The transformation of γ Fe2O3 to α Fe2O3; thermal activation and the effect of elevated pressure

Author(s): Adnan, J.; O'Reilly, W.
Author Affiliation(s): Primary:
University of Newcastle upon Tyne, Department of Physics, Newcastle upon Tyne, United Kingdom
Volume Title: Physics of the Earth and Planetary Interiors
Source: Physics of the Earth and Planetary Interiors, 110(1-2), p.43-50. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-9201 CODEN: PEPIAM
Note: In English. 15 refs.; illus.
Summary: The transformation of acicular γ Fe2O3 particles to α Fe2O3 has been monitored using magnetic properties as a proxy for γ Fe2O3 concentration during the inversion process. The transformation is thermally activated, the height of the barrier opposing inversion being 3.7 eV at atmospheric pressure and 0.5 eV at a pressure of about 100 MPa. The barrier arises from the combination of a term representing the reduction in lattice energy in an inverted region, and the strain energy associated with the interface between the inverted and non-inverted phases. The sensitivity of the inversion process to pressure can be understood in terms of the dependence of these energy terms, and the energy barrier, on interatomic spacing. Extrapolation of these laboratory data to the conditions of the submarine crust at Site 504B of the Deep Sea Drilling Project is consistent with the inferred magnetic mineralogy of the recovered material. Abstract Copyright (1999) Elsevier, B.V.
Year of Publication: 1999
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 17 Geophysics, General; Activation energy; Crust; DSDP Site 504; Deep Sea Drilling Project; East Pacific; Experimental studies; Hematite; High pressure; IPOD; Iron oxides; Laboratory studies; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Maghemite; Magnetic properties; Ocean Drilling Program; Oxides; Pacific Ocean; Pressure; Spinel structure; Transformations; X-ray diffraction data
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Record ID: 1999012279
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands