Investigating the igneous petrogenesis of Martian volcanic rocks using augite quantitative textural analysis of the Yamato nakhlites

1Sammy Griffin,2Arya Udry,1,3,4Luke Daly,5,6Lucy Victoria Forman,1Martin R. Lee,7Benjamin E. Cohen
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13934]
1School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ UK
2Department of Geoscience, University of Nevada Las Vegas, Las Vegas, Nevada, 89154 USA
3Australian Centre for Microscopy and Microanalysis, The University of Sydney, New South Wales, 2006 Australia
4Department of Materials, University of Oxford, Oxford, OX1 3PH UK
5Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Western Australia, 6845 Perth, Australia
6Department of Earth and Planetary Sciences, Western Australia Museum, Western Australia, 6986 Perth, Australia
7School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FE UK
Published by arrangement with John Wiley & Sons

To better understand volcanism on planetary bodies other than the Earth, the quantification of physical processes is needed. Here, the petrogenesis of the achondrite Martian Yamato (Y) nakhlites (Y 000593, Y 000749, and Y 000802) is reinvestigated via quantitative analysis of augite (high-Ca clinopyroxene) phenocrysts: crystal size distribution (CSD), spatial distribution patterns (SDP), and electron backscatter diffraction (EBSD). Results from CSD and EBSD quantitative data sets show augite to have continuous uninterrupted growth resulting in calculated minimum magma chamber residence times of either 88–117 ± 6 yr or 9–12 yr. All samples exhibit low-intensity S-LS type crystallographic preferred orientation. Directional strain is observed across all samples with intracrystalline misorientation patterns indicative of (100)[001]:(001)[100] (Y 000593 and Y 000802) and {110}<001>or {110}1/2<110> (Y 000749) slip systems. SDP results indicate phenocryst-bearing crystal-clustered rock signatures. Combined findings from this work show that the Yamato nakhlites formed on Mars as individual low-viscosity lava flows or sills. This study shows that through combining these different quantitative techniques over multiple samples, one can more effectively compare and interpret resulting data to gain a more robust, geologically contextualized petrogenetic understanding of the rock suite being studied. The techniques used in this study should be equally applicable to igneous achondrites from other parent bodies.

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