Geomaterials in the age of megapixel imaging
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Date
2016-02-04
Journal Title
Journal ISSN
Volume Title
Publisher
Australian Microscopy and Microanalysis Society
Abstract
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.
Description
Keywords
Geologic deposits, Ores, Environment, Synchrotrons, X-ray fluorescence analysis, Petrology, Biological evolution, Valence, Coal
Citation
Brugger, J., Etschmann, B., Li, K., Michaut, P., Donner, E., & Howard, D. (2016). Geomaterials in the age of megapixel imaging. Paper presented to ACMM24 : Australian Conference on Microscopy and Analysis : Melbourne Convention and Exhibition Centre, 31 Jan-4 Feb 2016, (pp. 66-67).