论碰撞作用时间  

A discussion on the collision time

作　　者：万天丰[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2011年第3期48-56,共9页Earth Science Frontiers

摘　　要：以中国及欧洲大陆一些碰撞带所测得的同位素年龄为基础,讨论板块从俯冲到碰撞的过程,认为依次发生了如下事件:俯冲板块的运移速度减慢,洋壳在地表消失,开始碰撞,形成强构造变形与动力变质作用,发生一系列的岩浆活动,最后才隆升成山。这些事件都具有不同的同位素年龄。碰撞的初始作用时间,应该在所测年龄最新的洋壳消失以后,在强构造变形与动力变质作用发生之前。显然,如果只想使用任何一种地质事件的年龄来确定碰撞作用的初始作用时间都是很困难的。俯冲板块运移的初次减速很可能是由于从原来具有典型大洋岩石圈结构的板块俯冲,转变为洋陆过渡型板块俯冲所致。对于较小的、强度不大的板块来说,如中国大陆地块群,在板块碰撞与拼合之后,大陆板块仍可发生地壳转动或大幅度的位移。沿碰撞带主断层面贯入的"钉合岩体"可以是同构造期形成的,也可能是继续碰撞作用的产物。Based on the isotopic ages collected in some collision zones of China and Europe continents,the process from subduction to collision between plates is discussed;in this process the following events occurred in sequence： the decrease in the moving velocity of plates,the disappearance of the oceanic crust on the surface,the beginning of the collision,the formation of the strong deformation and dynamic metamorphism,the occurrence of a series of magmatism and,at last,the uplifting of mountains.Above events have extremely different isotopic ages.The initial collision age is younger than that of the oceanic crust disappearing on the surface,and older than that of the formation of strong deformation and dynamic metamorphism.Obviously,it is very difficult to determine the initial age of subduction by using the isotopic age of only one geological event.The first decrease in moving velocity of subduction plate may have occurred because of the transformation from the subduction lithosphere plate with oceanic type to that with oceanic-continental transition type.For the smaller plates with less strength,for example,the Chinese continental blocks,after the collision and amalgamation between two plates,the continental plate may subsequently rotate and migrate rather widely.The stitching pluton,intruded into main fault plane of collision zone,could be formed in syntectonic period and also in the period of subsequent collision,i.e.post collision.

关 键 词：板块俯冲-碰撞 板块位移 变形变质 岩浆活动 同位素年龄 

分 类 号：P54[天文地球—构造地质学]