伊犁地块北缘温泉地区托克赛岩组的构造变形与年代学研究及其地质意义  

Structural Features and Zircon U-Pb Ages of the Tuokesai Formation in the Wenquan Area,Northern Yili Block,and Their Geological Significances

作　　者：邓聚 王博[1] 刘珈硕 宋芳 倪兴华 李盈莹 DENG Ju;WANG Bo;LIU Jiashuo;SONG Fang;NI Xinghua;LI Yingying(State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,Jiangsu,China)

机构地区：[1]南京大学地球科学与工程学院,内生金属矿床成矿机制研究国家重点实验室,江苏南京210023

出　　处：《大地构造与成矿学》2023年第3期484-505,I0024-I0038,共37页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42161144013、41772225、41390445)资助。

摘　　要：伊犁地块是中亚造山带西南缘的主要大陆块体之一,记录了新元古代‒古生代多期岩浆活动、复杂构造变形和高级变质作用,是研究天山乃至中亚造山带构造演化的理想场所。本文对位于伊犁地块北缘的温泉地区托克赛岩组中石榴角闪岩、花岗片麻岩、云母片岩、石英片岩和侵入其中的未变形花岗岩脉进行了详细的野外构造分析和岩相学观察,发现石榴角闪岩主要分布在一条近EW走向的韧性剪切带中,与其共生的花岗片麻岩、云母片岩和石英片岩均发生了强烈韧性变形,发育一致的陡立面理和近水平线理,运动学指示右旋走滑剪切变形。锆石U-Pb年代学研究显示,韧性变形的角闪岩中变质重结晶锆石具有453±4 Ma和414±4 Ma两个主要年龄值,其中前者与云母片岩中热液改造成因的锆石年龄(465±7 Ma)基本一致,代表这些岩石经历了高角闪岩相变质作用,该变质事件与温泉地区中奥陶世陆缘弧岩浆作用同期。角闪岩中较年轻的年龄峰值与石英片岩(408±3 Ma)和花岗片麻岩(399±7 Ma)中热液成因的锆石生长边,以及花岗岩脉(394±5 Ma)的年龄在误差范围内基本一致,代表了岩浆热液作用的时代,该事件与伊犁北缘泥盆纪岩浆弧花岗岩的侵入时代相当。同时,在角闪岩和花岗片麻岩中均获得了~900 Ma和~780 Ma两个年龄峰值,分别代表花岗片麻岩和角闪岩的原岩结晶时代。此外,石英片岩和云母片岩中锆石的核部还给出了~1135 Ma、~1286 Ma、~1517 Ma和~1725 Ma共4个中元古代的年龄峰值,代表其原岩物源区的岩浆事件。结合前人研究结果,笔者认为伊犁北缘温泉地区在463~443 Ma和423~395 Ma期间分别经历了两期俯冲相关的岩浆‒变质和岩浆‒热液事件,是认识准噶尔洋早古生代向伊犁地块俯冲作用的重要依据。The Yili Block is one of the main continental blocks in the southwestern Central Asian Orogenic Belt(CAOB);and it recorded Neoproterozoic and Paleozoic multi-stage magmatism,structural deformation,and high-grade metamorphism.Thus,it is an ideal place to study the tectonic evolution of the Tianshan Orogenic Belt and the CAOB.Field observation,petrographic analysis,and zircon geochronological study were conducted on the garnet-bearing amphibolites,orthogneisses,mica schists,quartz schists,and undeformed granitic dykes of the Tuokesai Formation in the Wenquan area.The garnet amphibolites occur mainly in a nearly east-west-striking ductile shear zone,whereas the associated orthogneisses,mica schists,and quartz schists all experienced strong ductile deformation,exhibiting steep foliation and sub-horizontal lineation with kinematic indicators suggestive of a dextral strike-slip shearing.The metamorphic recrystallized zircon grains from the deformed amphibolites have two major ages of 453±4 Ma and 414±4 Ma.The former is consistent with the age of hydrothermal zircon from the mica schist(465±7 Ma),indicating the amphibolite-facies metamorphism of these rocks is contemporaneous with the Middle Ordovician arc magmatism in the Wenquan area.The younger age of the amphibolites corresponds to the age of hydrothermal zircon rims in the quartz schist(408±3 Ma),orthogneiss(399±7 Ma),and granitic dyke(394±5 Ma),showing that the timing of the magmatic-hydrothermal event is also comparable to the age of the Devonian magmatic arc granite in the Wenquan area.In addition,two age peaks of ca.780 Ma and ca.900 Ma were obtained from both the amphibolites and orthogneisses,which may represent the protolith ages of the amphibolites and orthogneisses,respectively.Furthermore,zircon magmatic cores from the quartz schist and mica schist have four Mesoproterozoic age peaks of ca.1135 Ma,ca.1286 Ma,ca.1517 Ma and ca.1725 Ma,representing magmatic events in the provenance areas of the metamorphosed sediments.Combined with the previous result

关 键 词：中亚造山带 天山造山带 伊犁地块 温泉变质杂岩 锆石年代学 构造变形 角闪岩相变质作用 

分 类 号：P542[天文地球—构造地质学] P597[天文地球—地质学]