Constraints on the emplacement of Martian nakhlite igneous rocks and their source volcano from advanced micro-petrofabric analysis

Griffin, S. et al. (2022) Constraints on the emplacement of Martian nakhlite igneous rocks and their source volcano from advanced micro-petrofabric analysis. Journal of Geophysical Research: Planets, (doi: 10.1029/2021JE007080) (In Press)

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Abstract

The Martian nakhlite meteorites, which represent multiple events that belong to a single magma source region represent a key opportunity to study the evolution of Martian petrogenesis. Here 16 of the 26 identified nakhlite specimens are studied using coupled electron backscatter diffraction (EBSD) and emplacement end-member calculations. EBSD was used to determine shape preferred orientation (SPO) of contained augite (high Ca-clinopyroxene) phenocrysts by considering their crystallographic preferred orientation (CPO). Parameters derived from EBSD, and energy dispersive X-ray spectroscopy (EDS) data were used in basic emplacement models to assess their dominant mechanism against three end-member scenarios: thermal diffusion, crystal settling, and crystal convection. Results from CPO analyses indicate low intensity weak-moderate CPO. In all samples, a consistent foliation within the <001> axes of augite are observed typically coupled with a weaker lineation CPO in one of the other crystallographic axes. These CPO results agree best with crystal settling being the dominant emplacement mechanism for the nakhlites. Modelled crystal settling results identify two distinguishable groups outside of the model’s resolution indicating the presence of secondary emplacement mechanisms. Comparison of the two identified groups against petrofabric, geochemical, and age parameters indicate random variability between individual meteorites. Therefore, coupled petrofabric and emplacement modelling results identify an overarching characteristic of a dominant crystal settling emplacement mechanism for the nakhlite source volcano despite exhibiting random variation with each discharge through time.

Item Type:Articles
Additional Information:This work was funded by the Science and Technology Facilities Council through grants ST/N000846/1 and ST/H002960/1 to M.R.L.
Status:In Press
Refereed:Yes
Glasgow Author(s) Enlighten ID:Keller, Dr Tobias and Lee, Professor Martin and Daly, Dr Luke and Griffin, Miss Sammy
Authors: Griffin, S., Daly, L., Keller, T., Piazolo, S., Forman, L. V., Lee, M. R., Baumgartner, R.J., Trimby, P.W., Benedix, G.K., Irving, A.J., and Hoefnagels, B.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of Geophysical Research: Planets
Publisher:Wiley
ISSN:2169-9097
ISSN (Online):2169-9100
Published Online:16 May 2022
Copyright Holders:Copyright © 2022 American Geophysical Union
First Published:First published in Journal of Geophysical Research: Planets 2022
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172314A journey from the solar nebula to planetary bodies: cycling of heat, water and organicsMartin LeeScience and Technology Facilities Council (STFC)ST/N000846/1GES - Earth Sciences
190265Follow the water: insights into the martian hydrosphere from nakhlitesMartin LeeScience and Technology Facilities Council (STFC)ST/H002960/1GES - Earth Sciences