长春-延吉缝合带:性质与意义  

The Changchun-Yanji Suture Zone: Nature and tectonic implications

作　　者：周建波 曹嘉麟[1,2] 韩伟 李功宇[2] ZHOU JianBo;CAO JiaLin;HAN Wei;LI GongYu(Key Laboratory for Evolution of Past Life and Environment in Northeast Asia,Ministry of Education,Jilin University,Changchun 130026,China;College of Earth Sciences,Jilin University,Changchun 130061,China)

机构地区：[1]吉林大学东北亚生物演化与环境教育部重点实验室,长春130026 [2]吉林大学地球科学学院,长春130061

出　　处：《岩石学报》2020年第3期635-643,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41730210);科技部深地专项(2017YFC0601304)联合资助.

摘　　要：长春-延吉缝合带(或长春-延吉增生杂岩带),是由佳木斯-兴凯地块与华北板块之间俯冲拼贴形成的增生杂岩带。该缝合带自西向东分为三个部分,具体包括西段吉林-红旗岭、中段桦甸-两江和东段华集岭-开山屯组成。长春-延吉增生杂岩带以延边地区发育的开山屯混杂岩为代表,自西向东包括石头口门-烟筒山高压红帘石片岩,以及原定为“呼兰群”、“色洛河群”、“青龙村群”等一系列沿着缝合带分布的构造杂岩等,它们均发育“基质包裹外来岩块(block-in-matrix)”的混杂岩结构,并在吉林东部石头口门、烟筒山和延边开山屯等地区发现高压矿物组合,因此,这些杂岩应代表了佳木斯-兴凯地块向华北板块俯冲-拼贴过程中形成的增生杂岩。长春-延吉增生杂岩原岩年龄大致为晚古生代-早中生代(最小峰期240~250Ma),并被时代为~220Ma的晚三叠世大酱缸组磨拉石层序不整合覆盖,这一直接证据与近期发表的年代学证据一致,共同证明了长春-延吉缝合带的就位时代为中三叠世(220~240Ma),而不是前人认为的晚古生代或更早。区域构造分析显示,长春-延吉增生杂岩带不是天山-北山-西拉木伦河-长春断裂带的东延部分,而是佳木斯-兴凯地块西南缘分布的吉林-黑龙江高压变质带的南部组成部分,形成于三叠纪-早侏罗世太平洋板块西向俯冲过程中,佳木斯-兴凯地块自东向西的“剪刀式”闭合过程。因此,长春-延吉增生杂岩带记录了古亚洲构造域的结束和太平洋俯冲开始的关键时期,为两大构造域叠加与转换的关键性地质证据。Changchun-Yanji Suture Zone(CYSZ),or the Changchun-Yanji Accretionary Complex Belt(CYACB),is a subductionaccretion complex and formed at the collisional belt between the Jiamusi-Khanka Block(JKB)and the North China Craton(NCC).The CYSZ consists of three segments,and they are the Panshi-Hongqiling segment in the west,the Huadian-Liangjiang segment in the middle,and the Huajiling-Kaishantun segment in the east The typical subduction-related rock assemblages of the CYSZ are the Kaishantun melange in the Yanbian area,the Yantongshan high-pressure metamorphic rocks in the Panshi area,and the accretionary complex of the Hulan,Seluohe and the Qinglongcun‘groups’along the CYSZ.Those rocks show mélange structure as‘block-inmatrix’,and the high-pressure metamorphic mineral assemblages,implying that those rocks are not normal strata but the accretion-subduction complex due to the JKB subduction beneath the NCC.The protolith ages of the Changchun-Yanji accretionary complex are at Late Paleozoic to Early Mesozoic(250~240Ma),and was unconformity covered by the Dajianggang molasses of Late Triassic(~220Ma).Our recently new data together with the evidence from other studies,suggest that final close timing of the Changchun-Yanji suture should be at the Middle Triassic(240~220Ma),and not Late Paleozoic or more early as previously considered According the regional tectonic analyses,CYSZ are not eastern segments of the Tianshan-Beishan-Xra-Moron-Changchun Suture,but the southern segments of the Jilin-Heilongjiang High-pressure Metamorphic Belt(Ji-Hei HP Belt).The Ji-Hei HP Belt did not result from subduction between the Siberia and North China cratons within the Paleo-Asian Ocean,but instead was due to subduction of the Pacific Ocean from the east The Triassic is thus the time when major north-south subduction in the Central Asian Orogenic Belt(CAOB)had ceased and westward-directed Pacific Ocean plate subduction commenced in NE China.

关 键 词：中生代增生杂岩 古太平洋板块 中亚造山带 长春-延吉缝合带 欧亚大陆东缘 

分 类 号：P542.4[天文地球—构造地质学]