Exsolved silicate and oxide phases from clinopyroxenes in a single Hawaiian xenolith: Implications for oxidation state of the Hawaiian upper mantle

A single garnet-bearing clinopyroxenite xenolith from the Salt Lake crater on Oahu, Hawaii, contains two distinct types of clinopyroxene; one contains exsolved garnet, ilmenite, and magnetite, and the other contains exsolved hercynite-pleonaste spinel, orthopyroxene, and ilmenite. Application of mineral geothermometers, barometers, and oxygen barometers to this unusual combination of exsolved phases defines the following conditions of last mantle equilibration of this xenolith: P = 19 kbar, T =1153 °C, and log 10 f O 2 = -9.7.