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CHINA AND MONGOLIA 357 evolution of China included three megastages in the Precambrian, marked respectively by the aggregation of continental nuclei (2.8 Ga), the lateral growth and consolidation of proto-platforms through the Luliangian Orogeny (1.8 Ga), and the cratonization and coalescence of platforms into the Cathaysiana Supercontient through the Jinningian Orogeny (830 Ma) Until the Jinningian, the crustal evolution of China seems to have been dominated by continental growth, consolidation, and convergence to form a part of the Neoproterozoic Rodinia In Mongolia, only the last megastage, ending at 830 Ma, marked by the formation of the main massifs, is recognized After the Jinningian, China and Mongolia entered a megastage characterized by a tectonic pattern consisting of discrete continents and ocean basins, until their reassembly at the close of the Indosinian Orogeny (210 Ma) The Cathaysiana Supercontinent began to dissociate in the Cambrian, and ocean basins were formed between Sino-Korea and Qaidam, which was entirely closed through the Caledonian Orogeny, with marked collision zones The wide Caledonide between Yangtze and Cathaysia was, however, folded and uplifted without clear collision To the north of Tarim and Sino-Korea, the narrow Caledonides represent continent-arc accretion In Mongolia, the northern Mongolian massifs were successively accreted to the Siberia Platform, and the Mongolian massifs, the Salairides and Caledonides, together formed the northern Mongolian palaeocontinent, with the Gobi-Altai Caledonian Belt as its southern margin Two main branches of Late Palaeozoic oceans, the Zaysan-South Mongolia-Hingan in the north, and the Ural-Tianshan in the south, were consumed mainly after the Early Carboniferous, and are represented respectively by the main Hercynian sutures (Figure 1) The Late Carboniferous to Early Triassic marine basins in southern Mongolia and Inner Mongolia of China probably formed an ocean with scattered islands that were filled up without appreciable collision Furthermore, the Late Hercynides-Indosinides within northern Mongolia were actually intracontinental residual seas To the south of the Kunlun-Qinling central orogenic belt of China, an open sea had persisted since Early Palaeozoic, and the wide Indosinides are marked by the main Indosinian (Muztagh-Maqen) convergent zone in the north and the Jinshajiang zone in the south The main collision zones usually coincide with older collision zones; in other words, they are polyphased or superimposed collision zones It was at the close of the Indosinian Stage that the Laurasia Supercontinent took its final shape as the northern half of the Permian-Triassic Pangaea The post-Indosinian megastage of China and Mongolia witnessed an entirely new tectonic regime in East Asia, due to the appearance of the CircumPacific domain as a result of Pangaea disintegration and the opening of the Atlantic The subduction of the western Pacific beneath East Asia in the Jurassic caused a continent marginal magmatism along eastern China, including the Hingan belt and eastern Mongolia This new pattern brought about an apparent change of contrast between northern and southern China to that between eastern and western China In eastern China, and to a certain extent in eastern Mongolia, there occurred a combination of continental margin type and intracontinental type of volcanism, which was followed by the Late Cretaceous to Cenozoic tensional regime of rifted basins and consequent crustal and lithospheric thinning In western China, the tectonic process in the QinghaiTibet Plateau consisted of the northward accretion of the Gondwanan massifs to Eurasia, characterized by the northward subduction of the Himalaya beneath Gangise in the south, the distributed crustal thickening and shortening in the middle, and the southward indentation from Tarim and Mongol-Siberia in the northern part The contrast between the compressional versus extensional, and between the crustal and lithospheric thickening versus thinning regimes between western China and eastern China are evident These features may have reflected and induced the deeper process of an eastward flow of the asthenosphere from under western China, which might have, in turn, caused mantle upwelling and crustal and lithospheric thinning in eastern China See Also Asia: Central; South-East Gondwanaland and Gondwana Indian Subcontinent Japan Pangaea Russia Further Reading Badarch G, Cunningham WD, and Windley BF (2002) A new terrane subdivision for Monglia: implications for the Phanerozoic crustal growth of Central Asia Journal of Asian Earth Sciences 21: 87 110 Deng JF, Zhao Hailing, Mo Xuanxue, Wu Zongxu, and Luo Zhaohua (1996) Continental roots plume tectonics of China: key to the continental dynamics Beijing: Geological Publishing House (In Chinese with English abstract.) Dewey JF, Shackelton RM, Chang C, and Sun W (1994) The tectonic evolution of the Tibetan Plateau Philosoph ical Transactions of the Royal Society of London, Ser A 327: 379 413 He Guoqi, Li Maosong, Liu Dequan, Tang Yanling, and Zhou Ruhong (1988) Palaeozoic Crustal Evolution and
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