Quaternary kimberlitic volcanism on the Tanzania Craton

The tuffs and lava of the Igwisi Hills are the youngest magmatic rocks on the Tanzania Craton. They consist of small xenoliths of phlogopite-calcite-garnet lherzolite in an olivine-calcite-dolomite-apatite-perovskite-spinel-serpentine matrix. Their mineralogy, major element chemistry and isotope chemistry indicate strong affinities with kimberlite, particularly the calcite-rich kimberlites of the Benfontein Sills, South Africa. As such, the Igwisi Hills are the youngest example of kimberlite magmatism. The magma formed by small degrees of melting of a carbonate-apatite-bearing peridotite source at depths in excess of 110 km.