Uplift of the Tibetan Plateau

Abstract

The Tibetan Plateau is the highest plateau in the world, located southwest of China. It lies between several mountain ranges: the Kunlun Mountains to the north, the Himalayas and Karakoram Range to the south and southwest, and the Daxue Mountains to the east. The Tibetan Plateau encompasses the Tethyan-Himalaya thrust belt, the Lhasa terrane, the Qiangtang terrane and the Jinsha and Kunlun sutures, all of which represent their own diverse geological history. Due to the complexity of the area, uplift history and geological evolution of the Tibetan Plateau are poorly understood. Several models have been proposed and to describe the complex history of the region, which accommodate mechanisms acting along active margins of the plateau. A popular model assumes that the thick crust and high elevation of Tibet are a direct result of the continental collision between India and Asia since the Eocene. Crustal thickening is attributed to convective removal of the lower portion of the thickened lithosphere in this model, followed by east-west extension as a result of this removal. This model is based on magmatism throughout the Tibetan Plateau where potassic lavas to the east (30-40 Ma) are compared to potassic lavas from the west (20 Ma) and are interpreted to represent diachronous uplift in the history of the plateau. Other common models for the formation of the interior involves activity along the active margins along the plateau, such as: northward underthrusting of Indian lithosphere, homogenous lithospheric shortening/thickening, upper-crustal shortening followed by passive infill of basins and oblique subduction along sutures, and lastly thickening and flow of weak crust from the continental collision zone powered by topographic gradient. More recent studies, however, have challenged these prior models with evidence showing that portions of south Asia underwent major crustal shortening and thickening prior to the Indo-Asian collision. This was indicated by carbon and oxygen isotopic studies, indicating high paleo-elevation in the late Oligocene. The conflicting views for the uplift of the Tibetan Plateau illustrate the need to readdress theories on paleo-elevation, shortening and geochemical properties of the area, to understand how the Tibetan Plateau truly became ‘the roof of the world’.

 

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