HR: 0800h
AN: T21C-0507    [Abstracts]
TI: Thermal Structure and Tectono-Metamorphic Evolution of the Alboran Domain. New Insights From the Rif belt (Northern Morocco) and Correlations With the Betics (Southern Spain)
AU: * Negro, F
EM: negro@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75005 France
AU: Beyssac, O
EM: beyssac@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75005 France
AU: Goffe, B
EM: goffe@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure, 24 rue Lhomond, Paris, 75005 France
AU: Saddiqi, O
T21C-0507 AF: Departement de Geologie, Faculte des Sciences, Km 8, Route d'El Jadida, Casablanca, BP 5366 Morocco
AU: Bouybaouene, M
T21C-0507 AF: Departement de Geologie, Faculte des Sciences, 4 Avenue Ibn Battouta, Rabat, BP 1014 Morocco
AB: The Betico-Rifan Cordilleras represent the western termination of the Alpine Mediterranean orogen. The internal zone of this orogen is the Alboran Domain which consists in a complex stacking of metamorphic nappes including, locally, mantle-derived bodies: the Ronda and Beni Bousera peridotites. In order to assess the tectono-metamorphic evolution of theses nappes and their relation with the underlying peridotites, we have combined RSCM (Raman spectroscopy of carbonaceous material) thermometry and P-T estimates based on chlorite-phengite local equilibria together with a careful analysis of ductile deformation.
In the inner Rif, the lower units (lower Sebtides) of the Alboran Domain are directly on top of the Beni Bousera peridotites. Our study shows that peak T was reached during thinning of these units, and that heating continued after this event. A Miocene thermal imprint is also recorded at the base of the upper units of the Alboran Domain (Ghomarides) and evidenced by an increase of T coeval with resetting of K-Ar ages.
Retrograde P-T paths in the HP-LT units of the Sebtide Complex also agree with this thermal structure. The units located near the peridotites experienced heating during final decompression stages whereas the more distant units underwent mostly isothermal decompression. In addition analysis of ductile deformation shows that the whole complex was exhumed in a single tectonic event characterized by N-S to NW-SE stretching and top-to-the-N senses of shear.
The same approach in the equivalent units (Alpujarrides) from Western Betics evidences a very similar thermal structure over the Ronda peridotites but tectonic dismembering of the orogenic prism was stronger in the Betics compared to the Rif.
Finally, analysis of these observations at orogenic scale shows that the Alboran Domain underwent a strong thermal event during the Early Miocene. This event can be interpreted as the result of ascending hot mantle units coeval with thinning of the whole crustal sequence during late orogenic extension.
DE: 3625 Petrography, microstructures, and textures
DE: 3660 Metamorphic petrology
DE: 8030 Microstructures
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Tectonophysics [T]
MN: Fall Meeting 2005