地球史中的构造活动论和发展阶段论

从全球构造的活动论和地壳演化的发展阶段论出发,简要地讨论如下科学问题:(1)岩石圈形成;(2)中国大陆形成和演化;(3)造山过程;(4)裂谷作用过程中的某些问题。研究认为:(1)岩石圈不是地球形成时就已存在了,亦不是一次形成的,而是对流地幔(或软流圈)多次(或多阶段)分异形成的;基于岩浆作用、沉积作用、变质作用和成矿作用等在地球发展历史中长远阶段性的变化的可能指示,提出岩石圈-软流圈系统的不可逆的长远期阶段性变化特征,并可划分为若干阶段。(2)基于对中国大陆形成与演化的大阶段的研究,认为显生宙以来,中国大陆是由塔里木、扬子、中朝、华夏、蒙古和印度等陆块经过多个阶段的造山运动,镶嵌组装在一起的一个复合大陆,其拼合组装的各个阶段的洋陆分布的格局是不一样的,这种构造重组一定伴随岩石圈-软流圈动力系统的重组和构造体制的重大转换。(3)燕山带燕山期可识别出5个造山幕,每个造山幕的岩浆作用、沉积建造、变质作用、变形方式均有差异,造山过程的幕式阶段性标志明显;并认为华北地区现今面积的大小,并不能代表侏罗纪-白垩纪时的状态,燕山带的面积在侏罗纪—白垩纪时期远比现在的小。(4)提出华北大陆裂谷作用在古近纪与新近纪—第四纪的伸展作用是两次幕式事件,而不是前人认为的一次事件的两个相,同时,认为古近纪的断陷性质盆地发育对应纯剪切机制,而新近纪—第四纪拗陷性质盆地发育对应于分布剪切机制。(5)认为燕山期和喜山期华北地区岩石圈减薄作用的机制、过程不同,分属两个不同的阶段的动力学系统,而不是一个连续的渐变过程。

Mobilism in tectonics and development by stages in Earth's history

This paper discusses the following scientific problems: (1)the formation of lithosphere, (2)the formation and evolution of China continent, (3)orogenic processes, and (4)rifting processes.We advance the following viewpoints:(1)The Lithosphere does not exist in the earliest stage of the Earth, and was later formed through convection and mantle-asthenosphere differentiation. We suggest that the formation of the lithosphere and asthenosphere is irreversible. The process of earth evolution is episodic in nature, and can be subdivided into several stages. (2)China is a composite land mass, which was formed through a series of orogenic events. Mainland China was formed by the amalgamation of microcontinents such as Tarim, Yangtze, North China, South China, Huaxia, Mongolia and India. This was the result of repeated rebuilding of the lithosphere and asthenosphere systems, accompanied with great changes in tectonic patterns. (3)Five orogenic stages may be recognized in the Yanshan orogenic belt, which are characterized by different types of magmatism, sedimentary successions, metamorphism and tectonism. (4)The tectonic extension of the North China craton in the Neogene-Quaternary and in the Paleocene are two separate events, and are not considered as two separate phases of one event. The graben fault basins of Paleogene age were formed by pure shearing mechanism, whereas the depression basins of Neogene-Quaternary age were formed by distribution shearing mechanism.(5)The mechanism of lithosphere thinning in the Yanshanian stage is different from that in the Himalayan stage in the North China craton. They represent two different dynamic systems, and are not one single continuous gradual processe.