Cenozoic uplift and volcanism of Hangai Dome, central Mongolia triggered by lower mantle upwellings

The mechanisms of surface uplift of Hangai Dome (>2km) and formation of Cenozoic intraplate volcanism in central Mongolia remain vigorously debated. Here we directly investigate the mantle transition zone (MTZ) structure beneath central Mongolia to explore whether the deep mantle geodynamical processes have played a role. Our results reveal significant MTZ thinning of 10-13 km in three subareas mainly caused by the uplifted 660-km discontinuity (~10 km) (Figure 1a). In addition, the 410-km discontinuity is depressed beneath the Hangai Dome (~6 km) and the northern portion of the study area (10-15 km). These observations provide direct evidences for intracontinental mantle upwellings from the lower to the upper mantle, which would cause thermochemical erosion of the lithospheric root, thus significantly contributing to the Cenozoic uplift and basaltic volcanism of central Mongolia (Figure 1). Specially, these mantle upwellings are relatively sluggish compared to canonical mantle plumes based on the small magnitude of MTZ thinning and thus relatively moderate thermal anomaly within the MTZ (61-100 K).

Figure 1. Schematic diagram for tectonic evolution in central Mongolia. (a) Present-day MTZ structure and geodynamical processes. A, B, and C denote the locations of upwellings from the lower mantle, which are relatively sluggish and cooler than canonical plumes. Lithosphere-asthenosphere structures and accompanied geodynamical processes along 100.5°E longitudinal profile (b) before the lithospheric thinning and doming of the Hangai and (c) at present. The lithosphere is heterogeneously thinned beneath central Mongolia at present with the most significant thinning beneath the Hangai Dome.

This study is led by Prof. Xuewei Bao (the corresponding author), a Hundred-Talent-Plan research professor at School of Earth Sciences, Zhejiang University. The first author of this study is Yingkai Wu, a Ph.D. student in Bao’s group.

For more details: Wu, Y., & Bao, X. (2023). Cenozoic uplift and volcanism of Hangai Dome, central Mongolia triggered by lower mantle upwellings. Geophysical Research Letters, 50, e2023GL102838. https://doi.org/10.1029/2023GL102838.