The structure and evolution of the lithosphere-asthenosphere boundary beneath the Atlantic-Transition Region

J. Fullea (1, 2) , J.C. Afonso (3) , M. Fernandez (2) , J. Verges (2) , H. Zeyen (4)

1 Dublin
2 Institute of Earth Sciences Jaume Almera
3 GEMOC - ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents
4 IDES - Interactions et dynamique des environnements de surface

The present-day thermal and compositional 3D structure of the lithosphere beneath the Atlantic-Mediterranean Transition Region and the lithosphere-asthenosphere interaction from Jurassic times to present has been studied The Atlantic-Mediterranean Transition Region comprises the western segment of the Africa-Eurasia plate boundary encompassing two main large scale tectonic domains the Gibraltar Arc System and the Atlas Mountains An integrated and self-consistent geophysical-petrological methodology (LitMod3D) has been applied that combines elevation gravity geoid surface heat flow and seismic data and allows modelling of compositional heterogeneities within the lithospheric mantle Our results reveal large variations in the depth of the Moho and the lithosphere-asthenosphere boundary (LAB) as well as a lack of spatial correlation between the thicknesses of these two boundaries The Moho essentially mimics the topography with depths ranging from similar to 10 km beneath the oceanic domains of the Atlantic abyssal plains and the Algerian Basin to >34 km in the Eastern Betics and Rif the High Atlas mountains and the Sahara Platform In contrast the LAB is shallower beneath the central and eastern Alboran Basin (similar to 70 km) and all along the High Middle and Anti Atlas (<100 km) coinciding with the loci of Cenozoic volcanism Deeper LAB depths are found along the central and western Betics and the Moroccan Atlantic margin (>140 km) with values exceeding 230 km beneath the Rif and the Sahara Platform The average bulk composition of the lithospheric mantle corresponds to that of a typical Tecton (i e Phanerozoic) domain with the exceptions of the Sahara Platform the Alboran Basin and Atlas Mountains Distinct mantle compositions are required in these areas to make model predictions and geophysical observables compatible It is proposed that the highly irregular LAB topography is the result of the superposition of three different geodynamic processes i) shortening and thickening related to NW-SE Iberia-Africa convergence lasting from Late Cretaceous to Recent ii) impingement of a baby-like mantle plume or small-scale convection beneath the High-Middle Atlas and Anti Atlas commencing in the mid Eocene and iii) slab roll-back or mantle delamination in the Betic-Rif-Alboran realm acting from early to late Miocene (C) 2010 Elsevier B V All rights reserved

Domaines: Sciences de la Terre

J. Fullea, J.C. Afonso, M. Fernandez, J. Verges, H. Zeyen. The structure and evolution of the lithosphere-asthenosphere boundary beneath the Atlantic-Transition Region. Lithos, 2010, 120 ((1-2)), pp.:74-95 (IF 3.303). ⟨hal-00467028⟩