西秦岭南缘勉略构造带主要地质特征  

Main geological features of the Mianlue tectonic belt on the southern margin of the West Qinling

作　　者：裴先治[1,2] 张国伟[1] 赖绍聪[1] 李勇[1,2] 陈亮[1] 高明[1] 

机构地区：[1]西北大学地质学系 [2]长安大学地球科学学院,陕西西安710054

出　　处：《地质通报》2002年第8期486-494,共9页Geological Bulletin of China

基　　金：国家自然科学基金项目(49732080);中国地质调查局地质调查项目(200013000154);国土资源部"十五"重点科技项目(20010201)资助。

摘　　要：西秦岭勉略构造带现今呈近东西—北西西向展布,是以自北而南多层次叠瓦状逆冲推覆构造为骨架的向南突出的巨型复合断裂弧形构造带。该带原为西秦岭微板块与扬子板块之间的古缝合带,发育有俯冲和碰撞两期变形构造,以主造山碰撞晚期的自北向南的逆冲推覆构造为显著特征。初步确定发育OIB以及N-MORB和E-MORB型玄武岩,代表了洋盆发育的物质记录。根据已有的年代学和古生物化石研究结果,认为于泥盆纪晚期—早石炭世(D3—C1)沿勉略带发育有以蛇绿岩、洋岛玄武岩为代表的有限洋盆。在勉略带扩张打开形成有限洋盆与消减俯冲过程中,南侧发育有被动陆缘盆地沉积体系,北侧发育有深水裂陷盆地和活动陆缘盆地沉积体系。进而确定勉略带是一条重要的东古特提斯北侧分支洋盆俯冲消减碰撞缝合带和中国大陆印支期完成其主体拼合的主要结合带之一。The present nearly E-W-to WNW-trending Mianlue tectonic belt in West Qinling is a gigan-tic,south-convex,composite fault arcuate tectonic belt with the south-vergent ,multilayerd,imbricated thrust nappe structure as the framework.It was originally a paleo-suture zone between the West Qinling microplate and Yangtze plate,where two phases of deformation corresponding to subducting and collision respectively took place.This tectonic belt is featured by south-verging thrust nappe structure occurring in the late main collisional orogenic stage.In the belt,OIB,N-MORB and even E-MORB are also pre-liminarily recognized;they record the evolutionary history of an oceanic basin.The chronological and pale-ontological studies available suggest that a restricted oceanic basin represented by ophiolite and OIB devel-oped along the Mianlue suture zone in the Late Devonian-Early Carboniferous.While the Mianlue belt opened to form a restricted ocean basin and the basin was subducted,a passive continental-margin basin sedimentary system and an active continental-margin basin sedimentary system were developed on the north side and south side of the belt respectively.Then it is further determined that the Mianlue belt is an im-portant subduction-collision suture zone of the north branch of the eastern Paleo-Tethys,representing the main junction zone occurring when the amalgamation of the North China block with the Yangtze block was completed in the Indosinian.

关 键 词：秦岭 勉略构造带 古缝合带 东古特提斯 年代学 蛇绿岩 古生物化石 

分 类 号：P542[天文地球—构造地质学]