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五台山早元古代碰撞造山带初步认识
引用本文:李继亮,王凯怡.五台山早元古代碰撞造山带初步认识[J].地质科学,1990,0(1):1-11.
作者姓名:李继亮  王凯怡
作者单位:中国科学院地质研究所
摘    要:五台山地区分布着复杂的变质杂岩。过去人们把这些变质岩作为地层分成群组段。龙泉关剪切构造岩的发现突破了这种传统观念。野外工作中发现所谓五台群主要包含了三个蛇绿混杂带;阜平群和恒山群的主要成分是灰片麻岩,它们构成两个太古代陆块的基底。五台地区的花岗岩类由代表弧环境的双花岗岩带的I型和S型花岗岩组成,它们与变质的钙碱性火山岩代表了古代的岩浆弧。滹沱群的豆村和东冶亚群以及过去划入阜平群和五台群的某些变沉积岩是阜平陆块被动大陆边缘的沉积。滹沱群的郭家寨亚群则是前陆盆地的磨拉石沉积。因此可以认为,这是一个由恒山仰冲陆块、北台-车厂弧和阜平俯冲陆块构成的碰撞造山带,碰撞时间大致是距今2050Ma。闭合的弧前大洋和弧后盆地形成了三条蛇绿混杂带。

关 键 词:早元古代碰撞造山带  灰片麻岩  大陆基底  蛇绿混杂带  双花岗岩带  被动  边缘沉积  磨拉石  大地构造演化
收稿时间:1988-11-01
修稿时间:1988-11-01;

EARLY PROTEROZOIC COLLISION OROGENIC BELT IN WUTAISHAN AREA, CHINA
Li Jiliang Wang Kaiyi Wang Qingchen Liu Xiaohan Zhao Zhongyan.EARLY PROTEROZOIC COLLISION OROGENIC BELT IN WUTAISHAN AREA, CHINA[J].Chinese Journal of Geology,1990,0(1):1-11.
Authors:Li Jiliang Wang Kaiyi Wang Qingchen Liu Xiaohan Zhao Zhongyan
Affiliation:Institute of Geology, Academia Sinica, Beijing
Abstract:In Wutaishan area, there are very complicated metamorphic complex, of which the ages-range from Archaean to Early Proterozoic. During past years, geologists have traditionally regarded these metamorphic rocks as metamorphic strata and divided them into the Fuping, Wu-tai, Longquanguan, Hengshan and Hutuo Groups. Recent years, it has been found that the so-called Longquanguan Group is characterized a series of tectonites composed mainly of different kinds of mylonites. The authors made field work to examine the tectonic implications of the Longquanguan tectonite. During the field observation, the authors found that the Wu-tai Group can be divided into three zones of melonge besides the lowest formation (Banyu-kou Formation) which were the passiv marginal deposits. The grey gneisses in the Fuping and Hengshan Groups represent the crystalline basements of two Archaean continental blocks and the gneissic granitoids in Wutaishan area belong to double granite belts of an Archaean island arc. In the light of such a framwork, an Early Proterozoic continent-arc-continent collision orogenic belt can be recognizedThe south melange zone metamorphosed into amphibolite facies consists of serpentinized peridotite, pyroxenite, metamorphosed gabbro and basalt, and chert exotic blocks with metamorphosed flysch matrix. According to the petrochemical analysis, the metamorphosed basal was originally ocean floor tholliite. tt can be inferred that the metamorphosed ophiolitic me-lage was derived from a forearr accretion complex. The middle melange zone metamorphosed into greenschist is composed of serpentinite, pyroxenite, metamorphosed gabbro, diabase, pillow lava and chert with metamorphosed flysch matlix. The pillow lave is characterized by the lower TiO2 (avevage 0.75%), higher Al2O3(15%) and flat REE pattern. It is supposed that the middle ophiolitic melange was originally from oceanic lithosphere of the: back-arc basin. The fact that the melange thrust sheets overthrusted onto calc-alkaline valcanics provides the supporting evidence. The north melange zone metamorphosed into granulite facies is the product of a root zone, in which the ophiolitic blocks were also from back-arc basin.The gneissic granotoids such as Ekou, Wangjiahui, Cheku-Beitai and Guangmingsi granites contain both 1-and S-type granites which formed a series thrust sheets. These granites constitute the double granite belt making up the main body of an island arc with the associated calcalkaline volcanics.The marble and metamorphosed elastics in Baiyukou Formation, Fuping and Hutuo Groups were the passive marginal deposits on Fuping Continental Block. During the collision (about 2050 Ma ags) between the Fuping Block and arc terrain, the passive marginal deposits became a foreland fold-thrust belt and the thrust tectonics developed along the Longquanguan decollement. In the mean time, a forland mollasse basin developed and was filled with Guojia-gou molass deposit.After the forearc collision, the back-arc oceanic lithosphere started subduction beneath the Hengshan Block. At about 1900 Ma ago, the Hengshan Block came into collision with the arc terrain and the middle melange zone overthrust onto the arc. The nappes from Hengshan Block overlapped on the melange zone, which led the later to metamorphose into granulite facies. After the collision orogeny the deformation and uplifting continued untill 1600 Ma ago when the orogenic belt subsided and the sinian sediments deposited.
Keywords:early proterozoic collision orogenic belt  grey gneiss  continental base-ment  ophiolite melange  double granite belt  passive marginal sediments  molasse  tectonic evolu-tion
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