India Indenting Eurasia: A Brief Review and New Data from the Yongping Basin on the SE Tibetan Plateau

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.

Petrogenesis of the Late Eocene to Early Oligocene Yao'an Shoshonitic Complex, Southeastern Tibet: Partial Melting of an Ancient Continental Lithospheric Mantle beneath the Yangtze Block

“…Since the early Paleocene (~60 Ma, e.g., Hu et al, 2015, the successive indentation of India into Eurasia has generated the E-W-trending Tibet-Himalaya orthogonal collision belt and the N-S-trending SE Tibetan Plateau oblique collision belt along the frontal and eastern edges of the indenter, respectively (Fig. 1a; Molnar and Tapponnier, Yang et al, 2021;Dong et al, 2022).…”

“…This contribution focuses on the YSC, trying to reveal its magmatism process using both published geochronological, geochemical and zircon Hf-O isotopic data and our new data. Combined with recent advances in tectonic study (Yang et al, 2021;Liang et al, 2022), we also try to discuss the tectonic implications of the YSC.…”

Early Late Triassic retro-foreland basin in response to flat subduction of the Paleo-Tethyan oceanic plate, SE Tibet

“…This spatiotemporal relationship between these tectonic units (Figure 1B) makes it hard to understand tectonic nature of the basin represented by volcanicabsent sedimentary rocks of the transitional unit (Burchfiel and Chen, 2012). Widespread Mesozoic and Cenozoic basins, such as the Cretaceous Lanping basin (Liang, 2017 and references therein) and the Eocene Jianchuan basin (Liao et al, 2020) as well as the crustal deformation induced by the India-Eurasia collision (Yang et al, 2021;Liang et al, 2022) worse the situation.…”

“…The locations of the study areas are marked in Figure 2A. , 1986;Burchfiel and Chen, 2012;Yang et al, 2014Yang et al, , 2021. The two blue dashed lines are the approximate boundaries separating the northern, middle, and southern segments of the Jomda-Weixi-Yunxian arc belt, respectively.…”

“…FIGURE 1 (A) Tectonic framework of China mainland showing the location of the Sanjiang orogenic belt. (B) Simplified geological map of the Sanjiang orogenic belt showing the tectonic framework and the locations of the Transitional Unit (thick dash-line) and the study area (the solid polygon) (modified after ECSGM, 1986;Burchfiel and Chen, 2012;Yang et al, 2014Yang et al, , 2021. The two blue dashed lines are the approximate boundaries separating the northern, middle, and southern segments of the Jomda-Weixi-Yunxian arc belt, respectively.…”