Abstract
Successive indentations of Eurasia by India have led to the Tibet-Himalaya E–W orthogonal collision belt and the SE Tibetan Plateau N–S oblique collision belt along the frontal and eastern edges of the indenter, respectively. The belts exhibit distinctive lithospheric structures and tectonic evolutions. A comprehensive compilation of available geological and geophysical data reveals two sudden tectonic transitions in the early Eocene and the earliest Miocene, respectively, of the tectonic evolution of the orthogonal belt. Synthesizing geological and geochronological data helps us to suggest a NEE–SWW trending, ~450 km-long, ~250 km-wide magmatic zone in SE Tibet, which separates the oblique collision belt (eastern and SE Tibet) into three segments of distinctive seismic structures including the mantle and crust anisotropies. The newly identified Yongping basin is located in the central part of the magmatic zone. Geochronological and thermochronological data demonstrate that (1) this basin and the magmatic zone started to form at ~48 Ma likely due to NNW–SSE lithosphere stretching according to the spatial coincidence of the concentrated mantle-sourced igneous rocks on the surface with the seismic anomalies at depth; and (2) its fills was shortened in the E–W direction since ~23 Ma. These two dates correspond to the onset of the first and second tectonic transitions of the orthogonal collision belt. As such, both the orthogonal and oblique belts share a single time framework of their tectonic evolution. By synthesizing geological and geophysical data of both collision belts, the indenting process can be divided into three stages separated by two tectonic transitions. Continent–continent collision as a piston took place exclusively during the second stage. During the other two stages, the India lithosphere underthrust beneath Eurasia.
Highlights
A Brief Review of Cenozoic Geology of the Tibetan PlateauThe Tibetan Plateau is an ideal natural laboratory for studies of continental collision dynamics [1,2] and has been a focus of multidisciplinary research for more than a century
These belts are known as the Tibet-Himalaya and the Southeastern (SE) Tibetan Plateau [5], respectively, and they are currently separated by the Eastern Himalaya Syntax (EHS) [6]
The observations outlined above suggest that two tectonic transitions in the early Eocene and in the earliest Miocene, respectively, divide the tectonic evolution of the Tibetan Plateau into three stages
Summary
The Tibetan Plateau is an ideal natural laboratory for studies of continental collision dynamics [1,2] and has been a focus of multidisciplinary research for more than a century. Guo and Wilson [43] revealed a transformation in the nature of the post-collisional magmatism in Tibet at ~25 Ma by comprehensive compilation and modeling simulations of available geochemical data of the Cenozoic magmatic rocks across the Tibetan Plateau They found that the continental lithosphere-derived components in the mantle sources of the post-collision magmatic rocks are distinctive before and after 25 Ma. The observations outlined above suggest that two tectonic transitions in the early Eocene and in the earliest Miocene, respectively, divide the tectonic evolution of the Tibetan Plateau into three stages.
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