Control of stepwise subduction and slab breakoff on volcanism and uplift in the Tibetan Plateau

Abstract

The Tibetan Plateau plays a crucial role in both Asian and global geomorphology and climate dynamics. However, the precise mechanisms through which its deep geodynamic processes influence surface systems have remained elusive. Here, we present a novel model that can be used to evaluate these processes, employing a comprehensive approach that incorporates multistage bilateral subduction, lithospheric breakoff, and subsequent foundering based on a combined analysis of global tomography, volcanic rock ages, and geochemical isotopes. By analyzing seismic tomography data derived from extensive seismic arrays recording over 18 million multi-phase arrival times, we have constrained the locations and morphology of remnant slabs associated with the subduction of the Neo-Tethyan Ocean, Greater Indian plate, and Asian lithosphere. Our findings reveal a striking correlation between discrete episodic surface volcanism and plate uplift at distinct intervals: 56–44 Ma, 44–28 Ma, 28–18 Ma, and 18–0 Ma within the Tibetan Plateau. These intervals correspond to four stages of stepwise lithospheric subduction. Paired slab-like anomalies observed during the second and third steps suggest simultaneous detachment of subducting lithosphere from opposing directions. Building upon this observation, we propose a two-sided breakoff model. This model posits that bilateral subduction and lithospheric gravitational subsidence have induced extensive volcanism and episodic uplift within the Tibetan Plateau. The subsidence, resulting from both past and ongoing lithospheric break-offs of the Indian and Asian plates, has triggered widespread volcanism that likely exerts a significant impact on climate patterns. Our study establishes a systematic framework linking deep lithospheric processes with surface phenomena in Tibet, providing valuable insights into the dynamic interactions shaping the region's geological and climatic evolution.