Petrogénesis de los basaltos alcalinos de la Garrotxa, región volcánica del NE de España

Abstract

Compositional trends and trace elements abundance in leucite-basanites, nepheline-basanites and olivíne basalts from la Garrotxa (NE Spain region), suggest that the parental magma were originated from an homogeneous lherzolite source, strongly enriched in incompatible elements (between x15-x4 the chondritic values for the highly incompatible elements and between x5-x2 for the moderately incompatible), in which neither kaersutite, phlogopite or apatite remained as residual phases. The leucite-basanite magmas were derived by lower degrees of melting (7-10%) than the basanite s,s. and the olivine basalt magmas (13-15%). Except some primary leucite-basanites, the lavas from La Garrotxa underwent a moderate fractionation (~20%) of ol + cpx + mg, in proportion that range between 75-40%, 55-10% and 15-0 %, respectively.