Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001

1Carles E. Moyano-Cambero, 1Josep M. Trigo-Rodríguez, 2M. Isabel Benito, 3Jacinto Alonso-Azcárate, 4Martin R. Lee, 5Narcís Mestres, 6,7Marina Martínez-Jiménez, 1Francisco J. Martín-Torres, 8Jordi FraxedasMeteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12851]
1Institute of Space Sciences (IEEC-CSIC), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
2Departamento de Estratigrafía-IGEO, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid-CSIC, Madrid, Spain
3Fac. de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, Toledo, Spain
4School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 800, UK
5Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, Barcelona, Spain
6Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain
7Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Kiruna, Sweden
8Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and the Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, Barcelona, Spain
Published by arrangement with John Wiley & Sons

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe-Mg-Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg- and Fe-rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion.

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