Linkage between the India–Asia collision and far-field reactivation of the Altai mountains

Abstract

The present northwest-trending Altai mountains, as far as ∼2000 km north of the Indian–Asian collision front, are dominated by a transpressional strike-slip fault system, and are generally considered as one of distant tectonic effects of the ongoing India–Asia collision. However, the Cenozoic reactivation of the Altai and its linkage with the tectonic evolution of the Tibet plateau remain mechanically challenging. Here, we constructed large-scale 2D numerical models with inherited lithospheric heterogeneities from India to Altai representing the onset of the India–Asia collision. The sensitivity of model results to variable thermo-mechanical and geometric properties of the orogen-like Tibet and Altai as well as variable thermal state of the craton-like India and Junggar reveals that both the particular lithospheric architecture of western Tibet and basement structural inheritance of central Asia regulate the long-distance deformation propagation from the India–Asia plate boundary to the Altai–Sayan region. The model results indicate that the direct collision of the underthrusting Indian lithosphere with the rigid Tarim block beneath western Tibet plays a dominant role in the ultra-long-distance deformation propagation to central Asia. As less-deformed rigid blocks, the Tarim and Junggar basins with Precambrian basements serve as secondary indenters that transfer the compressive stresses extensively to the Altai–Sayan region. Constrained by substantial surface geology and geophysical observations, this numerical study recognizes the linkage between the evolving lithospheric structure of western Tibet with the northward younging trend of reactivation of the orogenic belts in central Asia. By means of the rigid Indian–Tarim lithospheric mantle collision, the plate-convergence stress can be effectively transmitted through Tarim to Tian Shan and subsequently through Junggar to Altai, leading to successive reactivation of the Tian Shan and Altai mountains. The locations of reactivation are determined by the inherited structural zones of lithospheric weakness that formed during the Paleozoic assembly of the Central Asian Orogenic Belt.