The influence of slab window asthenospheric flow on intraplate volcanism, dynamic uplift, and present-day mantle heterogeneity in East Asia

It is generally accepted that East Asian mantle dynamics has been dominated by subduction and downwelling since Mesozoic times (e.g. Müller et al. (2016)). However, seemingly in contrast to this history, a variety of observations indicate a presence of anomalously hot asthenospheric material beneath East Asia during the late Cenozoic. First of all, tomographic models consistently reveal an extensive network of seismically slow anomalies at asthenospheric depths, which align spatially with a recent (< 30 Ma) phase of intraplate volcanism. The influence of this positively buoyant material at the surface is further highlighted by induced dynamic uplift, which is recorded in the geological record through an inter-regional sedimentary hiatus during the late Eocene—Oligocene. Residual topography studies additionally find swells of dynamic uplift throughout this region in the present day. Global mantle circulation models (MCMs) show that these observations can be reproduced in a subduction-dominated region by the spillover of anomalously hot asthenospheric material from the adjacent Pacific domain during ridge subduction events. In particular, the subduction of the Izanagi-Pacific ridge at ~55 Ma provides a large window through which Pacific asthenosphere could have flowed into East Asia. We test this hypothesis by comparing these MCMs to a variety of geological observations, including the distribution of sedimentary hiatus and intraplate volcanism during the late Cenozoic. We additionally compare the present-day distribution of hot material predicted by these models with the recently published full waveform inversion tomographic model of the region, Sinoscope 1.0, which highlights the distribution of seismically slow anomalies beneath the region. We find an encouraging match between asthenospheric flow predicted by these models and the observations considered, showing this to be a viable new hypothesis in explaining these observations. The mechanism of hot asthenospheric build-up during subduction and release during slab window opening may not be limited to East Asia, and could reconcile observations of intraplate volcanism and dynamic uplift in convergent regions more generally.