中国东部中新生代反转构造及其记录的大洋板块俯冲过程  

Mesozoic-Cenozoic inversion tectonics of East China and its implications for the subduction process of the oceanic plate

作　　者：索艳慧[1,2] 李三忠[1,2] 曹现志[1,2] 李玺瑶 刘鑫[1,2] 曹花花[1,2] 

机构地区：[1]海底科学与探测技术教育部重点实验室 [2]中国海洋大学海洋地球科学学院,山东青岛266100 [2]青岛海洋科学与技术国家实验室海洋地质功能实验室,山东青岛266237

出　　处：《地学前缘》2017年第4期249-267,共19页Earth Science Frontiers

基　　金：国家自然科学基金项目(41502185,41325009,U1606401);山东省泰山学者特聘教授项目;鳌山卓越科学家计划项目(2015ASTP-0S10);国家实验室项目(2016ASKJ 3);国家重点研发计划项目(2016YFC0601002)

摘　　要：中新生代期间,中国东部可以划分西部沉降带(包括东北、华北和中下扬子盆地群)和东部沉降带(包括东海和南海盆地群)。各盆地内部反转构造表现为东强西弱、自东向西迁移的规律,反映了构造反转的动力来自东部,证实了反转构造是古太平洋或太平洋板块的俯冲效应。但反转构造总体又具有自西部沉降带向东部沉降带迁移的特征:西部沉降带以中生代末期的挤压反转为主,而东部沉降带以渐新世末和中新世末的新生代反转最为典型。可见,虽然在同一俯冲板块作用下,仰冲板块的反转时间和迁移规律却存在差异性,这可能与反转构造所隶属的仰冲板内背景或俯冲板块自身行为在不同地区存在时空差异有关。为确定哪一种反转机制,本文搜集了古地磁条带和最新的板块重建方案、太平洋海山K-Ar年龄等数据,初步厘定出中新生代期间太平洋板块运动学行为;也对中新生代期间中国东部的东北、华北和华南的地质特征等开展对比研究。本文认为,伊泽奈崎板块早期为平板式俯冲,160Ma左右板块拆沉并折返及岩石圈减薄,是西部沉降带的成盆机制;80 Ma左右伊泽奈崎板块向西的运动速度达到极值,对中国东部造成统一向西的挤压应力,是西部沉降带中生代的反转机制;大洋板块上发育的NW向破碎带的俯冲,可能加剧了这一期反转强度。60Ma左右伊泽奈崎板块俯冲潜没于欧亚大陆之下及太平洋板块俯冲启动并后撤,这是东部沉降带的成盆机制;中新世中晚期,菲律宾海板块向欧亚板块的俯冲挤压导致了中国东部大陆左旋压扭的应力场,这是东部沉降带新生代构造的反转机制。During the Mesozoic-Cenozoic period,the tectonic units in East China can be divided into the West Depression Belt（including Northeast China,North China,Middle and Lower Yangtze basin group）and the East Depression Belt（including East China Sea and South China Sea basin group）.The inversion intensity decreases from east to west for each basin,implying ageodynamic mechanism from the east and verifying the fact that the inversion structures were caused by the subduction of the paleo-Pacific Plate or Pacific Plate.Mesozoic inversion tectonics developed in the West Depression Belt,while Cenozoic inversion tectonics developed in the East Depression Belt,implying the subduction retreat of the paleo-Pacific Plate or Pacific Plate.Two alternative mechanisms could explain the complex inversion processes in East China：the differences of tectonic settings of each depression belt or the spatial variations of the subduction plates.To test which explanation is more reliable,we use paleo-magnetic data and K-Ar ages of the Pacific seamounts to analyze the kinematic processes of the paleo-Pacific and Pacific plates,and made a comparative study of the geological features for each depression belt.We concluded that the flat-slab Izanagi subduction in East China before ca.160 Ma formed the 600-km-wide intracontinental magmatic belt in Northeast China and the 1300-km-wide intracontinental magmatic belt in South China.Delamination of subduction slab at ca.160 Ma formed the West Depression Belt;the Cretaceous climax of compression of the Izanagi Plate at ca.80 Ma caused the regional inversion structures in the West Depression Belt.At ca.60 Ma,the Pacific Plate began to subduct under the Eurasian Plate and retreated eastward,resulting in the East Depression Belt;the subduction of the Philippine Sea Plate under the Eurasian Plate at the late Miocene produced the structural inversion in the East Depression Belt.

关 键 词：中国东部 反转构造 平板俯冲 拆沉 俯冲后撤 

分 类 号：P542[天文地球—构造地质学]