Effects of Shock and Martian Alteration on Tissint Hydrogen Isotope Ratios and Water Content

1,2,5L.J. Hallis, 1,2G.R. Huss, 2K. Nagashima, 1,2G.J. Taylor, 3D. Stöffler, 4C.L. Smith, 5M.R. Lee
Geochimica et Cosmochimcia Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.12.035]
1NASA Astrobiology Institute, Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, Hawaii 96822-1839, United States
2Hawai’i Institute of Geophysics and Planetology, Pacific Ocean Science and Technology (POST) Building, University of Hawai’i, 1680 East-West Road, Honolulu, HI 96822, United States
3Museum of Natural History, Invalidenstrasse 43 Leibniz-Institut Für Evolutions-Und Biodiversitätsforschung, 10115 Berlin, Germany
4Department of Earth Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK
5School of Geographical and Earth Science, University of Glasgow, Gregory Building, Lillybank Gardens, Glasgow, G12 8QQ, Scotland, United Kingdom
Copyright Elsevier

The Tissint meteorite, a picritic shergottite, fell to Earth in Morocco on the 18th of July 2011, and is only the fifth Martian meteorite witnessed to fall. Hydrogen isotope ratios and water contents are variable within different minerals in Tissint. Ringwoodite and shock melt pockets contain elevated D/H ratios relative to terrestrial values (δD =761 to 4224 ‰). These high ratios in recrystallized phases indicate significant implantation of hydrogen from the D-rich Martian atmosphere during shock. In contrast, although olivine has detectable water abundances (230-485 ppm), it exhibits much lower D/H ratios (δD = +88 to -150 ‰), suggesting this water was not implanted from the Martian atmosphere. The minimal terrestrial weathering experienced by Tissint gives confidence that the olivine-hosted water has a Martian origin, but its high concentration indicates direct inheritance from the parental melt is improbable, especially given the low pressure of olivine crystallisation. Incorporation of a low δD crustal fluid, or deuteric alteration during crystallisation, could explain the relatively high water contents and low D/H ratios in Tissint olivine.


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