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An Evaluation of Dating of Diagenetic Xenotime by Electron Microprobe.

Published online by Cambridge University Press:  02 July 2020

Brendan J. Griffin ,
Duncan Forbes  and
Neal J. McNaughton
Brendan J. Griffin
Affiliation:
Western Australian Centre for Microscopy, The University of Western Australia, Nedlands, WA6907
Duncan Forbes
Affiliation:
Department of Geology and Geophysics, The University of Western Australia, Nedlands, WA6907
Neal J. McNaughton
Affiliation:
Department of Geology and Geophysics, The University of Western Australia, Nedlands, WA6907
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Extract

Xenotime is an igneous mineral commonly present in pegmatite and fractionated granite. Recent studies reveal that it also forms as a diagenetic mineral. Minute (0.1-5 μm) xenotime overgrowths typically crystallise on the surfaces of detrital zircon shortly after sedimentation, in a wide range of siliciclastic sedimentary units. For example, in backscattered electron (BSE) imaging using a scanning electron microscope (SEM), two minute, euhedral, pyramidal, xenotime overgrowths on an oscillatory-zoned detrital Ambergate zircon are evident (figure 1).

Electron microprobe analysis (EMPA) geochronology is a chemical dating method that uses precisely measured concentrations of U, Th, and Pb, and the decay rates of U238, U235, and Th232, to calculate an age for a mineral. The EMPA dating method used in this study to date igneous xenotime and igneous-metamorphic monazite is the chemical isochron method (CHIME). EMPA geochronology is not a widely used technique because of the higher precision of isotopic geochronology.

Type
Ceramics & Minerals
Information
Microscopy and Microanalysis , Volume 6 , Issue S2: Proceedings: Microscopy & Microanalysis 2000, Microscopy Society of America 58th Annual Meeting, Microbeam Analysis Society 34th Annual Meeting, Microscopical Society of Canada/Societe de Microscopie de Canada 27th Annual Meeting, Philadelphia, Pennsylvania August 13-17, 2000 , August 2000 , pp. 408 - 409
Copyright
Copyright © Microscopy Society of America

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References

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3. This project was funded by the Australian Research Council and the University of Western Australia.Google Scholar