“岩浆引擎”与板块运动驱动力  

The Magma Engine and the driving force of plate tectonics

作　　者：孙卫东[1,2,3] Weidong Sun(Center of Deep Sea Research,Ocean Mega-Science Center,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Laboratory for Marine Mineral Resources,Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266237,China;School of Marine Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院海洋研究所深海研究中心中国科学院海洋大科学中心 [2]青岛海洋科学与技术试点国家实验室海洋矿产资源评价与探测技术功能实验室 [3]中国科学院大学海洋学院

出　　处：《科学通报》2019年第28期2988-3006,共19页Chinese Science Bulletin

基　　金：中国科学院战略性B类先导科技专项(XDB18020000);科技部重点研发计划“深地资源勘查开采”重点专项(2016YFC0600408)资助

摘　　要：从能量的角度看,地球内部的热是驱动板块运动的主要能量_热能要转化为动能需要集中有序释放.在地球上,热能最主要的集中有序释放发生在洋中脊岩浆作用过程中.根据“岩浆引擎”模型,在洋中脊不断形成新洋壳,新洋壳轻而薄,老洋売厚而重,致使整个板片斜置于软流圈上,产生下滑力,导致洋中脊不断扩张,形成新洋壳并推动俯冲带老洋壳的消亡,从而驱动板块运动.地幔柱岩浆活动是“岩浆引擎”的另一种表现形式.大的地幔柱头会引起上覆岩石圈受热,与大量上涌的岩浆共同作用,在其中心部位产生千米级的隆升,从而导致地壳局部大幅度的倾斜,产生向外的下滑力.当下滑力足够大时,岩石圈拉张破裂,向两边推挤扩张,同时远端洋壳在薄弱地带挤压破裂,产生板块俯冲.这是板块运动最初起始和“岩浆引擎”的点火器.在板块构造体制下,板块俯冲起始有两种主要形式,自发俯冲和诱导俯冲.自发俯冲起始往往发生在老洋盆,通常产生双向俯冲;诱导俯冲起始则往往发生于年轻洋盆,通常产生单向俯冲.新特提斯洋的多次单向俯冲闭合是诱导俯冲起始所致.“岩浆引擎”主要作用于与洋中脊和地幔柱相关的板块.其他板块构造运动的能量主要来自于板块相互作用.The true driving force behind drifts in plate tectonics is still a topic open for discussion.Currently,slab pull is taken as the dominant driving force.From the energy perspective,heat from the Earth's interior is the main source of power maintaining plate tectonics.The organized release of heat is the key to transforming static energy into kinetic energy.Here we propose a Magma Engine model.According to this model,heat is changed to potential energy through magmatism,and this consequently drives movements in plate tectonics through gravity.New oceanic crust is formed continuously at the mid-Ocean ridges,and then cools down gradually.The newly formed oceanic crust is lighter and thinner than the older ones,resulting in tilted plates sitting on the asthenosphere mantle.Given that the mantle has a high viscosity of 10^19-10^21 in the asthenosphere,and even higher values further down,the oceanic plate would lie on a big slope,with a height difference of around 80 kilometers.The highest plate sliding forces reach 1.4×10^14 N/m,which is an order of magnitude larger than the estimated value of slab pull.It is therefore the primary driving force of plate tectonics.Mantle plume is another type of Magma Engine.Large plume heads may elevate the overlying continental crust in kilometer scales,due to high temperatures and the bouncy of large amounts of plume magma.Such uplifting may lead to the overlying plate sliding away from the center of the plume.This may initiate plate subduction along weaker belts in case the plume is big enough and the overlying plate is strong enough.This is likely the main mechanism that initiated plate tectonics in the early history of the Earth.Under the plate tectonic system,the plume head plays a major role in the opening of new ocean basins,acting as an“igniter”of mid-ocean Magma Engines.There are two types of subduction initiations,spontaneous and induced(or forced).Spontaneous subduction initiation usually occurs in old ocean basins,forming double-track subductions on either side of the

关 键 词：板块构造 板块运动驱动力 岩浆引擎 板块滑移力 俯冲起始 

分 类 号：P58[天文地球—岩石学]