The Beni Bousera marbles, record of a Triassic-Early Jurassic hyperextended margin in the Alpujarrides-Sebtides units (Rif belt, Morocco)

The timing and process of exhumation the subcontinental peridotites Gibraltar Arc (Ronda, Beni Bousera) have been discussed extensively over last decades. In this work, we contribute to debate through first mapping, structural petrological analyses, SHRIMP U-Th-Pb dating high-grade marbles that crop out around Bousera antiform Alpujarrides-Sebtides units northern Rif (Morocco). These marbles, here termed (BBMs), instead being intercalations in granulitic envelope (kinzigites) peridotites, as previously described, form minor, dismembered within a ∼30 300 m thick mylonitic contact between kinzigites overlying gneisses Filali Unit (Filali–Beni Shear Zone, FBBSZ). They display silicate-rich dolomitic sandy-conglomeratic calcareous thinly bedded marble with interleaved biotite-rich schists. An unconformable contact, either stratigraphic or tectonic origin, underlying kinzigites, is observed locally. Pebbles detrital grains include K-feldspar, quartz, almandine garnet zircon. Peak mineral assemblages consist forsterite, Mg-Al-spinel, geikielite (MgTiO 3 ), phlogopite accessory zirconolite, baddeleyite srilankite dolomite marble, well scapolite, diopside, titanite graphite zircon calcite marble. characterize peak HT-LP metamorphic conditions close 700–750 °C, ≤4.5 kbar. FBBSZ includes minor ductile thrusts determine kinzigite horses slivers carried NW-ward marbles. Within latter, NNE-trending folds are conspicuous. Brittle, northward-dipping normal faults crosscut structures. Detrital cores from BBMs yield two age clusters ∼270 Ma ∼340 Ma, whereas their rims ∼21 ages. Correlations comparable settings other West Mediterranean Alpine belts discussed. compare Triassic carbonates deposited crustal Alpujarrides-Sebtides. assumed protoliths may onto extensional allochthons detachment Early Jurassic during incipient formation Alboran Domain continental margin. Thus, it concluded mantle rocks were exhumed shallow depth early rifting events responsible for birth Maghrebian Tethys.