拉脊山蛇绿混杂带结构组成、形成时代与形成过程
投稿时间:2016-07-27  最后修改时间:2016-08-05  点此下载全文
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作者单位E-mail
付长垒 中国地质科学院矿产资源研究所 fucl815@126.com 
闫臻) 中国地质科学院地质研究所  
基金项目:(编号: 41372207)联合资助。
中文摘要:拉脊山蛇绿混杂带分布于中祁连和南祁连构造带之间,是原特提斯洋演化的产物,自东向西断续出露于药草台林场、六道沟、青沙山和拉脊山口一带;岩石种类相对齐全,具有混杂带“块体(block)+基质(matrix)”典型结构特征。系统路线地质调查研究和关键地段大比例尺地质填图结果共同表明,药草台林场蛇绿混杂带由蛇纹岩基质及裹夹于其中的二辉橄榄岩、方辉橄榄岩、蛇纹岩、斜长角闪岩块体共同组成,且辉绿岩墙侵入于其中。六道沟混杂带可分为南、北2个亚带,其中南亚带由粗面岩和安山岩为主的岩块和强烈片理化玄武岩+安山岩基质共同构成;北亚带为辉石岩、蛇纹岩、辉长岩、辉绿岩、枕状玄武岩和斜长花岗岩块体裹夹于蛇纹岩或者玄武岩+辉绿岩基质中;青沙山混杂带由枕状玄武岩、灰岩、火山质杂砂岩和硅质泥岩共同构成;拉脊山口蛇绿混杂带岩块类型复杂,由橄榄岩、蛇纹岩、堆晶辉长岩、辉绿岩块/岩墙、枕状玄武岩、块状玄武岩、硅质岩等共同组成,其基质包括蛇纹岩和浊积岩两类。这些混杂带主要类型为蛇纹岩基质与各类岩性块体的组合。
中文关键词:拉脊山  混杂带  SSZ型蛇绿岩  活动大陆边缘  构造演化
 
The composition, age and tectonic setting of Lajishan ophiolitc mélange
Abstract:The Lajishankou ophiolitic mélange, which formed during the evolution of Proto-Tethyan Ocean, locates between the Central and the South Qilian tectonic belts and crops out discretly along Yaocaotai, Liudaigou, Qingshashan, and Lajishankou areas. It contains varities of lithological units showing typical of block-in-matrix texture. Results on regional surveying and geological mapping show that the blocks of Yaocaotai mélange consist of lherzolite, harzburgite, serpentinite, and amphibolite, which are encased in the matrix of serpentinite and intruded by dolerite dykes. The Liudaogou ophilitic mélange can be subdivided into two belts. The southern belt is dominated by trachytic, andesitic and foliated basaltic and andesitic matrix, but the northern belt is characterized by blocks with serpentinite or basaltic and doleritic matrix. The blocks in the basaltic and doleritic matrix comprise gabbro, dolerite, pillow basalt, plagiogranite, but these in the serpentinite matrix include peridotite, pyroxenite, dolerite, and plagiogranite. Qingshashan mélange is composed of pillow basalt, limestone, volcaniclastic rocks, chert, and siliceous mudstone. Lajishankou ophiolitic mélange can be subdivided into serpentinite mélange and broken formation. The former consists of serpentinite matrix and blocks of peridotite, serpentinite, cumulate gabbro, dolerite, pillow and massive basalt, and chert, but the latter is characterized by thinner beds of mudstone, shale, chert, and limestone and blocks of conglomerate, pebbly sandstone, quartzarenite, sandy limestone, and chert. These characters demonstrate that serpentinite mélange is the major type of the Lajishan mélange.
keywords:Lajishan  Mélange  SSZ ophiolite  Active continental margin  Tectonic evolution
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