Cenozoic magmatism of the valencia trough (western mediterranean): Relationship between structural evolution and volcanism ∗

Abstract

The Cenozoic magmatism of the Valencia trough is characterized by the existence of two volcanic cycles. The first cycle (Early Miocene-Middle Miocene) comprises calc-alkaline rocks which have been recognized in the central to eastern offshore areas and in Mallorca. The second cycle (Middle Miocene to Recent) is represented mainly by poorly differentiated alkaline rocks which are predominantly distributed along the Iberian margin of the Valencia trough. In accordance with the inferred structural evolution of the Valencia trough, petrological and geochemical data, as well as volcanological evidence, we suggest that two different geodynamic environments existed during these magmatic cycles. The Early to Middle Miocene calc-alkaline volcanism developed under compressive tectonic conditions and seems to be associated with the northwestern dipping subduction of the African plate. In contrast, the Middle Miocene to Recent alkaline volcanism is associated with extensional tectonics and can be explained within the framework of a low volcanicity rift model. Three zones—Catalan, Valencian and Columbretes—each located at different parts of the rift structure, can be distinguished in the Middle Miocene to Recent volcanism. This intraplate volcanism results from partial melting, due to extension-driven decompression, with the largest degrees of melting in the centre of the Valencia trough (Columbretes volcanic zone). In the Catalan volcanic zone a progressive increase in the extension rate from the first to the last volcanic episode has occurred, favouring the interaction of two mantle sources.