Pressure dependence of Fe-Ti order in the ilmenite-hematite solid solution: Implications for the origin of lower crustal magnetization

Harrison, R. J. and Stone, H. J. and Redfern, S. A. T. (2006) Pressure dependence of Fe-Ti order in the ilmenite-hematite solid solution: Implications for the origin of lower crustal magnetization. Physics of the Earth and Planetary Interiors, 154 (3-4). pp. 266-275. DOI oi:10.1016/j.pepi.2005.04.016

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Abstract

The View the MathML source to View the MathML source cation-ordering phase transition in the ilmenite (FeTiO3)–hematite (Fe2O3) solid solution has been studied at high temperature and pressure using in-situ time-of-flight powder neutron diffraction. Experiments were performed on a synthetic sample of (FeTiO3)0.65(Fe2O3)0.35 at T ≤ 933 °C and P ≤ 1.1 GPa using an internally heated Paris–Edinburgh cell. The degree of cation order is observed to increase significantly with pressure. Thermodynamic analysis reveals an increase in the transition temperature from 911 °C at atmospheric pressure to 1010 °C at P = 0.64 GPa. This increase is much larger than that predicted on the basis of the volume change for the transition, indicating that the pressure dependence of cation ordering is dominated by enhanced cation–cation interaction, and not by volume strain. We predict an increase in the eutectoid temperature of up to 150 °C at 1 GPa. This implies that intergrowths of antiferromagnetic hematite and paramagnetic ilmenite could be stable at temperatures up to 540 °C at 1 GPa and cannot be ruled out as a potential source of lower crustal magnetization.

Item Type: Article
Additional Information: Sp. Iss. SI
Uncontrolled Keywords: 2006 AREP 2006 P IA50
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Physics of the Earth and Planetary Interiors
Volume: 154
Page Range: pp. 266-275
Identification Number: oi:10.1016/j.pepi.2005.04.016
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:02
Last Modified: 23 Jul 2013 10:07
URI: http://eprints.esc.cam.ac.uk/id/eprint/358

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