Contrasting structural and P-T evolution of tectonic units in the southeastern Betics: Key for understanding the exhumation of the Alboran Domain HP/LT crustal rocks (western Mediterranean)

Thermobarometry using mica-chlorite local equilibria and structural analysis of three tectonic units of the Alpujarride complex in the southeastern Betics indicate that rocks that underwent low-pressure/low-temperature metamorphism are found below higher-grade blueschist facies rocks. Moreover, the high-pressure/low-temperature (HP/LT) units underwent contrasting (P-T) and structural evolutions. The structurally highest unit was exhumed in a typical postorogenic high-temperature geothermal context in the andalusite stability field, while the intermediate unit was exhumed following a cooling and decompression P-T path within the kyanite stability field. The superposition of the three units occurred during the lower Miocene related with north directed brittle-ductile shear zones and associated north vergent overturned folds, after postorogenic exhumation of the top unit. The coexistence of thrusting with lower and middle Miocene brittle extensional systems active in shallower levels of the Alboran orogenic wedge implies that extension was synorogenic. These data strengthen the hypothesis that rocks thinned by postorogenic extension during the latest Oligocene and lower Miocene were entrained in the lower to middle Miocene Alboran orogenic wedge.