Identification of magnetic Fe-Ti oxides in marine sediments by electron backscatter diffraction in scanning electron microscopy

Franke, Christine; Pennock, Gill; Drury, M. R.; Engelmann, R.; Lattard, Dominique; Garming, J. F. L.; Dobeneck, Tilo von; Dekkers, Mark J.

doi:10.1111/j.1365-246x.2007.03410.x

Cited by 19 publications

(16 citation statements)

References 63 publications

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“…Iron-(Ti)-oxides are also refractory minerals in which genetic and deformational history can be preserved. Several EBSD studies have been undertaken in rocks ranging from gabbros [65] and deformed granites [66] to marine sediments [67]. Barbosa and Lagoeiro, 2010 [68] used EBSD to address transformation between magnetite and hematite in samples from the Quadrilátero Ferrífero of Brazil, while Rosière et al (2013) [69] assessed the interplay between deformation and mineralization in high-grade iron ores hosted by shear zones.…”

Section: Electron Back-scatter Diffraction (Ebsd)mentioning

confidence: 99%

Advances and Opportunities in Ore Mineralogy

et al. 2017

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Abstract:The study of ore minerals is rapidly transforming due to an explosion of new microand nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can be obtained from ten of today's most important, or emerging, techniques and methodologies are reviewed: laser-ablation inductively-coupled plasma mass spectrometry; focussed ion beam-scanning electron microscopy; high-angle annular dark field scanning transmission electron microscopy; electron back-scatter diffraction; synchrotron X-ray fluorescence mapping; automated mineral analysis (Quantitative Evaluation of Mineralogy via Scanning Electron Microscopy and Mineral Liberation Analysis); nanoscale secondary ion mass spectrometry; atom probe tomography; radioisotope geochronology using ore minerals; and, non-traditional stable isotopes. Many of these technical advances cut across conceptual boundaries between mineralogy and geochemistry and require an in-depth knowledge of the material that is being analysed. These technological advances are accompanied by changing approaches to ore mineralogy: the increased focus on trace element distributions; the challenges offered by nanoscale characterisation; and the recognition of the critical petrogenetic information in gangue minerals, and, thus the need to for a holistic approach to the characterization of mineral assemblages. Using original examples, with an emphasis on iron oxide-copper-gold deposits, we show how increased analytical capabilities, particularly imaging and chemical mapping at the nanoscale, offer the potential to resolve outstanding questions in ore mineralogy. Broad regional or deposit-scale genetic models can be validated or refuted by careful analysis at the smallest scales of observation. As the volume of information at different scales of observation expands, the level of complexity that is revealed will increase, in turn generating additional research questions. Topics that are likely to be a focus of breakthrough research over the coming decades include, understanding atomic-scale distributions of metals and the role of nanoparticles, as well how minerals adapt, at the lattice-scale, to changing physicochemical conditions. Most importantly, the complementary use of advanced microbeam techniques allows for information of different types and levels of quantification on the same materials to be correlated.

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Section: Electron Back-scatter Diffraction (Ebsd)mentioning

confidence: 99%

Advances and Opportunities in Ore Mineralogy

et al. 2017

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“…These grains were distinguished by their morphology and cation element contents. Crystallographic mineral identification by electron backscatter diffraction (EBSD [e.g., Prior et al, 1999]) was carried out as a spot check on some representative particles [Franke et al, 2007a].…”

Section: Electron Microscopymentioning

confidence: 99%

“…The semiquantitative element analyses (Table 2b and Figure 3) indicate hemoilmenite compositions between Hilm45 to near end-member ilmenite (Hilm96) in paragenesis with Tmt phases of complementary compositions. Ti-rich Tmt and Hilm crystals were distinguished by a combination of the EDS and EBSD techniques [Franke et al, 2007a]. This approach discriminates Tmt and Hilm unambiguously by their elemental composition and crystallographic space group.…”

Section: Titanomagnetite-hemoilmenite Intergrowthsmentioning

confidence: 99%

“…A relatively mild oxic to suboxic environment ( Figure 1) promotes good preservation of the primary magnetic mineral assemblage. This study employs SEM and TEM methods, including energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD [Franke et al, 2007a]), on magnetic and heavy liquid separates [Franke et al, 2007b] to classify magnetic carriers according to their mineralogy, morphology, and granulometry. On the basis of their particle characteristics and geographical distributions, we develop genesis, source, transport and diagenesis issues.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic petrology of equatorial Atlantic sediments: Electron microscopy results and their implications for environmental magnetic interpretation

et al. 2007

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[1] The magnetic microparticle and nanoparticle inventories of marine sediments from equatorial Atlantic sites were investigated by scanning and transmission electron microscopy to classify all present detrital and authigenic magnetic mineral species and to investigate their regional distribution, origin, transport, and preservation. This information is used to establish source-to-sink relations and to constrain environmental magnetic proxy interpretations for this area. . Sediments from two depths corresponding to marine isotope stages 4 and 5.5 were processed. This selection represents glacial and interglacial conditions of sedimentation for the western, central, and eastern equatorial Atlantic and avoids interferences from subsurface and anoxic processes. Crystallographic, elemental, morphological, and granulometric data of more than 2000 magnetic particles were collected by scanning and transmission electron microscopy. On basis of these properties, nine particle classes could be defined: detrital magnetite, titanomagnetite (fragmental and euhedral), titanomagnetite-hemoilmentite intergrowths, silicates with magnetic inclusions, microcrystalline hematite, magnetite spherules, bacterial magnetite, goethite needles, and nanoparticle clusters. Each class can be associated with fluvial, eolian, subaeric, and submarine volcanic, biogenic, or chemogenic sources. Large-scale sedimentation patterns are delineated as well: detrital magnetite is typical of Amazon discharge, fragmental titanomagnetite is a submarine weathering product of mid-ocean ridge basalts, and titanomagnetite-hemoilmenite intergrowths are common magnetic particles in West African dust. This clear regionalization underlines that magnetic petrology is an excellent indicator of source-to-sink relations. Hematite encrustations, magnetic spherules, and nanoparticle clusters were found at all investigated sites, while bacterial magnetite and authigenic hematite were only detected at the more oxic western site. At the eastern site, surface pits and crevices were seen on the crystal faces indicating subtle early diagenetic reductive dissolution. It was observed that paleoclimatic signatures of magnetogranulometric parameters such as the ratio of anhysteretic and isothermal remanent magnetizations can be formed either by mixing of multiple sources with separate, relatively narrow grain size ranges (western site) or by variable sorting of a single source with a broad grain size distribution (eastern site). Hematite, goethite, and possibly ferrihydrite nanoparticles occur in all sediment cores studied and have either high-coercive or superparamagnetic properties depending on their partly ultrafine grain sizes. These two magnetic fractions are generally discussed as separate fractions, but we suggest that they could actually be genetically linked.

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“…The new peaks represent an intermixture of Fe 2 O 3 and TiO 2 oxides forming the new phase Ti x Fe y O z . Through the consultation of Ti-Fe-O ternary phase diagrams and related literature [15][16][17], two phases, namely the spinel (TiFe 2 O 4 ) and Pseudobrookite (TiFe 2 O 5 ) phases might be nominated amongst those most thermodynamically likely to form (i.e. stable).…”

Section: Structure Evolutionmentioning

confidence: 99%