岩；地球化学；构造演化；中天山北缘断裂；哈密尾亚
中图分类号：P548；P595；P588.145
文献标识码：A
文章编号：1006-7493（2012)04-0661-15
GeochemicalFeaturesandTectonicSignificancesofWeiyaOphioliticMélange
and MaficGranulite,Xinjiang CHENXijie,SHULiangshu,MAXuxuan
State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering
Nanjing University, Nanjing 210093, China
Abstract: The ophiolitic melange and mafic granulites are outcropped in the Weiya segment which is near to the norther boundary fault of the Central Tianshan belt. The sub-EW-striking ophiolitic melange 2 km wide is located about 8 km east of the Weiya railway station. It is composed of various blocks such as serpentinite, diabase, gabbro and siliceous rocks. All these blocks are flattened parallel to the regional metamorphic foliation and thus had likely experienced the same deformation as their country rocks (sandy and muddy phyllites and schists). The mafic granulites are situated about 8 km west of Weiya and occur in the schists and gneisses as lenticular blocks, which were intruded by later stage granitic plutons. The petrological and geochemical data suggest that the geochemical features of the diabase and gabbro of the ophiolitic melange are similar, characterized by high
收稿日期：2011-05-02；修回日期：2011-11-16
（0）
项目（2008-1-01）资助
作者简介：陈希节，男，1986年生，博士研究生，构造地质学专业；E-mail:xijiechen2008@gmail.com
"通讯作者：舒良树，男，1951年生，教授，博士生导师，构造地质学专业；E-mail:Isshu2003@yahoo.com.cr