中国大地构造基本特征及其发展的初步探讨

大地构造是地壳形变的结果,而地壳形变是在地壳形成的基础上发展起来的。地壳的形成主要表现为地质体的建造过程,包括地壳形成的地质时期中,不同温度和压力下所产生的沉积岩、岩浆岩和变质岩的类型、组合和相带的发展。地壳的形变主要表现为地质体的改造过程,包括各种岩层在形成过程之中或以后,经受内力和外力作用而产生的各种微观和宏观的结构变化,如流动、褶曲、破碎和断裂等。

A PRELIMINARY NOTE ON THE BASIC TECTONIC FEATURES AND THEIR DEVELOPMENTS IN CHINA

By the method both of geomechanical and geohistorical analysis, the block movements characterizing the basic tectonic features and their developments in China are well-defined on the basis of synthetic analysis of geological and geophysical as well as model experimental data gathered especially during and after the Great Proletarian Cultural Revolution. From the geohistorical point of view, five tectonic cycles and ten orogenic phases are established. By the geomechanical analysis, it has been recognized that the main fault-zones are essentially controlled by two sets of X-shaped shear frac- tures running NNE and NNW as well as NEE and NWW, and further develop into zig-zag fracture zones with transform movements, i.e. shear-tension and shear-compression. The Western Kunlun-the Altyn Tagh-the Northern Chilien and the Tsinling-the Tan-Lu fracture zone may be taken as examples.Three types of fault-blocks in Chinese territory may be preliminarily classified with faulting blocks, folding blocks and warping blocks. From their boundary-movement pattern, three types of fault-zones are also recognized: subductive fault-zone, collision fault-zone and fissuring fault-zone. The first type may penetrate through the whole lithosphere with ancient marine crust underthrusting ancient continental and thus "tectonic-block-suture" is named, the second one usually cut through the continental crust and the term "deep-fault" is suggested, while the third remains within the crust and may be known as fundamental fault.The strati graphical developments in China are essentially controlled by these tectonic block-faulting movements. There are different stratigraphic settings on different blocks usually with zonal developments of stratigraphical breaks along their boundaries.Different types of magmatism are closely related to different types of tectonic blocks. Syntectonic magmatism are often more well-developed in folding blocks, lessin warping blocks and least in faulting blocks. Ultrabasic with basic intrusions andmarine eruptions usually follow tectonic-block-sutures, basic with ultrabasic intrusions and continental eruptions are often accompanied with deep fault-zones, while acidic intrusions and continental eruptions sometimes are associated with fundamental faults. The zonation of magmatic and metamorphic roeks usually depends upon the inclination of the planes of these fault-zones. The zonal arrangements of the types of rocks are distinct in case of moderate dips of these fault-planes whereas they tend to mix together in case of steep dips.The seismicity of China is essentially controlled by tectonic faulted blocks. The epicenter of the main earthquakes usually follow the boundaries of three big block-faulting zones which have been activated since the Cenozoic times. In the Eastern China the Cathysian zone adapted the X-shaped shear fractures running NNE and NNW with the NNE striking ones in predominance, while in the Western the Siyuian and the Tibetian zones adapted the X-shaped shear fractures of NEE and NWW strikes in which the NWW trending predominate. Along these big block-faulting zones, the thickness of the earth’s crust and the gravity anomalies usually show abrupt changes. The tectonic stress-fields in the Mesozoic and Cenozoic times are tentatively assumed and it might. be hopeful to throw light on earthquake prediction.