从洋-陆俯冲到陆-陆碰撞:回眸与展望

From accretion to collision:situation and outlook

大陆造山带的经典含义是指由于大陆地壳岩石在板块俯冲-碰撞的巨大挤压应力下,遭受强烈变形、变质和熔融作用,地壳发生大规模缩短、加厚和隆升而形成的地带。分布在大陆边缘和内部的造山带,经历从洋壳扩张、洋-陆俯冲到陆-陆碰撞的造山过程,形成"俯冲增生型"、"陆陆碰撞型"和远离板块边界的"陆内型"造山带。造山带类型的分析是识别地球上造山带机制的钥匙。本文在阐述经典造山带分类的基础上,根据造山带的几何学、热历史、构造样式等特征,讨论了弧形造山带、特殊几何学造山带和走滑造山带的结构、运动学和动力学,以及从洋-陆俯冲到陆-陆碰撞造山在时空上的转化和演化。在回顾造山带研究的基础上,突出在板块汇聚边界的大洋和大陆俯冲带研究的重大进展,提出俯冲带和地幔柱提供了穿越地球层圈物质和能量交换的通道,它们的结合研究是探索全球单层壳-幔大循环假说与板块驱动力的新方向,是统领造山带研究的大思路。对于大陆动力学研究的一些前瞻性问题的思考,强调了造山过程的热扩散模式和变形-变质-深熔-成矿作用的自组织行为,以及地壳熔融在造山中的重要性;强调了流变学在大陆造山带形成和演化中的基础地位,并认为这是造山带研究中亟待解决的问题。作者认为板块水平运动是致使地壳挤压缩短和加厚、形成造山带的主要驱动力;而在板块离散边界(包括大洋中脊)垂直上升流所形成"地貌"上的山链,被称为"伸展造山带",不应属于经典"造山带"的范畴。

The classic definition of an"orogen"is a belt of notably shortened,thickened and uplifted continental crust,which has been strongly deformed,metamorphosed and even partially melted,under the massive stress caused by subduction or collision.It is important to understand different types of orogenic mechanisms."accretionary orogens","collisional orogens"and"intracratonic orogens"are formed inside or on the margins of continents,throughout the process of oceanic curst spreading,oceanic-continental subduction and continental collision.In this paper,we further discuss the kinematics and dynamics of curved orogens,irregular-shaped orogens and strike-slip-fault orogens,based on their geometries,thermal histories,tectonic styles and deep-subduction modes.The spatial and temporal transitions between accretionary and collisional orogens are also discussed.In the discussion part,we emphasize the recent major advances of in subduction zone research.The subduction zone and mantle plume work as conveyors of materials and energy throughout the Earth’s spheres.Their investigations should provide crucial information about the Earth’s crust-mantle convention,as well as the driving force of the plate movement.Therefore,the study of subduction zone should also be the focus in the research of orogens.In the outlook part,we address several key questions to be solved.The thermal evolution in orogeny is described,as well as its self-organizing mechanism through deformation,metamorphism,anatexis and mineralization processes.The importance of crust melting in orogeny is accentuated.The understanding of the rheological processes in the orogeny is fundamental in the study of continental orogens,but has not been adequately developed yet.The authors argue that the horizontal movement of tectonic plates is the major driving force of orogeny.On the other hand,geomorphic mountain building caused by vertical upwelling along divergent plate boundaries(including mid-ocean ridges),are not"orogens"by classic definition.This applies to the those"extensional orogens"and"rifting orogens",as defined by some authors.