Petrology, geochemistry and origin of the sierra de baza ophiolites (Betic cordillera, Spain)

Abstract

In this work we present for the first time a petrological-geochemical and genetic study of the Sierra de Baza ophiolites, which represent one of theophiolitic occurrences of the Betic Cordillera (Southern Spain). They are composed of ultramafic, mafic and sedimentary rocks, largely affected bothby ocean floor and polyphasic metamorphism during the Alpine orogeny. Ultramafic rocks are serpentinized lherzolites and harzburgites, whereas themetabasites are meta-gabbros and meta-basalts. On the whole, Sierra de Baza ophiolites show striking geochemical similarities with those from otherBetic occurrences, as well as with other Tethyan ophiolites of the Western Mediterranean (Calabria, Internal and External Ligurides, Platta, Corsica andWestern Alps). In particular, metabasites show petrological and geochemical features similar to the E-MORB magmatism of the Atlantic Ridge between45 and 63oN generated under ultra-slow spreading ridge conditions. This process originated a strip of few hundreds km of ocean floor at the western endof the Tethys, located SE of the Iberian-European margin during the Mesozoic. The inversion of the stress regime in the European-Iberian and Africangeodynamics, starting from the Late-Middle Cretaceous, caused subduction and metamorphism in the eclogite facies of oceanic slices that were partiallyexhumed on the continental margin, forming the Betic Ophiolites. These ophiolites were disarticulated and dismembered as a result of the shift towardsSW of the Alboran continental block, progressively separated from the AlKaPeCa (Alboran, Kabilias, Peloritani, Calabria) microplate, finally occupyingtheir current position in the Betic Internal Zones.