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The subduction process of flat-slab subduction (M-10 of 30-km-thick and 200-km-long). (a)-(c), the evolution of composition, density and viscosity of M-10, respectively. (a2')-(a6') is the enlarged display of the black frame area in a2-a6, respectively. Only eclogite and partial melting are shown, no other composition information is shown. The red and black areas indicate partial melting and eclogite, respectively.
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Oceanic plateaus (or aseismic ridges) can be either subducted into the deep mantle, or accreted onto the overriding plate. Furthermore, some oceanic plateaus can change subduction mode from steep to flat-slab subduction. What factors control the fate of oceanic plateaus during subduction remain enigmatic. Here, we investigate the controls on these...
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... . 5 shows the evolution of a 30-km thick and 200-km long oceanic plateau (M-10 in Fig. 3). Similar to model M-15, the subduction begins along the weak zone with a shallow angle (Fig. 5a1). The slab steepens due to the continued convergence and eclogitization ( Fig. 5a2 ), and the break-off occurs at a depth of ∼250 km at the junction ...
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... (Fig. 6a4). At this stage, partial melting moved away from the old trench, that is, partial melting of the crust also occurred in the newly created subduction zone (Figs 6a4 and a4'). With the eclogitization of the plateau crust, the accretionary plateau frontal plate rolled back, causing the trench to retreat, resulting in decompression melting (Fig. ...
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... distinct magma effects associated with the oceanic plateaus' subduction. In the steep subduction model (e.g. M-15), partial melting of the oceanic crust occurs locally near the trench (Fig. 4). In the flat-slab subduction process (e.g. M-10), partial melting migrates inland and then migrates toward the trench again due to the rollback of the slab (Fig. 5). For the collision and accretion model (e.g. M-28), due to the formation of the new subduction zone, the partial melting of the crust will migrate away from the trench, forming two melting zones along the old and new subduction zones (Fig. 6a4). As the trench retreated, decompression melting followed (Fig. 6a5). It should be noted that ...
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... again due to the rollback of the slab (Fig. 5). For the collision and accretion model (e.g. M-28), due to the formation of the new subduction zone, the partial melting of the crust will migrate away from the trench, forming two melting zones along the old and new subduction zones (Fig. 6a4). As the trench retreated, decompression melting followed (Fig. 6a5). It should be noted that not all accretionary models will form new subduction zones (Fig. S5, Supporting Information). For example, in M-6, only the plateau crust accretes on the continental margin owing to its small length (100 km) and the continuous compression, and the partial melting process is similar to the process in steep ...
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... due to the formation of the new subduction zone, the partial melting of the crust will migrate away from the trench, forming two melting zones along the old and new subduction zones (Fig. 6a4). As the trench retreated, decompression melting followed (Fig. 6a5). It should be noted that not all accretionary models will form new subduction zones (Fig. S5, Supporting Information). For example, in M-6, only the plateau crust accretes on the continental margin owing to its small length (100 km) and the continuous compression, and the partial melting process is similar to the process in steep subduction (Fig. S6, Supporting ...
Citations
... Accretion and subduction zone jumps are impacted by the width and rheological structure of allochthonous terranes, the thickness of the crust, convergence rates, boundary convergence forces, mantle convection, pre-existing weak zones, rheological strength and the thermal structure of passive continental margins, and the geometry of subduction zones (e.g., Cloos, 1993;Nikolaeva et al., 2010Nikolaeva et al., , 2011Marques et al., 2013Marques et al., , 2014Buiter, 2012, 2014;Moresi et al., 2014;Vogt and Gerya, 2014;Leng and Gurnis, 2015;Wan et al., 2019;Kiss et al., 2020;Gün et al., 2021;Yan et al., 2021Yan et al., , 2022Zhong and Li, 2022). However, past studies only considered the dynamics of continental accretion (e.g., Moresi et al., 2014), the subduction initiation of the passive continental margin without the collision process (e.g., Marques et al., 2013Marques et al., , 2014, or a single phase of subduction zone jump (e.g., Yan et al., 2021). ...
... In this study, based on our previous model of a single subduction zone jump (Yan et al., , 2022, we designed new numerical models to explore the dynamics of successive accretions and multiple episodes of subduction initiation induced by future allochthonous terranes. We numerically investigated the end-member case where the multiple collisions of future allochthonous terranes onto the continental margin lead to outward multiple subduction zone jumps, focusing on the multiple collisions and subduction process and the factors controlling the polarity of subduction initiation and the jumping time. ...
... Here, we systematically test the convergence rate (Fig. 6A) and the properties of future allochthonous terranes (width and depletion degree of the mantle; Fig. 6B) because the plate convergence rate has an important influence on the subduction zone (e.g., Lallemand et al., 2005;Yan et al., 2022), and different oceanic plateaus can reorganize subduction zones . All of the models are compared to reference Model 1, and the results are summarized in Figure 6. ...
The accretion of future allochthonous terranes (e.g., microcontinents or oceanic plateaus) onto the southern margin of Asia occurred repeatedly during the evolution and closure of the Tethyan oceanic realm, but the specific geodynamic processes of this protracted convergence, successive accretion, and subduction zone initiation remain largely unknown. Here, we use numerical models to better understand the dynamics that govern multiple terrane accretions and the polarity of new subduction zone initiation. Our results show that the sediments surrounding the future terranes and the structural complexity of the overriding plate are important factors that affect accretion of multiple plates and guide subduction polarity. Wide (≥400 km) and buoyant terranes with sediments behind them and fast continental plate motions are favorable for multiple unidirectional subduction zone jumps, which are also referred to as subduction zone transference, and successive terrane-accretion events. The jumping times (∼3−20+ m.y.) are mainly determined by the convergence rates and rheology of the overriding complex plate with preceding terrane collisions, which increase with slower convergence rates and/or a greater number of preceding terrane collisions. Our work provides new insights into the key geodynamic conditions governing multiple subduction zone jumps induced by successive accretion and discusses Tethyan evolution at a macro level. More than 50 m.y. after India-Asia collision, subduction has yet to initiate along the southern Indian plate, which may be the joint result of slower plate convergence and partitioned deformation across southern Asia.
... Previous researchers have conducted extensive studies on the dynamics of subduction transference and subduction polarity reversal (Almeida et al., 2022;Liu et al., 2021;Riel et al., 2023;Schellart et al., 2023;Sun et al., 2021;Yang et al., 2022a). The studies of subduction transference mainly focus on the continental margin, and they emphasize the impact of eclogitization, size, thickness, and rheology of an oceanic plateau on collision and accretion processes (Tao et al., 2020;Tetreault and Buiter, 2012;Vogt and Gerya, 2014;Yan et al., 2021;Yan et al., 2022). Arrial and Billen (2013) suggested that the eclogitization of the oceanic plateau promotes its subduction. ...
... Vogt and Gerya (2014) further highlighted the importance of the thermal structure of the subducting plate and oceanic plateau. Yan et al. (2022) suggested that an intermediate-size oceanic plateau will result in frontal slab breakoff and subsequent flat subduction. In contrast, a thick plateau tends to accrete to the continental margin or generate a new subduction zone behind the oceanic plateau if it is sufficiently weak (Tao et al., 2020). ...
... The model results can be categorized into three modes: continuous subduction, subduction transference, and subduction polarity reversal. A relatively thin (≤20 km) and/or heavy oceanic plateau favors continuous subduction, which reinforces the earlier research findings (Arrial and Billen, 2013;Yan et al., 2022). SI is more likely to occur with oceanic plateaus possessing a substantial crust thickness, which renders them susceptible to accretionary processes. ...
... We posit that even though the previous hot material upwelling in the northern region might not have caused extensive surface volcanism, it still had a considerable impact on the uppermost mantle. A new geodynamic simulation study also validates this kind of retreat model of flat-slab subduction (Yan et al., 2022). ...
Plain Language Summary
The collision and subduction of the Cocos and North American plates created a complex geological structure in southern Mexico. Although some scholars proposed that there are some tears in the subducted Cocos slab based on the research of seismic parameters, the support of seismic tomography research for tear models is insufficient. Here, we applied a unique Pn tomography method and obtained the first Pn velocity and anisotropy model of the uppermost mantle in southern Mexico. The study clarified the mid‐oceanic ridge‐perpendicular anisotropy of the Cocos oceanic plate and the trench‐parallel anisotropy beneath the subduction arc. The spatial variations in Pn velocity and anisotropic structure in southern Mexico provide new seismological constraints on the tears of the subducted Cocos plate corresponding to fracture zones. The observed low Pn velocity beneath the Trans‐Mexican Volcanic Belt and the northern area and the trench‐perpendicular anisotropy support the retreat model of the Central Cocos plate. Our study provides a new and reliable tomography basis for a complicated subduction dynamics process in the southern Mexico subduction zone and provides new constraints for a slab‐tearing model corresponding to the fracture zones and the slab retreat model of the Central Cocos plate.
... Modeling studies have shown that periodic shallowing and steepening of slab dips during long-term subduction (Guillaume et al., 2009;Yan et al., 2022). Slab shallowing subduction typically produce strong compression and (Floyd & Leveridge, 1987), (b) La/Sc-Co/Th plot (Gu et al., 2002), (c) K 2 O/Na 2 O-SiO 2 plot (Roser & Korsch, 1986), (d) La-Th-Sc plot, (e) Th-Sc-Zr/10 plot (Bhatia & Crook, 1986). ...
The Mesozoic subduction history of the Paleo‐Pacific plate below the East Asian margin remains contentious, in part because the southern part is poorly understood. To address this, we conducted a sediment provenance study to constrain Mesozoic subduction history below West Sarawak, Borneo. A combination of detrital zircon U‐Pb geochronology, heavy minerals, trace element, and bulk rock Nd isotope data were used to identify the tectonic events. The overall maturity of mineral assemblages, dominantly felsic sources, abundant Precambrian‐aged zircons, and low εNd(0) values (average −13.07) seen in Late Triassic sedimentary rocks suggest a period of inactive subduction near Borneo. Slab shallowing subduction occurred between 200 and 170 Ma based on subdued magmatism and tectonic compression across West Sarawak. From c. 170 to 70 Ma there was widespread magmatism and we interpret the Paleo‐Pacific slab steepened. Collectively, we show the Paleo‐Pacific plate subduction had variable slab dip histories in Borneo.
Flat subduction can significantly influence the distribution of volcanism, stress state, and surface topography of the overriding plate. However, the mechanisms for inducing flat subduction remain controversial. Previous two-dimensional (2-D) numerical models and laboratory analogue models suggested that a buoyant impactor (aseismic ridge, oceanic plateau, or the like) may induce flat subduction. However, three-dimensional (3-D) systematic studies on the relationship between flat subduction and buoyant blocks are still lacking. Here, we use a 3-D numerical model to investigate the influence of the aseismic ridge, especially its width (which is difficult to consider in 2-D numerical models), on the formation of flat subduction. Our model results suggest that the aseismic ridge needs to be wide and thick enough to induce flat subduction, a condition that is difficult to satisfy on the Earth. We also find that the subduction of an aseismic ridge parallel to the trench or a double aseismic ridge normal to the trench has a similar effect on super-wide aseismic ridge subduction in terms of causing flat subduction, which can explain the flat subduction observed beneath regions such as Chile and Peru.
