Triggering of episodic back-arc extensions in the northeast Asian continental margin by deep mantle flow

Abstract

Back-arc extension has been well documented in subduction plate tectonic regimes. However, the reasons why back-arc extensions are associated with some subduction systems but not others have remained elusive. Here, spatio-temporal variations in the composition of Cenozoic basalts in the northeast Asian continental margin are used to constrain the mechanism for episodic back-arc extensions. Using geochemical data sensitive to tectonic affinity, we show that typical volcanic arc compositions are located in the eastern margin of northeast Asia, whereas coeval intraplate volcanic compositions are located in the western part of northeast Asia, and that the intraplate and arc volcanism exhibit two eastward shifts, from 52 Ma to 33 Ma and from 33 Ma to 21 Ma. Intraplate basalts dated at ca. 11 Ma display a weak, arc-like geochemical signature, which suggests that the upwelling of asthenospheric mantle resulted in the remelting of previously melt-extracted lithospheric mantle modified by slab-derived fluids and the cessation of back-arc extensions. Thus, we propose that the eastward mantle flow resulted in eastward shifts of back-arc extensions that led to the development of extensive Cenozoic arc and intraplate volcanism in the northeast Asian continental margin.

Variable plate kinematics promotes changes in back-arc deformation regime along the north-eastern Eurasia plate boundary

“…In this time span of 15 Ma the lithosphere within the basin reached the minimum in thickness ( 10 km). This is in accordance with 28 , that pointed how the eastward motion of the mantle flow in the area resulted in the first eastward shift of the back-arc extensions in north-east Asia between 52 Ma and 33 Ma. This main opening phase of the basin coincides with the only episode of lowering of the Pacific plate velocity in our model.…”

“…Our models include the Pacific plate motion changes 45 , computed along the profile reported in Figures 1 and 2 , a Low-Velocity Zone (LVZ 14 , 18 , 22 , 46 – 53 ), and the mantle flow 22 . This latter is also based on geochemical evidence in the composition of Cenozoic basalts in the area, revealing an eastward shift of the intraplate and arc volcanism through time during the Eocene-Early Miocene 28 , so that an eastward mantle flow needs to be addressed as the primary cause of this eastward shift. Furthermore, our approach is similar to the one by 22 , in which the westward lithospheric drift (or relative eastward mantle wind) is included in the model 54 , 55 .…”

“…Several basins developed during the Cenozoic (Fig. 1 ), such as the Kuril Basin, the Japan Sea, the East China Sea Shelf, the Yellow Sea, and the Bohai Basin, that were interested by phases of both extension and compression 25 – 28 . For instance, the Japan Sea and the Kuril Basin provide current evolving examples of back-arc basins which opened within a continental plate during the Late Eocene-Miocene.…”

Arc Magmatism Controlled by Switches in Tectonic Style: Insights From the NE Asian Margin in the Cretaceous

“…The NE Asian continental margin has been an accretionary orogen since the Mesozoic (Sengör & Natal'in, 1996), represented by episodic back‐arc extension and intervening compression (Dong et al., 2023). During the Cretaceous, arc magmas were generated in the Sikhote‐Alin orogenic belt in the Russian Far East (Jahn et al., 2015), whereas non‐marine basins were developed in the back‐arc region in NE China (Figure 1a) (P.‐J.…”

Geochemistry of apatites from pre–shield and post–shield basalts and their petrogenetic implications: A case study of the Naitoushan basalt and Heishigou dike in the Changbaishan Tianchi volcano, NE China

“…In the last ten years, seismic and three-dimensional magnetotelluric imaging has identi ed that the CTV is located above the 500 km deep stagnant plate of the western subduction Paci c plate (Yang et al, 2021;Song et al, 2023). Three geodynamic mechanisms have been proposed to explain the large-scale basaltic magma eruption in the CVF: upwelling mantle plume (Chen et al, 2007), intraplate continental rifting (Gilder et al, 1991;Dong et al, 2023) and Paci c plate subduction (Zhang et al, 2018). More studies on volcanism focus on the Millennium eruption (ME) (Zou et al, 2014;Pan et al, 2020), and minimal attention is given to the chronology, single mineral geochemistry and related magmatic stages or genesis of basalts in the CVF.…”