Melt inclusions from the deep Slave lithosphere: Implications for the origin and evolution of mantle-derived carbonatite and kimberlite

Abstract

Melt inclusions in clinopyroxenes from lherzolitic xenoliths from the deep lithospheric mantle beneath the Slave Craton (Lac de Gras area, Canada) reveal multiple origins for carbonatitic melts. One type of inclusions consists of a series of silicate-carbonate-silicate concentric layers, interpreted to have unmixed under disequilibrium conditions during rapid ascent to the surface. Bulk major- and trace-element compositions are typical of Group 1 kimberlites and quantitative nuclear microprobe imaging of the globules reveals fractionation of related elements (e.g. F-Br, Nb-Ta) between the silicate and carbonate components. The globules probably formed by partial melting of carbonated peridot..