La región volcánica mio-pleistocena del NE de España

Abstract

ABSTRACT The mio-pleistocene volcanic rocks in the NE Spain region can be grouped into leucitebasanites, basanites s.s., olivine basalts, and trachytes, The mineralogical and ,geochemical features displayed by these rocks, together with the common ocurrence of mantle-derived inclusions, indicate their alkaline nature, as well as that many of the magmas represent primary liquids. Compositional trends and 'trace element abundances suggest that the parental magmas were originated from a homogeneous Iherzolite source, strongly enriched in incompatible elements (> 10 x the chondritic values for the highly incompatible elements and between 3-1.5 x for the moderately incompatible), in which neither kaersutite, phlogopite or apatite remained as residual phases. On the other hand, the differentiated lavas were derived from magmas produced by 10-15% partial melting of such mant1e source, that later underwent fractionation (F= 80%) of olivine + clinopyroxene + titanomagnetite, in proportion that range between 75-40%, 55-10% and 15-0%, respectively. The nature of this volcanism gives further support to independent geological and geophysical evidence indicating that the northeastern corner of the Spain -like most of the iberian mediterranean margin- has been subjected to rifting since late Oligocene-early Miocene.