Spectroscopic examinations of hydro- and glaciovolcanic basaltic tuffs: Modes of alteration and relevance for Mars

Abstract

a b s t r a c tHydro-and glaciovolcanism are processes that have taken place on both Earth and Mars. The amount of materials produced by these processes that are present in the martian surface layer is unknown, but may be substantial. We have used Mars rover analogue analysis techniques to examine altered tuff samples collected from multiple hydrovolcanic features, tuff rings and tuff cones, in the American west and from glaciovolcanic hyaloclastite ridges in Washington state and in Iceland. Analysis methods include VNIR-SWIR reflectance, MWIR thermal emissivity, thin section petrography, XRD, XRF, and Mössbauer spectroscopy. We distinguish three main types of tuff that differ prominently in petrography and VNIR-SWIR reflectance: minimally altered sideromelane tuff, gray to brown colored smectite-bearing tuff, and highly palagonitized tuff. Differences are also observed between the tuffs associated with hydrovolcanic tuff rings and tuff cones and those forming glaciovolcanic hyaloclastite ridges. For the locations sampled, hydrovolcanic palagonite tuffs are more smectite and zeolite rich while the palagonitized hyaloclastites from the sampled glaciovolcanic sites are largely devoid of zeolites and relatively lacking in smectites as well. The gray to brown colored tuffs are only observed in the hydrovolcanic deposits and appear to represent a distinct alteration pathway, with formation of smectites without associated palagonite formation. This is attributed to lower temperatures and possibly longer time scale alteration. Altered hydroor glaciovolcanic materials might be recognized on the surface of Mars with rover-based instrumentation based on the results of this study.

Determining the Volcanic Eruption Style of Tephra Deposits From Infrared Spectroscopy

“…Devitrified glass can be differentiated from glass in TIR spectra and indicates distinct thermal conditions after emplacement (Farrand et al., 2016). TIR models of both welded ignimbrites and hydrovolcanic tephra are dominated by devitrified glass, indicating prolonged thermal alteration, but the hydrovolcanic tephra often also exhibits strong clay mineral absorptions, allowing us to specifically infer hydrothermal alteration (Ehlmann & Mustard, 2012; Farrand et al., 2018). Similarly, accretionary lapilli exhibit evidence for aqueous alteration in the VNIR but are dominated by glass in both VNIR and TIR, suggesting that alteration occurred under cooler and more water‐limited conditions.…”

“…All rights reserved. Farrand et al, 2018]. Similarly, accretionary lapilli exhibit evidence for aqueous alteration in the VNIR but are dominated by glass in both VNIR and TIR, suggesting that alteration occurred under cooler and more water-limited conditions.…”

“…Crystallinity was determined from TIR linear deconvolution models by subtracting from 100 the fraction of unambiguously amorphous phases (glass, devitrified glass, partially to fully amorphous silica phases) as well as clay, oxide, and zeolite phases that are difficult to quantify using XRD and/or may be poorly crystalline when present in palagonites (S. E. Ackiss et al., 2018a; Farrand et al., 2018). Previous studies of crystalline igneous rocks suggested that TIR‐derived abundances are accurate within 15 vol.% (Feely & Christensen, 1999).…”

“…Thus, these crystallinities are not just a measure of the glass content but also the presence of other X-ray amorphous phases, including assemblages like palagonite [Ackiss et al, 2018a]. Palagonite is an assemblage of largely amorphous phases that forms due to hydrothermal alteration of glass during or shortly after an eruption [Allen et al, 1981;Stroncik and Schmincke, 2001;2002;Drief and Schiffman, 2004;Pauly et al, 2011;Ackiss et al, 2018a;Farrand et al, 2018]. Bulk crystallinity (groundmass/phenocrysts), as well as groundmass crystallinity (phenocrysts removed by hand) for our samples, were inferred from XRD models by Wall et al (2014).…”

An overview of explosive volcanism on Mars

“…10c) within the Home Plate exposure suggests that the deposits originate from hydrovolcanic activity within the Gusev crater itself (Lewis et al, 2008) as a volcanic bomb would not be expected more than 350 m from its source (Manga et al, 2012). Recent studies additionally suggest that the rover-based instruments on board Mars Science Laboratory (MSL) rover Curiosity may be used to distinguish whether altered tuff samples, if detected, were formed by hydro-or glaciovolcanic activity (Farrand et al, 2018), which is giving a prospect to detect direct evidence of hydrovolcanism on Mars in the future.…”