Mantle exhumation at magma-poor rifted margins controlled by frictional shear zones - Model animations

• Main Authors: Theunissen, Thomas, Huismans, Ritske S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: figshare 2022
• Subjects: 40402 Geodynamics; FOS Earth and related environmental sciences; 80110 Simulation and Modelling; FOS Computer and information sciences; 40305 Marine Geoscience; Solid Earth Sciences; Indian; White Point; Antarc*; Antarctica; Newfoundland
• Online Access: https://dx.doi.org/10.6084/m9.figshare.17153264.v1; https://figshare.com/articles/media/Mantle_exhumation_at_magma-poor_rifted_margins_controlled_by_frictional_shear_zones_-_Model_animations/17153264/1

Here we present animations of 2-D geodynamic numerical modelling results of a-magmatic continental rifting and mantle exhumation published in Nature communication.This set of models shows sensitivity of model behavior during mantle exhumation to spreading rate (0.7; 0.8; 1.0; 1.5 cm/yr), fault strength (psw1=strong mantle shear zones; psw2=Intermediate strength mantle shear zones; psw3=Weak mantle shear zones; psw4, psw5=very strong shear zones), and thermal conductivity. The reference model M1 (Movies S1 and S2) is characterized by strong shear zones (psw1) and by a spreading rate of 1.5 cm/yr. All models include higher thermal conductivity of peridotites at low temperature except model SM15 (psw1_1.5_cst_k) where thermal conductivity is constant (2.25 W/m/K). Plastic strain weakening parameters (cohesion,angle of internal friction): psw1 20-20 Mpa 15-4º psw2 20-20 MPa 15-2º psw3 20-4 MPa 15-2º psw4 20-20 MPa 15-8º psw5 20-4 MPa 15-15º # Supplementary model names as found in the publication versus filenames: SM1 psw1_1.0.mp4 SM2 psw1_0.8.mp4 SM3 psw1_0.7.mp4 SM4 psw2_1.5.mp4 SM5 psw2_1.0.mp4 SM6 psw2_0.8.mp4 SM7 psw2_0.7.mp4 SM8 psw3_1.5.mp4 SM9 psw3_1.0.mp4 SM10 psw3_0.8.mp4 SM11 psw3_0.7.mp4 SM12 psw4_1.5.mp4 SM13 psw5_1.5.mp4 SM14 fw_1.5.mp4 SM15 psw1_1.5_cst_k.mp4 Movie descriptions: Movie S1. (MovieS1_M1_PTt_path.mp4): Large scale animation of the reference model M1 presented in the main text. Shown are upper crust (orange), middle crust (white), lower crust (light yellow), pre-rift upper-crust layer (purple), lithospheric mantle (green), sub-lithospheric mantle (yellow), overlay of weakened frictional-plastic shear zones (grey), overlay of strain rate higher than 10 -14 s -1 , contours of isotherms 350ºC, 550ºC, 800ºC, 1200ºC and 1300ºC. The Pressure-Temperature-time (PTt) history of the first peridotite ridge associated with crustal breakup in our model (Fig. 3A, ridge 1) is shown on the right side of the animation. The tracked point is drawn with a black contoured white point in the animation. Movie S2. (MovieS2_M1_zoom.mp4): Upper-crustal scale animation of the reference model M1 presented in the main text. Shown are upper crust (orange), middle crust (white), lower crust (light yellow), pre-rift upper-crust layer (purple), lithospheric mantle (green), sub-lithospheric mantle (yellow), overlay of weakened frictional-plastic shear zones (grey), overlay of strain rate higher than 10 -14 s -1 , contours of isotherms 350ºC and 550ºC. Abstract: The transition zone from continental crust to the mature mid-ocean ridge spreading centre of the Iberia-Newfoundland magma-poor rifted margins is mostly composed of exhumed mantle characterized by highs and domes with varying elevation, spacing and shape. The mechanism controlling strain localization and fault migration explaining the geometry of these peridotite ridges is poorly understood. Using forward geodynamic models we find that multiple out-of-sequence detachments with recurring dip reversal forming during magma-poor rifting and mantle exhumation as a consequence of the strength competition between weak frictional-plastic shear zones and the thermally weakened necking domain beneath the exhuming footwall explain geometry of these peridotite ridges. Model behaviour also shows that fault types and detachments styles vary with spreading rate and fault strength and confirm that these results can be directly compared to other magma poor passive margins such as along Antarctica-Australia and to ultra-slow mid-ocean spreading systems as the South-West Indian Ridge.