ALBERT

Description: The basement of the Vera and Huercal Overa basins (southeastem Betics) is fonned by rocks ofthe Alboran Crustal Domain; a terrain which collided with the South-Iberian and Maghrebian continentalmargins in the Lower Miocene, resulting in the fonnation of the Gibraltar Are mountain chain. The Alpuja1Tide complex which occupies an intermediate structural position within the Alboran Domain, above the Nevado-Filabride and below the Malaguide complexes, includes at least three tectonic units in the southeastern Betics. From bottom to top in the slTuctural sequence, these units are Almagro, Almanzora and Variegato. The metapelitic rocks of these units show significative differences in their tectonic fabrics and in their P-T metamorphic paths. The lower Almagro unit underwent low-P/low-T metamorphism (300 oc and 3-4 kbar) and its metapelites are slates with no differentiated metamorphic fabric, which show two sets of spaced axial-plane cleavages. The intennediate Almanzora unit has two differentiated metamorphic fabrics. The oldest foliation (S,) preserved in quartz-rich domains of a crenulation cleavage (S ce) grew during high-P/low-T metamorphism (between 300 °C/12 kbar and 350 oC/6 kbar). The Scc cleavage deyeloped after an isobaric heating to 475 oc at 5 kbar and registers an initial isothennal decompression to 475 oc at 3 kbar followed by cooling to 300 oc at 2 kbar. A brittle spaced cleavage axial plane to N-vergent asymmetric folM cuts the S ce fabtic. At the top ofthe Alpujarride tectonic pile the Variegato unit, includes up to tlu·ee imbrications formed from top to bottom by gamet schists, fine"grained schists and Triassic carbonates. The main Scc foliation in the gamet schists grew during a nearly isothennal decompression between 500 oc at 8 kbar and 525 oc at 2 kbar. In the Variegato dark schists, the spaced crenulation cleavage associated to Nvergent folds is defined by muscovite and chlorite lepidoblasts and is overprinted by the growth of andalousite porphyroblasts. This assemblage equilibrated at 450-460 oc at 2 kbar. The Variegato fine-grained schists include a high-P/low-T Mg-carpholite-bearing assemblage, within pre-Scc quartz veins equilibrated at 8-10 kbar and approximately 400 °C. Furthermore, a chlorite + phengite + quartz assemblage defining the se relic foliation in lenticular domains of the scc cleavage shows local equilibria at 11 to 9 kbar at 400 °C. The superposition ofthese units was related with N-directed compressional brittle-ductile shear zones and associated N-vergent asymmetric folds, which were active at a late stage of the metamorphic evolution after coaxial ductile flattening of the Variegato and Almanzora units. The thrust pile that resulted from this late compressional event was later thinned by two consecutive brittle extensional systems with northward and southwestward tectonic transport. Final! y, these metamorphic rocks were exhumed to the surface in the core of E-W oriented anticlinal ridges, which developed during the Upper Neogene and the Quaternary. Folding and strike-slip faulting of the Miocene Alboran basin produced the present basin and range morphology of the southeastern Betics, which is characterised by the formation of isolated sedimentary basins in the synclines.

Description: We have analysed the thermobarometric equilibrium conditions reached during local equilibria among phengite + chlorite + quartz + water ± chloritoid ± garnet assemblages found in metapelites of the Ragua unit, the structurally-lowest tectonic unit outcropping in the Betics hinterland (southern Spain). Porphyroblast- deformation relationships show that lenticular domains preserved within the main foliation in the metapelites grew during a HP/LT prograde metamorphic event with thermal conditions of 320-450 °C and 12-14 kbar pressure. Hence, the Ragua unit subducted in a continental accretionary-wedge context, undergoing a tectonic evolution parallel to the one followed by the two other overlying Nevado-Filabride units.

Description: The Santi Petri dome (western Betics, southern Spain) shows a core-complex-like structure, where migmatitic gneisses and schists outcrop below low-grade slates and phyllites, all of which form the basement of the Neogene Málaga basin. The migmatites and schists suffered a coaxial-flattening event during isothermal decompression and were later exhumed by ductile ESE non-coaxial stretching. Further exhumation was achieved by W- to SW-transport brittle low-angle normal faulting. Subsequently these extensional structures were gently folded in the core of a NE/SW-oriented antiform during the Tortonian. Finally the Santi Petri domal geometry was accentuated by the interference of orthogonal high-angle faults with ENE–WSW and NNW–SSE orientation. This core-complex-like structure, formed by superposition of extensional and compressive tectonic events, does not represent a classical, purely extensional core complex, which shows that metamorphic structure and geometry are not decisive criteria to define a core-complex.

Description: The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the The Palomares Fault Zone (PFZ) is one of the main strike-slip brittle shear zones found in the Betics. It is segmented in several faults that have been active between the Upper Tortonian and present day. Data from drill cores in the Palomares area have permitted us to define the geometry and location of sedimentary depocentres related with the PFZ. These data show an eastward displacement between the Upper Tortonian to Messinian and the Pliocene–Quaternary sedimentary depocentres, towards the presently active Arteal fault, which bounds the western mountain front of Sierra Almagrera, showing that deformation along this fault zone has migrated towards the east, from the Palomares segment, with its main activity during the Upper Tortonian and Messinian, towards the Arteal fault, active during the Pliocene and Quaternary.