Earth and Planetary Science Letters 501 (2018) 13–23 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Towards subduction inception along the inverted North African margin of Algeria? Insights from thermo-mechanical models Hamai Lamine a,b , Petit Carole b,∗ , Le Pourhiet Laetitia c , Yelles-Chaouche Abdelkarim a , Déverchère Jacques d , Beslier Marie-Odile b , Abtout Abdeslam a a Centre de Recherches en Astronomie Astrophysique et Géophysique, Route de l’Observatoire, BP 63, Algiers, Algeria b Université Côte d’Azur, CNRS, OCA, IRD, Geoazur, France c Sorbonne Université, CNRS-INSU, Institut des Sciences de la Terre Paris, ISTeP UMR 7193, F-75005 Paris, France d Domaines Océaniques, Institut Européen de la Mer, CNRS-UBO, Technopôle Brest-Iroise, Place Nicolas Copernic, F-29280 Plouzané, France a r t i c l e i n f o a b s t r a c t Article history: Received 1 March 2018 Received in revised form 25 July 2018 Accepted 15 August 2018 Available online xxxx Editor: J.P. Avouac Keywords: numerical modeling passive margin inversion subduction initiation Northern Algeria While ocean subduction at continental margins is a prominent process of plate tectonics, understanding how and where it begins is still being debated, especially because examples of emerging ocean– continent subduction in the world are rare. Northern Algeria is currently undergoing a slow compression deformation due to the ongoing African–Eurasian convergence. Active compressional seismic activity recorded both on land and at sea indicates that the margin might be transitioning from a passive stage to an active one. In order to test this hypothesis, we perform thermo-mechanical models of margin inversion. Varying thermal and rheological parameters as well as the geometry of the margin boundary, we find that tectonic inversion of a young passive margin localizes at the margin toe only if the latter is strongly heated (i.e., with an abrupt thermal gradient between oceanic and continental lithospheres); otherwise, deformation propagates into the weak, hot oceanic lithosphere. The presence of a thinned continental crust at the ocean–continent transition favors either subduction of the oceanic lithosphere when the transition zone plunges towards the continent, or an indentation of the lower continental crust by the oceanic lithosphere when the transition zone is vertical. If the oceanic lithosphere is directly in contact with the continental margin, subduction-like deformation occurs during the early stages of the model but rapidly gives place to intra-oceanic buckling and faulting. Comparing the results of the simulation to the active tectonic structures of the Algerian margin, we conclude that both processes (emerging subduction or indentation) are possible and that the presence of a thermal anomaly beneath the thinned continental margin is probable, in relation with slab rupture at depth or with other thermal weakening processes.  2018 Elsevier B.V. All rights reserved. 1. Introduction North Algeria is currently undergoing a slow compressional de- formation due to the convergence between Africa and Eurasia. Horizontal movements resulting from this convergence are today absorbed in large part by the deformation of the North Algerian margin (Frizon de Lamotte et al., 2011), as evidenced by the seis- micity recorded both on land and at sea (Meghraoui et al., 2004). Part of this deformation (estimated at one third or half of the total deformation, i.e., 1 to 2 mm yr −1 according to Serpelloni et al., 2007) is located near the margin toe and results into the * Corresponding author. E-mail address: petit@geoazur.unice.fr (C. Petit). downward bending of the oceanic plate against the continental plate, with an isostatic signature similar to that of an active mar- gin (Hamai et al., 2015). The North African margin in Algeria can therefore be considered as in a transitional stage between active and passive margin settings and is ideally suited to study the way subduction initiates at continental margins. A large number of studies have focused on the parameters con- trolling subduction inception (e.g., Cloetingh et al., 1982; Goren et al., 2008; Hall et al., 2003; Leng and Gurnis, 2011; Marques et al., 2014; Niu et al., 2003; Stern, 2004; Stern and Gerya, 2017; Toth and Gurnis, 1998). For instance, Stern (2004) examined how subductions can theoretically initiate depending on the far-field kinematic conditions (“induced” subduction) or on local (body) forces (“spontaneous” subduction). A type of spontaneous subduc- tion occurs when the lithosphere reaches negative buoyancy due https://doi.org/10.1016/j.epsl.2018.08.028 0012-821X/ 2018 Elsevier B.V. All rights reserved.