Vertical gradations in mineralogy and oxide parageneses of the middle sill, together with the evidence of pre- and post-intrusion reactions, support the conclusion that the kimberlite sills at Benfontein, South Africa, were emplaced as xenolith-poor, phenocryst-rich carbonated peridotite magmas under T higher than those typical for kimberlite intrusions elsewhere. Release of the necessary heat for producing and maintaining reaction T probably involved consumption of graphite and/or diamond and/or methane. Redox re-equilibration of magmatic phases may have contributed significantly to the high intrusion T.-M.S.
