The chemistries of accessory mineral titanates in xenolith suites are discussed in the context that these titanates are major repositories for refractory silicate incompatible elements in the Earth's upper mantle. The minerals are considered to be metasomatic, having formed at an estimated 20-30 kbar and 900-1100oC; this places the zone of metasomatism at 75-100 km in the subcontinental lithosphere. It is possibly from within this zone that the high alkali and incompatible element signatures of kimberlites and lamproites are derived by mixing with melts generated in the asthenosphere. (Author's abstract)-J.M.H.
