摘要
本文从不同方面和断代论述了中国东南地区的基底杂岩时代、性质、构造环境、边界变质条件、地球物理场及其反映的构造格局、断裂体系、中生代火山活动的基底构造及类型分区。在此基础上提出了东南地区的构造划分及构造演化阶段和格局。并提出了不同类型的地体及其分类、大陆裂解、增生的新概念。
This paper have discussed some features of the age of basement complex . tectonic environment , boundary metamorphic condition, geophysical field.fault system, basement structure of volcanic activity in southeast area of China according to many materials.
Based on informations, authors divide southeast area into different stage and pattern of tectonic evolution and also suggest some new concept about different types of terrain, continental breakup and accretion.
The results from synthetic study on geology, geochemistry and geophysics in southeast China indicate that geotectonic pattern of southeast China continent is charaterized by offshore accretion of Eurasia continental margin. Besides exotic terrane, the distinctive growth terrane and breakup-tectonic magmatic terrane also appear in southeast China: the former, caused by crustal spreading and mantle upwarping developed in form of continentization of oceanic crust and offshore accretion, the latter, new regional growth structure layer, was formed by way of that unstable crust leads continental breakup, then mantle prism-hotspot materials intrudes thinned - disurpted crust. Tectonic magmatic terrane consists of such distinctive magmatic complex as A-type granite and rhyolitic chain etc. These silica-, alkali-and sodium-rich rocks with high DI value appear in the gravity gradient belt of Eurasia continental margin. The crustal structure models of breakup belts are as follows: upper crust contains a sialic lower velocity zone of unstable gravity; intermediate crust consists of oceanic-continental transitional crust-' similar rift type' structure, with P wave velocity of 6. 3-6.4 km / s; lower crust contains a high velocity (7.0-7.4km / s) of crust-mantle mixture type. Along with the forming of ' anomalously' upper mantle, thermal activity and crust-mantle border upwarp took place on a large scale. The up warp is characterized by thinner crust cover than normally regions.
Because of the differences of crustal structure in southeast China, chemical reservoir and chemical boundary layer are not continuous in transverse, the geologic history displays intensive uncoordinated in different terranes . Therfore, we have divided southeast China into two sub-plates with different paleobasement and late period geologic history, eight terranes which are fault-bounded geologic entities of regional extent, each characterized by a geologic history which is distinct from that of neighboring terranes;one spread-breakup tectonic magmatic terrane of recently growth structure layer, was mainly caused by breakup and composed of hotspot tracks, which is rather important in Eurasia continental margin.
出处
《火山地质与矿产》
1991年第3期15-24,共10页
Volcanology & Mineral Resources
关键词
地壳
演化
地球物理
大陆
age. boundary metamorphic belt, geophysics, the crust evolution.
