Magnetic characterization of synthetic titanomagnetites: quantifying the recording fidelity of ideal synthetic analogs

Almeida, T. P. , Muxworthy, A. R., Williams, W., Kasama, T. and Dunin-Borkowski, R. (2014) Magnetic characterization of synthetic titanomagnetites: quantifying the recording fidelity of ideal synthetic analogs. Geochemistry, Geophysics, Geosystems, 15(1), pp. 161-175. (doi:10.1002/2013GC005047)

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Abstract

A series of four synthetic basalts comprising titanomagnetite (Fe3-xTixO4) grains of varied size and titanium content have been produced by a glass-ceramic method. Complementary characterization techniques of X-ray diffractometry, secondary electron microscopy, and transmission electron microscopy (TEM) demonstrate the reaction product composition consisted of mainly Fe3-xTixO4, pyroxene hedenbergite, fayalite, and SiO2. The samples exhibit bimodal distributions of larger (<2 µm) and smaller Fe3-xTixO4 particles (<50 nm in diameter), the latter found inside pyroxene crystals, as well as the sporadic occurance of dendritic Fe3-xTixO4 structures. Magnetic measurements show their bulk characteristics fall into two groups: Ti-rich titanomagnetite samples with varying Ti content; and near-stoichiometric magnetite. The TEM technique of off-axis electron holography allowed for visualization of the magnetic behavior of the synthetic Fe3-xTixO4 grains. Energy dispersive X-ray analysis and off-axis electron holography confirmed the small Fe3-xTixO4 grains (<50 nm) confined within glassy pyroxene regions to be Fe-rich and single domain, carrying strong magnetic signals, compared to the relatively magnetically weak larger Fe3-xTixO4 grains (x ∼ 0.6). The large grains in the pure magnetite sample are shown to be pseudo-single domain in nature. The quenching process involved in synthesis is considered similar to that of pillow basalts found at mid-ocean ridges and hence the reaction products are thought ideal in terms of characterization and understanding, for the purpose of studying natural systems.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Almeida, Dr Trevor
Authors: Almeida, T. P., Muxworthy, A. R., Williams, W., Kasama, T., and Dunin-Borkowski, R.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Geochemistry, Geophysics, Geosystems
Publisher:American Geophysical Union
ISSN:1525-2027
ISSN (Online):1525-2027
Copyright Holders:Copyright © 2013 The Authors
First Published:First published in Geochemistry Geophysics Geosystems 15(1):161-175
Publisher Policy:Reproduced under a Creative Commons License

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