Gueydan, F. and Pitra, P. and Afiri, A. and Poujol, M. and Essaifi, A. and Paquette, J.-L. (2015) Oligo-Miocene thinning of the Beni Bousera peridotites and their Variscan crustal host rocks, Internal Rif, Morocco. Tectonics, 34 (6). pp. 1244-1268.

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Abstract

Deciphering Variscan versus Alpine history in the Internal Rif system is a key to constrain the tectonic evolution of the Alboran domain and hence the geodynamics of the western Mediterranean system during the Cenozoic. This study focuses on the evolution of the metamorphic envelope of the Beni Bousera massif and its relation to the underlying peridotites. Combining structural geology, metamorphic petrology, and laser ablation inductively coupled plasma mass spectrometry U-Th-Pb dating of monazite, this study contributes to the understanding of the tectonic history of the western Internal Rif. The regional foliation (S2) is characterized by low pressure-high temperature (LP-HT) mineral assemblages and obliterates a former foliation (S1) developed along a Barrovian (medium pressure-medium temperature, MP-MT) metamorphic gradient. The dating of some metamorphic monazite grains from a micaschist and a migmatitic gneiss demonstrates that the crustal envelope of the peridotite recorded two distinct tectonometamorphic episodes. Data from monazite inclusions in S1 garnet suggest that the first event, D1, is older than 250-170 Ma and likely related to the Variscan collision, in agreement with the Barrovian type of the metamorphic gradient. The second event, D2, is Alpine in age (at circa 21 Ma) and corresponds to a strong lithosphere thinning allowing subsequent subcontinental mantle exhumation. Such a tectonic context provides an explanation for the LP-HT metamorphic gradient that is recorded in the regional foliation of the western Betic-Rif system. This extension is probably related to a subduction slab rollback in the western end of the Mediterranean realm during the Oligo-Miocene times. No evidence for a Tertiary high pressure/low temperature metamorphism has been identified in the studied area. ©2015. American Geophysical Union. All Rights Reserved.

Item Type: Article
Uncontrolled Keywords: Geochronology; Geodynamics; Inductively coupled plasma mass spectrometry; Laser ablation; Lead; Mass spectrometry; Monazite; Petrography; Petrology; Phosphate minerals; Tectonics, Beni Bousera peridotites; Betic-Rif orogen; La-ICP-MS; P-T pseudosection; Variscan, Structural geology, Alpine orogeny; crustal thinning; Hercynian orogeny; inductively coupled plasma method; metamorphism; Miocene; monazite; Oligocene; P-T conditions; peridotite; tectonic evolution; uranium series dating, Morocco; Rif
Subjects: Earth and Planetary Sciences
Divisions: SCIENTIFIC PRODUCTION > Earth and Planetary Sciences
Depositing User: Administrateur Eprints Administrateur Eprints
Last Modified: 31 Jan 2020 15:46
URI: http://eprints.umi.ac.ma/id/eprint/2893

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