大兴安岭北段扎兰屯地区晚古生代早期花岗质岩浆作用——对额尔古纳-兴安地块和松嫩地块拼合时限的制约  

The Early Late-Paleozoic Granitic Magmatism in the Zalantun Region,Northern Great Xing'an Range,NE China:Constraints on the Timing of Amalgamation of Erguna-Xing'an and Songnen Blocks

作　　者：钱程[1] 陆露[2,3] 秦涛 李林川[1] 陈会军[1] 崔天日[1] 江斌[1] 那福超[1] 孙巍[1] 汪岩[1] 吴新伟[1] 马永非[1] QIAN Cheng;LU Lu;QIN Tao;LI Linchuan;CHEN Huijun;CUI Tianri;JIANG Bin;NA Fuchao;SUN Wei;WANG Yan;WU Xinwei;MA Yongfei(Shenyang Geological Survey Center,China Geological Survey（CGS）,Shenyang,110034;College of Paleontology,Shenyang Normal University,Shenyang,110034;Key Laboratory of Evolution of Past Life in Northeast Asia,Ministry of Land and Resources,Shenyang,110034)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]沈阳师范大学古生物学院,沈阳110034 [3]东北亚古生物演化重点实验室,沈阳110034

出　　处：《地质学报》2018年第11期2190-2214,共25页Acta Geologica Sinica

基　　金：中国地质调查局项目(编号DD20160048-01,12120114085601,12120113054100,DD20160345-17,1212011220435)资助成果

摘　　要：扎兰屯地区位于二连-贺根山-黑河构造带中段,区内发育韧性变形叠加的晚古生代早期花岗岩类。本文在详尽的野外地质调查基础上,对该套花岗岩类的锆石U-Pb年代学和地球化学进行系统分析,研究其成岩年代序列,探讨岩石成因及构造背景,厘定韧性构造叠加的时限,进一步揭示扎兰屯地区额尔古纳-兴安地块和松嫩地块的拼合过程,为兴蒙造山带的区域构造演化研究提供新材料。大量年代学研究显示,扎兰屯地区晚古生代早期花岗质岩浆作用发生于405～325Ma之间,该作用可进一步细化为早中泥盆世(Ⅰ期、405～380Ma)、晚泥盆世—早石炭世初(Ⅱ期、365～350Ma)和早石炭世晚期(Ⅲ期335～325Ma)等3期。其中Ⅰ期和Ⅱ期花岗岩类属高钾—钾玄质钙碱性、准铝质—弱过铝质花岗岩类,可能为俯冲背景下岛弧岩浆活动形成的I型-分异I型花岗岩;Ⅲ期花岗岩类属中—高钾钙碱性、准铝质—弱过铝质花岗岩类,可能为后碰撞背景下岩浆活动形成的分异I型-A型花岗岩。该套花岗岩类普遍叠加韧性变形,可能为碰撞后侧向逃逸作用的产物,变形时限为晚石炭世末—早二叠世(308～290Ma)。大兴安岭北段晚古生代早期花岗质岩浆作用与额尔古纳-兴安地块和松嫩地块的碰撞拼合作用有关,扎兰屯地区二者的碰撞拼合时限可能为早石炭世中期。The Zalantun region,located in the middle part of the Erlian-Hegenshan-Heihe suture belt,contains well-developed early Late-Paleozoic granitoids superimposed by ductile deformation.Through field investigation and systematic analyses,such as microscopy,geochemistry and zircon U-Pb geochronology,we investigated rock-forming chronological sequence,petrogenesis and tectonic setting of the granitoids,redefined the time of their deformation,and then further revealed amalgamation between Erguna-Xing’an and Songnen blocks,providing new materials for understanding the regional tectonic evolution of the Xing’anMongolian Orogenic Belt.Geochronological study shows that the early Late-Paleozoic magmatism in the Zalantun region happened during 405～325 Ma,and can be sub-divided into three periods：Stage I at the Early-Middle Devonian（405～380 Ma）,stage II at the Late Devonian-initial Early Carboniferous（365～350Ma）and stage III at the late Early Carboniferous（335～325 Ma）respectively.TheⅠstage andⅡstage granitoids belong to metaluminous to weakly peraluminous granitoids of shoshonite series and high-K calc-alkaline series,and are likely the I-type and high fractionated I-type granites formed in island-arc magmatism of subduction environment.And theⅢstage ones belong to metaluminous to weakly peraluminous granitoids of middle to high-K calc-alkaline series,and are likely high fractionated I-type and A-type granites formed in magmatism of post-collisional environment.The universal deformation of the granitoids,which was the product of lateral escape in a post-collisional environment,occurred in the end of Late Carboniferous to Early Permian（308～290Ma）.We conclude,therefore,that the occurrences of the early Late-Paleozoic granitic magmatism in the northern Great Xing’an Range was related to the collision and combination between Erguna-Xing’an and Songnen blocks,and the amalgamation at the Zalantun region might occur in the middle Early Carboniferous.

关 键 词：晚古生代早期 花岗质岩浆作用 锆石U-PB年代学 贺根山-黑河构造带 扎兰屯地区 

分 类 号：P588.11[天文地球—岩石学]