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The uplift of the Qinghai-Tibet Plateau is one of the most important Cenozoic geological events in the world. It not only affects the tectonic pattern of Eurasia, but also has a far-reaching impact on the global climate change since the Cenozoic era. However, for a long time, the spatio-temporal mechanism of the deformation and surface uplift of the continental lithosphere of the Qinghai-Tibet Plateau during the India-Asia continental collision is still unclear.

Satellite images of the Qinghai-Tibet Plateau. Image source: NASA in recent years, with the accelerated generation of quantitative paleo-elevation data, scholars gradually realize that the plateau has the characteristics of differential uplift, and the uplift time in some areas is earlier or later than the previous hypothesis. However, the existing dynamic models can not fully reflect the uplift process of the plateau.

"A complete evolution model of the Qinghai-Tibet Plateau must take into account the paleogeomorphology and lithospheric heterogeneity of Asia in the tectonic events before the India-Asia collision, which is very important for understanding the differential uplift of the Qinghai-Tibet Plateau." The research team led by Professor Ding Lin of the Institute of Qinghai-Tibet Plateau of the Chinese Academy of Sciences recently published an article systematically explaining the differential uplift process of the Qinghai-Tibet Plateau since the Cretaceous and its related deep dynamic mechanism. He said that at present, the widely used paleo-highly quantitative reconstruction techniques include hydrogen / oxygen isotopes, animal and plant fossils, cluster isotopes and so on. These paleo-height quantitative reconstruction techniques provide key information for continental deformation and plateau growth, and can better understand the differential uplift process and dynamic mechanism of the plateau.

Through a detailed analysis of the Cretaceous evidence on the Qinghai-Tibet Plateau, the team proposed that the collision of the Lhasa-Qiangtang terrane and the subsequent northward subduction of the Lhasa lithosphere led to the initial growth of the watershed mountains; the continuous subduction of the Neo-Tethys Ocean plate uplifted the Gangdise Mountains above sea level about 9500 years ago, forming the Gangdise Mountains, but the extent of surface uplift remains to be quantified.

The time and mode of India-Asia plate collision is the key to limit the surface uplift and deep dynamic amplitude of the plateau. At present, the hypotheses about the closure history of the Neo-Tethys Ocean and the initial India-Asia collision include the Greater India Basin model, the intraoceanic subduction model and the single-stage subduction collision model. These hypotheses make very different predictions of the outcome and timing of the collision.

However, all these models are based on a key evidence first discovered by Professor Ding Lin's team, that is, the Foreland basin formed by the Indo-Eurasian collision, which began to accept the provenance of the Gangdise arc 65 million to 59 million years ago. this indicates that the Indo-Eurasian plate collision has begun at this time. Therefore, the team believes that the single-stage subduction-collision model is the simplest model to explain the Indo-Asian collision and is supported by geological evidence.

Combined with the existing results of quantitative paleolatitude and deep dynamic evidence, the research team further restored the history of surface uplift and lithospheric evolution of the Qinghai-Xizang Plateau from about 6000 million years ago to the present day, indicating that different orogenic belts of the Qinghai-Xizang Plateau have different uplift history.

About 4500-4000 million years ago, after the rupture of the Neo-Tethys Ocean plate, the more buoyant Indian lithosphere wedged northward horizontally, activating the suture zones in the north and south of the Qiangtang body and carrying out internal subduction, causing the watershed mountains to rise to a high altitude of 5000 meters. At this time, the valleys in central Xizang between the Gangdise Mountains and the watershed, and the Himalayas in the south and north of Xizang are still at low elevations. Xizang's paleo-topography shows a geomorphological state of "two mountains with low valleys".

About 4000-3000 million years ago, the Lhasa lithosphere collapsed below the central valley, and various deep geodynamic processes such as crustal shortening and asthenosphere upwelling caused the central valley to rise to the current height of 4500 meters. At this time, the Qinghai-Tibet Plateau was officially transformed from an orogenic belt to a plateau.

Pixabay.com about 25 million to 1500 million years ago, due to the continuous subduction of the Indian continent, the Indian continental lithosphere subducted under the Himalayas and the Asian continental lithosphere subducted under the Kunlun Mountains in the north of Xizang, the Himalayas and Kunlun Mountains rose to modern heights one after another, forming a modern plateau.

However, the study shows that the uplift history of the northern Qinghai-Xizang Plateau is still uncertain. In order to solve the time and mechanism of the uplift of the Qinghai-Tibet Plateau as a whole, further research is needed and more quantitative paleo-elevation data are needed to verify it. For example, the evolution history of the plateau earth system should be accurately reconstructed by combining numerical simulation and geological data, and the cycle process and distribution range of the continental lithosphere should be clarified by combining geophysical imaging technology and geodynamic simulation. analyze how continental collisions affect the tectonics of adjacent plate boundaries and mantle convection on a global scale.

References:

1.Ding, L., Kapp, P., Cai, F. Et al. Timing and mechanisms of Tibetan Plateau uplift. Nat Rev Earth Environ (2022). Https://doi.org/10.1038/s43017-022-00318-4

2.Li, Y. (2022). Exploring the timing and mechanism of Tibetan Plateau uplift. Https://phys.org/news/2022-08-exploring-mechanism-tibetan-plateau-uplift.html

This article comes from the official account of Wechat: intellectual Society academic Circle (ID:zhishexueshuquan), author: intellectual Society

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