From the Tethys to the formation of the Qinghai-Tibet Plateau:constrained by tectono-magmatic events
From the Tethys to the formation of the Qinghai-Tibet Plateau:constrained by tectono-magmatic events
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作者：
Mo Xuan-xue
青藏高原被称为“地球第三极”。然而，从特提斯演化到青藏高原形成的过程是一个复杂而漫长的时期。这个过程包括三个阶段：古特提斯、新特提斯以及印度 - 欧亚大陆碰撞和高原形成。古特提斯自早石炭世开始张开，形成了包括修沟 - 玛沁、金沙江 - 哀牢山和澜沧江 - 昌宁 - 孟连等三个洋盆。它在早二叠世达到最大宽度，然后开始板块俯冲。所有古特提斯洋盆在三叠纪末/侏罗纪初闭合，导致冈瓦纳古大陆和劳亚古大陆前缘碰撞。古特提斯的整个演化过程大约历时1.5亿年。几乎与古特提斯闭合同时或更早，新特提斯张开，并随后在早/中侏罗世达到最大宽度，然后开始板块俯冲和消减。班公错 - 怒江洋盆，即新特提斯的北支，在晚侏罗世到早白垩世期间（约1.6亿 - 1亿年）闭合，导致拉萨地块和羌塘地块碰撞。后来，新特提斯的南支雅鲁藏布江洋盆在晚白垩世和早古近纪之交开始闭合，引发了印度 - 欧亚大陆碰撞，这是青藏高原形成的真正起点。这次碰撞的整个过程大约需要2000万年（约6500万 - 4000/4500万年）完成，随后进入碰撞后时期。显然，上述如此巨大的地壳和岩石圈运动，时间尺度达数亿年，空间尺度达数万公里，必然对应着地球内部各个圈层之间巨大的物质 - 能量交换。正是这种巨大的物质 - 能量交换最终导致了青藏高原的形成以及对资源和环境的影响。
The Qinghai-Tibet plateau is known as “the third pole of the Earth”. The process from the evolution of Tethys to the formation of the Qinghai-Tibet plateau, however, is a complex long-term period. This process consists of three stages: the Paleo-Tethys, the Neo-Tethys and the India-Eurasia collision and formation of the plateau. The Paleo-Tethys opened since the early Carboniferous, formed three branches including the Xiugou-Maqing, the Jinshajiang-Ailaoshan and the Lancangjiang-Changning-Menglian oceanic basins. It reached the maximum width in the early Permian and then started with plate subduction. All the Paleo-Tethyan oceanic basins were closed at the end of the Triassic/the beginning of Jurassic, resulting in collision between the fronts of the Gondwana and Laurasia paleo-continents. This whole process for the evolution of the Paleo-Tethys took about 150 Mys period of time. Almost at the same time as the closure of the Paleo-Tethys or earlier, the Neo-Tethys opened and subsequently reached its maximum width in early/middle Jurassic, and then started with plate subduction and consumption. The Bangongco-Nujiang oceanic basin, i.e., the northern blanch of the Neo-Tethys, was closed up in the period from the late Jurassic to the early Cretaceous (about 160-100 Ma), given rise to collision between the Lhasa and the Qiangtang blocks. Later on, southern branch of the Neo-Tethys, the Yarlung Tsangbo oceanic basin started to close at the boundary between the late Cretaceous and the early Paleogene and caused the initiation of India-Eurasia continental collision, the real staring point of formation of the Tibetan plateau. The entire process of this collision took about 20 Mys (65-40/45 Ma or so)to be completed, and subsequently transformed into post-collisional time.Obviously, such a huge crustal and lithospheric movement mentioned above, with hundreds of million years in time scale and tens of thousand kilometers in space scale, must have corresponded to a huge mass-energy exchange among various geospheres of the Earth's interior. It was this huge mass-energy exchange that eventually caused the formation of the Qinghai-Tibet plateau and the influence on resources and environments.