摘要
大陆下地壳是连接岩石圈地幔和上地壳的“纽带”,是地壳与地幔交换最活跃的部位。上地幔与下地壳的部分熔融及下地壳一些岩石的拆沉还可直接导致壳-幔物质的交换、循环与重组。换言之,下地壳是壳-幔作用的一个极其重要的场所,底垫、拆沉、深熔、高级变质和其他作用都在下地壳中发生和实现。然而,下地壳是以往研究地球深部和浅部关系时被“跳”过去的部位,没有得到足够的重视。克拉通化定义为大陆原来混沌的原地壳分异并形成稳定的上地壳和下地壳,并由此构建了稳定的壳-幔结构,这种空前的稳定关系从形成起一直维持到现在,是大陆演化、洋-陆与壳-幔相互作用的基础。在板块边界的造山过程中,如洋-陆的俯冲碰撞特别是陆-陆碰撞,可以形成不同大陆地块的陆壳叠置、加厚、垮塌、拆沉、底垫和重新稳定,在造山带根部形成新的下地壳,即造山带型下地壳。本文重点讨论了克拉通型下地壳演化过程,强调了其动力学意义及其在大陆动力学研究中的重要地位,建议在深地研究和学科布局中给与充分重视。
The lower crust,linking the lithospheric mantle and the upper crust,is the most active place of energy exchange between the crust and the mantle;and partial melting of the lower crust and upper mantle,and delamination of the lower crust can directly lead to crust/mantle material exchange,re-cycling,recombination.In other words,the lower crust is one of the most important site for mantle-crust interactions where magma underplating,anatexis,delamination,high-grade metamorphism,and other processes take place.However,the lower crust has been largely overlooked by previous studies of the deep Earth.In this paper,the lower crustal profile of the North China Craton is described in detail.On this basis,the craton-type lower crust processes are discussed,and their dynamic significance and important position in the study of continental dynamics are emphasized.Cratonization is the transition of the formerly chaotic crust of the continent to stable upper and lower crust,and thus establishing a stable lithosphere.This unprecedented stable relationship between the crust and the mantle has been maintained from the beginning to the present,and is the basis for continental evolution,ocean-continent interaction,and crust-mantle interaction.The cratonic crust is not static after formation,and the continental boundaries can change during ocean-continental subduction-collisions.Especially during continent-continent collisions,the continental crust that can form different continental blocks is superimposed,thickened,collapsed,disassembled,underpinned and re-stabilized.At the root of the continental orogenic belt,a new lower crust is formed to become the lower crust of the orogenic belt type.We,therefore,suggest in this paper that the craton-type lower crust processes should receive full attention in the study of the deep Earth as well as in the designing of geoscience curricula.
作者
张艳斌
翟明国
周艳艳
周李岗
ZHANG Yanbin;ZHAI Mingguo;ZHOU Yanyan;ZHOU Ligang(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2024年第1期28-45,共18页
Earth Science Frontiers
基金
国家自然科学基金项目(42220104008)。
关键词
大陆下地壳
地质过程
壳幔作用
克拉通
造山带
地球动力学
continental lower crust
geological process
interaction between crust and mantle
craton
orogeny
geodynamics