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.

¹Kevin Righter,²Ryan S. Jakubek,¹Marc D. Fries,³John Schutt,²Kellye Pando,²Roger Harrington
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13932]
¹Mailcode XI2, NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas, 77058 USA
²Jacobs, NASA Johnson Space Center, Houston, Texas, 77058 USA
³Department of Earth, Environmental, and Planetary Science, Case Western Reserve University, 10900 Euclid Ave, Cleveland, Ohio, 44106 USA
Published by arrangement with John Wiley & Sons

Carbonaceous chondrites of the Vigarano group (CV) are primitive (nearly un-metamorphosed) meteorites that provide a wealth of information about the early solar system, including constraints on chondrule formation, origin of calcium-aluminum inclusions, stability of organic compounds, and redox conditions. The US Antarctic meteorite collection contains 119 CV samples from 15 dense collection areas (DCAs) from the TransAntarctic Mountains; these samples have been assigned a preliminary classification as CVs, but not to the subgroups oxidized A, oxidized B, and reduced. Furthermore, variation in petrologic grade can be determined non-destructively using Raman spectroscopy. To update the classification of both subgroups and petrologic types in the collection, we have acquired magnetic susceptibility, metal and sulfide compositions, and Raman spectra. Overall, there are 55 oxidized A samples, 18 oxidized B samples, and 46 reduced samples. Several of the CVs are quite primitive (Lewis Cliffs Ice Tongue and MacAlpine Hills) but are also very small. Multiple pairing groups have been identified in the Miller Range (MIL), Queen Alexandra Range, and Larkman Nunatak DCAs, including all of the subgroups. In MIL 090981, there is evidence for multiple lithologies. We make suggested updates for all the samples, knowing that this information will help to better guide researchers interested in studying the CV chondrites in the US Antarctic meteorite collection.