Visean high-K mafic–intermediate plutonic rocks of the Ossa–Morena Zone (SW Iberia): implications for regional extensional tectonics

Abstract

Field relationships and new U-Pb geochronology data indicate a temporal link among the diverse high-K mafic-intermediate magmas of the Ossa-Morena Zone (OMZ). Ages of ca. 338-335 Ma for the Vale de Maceiras gabbro and the Campo Maior microdiorite and quartz-diorite indicate that plutonism took place during Variscan extensional D 2 deformation event in the OMZ. The syn-tectonic nature of the Vale de Maceiras pluton is attested by the orientation of intrusive contacts, magmatic foliation, and growth of contact metamorphic minerals in relation to Variscan extensional D 2 foliation. The Campo Maior microdiorite, quartz-diorite, and orthomigmatites are temporally linked to high-temperature mylonitic gneisses formed simultaneously with the Variscan extensional D 2 deformation event. The geochemical features of the Vale de Maceiras and Campo Maior mafic-intermediate rocks show an affinity with the sanukitoid series. This finding suggests that the observed geochemical variability, from tholeiitic to calc-alkaline and sanukitoid, in the Visean OMZ plutonic rocks (ca. 349-335 Ma) may have been inherited from partially melted mantle domains that were previously contaminated by crustal melts during subduction. Supplementary material at https://doi.org/10.6084/m9.figshare.c.6243822