The Betic Ophiolites and the Mesozoic Evolution of the Western Tethys

Abstract

Abstract:The Betic Ophiolites consist of numerous tectonic slices, metric to kilometric in size, of eclogitized mafic and ultramafic rocks associated to oceanic metasediments, deriving from the Betic oceanic domain. The outcrop of these ophiolites is aligned along 250 km in the Mulhacén Complex of the Nevado-Filábride Domain, located at the center-eastern zone of the Betic Cordillera (SE Spain). According to petrological/geochemical inferences and SHRIMP (Sensitive High Resolution Ion Micro-Probe) dating of igneous zircons, the Betic oceanic lithosphere originated along an ultra-slow mid-ocean ridge, after rifting, thinning and breakup of the preexisting continental crust. The Betic oceanic sector, located at the westernmost end of the Tethys Ocean, developed from the Lower to Middle Jurassic (185-170 Ma), just at the beginning of the Pangaea break-up between the Iberia-European and the Africa-Adrian plates. Subsequently, the oceanic spreading migrated northeastward to form the Ligurian and Alpine Tethys oceans, from 165 to 140 Ma. Breakup and oceanization isolated continental remnants, known as the Mesomediterranean Terrane, which were deformed and affected by the Upper Cretaceous-Paleocene Eo-Alpine high-pressure metamorphic event, due to the intra-oceanic subduction of the Jurassic oceanic lithosphere and the related continental margins. This process was followed by the partial exhumation of the subducted oceanic rocks onto their continental margins, forming the Betic and Alpine Ophiolites. Subsequently, along the Upper Oligocene and Miocene, the deformed and metamorphosed Mesomediterranean Terrane was dismembered into different continental blocks collectively known as AlKaPeCa microplate (Alboran, Kabylian, Peloritan and Calabrian). In particular, the Alboran block was displaced toward the SW to occupy its current setting between the Iberian and African plates, due to the Neogene opening of the Algero-Provençal Basin. During this translation, the different domains of the Alboran microplate, forming the Internal Zones of the Betic and Rifean Cordilleras, collided with the External Zones representing the Iberian and African margins and, together with them, underwent the later alpine deformation and metamorphism, characterized by local differences of P-T (Pressure-Temperature) conditions. These Neogene metamorphic processes, known as Meso-Alpine and Neo-Alpine events, developed in the Nevado-Filábride Domain under Ab-Ep amphibolite and greenschists facies conditions, respectively, causing retrogradation and intensive deformation of the Eo-Alpine eclogites.

Geology of the Eastern Prebetic Zone at the Jumilla region (SE Iberia)

“…This agrees with regional stratigraphic and structural evidences along the Eastern Prebetic Zone supporting the existence of a Mesozoic phase of extension (De Ruig, 1995;García-Hernández et al, 1989;Pedrera, Marín-Lechado, Galindo-Zaldívar, & García-Lobón, 2014;Vilas et al, 2003). However, ophiolites Middle Jurassic in age outcropping in the Internal Betic Zone demonstrates that the Southern Iberian margin was already a passive margin with the oceanic crust at this time (Puga et al, 2011). Extension in the South Iberian margin which took place between the Lower and Middle Jurassic was clearly connected with the opening of the Central Atlantic Ocean to the west (De Jong, 1990;Srivastava et al, 1990).…”

Lateral variations of pressure-temperature evolution in non-cylindrical orogens and 3-D subduction dynamics: the Betic-Rif Cordillera example

“…The Mecina and the Filabres shear zones carry the Alpujárride Complex in their hanging-wall and the eclogite-facies Bédar-Macael unit in their footwall, showing again a gap of pressure with higher pressure downward (Jabaloy et al, 1993;Martinez-Martinez and Azañón, 2002;. Although the peak conditions in the three main Nevado-Filábride units are similar according to the recent study of Santamaria-Lopez et al (2019) the basal contact of the Bédar-Macael unit brings marbles, metabasites and ultramafic rocks of oceanic origin (Puga et al, 1995(Puga et al, , 2017 on top of continental material and was thus a thrust in the first place, before the extensional reactivation (García-Dueñas et al, 1988Jabaloy et al, 1993).…”

Two Tertiary metamorphic events recognized in high‐pressure metapelites of the Nevado‐Filábride Complex (Betic Cordillera, S Spain)

“…Presently, two unit divisions of the NFC are used widely. One division concerns the Mulhacén and underlying Veleta units and is based either on an erosion surface between the two units, that is overlain by conglomerates (Sanz de Galdeano, López‐Garrido, & Santamaría‐López, ), or ophiolites only existing in the Mulhacén unit (Puga et al., ). The other division includes (from bottom to the top) the Ragua (or ~Veleta), the Calar Alto (or ~lower part of Mulhacén) and the Bédar‐Macael (or ~upper part of Mulhacén) units and differences in metamorphic features (Martínez‐Martínez, Soto, & Balanyá, ) and were, thus, adopted by us (Figure ).…”