Oxygen Fugacity in the Apatite-Bearing Intrusion of the Khibina Complex

Based on the analysis of coexisting minerals (magnetite, ilmenite, titanite, and pyroxene), the temperature and redox conditions of rock crystallization in the Khibina alkaline massif were estimated. Under the redox conditions typical of the Khibina complex, the carbon speciation evolved as follows: CO2 in fluid and carbonate anions in melt at high temperatures; then, graphite formation; and, at lower temperatures, the appearance of significant amounts of hydrocarbons owing to fluid-graphite interaction. Abiogenic hydrocarbons in magmatic complexes can be produced by processes differing from the Fischer-Tropsch synthesis.