Kinematic Boundary Conditions Favouring Subduction Initiation at Passive Margins Over Subduction at Mid-oceanic Ridges

We perform numerical modelling to simulate the shortening of an oceanic basin and the adjacent continental margins in order to discuss the relationship between compressional stresses acting on the lithosphere and the time dependent strength of the mid-oceanic ridges within the frame of subduction initiation. We focus on the role of stress regulating mechanisms by testing the stress–strain-rate response to convergence rate, and the thermo-tectonic age of oceanic and continental lithospheres. We find that, upon compression, subduction initiation at passive margin is favoured for thermally thin (Palaeozoic or younger) continental lithospheres (<160 km) over cratons (>180 km), and for oceanic basins younger than 60 Myr (after rifting). The results also highlight the importance of convergence rate that controls stress distribution and magnitudes in the oceanic lithosphere. Slow convergence (<0.9 cm/yr) favours strengthening of the ridge and build-up of stress at the ocean-continent transition allowing for subduction initiation at passive margins over subduction at mid-oceanic ridges. The results allow for identifying geodynamic processes that fit conditions for subduction nucleation at passive margins, which is relevant for the unique case of the Alps. We speculate that the slow Africa–Europe convergence between 130 and 85 Ma contributes to the strengthening of the mid-oceanic ridge, leading to subduction initiation at passive margin 60–70 Myr after rifting and passive margin formation.

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Lateral propagation–induced subduction initiation at passive continental margins controlled by preexisting lithospheric weakness

Science Advances ◽

10.1126/sciadv.aaz1048 ◽

2020 ◽

Vol 6 (10) ◽

pp. eaaz1048 ◽

Cited By ~ 3

Author(s):

Xin Zhou ◽

Zhong-Hai Li ◽

Taras V. Gerya ◽

Robert J. Stern

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Numerical Models ◽

Three Dimensional ◽

Passive Margin ◽

Continental Margins ◽

Subduction Initiation ◽

Passive Margins ◽

The North ◽

Lateral Propagation

Understanding the conditions for forming new subduction zones at passive continental margins is important for understanding plate tectonics and the Wilson cycle. Previous models of subduction initiation (SI) at passive margins generally ignore effects due to the lateral transition from oceanic to continental lithosphere. Here, we use three-dimensional numerical models to study the possibility of propagating convergent plate margins from preexisting intraoceanic subduction zones along passive margins [subduction propagation (SP)]. Three possible regimes are achieved: (i) subducting slab tearing along a STEP fault, (ii) lateral propagation–induced SI at passive margin, and (iii) aborted SI with slab break-off. Passive margin SP requires a significant preexisting lithospheric weakness and a strong slab pull from neighboring subduction zones. The Atlantic passive margin to the north of Lesser Antilles could experience SP if it has a notable lithospheric weakness. In contrast, the Scotia subduction zone in the Southern Atlantic will most likely not propagate laterally.

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Schistes lustrés from Corsica to Hungary : back to the original sediments and tentative dating of partly azoic metasediments

BSGF - Earth Sciences Bulletin ◽

10.2113/174.3.197 ◽

2003 ◽

Vol 174 (3) ◽

pp. 197-209 ◽

Cited By ~ 9

Author(s):

Marcel Lemoine

Keyword(s):

Late Cretaceous ◽

Deep Sea ◽

Black Shales ◽

Continental Margins ◽

Long Time ◽

The Alps ◽

Mass Flow Deposits ◽

Reliable Marker ◽

Early Late

Abstract The Alpine and Corsican Schistes lustrés (SL) are nearly azoic Jurassic-Cretaceous metasediments often associated with ophiolites. They are derived from both the vanished Valais (N-Penninic) and Piemont-Ligurian (S-Penninic) oceans and from their continental margins. Their age is generally poorly known. Because of fossils discovered by Alb. Heim and by S. Franchi at the beginning of the 20th century, they were believed for a long time to be mostly Liassic in age. We know now that the major part of the SL is Cretaceous. Deep-sea sediments, and particularly the SL, are made up of a hemipelagic-pelagic background (HPB) associated with detrital components of local or distant origin. The nature of the HPB, mostly conditioned by Tethyan and worldwide events, is of great help as an at least rough stratigraphic marker ; in contrast, detrital material is not a reliable marker because it may occur at different times in different places. The HPB exhibits several successive, 10 to 40 m.y. long episodes which are either predominantly argillaceous (A) or calcareous (C). During the deposition of the Juras-sic-Cretaceous SL, seven episodes can be distinguished : C1, calcareous Liassic ; A1, marly Upper Liassic ; C2, calcareous latest Liassic and early Dogger ; A2, shaly or radiolaritic late Dogger-early Malm ; C3, calcareous late Malm ; A3 shaly or marly early Cretaceous ; C4 calcareous late Cretaceous. They can be recognized, each one by its prevailing lithology, and all together by their succession in order from C1 to C4. Nearly all of these subdivisions are here and there dated by rare fossils, which allow for a rough dating of the numerous azoic SL series. As they exhibit very different lithologies, from pelagic calcareous oozes to Black Shales and various kinds of flysch and other mass flow deposits, the SL cannot be considered as a specific, well-defined facies : they are not characteristic for a particular stage of the geodynamic evolution of the Alps. Finally, a possible influence of worldwide events is suggested. First, the role of the depth of the CCD, governed by early late Jurassic and early late Cretaceous biotic recoveries. Secondly, the correlation with first order eustatic events : transgressions on platforms seem to be roughly coeval with A episodes in the deep sea, regressions with C episodes.

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Fossil oceanic core complexes in the Alps. New field, geochemical and isotopic constraints from the Tethyan Aiguilles Rouges Ophiolite (Val d’Hérens, Western Alps, Switzerland)

Swiss Journal of Geosciences ◽

10.1186/s00015-020-00380-4 ◽

2021 ◽

Vol 114 (1) ◽

Cited By ~ 2

Author(s):

Thierry Decrausaz ◽

Othmar Müntener ◽

Paola Manzotti ◽

Romain Lafay ◽

Carl Spandler

Keyword(s):

Sedimentary Cover ◽

Oceanic Lithosphere ◽

Western Alps ◽

Continental Margins ◽

Remarkable Feature ◽

Isotopic Signatures ◽

Basement Rocks ◽

The Alps ◽

Slow Spreading

AbstractExhumation of basement rocks on the seafloor is a worldwide feature along passive continental margins and (ultra-) slow-spreading environments, documented by dredging, drilling or direct observations by diving expeditions. Complementary observations from exhumed ophiolites in the Alps allow for a better understanding of the underlying processes. The Aiguilles Rouges ophiolitic units (Val d’Hérens, Switzerland) are composed of kilometre-scale remnants of laterally segmented oceanic lithosphere only weakly affected by Alpine metamorphism (greenschist facies, Raman thermometry on graphite: 370–380 °C) and deformation. Geometries and basement-cover sequences comparable to the ones recognized in actual (ultra-) slow-spreading environments were observed, involving exhumed serpentinized and carbonatized peridotites, gabbros, pillow basalts and tectono-sedimentary cover rocks. One remarkable feature is the presence of a kilometric gabbroic complex displaying preserved magmatic minerals, textures and crosscutting relationships between the host gabbro and intruding diabase, hornblende-bearing dikelets or plagiogranite. The bulk major and trace element chemistry of mafic rocks is typical of N-MORB magmatism (CeN/YbN: 0.42–1.15). This is supported by in-situ isotopic signatures of magmatic zircons (εHf = + 13 ± 0.6) and apatites (εNd = + 8.5 ± 0.8), determined for gabbros and plagiogranites. In-situ U–Pb dating was performed on zircons by laser ablation-ICP-MS, providing ages of 154.9 ± 2.6 Ma and 155.5 ± 2.8 Ma, which are among the youngest for oceanic gabbros in the Alps. Our study suggests that the former Aiguilles Rouges domain was characterized by tectonism and magmatism resembling present-day (ultra-) slow-spreading seafloor. It also suggests that the Tethyan lithosphere is laterally segmented, with punctuated magmatism such as the Aiguilles Rouges gabbros and carbonated ultramafic seafloor covered by basalts and Jurassic tectono-sedimentary deposits.

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Evidence of oceanic plate delamination in the Northern Atlantic

10.21203/rs.3.rs-690433/v1 ◽

2021 ◽

Author(s):

Joao Duarte ◽

Nicolas Riel ◽

Chiara Civiero ◽

Sonia Silva ◽

Filipe Rosas ◽

...

Keyword(s):

Plate Tectonics ◽

Numerical Models ◽

Oceanic Lithosphere ◽

Continental Lithosphere ◽

Subduction Initiation ◽

Passive Margins ◽

Velocity Anomaly ◽

New Class ◽

Lisbon Earthquake ◽

Mountain Belts

Abstract The Earth’s surface is constantly being recycled by plate tectonics. Subduction of oceanic lithosphere and delamination of continental lithosphere constitute the two most important mechanisms by which the Earth’s lithosphere is recycled into the mantle. Delamination or detachment in continental regions typically occurs below mountain belts due to a weight excess of overthickened lithospheric mantle, which detaches from overlying lighter crust, aided by the existence of weak layers within the continental lithosphere. Oceanic lithosphere is classically pictured as a rigid plate with a strong core that does not allow for delamination to occur. Here, we propose that active delamination of oceanic lithosphere occurs offshore Southwest Iberia. The process is assisted by the existence of a lithospheric serpentinized layer that allows the lower part of the lithosphere to decouple from the overlying crust. Tomography images reveal a sub-lithospheric high-velocity anomaly below this region, which we interpret as a delaminating block of old oceanic lithosphere. We present numerical models showing that for a geological setting mimicking offshore Southwest Iberia delamination of oceanic lithosphere is possible and may herald subduction initiation, which is a long-unsolved problem in the theory of plate tectonics. We further propose that such oceanic delamination is responsible for the highest-magnitude earthquakes in Europe, including the M8.5-8.7 Great Lisbon Earthquake of 1755 and the M7.9 San Vincente earthquake of 1969. In particular, our numerical models, in combination with calculations on seismic potential, provide a solution for the instrumentally recorded 1969 event below the flat Horseshoe abyssal plain, away from mapped tectonics faults. Delamination of old oceanic lithosphere near passive margins constitutes a new class of subduction initiation mechanisms, with fundamental implications for the dynamics of the Wilson cycle.

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The effect of magma poor and magma rich rifted margins on continental collision dynamics

10.5194/egusphere-egu21-6052 ◽

2021 ◽

Author(s):

Valeria Turino ◽

Valentina Magni ◽

Hans Jørgen Kjøll ◽

Johannes Jakob

Keyword(s):

Oceanic Lithosphere ◽

Continental Collision ◽

Passive Margin ◽

Collision Dynamics ◽

Large Variability ◽

Passive Margins ◽

Continental Plate ◽

Rifted Margins ◽

Wide Range ◽

Rifted Margin

The transition between continental and oceanic lithosphere in rifted margins can display a wide range of characteristics, which primarily depend on the regional tectonic evolution. Rifted margins form when continents rift apart and are commonly characterized by a thinned transition zone between the continental crust and the oceanic crust. The velocity and duration of the rifting process influence the dimensions and geometry of the passive margin. Rifted (or passive) margins are often subdivided in a magma-rich type and a magma-poor type, where the magma-rich are characterized by large input of mafic melt, derived from the mantle, into the crust. Magma-poor rifted margins on the other hand are characterized by much less magma production during the rifting process. This causes high variability in the geometry and rheology of passive margins.The aim of this work is to understand how different types of passive margins can influence the dynamics of continental collision. We modelled subduction using the finite element code Citcom and to describe the dynamics of continental collision we mainly focused on the time and position of the slab break-off after the collision and on the fate of the passive margin material.We compared these models as a function of various parameters (e.g., margin length, density, and viscosity), in order to understand how the architecture of a passive margin affects the dynamics of continental collision. We find that passive margins have a noticeable impact on subduction, as we observe a large variability in slab break-off times (about 10&#8211;70 Myr after continental collision) and depth (about 200&#8211;450 km). Furthermore, the factor that shows the largest impact on subduction dynamics is the rheology of the passive margin. Our results show that for both magma-poor and magma-rich margins, part of the margin does not subduct but, instead, exhumes and accretes to the overriding plate. Importantly, the amount of accreted material to the overriding plate is much larger when the passive margin is magma-poor compared to the magma-rich case. This is consistent with geological observations that fossil magma-poor passive margins are preserved in many mountain ranges, such as the Alps and the Scandinavian Caledonides, whereas remnants of magma-rich rifted margins are scarce. Because, in our models, the slab break-off occurs inboard of the LCB, magma-rich rifted margin may only be preserved when the density of the LCB is similar to that of the rest of the continental plate. Therefore magma-rich rifted margins are prone to be subducted and recycled into the mantle. Importantly, our results show that&#160;rifted margin type controls the architecture of the subsequent collisional phase of the Wilson cycle.

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Comparing onshore and offshore volumes of large igneous provinces associated with passive continental margins

10.5194/egusphere-egu21-13631 ◽

2021 ◽

Author(s):

Seth Stein ◽

Molly Gallahue ◽

Carol Stein ◽

Tyrone Rooney ◽

Andie Gomez-Patron

Keyword(s):

Passive Margin ◽

Igneous Rocks ◽

Continental Rifting ◽

Large Igneous Provinces ◽

Passive Margins ◽

Igneous Provinces ◽

Euler Pole ◽

Seismic Reflection Profiles ◽

The Relationship ◽

Insight Into

The rifting of continents can lead to the initiation of seafloor spreading and the formation of passive margins. Magma-rich passive margins, which are defined as being underlain by enormous volumes of igneous rocks, are often associated with large igneous provinces (LIPs). However, the relationship between the igneous units found along these magma-rich passive margins, rifting processes, and LIPs is poorly understood.We have developed the VOLMIR (VOLcanic passive Margin Igneous Rocks) dataset to investigate these relationships. VOLMIR is based on seismic reflection profiles in which the volumes and geometries of both shallow seaward dipping reflector (SDR) and deeper high velocity lower crustal (HVLC) units can be measured. We find a relatively consistent ratio of SDR to HVLC volumes, with SDR volumes about one third that of HVLC. This consistency suggests that the units are related during formation and may be used to provide insight into how such units form during continental rifting and breakup. Presumably, as magmas rise and erupt to the surface to form SDRs, the remaining high-density residuum or cumulate becomes the HVLC. The volumes of SDR units are moderately positively correlated with distance from the Euler pole, and weakly negatively correlated with distance from the nearest hotspot, suggesting that lithospheric processes play more of a role in late-stage continental rifting and breakup than hotspot/mantle plume processes.The Mid- and South Atlantic Ocean breakups, and the resulting offshore volcanic passive margins, are temporally and spatially associated with the Central Atlantic Magmatic Province (CAMP) and Parana&#769;-Etendeka LIP. Using VOLMIR, we estimate the amount of igneous material in the offshore volcanic passive and compare it to estimates for the adjacent on-land LIPs. The results indicate that a significant volume of volcanics exist in the offshore passive margins, increasing the inferred amount of volcanic output associated with the LIPs. Further studies will provide insight into the relationship between offshore passive margins and on-land LIPs, and perhaps provide further understanding on the role of magmatism in rifting processes.

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Birthdate for the Coronation paleocean: age of initial rifting in Wopmay orogen, CanadaThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

Canadian Journal of Earth Sciences ◽

10.1139/e10-038 ◽

2011 ◽

Vol 48 (2) ◽

pp. 281-293 ◽

Cited By ~ 28

Author(s):

Paul F. Hoffman ◽

Samuel A. Bowring ◽

Robert Buchwaldt ◽

Robert S. Hildebrand

Keyword(s):

Detrital Zircon ◽

Hanging Wall ◽

Passive Margin ◽

Pyroclastic Rock ◽

Continental Margins ◽

Ionization Mass ◽

Slave Craton ◽

Passive Margins ◽

Igneous Zircon ◽

The Mean

The 1.9 Ga Coronation “geosyncline” to the west of Slave craton was among the first Precambrian continental margins to be identified, but its duration as a passive margin has long been uncertain. We report a new U–Pb (isotope dilution – thermal ionization mass spectrometry (ID–TIMS)) 207Pb/206Pb date of 2014.32 ± 0.89 Ma for zircons from a felsic pyroclastic rock at the top of the Vaillant basalt, which underlies the passive margin sequence (Epworth Group) at the allochthonous continental slope. A sandstone tongue within the basalt yields Paleoproterozoic (mostly synvolcanic) and Mesoarchean detrital zircon dates, of which the latter are compatible with derivation from the Slave craton. In contrast, detrital zircon grains from the Zephyr arkose in the accreted Hottah terrane have Paleoproterozoic and Neoarchean dates. The latter cluster tightly at 2576 Ma, indistinguishable from igneous zircon dates reported here from the Badlands granite, which is faulted against the Vaillant basalt and underlying Drill arkose. We interpret these data to indicate that Badlands granite belongs to the hanging wall of the collisional geosuture between Hottah terrane and the Slave margin, represented by the Drill–Vaillant rift assemblage. If 2014.32 ± 0.89 Ma dates the rift-to-drift transition and 1882.50 ± 0.95 Ma (revised from 1882 ± 4 Ma) the arrival of the passive margin at the trench bordering the Hottah terrane, the duration of the Coronation passive margin was ∼132 million years, close to the mean age of extinct Phanerozoic passive margins of ∼134 million years (see Bradley 2008).

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Subduction initiation and subsequent burial-exhumation of (ultra)high-pressure rock

10.5194/egusphere-egu21-10097 ◽

2021 ◽

Author(s):

Stefan Markus Schmalholz ◽

Lorenzo Candioti ◽

Joshua Vaughan-Hammon ◽

Thibault Duretz

Keyword(s):

High Pressure ◽

Subduction Zones ◽

Conceptual Models ◽

Passive Margin ◽

Far Field ◽

Subduction Initiation ◽

Ultra High Pressure ◽

Orogenic Wedge ◽

The Alps ◽

Marine Basin

Subduction zones are one of the main features of plate tectonics, they are essential for geochemical cycling and are often a key player during mountain building. However, several processes related to subduction zones remain elusive, such as the initiation of subduction or the exhumation of (ultra)high-pressure rocks.Collision orogens, such as the European Alps or Himalayas, provide valuable insight into long-term subduction zone processes and the larger geodynamic cycles of plate extension and subsequent convergence. For the Alps, geological reconstructions suggest a horizontally forced subduction initiation caused by the onset of convergence between the Adriatic and European plates. During Alpine orogeny, the Piemont-Liguria basin and the European passive magma-poor margin (including the Brian&#231;onnais domain) were subducted below Adria. The petrological rock record indicates burial and subsequent exhumation of both continental and oceanic crustal rocks that were exposed to (ultra)high-pressure metamorphic conditions during their Alpine burial-exhumation cycle. Moreover, estimates of exhumation velocities yield magnitudes in the range of several mm/yr to several cm/yr. However, published estimates of exhumation velocities, ages of peak metamorphic conditions and estimates for peak pressure and peak temperature vary partly significantly, even for the same tectonic unit. Consequently, many, partly significantly, contrasting conceptual models for subduction initiation (convergence versus buoyancy driven) or rock exhumation (channel-flow, diapirism, episodic regional extension, erosion etc.) have been proposed for the Alps.&#160;Complementary to the data-driven approach, mathematical models of the lithosphere and upper mantle system are useful tools to investigate geodynamic processes. These mathematical models integrate observational and experimental data with the fundamental laws of physics (e.g. conservation of mass, momentum and energy) and are useful to test conceptual models of subduction initiation and rock exhumation. Here, we present numerical solutions of two-dimensional petrological-thermo-mechanical models. The initial model configuration consists of an isostatically and thermally equilibrated lithosphere, which includes mechanical heterogeneities in the form of elliptical regions with different effective viscosity. We model a continuous geodynamic cycle of subsequent extension, no far-field deformation and convergence. During extension, the continental crust is necked, separated and mantle is exhumed, forming a marine basin bounded by passive margins. During the subsequent stage with no far-field deformation, the thermal field of the lithosphere is re-equilibrated above a convecting mantle. During convergence, subduction is initiated at one passive margin and the mantle lithosphere below the marine basin as well as the other passive margin are subducted. During progressive subduction, parts of the subducted continental upper crust are sheared-off the subducting plate and are exhumed to the surface, ultimately forming an orogenic wedge. For the convergence, we test the impact of serpentinites at the top of the exhumed mantle on orogenic wedge formation. We compare the model results with observational and experimental constraints, discuss the involved processes and driving forces and propose a model for subduction initiation and (ultra)high-pressure rock exhumation for the Alps.

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Tectonic and geomorphic controls on the distribution of submarine landslides across active and passive margins, eastern New Zealand

Geological Society London Special Publications ◽

10.1144/sp500-2019-165 ◽

2019 ◽

Vol 500 (1) ◽

pp. 477-494 ◽

Cited By ~ 2

Author(s):

S. J. Watson ◽

J. J. Mountjoy ◽

G. J. Crutchley

Keyword(s):

New Zealand ◽

Slope Failure ◽

Submarine Landslide ◽

Passive Margin ◽

Continental Margins ◽

Submarine Landslides ◽

Mass Wasting ◽

Active Margin ◽

Passive Margins ◽

Marine Habitats

AbstractSubmarine landslides occur on continental margins globally and can have devastating consequences for marine habitats, offshore infrastructure and coastal communities due to potential tsunamigenesis. Therefore, understanding landslide magnitude and distribution is central to marine and coastal hazard planning.We present the first submarine landslide database for the eastern margin of New Zealand comprising >2200 landslides occurring in water depths from c. 300–4000 m. Landslides are more prevalent and, on average, larger on the active margin compared with the passive margin. We attribute higher concentrations of landslides on the active margin to tectonic processes including uplift and oversteepening, faulting and seamount subduction. Submarine landslide scars are concentrated around canyon systems and close to canyon thalwegs. This suggests that not only does mass wasting play a major role in canyon evolution, but also that canyon-forming processes may provide preconditioning factors for slope failure.Results of this study offer unique insights into the spatial distribution, magnitude and morphology of submarine landslides across different geological settings, providing a better understanding of the causative factors for mass wasting in New Zealand and around the world.

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Forced subduction initiation at passive continental margins: Numerical modeling

10.5194/egusphere-egu2020-1761 ◽

2020 ◽

Author(s):

Xinyi Zhong ◽

Zhong-Hai Li

Keyword(s):

Subduction Zones ◽

Plate Tectonics ◽

Numerical Models ◽

Oceanic Lithosphere ◽

Ocean Basin ◽

Passive Margin ◽

Complex Case ◽

Subduction Initiation ◽

Boundary Force ◽

Time Required

Subduction initiation (SI) induced by the tectonic boundary force may play a significant role in the Wilson cycle. In the previous analog and numerical models, the constant convergent velocity is generally applied, which may lead to large boundary forces for SI. In this study, we begin with testing the simple case of SI at passive margin with constant convergent force. The results indicate that the boundary force required to trigger the SI at passive margin with a thin and young oceanic lithosphere is much lower than that with a thick and old one. It is consistent with the multiple Cenozoic subduction zones in the Southwest Pacific, which are young ocean basin within 40 Ma and compressed by the India-Australia plate. Furthermore, we extended our model to explore a more complex case, forced SI during the collision-induced subduction transference, which is critical for Tethyan evolution. Both collision and SI processes are integrated in the numerical models. The results indicate that the forced convergence, rather than pure free subduction, is required to trigger and sustain the SI in the neighboring passive margin after collision of terrane. In addition, a weak passive margin can significantly promote the occurrence of subduction initiation, by decreasing required boundary force within reasonable range of plate tectonics. However, the lengths of subducted oceanic slab and accreting terrane play secondary roles in the occurrence of SI after collision. Under the favorable conditions of collision-induced subduction transference, the time required for subduction initiation after collision is generally within 10 Myrs, which is consistent with the general geological records of Neo-Tethys. In contrast, both Atlantic passive margin and Indian passive margin are old and stable with absence of subduction initiation in the present, which remains an open question.

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