Subduction of oceanic lithosphere has been proposed as the main driving mechanism for plate tectonics for decades and it represents a key process for the geochemical cycles on Earth. However, the physical processes and melting that occur as the subduction zone began foundering and evolved to reach a mature stage is still debated. The Izu-Bonin-Mariana (IBM) intra-oceanic subduction zone, that represents the boundary between the Pacific Plate and the Philippine Sea, is an ideal natural laboratory to study subduction zone processes from their inception to their stabilization. The rock record produced in IBM reveals a rapid compositional variability in slab-fluid tracers as well as in mantle depletion-enrichment over a short timescale (within 1 to 5 Ma of subduction inception). Despite this geochemical evolution, it is still highly debated whether IBM initiated as a forced or spontaneous subduction zone, i.e. induced by or in the absence of horizontal forcing, respectively.

Here, we conducted 2D high-resolution petrological-thermomechanical subduction models that include spontaneous deformation, erosion, sedimentation and slab dehydration processes, as well as melting, assuming a visco-plastic rheology using the i2VIS code. We aimed to model the initiation and the early stage of IBM with ultra-low horizontal forcing and inception triggered by transform collapse. Our new numerical model proposes a viable scenario for the transition from juvenile to mature subduction zone. This evolution includes initiation by gravitational collapse of the slab and the development of a near-trench spreading, the gradual build-up of a return flow of asthenospheric mantle and the progressive maturation of the volcanic arc. Our numerical results of mantle depletion within the mantle wedge and the overall subduction history of IBM are compared further with seismological and geochemical evidences.

How to cite: Ritter, S., Balázs, A., Ribeiro, J., and Gerya, T.: Magmatic Fingerprints of Subduction Initiation and Mature Subduction of the Izu-Bonin-Mariana Subduction Zone: Numerical Modelling and Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2071, https://doi.org/10.5194/egusphere-egu23-2071, 2023.

Early Cretaceous Nidar Ophiolite Complex (NOC, eastern Ladakh) is associated with the north-dipping supra-subduction of the Neo-Tethyan Ocean along the Indus suture zone. The supra-subduction zone ophiolite formed in the forearc setting records the magmatic response to the subduction initiation, but the magmatic evolution in the NOC is poorly constrained. The low-Ti gabbros have low SiO₂ in whole-rock composition and high Mg# in clinopyroxene. They also record highly depleted magma In contrast, dolerites and basalts have relatively higher SiO₂ in whole-rock composition and lower Mg# in clinopyroxene, with flat REE patterns accompanied by fractional crystallization. Significant variation in Yb content relative to Tb/Yb ratio also supports fractional crystallization from gabbros to basalts. In Th/Yb-Nb/Yb diagram, all samples plot in the region from the MORB type to the island arc tholeiite. The Nd-Sr isotopes and high Ba/La ratio suggest that the NOC was originally derived from a single depleted mantle source similar to the MORB and was subsequently affected by hydrothermal alteration, resulting in greenschist- to lower amphibolite-facies overprint to form albite, actinolite, epidote and chlorite. Detrital zircon U-Pb ages from volcanic sediments associated with the NOC concentrated at ca. 136 Ma, representing the timing of the main magmatic phase in the NOC. Our data, combined with the geochronological and geochemical data in previous studies, suggest that the low-Ti, highly depleted magma in the NOC was firstly generated at extensional spreading in the upper plate during subduction initiation, and then changed to island arc tholeiite composition with the development of the subduction zone during Early Cretaceous.

How to cite: Imayama, T., Sato, A., Dutta, D., Kaneda, Y., Watanabe, S., Hasegawa, T., Minami, M., Wakasugi, Y., Wakaki, S., and Keewook, Y.: Magmatic response to the subduction initiation of Early Cretaceous Nidar Ophiolite Complex, eastern Ladakh, NW Himalaya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2981, https://doi.org/10.5194/egusphere-egu23-2981, 2023.

There is a long-standing mystery regarding how subduction zones enter internal Atlantic-type oceans to complete their Wilson cycle. While the process of subduction initiation is challenging to tackle, the Atlantic is a natural laboratory that allows understanding of some of the different stages of the process of invasion of new subduction zones. Three different subduction zones seem to be entering the Atlantic from different edges: the Caribbean Arc, the Scotia Arc and around the Iberia Peninsula. While the first two examples constitute fully developed subduction zones, it is unknown how they will propagate in the future. Will they spread intra-oceanically or will the subduction migrate along the Atlantic passive margins? Iberia is a good place to investigate the processes involved in the formation of new subduction zones. There have been places of aborted subduction (along the Cantabrian margin), places of incipient subduction (North, West and Southwest Iberia) and there is a subduction arc currently propagating into the Atlantic Ocean (the Gibraltar Arc). We will focus on this last case. Last year, we presented a numerical model that showed that the Gibraltar Arc may indeed further propagate into the Atlantic. This year, we present new models that investigate the factors controlling such propagation. We test different parameters such as the presence of weak zones in the adjacent margins and in the oceanic lithosphere (fracture zones) to obtain insights into the main factors controlling the first stages of propagation of new subduction zones in Atlantic-type oceans.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020- IDL

How to cite: Duarte, J. C., Riel, N., Cadenas, P., Rosas, F. M., Welford, J. K., and Kaus, B.: How do subduction zones spread over Atlantic-type oceans?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7211, https://doi.org/10.5194/egusphere-egu23-7211, 2023.

The initiation of subduction remains an enigmatic process and a variety of conceptual models has been proposed to explain such initiation. Conceptual models have been tested with geodynamic models and have been applied to various subduction settings around the globe. None of these tested models, however, are applicable to the Scotia subduction zone in the Southern Atlantic (also referred to as South Sandwich subduction zone), where subduction started in the Late Cretaceous/Early Cenozoic in a pristine ocean basin setting devoid of other subduction/collision zones. How this subduction zone initiated remains intensely debated, as exemplified by the variability of published plate tectonic reconstructions. We present new tectonic reconstructions of the Scotia region involving a relatively simple middle-Late Cretaceous plate boundary configuration that involves a new mechanism of subduction initiation, Subduction Invasion Polarity Switch (SIPS). SIPS involves a long-lived, wide and deep subduction zone (South American-Antarctic subduction zone) that imposes major horizontal trench-normal compressive deviatoric stresses on the overriding plate. The overriding plate consists of a narrow continental lithospheric (land) bridge at the trench (Cretaceous-Early Cenozoic Antarctica-South America land bridge) with oceanic lithosphere behind it (Weddell Sea-Atlantic Ocean). The stresses cause shortening and thrusting at the continent-ocean boundary in the backarc region of the overriding plate, forcing oceanic lithosphere under continental lithosphere, starting the subduction initiation process, and eventually leading to a new, self-sustaining, subduction zone (Scotia subduction zone) with an opposite polarity (dipping westward) compared to the long-lived subduction zone (dipping eastward). The model thus involves invasion of a new subduction zone into a pristine ocean basin (Atlantic Ocean), with the primary driver being a long-lived subduction zone in another ocean basin (Pacific Ocean). To test the physical viability of the SIPS model, we have conducted numerical geodynamic simulations of buoyancy-driven subduction. Numerical results demonstrate that the SIPS model is viable, with compressive stresses in the overriding plate resulting from strong trenchward basal drag induced by subduction-driven whole-mantle poloidal return flow and compression at the subduction zone plate boundary due to the high resistance of the subduction zone hinge of the long-lived subduction zone to retreat westward. Subduction initiation starts in the overriding plate after ~100 Myr of long-lived subduction, eventually resulting in the formation of a new, opposite-dipping, subduction zone. Notably, this new subduction zone develops at the continent-ocean boundary for models without and with a pre-imposed weak zone. Apart from the Scotia Sea region, the SIPS model might also be applicable to subduction initiation that has occurred elsewhere in the geological past (e.g. the New Caledonia, Lesser Antilles-Puerto Rico, Rocas Verdes and Arperos subduction zones), and that is presently in a very early stage of development in the Japan Sea.

How to cite: Schellart, W. P., Strak, V., Beniest, A., Duarte, J. C., and Rosas, F. M.: Subduction invasion polarity switch (SIPS):  A new mechanism of subduction initiation, with an application to the Scotia Sea region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5747, https://doi.org/10.5194/egusphere-egu23-5747, 2023.

The subduction zone interface is a shear zone of varying thickness that defines the boundary between the subducting slab and overriding plate. The rheology of this shear zone controls several important aspects of subduction dynamics, but accurately estimating its rheology can be complex due to the wide range of subduction materials and their varying rheological properties. Of particular importance is the relative strengths of metasedimentary and metabasic rocks at various temperature and pressure conditions. To better understand these rheological contrasts in naturally deformed rocks, we are conducting field and microstructural work in the Eclogite Zone in the Tauern Window, Austria. The eclogite zone preserves intercalated metamafic (metabasalt and metagabbro) and metasedimentary (quartzite, garnet mica schist, marble and calc-schist) rocks that were subducted and exhumed to the surface as a single structural unit. Using high resolution drone imaging, 2D structural mapping, and 3D structural modeling, we have documented map-scale relationships between metamafic and metasedimentary rocks in the Eissee region near Matrei. Our mapping demonstrates that the mafic eclogites consistently define slabs, lenses and boudins of up to 2 km in along-strike length and 0.2 km in thickness, embedded within the metasedimentary units, all of which are relatively uniformly deformed to very high strain. This suggests that eclogitized metamafic rocks persisted as rheological heterogeneities within the subduction channel through both the subduction and exhumation paths. Additionally, we are using microstructural observations to document the deformation mechanisms of individual rock units and to understand the weakening mechanisms that allowed some of the eclogites to break down from boudins to strongly foliated layers intercalated with the metasediments. At the interface between select metasedimentary and eclogite units there is a marked rheological change in eclogite rheology, likely due to fluids leached from the metasedimentary rocks, resulting in strain localization and increased foliation development within eclogite layers from meter to micron length scales. Integration of our mapping, outcrop, and microstructural observations will provide insights into the length scales of rheological heterogeneity on the deep interface and large-scale geodynamics of subduction through influencing the bulk viscosity of the interface.

How to cite: Tokle, L., Behr, W., Braden, Z., and Cisneros, M.: Persistence of initial lithological heterogeneity to deep subduction conditions: Implications for the rheology of the subduction zone interface, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5162, https://doi.org/10.5194/egusphere-egu23-5162, 2023.

How to cite: Arias, A., Beinlich, A., Eberhard, L., Scambelluri, M., John, T., Kotowski, A., and Plümper, O.: Micro to Macroscale: the three-dimensional network characteristics of serpentinite dehydration veins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3130, https://doi.org/10.5194/egusphere-egu23-3130, 2023.

Molybdenum (Mo) isotopes in magmatic rocks are a promising tool in high-temperature isotope geochemistry. In particular, basalts from subduction zones that are geochemically controlled by mass transfer through slab-fluid addition have systematically higher δ⁹⁸Mo values (i.e. measured ⁹⁸Mo/⁹⁵Mo ratio in a sample relative to that in a standard) than the depleted mantle (δ⁹⁸Mo = –0.21‰). In these rocks, the elevated δ⁹⁸Mo values are linked to high Pb/Ce and high (²³⁸U/²³⁰Th) ratios and can be reconciled by the addition of isotopically heavy Mo via a slab fluid component^1,2. So far, these systematics are best expressed in subduction zone basalts from the Mariana and Izu arc systems that also form coherent mixing trends between fluid-enriched mantle domains in δ⁹⁸Mo versus ¹⁴³Nd/¹⁴⁴Nd and ¹⁷⁶Hf/¹⁷⁷Hf space^1,2.

The Kamchatka arc system represents the northernmost expression of the W-Pacific convergent margin. Volcanic front lavas are dominated by slab-to-mantle mass transfer through fluid transport, whereas subduction of the Emperor seamount ridge gives rise to back-arc basalts with a geochemical and isotopic affinity to within-plate basaltic rocks³.

Here, we report δ⁹⁸Mo data for 47 basalts from an E-W transect across the Kamchatka peninsula that have previously been analysed for their major, trace element, radiogenic and stable isotope data. The δ⁹⁸Mo data extent the trend defined by samples from the Marianas and Izu arcs starting from moderately high δ⁹⁸Mo and Pb/Ce values towards sub-depleted mantle δ⁹⁸Mo and mantle-like Pb/Ce ratios that indicate the presence of a source component formed by partial melts of a rutile-bearing mafic crust⁴.

The common geochemical and isotopic trends formed by the combined Mariana – Izu – Kamchatka datasets suggest a surprisingly uniform Mo isotope composition of a subduction zone fluid endmember for more than 5000 km along-strike of the Circum-Pacific subduction zone system. Our data also confirm the presence of an enriched source component in the Kamchatka mantle wedge, possibly originating from the subducted Emperor seamount chain⁵.

¹Freymuth, H., et al., EPSL 432, 176-186 (2015). ²Villalobos-Orchard, J., et al., GCA 288, 68-82 (2020). ³Churikova, T., et al. JPet 42, 1567-1593 (2001). ⁴Chen, S., et al., Nat. Comm. 10, 4773 (2019). ⁵Shu,Y., et al.,Nat. Comm. 13, 4467 (2022).

How to cite: Willbold, M. and Wörner, G.: Molybdenum Isotope Systematics of the Kamchatka Subduction Zone System, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9814, https://doi.org/10.5194/egusphere-egu23-9814, 2023.

Volatiles expelled from subducted plates promote melting of the overlying warm mantle, feeding arc volcanism. However, debates continue over the factors controlling melt generation and transport and how these determine the placement of volcanoes. To broaden our synoptic view of these fundamental mantle wedge processes, we image seismic attenuation beneath the Lesser Antilles arc, an end-member system that slowly subducts old, tectonised lithosphere. Punctuated anomalies with high ratios of bulk-to-shear attenuation (Qκ-1/Qµ-1 > 0.6) and VP/VS (>1.83) lie 40 km above the slab, representing expelled fluids that are retained in a cold boundary layer, transporting fluids towards the back-arc. The strongest attenuation (1000/QS~20), characterising melt in warm mantle, lies beneath the back-arc, revealing how back-arc mantle feeds arc volcanoes. Melt ponds under the upper plate and percolates toward the arc along structures from earlier back-arc spreading, demonstrating how slab dehydration, upper plate properties, past tectonics, and resulting melt pathways collectively condition volcanism.

How to cite: Hicks, S., Bie, L., Rychert, C., Harmon, N., Goes, S., Rietbrock, A., Wei, S., Collier, J., Henstock, T., Lynch, L., Prytulak, J., Macpherson, C., Schlaphorst, D., Wilkinson, J., Blundy, J., Cooper, G., Davy, R., and Kendall, J.-M.: Slab to back-arc to arc: fluid and melt pathways through the mantle wedge beneath the Lesser Antilles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11540, https://doi.org/10.5194/egusphere-egu23-11540, 2023.

The thermal structure of subduction zones enacts a first-order control on many geological processes and properties, including the locus and degree of slab devolatilization, and the associated densities and strengths of subducting material. Modeling studies with fixed subduction geometries and plate velocities have been used to map out how various subduction parameters affect the pressure-temperature conditions of slabs and, in turn, the depths of major dehydration reactions. However, there is abundant geological evidence that slab properties, and the associated temperatures, evolve over few-Myr timescales. In this study, we use numerical subduction models to target this time dependence. Specifically, we focus on the styles and drivers of thermal transience and the imprint of this on subducting slab dehydration and slab strength.

Specifically, we have developed 2-D and 3-D subduction models that enable slab properties to evolve through time in a dynamically consistent fashion using the ASPECT finite element code^1-3. We use these models to investigate: i) the extent to which slab thermal conditions – and the associated metamorphic reactions and slab strength – evolve throughout the lifetime of a subduction zone, ii) the effects of first-order subduction zone properties on this evolution, and iii) the degree to which three-dimensionality (i.e., the presence of a slab edge) impacts this evolution. Regardless of imposed basic subduction parameters (e.g., plate ages, crustal strengths), our model subduction zones exhibit highly time-dependent thermal evolutions. The slab top, for example, exhibits rapid cooling during initiation and slower cooling subsequently, with along-strike temperature variations of up to ~40°C in the 3-D models. This thermal transience has fundamental implications for the geophysical and geochemical evolution of subduction zones; it manifests in a strong time dependence of dehydration depths and magnitudes and, in turn, substantial variability in slab strength. 

1: Bangerth, W., Dannberg, J., Gassmoeller, R., & Heister, T. (2020). ASPECT v2.1.0, Zenodo. https://doi.org/10.5281/ZENODO.3924604

2: Heister, T., Dannberg, J., Gassmöller, R., & Bangerth, W. (2017). High accuracy mantle convection simulation through modern numerical methods - II: Realistic models and problems. Geophys. J. Int., 210(2), https://doi.org/10.1093/gji/ggx195

3: Holt, A. F., & Condit, C. B. (2021). Slab temperature evolution over the lifetime of a subduction zone. Geochem., Geophys., Geosys., 22, doi:10.1029/2020GC009476.

How to cite: Holt, A., Condit, C., Turino, V., Epstein, G., Stoner, R., and Guevara, V.: Time dependent slab temperatures, metamorphism, and mechanical properties: Insights from dynamic subduction models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10756, https://doi.org/10.5194/egusphere-egu23-10756, 2023.

How to cite: Brizzi, S., Becker, T., Faccenna, C., Behr, W., van Zelst, I., Dal Zilio, L., and van Dinther, Y.: The role of sediments on subduction dynamics and geometry: insights from numerical modeling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5221, https://doi.org/10.5194/egusphere-egu23-5221, 2023.

Microcontinent accretion during oceanic subduction is one of the main contributors to continental crustal growth. Many of the continental mountain belts we find today were built from accretionary orogenesis, for example, the Cordillera of the west coast of the Americas, the European Alps, and the Australian Lachlan orogen. Continental growth can also be observed in modern accretionary orogens such as the Pacific accretionary belt, with the collision of the Philippine microplate, and the Taiwan-Luzon-Minduro Belt. In many of these systems, multiple bathymetric highs, such as microcontinental terranes, island arcs, or oceanic plateaus, are accreted before full oceanic closure, thus significantly altering the subduction zone before continental collision occurs.
The process of accretion implies a complex balance of multiple geodynamic forces that can result in either microcontinent subduction, microcontinent accretion, or subduction stalling (which could lead to the initiation of an altogether new subduction zone). The most important driving forces in this system are the slab-pull force arising from the negative buoyancy of the down-going slab and the far-field force which is the result of large-scale plate-motions external to the subduction zone. These forces are counteracted (among others) by friction along the subduction interface and the buoyancy of the downgoing microcontinent. The resulting net forces control the overall stress-field of the overriding plate as well as the state of stress and potential deformation of any further microcontinents embedded within the oceanic lithosphere that are not yet in the subduction zone. 
When multiple microcontinents are embedded in the subducting oceanic plate, the friction along the subduction interface and its temporal variations can take a crucial role. The accreting microcontinents have a first order effect on the length and the rheology of the subduction channel, thereby controlling the interface friction. The fate of the microcontinents (e.g. full or partial accretion, or subduction) also affects the overall buoyancy of the slab, altering the balance of forces through the slab-pull.
Using 2D thermo-mechanical experiments with the finite-element software SULEC-2D, we explore the roles of the structure and rheology of multiple accreting microcontinents (controlling their integrated strength) as well as the velocity of the subducting plate (controlling the far-field and the slab-pull force) to better understand how accretion of crustal units can modify the subduction zone and affect later continental collision. Our setup is comprised of a subducting oceanic basin surrounded by two continents. In this setup the oceanic plate is either “empty” or one or two microcontinents are embedded within it.
Our first results show that microcontinent accretion is promoted by the presence of a weak rheological detachment layer within the microcontinent. In turn, strong coupling of the microcontinental crust to its host-lithosphere promotes terrane subduction and may ultimately lead to the stalling of subduction. Moreover, the behavior of the microcontinents during accretion and subsequent continental collision has a first order effect on the structural style of the resulting orogen as the rheology of the microcontinents controls the degree of localization of deformation in the subduction channel.

How to cite: Erdős, Z., Buiter, S., and Tetreault, J.: Dynamics of multiple microcontinent accretion during oceanic subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6155, https://doi.org/10.5194/egusphere-egu23-6155, 2023.

Because Earth's tectonic plates are doubly curved shells, their mechanical behavior during subduction can differ significantly from that of flat plates. We use the boundary-element method (BEM) to study free (gravity-driven) subduction in axisymmetric and 3-D geometry, with a focus on determining the dimensionless parameters that control the dynamics. The axisymmetric model comprises a shell with thickness h and viscosity η₁ subducting in an isoviscous planet with radius R₀ and viscosity η₂. The angular radius of the trench is θ_t. Scaling analysis based on thin-shell theory reveals two key dimensionless parameters: a `flexural stiffness' St = (η<sub>1</sub>/η<sub>2</sub>)(h/l<sub>b</sub>)<sup>3</sup> that is also relevant for flat plates, and a new `dynamical sphericity number' Σ_D = (l_b/R₀)cotθ_t that is unique to spherical geometry. Here l_b is the `bending length', or the sum of the lengths of the slab and of the seaward flexural bulge. The definition of Σ<sub>D</sub> implies that the dynamical effect of sphericity is greater for small plates than for large ones; we call this the `sphericity paradox'. By contrast, the purely geometric effect of sphericity is opposite, i.e. greater for large plates than for small ones. The dynamical and geometrical effects together imply that sphericity significantly influences subduction at all length scales. We confirm the scaling analysis using BEM numerical solutions, which show that the influence of sphericity on the slab sinking speed (up to a few tens of percent) and on the hoop stress (up to a factor of 2-3) is largest for small plates such as the Juan de Fuca, Cocos and Philippine Sea plates. We next study a 3-D model comprising a plate bounded by a ridge and a semicircular trench subducting in a three-layer earth consisting of an upper mantle, a lower mantle and an inviscid core. We examine the linear stability of the shell to longitudinal perturbations corresponding to buckling, and determine a scaling law for the most unstable wavelength that we compare with the observed shapes of northern/western Pacific trenches. 

How to cite: Ribe, N., Chamolly, A., Gerardi, G., Chaillat, S., and Li, Z.: Scaling of Free Subduction on a Sphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2103, https://doi.org/10.5194/egusphere-egu23-2103, 2023.

It has long been recognised that the shape of subduction zones is influenced by Earth’s sphericity, but the effects of sphericity are regularly neglected in numerical and laboratory studies that examine the factors controlling subduction dynamics: most existing studies have been executed in a Cartesian domain, with the small number of simulations undertaken in a spherical shell incorporating plates with an oversimplified rheology, limiting their applicability. There are therefore many outstanding questions relating to the key controls on the dynamics of subduction. For example, do predictions from Cartesian subduction models hold true in a spherical geometry? When combined, how do subducting plate age and width influence the dynamics of subducting slabs, and associated trench shape? How do relic slabs in the mantle feedback on the dynamics of subduction? These questions are of great importance to understanding the evolution of Earth's subduction systems but remain under explored.

In this presentation, we will target these questions through a systematic geodynamic modelling effort, by examining simulations of multi-material free-subduction of a visco-plastic slab in a 3-D spherical shell domain. We will first highlight the limitation(s) of Cartesian models, due to two irreconcilable differences with the spherical domain: (i) the presence of sidewall boundaries in Cartesian models, which modify the flow regime; and (ii) the reduction of space with depth in spherical shells, alongside the radial gravity direction, the impact of which cannot be captured in Cartesian domains, especially for subduction zones exceeding 2400 km in width. We will then demonstrate how slab age (approximated by co-varying thickness and density) and slab width affect the evolution of subducting slabs, using spherical subduction simulations, showing that: (i) as subducting plate age increases, slabs retreat more and subduct at a shallower dip angle, due to increased bending resistance and sinking rates; (ii) wider slabs can develop along-strike variations in trench curvature due to toroidal flow at slab edges, trending toward a `W'-shaped trench with increasing slab width, and (iii) the width effect is strongly modulated by slab age, as age controls the slab's tendency to retreat. Finally, we will show the diverse range of ways in which remnant slabs in the mantle impact on subduction dynamics and the evolution of subduction systems.

How to cite: Davies, R., Chen, F., Goes, S., and Suchoy, L.: Controls on the Dynamics of Subducting Slabs in a 3-D Spherical Shell Domain, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4710, https://doi.org/10.5194/egusphere-egu23-4710, 2023.

Plateau subduction is a common process at different plate convergent margins, and they often modify subduction and affect slab behaviour. However, fewer studies have been conducted in the intraoceanic subduction context, and the physical and rheological parameters involved imply a strong hypothesis on the initial conditions (thermal state, no flow in the mantle, no interaction with the tectonic network). Here, we use global three-dimensional spherical mantle convection models to investigate the potential impacts of a subducting plateau on subduction zones and plate reorganization from regional to global scales in a fully self-consistent plate-like tectonics system. Our models show that plateaus with different sizes (length, width and thickness) can locally slow down the trench retreat rate. A larger plateau prevents trench migration, eventually terminating the subduction. The buoyancy of plateaus is found to influence the shape of the trench. Low buoyancy plateaus do not deform the trench as they subduct while in models with buoyant plateaus, the trench advances landward in front of a plateau forming an arcuate shape in the map. This arcuate shape of the trench is further enhanced with decreasing buoyancy and increasing viscosity. If the oceanic plateau has a higher yield stress, it will always drive the formation of the arcuate trench before fully subducted, regardless of the buoyancy. The simulations suggest that any single plateau rheology variable (buoyancy, or yield stress) except the viscosity can influence trench migration behaviour on a regional scale. We will also explore how plateau subduction modifies the global tectonic evolution over 100 My.

How to cite: Liu, Y., Coltice, N., Le Pourhiet, L., and Wu, Z.: How a subducting plateau impacts regional and global tectonics?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7188, https://doi.org/10.5194/egusphere-egu23-7188, 2023.

The theory of plate tectonics acknowledges that drifting lithospheric plates are rigid and do not undergo substantial deformation except near or at plate boundaries. However, studies have shown that intra-plate deformation is a feature for continental lithosphere and can originate from different mechanisms such as lithospheric drips, delamination, and in-plane stresses. On the other hand, there is not well-known understanding of tectonic deformation within the interior of ocean plates. We compile data to show there is geological and geophysical evidence documenting that the drifting Pacific plate has been undergoing appreciable extensional deformation at the locations of its oceanic plateaux. Namely, the Ontong Java, Shatsky Rise, Hess Rise, and Manihiki plateaux show extensive evidence for normal faults, horst-graben structures, and extension related magmatic activity at a significant distance from plate boundaries. Furthermore, this deformation occurred after the initial emplacement of their associated large igneous provinces (LIPs) and before their arrival to subduction zones.

We present numerical geodynamic experiment results demonstrating that terranes embedded in ocean plates can undergo extensional deformation prior their accretion to the overriding plate due to slab-pull (e.g., a “subduction pulley”).  Our numerical models show that the subduction pulley is also a valid mechanism for the extensional deformation of the Pacific oceanic plateaux even at remote locations from the plate boundaries. For instance, tensional stress originated from down-going slabs can be transmitted through strong oceanic lithosphere over long distances (>1000 km) and deform the plate at its weak oceanic plateaux regions. The numerical experiments further demonstrate that high crustal thickness reduces the bulk strength of ocean lithosphere at the location of oceanic plateaux and makes them susceptible to slab-pull related extension—manifesting on the surface as intra-ocean plate deformation.

How to cite: Gün, E., Pysklywec, R., Heron, P., Topuz, G., and Göğüş, O.: Intra-Plate Deformation of the Pacific: Evidence from Oceanic Plateaux and Geodynamic Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8910, https://doi.org/10.5194/egusphere-egu23-8910, 2023.

The subduction of positively buoyant features has been suggested to cause flat or shallow dipping slabs, the formation of cusps in trench geometry and periods of reduction or full cessation of arc magmatism. Additionally, recent earthquake data indicates that the subduction of the Hikurangi plateau near New Zealand causes a rotation of intraplate stresses. In this study, we present a series of multi-material 3-D simulations of free subduction to investigate how subduction of buoyant elongated features, or ridges, impact downgoing plate velocities, trench motions, slab morphology and intraplate stress regime. We examine how these parameters are affected by the age of the subducting plate and the relative buoyancy and position of the buoyant ridge. We find that buoyant ridges change slab sinking and trench retreat rates and locally rotate intraplate stresses. These, in turn, modify the evolution of slab morphology at depth and trench shape at the surface, as trench retreat is reduced, or switches to trench advance, where the ridge subducts. These effects depend strongly on downgoing plate age: on young and weak plates, the change in trench shape is more localised than on old and strong plates. We observe slab shallowing around the ridge only in young plates, while the stronger pull by the more negatively buoyant old plates causes slab steepening near the buoyant ridge. Buoyant ridges on old plates which are located near stagnating or advancing regions, typical in wide slabs, modify trench behaviour more strongly than ridges in other regions of the trench. Bending-related intraplate earthquakes are more likely in older plates where higher stress is accumulated and the rotation due to the buoyant ridge is more widespread than for younger plates. The combined effects of buoyant feature location, subducting plate age and overriding plate properties can result in a range of responses: from mainly trench deformation, through local slab shallowing, to the formation of a flat slab, a variation in expressions also observed on Earth.

How to cite: Suchoy, L., Goes, S., Chen, F., and Davies, D. R.: A 3-D numerical investigation of the impact of buoyant features on subduction dynamics and stress, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14049, https://doi.org/10.5194/egusphere-egu23-14049, 2023.

Shallowing of slabs during their descend into the upper ~200 km of the mantle, i.e. flat subduction, can be associated with extensive geochemical, structural, and dynamic modification of the continental lithosphere. Anomalously buoyant oceanic lithosphere, overthrusting, and interactions with cratonic keels have been suggested to explain flat slabs, but the dynamics of flat slab subduction remain to be fully understood. Here, we explore self-consistent flat-slab subduction using the finite element code ASPECT with adaptive mesh refinement and a free surface boundary condition. We focus on the role of the structure of the overriding continental plate including the role of keels. Results show that flat slabs arise when the subduction interface is weak and the overriding continental lithosphere is positively buoyant, leading to trench rollback. Substantiating previous work, we also observe that a strong continental keel further enhances flat slab formation. Our results also indicate that as the slab flattens, regions of pronounced subsidence and extension develop within the foreland region, on top of more typical, larges-scale subsidence recorded within the continental interior. Regional uplift and subsidence of the overriding plate are not only linked to flat slab emplacement and removal, but also affected by slab dynamics of the shallow upper mantle. Our work can contribute to a better understanding of continental deformation including sediment transport on continent-wide scales.

How to cite: Grima, A. G. and Becker, T.: Modeling the interactions between slab dynamics and continental overriding plate deformation during flat subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1322, https://doi.org/10.5194/egusphere-egu23-1322, 2023.

The Sierras Pampeanas (29 - 35°S) located south of the Altiplano-Puna plateau above the Chilean subduction zone, consist of uplifted foreland basement blocks that are an expression of the eastward propagation of compresive deformation. Their presence is one of the most enigmatic features of the Andes. The formation of these ranges is considered an end member of the thick-skinned foreland deformation style, which involves the deformation of the sedimentary cover and the crystalline basement. At 33°S, the onset of compression occurs at 22Ma, and the change between thin and thick skinned deformation style at 16Ma. However, the mechanism responsible for this evolution remains controversial. Two main hypotheses have been proposed to explain this evolution. The first one atributes the change in foreland deformation style to the setting of the Pampean flat slab at 12 Ma, which is contemporanous to the southward migration and subduction of the Juan Fernandez hotspot ridge at 33S. Alternatively, it has been proposed that the reactivation of pre-existing structures inherited from pre-Neogen tectonic events could better explain the onset of deformation about 10 Ma before the arrival of the flat-slab. To resolve this controversial debate, we have developed a data-driven 3D geodynamic model using the FEM geodynamic code ASPECT. We incorporated the present-day geometrical and thermal configuration of the southern central Andes and the flat-slab from previous models. This approach allowed us to study the structural and thermomechanical factors responsible for the location of deformation in the Sierras Pampeanas (e.g., topography, temperature and composition, strength of the lithosphere and velocity of the plates).  Moreover,  we investigated the role of the geometry of the Nazca plate on the foreland deformation, and proposed a new mechanism ("flat slab conveyor)" that reconciles the timing of the main geological events (onset of shortening, change in tectonics style of deformation of the foreland, growth of the topography, cessation of volcanic activity, uplift of the basement, and propagation of the deformation). This work expands our understanding of how plates interact at convergent boundaries, in particular at the subduction zones, and how and where deformation is expressed at the surface of the the upper continental plate.

How to cite: Pons, M., Rodriguez Piceda, C., Sobolev, S. V., Scheck-Wenderoth, M., and Strecker, M. R.: Understanding the role of structural inheritance and flat slab geometry in Central Andes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8492, https://doi.org/10.5194/egusphere-egu23-8492, 2023.

To explore the conditions that lead to mountain-building in the case of an oceanic subduction, we conduct analog experiments (with silicon putty upper and lower plates, glucose syrup upper mantle) where subduction is driven by slab pull but also by an underlying mantle flow. Here, plate displacement is not imposed as in most models, but is controlled by the overall balance of forces in the system. We simulate three scenarios: no mantle flow (slab-pull driven subduction), mantle flow directed toward the subducting plate, and mantle flow directed toward the overriding plate. In the case of this latter scenario, we also test the influence of pre-existing rheological contrasts in the upper plate to best reproduce natural cases where inheritance is common. Our experiments show that when plate convergence is also driven by a background mantle flow, the continental plate deforms with significant trench-orthogonal shortening (up to 30% after 60 Myr), generally associated with thickening. We further identify that upper plate shortening and thickening is best promoted when the mantle flow is directed toward the fixed overriding continental plate. The strength of the upper plate is also a key factor controlling the amount and rates of accommodated shortening. Deformation rates increase linearly with decreasing bulk strength of the upper plate, and deformation is mostly localized where viscosity and strength are lower. When compared to the particular natural case of the Andes, our experiments provide key insights into the geodynamic conditions that lead to the building of this Cordilleran orogen since the Late Cretaceous - Early Cenozoic.

How to cite: Lacassin, R., Habel, T., Replumaz, A., Guillaume, B., Simoes, M., Geffroy, T., and Kermarrec, J.-J.: Upper-plate shortening and Andean-type mountain-building in the context of mantle-driven oceanic subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7182, https://doi.org/10.5194/egusphere-egu23-7182, 2023.

Shifts in isotopic and trace element composition in magmatic zircon are commonly related to internal forcing independent of plate parameters (e.g., crustal thickness, delamination), or external factors that are governed by parameters of the down-going plate, particularly the slab dip. U-Pb geochronology, trace elements and Hf-O isotope analyses on detrital zircon from central Patagonia (45 °S – 48 °S) were used in this study as fingerprint for monitoring slab dip variations and related processes (e.g., arc migration, slab rollback) as well as upper-plate stress regime evolution. According to literature, main geodynamic events include: (i) two shallow slab episodes during late Triassic and late Early Cretaceous – early Paleogene times, the latter characterized by significant contraction; (ii) two phases of slab rollback during Jurassic – Early Cretaceous and late Paleogene, associated to a steep slab configuration, extensional processes and crustal thinning; (iii) a slab window episode during the Paleogene; and (iv) a Miocene contractional phase following an increase of plate convergence rates. Although slab dynamics seems structurally related with upper-plate architecture, it appears to exert little to null control on the magmatic arc reservoirs. Indeed, our results, integrated with published data from a larger area (40 °S – 52 °S), show long-lasting trends ( > 70 Ma) in the isotopic and trace elements record, that are mostly independent of these events. We thus consider that other processes, eventually coeval, controlled the enrichment of magmas and may overtake the influence of slab dip and upper-plate architecture on the isotopic and trace elements signature. These other processes include subduction erosion, ridge subduction, subduction of a younger slab, potential slab tearing, and/or change in convergence rates that affects mantle flow. 

How to cite: Genge, M., Witt, C., Zattin, M., Bosch, D., Bruguier, O., and Mazzoli, S.: Are the long-lasting isotope trends in central Patagonia independent from slab dynamics and upper-plate architecture?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4644, https://doi.org/10.5194/egusphere-egu23-4644, 2023.

A forearc environment is usually characterised by a relatively low geothermal gradient and hence little magmatic activity occurs. However, S-type granites were discovered within the forearc accretionary complex of the East Kunlun Orogenic Belt. The S-type granites intruded into an upper amphiolite facies partially migmatitic crystalline basement in form of dikes and sills at ca. 440 Ma which corresponds to the transition of the Proto-Tethyan to the Paleo-Tethyan realm in the northern Tibetan Plateau. The observed granites contain either garnet + biotite + muscovite or garnet + muscovite: (1) muscovite granite is strongly peraluminous with an aluminous saturation index (ASI) of more than 1.1 (ASI = molar [Al₂O₃/(Na₂O+K₂O+CaO]) and has high-K calc-alkaline characteristics, low Sr/Y (1.9–16.1) and La_N/Yb_N (1.85–13.2) ratios. (2) Two-mica granite is moderately peraluminous (ASI = 1.02–1.09), has high Ca and low K contents as well as high Sr/Y (16.8–67.7) and La_N/Yb_N(10.9–33.3) ratios. Other trace element contents and their ratios also show striking differences with high Sr (207–324 ppm) content and CaO/Na₂O (0.47–0.96) ratio, and a low Rb/Sr (0.04–0.32) ratio for two-mica granite, but low Sr (63–126 ppm) content and CaO/Na₂O (0.08–0.20) ratio, and a high Rb/Sr (0.56–2.53) ratio for muscovite granite. The observed differences are due to different protolith chemistries and melting mechanisms. Based on melting experiments of metasedimentary rocks (Patiño Douce and Harris, 1998), muscovite granite was most likely produced by dehydration melting of a metapelitic source and the two-mica granite by H₂O-fluxed melting of a metagreywacke. Zircon Hf isotopes of the two S-type granites have ε_Hf(440 Ma) values of -6.85 to +12.02 indicating the involvement of a mantle-derived magma which probably triggered the anatexis of supracrustal rocks deposited in a forarc regime. Coveal adakites with a younging westward trend as well as mafic rocks have been reported in this accretionary complex, which together with anatexis and metamorphism of accreted material support the occurrence of a slab window beneath the forearc accretionary complex of the East Kunlun Orogenic Belt during subduction of the Tethyan oceanic slab.

References

Patiño Douce, A.E., Harris, N., 1998. Experimental constraints on Himalayan anatexis. Journal of Petrology 39, 689–710.

How to cite: Ren, X., Dong, Y., He, D., and Hauzenberger, C.: Origin of S-type granites in the forearc accretionary complex of the East Kunlun Orogenic Belt, northern Tibetan Plateau, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9902, https://doi.org/10.5194/egusphere-egu23-9902, 2023.

Lithospheric structure in subduction settings controls the distribution of thermal, compositional and rheological interfaces.  It therefore plays a key role in the generation, fractionation and transport of subduction-related melts that are a vital ingredient of the formation of porphyry copper deposits.  Renewed efforts to understand the linkage between lithospheric structure and the location, grade and endowment of porphyry copper deposits has raised the possibility of using crustal and lithospheric mantle structure as an exploration tool.  One example is a suggested relationship between the genesis of porphyry copper deposits – known to be associated with evolved, silica-rich magmas – and the thickness of the crust.  Here, using a new compilation of spot measurements, we explore the utility of crustal thickness as an exploration tool for porphyry copper deposits.

How to cite: Stephenson, S., Hoggard, M., Haynes, M., Czarnota, K., and Czado, K.: Lithospheric Controls on the Distribution of Porphyry Copper Deposits, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13615, https://doi.org/10.5194/egusphere-egu23-13615, 2023.

The Alboran margin in the Betics formed as a result of backarc crustal thinning oblique to the direction of the slab retreat. The history of sediment infill, subsidence and faulting reveals extension at upper crustal levels operated from the Serravallian-early Tortonian to the late Tortonian (14-8 Ma) synchronously with Ca-K magmatism. Only recently, around 8 Ma, the retreating slab detached resulting in the onset of the tectonic inversion of the margin. Here we report new apatite (U-Th)/He thermochronological analyses from Cabo de Gata magmatic province, and new U-Pb dating, Oxygen (O) and carbon (C) stable isotopic analyses of calcite-filled veins from the Tabernas basin combined with fluid temperatures determined by clumped isotope D47 analyses. U-Pb ages from 8.56 ± 0.21 to 4.88 ± 0.45 Ma are remarkably synchronous with late alkaline Tortonian-Messinian magmatic events and post-Messinian uplift. Low-temperature thermochronology confirms that magmatic edifices cooled below sea-level at around 8-7 Ma, and then slowly exhumed onshore during shortening along the Carboneras fault and regional kinematic reorganisation associated with slab detachment. C and O isotopic compositions (-17.23‰ to -9.08‰ for O and -15.77‰ to -1.60‰ for C, in V-PDB) of calcite veins are close to carbonates endmember of the Alpujárride basement. The O and C isotopes trend highlights a burial where all δ18O and δ13C calcite have depleted values compared with host rocks indicating a higher temperature of calcite precipitation (estimated at 83.7°C) and an increasing organic matter degradation with depth. The concordance on ages suggests that deep processes including mantle delamination and hot mantle triggered CaCO3 fluid precipitation and uplift during the transition from extension to onset of tectonic inversion. The deep mantle processes related to the 8 Ma event impacted not only the uplift of the Alboran basin that caused the Messinian Salinity Crisis that is well recorded in the Betics, but also the recent uplift of Iberia and Western Europe.

How to cite: Mouthereau, F., Larrey, M., Boschetti, L., Beaudoin, N., Brichau, S., Roberts, N., Huyghe, D., Daëron, M., Miegebielle, V., and Calassou, S.: Processes related to the rift-to-collision transition in the eastern Betics as revealed by low-temperature thermochronology on magmatic, U-Pb dating and clumped isotopes on calcite-filled veins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13467, https://doi.org/10.5194/egusphere-egu23-13467, 2023.

The geometry of subducting slabs is largely controlled by mantle rheology and time evolving processes of surface plate boundaries. Imaging of a detailed slab distribution and its surrounding can provide information of physical, chemical, and dynamical properties of the upper mantle. Based on new high-resolution 3-D tomography of subducting Pacific slab in northeast Asia, we revealed a prominent gap within the stagnant portions of the slab showing an abrupt change in its lateral trends that follow the trace of plate junctions associated with plate reorganization at the western Pacific margin during the Cenozoic. Focused partial melting above the slab gap was inferred based on the spatial coincidence between the high Vp/Vs anomaly and the negative reflectivities above the 410-km discontinuity from local receiver function studies. The slab gap is possibly filled with low-velocity anomalies within the MTZ as evidenced by wavefield focusing of teleseismic body waves and absolute velocity imaging from previous studies. We explain the spatial coincidence between the low-velocity anomaly within the MTZ and the focused melt layer above the MTZ by the process of mantle dynamics related with secular variation of slab geometries by tearing. Isolated low-velocity anomalies within the MTZ imaged by seismic tomography without previous thermal disturbances (e.g., hot plume) are suggested to be the products of distinct MTZ compositions disturbed by former nearby slab subductions. Our results suggest a close dynamical relationship between the subducting slab and the MTZ, which promotes the formation of multi-scale chemically distinct domains in the deeper upper mantle.

How to cite: Song, J.-H., Kim, S., and Rhie, J.: Seismic Evidence of Slab Segmentation and Melt Focusing Atop the 410-km Discontinuity in NE Asia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10944, https://doi.org/10.5194/egusphere-egu23-10944, 2023.

Slab break-off is usually referred to as an early collisional process driven primarily by the slowing of the subduction rate as negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere that is attempting to subduct. In this context, slab tearing (or slab break-off propagation) is traditionally attributed to continental corner dynamics, when the subducting plate first detaches in the area of continental collision and then the slab window opens toward the adjacent segment of the convergence boundary, where ocean-continent subduction continues. Another important process, previously thought to be independent of slab break-off and horizontal slab tearing, is a fragmentation of the subducting slab along vertical planes perpendicular to the convergence direction. Previous numerical studies have linked this vertical slab tearing to pre-existing weakness within the subducting plate and/or abruptly changing convergence rates along the trench.

In our study, we use a 3D thermo-mechanical numerical approach to study slab tearing in a non-collisional geodynamic context. The effects of subduction obliquity angle, age of oceanic slab, and partitioning of boundary velocities have been investigated. We show, for the first time, that horizontal and vertical slab tearing are different stages of the same process, which can develop in a self-sustained manner in a non-collisional environment of oblique ocean-continent subduction. Even with an initially absolutely homogeneous oceanic plate and laterally unchanging and temporally constant boundary velocities, the obliquity of the active margin appears to be a sufficient factor to trigger complex system evolution, which includes the transition from horizontal to vertical slab tearing along with additional processes such as retreat and rotation of the trench, decoupling of the overriding and downgoing plates by upwelling asthenosphere in the mantle wedge (also termed “delamination”), initiation of new subduction, and formation of a transform fault.

Our results show striking similarities with several features – such as trench curvature, subduction zone segmentation, magmatic production, lithospheric stress/deformation fields, and associated topographic changes – observed in many subduction zones (e.g., Marianas, New Hebrides, Mexico, Calabrian).

How to cite: Koptev, A., Andrić-Tomašević, N., Maiti, G., Gerya, T., and Ehlers, T.: Horizontal and vertical slab tearing as different stages of a self-sustaining process developing in a non-collisional setting with oblique subduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1559, https://doi.org/10.5194/egusphere-egu23-1559, 2023.

How to cite: Piccolo, A., Thielmann, M., and Spang, A.: Insights into slab detachment dynamics from 0D to 3D numerical experiments  , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14144, https://doi.org/10.5194/egusphere-egu23-14144, 2023.

Continental collision zones form at convergent plate boundaries after negatively buoyant oceanic lithosphere subducts entirely into the Earth's mantle, whereafter collision ensues, and colliding continents are sutured together. In models of free subduction, the volume of the preceding and adjacent negatively buoyant oceanic lithosphere controls the system's driving force and dynamics. To investigate the dynamics of long-term continental subduction, indentation and collisional boundary migration and associated slab dynamics we designed large-scale numerical models of subduction-and-collision including two sets of modelled depths: whole mantle (2880 km) and upper mantle + partial lower mantle (960 km) and varying the trench parallel length ratio (1.5 - 2) of the indenting continental lithosphere (~2300 km) and adjacent oceanic lithosphere. In this contribution, we present the contrasting evolution of continental subduction and indentation coupled with adjacent oceanic slab rollback focusing on the different slab dynamics observed by varying the depth of the mantle in the models. Intriguingly, the whole mantle models show sustained continental indentation and concurrent deep continental subduction to mid-low upper mantle depths resulting in deep slab tearing at the subducted continental margin and shallow slab tearing at the trench parallel boundaries of the continental plate. In addition, the models also show continental underthrusting beneath the overriding plate and underplating of the continent, coeval with indentation and adjacent oceanic slab rollback. Together, these results provide insights into the India-Eurasia collision zone where the prolonged northward indentation of India during the last 50 Myrs and the rollback of the Sunda slab appear linked.

How to cite: Laik, A., Schellart, W., and Strak, V.: Protracted continental subduction, indentation and collisional boundary migration coupled with adjacent oceanic slab-rollback and slab detachment in large-scale buoyancy-driven 3D whole-mantle scale numerical models of subduction-and-collision., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14232, https://doi.org/10.5194/egusphere-egu23-14232, 2023.