Cryptic metasomatism in the upper mantle beneath Kutch: Evidence from spinel lherzolite xenoliths

摘要: Spinel lherzolite xenoliths entrained in the alkaline rocks from central Kutch vary fertile (10-12% modal clinopyroxene) to depleted (2-3% types. Low equilibrium temperatures (884-972°C) indicateentrainment of shallow depths within lithosphere. Variations major oxides and incompatible elemental concentrations clinopyroxene indicate a primary control by partial melting. In most however, light rare earth elements (LREE), thorium (Th) niobium (Nb) are strongly enriched cannot be attributed totally process The absence typical 'meta-somatic' minerals, low equilibration LREE patterns that upper mantle below underwent an event cryptic metasomatic enrichment prior distinctive chemical features, viz. enrichment, strong Ti depletion relative Eu, slight Nb fractionation Zr Hf therefore high Zr/Hf ratio, La/Yb, Nb/La Ti/Eu all results interaction refractory peridotite residues with carbonatite melts.