Seismic Structure of the Caroline Plateau‐Yap Trench Collision Zone

Abstract

Collision of oceanic plateaus with trenches has played a key role in the continental growth and plate tectonic reorganizations throughout the Earth's history. However, the understanding of collision between an initially rifted plateau with a trench is still deficient. Here we conduct the first seismic tomography and receiver function analyses in the Yap subduction zone, western Pacific Ocean, where the initially rifted Caroline Plateau is colliding with the Yap Trench. Our results reveal horizontal and overturned slabs south and north of the Sorol Trough, respectively, which may be caused by slab breakoff followed by underplating and eastward mantle flow with ultra‐slow convergence. The distinct slab morphologies could be responsible for the short‐lived arc volcanism (11‐7 Ma), horst‐graben structures, different Bouguer gravity anomalies and stress regimes in the Yap subduction zone. The overturned slab may cause the incoming plateau to be stretched to facilitate the initial plateau subduction.

Detached Pacific Slab Beneath the Philippine Sea Plate and Its Geodynamical Implications

“…These transform and/or strike‐slip faults may contribute to the formation of the detached Pacific slab. Moreover, different subducting angles and rates of the Pacific Plate along different segments of the IBM Trench, the bending and flattening of the subducted Pacific slab in the MTZ, and the subduction of the Ogasawara and Caroline plateaus may have jointly resulted in the slab detachment (e.g., Obayashi et al., 2009; P. Ma et al., 2019; Mason et al., 2010; Fan et al., 2022).…”

“…Seismic tomography is a powerful tool for mapping the subducted slabs in the mantle. Although many tomographic studies have been made, the three‐dimensional (3‐D) P‐wave velocity (Vp) structure of the upper mantle beneath the whole PSP is still not well revealed, because the previous studies mainly focused on local areas, such as the Japan Islands and the Ryukyu arc (e.g., Cao et al., 2014; Fan & Zhao, 2021b; Hasegawa et al., 2013; Huang et al., 2013; Liu & Zhao, 2016; Zhao et al., 1992, 2012), the Philippines (e.g., Fan & Zhao, 2018; Fan et al., 2015, 2016, 2017; Wei et al., 2022), the Taiwan Island (e.g., Fan & Zhao, 2021a; Koulakov et al., 2014; Kuo‐Chen et al., 2012; Lallemand et al., 2001; Toyokuni et al., 2021), and the Yap and Mariana trenches (e.g., Barklage et al., 2015; Fan et al., 2022; Pyle et al., 2010; Qiao et al., 2021). Some researchers have investigated the large‐scale mantle structure beneath East or Southeast Asia (e.g., Chen et al., 2017; Huang & Zhao, 2006; J. Ma et al., 2018, 2019; Toyokuni et al., 2022; van der Hist et al., 1991; Wei et al., 2012, 2015; Zhao et al., 2017) and the global mantle structure (e.g., Amaru, 2007; Fukao & Obayashi, 2013; Li et al., 2008; Lu et al., 2019; Zhao, 2004; Zhao et al., 2013), but these large‐scale Vp models generally have lower resolution than the local Vp models.…”

“…The most conspicuous feature of the PSP is that it is mostly bounded by a series of subduction zones (Figure 1). Its eastern boundary is the Izu‐Bonin‐Mariana‐Yap‐Palau trench system, along which the Pacific and Caroline Sea plates descend into the mantle beneath the PSP (e.g., Fan et al., 2022). Connecting this trench system is the Ayu Trough, which constitutes the PSP southernmost boundary.…”

“…BR, the Benham Rise; HT, the Halmahera Trench; LI, the Luzon Island; MS, the Molucca Sea; OP, the Ogasawara Plateau; PT, the Palau Trench; ST, the Sangihe Trench; TI, the Taiwan Island; UP, the Urdaneta Plateau; YT, the Yap Trench. Huang et al, 2013;Liu & Zhao, 2016;Zhao et al, 1992Zhao et al, , 2012, the Philippines (e.g., Fan & Zhao, 2018;Fan et al, 2015Fan et al, , 2016Fan et al, , 2017Wei et al, 2022), the Taiwan Island (e.g., Fan & Zhao, 2021a;Koulakov et al, 2014;Kuo-Chen et al, 2012;Lallemand et al, 2001;Toyokuni et al, 2021), and the Yap and Mariana trenches (e.g., Barklage et al, 2015;Fan et al, 2022;Pyle et al, 2010;Qiao et al, 2021). Some researchers have investigated the large-scale mantle structure beneath East or Southeast Asia (e.g., Chen et al, 2017;Huang & Zhao, 2006;J.…”

Construction of the Caroline Ridge uppermost basement in the West Pacific: Implications from intrabasement seismic reflectors

“…Before the Caroline Plate formed at ~35 Ma, the proto‐Yap–Mariana Trench formed a continuous subduction system (Hegarty & Weissel, 1988; Fujioka et al, 2002; Gaina & Müller, 2007; Lallemand, 2016; Zhang & Li, 2019; Zhang, Li, et al, 2022). In the Late Oligocene, collision between the buoyant Caroline Ridge with thick crust (Bracey, 1975; Nagihara et al, 1989; Lee, 2004; Gaina & Müller, 2007; Zhang, Dong, Sun, & Zhang, 2021; Fan et al, 2022) and the western boundary of the Caroline Plate led to subduction cessation at the Yap Trench (Hawkins & Batiza, 1977; Fujiwara et al, 2000; Kobayashi, 2004). Volcanism in the Yap arc decreased (Ohara et al, 2002), and the metamorphosed ophiolite obduction ages (Fujioka et al, 1998) and amphibolite age of the Yap arc (Zhang & Zhang, 2020) suggest that the collision process occurred in the Late Oligocene.…”