晚中生代漠河盆地充填-剥露过程对鄂霍次克海关闭的响应

The closure of the Okhotsk Ocean which began in the Triassic is an important part of the late Mesozoic "East Asia Convergence". Clarifyits closing process and timeframe can help us determine the coupled relationship between the revolution history of the Okhotsk Ocean and the construction in East Asia, but also can help us to analyze the border differences here from a united multi-plate convergence context. The Mohe Basin locates on the south of the Mongol-Okhotsk suture belt. It is a foreland basin formed during the Mesozoic closure of the Okhotsk Ocean. In this basin, the late-Mesozoic sediments developed very well. These sediments were sourced from the Okhotsk suture zone and recorded the late-Mesozoic tectonic deformation of the Okhotsk suture zone. Therefore, the research of the late Mesozoic filling-denudation process of Mohe Basin provides an ideal operation scheme for determination of the detail process and specific closure time of the Okhotsk Ocean. Determine the continuous date and deposition rate (related with the source) of the sediment profile using the Paleomagnetic method; identify the process of the sudden deepen and migration of the water center combined with continuous strata date; disclose the time of uplifting and erosion rates of the source region using the detritus fission track samples (the stratigraphic ages were known);Using the temperature chronology, clarify the active stages,simulations of the basin exhumation process. Comprehensive analysis of the filling-denudation process of Mohe Basin, identifying the closing process of the Okhotsk Ocean in the late Mesozoic, has important scientific significance for the late Mesozoic "East Asia Convergence" research.

始于三叠纪的鄂霍次克海关闭,是晚中生代"东亚汇聚"的重要组成部分。明确其闭合过程和时限，不仅能够确定其演化历史与东亚陆内构造的耦合关系,而且还能有助于分析在统一多向板块汇聚背景下该边界的差异性。漠河盆地位于蒙古-鄂霍次克缝合带南侧,是鄂霍次克海关闭过程中形成的晚中生代前陆盆地。盆内源自鄂霍次克缝合带的沉积物非常发育,记录了缝合带在晚中生代的变形过程。因此研究漠河盆地的充填-剥露过程,是揭示晚中生代鄂霍次克海关闭过程和时限的理想方案。 用古地磁确定（与源区有关的）沉积剖面的连续年龄和沉积速率；结合连续地层年龄,用沉积学确定水体突然变深和沉积中心迁移的过程；具备地层年龄的碎屑颗粒裂变径迹样品可以确定源区挤压隆升的时间和剥蚀速率的变化；利用热年代学方法,确定断裂活动期次,模拟盆地剥露过程。综合分析其充填-剥露过程,确定晚中生代鄂霍次克海的关闭过程和时限,对于研究晚中生代东亚汇聚具有重要科学意义。

漠河盆地位于我国最北端，其与俄罗斯境内的乌舒蒙盆地相连为一个统一的盆地，其北为“蒙-鄂造山带”。研究漠河盆地的沉积体系和构造背景,将为“蒙-鄂带”造山过程甚至重建中生代东亚汇聚提供依据，且对盆地油气的进一步勘探有一定的指导意义。.系统的确定了漠河盆地上侏罗统与下白垩统地层岩石序列和空间展布，识别出断裂共75条，其中I级断裂11条，II级断裂11条，III级断裂53条。根据野外露头以及镜下观察，确定晚侏罗世为挤压环境，在侏罗纪与白垩纪交界存在一次逆冲推覆，早白垩存在一期强挤压，之后为伸展环境。.盆地从北向南水体逐渐变浅，整体展布规律从北向南为半深湖—滨浅湖—扇三角洲前缘—扇三角洲平原趋势。其中二十二站组和额木尔河组是盆地湖泊发育的主要时期。首次发现中侏罗世漠河盆地的物源除南部物源和北部物源以外，还存在盆地内部隆升产生的物源供给。盆地下充填整体表现出压性盆地的沉积特征。漠河盆地靠近“蒙古-鄂造山带”一侧细相带更加发育，由于鄂霍茨克海关闭的挤压作用，漠河-乌舒蒙盆地的沉积中心存在中心向南迁移的现象。.通过盆地内碎屑物质的常量元素和稀土元素的含量，揭示出漠河盆地源区构造背景为活动陆缘区及大陆岛弧区。.白垩纪以来研究区存在两期强隆升，1期在120ma，第二期在50ma，第一期强于第二期。其中120ma的隆升，是由鄂霍次克海关闭造成。.蒙古-鄂霍茨克海关闭始于三叠纪，结束于晚侏罗末到早白垩纪初期。在此过程中形成了漠河-乌舒蒙前陆盆地。三叠纪由于弧-陆碰撞形成弧后小洋盆乌舒蒙盆地发育三叠纪海相地层，三叠纪时期乌舒蒙盆地为弧后前陆盆地；随着挤压碰撞造山的进行（陆-陆碰撞），盆地向南进一步扩展，在晚侏罗纪中国境内的漠河盆地开始发育陆相地层，在晚侏罗纪漠河-乌舒蒙盆地为周缘前陆盆地。早白垩纪蒙古－鄂霍茨克洋的关闭，由造山后垮塌和古太平洋板块俯冲的远程效应，漠河盆地白垩纪以来整体处于伸展状态，为分割的断陷湖盆。