Chemical alteration of fine-grained sedimentary rocks at Gale crater

Nicolas Mangold, E. Dehouck, C. Fedo, Olivier Forni, C. Achilles, T. Bristow, R. T. Downs, J. Frydenvang, Olivier Gasnault, J. L'Haridon, L. Le Deit, Sylvestre Maurice, S. M. McLennan, Pierre-Yves Meslin, S. Morrison, H. E. Newsom, E. Rampe, William Rapin, F. Rivera-Hernandez, M. Salvatore

    21 Citationer (Scopus)

    Abstract

    From Sol 750 to 1550, the Curiosity rover documented>100 m thick stack of fine-grained sedimentary rocks making up part of the Murray formation, at the base of Mt Sharp, Gale crater. Here, we use data collected by the ChemCam instrument to estimate the level of chemical weathering in these sedimentary rocks. Both the Chemical Index of Alteration (CIA) and the Weathering Index Scale (WIS) indicate a progressive increase in alteration up section, reaching values of CIA of 63 and WIS of 25%. The increase in CIA and WIS values is coupled with a decrease in calcium abundance, suggesting partial dissolution of Ca-bearing minerals (clinopyroxene and plagioclase). Mineralogy from the CheMin X-ray diffraction instrument indicates a decrease in mafic minerals compared with previously analyzed strata and a significant proportion of phyllosilicates consistent with this interpretation. These observations suggest that the sediments were predominantly altered in an open system, before or during their emplacement, contrasting with the rock-dominated conditions inferred in sedimentary deposits analyzed at Yellowknife Bay.

    OriginalsprogEngelsk
    TidsskriftIcarus
    Vol/bind321
    Sider (fra-til)619-631
    Antal sider13
    ISSN0019-1035
    DOI
    StatusUdgivet - 15 mar. 2019

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