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Mineralogy and chemistry of altered Icelandic basalts: Application to clay mineral detection and understanding aqueous environments on Mars

Ehlmann, B. L. and Bish, D. L. and Ruff, S. W. and Mustard, J. F. (2012) Mineralogy and chemistry of altered Icelandic basalts: Application to clay mineral detection and understanding aqueous environments on Mars. Journal of Geophysical Research E, 117 (E11). Art. No. E00J16. ISSN 0148-0227. https://resolver.caltech.edu/CaltechAUTHORS:20140224-092155309

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Abstract

We used a suite of techniques, including those emulating compositional data sets obtained from Mars orbit and obtainable at the Mars surface, to examine aqueous alteration of basaltic rocks from Iceland as a mineralogic and geochemical analog for Noachian environments on Mars. A sample suite was collected for laboratory measurement of (1) whole-rock visible/near-infrared (VNIR) reflectance and thermal infrared (TIR) emission spectra; (2) VNIR and TIR reflectance spectra of particle-size separates derived from the bulk rock and from materials extracted from fractures/vesicles; (3) X-ray diffraction (XRD) patterns for determination of quantitative modal mineralogy; (4) major element chemistry using flux fusion of whole-rock powders; and (5) electron microprobe analyses of minerals in thin sections. Conclusions about aqueous alteration can be influenced by technique. For these basalts, whole-rock chemical data showed scant evidence for chemical fractionation, but TIR, VNIR, and XRD measurements identified distinctive assemblages of hydrous silicate minerals, differing by sample. XRD provided the most complete and accurate quantitative determination of sample mineralogy. However, VNIR spectroscopy was the technique most useful for determining composition of low-abundance smectite clays, and TIR spectroscopy was the most useful for recognizing hydrated silicates in thin surface coatings. High spatial resolution mineralogical and chemical data sets were useful for understanding the texture and distribution of alteration products and variations in fluid chemistry. No single approach provides a complete assessment of the environment of alteration, demonstrating the importance of employing multiple, synergistic mineralogical and geochemical techniques and instruments in exploration of rock strata from aqueous paleoenvironments on Mars.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2012JE004156DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2012JE004156/abstractPublisherArticle
ORCID:
AuthorORCID
Ehlmann, B. L.0000-0002-2745-3240
Additional Information:© 2012 American Geophysical Union. Received 6 June 2012; revised 16 August 2012; accepted 20 August 2012; published 13 October 2012. This work benefited from the invaluable advice and laboratory assistance provided by Dave Murray (flux fusion analysis), Joe Orchardo (ICP-OES), Bill Collins (thin section preparation), Joe Devine (microprobe), Taki Hiroi (RELAB spectral measurements), Miles Watkins (rock sample cataloging), and Michael Cheshire (XRD measurement assistance). Thanks to Mike Wyatt, Ulyana Horodyskyj, and Richard Lewis for supporting field work and comments by Christina Viviano and an anonymous reviewer, which improved this work.
Subject Keywords: XRD; clay minerals; hydrothermal alteration; infrared spectroscopy; weathering; zeolites
Issue or Number:E11
Record Number:CaltechAUTHORS:20140224-092155309
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140224-092155309
Official Citation:Ehlmann, B. L., D. L. Bish, S. W. Ruff, and J. F. Mustard (2012), Mineralogy and chemistry of altered Icelandic basalts: Application to clay mineral detection and understanding aqueous environments on Mars, J. Geophys. Res., 117, E00J16, doi:10.1029/2012JE004156.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43941
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Feb 2014 23:39
Last Modified:09 Mar 2020 13:18

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