Low-temperature oxidation of a titanomagnetite and the implications for paleomagnetism

Abstract

Natural crystals of a titanomagnetite were oxidized in an excited oxygen gas at temperatures that were varied from 50° to 200°C, and the effect of oxidation on the intensity of the remanent magnetization was measured. Oxidation of the titanomagnetite, which was extracted by dry grinding from a submarine basalt, produced two separate types of behavior. When the temperature of oxidation was 135°C or above, oxidation produced an increase in the intensity of the original remanence and a chemical remanence that was stronger than the original remanence in the sample. When the temperature of oxidation was below 135°C, oxidation produced a decrease in the intensity of the initial remanence and a chemical component that was less intense than the original remanence. Both types of oxidation produced a chemical magnetization having higher coercivity than the original remanence during af demagnetization. The increase in remanent intensity at the higher oxidation temperatures is shown to be associated with the unmixing of the titanomaghemite that forms during oxidation.