A Newly Discovered Late‐Cretaceous East Asian Flat Slab Explains Its Unique Lithospheric Structure and Tectonics

Abstract

Different from normal subduction, flat slabs have small dip angles and lie nearly horizontally beneath an overriding plate. The best examples for ongoing flat subduction are those beneath South America, clearly seen in geophysical images (Gutscher et al., 2000;Hayes et al., 2012) and likely caused by subducting oceanic plateaus and nearby cratonic roots Manea et al., 2012). However, due to sparse observational constraints, the existence and mechanisms of flat slabs during the geological past remain debated, especially in regions with a complex tectonic history. A notable example is the Late Cretaceous-early Cenozoic Farallon flat slab beneath the western

Dynamics of the Subducted Izanagi-Pacific Plates Since the Mesozoic and Its Implications for the Formation of Big Mantle Wedge Beneath Eastern Asia

“…The linkage between the Izanagi plate subduction and the tectonic evolution of East Asia is still controversial because the slab dynamics of the Izanagi plate have not been well resolved. Previous studies have proposed flat-slab subduction of the Izanagi plate to be responsible for the East Asian lithospheric evolution in Mesozoic time Peng et al, 2021b). Our numerical results, which reveal multiple stagnation events of the Izanagi slab in Mesozoic time as an alternative mechanism, provide new insight into the Izanagi slab dynamics and its relation with the East Asian tectonics.…”

“…The formation of such mantle wedge, which may lead to slab-triggered water release and vigorous mantle convective flow that could potentially weaken the lithosphere (e.g., Wang et al, 2016;Yang et al, 2017), is therefore supposed to be responsible for the Mesozoic evolution of the overriding plate that are characterized by magmatic activities and/or lithospheric instabilities in Eastern Asia (Ma and Xu, 2021). The intraplate magmatism along East Asia has disappeared in the Late Mesozoic (~80 Ma) and a flat slab model has been proposed to explain this magmatic termination (Peng et al, 2021b). In contrast, our numerical results still show a stagnation event at 90-70 Ma, but the resultant mantle wedge seems to be smaller than that in the middle Mesozoic (~130 Ma) which might be insufficient to cause large-scale magmatism.…”

Styles of Trench‐Parallel Mid‐Ocean Ridge Subduction Affect Cenozoic Geological Evolution in Circum‐Pacific Continental Margins

“…In normal subduction circumstances, a steep slab subduction is a favorable situation for arc magma production (Peacock, 1990) and back‐arc extension (Sdrolias & Müller, 2006; Yang et al., 2018). Flat slab subduction is thought to greatly facilitate the transmission of compressive stress to the overriding plate (Lallemand et al., 2005; Liu et al., 2021; Peng et al., 2021), trench‐ward migration of the magmatic arc during the retreat of the flat slab (Wu, Yang, et al., 2019), and development of a prominent, syn‐flat slab magmatic lull (Henderson et al., 1984; Hu & Liu, 2016). Although previous studies have revealed the effect of slab dips on the tectono‐magmatic evolution in normal slab subduction, the effect may be opposite in the circumstances of mid‐ocean ridge subduction.…”

Ongoing Lithospheric Alteration of the North China Craton Revealed by Surface‐Wave Tomography and Geodetic Observations

“…to trigger the reactivation of the NCC (Peng et al, 2021;Zheng et al, 2018;Zhu, Jiang et al, 2012). The thick (>180 km), cold and refractory lithosphere beneath the eastern NCC was replaced by thin (∼80 km) juvenile lithosphere (Menzies et al, 1993;Xu et al, 2004;Zheng et al, 2007).…”

“…A significant effort is dedicated to deciphering the evolution of the NCC, especially its tectonothermal reactivation peaked in the late Mesozoic (Chen et al., 2008; Huang et al., 2009; Xu, 2001; Zheng et al., 2018). The destruction of the NCC is generally attributed to the westward subduction of the Paleo‐Pacific plate according to the first‐order spatial and temporal correspondence between these two events (Chen, 2010; Peng et al., 2021; Zheng et al., 2018). The predominant feature of the NCC is the E‐W contrast in the lithospheric structure, significantly thinning from west to east (Chen, 2010; Guo et al., 2016; Huang et al., 2009).…”