青藏高原造山带的垮塌与高原隆升

Collapsed Himalayan-Tibetan orogen and the rising Tibetan Plateau

印度与亚洲的碰撞及前期的地体拼合产生了世界上规模最大的青藏高原碰撞造山带,并进而导致了高原的形成。但关于该造山带的形成演化过程与高原隆升的关系,一直未能取得明确的共识。本文通过对近几年来的资料总结发现,印度与亚洲的碰撞大约发型在55 Ma左右。由于新特提斯大洋板块的断离作用,形成冈底斯地区大规模的古新世—始新世花岗岩和火山岩,并发生青藏高原第一次较大规模的隆升。随着印度板块的持续向北挤压和朝亚洲大陆下的不断俯冲,该造山带岩石圈不断增厚,并在≈26 Ma左右发生岩石圈拆沉和减薄,形成全区的新生代钾质与超钾质岩浆活动,并发生全区范围内的大规模地壳隆升与剥蚀。中新世及以后,除局部地区外,青藏高原总体隆升幅度不大。因此,青藏高原的隆升与造山带的垮塌有关,而并不是由印度与亚洲碰撞而直接产生的。

India - Asian collision and former terrane amalgamation yielded the largest collisional orogenic belt of Tibet in the world, and subsequently resulted in the formation of the Tibetan Plateau. However, it is controversial about the relationship between the orogenesis and Tibetan Plateau uplift. Based on a comprehensive summary of the data obtained during past decades, it is proposed that the India - Asia collision took place at - 55 Ma. The break - off of the Neo - Tethyan oceanic plate caused a large scale of Paleocene -Eocene granites and volcanic rocks in the Gangdese area with the first stage of significant uplift of the plateau. The continued northward movement of the Indian plate and subduction beneath the Asian plate resulted in the lithospheric thickening of the whole orogen, which was lithospherically delaminated at - 26 Ma with development of coeval potassium - ultra potassium magmatic activities and large scale of crustal uplift and erosion. Since Miocene, the Tibetan plateau was not uplifted significantly except for some local areas. Therefore, it is proposed that the uplift of the Tibetan Plateau was caused by collapse of the Tibetan orogen, rather than by the direct collision between India and Asia.