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THE MAIN STAGES OF CRUSTAL DEVELOPMENT OF CHINA

Wang Hongzhen (H. C. Wang)  
The present paper is an outline of the tectonic development of the cr- ust of China, based on the doctrines of mobilism in regard to global tectonics and of development stages in regard to crustal evolution. The mobile point of view in glotectonics as depicted here refers to relative motions between the continents and oceans as in plate tectonics, but special emphasis is laid on the boundary between ancient continental marginal domains which are not necessarily plate boundaries. Crustal subduct-ion and consumption zones within a continental marginal damain are called accretional, while those separating two opposite continental marginal domains are called convergent crustal consumption zones. The conception of development stages implies profound and revolutionary changes of tectonic regime which are effected in a comparatively short duration of time in the geological history, thus giving rise to new stages of development. The evolution of the earth crust is thus conceived as a process of progressive and episodic nature. In regard to spatial relations, the crustal parts of China may be divided into 5 domains. 1 ) Northern Border Domain, consisting of a narrow southern belt representing the northern margin of the North China platform, and a much wider northern belt including such median massifs as Songliao and Dju-ngaria, representing the conplicated southern marginal terrain of the Siberian Platform. In between is the Aibi Lake-Juyanhai crustal consumption zone, which is probably continuous to the east with the Suolun-Silamulun Zone (fig. 1 ) . 2) The Northern Domain, comprising North China and Tarim Platforms, the former composed of Archaean nuclei surrounded by Lower Pro-terozoic fold zones and covered by Middle and Upper Proterozoic paraco-ver sequence, the latter mostly covered by young sediments but also. with old foundation at least Early Protefozoic in age. The Qaidam massif and Median Qilian uplift represent probably another old massif affilated to North China. 3) Southern Domain, the major part of which is the Yangtze, Platform with a Lower Proterozoic nucleus,which was stabilized in pre-sinaia times, and the extensive Caledonides of Southeast China. The western unit of the Southern Domain might be represented by the Qiangtang massif, probably a stable region since from the Palaeozoic. Between the Southern and the Northern Domains lies the Xiugou--Maxin crustal consumption zone, which is continuous with the Shanyang -Tongcheng zone to the east (fig. 4) . Both are closed up in the Indosinan orogeny. 4) Southern Border Domain, comprising the Gandise and Himalaya, representing the true northern rim of the ancient Gondwana. The westernmost part of yunnan is probably its eastern counterpart. In respect to temporal relations, the tectonic history of the crust of China is subdivided into four megastages the essential characteristics of which are as follows. 1 . Megastage of formation of continental nuclei. This corresponds to the pre-Fupingian or Archaean, characterized by permobile tectonic conditions all over the earth, probably with much thinner crust and higher thermal gradient than now. The essential process is probably the continuous aggregation of minute sial masses to form continental nuclei, which have net undergone remarkable changes since its formation. Definite Archaean nuclei are only known within the North China Platform. 2 . Megastage of formation of platforms. This includes the Fupingian-Luliangian and the Luliangian-Jinningian stages and ends with the beginning of the Upper Proterozoic, when stable terrains were probably most extensive on the earth surface. The crustal nature in the Early Proterozoic, i. e. prior to 1900my Bp, is transitional, while the Middle Proterozoic (1900-1000my) represents a steady stabilizing stage leading to tie final formation of platforms. The crust thickness, the atmospheric and hydros-pheric composition were probably not much different than now. In this mega stage, the North China Tarim Continental Domain was most extensive in scope, the northern bounda
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