Browsing by Author "Michaut, P"

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    Geomaterials in the age of megapixel imaging
    (Australian Microscopy and Microanalysis Society, 2016-02-04) Brugger, J; Etschmann, BE; Li, K; Michaut, P; Donner, E; Howard, DL
    Geological samples are extremely diverse and share a tendency for heterogeneity and complexity. This is especially true for ores and for environmental samples, which result from complex processes in dynamic environments. In recent years, a number of tools that enable imaging element distribution in geological samples at 1-50μm-resolution and over cm2 areas have seen rapid development and have become readily available. The application of synchrotron-based X-ray fluorescence mapping has been limited to addressing key questions because of low availability and high cost. However, recent advances in X-ray fluorescence detector technology are bringing new possibilities to petrology. Millisecond dwell times allow collection of thin-section-size maps in hours, and improvement in data analysis produces quantitative elemental maps. The technique can be combined with XANES imaging to provide additional information about element speciation (e.g., As oxidation state). We illustrate applications of M(egapixel)-μXRF for ore petrology (commodities: Au, Pt, U, Cu, Ge, Ti, REE, Nb), coal petrology, and environmental samples. Examples of outcomes include: (i) the distribution of μm-sized Pt-rich grains and Ti-mobility during schistosity formation at the Fifield Pt prospect (Australia); (ii) confirmation of the two-stage Ge-enrichment in the Barrigão deposit (Portugal), with demonstration of the presence of Ge in solid solution in the early chalcopyrite; (iii) enrichment of U during late dissolution-reprecipitation reactions in the Cu-rich ores of the Moonta and Wallaroo IOCG deposits (Australia); (iv) history of REE-Ti-Nb-(As) mobility during amphibolite to greenschist facies metamorphism in the Binntal Valley, Switzerland; (v) contrasting distribution of As, Ge and W in Ge-rich coals across the Globe; and (vi) evolution of the distribution and speciation of Cu upon aging of biosolids.