新特提斯单向俯冲的动力学机制  

Geodynamics of the one-way subduction of the Neo-Tethys Ocean

作　　者：朱日祥[1] 赵盼 万博[1] 孙卫东[2,3] Rixiang Zhu;Pan Zhao;Bo Wan;Weidong Sun(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Center of Deep Sea Research,Ocean Mega-Science Center,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;School of Marine Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [2]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研究中心,青岛266071 [3]中国科学院大学海洋学院,北京100049

出　　处：《科学通报》2023年第13期1699-1708,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(92155203)资助。

摘　　要：新特提斯洋向北单向俯冲的机制涉及两个核心问题,分别是南侧冈瓦纳被动大陆的不断裂解和拼贴到欧亚大陆南缘陆块诱发的俯冲起始.本文统计了大火成岩省的分布规律,发现200~80 Ma期间,与地幔柱相关的大火成岩省主要分布于南半球,暗示该时期南半球地幔温度高于北半球地幔温度.在南北半球地幔温差和地幔柱/大火成岩省作用下,引起上覆岩石圈抬升、破裂,结合新特提斯洋的北向俯冲,共同诱发冈瓦纳大陆的多期裂解.由于南北半球地幔温差会造成地幔柱头岩浆向北扩散并与新特提斯洋中脊发生相互作用,在特殊情况下,会引发原来大洋中脊的堵塞和跃迁,形成新的洋中脊,促进了陆块不断向北漂移.在古特提斯洋闭合后洋壳持续俯冲引发的应力作用下,欧亚大陆南缘具有高含水特性的洋陆过渡带率先破裂并产生向北的俯冲起始.驱动新特提斯大洋岩石圈持续向北俯冲的动力,除俯冲板片的拖曳力/重力外,还应该包含南半球高地幔温度和洋中脊产生的向北推力.The one-way northward subduction of the Neo-Tethys Ocean involves two essential processes:Persistent rift of blocks from northern margin of Gondwanaland and subduction initiation after collision of drifted blocks of the Eurasian continent.Therefore,uncovering the mechanism of the two processes is a key target to decipher the geodynamics of the one-way subduction of the Neo-Tethys Ocean.From a compilation of large igneous provinces(LIPs),we find that plume related Mesozoic LIPs are mainly distributed in the southern hemisphere,indicating higher southern hemisphere mantle temperature than that of the northern hemisphere.The high mantle temperature can be ascribed to the existence of the Tuzo large low-shear-velocity province(LLSVP)beneath the Gondwanaland.The Tuzo LLSVP resulted in upwelling of mantle plumes of different ages,leading to uplift and rupture of overlying lithosphere that induced the continuous rifting of blocks from the northern margin of Gondwanaland.With the northward subduction of the oceanic slab,the rifted blocks drifted northward away from Gondwanaland.Hemispheric mantle temperature difference also induced northward transfer of plume head magma to mid-ocean ridges.Under exceptional circumstances,the interaction between plume head magma and mid-ocean ridges can block the ridges and lead to ridge jumps,forming new mid-ocean ridges,which can promote the expansion of the Neo-Tethys Ocean and northward drift of rifted blocks.For subduction initiation along the new southern margin of the Eurasian continent,after closure of the Paleo-Tethys Ocean,the drag force from the still on-going subduction of subducted Paleo-Tethys oceanic slab and push force from Neo-Tethys mid-ocean ridge led to stress accumulation that induced rupture of the Neo-Tethys slab in the ocean-continent transition zone along the northern margin of the Neo-Tethys Ocean,which is the weakest region for slab rupture.Meanwhile,the southern margin of the Eurasian continent experienced multistage orogenic events during the Phanerozoic,where

关 键 词：新特提斯洋 单向俯冲 俯冲起始 南北半球地幔温差 欧亚大陆南缘富水岩石圈 

分 类 号：P542[天文地球—构造地质学]