Sequential development of the metamorphic aureole beneath the Ronda peridotites and its bearing on the tectonic evolution of the Betic Cordillera

• Published in: Tectonophysics 1997-09, Vol.279 (1), p.227-252
• Main Authors: Tubía, JoséM., Cuevas, Julia, Ibarguchi, JoséI.Gil
• Format: Article
• Language: English
• Subjects: eclogite; metamorphic sole; Ronda peridotites; syn-collisional exhumation
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/S0040-1951(97)00124-8

At Sierra Alpujata (western Betic Cordillera, Spain), the Ronda peridotites overlay a metamorphic sole of felsic composition formed during the hot overthrusting of the ultrabasic rocks over the Ojén nappe. The metamorphic sole evolved from an initial eclogite facies metamorphism ( P ≥ 1.7 GPa; T = 790°C) to low-pressure ( P ≤ 300 MPa) high-temperature ( T ∼ 600°C) conditions. The active movement zone migrated downwards in the metamorphic sole as temperatures decreased during this exhumation process: high temperatures led to strain localization along the 200-m-thick ductile shear zone that forms the uppermost level of the metamorphic sole, and brittle to ductile deformations achieved at temperatures below 500°C are concentrated in the basal contact of the metamorphic sole. The maintenance of a common kinematics, with ENE-trending stretching lineations and top-to-the-ENE shearing, along the high-temperature and the low-temperature shear zones suggests that the main part of the exhumation process was performed before the overall north-south convergence of the Iberian and African plates. The subduction of the Ojén nappe, a wedge of subcontinental lithosphere, below the orogenic lherzolites of Ronda probably gave rise to the syn-collisional exhumation of the metamorphic sole and then to the slab breakoff and sinking of the subducted lithospheric mantle.