scholarly journals Subduction initiation along the inherited weakness zone at the edge of a slab: Insights from numerical models

2011 ◽  
Vol 184 (3) ◽  
pp. 991-1008 ◽  
Author(s):  
Marzieh Baes ◽  
Rob Govers ◽  
Rinus Wortel
Keyword(s):  
Numerical Models ◽  
Subduction Initiation ◽  
Weakness Zone

scholarly journals Impact of upper mantle convection on lithosphere hyperextension and subsequent horizontally forced subduction initiation

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2327-2357
Author(s):  
Lorenzo G. Candioti ◽  
Stefan M. Schmalholz ◽  
Thibault Duretz
Keyword(s):  
Upper Mantle ◽  
Mantle Convection ◽  
Driving Forces ◽  
Numerical Models ◽  
Passive Margin ◽  
Continuous Simulation ◽  
Subduction Initiation ◽  
Lithosphere Dynamics ◽  
The Impact

Abstract. Many plate tectonic processes, such as subduction initiation, are embedded in long-term (>100 Myr) geodynamic cycles often involving subsequent phases of extension, cooling without plate deformation and convergence. However, the impact of upper mantle convection on lithosphere dynamics during such long-term cycles is still poorly understood. We have designed two-dimensional upper-mantle-scale (down to a depth of 660 km) thermo-mechanical numerical models of coupled lithosphere–mantle deformation. We consider visco–elasto–plastic deformation including a combination of diffusion, dislocation and Peierls creep law mechanisms. Mantle densities are calculated from petrological phase diagrams (Perple_X) for a Hawaiian pyrolite. Our models exhibit realistic Rayleigh numbers between 106 and 107, and the model temperature, density and viscosity structures agree with geological and geophysical data and observations. We tested the impact of the viscosity structure in the asthenosphere on upper mantle convection and lithosphere dynamics. We also compare models in which mantle convection is explicitly modelled with models in which convection is parameterized by Nusselt number scaling of the mantle thermal conductivity. Further, we quantified the plate driving forces necessary for subduction initiation in 2D thermo-mechanical models of coupled lithosphere–mantle deformation. Our model generates a 120 Myr long geodynamic cycle of subsequent extension (30 Myr), cooling (70 Myr) and convergence (20 Myr) coupled to upper mantle convection in a single and continuous simulation. Fundamental features such as the formation of hyperextended margins, upper mantle convective flow and subduction initiation are captured by the simulations presented here. Compared to a strong asthenosphere, a weak asthenosphere leads to the following differences: smaller value of plate driving forces necessary for subduction initiation (15 TN m−1 instead of 22 TN m−1) and locally larger suction forces. The latter assists in establishing single-slab subduction rather than double-slab subduction. Subduction initiation is horizontally forced, occurs at the transition from the exhumed mantle to the hyperextended passive margin and is caused by thermal softening. Spontaneous subduction initiation due to negative buoyancy of the 400 km wide, cooled, exhumed mantle is not observed after 100 Myr in model history. Our models indicate that long-term lithosphere dynamics can be strongly impacted by sub-lithosphere dynamics. The first-order processes in the simulated geodynamic cycle are applicable to orogenies that resulted from the opening and closure of embryonic oceans bounded by magma-poor hyperextended rifted margins, which might have been the case for the Alpine orogeny.

scholarly journals Subduction Initiation by Plume‐Plateau Interaction: Insights From Numerical Models

2020 ◽  
Vol 21 (8) ◽  
Author(s):  
Marzieh Baes ◽  
Stephan V. Sobolev ◽  
Taras Gerya ◽  
Sascha Brune
Keyword(s):  
Numerical Models ◽  
Subduction Initiation

scholarly journals Evidence of oceanic plate delamination in the Northern Atlantic

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.

Forced subduction initiation at passive continental margins: Numerical modeling

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

<p>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.</p>

Vertically Driven Dynamics and Magmatism of Rapid Subduction Initiation in the Western Pacific

2020 ◽  
Author(s):  
Ben Maunder ◽  
Saskia Goes ◽  
Julie Prytulak ◽  
Mark Reagan
Keyword(s):  
Plate Tectonics ◽  
Numerical Models ◽  
Plate Boundaries ◽  
Temporal And Spatial Distribution ◽  
Subduction Initiation ◽  
Primary Driver ◽  
International Ocean Discovery Program ◽  
Subduction System ◽  
The Western Pacific

<p><strong>Plate tectonics requires the formation of plate boundaries. Particularly important is the enigmatic initiation of subduction: the sliding of one plate below the other, and the primary driver of plate tectonics. A continuous, in situ record of subduction initiation was recovered by the International Ocean Discovery Program Expedition 352, which drilled a segment of the fore-arc of the Izu-Bonin-Mariana subduction system, revealing a distinct magmatic progression with a rapid timescale (</strong><strong>approximately 1 </strong><strong>million years). Here, using numerical models, we demonstrate that these observations cannot be produced by previously proposed horizontal external forcing. Instead a geodynamic evolution that is dominated by internal, vertical forces produces both the temporal and spatial distribution of magmatic products, and progresses to self-sustained subduction. Such a primarily internally driven initiation event is necessarily whole-plate scale and the rock sequence generated (also found along the Tethyan margin) may be considered as a smoking gun for this type of event. </strong></p>

Role of grain size reduction in formation and inversion of oceanic detachment faults

2020 ◽  
Author(s):  
Mingqi Liu ◽  
Taras Gerya ◽  
David Bercovici
Keyword(s):  
Grain Size ◽  
Numerical Models ◽  
Thermal Structure ◽  
Mantle Peridotite ◽  
Spreading Rate ◽  
Size Reduction ◽  
Dislocation Creep ◽  
Subduction Initiation ◽  
Detachment Faults ◽  
Oceanic Detachment Fault

<p>Oceanic detachment faults are large and long-lived (1-2 Myr), forming at slow- and ultraslow- mid-ocean ridges. They can expose lower crustal gabbroic rocks and mantle peridotite in the seafloor, recognized as oceanic core complexes (OCCs). Mechanical models proposed that detachment faults originate at high angle and, as fault offset increases, are rotated flexurally to an inactive low-angle configuration. Previous studies showed that long-lived detachment faults need a rheological boundary for the offset: (1) an alteration front; (2) the brittle-plastic transition (BPT); (3) the boundary between gabbro intrusions and weakened hydrated peridotite; or (4) low magma supply.  In order to better understand the rheological behavior of oceanic detachments, we investigate numerically potential effects of ductile weakening controlled by grain size reduction on the oceanic detachment faults formation as well as on their subsequent inversion during the Wilson cycle. We employ 3D thermomechanical numerical models with a composite rheology consisting of diffusion and dislocation creep. In our model, oceanic crust deforms in a brittle manner and its strength is controlled by fracture-related strain weakening and healing. In contrast, the lithospheric mantle deforms according to the dry olivine flow law, as a mixture of grain size-dependent diffusion and dislocation creep. Numerical results show that ductile weakening induced by grain size reduction could indeed notably influence both the style of detachment faulting and the fault dipping angles in the depth of the BPT. Grain size has a great effect on the offset of detachment faults and the formation of megamullions and controls the place of new subduction initiation below the BPT. We systematically investigate the influence of the thermal structure, initial grain size and spreading rate on the characteristic oceanic detachment fault pattern. In addition, we also study effects of these parameters on the final inversion of detachment faults during induced intra-oceanic subduction initiation.</p>

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

2020 ◽  
Vol 6 (10) ◽  
pp. eaaz1048 ◽  
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.

scholarly journals Differentiating induced versus spontaneous subduction initiation using thermomechanical models and metamorphic soles

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xin Zhou ◽  
Ikuko Wada
Keyword(s):  
High Temperature ◽  
Plate Tectonics ◽  
Numerical Models ◽  
Critical Role ◽  
Slab Surface ◽  
Subduction Initiation ◽  
Temperature Conditions ◽  
Wide Range ◽  
Parameter Values

AbstractDespite the critical role of subduction in plate tectonics, the dynamics of its initiation remains unclear. High-temperature low-pressure metamorphic soles are vestiges of subduction initiation, providing records of the pressure and temperature conditions along the subducting slab surface during subduction initiation that can possibly differentiate the two end-member subduction initiation modes: spontaneous and induced. Here, using numerical models, we show that the slab surface temperature reaches 800–900 °C at ~1 GPa over a wide range of parameter values for spontaneous subduction initiation whereas for induced subduction initiation, such conditions can be reached only if the age of the overriding plate is <5 Ma. These modeling results indicate that spontaneous subduction initiation would be more favorable for creating high-temperature conditions. However, the synthesis of our modeling results and geological observations indicate that the majority of the metamorphic soles likely formed during induced subduction initiation that involved a young overriding plate.

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