Upper-crustal extension during oblique collision: The Temsamane extensional detachment (eastern Rif, Morocco)

摘要

The subducted North Maghrebian passive margin was exhumed in the Tortonian (11-7Ma) by an upper-crustal brittle-ductile extensional detachment and brittle low-angle normal faults in a continental subduction transform setting. The Temsamane detachment in the eastern Rif is defined by a ductile shear zone approximately 100-m thick with a low-angle ramp geometry that cuts down into the Temsamane fold-nappe stack. The shear zone shows south-westward kinematics and separates lower-greenschist (≈400°C) metapelites of the Temsamane units below from the anchizone and diagenetic rocks (<300-200°C) of the Ketama-Aknoul units above. To the east, the detachment becomes brittle, branching into a listric-fan that cuts through 10-6Ma sediments and volcanoclastics in the Tres Forcas cape. Both the North Maghrebian and the South Iberian subducted passive margins were exhumed in the Betic and Rif branches of the Gibraltar arc by SW-directed brittle-ductile detachments during the late Miocene in an oblique collisional setting.