Transmission electron microscope analyses of alteration phases in MIL090030

Hallis, L.J. , Ishii, H.A., Bradley, J.P. and Taylor, G.J. (2014) Transmission electron microscope analyses of alteration phases in MIL090030. Geochimica et Cosmochimica Acta, 134, pp. 275-288. (doi: 10.1016/j.gca.2014.02.007)

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The nakhlite group of martian meteorites found in the Antarctic contain varying abundances of both martian and terrestrial secondary alteration phases. The aim of this study was to use transmission electron microscopy (TEM) to compare martian and terrestrial alteration embodied within a single nakhlite martian meteorite find – MIL 090032. Martian alteration veins in MIL 090032 are composed of poorly ordered Fe-smectite phyllosilicate. This poorly-ordered smectite appears to be equivalent to the nanocrystalline phyllosilicate/hydrated amorphous gel phase previously described in the martian alteration veins of other nakhlites. Chemical differences in this nanocrystalline phyllosilicate between different nakhlites imply localised alteration, which occurred close to the martian surface in MIL 090032. Both structurally and compositionally the nakhlite nanocrystalline phyllosilicate shows similarities to the amorphous/poorly ordered phase recently discovered in martian soil by the Mars Curiosity Rover at Rocknest, Gale Crater. Terrestrially derived alteration phases in MIL 090032 include jarosite and gypsum, amorphous silicates, and Fe-oxides and hydroxides. Similarities between the mineralogy and chemistry of the MIL 090032 terrestrial and martian alteration phases suggest the alteration conditions on Mars were similar to those in the Antarctic. At both sites a small amount of fluid at low temperatures infiltrated the rock and became acidic as a result of the conversion of Fe2+ to Fe3+ under oxidising conditions.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Hallis, Dr Lydia
Authors: Hallis, L.J., Ishii, H.A., Bradley, J.P., and Taylor, G.J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Research Group:Planetary Science and Astrobiology
Journal Name:Geochimica et Cosmochimica Acta
Published Online:01 March 2014

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