碰生型微地块的分类及其形成机制

Type and Genetic Mechanism of Collision-derived Micro-blocks

碰生型微地块是指受大陆碰撞造山作用触发的相对独立的微小板块或地块。本文通过具体实例从多角度对碰生型微地块进行了分类:按发生碰撞的两侧陆壳性质,可分为陆?陆、弧?陆和弧?弧碰生型微地块;按碰撞方式,可分为追尾式、侧向式、错车式和拥堵式碰生型微地块;根据微地块本身的物质组成,可分为碰生型微洋块和碰生型微陆块。总结了碰生型微地块的形成机制——远程碰撞触发模型:碰撞事件及其远程效应,触发了地幔内部热结构的非稳定性,使板块内部的应力失稳,在大陆内部形成岩石圈尺度的断裂,大块体被分裂为多个刚性块体,并发生差异性裂解、逃逸、挤出、旋转等,形成具有独立运动学特征的微陆块;在大洋内触发了洋中脊拓展式、跃迁式生长,形成独立微洋块。碰生型微地块类型划分为研究碰撞造山的非相邻地质体之间的盆?山效应奠定了基础,为研究“板内”变形机制提供了新依据、新思路。碰生型微洋块的形成记录了大陆碰撞事件的起始时间,是对基于大陆地质研究而确定的碰撞时间的重要补充。

The collision-derived micro-block is a relatively independent microplate or microblock formed in continental collision or orogeny.In this paper,the collision-derived micro-block is defined from various aspects with specific examples.It can be divided into continent-continent,continent-arc and arc-arc collision-derived micro-blocks according to the colliding continental crust on both sides of the collisional zones;it can also be divided into the rear-end collision,lateral collision,rubbing collision and congestion collision-derived micro-blocks regarding the collisional processes.It can also be divided into collision-derived oceanic micro-block and collision-derived continental micro-block according to the crustal type of the mico-block.Then,this paper summarizes the formation mechanism of the collision-derived micro-block—remote-collision triggering model:the collision event and its remote effect triggered the instability of the mantle thermal structure,resulting in the stress instabilities that destroy the original structure of the lithosphere and form lithosphere-scale fault inside the continent,and the large-scale block is rifted into several rigid micro-blocks.Subsequently,the independent micro-blocks are formed in the kinematics with differential rifting,escape and extrusion.Similarly,in the ocean,the collision event and its remote effect can trigger the jumping and propagation of the mid-ocean ridge,and forming the independent oceanic micro-block.The type division of the collision-derived micro-block is a key for studying complex collisional zones or orogenic belts,and providing theoretical support for refined tectonic research.The formation of the collision-derived micro-block records the starting time of the collision event,which can be an important supplement to the collision time determined by the study of the continental geology.