学术论文

      地球的层圈结构与穿越层圈构造

      The Spherical Structure of the Earth and Across-sphere Tectonics

      摘要:
      从1906年发现地核到20世纪60年代,地球物理学、地质学和矿物物理学的研究揭示了地球具有物理化学性质截然不同的层圈结构,并根据全球地震波速度和密度的变化建立了初始参考地球模型.1967年提出的板块构造理论假定刚性的岩石圈板块在塑性的软流圈之上发生运动,在洋中脊不断形成的洋壳逐渐在海沟俯冲,由于板块是刚性的,变形将主要集中在板块边界.板块构造理论成功地解释了大洋岩石圈的形成和消亡、火山和地震活动带的分布以及全球构造格局,给地球科学带来了一场革命.但是,经典的板块构造理论尚未解决板块运动的起源和驱动力、大陆岩石圈的弥散性变形、大陆深俯冲等问题,因此大陆动力学成为对板块构造理论的重要补充.近年来的研究表明:在板块汇聚边界,大洋岩石圈可以俯冲至地幔过渡带、下地幔,乃至核幔边界;而大陆岩石圈可以俯冲至150~ 300 km深度,然后相对低密度的陆壳物质快速折返形成含柯石英和微粒金刚石的超高压变质带.地幔柱活动是是俯冲板块再循环的产物,不仅可以形成大火成岩省和洋岛玄武岩,还可以把俯冲到地幔过渡带的物质带回浅部,导致蛇绿岩中保留金刚石和深地幔矿物.因此,俯冲带和地幔柱不仅提供了穿越层圈的物质和能量交换的通道,也驱动了对地球宜居性至关重要的水循环和碳循环,是研究地球物质组成和动力学演化的重要窗口.
      Abstract:
      From the discovery of the Earth's core in 1906 to 1960's,studies of geophysics,geology and mineral physics revealed a spherical structure of the Earth composed of layers with different physical and chemical properties.The Preliminary Reference Earth Model has been established according to global changes of seismic velocities and density with depth.The plate tectonics theory proposed in 1967 brought a revolution in Earth Sciences.Plate tectonics proposed that the outer shell of the Earth is a rigid lithosphere,which moves above a ductile asthenosphere.The oceanic crust is continuously formed at mid-ocean ridges and consequently similar amount of the old oceanic crust subducted at trenches.Because of the rigidity of plates,deformation is mainly concentrated in plate boundaries.Plate tectonics successfully interprets the birth and subduction of the oceanic lithosphere,distribution of volcanos and earthquakes,and global tectonic regime.However,it still cannot answer some key questions such as when and how plate tectonics initiated,how diffusive deformation of the continental lithosphere formed,deep subduction of the continental lithosphere etc.Hence continental dynamics became an important complementary to plate tectonics.Recent studies indicate that at convergent plate margins,the oceanic lithosphere may be subducted to the mantle transition zone,the lower mantle and even the core—mantle boundary;whereas the continental lithosphere may be subducted to depths of 150 ~ 300 km and then the low-density continental materials exhume rapidly and form coesite-and diamond-bearing ultrahigh-pressure metamorphic terranes.Mantle plumes are related to the recycling of subducted oceanic slabs.They not only produces large igneous provinces and oceanic island basalts,but also carry subducted materials from the mantle transition zone to the shallow depths,as evidenced by diamond and deep mantle minerals in ophiolites.Across-sphere tectonics,such as subduction zones and mantle plumes,not only provided important pathways for the material cycles among different layers,but also triggered the Earth's deep water and carbon cycles that are essential for a habitable planet.Therefore,knowledge about subduction zones and mantle plumes is critical for our understanding of composition and dynamic evolution of the Earth.
      作者: 许志琴 [1] 王勤 [1] 孙卫东 [2] 李忠海 [3]
      Author: XU Zhiqin [1] WANG Qin [1] SUN Weidong [2] LI Zhonghai [3]
      作者单位: 内生金属矿床成矿机制研究国家重点实验室,南京大学地球科学与工程学院,南京,210046 中国科学院海洋研究所深海研究中心,山东青岛,266071;青岛海洋科学与技术国家实验室,山东青岛,266237 中国科学院大学地球科学学院计算地球动力学实验室,北京,100049
      刊 名: 地质论评 ISTICPKU
      Journal: Geological Review
      年,卷(期): 2018, 64(2)
      在线出版日期: 2018年7月2日
      基金项目: 国家自然科学基金资助项目,中国地质调查项目,南京大学人才基金的成果.This study was supported by the National Natural Science Foundation of China,the Geological Survey of China (No.1212010818094).We appreciate academician Jin Zhenmin,Yang Wencai and Yang Jjingsui for discussion with us.We thank Zheng Yilong,Zhang Miao and Ma Zeliang for their assistances in the text