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 olivine basalts from La Garrotxa (NE Spain region), suggest that the parental magma were originated from an homogeneous lherzolite source, strongly enriched in incompatible elemenb (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 01 + cpx + mg, in proportion that range between 75-40%, 55-10% and 15-0%, respectively