俯冲带形成机制的可检验假说和检验方案  

The geologically testable hypothesis on subduction initiation and actions

作　　者：牛耀龄[1,2,3] 沈芳宇 陈艳虹 龚红梅[2,4] Yaoling NIU;SHEN Fangyu;CHEN Yanhong;GONG Hongmei(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266061,China;Department of Earth Sciences,Durham University,Durham DH13LE,UK;Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [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266061 [3]Department of Earth Sciences,Durham University,Durham DHI 3LE,UK [4]中国科学院海洋研究所,山东青岛266071

出　　处：《地学前缘》2018年第6期51-66,共16页Earth Science Frontiers

基　　金：国家自然科学基金项目(41630968,41130314);国家基金委-山东省联合基金项目(U1606401);青岛海洋科学与技术国家实验室鳌山科技创新计划项目(2015ASKJ03);111计划项目(B14-048)

摘　　要：五十年前板块构造理论的诞生是地球科学领域的一场革命,它为理解地球如何运作构建了基本框架。过去五十年对该理论的进一步研究告诉我们地质过程最终都是地球热损失的结果。例如,大洋岩石圈板块在洋中脊形成,其运动和增生以及最终通过俯冲带进入地幔导致地幔冷却降温,从而导致大规模的地幔对流。亦即,板块构造的直接驱动力是俯冲大洋岩石圈板块的下沉力。因此,没有俯冲带就没有板块构造,但是俯冲带如何开始仍然有争议。对俯冲起始的研究从未中断,有数值模拟也有地质推断。2014年在西太平洋用三个IODP航次(350、351和352)来检验“自发”和“诱发”俯冲开始的想法。所有这些努力都值得肯定,但这些是无法检验的想法。无法检验意味着没有结果。本文介绍至今唯一可用地质学方法检验的假说,亦即“岩石圈内横向物质组成差异导致的浮力差是俯冲带形成的起因”。这种浮力差位于海底高原的边部和被动大陆边缘,因此这些部位是未来俯冲带起始的必然轨迹。在远离这些部位的正常洋盆内因缺乏浮力差而俯冲带不可能起始。换句话说,“所有岛弧一定有大陆(或海底高原)基底”,这可以通过采集和研究岛弧基底岩石来验证。The advent of plate tectonics theory 50 years ago has revolutionized Earth Science thinking and provided a solid framework for understanding how the Earth works.This theory explains in simple clarity that all the geological processes are ultimately consequences of Earth’s cooling.This is well manifested by the origin of oceanic plates at ocean ridges,the movement and thickening of these plates,and their ultimate consumption back into the Earth’s deep interior through subduction zones,which provides an efficient mechanism to cool the Earth’s mantle,leading to large-scale mantle convection.That is,the immediate driving force for plate tectonics is the sinking of the cold and dense oceanic lithosphere,under gravity,into the deep mantle through subduction zones.Hence,there would be no plate tectonics if there were no subduction zones,but exactly how a subduction zone begins remains speculative.Studies on subduction initiation have been many and continue to this day by means of numerical simulation and geological inferences,culminating with three IODP expeditions (350,351 and 352 in 2014) in the western Pacific to test the ideas of spontaneous and induced subduction initiation.All these efforts are welcome,but the ideas are not testable hypothesis.In this paper,we explain the only hypothesis that is geologically testable on subduction initiation,i.e.,subduction initiation is a consequence of lateral compositional buoyancy contrast within the lithosphere.Such large buoyancy contrast is located at edges of oceanic plateaus in ocean basins and at passive continental margins globally.Because back-arc basins result from seafloor subduction,all the island arcs must have continental (or oceanic plateau) basement.Hence,this hypothesis can be effectively tested by sampling and studying island arc basement rocks that are exposed on landward trench slopes as the result of serpentinite diapirism.

关 键 词：完善板块构造理论 俯冲带的成因 被动大陆边缘 海底高原边缘 岛弧基底岩石组成 

分 类 号：P541[天文地球—构造地质学]