对内蒙古贺根山蛇绿岩的新认识  

A further study on the ophiolite in Hegenshan,Inner Mongolia

作　　者：邵济安[1] 张丽莉[2] 周新华[3,4] 张履桥 唐克东 SHAO JiAn;ZHANG LiLi;ZHOU XinHua;ZHANG LvQiao;TANG KeDong(MOE Key Laboratory of Orogenic Belts and Crustal Evolution,School of Earth and Space Sciences,Beijing 100871,China;Key Laboratory of Petroleum Resources Research,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Geological Bureau of Inner Mongolia,Huhehot 010020,China;Shenyang Institute of Geology and Mineral Resource,Shenyang 110034,China)

机构地区：[1]造山带与地壳演化教育部重点实验室,北京大学地球与空间科学学院,北京100871 [2]中国科学院地质与地球物理研究所,中国科学院油气资源研究重点实验室,北京100029 [3]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [4]中国科学院大学地球与行星科学学院,北京100049 [5]内蒙古地质研究所,呼和浩特010020 [6]沈阳地质矿产研究所,沈阳110034

出　　处：《岩石学报》2019年第9期2864-2872,共9页Acta Petrologica Sinica

基　　金：中国地质调查项目(121201102000150009);国家重点研发计划专项(2017YFC0601206)联合资助

摘　　要：本文将华北板块和中亚-蒙古陆块缝合带中前人划分的"贺根山蛇绿岩套"划分为三个不同组分、不同成因的岩系:以含金刚石和其它幔源矿物的变质橄榄岩系为主,包括堆晶杂岩在内的镁铁-超镁铁岩系;含放射虫硅质岩夹层的玄武岩系;上覆的火山-沉积岩系。根据地质学与年代学证据,可以认为蛇绿岩形成于晚泥盆-早石炭世。在此基础上,本文重点讨论了三个问题:(1)结合不同尺度的构造研究,将含金刚石等幔源矿物的超镁铁岩看作源自地幔转换带的幔源熔-流体,在软流圈底辟体上涌的背景下持续上升,在板块对接的过程中构造侵位的岩石。据此,对现有的蛇绿岩概念提出了补充;同时提出贺根山在板块汇聚过程未发生明显的俯冲和碰撞,而是通过拼贴的方式连为一体的;(2)贺根山具有OIB特征的玄武岩与朝克山MORB的对比,表明不同来源的多地块的存在及板块闭合时间的差异均反映了陆间小洋盆的特征;(3)将上覆在玄武岩系之上的火山沉积岩系看作洋盆最后充填的产物,反映了古亚洲洋闭合过程中小洋盆直接从洋壳转化为陆壳的过程,最后从时空角度进一步讨论了小洋盆闭合的特征。The previously termed as"Hegenshan ophiolite suite",a composite rock suite,in the suture zone between North China block( plate) and Central Asian-Mongolia continental block has been divided into three rock series with different constituents and different genesis by this study:( 1) mafic-ultramafic rocks,mainly composed of meta-peridotite series with diamonds and other mantlederived minerals,also including cumulate complex;( 2) a basalt series intercalated with radiolarian siliceous rocks;and( 3) an overlying volcanic-sedimentary rock series. Based on the evidences from geology and geochronology,the Hegenshan ophiolite can be considered as formed in Late Devonian-Early Carboniferous. On this basis,three issues have been focused by this article:( 1)combined with structural geology studies in different scales,the mafic-ultramafic rocks containing diamonds and other mantle-derived minerals can be regarded as tectonic emplacement rocks,derived from deep melt-fluids,which continuously rising up from mantle transitional zone as the asthenosphere upwelling diapirs during the plate converge process. Hereby,the traditional concept of ophiolite has been extended,and it is postulated that two plates converged by amalgamate process to unify,instead of obvious subduction or collision in Hegenshan region;( 2) comparison of the Hegenshan OIB-type basalts with the Chaogenshan MORB-type basalts indicates that the existence of multiple massifs derived from different sources and the time difference between plates closure is one of the characteristics of the small intercontinental ocean basins;( 3) the volcanic-sedimentary rocks overlying on basalt series has been regarded as the final stage products of filling-in the ocean basin,which demonstrates the direct transform process from oceanic crust to continental crust in small-medium intercontinental ocean basins during closure of the paleo-Asian ocean. Finally,the temporal and spatial characteristics of closure of small oceanic basin are discussed.

关 键 词：缝合带 镁铁-超镁铁岩 玄武岩 上覆岩系 小洋盆闭合 贺根山 

分 类 号：P542[天文地球—构造地质学] P588.125[天文地球—地质学]