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Geologic history of Martian regolith breccia Northwest Africa 7034: Evidence for hydrothermal activity and lithologic diversity in the Martian crust

McCubbin, Francis M.; Boyce, Jeremy W.; Novák‐Szabó, Timea; Santos, Alison R.; Tartèse, Romain; Muttik, Nele; Domokos, Gabor; Vazquez, Jorge; Keller, Lindsay P.; Moser, Desmond E.; Jerolmack, Douglas J.; Shearer, Charles K.; Steele, Andrew; Elardo, Stephen M.; Rahman, Zia; Anand, Mahesh; Delhaye, Thomas and Agee, Carl B. (2016). Geologic history of Martian regolith breccia Northwest Africa 7034: Evidence for hydrothermal activity and lithologic diversity in the Martian crust. Journal of Geophysical Research: Planets, 121(10) pp. 2120–2149.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1002/2016JE005143
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Abstract

The timing and mode of deposition for Martian regolith breccia Northwest Africa (NWA) 7034 were determined by combining petrography, shape analysis, and thermochronology. NWA 7034 is composed of igneous, impact, and brecciated clasts within a thermally annealed submicron matrix of pulverized crustal rocks and devitrified impact/volcanic glass. The brecciated clasts are likely lithified portions of Martian regolith with some evidence of past hydrothermal activity. Represented lithologies are primarily ancient crustal materials with crystallization ages as old as 4.4 Ga. One ancient zircon was hosted by an alkali-rich basalt clast, confirming that alkalic volcanism occurred on Mars very early. NWA 7034 is composed of fragmented particles that do not exhibit evidence of having undergone bed load transport by wind or water. The clast size distribution is similar to terrestrial pyroclastic deposits. We infer that the clasts were deposited by atmospheric rainout subsequent to a pyroclastic eruption(s) and/or impact event(s), although the ancient ages of igneous components favor mobilization by impact(s). Despite ancient components, the breccia has undergone a single pervasive thermal event at 500–800°C, evident by groundmass texture and concordance of ~1.5 Ga dates for bulk rock K-Ar, U-Pb in apatite, and U-Pb in metamict zircons. The 1.5 Ga age is likely a thermal event that coincides with rainout/breccia lithification. We infer that the episodic process of regolith lithification dominated sedimentary processes during the Amazonian Epoch. The absence of pre-Amazonian high-temperature metamorphic events recorded in ancient zircons indicates source domains of static southern highland crust punctuated by episodic impact modification.

Item Type: Journal Item
Copyright Holders: 2016 American Geophysical Union
ISSN: 1934-8843
Project Funding Details:
Funded Project NameProject IDFunding Body
Astronomy and Planetary Sciences at the Open UniversityST/L000776/1STFC (Science & Technology Facilities Council)
Not SetST/1001298/1STFC (Science & Technology Facilities Council)
Keywords: Martian Meteorite; NWA 7034; Breccia
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Space
Item ID: 50322
Depositing User: Mahesh Anand
Date Deposited: 26 Jul 2017 10:52
Last Modified: 08 May 2019 22:40
URI: http://oro.open.ac.uk/id/eprint/50322
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