兴蒙造山带东段清河镇构造混杂岩带晚古生代-早中生代构造演化

The Qinghezhen tectonic mélange belt in Kaiyuan City is located in the west of Kaiyuan-Yanji accretionary complex belt, which is mainly distributed in the north of Shahe fault and the south of Kouhe fault. Qinghezhen tectonic mélange belt is consist of metamorphism and deformation mélanges of different ages and different types, it's the most typical area to research the evolution process and dynamic mechanism of the Xing'an-Mongolian Orogenic Belt. In this project, we plan to take the combination of a variety of technical methods, such as field geological investigation, geological section, large scale geological mapping, petrography, geochemistry, zircon U-Pb geochronology, zircon Lu-Hf isotope analysis, whole-rock Sr-Nd isotope analysis, and so on. By this way to carry out the following research: (1) The material composition, formation age, tectonic setting and contact relationship of the Qinghezhen tectonic mélange belt. (2) Based on the study of structural style, kinematic characteristics, rheological mechanism and tectonic chronology to identify the formation and evolution history of the Qinghezhen tectonic mélange belt. (3) Determining the metamorphic type and age of the accretionary complexes, and the coupling relationship between metamorphic events evolution and the subduction to collision orogeny process. (4) The magmatism and magmatic evolution characteristics during the Late Paleozoic to Early Mesozoic. Ascertaining the material composition, protolith formation, formation age, tectonic attribute and contact relationship of the Qinghezhen tectonic mélange belt, in order to discuss the accretionary orogenesis process and dynamic mechanism in the eastern part of the Xing'an-Mongolian Orogenic Belt during the Late Paleozoic to Early Mesozoic.

清河镇构造混杂岩带位于开原-延吉增生杂岩带西段，主要分布于沙河断裂以北、寇河断裂以南，由不同时代、不同类型变质变形杂岩组成，是研究华北板块北缘兴蒙造山带东段形成演化过程及其动力学机制最为典型区域。本项目拟采用野外路线地质调查、地质剖面测制、大比例尺地质填图、岩相学、岩石地球化学、锆石U-Pb年代学、锆石Lu-Hf同位素和全岩Sr-Nd同位素分析等多种技术手段相结合的方法，开展以下几个方面研究：（1）清河镇增生杂岩带物质组成、形成时代、构造环境和相互接触关系；（2）构造样式、运动学特征、流变机制和构造年代学，确定其形成演化历史；（3）增生杂岩变质作用类型及时代，确定变质事件演化与俯冲、碰撞造山之间的耦合关系；（4）晚古生代-早中生代岩浆活动及其演化特征。查明该构造混杂岩带物质组成、原岩建造、形成时代、构造属性和相互关系，探讨兴蒙造山带东段晚古生代-早中生代大陆边缘增生造山过程及其动力学机制。

清河镇构造混杂岩带位于兴蒙造山带东段南部的开原-延吉增生杂岩带西段，分布于沙河断裂以北、寇河断裂以南，由不同时代、不同类型变质变形杂岩组成，记录古亚洲洋俯冲、闭合、碰撞造山演化过程，是研究中亚造山带形成演化过程及其动力学机制最为典型区域。采用野外路线地质调查、地质剖面测制、大比例尺地质填图、岩相学、岩石地球化学、锆石U-Pb年代学、锆石Lu-Hf同位素和全岩Sr-Nd同位素分析等多种技术手段相结合的方法，对兴蒙造山带形成演化过程及动力学机制进行研究，取得如下认识：（1）清河镇构造混杂岩由岩块与基质两个部分组成，代表古亚洲洋晚古生代-早三叠世向南俯冲增生杂岩，但是被后期地质作用改造破坏，呈断续分布，出露不连续；（2）确立华北板块北缘早古生代造山带存在，建立早古生代弧-陆碰撞造山演化模式，对内蒙古中部、辽北和吉林中部一带早古生代温都尔庙混杂岩、白乃庙岛弧岩浆岩、徐尼乌苏弧后盆地、辽北及吉林中部公主岭早古生代岛弧岩浆岩进行系统研究，查明温都尔庙混杂岩是由洋内俯冲增生杂岩与洋内弧岩浆岩构成，确认早古生代白乃庙岛弧为安第斯型活动大陆边缘岩浆弧，向东延伸至辽北、吉林中东部地区；（3）在公主岭地区新识别出中元古代岩浆岩，为强烈变质变形黑云母花岗闪长质片麻岩，其形成时代为1321±43 Ma ~ 1388±31 Ma，是早古生代白乃庙岛弧前寒武纪基底的一部分，表明该构造带内存在中元古代微陆快；（4）在辽北法库地区新发现一套晚古生代蛇绿岩，为一套SSZ型蛇绿岩，形成于弧后盆地环境，中亚造山带南部在晚泥盆世以来的持续伸展过程中，可能形成了一个幼年期的弧后陆内海洋盆地，最终在早三叠世关闭；（5）确定了古亚洲洋系向古太平洋系的构造转换时间，晚三叠世晚期-早侏罗世转变为古太平洋体系，古太平洋板块开始俯冲。