中国与蒙古之地质

按照构造单元和构造阶段讨论中国和蒙古的演化史。中国前寒武纪地壳演化可分3大阶段:陆核的聚结(2·8Ga);原地台在吕梁运动中固结和侧向增生(1·8Ga);地台在晋宁运动中固化拼合成华夏超大陆(830Ma)。晋宁运动后,中国和蒙古以离散大陆和洋盆并存为特征,至早古生代末聚合为中国和北蒙古两个古大陆。晚古生代时,斋桑—南蒙古—兴安和乌拉尔—天山两大海域陆续消减,形成了海西期的主缝合带。中国蒙古各地块大致于印支运动末期(210Ma)重新聚合,成为劳亚超大陆,即二叠纪—三叠纪泛大陆北支的一部分。印支期后大阶段的特征是泛大陆裂解和大西洋扩张导致了环太平洋域的出现,这一新的构造型式使中国由南北部之间的差异转变为东西部之间的差异。中国东部,也包含蒙古在内,在中—新生代基本上处于张性构造状态,发育张裂盆地和大陆内部火山活动;而在中国西部,中—新生代的构造发展过程则表现为亲冈瓦纳诸地块陆续向北增生拼贴到古亚洲大陆之上。这个过程最终导致了青藏高原在中新世至第四纪的迅速上隆。

The geology of China and Mongolia

The geological history of China and Mongolia is discussed in terms of tectonic units and tectonic stages. The crustal evolution of China in the Precambrian included three megastages, marked by the formation of continental nuclei (2.8 Ga), of protoplatforms through the Lüliangian orogeny (1.8 Ga), and of the Cathaysiana Supercontient through the Jinningian orogeny (830 Ma). The Cathaysiana and Mongolia were both part of the Neoproterozoic Pangaea. After the Jinningian orogeny, China and Mongolia entered a megastage of discrete continents and ocean basins, which converged into a Cathaysian palaeocontinent and a northern Mongolian palaeocontinent at the end of Early Palaeozoic. Two main branches of Late Palaeozoic oceans, the Zaysan-South Mongolia-Hing'an and the Ural-Tianshan, were closed at the end of Late Palaeooic. China and Mongolia were on the whole re-assembled after the Indosinian orogeny to become part of the Laurasia Supercontinent, which was the northern half of the Permian-Triassic Pangaea. The post-Indosinian megastage was chracterized by the appearance of the Circum-Pacific tectonic domain caused by Pangaea disintegration and opening of the Atlantic. This new tectonic pattern brought about a basic contrast between eastern China and western China. In Late Mesozoic and Cenozoic times, eastern China,and to a certain extent Mongolia, were mainly dominated by a tensional regime consisting of rifted basins and intracontinental type of volcanism, whereas western China witnessed a successive northward moving and collaging of the Gondwana-affiliated massifs onto the southern margin of the Asian paleocontinent. These processes finally resulted in the rapid uplifting of the Qinghai-Tibet Plateau in Miocene to Quaternary times after the major India-Asia collision event.