Large-scale polyphase deformation of a coherent HP/LT metamorphic unit: the Mulhacen Complex in the eastern Sierra de los Filabres (Betic Zone, SE Spain)

Abstract

This paper elucidates the large-scale polyphase deformation history of the Mulhacen Complex, the partially overprinted HP/LT metamorphic nappe complex in the Betic Zone of southeastern Spain, by tying zones of concentrated small-scale and mesoscopic deformation to large-scale structures, which could be mapped out due to excellent exposure. Small-scale structures show that progressively younger deformation was increasingly less homogeneous and became progressively more concentrated in zones. The original D1mulh- D2mulh distribution of lithologic units and main tectonic units was disrupted during subsequent polyphase deformation. During a third phase of penetrative deformation (D3mulh), S-SW vergent folding and associated S-SW ward thrusting occurred; the most intense folding and cleavage development took place in the vicinity of these thrusts. During D3mulh, a level in the top of the lowest nappe of the Mulhacen Complex acted as floor thrust of the imbrications. Mapping and structural analysis showed that during subsequent deformation this zone was reactivated and that deformation was concentrated below the detachment. The last phase of deformation (D7mulh) did not result in penetrative deformation but in approximately N-S trending subvertical faults and associated similarly oriented flexures and large-scale open folds. Tortonian sediments show that D6mulh occurred before, and D7mulh, at least partly, after their deposition.