Journal article

Automated mapping of K-feldspar by electron backscatter diffraction and application to 40Ar/39Ar dating

Sandra McLaren, Steven M Reddy



The ability to quantify feldspar microstructure using the electron backscatter diffraction (EBSD) method has direct application in the study of rock deformation and strain kinematics. However, automated EBSD analysis of low symmetry phases, such as feldspar, has previously proven difficult. Here, we successfully apply the EBSD method to a number of granitic feldspars and develop automated phase and orientation mapping to discriminate K-feldspar and plagioclase, and quantify orientation variations within individual K-feldspar grains. These results represent the first automated quantitative mapping of orientation microstructure in K-feldspar. We use the method to evaluate the relationship betw..

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Awarded by Australian Research Council

Funding Acknowledgements

Geoff Fraser, John Fitz Gerald, Jim Dunlap and Mark Harrison are thanked for helpful discussions throughout the project. Geoff Fraser is also thanked for providing the Dead Fox Granite sample. Oscar Lovera provided initial assistance with the MDD modeling. We are grateful to Ian Parsons for his detailed comments on an earlier version of this manuscript. We are also grateful to Jo Wartho for assistance and guidance with UV <SUP>40</SUP>Ar/<SUP>39</SUP>Ar analysis. Nick Timms and Rob Hough are thanked for help with sample preparation and Elaine Miller is thanked for assistance with SEM operation. Irradiation of the Dead Fox Granite K-feldspar grain separate was undertaken by the Australian Nuclear Science and Technology Organization, through the Australian Institute of Nuclear Science and Engineering and was analysed at the Research School of Earth Sciences. The ultra-violet laser ablation microprobe <SUP>40</SUP>Ar/<SUP>39</SUP>Ar analyses were undertaken at the Western Australian Argon Isotope Facility, operated by a consortium consisting of Curtin University and the University of Western Australia. We are grateful to Mark Pearce and an anonymous reviewer for their comments on the manuscript, and Tom Blenkinsop for his editorial efforts. SM acknowledges support of Australian Research Council Australian Postdoctoral Fellowship and Discovery Grant DP0208837 and the University of Melbourne Faculty of Science Centenary Research Fellowship for support during publication. SMR acknowledges a Curtin University Targeted Research Fellowship and ARC Discovery Project DP0664078. This paper is TIGeR contribution 116.