华北东部印支期变形特征:对大陆深俯冲极性的启示

Indosinian deformation in eastern North China:implications for continental deep subduction polarity

华北东部印支期沿苏鲁造山带的俯冲极性长期没有得到解决,为了解决印支期在华北地块东部的大陆俯冲极性问题,本文通过收集前人岩石学、年代学、地球物理等资料,同时结合野外调查工作,分析了印支期徐-淮弧形构造区,渤海湾盆地的黄骅、济阳坳陷,辽东半岛南部以及鲁西地区的构造变形特征。研究揭示:(1)印支期华北东部及其东北地区整体变形轨迹呈波浪状,在大别和渤海湾地区为近E-W向,徐-淮地区和长海地区则为NE向,辽东半岛南部及兴凯—佳木斯—布列亚呈近S-N向;(2)印支期华北地块东缘沿五莲—青岛—烟台断裂带向南东俯冲到华南地块之下;(3)华北板块向SE或向东俯冲过程中,在苏鲁造山带形成一系列向NW逆冲的推覆构造,而在靠近扬子地块一侧形成向SE逆冲的反冲断层;华北地块东南缘与俯冲带的距离不同,构造变形强度也略有不同,较近处(如徐-淮构造带)发育较强烈的逆冲推覆构造,较远处(如济阳、黄骅坳陷)则发育较宽缓的褶皱。

It is still controversial about the Indosinian subduction polarity along the Sulu Orogen in the eastern North China during the period.To solve this problem,this paper synthesized the previous published data including petrology,chronology and geophysics,as well as our field observation.We analyzed the Indosinian deformation in the Xu-Huai thrust-and-fold belt,the Huanghua and Jiyang Depression of the Bohai Bay Basin,the southern Liaodong Peninsula and western Shandong area.The results reveal that（1）the whole structural trajectory in eastern North China and its surrounding areas present a series of curved lines.They present E-W trending trajectory in the Dabie Orogen and the Bohai Bay Basin,NE trending trajectory in the Xu-Huai and Changhai regions,and S-N trending trajectory in the southern Liaodong peninsula and the Bureya-JiamusiKhanka regions;that（2）the southeastern margin of North China Block subducted southeastward under the South China Block along the Wulian-Qingdao-Yantai Fault during the Indosinian period,which resulted in the curved lines mentioned above;that（3）there are a series of NW-ward thrust nappe structures formed in the Sulu Orogen and SE-ward antithetic faults in the Yangtze side during the process of subduction.Moreover,the intensity of deformation varies with a distance of the SE margin of North China to the subduction zone.The regions near the subduction zone,such as the Xu-Huai area,developed intense thrust nappe structures,while the Bohai Bay Basin which is far away from the subduction zone developed gentle folds.