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)

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