Depletion Events, Nature of Metasomatizing Agent and Timing of Enrichment Processes in Lithospheric Mantle Xenoliths from the Veneto Volcanic Province

Abstract

analogues of the modelled metasomatizing agent/s occur in the Mantle xenoliths included in the alkaline basic lavas from the South Alpine domain as late Cretaceous lamprophyric dykes, as Paleogene Veneto Volcanic Province (VVP) consist of predominant well as VVP alkaline basic lavas. An estimate of timing of the spinel lherzolites (21–6% clinopyroxene) and minor spinel harzenrichment processes was achieved by a REE inward diffusion burgites (4–2% clinopyroxene), mainly protogranular textured. Most model in primary and spongy clinopyroxenes, assuming LREEof the xenoliths show superimposed textural evidence of metasomatic enriched secondary clinopyroxenes as the boundary surface comprocesses, consisting of reaction patches and spongy clinopyroxenes, position. Model calculations imply a complete chemical revariably associated with glass and secondary olivine, clinopyroxene, homogenization of a 1 mm crystal in a time span of 4·8–16 kyr. spinel and feldspar. Whole-rock and mineral major and trace element Consequently, the observed REE zoning of clinopyroxenes, together data indicate a complex history of depletion and enrichment processes with the presence of glassy patches, indicates that the most recent undergone by the continental lithospheric mantle beneath a withinmetasomatic processes occurred shortly before the entrainment of plate region. Protogranular-textured clinopyroxenes from lherzolites mantle xenoliths by the host lavas. show heavy rare earth element (HREE) contents >10 times chondrite and strong light REE (LREE) depletion [(La/Yb)N = 0·002–0·025)], whereas those in harzburgites vary from slightly LREE depleted to LREE enriched [(La/Yb)N = 0·64–4·00],