Determination of lattice parameter, oxidation state, and composition of individual titanomagnetite/titanomaghemite grains by transmission electron microscopy

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doi: 10.1029/1999JB900095
Author(s): Zhou, Weiming; Peacor, Donald R.; Van der Voo, Rob; Mansfield, John F.
Author Affiliation(s): Primary:
University of Michigan, Department of Geological Sciences, Ann Arbor, MI, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 104(B8), p.17,689-17,702. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. 55 refs.; illus., incl. 4 tables
Summary: A transmission electron microscopy (TEM) method, higher-order Laue zone (HOLZ) diffraction, has been applied to measurement of accurate lattice parameters of individual titanomagnetite and titanomaghemite grains. Lattice parameters and cation - composition data are obtained with TEM/analytical electron microscopy (AEM) for individual grains smaller than 0.1 µm in diameter. A suite of Ocean Drilling Program/Deep Sea Drilling Project ocean - floor basalts containing titanomagnetite-titanomaghemite with a wide range of oxidation degree (z), were employed to establish the relationship between lattice parameter (a), z and Ti - content (x) for naturally occurring samples. Standardization was accomplished with measurements on grains sufficiently large to allow the determination of absolute oxygen contents by electron microprobe analyses, which directly yielded z values. The probe data confirm that the maghemitization process in ocean - floor basalts is one involving loss of iron and indicate a nearly linear relationship between lattice parameters and oxidation degrees for a given x value, except for the smallest and largest values of z. The standardized relation permits determination of z for individual submicrometer-sized grains using only measured a - values and cation compositions as determined by HOLZ diffraction and AEM. Copyright 1999 by the American Geophysical Union.
Year of Publication: 1999
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 01 Mineralogy and Crystallography; Accuracy; Basalts; Cations; Chemical composition; Crystal structure; Deep Sea Drilling Project; Diffraction; Higher-order Laue zone; Igneous rocks; Lattice; Magnetic minerals; Measurement; Mid-ocean ridge basalts; Ocean Drilling Program; Oxidation; Oxides; Oxygen; TEM data; Titanomaghemite; Titanomagnetite; Volcanic rocks; World ocean
Record ID: 1999067554
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.

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