微板块与深部地幔LLSVP的遥相关作用  

Telecommunication interactions between microplates and basal mantle LLSVPs

作　　者：曹现志[1,2] 李三忠 索艳慧[1,2] 戴黎明 杨安[3] 王鹏程 刘金平[1,2] CAO XianZhi;LI SanZhong;SUO YanHui;DAI LiMing;YANG An;WANG PengCheng;LIU JinPing(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,and College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Laoshan Laboratory,Qingdao 266237,China;Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China)

机构地区：[1]深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,青岛266100 [2]崂山实验室海洋矿产资源评价与探测技术功能实验室,青岛266237 [3]中国科学院海洋研究所,海洋地质与环境重点实验室,青岛266071

出　　处：《岩石学报》2023年第3期659-669,共11页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42121005、91958214);青岛海洋科学与技术国家实验室山东省专项经费(2022QNLM05032);山东省自然科学基金项目(ZR2021YQ25);科技部重点研发计划项目(2022YFF0800401)联合资助。

摘　　要：基于海洋地质地球物理观测建立的板块构造理论意味着板块和浅部地幔共同演化,然而地幔底部尤其是大型横波低速异常区(LLSVP)与板块(尤其微板块)运动和演化之间是否存在关联仍有争议。一些研究认为LLSVP长期保持稳定,而另一些模型则认为它与各级板块存在相互作用。为此,本文通过总结前人成果,并基于近期发表的板块重建和地幔对流模型进行进一步分析,探讨微板块运动和LLSVP的演化关系。模拟结果表明,微板块与大板块类似,俯冲后通常会下沉至核幔边界。微幔块会推动地幔底部热的物质聚集并形成大的热化学结构。该热化学结构与层析成像揭示的LLSVP基本吻合。下地幔径向流速场和温度场的二阶结构与地表速度场散度的二阶结构随时间的移动轨迹相似,表明深浅部圈层的耦合演化,但是下地幔结构演化一般会滞后于浅表。在微幔块推挤之下,地幔柱优先沿着地幔底部热化学结构的边缘形成,且有时会被推至热化学结构的内部。地幔柱上升至浅部后,能够导致岩石圈弱化甚至裂解或板块边界跃迁,形成微板块。因此,地幔底部LLSVP不是稳定或静止的,而是与微板块动态协同演化,并通过地幔柱与浅表板块边界发生遥相关,从而控制微板块生成场所。Plate tectonic theory, underpinned by marine geological and geophysical observations, indicates co-evolution between plates and shallow mantle. However, whether the basal mantle, especially the Large Low Shear Velocity Provinces(LLSVPs), is related to the motion and evolution of plates(especially microplates) is still controversial. Some studies proposed that LLSVPs remain stable forever, while other models indicate that they interact with both large plates and microplates. This paper discusses the relationship between Earth’s surface and the LLSVPs by summarizing previous works and in-depth analysis on our recently published microplate reconstruction and mantle convection models. The model results show that similar to large plates, after microplates are subducted, the mantle microplates generally sink to the basal mantle, sweeping hot materials into large thermochemical structures. The modelled thermochemical structures are consistent with the LLSVPs revealed by tomography. The motion path of degree-2 structure of the radial velocity and temperature fields in the lower mantle is similar to the degree-2 structure of the surface divergence over time, indicating the coupled evolution of deep Earth mantle and shallow Earth surface. However, the evolution of the lower mantle structure may lag behind the surface. Due to the push from mantle microplates, mantle plumes preferentially form along the edge of the thermochemical structures, and sometimes they are further pushed to the interior of the thermochemical structures. When plumes rise to shallow Earth, they can lead to the weakening or even breakup of the lithosphere above or jump of plate boundaries, forming microplates. Therefore, the LLSVPs are not stable, but evolve dynamically with microplates at the Earth’s surface, and control the development sites of microplates through telecommunication interactions of plumes with plate boundaries at the Earth’s surface.

关 键 词：微板块构造 地幔对流 大型横波低速异常区 深浅耦合 地球动力学 

分 类 号：P541[天文地球—构造地质学]