Evidence for silicate dissolution on Mars from the Nakhla meteorite

Lee, M.R. , Tomkinson, T., Mark, D.F. , Stuart, F.M. and Smith, C.L. (2013) Evidence for silicate dissolution on Mars from the Nakhla meteorite. Meteoritics and Planetary Science, 48(2), pp. 224-240. (doi: 10.1111/maps.12053)

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Veins containing carbonates, hydrous silicates and sulphates that occur within and between grains of augite and olivine in the Nakhla meteorite are good evidence for the former presence of liquid water in the Martian crust. Aqueous solutions gained access to grain interiors via narrow fractures, and those fractures within olivine whose walls were oriented close to (001) were preferentially widened by etching along [001]. This orientation selective dissolution may have been due to the presence within olivine of shock-formed [001](100) and [001]{110} screw dislocations. The duration of etching is likely to have been brief, possibly less than a year, and the solutions responsible were sufficiently cool and reducing that laihunite is absent and Fe liberated from the olivine was not immediately oxidised. The pores within olivine were mineralised in sequence by siderite, nanocrystalline smectite, a Fe-Mg phyllosilicate, and then gypsum, whereas only the smectite occurs within augite. The nanocrystalline smectite was deposited as sub-micrometre thick layers on etched vein walls, and solution compositions varied substantially between and sometimes during precipitation of each layer. Together with microcrystalline gypsum the Fe-Mg phyllosilicate crystallised as water briefly returned to some of the veins following desiccation fracturing of the smectite. These results show that etching of olivine enhanced the porosity and permeability of the nakhlite parent rock and that dissolution and secondary mineralization took place within the same near-static aqueous system.

Item Type:Articles
Additional Information:The definitive version is available at www3.interscience.wiley.com
Keywords:Mars, meteorite, water
Glasgow Author(s) Enlighten ID:Mark, Professor Darren and Tomkinson, Dr Tim and Lee, Professor Martin and Stuart, Professor Fin and Smith, Dr Caroline
Authors: Lee, M.R., Tomkinson, T., Mark, D.F., Stuart, F.M., and Smith, C.L.
Subjects:Q Science > QB Astronomy
Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > Scottish Universities Environmental Research Centre
Research Group:Earth Systems
Journal Name:Meteoritics and Planetary Science
Publisher:Wiley-Blackwell Publishing Ltd.
Published Online:28 January 2013
Copyright Holders:Copyright © 2012 The Meteoritical Society
First Published:First published in Meteoritics and Planetary Science 48(2):224-240
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
519741Follow the water: insights into the martian hydrosphere from nakhlitesMartin LeeScience & Technologies Facilities Council (STFC)ST/H002960/1SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES