Mafic geosynclinal volcanism in the Lower Carboniferous of South Portugal

Abstract

Lower Carboniferous mafic volcanism in the Hercynian geosyncline of South Portugal produced spilite flows, often pillow lavas, and albite diabase intrusions. Spilites only occur in a central zone. Felsic voicanism took place at about the same time in this geosyncline: in South Portugal the mafic volcanism followed the felsic eruptions but in Southwest Spain the succession is reversed. The relationships between the mafic and the felsic activity indicate a rough juxtaposition in space and time but no genetical link. The mafic volcanics are considered to derive from the upper mantle and the felsic volcanics are thought to have been generated in Iocal magma chambers by melting in the deep crust.