Cr-rich spinel and garnet in two peridotite xenoliths from the Frank Smith mine, South Africa: significance of Al and Cr distribution between spinel and garnet.

Of two peridotite xenoliths one contains very Ti-rich minerals and the other Ti-poor minerals. Various geothermometers indicate approx 1350 K and approx 1100 K, respectively, with the low Al₂O₃ in the orthopyroxenes of the Ti-poor peridotite giving 39-47 kbar from the Wood-Banno geobarometer. Complex behaviour was found for the Cr/Al distribution in published analyses of garnet and spinel; these phases may coexist over a 30 kbar P interval ranging from approx 16 kbar for low-bulk Cr to approx 40 kbar for high Cr.-R.A.H.