Depleted lherzolite xenoliths from the leucititic Morrón de Villamayor volcano (Calatrava volcanic field, Spain)

Abstract

This work reports petrographical, mineralogical and geochemical data of a suite of mantle xenoliths from the Morrón de Villamayor volcanic centre (MVM), which belongs to the Calatrava Volcanic Field (CVF), a part of the Circum-Mediterranean Anorogenic Cenozoic Igneous Province. The MVM volcano is the only centre belonging to the first stage of the CVF magmatism, an ultrapotassic stage that provides a sampling of the subcontinental lithospheric mantle beneath central Spain. The MVM peridotites record a variable host melt interaction (spongy texture and reaction zones), more intense toward xenolith-host leucitite contacts that it was formed during transport within the volcanic melt. The studied mantle xenoliths are spinel lherzolites equilibrated at lower temperatures (618–942 °C) and similar pressure ranges (8.8–13.6 kbar) than other studied CVF mantle xenoliths, and record a lithospheric mantle before the main volcanic Calatrava event. The MVM lherzolites could be classified in two groups by their chondrite-normalized rare earth element (REE) clinopyroxene patterns: group-1 lherzolites show flat pattern, and group-2 lherzolites display a LREE-depleted (N-MORB like) pattern. Group-1 lherzolites represent a more residual lithospheric mantle (up to 9 partial melting %) than group-2 lherzolites (~ 5%), the latter with similar partial melting degrees than other mantle xenoliths from the CVF. Moreover, group-1 lherzolites have undergone a post partial melting refertilization by different metasomatic agents: silicate and alkaline silicate melts different in composition to host leucitite. A primary clinopyroxene concentrate from these MVM lherzolites provides high Sr (87Sr/86Sr = 0.706104) and intermediate Nd (143Nd/144Nd = 0.512830) initial radiogenic ratios, not previously recorded in this volcanic field. This sampling proves the presence of an enriched isotope mantle pole in xenolith suites of the Calatrava area, trending in composition to an intermediate DMM-EMII component.