Kazakhstan Orocline bending in response to seamounts subduction

Abstract

Oroclines are map-view deformation of Earth's crust resulting from bending of quasi-linear elements. The Central Asian Orogenic Belt (CAOB) is one of the largest and long-lived accretionary orogens in the world and mainly consists of the Kazakhstan and Tuva-Mongolian oroclines. However, the mechanism of the oroclines is still in debate. Therefore, in this paper, we combine some investigation of high bathymetric relief resistance to subduction, review oroclinal bending models of the Kazakhstan Orocline, and propose a tentative model that involves asymmetric rollback in response to seamounts subduction and accretion, followed by bending associated with the convergence of the Siberian and Tarim cratons. Moreover, the role of pinning due to seamount and ridge subduction is probably more important than the convergence of continents in the CAOB. This model is compatible with the occurrence of seamounts, the spatial migration of intraoceanic arcs, and the development of multiple rollback processes during amalgamation of Eurasia. However, only geochemical and geochronological data will enable definition of the seamounts in CAOB so far, without much matching structural data. So we need more work to understand seamounts subduction and accretion as well as orocline bending in CAOB.

The effect of seamount chain subduction and accretion

“…Recently, based on detailed mapping, field structural geology, and geochemical data, J. E. Zhang et al (2018) proposed that the basement of the Tacheng block was an Early Palaeozoic oceanic plateau (Figure 2b), which collided with the Chingiz arc at Late Ordovician to Late Devonian (Y. C. Chen et al, 2017), and may result in the formation of a new subduction belt behind the accreted plateau (G. X. Yang, 2019). In addition, the oceanic plateau and seamount fragments are widely scattered along the Tangbale, Mayile, and Darbut ophiolitic mélange belts in southern West Junggar, as well as the Kujibai‐Hebukesaier‐Hongguleleng suture zone in the northern West Junggar (Figure 2b; Du et al, 2019; G. X. Yang, Li, Santosh, Yang, et al, 2012; G. X. Yang, Li, Santosh, Yang, Gu, et al, 2012; G. X. Yang et al, 2013, 2015; Y. Q. Yang et al, 2019, 2020).…”

“…But these models above did not address the role of seamount and/or oceanic plateau subduction and accretion. Actually, this might have played a key role in oroclinal bending (Figure 11; Miller et al, 2006; Rosenbaum & Mo, 2011; G. X. Yang, 2019) and resulted in subduction initiation (G. X. Yang et al, 2022).…”

“…At the Late Ordovician, the Tacheng oceanic plateau entered the subduction zone, and collided with the Chingiz arc in the north (Figure 11a; Y. C. Chen et al, 2017), and may have resulted in the formation of a new subduction belt behind the accreted plateau (Figure 11b; G. X. Yang, 2019). This new subduction dipped in the same direction as the original one, namely subduction transference (Stern, 2004).…”