Modes of propagation of continental break-up and associated oblique rift structures

Anthony Jourdon (1, 2) , Laetitia Le Pourhiet (2) , Frédéric Mouthereau (1) , Dave A. May (3, 4)

1 GET - Géosciences Environnement Toulouse
2 iSTeP - Institut des Sciences de la Terre de Paris
3 Institute of Geophysics [ETH Zürich]
4 University of Oxford

8 V-shaped oceanic propagators are widespread around the world. Their geometry combined with 9 magnetic anomalies associated to their opening shows at first order that ridge propagation in the third 10 dimension occurs by pulses. In this study we use 3D thermomechanical numerical models to show 11 how oblique kinematic boundary conditions control both the intracontinental rift development and the 12 oceanic ridge propagation. To do so, we apply a shortening velocity boundary condition in the 13 direction perpendicular to the extension for "strong" and "weak" crustal rheologies. Numerical models 14 results highlight that three ridge propagation modes can occur. For low out of plane velocities (12% to 15 15% of the extension rate), the ridge propagation is fast (>1.5 cm/yr) and straight. Higher shortening 16 velocities (15% to 17%) lead to a ridge propagation by pulses alternating between fast propagation 17 (~1.5 cm/yr) and stalling phases. Finally, for higher velocities (17% to 20%) a ridge jump propagation 18 mode occurs, localizing a new spreading centre between 100 and 200 km far from the initial ridge. We 19 also show that ridge propagation phases are associated with dip-slip dominated deformation while 20 stalling phases are dominated by strike-slip deformation. These deformation regimes are marked by 21 structures reorientation while kinematic boundary conditions remain constant. We discuss these results 22 in term of plate tectonics reconstructions and regional geological studies. 23

Domaines: Sciences de la Terre

Anthony Jourdon, Laetitia Le Pourhiet, Frédéric Mouthereau, Dave A. May. Modes of propagation of continental break-up and associated oblique rift structures. Journal of Geophysical Research : Solid Earth, 2020, 125 (9), ⟨10.1029/2020JB019906⟩. ⟨hal-02985979⟩