Summary: Electron-probe data are presented for coexisting magnetite and ilmenite from seven gabbro cumulates and a gabbro pegmatite, and bulk FeO-Fe₂O₃-TiO₂ analyses for ten magnetite-ilmenite assemblages. The oxides equilibrated at 580 to 720 °C and oxygen fugacities of 10^−15·0 to 10^−20·5 bar. Late-stage alteration, associated with growth of hydrothermal silicates, resulted in the breakdown of ilmenite to rutile and the dissolution of magnetite. Higher levels in the intrusion equilibrated at lower temperatures than deeper levels. All features described are consistent with the retention of the initial water content of the magma within the walls of the intrusion.