天体化学:地球起源与演化的几个关键问题

以近几年天体化学研究取得的一些重要成果，论述了对于认识地球的起源和演化进程的重要意义。地球主要由一套具有独立化学成分组成的硅酸盐质星子群随机碰撞吸积而成。地球的星子堆积形成方式和初始化学成分的不均一性制约着地球后期的非均一、非均变演化过程。以１８００Ｍａ为转折点，地球的演化具明显的两阶段演化特征：早期以初生壳体———星子源地体的形成和发展为特点，后期以岩石圈板块运动为特点。地球演化史中的地外撞击事件，是太阳系形成机制———碰撞吸积作用的继续，是地质历史生物、沉积、岩浆、构造等演化的重要营力之一。

RELATIONSHIP BETWEEN COSMOCHEMISTRY AND THE EARTH′S EVOLUTION HISTORY

This paper discusses the implication of some significant achivements which have been made in recent years on cosmochemistry to the origin and evolution process of the Earth. The Earth was formed by a suit of planetesimals with independant chemical compositions through the mechanism of collisional accreation. The planetesimal accumulated formation style and the initial inhomogeneity of chemical compositions of the Earth had constrained strongly on the non homogeneity and non uniform evolution process of the Earth at late stages. As a turning point of 1800Ma, the evolution of the Earth can be divided into the early stage and the late stage characterised by the formation and development of planetesimal derived terrains and by the movement of lithospheric plates respectively. Extraterrestrial impact events in the Earth′s evolution history are thought to be the continuance of collisional accreation—the formation mechanism of solar system, and may play an important role in the organism evolution, sedimentation, magmatism, tectonic etc.