Incipient mantle delamination, active tectonics and crustal thickening in Northern Morocco: Insights from gravity data and numerical modeling

The Betic-Rif orocline surrounding the Alboran Sea, the westernmost tip of the Mediterranean Sea, accommodates the NW–SE convergence between the Nubia and Eurasia plates. Recent GPS observations indicate a ∼4 mm/yr SW motion of the Rif Mountains, relative to stable Nubia, incompatible with a simple...

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Bibliographic Details
Published in:Earth and planetary science letters 2016-11, Vol.454, p.113-120
Main Authors: Baratin, Laura-May, Mazzotti, Stéphane, Chéry, Jean, Vernant, Philippe, Tahayt, Abdelilah, Mourabit, Taoufik
Format: Article
Language:English
Subjects:
Brittleness
Crusts
delamination
Earth Sciences
geodesy
Geophysics
Gravitation
gravity
Lithosphere
Mantle
Mathematical models
Mountains
numerical modeling
Sciences of the Universe
Tectonics
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Summary:The Betic-Rif orocline surrounding the Alboran Sea, the westernmost tip of the Mediterranean Sea, accommodates the NW–SE convergence between the Nubia and Eurasia plates. Recent GPS observations indicate a ∼4 mm/yr SW motion of the Rif Mountains, relative to stable Nubia, incompatible with a simple two-plate model. New gravity data acquired in this study define a pronounced negative Bouguer anomaly south of the Rif, interpreted as a ∼40 km-thick crust in a state of non-isostatic equilibrium. We study the correlation between these present-day kinematic and geodynamic processes using a finite-element code to model in 2-D the first-order behavior of a lithosphere affected by a downward normal traction (representing the pull of a high-density body in the upper mantle). We show that intermediate viscosities for the lower crust and uppermost mantle (1021–1022Pas) allow an efficient coupling between the mantle and the base of the brittle crust, thus enabling (1) the conversion of vertical movement, resulting from the downward traction, to horizontal movement and (2) shortening in the brittle upper crust. Our results show that incipient delamination of the Nubian continental lithosphere, linked to slab pull, can explain the present-day abnormal tectonics, contribute to the gravity anomaly observed in northern Morocco, and give insight into recent tectonics in the Western Mediterranean region. •2D numerical modeling of a lithosphere affected by the pull of a high-density body.•Intermediate viscosities in lower crust and uppermost mantle are needed.•Present-day abnormal tectonics and gravity anomaly explained by slab pull.•Incipient delamination of the Nubian continental lithosphere is proposed.
ISSN:0012-821X
1385-013X
DOI:10.1016/j.epsl.2016.08.041