Title
Identification of magnetic Fe-Ti oxides in marine sediments by electron backscatter diffraction in scanning electron microscopy
Author
Franke, C.
Pennock, G.M.
Drury, M.R.
Engelmann, R.
Lattard, D.
Garming, J.F.L.
von Dobeneck, T.
Dekkers, M.J.
TNO Bouw en Ondergrond
Publication year
2007
Abstract
In paleomagnetic and environmental magnetic studies the magnetomineralogical identification is usually based on a set of rock magnetic parameters, complemented by crystallographic and chemical information retrieved from X-ray diffraction (XRD), (electron) microscopy or energy dispersive spectroscopy (EDS) of selected samples. While very useful, each of these supplementary techniques has its limitations when applied to natural sample material which are related to low particle concentrations (down to the ppm range in marine sediments) and very fine grain sizes (down to the nm scale). Therefore, meaningful application of such techniques depends on sample quality. Electron backscatter diffraction (EBSD) of individual grains in scanning electron microscopy (SEM) enables mineralogical identification of grains down to ∼0.2 micrometer and is particularly powerful when combined with EDS. In this study, we show the merits of EBSD for rock magnetic investigations by analyzing titanomagnetites and hemoilmenites of various compositions and submicron lamella of titanomagnetite-hemoilmenite intergrowths. Such particles often occur in natural marine sediments where EDS often has a semi-quantitative character and compositionally similar intergrowths may be difficult to distinguish. With the mineralogical information provided by EBSD unambiguous identification of spinel-type and trigonal oxides is obtained. Optimal EBSD patterns are gathered from smooth, polished surfaces, but here we show that interpretable EBSD patterns can be obtained directly from the surface of unconsolidated, so called 'non-embedded' particles from marine sediments. This information enhances the interpretative value of rock magnetic parameters. © 2007 The Authors Journal compilation © 2007 RAS.
Subject
Geosciences
Electron backscatter diffraction (EBSD)
Energy dispersive spectroscopy (EDS)
Hemoilmenite
Rock magnetism
Scanning electron microscopy (SEM)
Titanomagnetite
backscatter
ilmenite
iron oxide
magnetic mineral
magnetic property
marine sediment
scanning electron microscopy
titanomagnetite
X-ray diffraction
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TNO identifier
240105
ISSN
0956-540X
Source
Geophysical Journal International, 170 (2), 545-555
Document type
article