Multi-terrane structure controls the contrasting lithospheric evolution beneath the western and central–eastern Tibetan plateau

Abstract

The Tibetan plateau is manifested by contrasting along-strike lithospheric structures, but its formation mechanism and the relationship with the heterogeneous multi-terrane configuration is a challenging problem. Here we conduct systematic numerical modeling to explore the roles of width, density, and rheological properties of the multiple terranes in the lithospheric evolution of the Tibetan plateau, which reveals two distinct collision modes. In Mode-I, the lithospheric mantles of both the strong and weak terranes in the Tibetan plate are completely detached, followed by the underthrusting of Indian lithosphere beneath the whole plateau. Alternatively, Mode-II is characterized by full detachment of the weak terranes, but (partial) residue of the strong terranes during collision. These two contrasting modes, broadly consistent with the lithospheric structures of western and central–eastern Tibetan plateau, respectively, are strongly dependent on the along-strike variation of the width of the strong Lhasa–Qiangtang terranes.

Lithospheric Structure of Eastern Tibetan Plateau from Terrestrial and Satellite Gravity Data Modeling: Implication for Asthenospheric Underplating

“…The configuration of the lithospheric mantle and asthenospheric material depicted in the gravity models ( Figures 5-9) are in favor of studies suggesting underplating in the western part of Tibet [22,52,126] with a steeper slab in the eastern part of the plateau ( [15,51,127,128]). The lithospheric thicknesses discussed in this study are in direct support of distributed crustal thickening together with the subsequent convective removal of the lithospheric mantle below the central and eastern Tibetan plateau [47,48,52]. More recent research [45] suggests rapid removal below the Qiantang and Songpan-Ganze terranes but not below the Lhasa terrane due to the absence of the Tibetan lithospheric mantle material below Lhasa's mantle transition zone [123,124,129].…”

“…Even though the slab is at a greater depth today, it is still sinking. Similar to the delaminated lithospheric mantle, the sinking slab may have induced upward asthenospheric flow, as shown by a numerical model from Huangfu et al [47]. Thus, the past asthenospheric flow beneath the central and eastern Tibetan plateau might have been induced by the combination of a delaminated lithospheric mantle and the last slab breakoff event.…”

“…This is also consistent with shear wave anomalies seen in recent work from Chen et al [29] which suggests recent asthenospheric upwelling and thermal erosion of thickened lithosphere responsible for the observed potassic volcanism. Seismic tomography images a low velocity anomaly in the uppermost mantle which is interpreted as asthenospheric material [47][48][49]. Hence, a thinner lithospheric mantle underlain by a low-velocity asthenospheric material is suggested below the eastern Tibetan plateau.…”

“…The LAB decreases to 120-140 km below the Lhasa, Qiangtang, and Songpan-Ganze terranes. On the northern end of the profiles, the LAB depth increases to 160-180 km below Qaidam Basin due to the presence of a downgoing Asian slab [47,52,109]. The densities of the asthenosphere were constrained using an eastern and western Tibetan plateau tomographic model [52].…”

Dynamics of crustal overthrust versus underthrust in the continental collision zones: Numerical modelling

“…One typical example of crustal overthrust is the Dinarides, where the Dinaridic crust, belonging to the Adriatic/African units, clearly migrates onto the European plate over 100 km, confirmed by the gravity model, tomographic imaging and surface heat flow distribution (Koulakov, Kaban, Tesauro, & Cloetingh, ; Šumanovac, ; Figure a). Alternatively, crustal underthrust is well represented in southern Tibet, where the Indian lower crust sub‐horizontally underthrusts Tibetan crust for hundreds of kilometres (DeCelles, Robinson, & Zandt, ; Huangfu et al., ; Nábělek et al., ; Tilmann et al., ; Xu, Zhao, Yuan, Liu, & Pei, ; Figure b).…”