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SUMMARY Continental collision zones form at convergent plate boundaries after the negatively buoyant oceanic lithosphere subducts entirely into the Earth’s mantle. Consequently, orogenesis commences, and the colliding continents are sutured together. During the collision, plate convergence and motion of the sutured boundary towards the overriding plate are manifest in its deformation, as is the case for the long-term (∼50 Ma) and nearly constant convergence rate at the India–Eurasia collisional zone that hosts the Himalaya. However, despite the long history of modelling subduction-collision systems, it remains unclear what drives this convergence, especially in models where subduction is driven solely by buoyancy forces. This paper presents dynamic self-consistent buoyancy-driven 2-D whole-mantle scale numerical models of subduction-and-collision processes to explore variations in density and rheological stratification of the colliding continent and overriding plate (OP) viscosity (a proxy for OP strength) that facilitate post-collisional convergence and collisional boundary migration. In models with a moderately buoyant indenting continent, the collisional boundary advance is comparatively low (0.1–0.6 cm yr–1), and convergence is driven by the dense continental lithospheric mantle that continues to subduct as it decouples from its deforming crust. Conversely, models with a highly buoyant indenting continent show sustained indentation at 0.5–1.5 cm yr–1 until the slab detaches. Furthermore, models with a weaker OP and lower backarc viscosity show an enhanced propensity for indentation by a positively buoyant continent. These models additionally highlight the role of whole mantle flow induced by the sinking of the detached slab in the lower mantle as it sustains slow convergence at an average rate of 0.36 cm yr–1 for ∼25 Myr after break-off as well as prevents the residual slab from educting. In previous buoyancy-driven partial mantle depth models such eduction does generally occur, given that free-sinking of the detached slab in the mantle is not modelled. Although these findings widen the understanding of the long-term convergence of indenting continents, the lower post-collisional advance rates (0.3–1.5 cm yr–1) compared to India’s approximate 1000–2000 km of northward indentation during the last 50 Myr attest to the need for 3-D models.

© 2021 The Author(s). Published by Oxford University Press on behalf of The Royal Astronomical Society.Flat slab subduction has been ascribed to a variety of causes, including subduction of buoyant ridges/plateaus and forced trench retreat. The former, however, has irregular spatial correlations with flat slabs, while the latter has required external forcing in geodynamic subduction models, which might be insufficient or absent in nature. In this paper, we present buoyancy-driven numerical geodynamic models and aim to investigate flat slab subduction in the absence of external forcing as well as test the influence of overriding plate strength, subducting plate thickness, inclusion/exclusion of an oceanic plateau and lower mantle viscosity on flat slab formation and its evolution. Flat slab subduction is reproduced during normal oceanic subduction in the absence of ridge/plateau subduction and without externally forced plate motion. Subduction of a plateau-like feature, in this buoyancy-driven setting, enhances slab steepening. In models that produce flat slab subduction, it only commences after a prolonged period of slab dip angle reduction during lower mantle slab penetration. The flat slab is supported by mantle wedge suction, vertical compressive stresses at the base of the slab and upper mantle slab buckling stresses. Our models demonstrate three modes of flat slab subduction, namely short-lived (transient) flat slab subduction, long-lived flat slab subduction and periodic flat slab subduction, which occur for different model parameter combinations. Most models demonstrate slab folding at the 660 km discontinuity, which produces periodic changes in the upper mantle slab dip angle. With relatively high overriding plate strength or large subducting plate thickness, such folding results in periodic changes in the dip angle of the flat slab segment, which can lead to periodic flat slab subduction, providing a potential explanation for periodic arc migration. Flat slab subduction ends due to the local overriding plate shortening and thickening it produces, which forces mantle wedge opening and a reduction in mantle wedge suction. As overriding plate strength controls the shortening rate, it has a strong control on the duration of flat slab subduction, which increases with increasing strength. For the weakest overriding plate, flat slab subduction is short-lived and lasts only 6 Myr, while for the strongest overriding plate flat slab subduction is long-lived and exceeds 75 Myr. Progressive overriding plate shortening during flat slab subduction might explain why flat slab subduction terminated in the Eocene in western North America and in the Jurassic in South China.

Subduction style is controlled by a variety of physical parameters. Here we investigate the effect of subducting plate length on subduction style using laboratory experiments of time-evolving buoyancy-driven subduction in 3-D space. The investigation includes two experimental sets, one with a lower (~740) and one with a higher (~1,680) subducting plate-to-mantle viscosity ratio (ηSP/ηM). Each set involves five models with a free-trailing-edge subducting plate and variable plate length (20–60 cm, scaling to 1,600–4,800 km), and one model with a fixed-trailing-edge subducting plate representing an infinitely long plate. Through determining the contact area between subducting plate and underlying mantle, plate length affects the resistance to trenchward motion of the subducting plate and thus controls the partitioning of the subduction velocity (vS) into the subducting plate velocity (vSP) and trench velocity (vT). This subduction partitioning thereby determines the subduction style by controlling the dip angle of the slab tip once it first touches the 660 km discontinuity. The low ηSP/ηM models display two subduction styles. Short plates (≤40 cm) induce a higher subduction partitioning ratio (vSP/vS), promoting trench advance and slab rollover geometries, whereas longer plates (≥50 cm) lead to a lower vSP/vS, producing continuous trench retreat and backward slab draping geometries. In contrast, the high ηSP/ηM models exclusively show trench retreat with draping geometries, as the high ηSP/ηM enables less slab bending before its tip touches the 660 km discontinuity. Our study indicates that future modeling work should consider the effects of plate length on the style and evolution of subduction.

Overriding plate deformation (OPD) and topography vary at different subduction zones, with some subduction zones showing mainly overriding plate extension and low topography (e.g. Mariana, Tonga, Izu-Bonin subduction zones), while some showing mainly shortening and elevated topography (e.g. Makran, southern Manila subduction zones). Here we investigate how different subduction modes, namely trench retreat and trench advance, affect OPD and generate corresponding topography with fully dynamic analogue models of time-evolving subduction in three-dimensional space. We conduct two sets of experiments, one of which is characterized by trench retreat and slab rollback, and the other characterized by trench advance and slab rollover. We compute the mantle flow, the overriding plate strain and topography during subduction using the particle image velocimetry technique (PIV). The overriding plate in the experiments showing continuous trench retreat experiences overall extension, while in the experiments with trench advance following trench retreat it experiences overall shortening. The overriding plate in both trench retreat and trench advance subduction modes present fore-arc shortening and intra-arc extension. Our experiments indicate that the overall OPD except in the fore-arc region is mainly driven by the horizontal mantle flow at the base of the OP inducing a viscous drag force (FD), and is determined by the gradient of the horizontal mantle flow velocity (dvx/dx). Furthermore, a large-scale trenchward overriding plate tilting and an overall subsidence of the overriding plate were observed in the experiments showing continuous trench retreat, while a landward tilting and an overall uplift of the overriding plate were observed during long-term trench advance. The two types of topography during the two different subduction modes can be ascribed to the large-scale trenchward and landward mantle flow, respectively, and thus represent forms of dynamic topography. Our models showing trench advance provide a possible mechanism for OPD in the Makran subduction zone, which has experienced overall trench-normal tectonic shortening in the overriding plate, but shows extension in a local region of the coastal Makran that is spatially comparable to that in our experiments. In addition, these models might also provide an explanation for the regional topography at the Makran subduction zone, which shows a long-wavelength topographic high in the overriding plate near the trench that decreases northward.

The influence of aseismic ridges on subduction kinematics and dynamics, and on the deformation of the overriding plate, remains a topic of debate. This study presents laboratory-based geodynamic models that simulate the process of aseismic ridge subduction below an overriding plate. The analog experiments show that, depending on its size, subduction of an aseismic ridge can impact on the kinematics of subduction, overriding plate deformation and, to a lower extent, on the geometry of the slab and that of the trench. Specifically, it can cause a reduction of the subducting plate and trench retreat velocities, decreases overriding plate extension and even drives local forearc shortening for the widest ridge, increases the slab dip angle next to the aseismic ridge, but decreases the dip angle at the aseismic ridge in case the ridge is thick and wide, and produces a local perturbation (indentation) of the trench geometry. The magnitude of the described modifications relies to a comparable extent on aseismic ridge width and thickness. The effects of aseismic ridge subduction observed in our models compare to those of the Louisville Seamount Chain, the Cocos Ridge, and the d'Entrecasteaux Ridge system in nature and provide an explanation for the local deformation observed at these subduction zones.

The South American subduction zone is enigmatic due to its fast subducting plate consumption, strong oscillation in subducting plate velocity, and deep mantle subduction. A key to help understand these subduction zone characteristics is through studying its dynamics with buoyancy-driven numerical modeling that uses independent variables to best approximate the dynamics of the real subduction system. We conduct a parametric investigation on the effect of upper mantle rheology, subduction interface yield stress and slab thermal weakening. To constrain those model variables, we attempt to find best-fits by comparing our model outcomes with the present-day slab geometry and estimates of Cenozoic velocities in the center of the South American subduction zone. Key ingredients that need to be reproduced are low slab dip angles close to the surface, steeper lower mantle dip angles, strong oscillation of the fast Farallon-Nazca subducting plate velocity and a progressive decrease in trench retreat rate during long-term subduction. We include these ingredients to define a model fitting score using 10 criteria. Our best fitting models involve a weak subduction zone interface (yield stress of ∼20 MPa) and significant slab thermal weakening to attain the fast Farallon-Nazca subducting plate velocity and to better reproduce the subduction partitioning since 48 Ma due to reduced shear stresses resisting downdip slab sinking and reduced slab bending resistance. Furthermore, a non-Newtonian upper mantle promotes slab folding and realistic oscillation of the subducting plate velocity. Whether and how this slab folding process induces temporal variations in Andean deformation remains an open question.

The South American subduction zone remains a topic of debate with long-lasting questions involving the origin of non-collisional orogeny and the effect of very large trench-parallel extent, slab sinking to great mantle depths, and aseismic ridge subduction. A key to help solve those issues is through studying the subduction zone dynamics with buoyancy-driven numerical modelling that uses constrained independent variables in order to best approximate the dynamics of the real subduction system. We conduct a parametric investigation on the effect of upper mantle rheology (Newtonian or non-Newtonian), subduction interface yield stress and slab thermal weakening. As a means of constraining those model variables we attempt to find best-fits by comparing our model outcomes with the present-day upper- and lower-mantle slab geometry observed on tomography models and obtained from earthquake hypocentre locations, as well as with estimates of Cenozoic velocities obtained from kinematic reconstruction. Key ingredients that need to be reproduced are slab flattening close to the surface, strong oscillation of the Farallon-Nazca subducting plate velocity and progressive decrease in trench retreat rate after a long period of time. We include these ingredients to define a model fitting score that contains a total of 9 criteria. Our best fitting model involves significant slab thermal weakening in order to attain the fast Farallon-Nazca subducting plate velocity and to better reproduce the subduction partitioning in the past 48 Myr, due to strong reduction of the shear stresses resisting downdip slab sinking and of the slab bending resistance. We further find that a non-Newtonian upper mantle rheology promotes slab folding and realistic associated oscillation of the subducting plate velocity. Our parametric study also indicates that the subduction interface must be weak in agreement with earlier laboratory subduction models, but not too weak, with a yield stress of ~ 14–21 MPa, otherwise the fit becomes poor. Our models moreover suggest that slab folding at the 660 km discontinuity can be a cause of the Farallon-Nazca subducting plate velocity oscillation. Whether and how this slab folding process induces periodic/episodic variations in deformation of the Andes remains an open question that requires further research.

©2019. American Geophysical Union. All Rights Reserved. Independent models of P wave and S wave velocity anomalies in the mantle derived from seismic tomography help to distinguish thermal signatures from those of partial melt, volatiles, and compositional variations. Here we use seismic data from SW Europe and NW Africa, spanning the region between the Pyrenees and the Canaries, in order to obtain a new S-SKS relative arrival-time tomographic model of the upper mantle below Iberia, Western Morocco, and the Canaries. Similar to previous P wave tomographic results, the S wave model provides evidence for (1) subvertical upper-mantle low-velocity structures below the Canaries, Atlas Ranges, and Gibraltar Arc, which are interpreted as mantle upwellings fed by a common lower-mantle source below the Canaries; and (2) two low-velocity anomalies below the eastern Rif and Betics that we interpret as the result of the interaction between quasi-toroidal mantle flow induced by the Gibraltar slab and the mantle upwelling behind it. The analysis of teleseismic P wave and S wave arrival-time residuals and the conversion of the low-velocity anomalies to temperature variations suggest that the upwellings in the upper mantle below the Canaries, Atlas Ranges, and Gibraltar Arc system may be solely thermal in nature, with temperature excesses in the range ~100–350 °C. Our results also indicate that local partial melting can be present at lithospheric depths, especially below the Atlas Ranges. The locations of thermal mantle upwellings are in good agreement with those of thinned lithosphere, moderate to high heat-flow measurements, and recent magmatic activity at the surface.

We present a review of the analogue modelling method, which has been used for 200 years, and continues to be used, to investigate geological phenomena and geodynamic processes. We particularly focus on the following four components: (1) the different fundamental modelling approaches that exist in analogue modelling; (2) the scaling theory and scaling of topography; (3) the different materials and rheologies that are used to simulate the complex behaviour of rocks; and (4) a range of recording techniques that are used for qualitative and quantitative analyses and interpretations of analogue models. Furthermore, we apply these four components to laboratory-based subduction models and describe some of the issues at hand with modelling such systems. Over the last 200 years, a wide variety of analogue materials have been used with different rheologies, including viscous materials (e.g. syrups, silicones, water), brittle materials (e.g. granular materials such as sand, microspheres and sugar), plastic materials (e.g. plasticine), visco-plastic materials (e.g. paraffin, waxes, petrolatum) and visco-elasto-plastic materials (e.g. hydrocarbon compounds and gelatins). These materials have been used in many different set-ups to study processes from the microscale, such as porphyroclast rotation, to the mantle scale, such as subduction and mantle convection. Despite the wide variety of modelling materials and great diversity in model set-ups and processes investigated, all laboratory experiments can be classified into one of three different categories based on three fundamental modelling approaches that have been used in analogue modelling: (1) The external approach, (2) the combined (external+internal) approach, and (3) the internal approach. In the external approach and combined approach, energy is added to the experimental system through the external application of a velocity, temperature gradient or a material influx (or a combination thereof), and so the system is open. In the external approach, all deformation in the system is driven by the externally imposed condition, while in the combined approach, part of the deformation is driven by buoyancy forces internal to the system. In the internal approach, all deformation is driven by buoyancy forces internal to the system and so the system is closed and no energy is added during an experimental run. In the combined approach, the externally imposed force or added energy is generally not quantified nor compared to the internal buoyancy force or potential energy of the system, and so it is not known if these experiments are properly scaled with respect to nature. The scaling theory requires that analogue models are geometrically, kinematically and dynamically similar to the natural prototype. Direct scaling of topography in laboratory models indicates that it is often significantly exaggerated. This can be ascribed to (1) The lack of isostatic compensation, which causes topography to be too high. (2) The lack of erosion, which causes topography to be too high. (3) The incorrect scaling of topography when density contrasts are scaled (rather than densities); In isostatically supported models, scaling of density contrasts requires an adjustment of the scaled topography by applying a topographic correction factor. (4) The incorrect scaling of externally imposed boundary conditions in isostatically supported experiments using the combined approach; When externally imposed forces are too high, this creates topography that is too high. Other processes that also affect surface topography in laboratory models but not in nature (or only in a negligible way) include surface tension (for models using fluids) and shear zone dilatation (for models using granular material), but these will generally only affect the model surface topography on relatively short horizontal length scales of the order of several mm across material boundaries and shear zones, respectively.

Overriding plate topography provides constraints on subduction zone geodynamics. We investigate its evolution using fully dynamic laboratory models of subduction with techniques of stereoscopic photogrammetry and particle image velocimetry. Model results show that the topography is characterized by an area of forearc dynamic subsidence, with a magnitude scaling to 1.44-3.97 km in nature, and a local topographic high between the forearc subsided region and the trench. These topographic features rapidly develop during the slab free-sinking phase and gradually decrease during the steady state slab rollback phase. We propose that they result from the variation of the vertical component of the trench suction force along the subduction zone interface, which gradually increases with depth and results from the gradual slab steepening during the initial transient slab sinking phase. The downward mantle flow in the nose of the mantle wedge plays a minor role in driving forearc subsidence.

Since the first published laboratory models from Sir James Hall in 1815, analogue and numerical geodynamic modelling have become widely used as they provide qualitative and quantitative insights into a broad range of geological processes. To celebrate the 200th anniversary of geodynamic modelling, this special issue gathers review works and recent studies on analogue and numerical modelling of tectonic and geodynamic processes, as an opportunity to present some of the milestones and recent breakthroughs in this field, to discuss potential issues and to highlight possible future developments.

Backarc extension is a characteristic feature of many narrow subduction zones. Seismological and geochemical studies imply the occurrence of mantle flow around the narrow subducting slabs. Previous 3D models suggested that backarc extension is related to subduction-induced toroidal mantle flow. The physical viability of this mechanism, however, has never been tested using laboratory-based geodynamic models. In this work, we present dynamic laboratory models of progressive subduction in three-dimensional (3D) space that were carried out to test this mechanism. To achieve this, we have used a stereoscopic Particle Image Velocimetry (sPIV) technique to map simultaneously overriding plate deformation and 3D subduction-induced mantle flow underneath and around an overriding plate. The results show that the strain field of the overriding plate is characterized by the localization of an area of maximum extension within its interior (at 300–500 km from the trench). The position of maximum extension closely coincides (within ∼2 cm, scaling to 100 km) with that of the maximum trench-normal horizontal mantle velocity and velocity gradient measured at a scaled depth of 15–25 km below the base of the overriding plate, and the maximum horizontal gradient of the vertical mantle velocity gradient. We propound that in narrow subduction zones backarc extension in the overriding plate is mainly a consequence of the trench-normal horizontal gradients of basal drag force at the base of the overriding plate. Such shear force gradients result from a horizontal gradient in velocity in the mantle below the base of the lithosphere induced by slab rollback. Calculations based on our models indicate a tensional horizontal trench-normal deviatoric stress in the backarc region scaling to ∼28.8 MPa, while the overriding plate trench-normal stress resulting from the horizontal component of the trench suction force is about an order of magnitude smaller, scaling to ∼2.4–3.6 MPa.

The impact of slab width W (i.e., trench-parallel extent) on subduction-induced upper mantle flow remains uncertain. We present a series of free subduction analog models where W was systematically varied to upscaled values of 250–3600 km to investigate its effect on subducting plate kinematics and upper mantle return flow around the lateral slab edges. We particularly focused on the upwelling component of mantle flow, which might promote decompression melting and could thereby produce intraplate volcanism. The models show that W has a strong control on trench curvature and on the trench retreat, subducting plate, and subduction velocities, generally in good agreement with previous modeling studies. Upper mantle flow velocity maps produced by means of a stereoscopic particle image velocimetry technique indicate that the magnitude of the subduction-induced mantle flow around the lateral slab edges correlates positively with the product of W and trench retreat velocity. For all models an important upwelling component is always produced close to the lateral slab edges, with higher magnitudes for wider slabs. The trench-parallel lateral extent of this upwelling component is the same irrespective of W, but its maximum magnitude gets located closer to the subducting plate in the trench-normal direction and it is more focused when W increases. For W ≤ 2000 km the upwelling occurs laterally (in the trench-parallel direction) next to the subslab domain and the mantle wedge domain, while for W ≥ 2000 km it is located only next to the subslab domain and focuses closer to the trench tip, because of stronger poloidal flow in the mantle wedge extending laterally.

We present analogue models of free subduction in which we investigate the three-dimensional (3-D) subduction-induced mantle flow focusing around the slab edges. We use a stereoscopic Particle Image Velocimetry (sPIV) technique to map the 3-D mantle flow on 4 vertical cross-sections for one experiment and on 3 horizontal depth-sections for another experiment. On each section the in-plane components are mapped as well as the out-of-plane component for several experimental times. The results indicate that four types of maximum upwelling are produced by the subduction-induced mantle flow. The first two are associated with the poloidal circulation occurring in the mantle wedge and in the sub-slab domain. A third type is produced by horizontal motion and deformation of the frontal part of the slab lying on the 660 km discontinuity. The fourth type results from quasi-toroidal return flow around the lateral slab edges, which produces a maximum upwelling located slightly laterally away from the sub-slab domain and can have another maximum upwelling located laterally away from the mantle wedge. These upwellings occur during the whole subduction process. In contrast, the poloidal circulation in the mantle wedge produces a zone of upwelling that is vigorous during the free falling phase of the slab sinking but that decreases in intensity when reaching the steady-state phase. The position of the maximum upward component and horizontal components of the mantle flow velocity field has been tracked through time. Their time-evolving magnitude is well correlated to the trench retreat rate. The maximum upwelling velocity located laterally away from the subducting plate is ∼18–24% of the trench retreat rate during the steady-state subduction phase. It is observed in the mid upper mantle but upwellings are produced throughout the whole upper mantle thickness, potentially promoting decompression melting. It could thereby provide a source for intraplate volcanism, such as Mount Etna in the Mediterranean, the Chiveluch group of volcanoes in Kamchatka and the Samoan hotspot near Tonga.

International audience; The growth of relief in active tectonic areas is mainly controlled by the interactions between tectonics and surface processes (erosion and sedimentation). The study of long-lived morphologic markers formed by these interactions can help in quantifying the competing effects of tectonics, erosion and sedimentation. In regions experiencing active extension, river-long profiles and faceted spurs (triangular facets) can help in un- derstanding the development of mountainous topography along normal fault scarps. In this study, we devel- oped analogue experiments that simulate the morphologic evolution of a mountain range bounded by a normal fault. This paper focuses on the effect of the fault slip rate on the morphologic evolution of the foot- wall by performing three analogue experiments with different fault slip rates under a constant rainfall rate. A morphometric analysis of the modelled catchments allows comparing with a natural case (Tunka half- graben, Siberia). After a certain amount of fault slip, the modelled footwall topographies of our models reaches a dynamic equilibrium (i.e., erosion balances tectonic uplift relative to the base level) close to the fault, whereas the topography farther from the fault is still being dissected due to regressive erosion. We show that the rates of vertical erosion in the area where dynamic equilibrium is reached and the rate of re- gressive erosion are linearly correlated with the fault throw rate. Facet morphology seems to depend on the fault slip rate except for the fastest experiment where faceted spurs are degraded due to mass wasting. A stream-power law is computed for the area wherein rivers reach a topographic equilibrium. We show that the erosional capacity of the system depends on the fault slip rate. Finally, our results demonstrate the pos- sibility of preserving convex river-long profiles on the long-term under steady external (tectonic uplift and rainfall) conditions.

[1] We present new results on the long-term throw rates of active normal faults in the North Baikal Rift (NBR), eastern Siberia, based on a statistical analysis of triangular faceted scarps. Fault-bounded ridges in the NBR display typical morphologies with several contiguous facets separated by fault-perpendicular catchments. Over a range of 20 fault segments analyzed, triangular facet heights vary from ∼200 to >900 m. As fault scarps have been developing under similar long-term climatic conditions, we infer that the scatter in mean facet height arises from long-term differences in fault throw rate. We compare the morphology of NBR facets with results obtained in a previously published numerical model of facet growth. Using facet height as an input, model results provide estimates of the long-term fault throw rate. NBR throw rates vary between 0.2 and 1.2 mm yr−1. The throw rates are then compared with the cumulated throw, which has been constrained by geophysical and stratigraphic data in the basins. This provides an estimate of the age of fault and basin initiation. We show that the modern stage of basin development started circa 3 Myr ago, except for the North Baikal basin (∼8 Ma). Our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage.

Upper-mantle upwellings are often invoked as the cause of Cenozoic volcanism in the Ibero-western Maghreb region. However, their nature, geometry and origin are unclear. This study takes advantage of dense seismic networks, which cover an area extending from the Pyrenees in the north to the Canaries in the south, to provide a new high-resolution P-wave velocity model of the upper-mantle and topmost lower-mantle structure. Our images show three subvertical upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc, which appear to be rooted beneath the upper-mantle transition zone (MTZ). Two other mantle upwellings beneath the eastern Rif and eastern Betics surround the Gibraltar subduction zone. We propose a new geodynamic model in which narrow upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc rise from a laterally-propagating layer of material below the MTZ, which in turn is fed by a common deep source below the Canaries. In the Gibraltar region, the deeply rooted upwelling interacts with the Gibraltar slab. Quasi-toroidal flow driven by slab rollback induces the hot mantle material to flow around the slab, creating the two low-velocity anomalies below the eastern Betics and eastern Rif. Our results suggest that the Central Atlantic plume is a likely source of hot mantle material for upper-mantle upwellings in the Ibero-western Maghreb region.