鲁西七星台地区韧性剪切带变形特征及样式:对华北克拉通东部新太古代演化的构造约束  

Deformational characteristics of the Qixingtai ductile shear zone,western Shandong:Implications for the Neoarchean tectonic evolution of the eastern North China Craton

作　　者：张书慧 张健 赵辰[3] 苗亚洲 刘晓光 陈国楷 ZHANG ShuHui;ZHANG Jian;ZHAO Chen;MIAO YaZhou;LIU XiaoGuang;CHEN GuoKai(School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519000,China;Department of Earth Sciences,University of Hong Kong,Hong Kong,China;Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China)

机构地区：[1]中山大学地球科学与工程学院,珠海519000 [2]香港大学地球科学系,中国香港 [3]中国地质调查局沈阳地质调查中心,沈阳110034 [4]山东科技大学地球科学与工程学院,青岛266590

出　　处：《岩石学报》2025年第1期237-259,共23页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42025204、42302221)资助.

摘　　要：鲁西地区是华北克拉通东部陆块的重要组成部分,整体呈NW-SE向带状展布,保留有完整的新太古代地质记录和丰富的新太古代构造样式,对深入研究华北克拉通新太古代构造演化历史具有重要意义。过去的研究主要集中于地球化学、年代学、变质岩石学等方面,但在构造地质学方面缺乏详细的证据制约。七星台地区位于鲁西西北部,新太古代不同岩性均有出露,保留丰富新太古代时期构造,是研究鲁西地壳形成与演化的经典地区。因此,本文选择在该地区进行了详细的野外构造解析、显微构造分析以及有限应变测量和地质年代学研究。详细野外填图揭示七星台韧性剪切带整体呈NW-SE向展布,剪切带内面理产状近直立,并且发育近水平矿物拉伸线理,而剪切运动学标志不发育。两条代表性构造剖面表明,在二长花岗岩体西侧与新太古代晚期TTG岩石构造接触区域,二长花岗岩为S-L构造岩发育糜棱面理,向东侧变形程度逐渐降低且最终变为块状构造。两条剖面中岩石分布及变形特征相似,不同变形程度的岩石间无明显界限,表明该地区带状分布的近直立岩石面理可能为水平向挤压所致。镜下显微特征也显示变形强度自西向东逐渐减弱的相似趋势,在变形二长花岗岩中普遍存在由强烈拉长的石英颗粒形成的多晶条带,矿物变形行为表明变形温度约450~550℃。利用三种不同方法获得的岩石有限应变测量结果和Flinn图解表明岩石应变类型为压扁型应变。应变强度分布图也显示岩石应变强度中间最强,向东远离构造接触带则呈逐渐降低趋势。LA-ICP-MS锆石U-Pb定年结果显示七星台二长花岗岩形成时代为~2525Ma,结合前人研究,认为鲁西七星台地区变形时代约为2525~2500Ma。综上所述,鲁西地区在新太古代晚期经历了近NE-SW向水平压扁应变和近NW-SE向水平拉伸应变,指示新太古代晚期水平The western Shandong is a prominent part of the Eastern Block of the North China Craton and preserves extensive Archean geological records with distinctive tectonic pattern.Previous studies have primarily focused on geochemistry,geochronology,and metamorphic petrology,but there is a lack of detailed structural evidence.The Qixingtai region,located in the northwest of western Shandong,provides a key exposure of diverse Neoarchean rocks and abundant Neoarchean structural features,which thus represents a pivotal region for studying the formation and evolution of western Shandong.This study presents an integrated field-based structural analysis,microscopic structural analysis,finite strain measurements,and geological chronology in the Qixingtai region.Detailed field mapping reveals that the Qixingtai ductile shear zone strikes NW-SE with nearly vertical foliation and sub-horizontal mineral stretching lineations,while distinct kinematic indicators for simple shear are absent.We conducted two representative structural profiles and found that the western side of monzogranite,in contact with the Late Neoarchean TTG rocks,exhibits mylonitic foliations.Towards east,the deformation intensity gradually decreases,eventually transitioning into massive structures.The distribution of rocks and their deformation characteristics along the two profiles show similarities.This observation suggests a significant horizontal compression,resulting in the localization of high-strain deformation.Microstructures also reveal a progressive transition of deformation intensity from west to east.Intensely elongated quartz grains are widespread in strongly deformed monzogranitic gneisses.Microstructural features indicate that the deformation temperature ranges from 450℃to 550℃.Finite strain measurement results,obtained through three different methods,along with Flinn diagrams,illustrate a pancake-like dominated flattening deformation,indicating that the rocks belong to the S-L tectonite.The strain intensity decreases obviously towards east.LA

关 键 词：新太古代晚期 七星台韧性剪切带 二长花岗岩 有限应变测量 鲁西 

分 类 号：P542[天文地球—构造地质学] P583[天文地球—地质学] P597.3