Geochronology, geochemistry and geodynamics of the Cabo de Gata volcanic zone, Southeastern Spain

Abstract

© 2014 Societa Geologica Italiana, Roma. New 40Ar/39Ar ages and major and trace element geochemistry of the middle-late Miocene Cabo de Gata volcanic complex, southeast Spain, indicate that the volcanic activity of the Cabo de Gata volcanic zone developed over a short period through several pulses of geochemically and isotopically different parental magmas. The oldest volcanic rocks exposed in the Cabo de Gata volcanic zone are the shoshonite and high-K calc-Alkaline rocks of Bujo group, which cry - stallised from a parental magma transitional from calc-Alkaline to alkaline potassic generated through large degrees of partial melting, and then affected by a minor contribution from metasomatised veins and a larger one from the surrounding mantle wedge, in comparison to ultrapotassic melts. Subsequent partial melting of the mantle source produced typical calc-Alkaline parental magmas belonging to the Rodalquilar and Agua Amarga groups. Sr-Nd-Pb isotope and incompatible trace element distributions of Cabo de Gata rocks are in agreement with a mantle-wedge source affected by a two-fold metasomatism. The data suggested that mild potassic to sub-Alkaline subduction-related parental magmas (i.e., high-K calc-Alkaline and calc-Alkaline) were generated in the Cabo de Gata sector within a mantle wedge metasomatised by a fluid-dominated agent. In contrast, the enrichment in K2O of shoshonitic to ultrapotassic magmas was achieved through recycling of subducted sediments through melts that enriched the mantle wedge in K and related elements. Such a scenario can be easily reconciled with a geodynamic setting at the edge of a destructive plate margin with the subducted slab responsible for the recycling of sediments within the mantle wedge.