前寒武纪沉积岩地球化学特征及其对地壳演化的指示意义

本文介绍了运用前寒武纪沉积岩地球化学特征推断地球早期地壳的组成、增生历史及太古—元古宙界面构造性质突变问题,这已成为国际前寒武纪地质研究的前沿课题,并已相继在世界典型的前寒武纪低级区及部分高级区开展了这一方面的研究工作,取得了一系列重要进展。

GEOCHEMISTRY OF PRECAMBRIAN SEDIMENTARY ROCKS AND ITS IMPLICATIONS FOR CRUSTAL EVOLU TION

The evolution of the early crust such as its composition, accretion history and Ar-chaean-Proterozoic transition can be deduced from geochemistry of the Precambrian sedimentary rocks. It has been investigated from some typical low-grade terrains and partial high-grade terrains in the world, and some important results have been reported. For example, crust composition of source area may be reflected by the elements of Ti-group, Al-group and REE, Th, Nb, Sn, Be in the precambrain sedimentary rocks; Distribution patterns of REE in fine grained clastic sediments and research results of isotope Sm-Nd have shaken the crust growth model presented in 70's; REE and other trail elements in sedimentary rocks show essential differences on Archaean-Proterozoic border surface; Chemical compositions of chemical sedimentary rocks reveal some characteristics of early hydrosphere and atmosphere; In partial high-grade terrains quartzite-feldspathic sandstone-argillite-carbonatite associatoin and limestone-shale turbidite association have been studied.