Petrogenesis of Permian alkaline lamprophyres and diabases from the Spanish Central System and their geodynamic context within western Europe

Abstract

Basic to ultrabasic alkaline lamprophyres and
diabases intruded within the Spanish Central System (SCS)
during Upper Permian. Their high LREE, LILE and HFSE
contents, together with positive Nb–Ta anomalies, link
their origin with the infiltration of sublithospheric K-rich
fluids. These alkaline dykes may be classified in two distinct
groups according to the Sr–Nd isotope ratios: (1) a
depleted PREMA-like asthenospheric component, and (2) a
BSE-like lithospheric component. A slight enrichment in
radiogenic 207Pb and 208Pb allows the contribution of a
recycled crustal or lithospheric component in the mantle
sources. The intrusion of this alkaline magmatism is likely
to have occurred due to adiabatic decompression and
mantle upwelling in the context of the widespread rifting
developed from Carboniferous to Permian in western
Europe. The clear differences in the geochemical affinity of
Lower Permian basic magmas from north-western and
south-western Europe might be interpreted in terms of a
more extensive separation of both regions during that
period, until they were assembled during Upper Permian.