We report on experiments with Mars analog materials under diagenetic conditions and find characteristic chemical surface changes in correspondence with the fluid conditions

Bridges, J. C.

Bullock, M. A.

Chavez, C.

Filiberto, J.

Hicks, L. J.

Kelley, S. P.

McIntosh, R. A.

Miller, M. A.

Moore, J. M.

Ott, U.

Schwenzer, S. P.

Smith, H.

Swindle, T. D.

Treiman, A. H.

English

Open Research Online (Open)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsMineral Surface and Fluid Chemistry in NakhliteAnalog Water-Rock ReactionsConference or Workshop ItemHow to cite:Miller, M. A.; Schwenzer, S. P.; Bridges, J. C.; Hicks, L. J.; Ott, U.; Filiberto, J.; Chavez, C.; Smith, H.;Treiman, A. H.; Kelley, S. P.; Moore, J. M.; Swindle, T. D.; Bullock, M. A. and McIntosh, R. A. (2018). MineralSurface and Fluid Chemistry in Nakhlite Analog Water-Rock Reactions. In: 49th Lunar and Planetary ScienceConference, 19-23 Mar 2018, The Woodlands, Houston, Texas, USA.For guidance on citations see FAQs.c© [not recorded]Version: Version of RecordLink(s) to article on publisher’s website:https://www.hou.usra.edu/meetings/lpsc2018/pdf/1688.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukMINERAL SURFACE AND FLUID CHEMISTRY IN NAKHLITE ANALOG WATER-ROCK REACTIONS.  M. A. Miller1, S. P. Schwenzer2, J. C. Bridges3, L. J. Hicks3, U. Ott4,5, J. Filiberto2,6, C. Chavez7, H. Smith7, A. H. Treiman8, S. P. Kelley2, J. M. Moore7, T. D. Swindle9, M. A. Bullock10, R. A. McIntosh1, – 1Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas 78228 (mmiller@swri.org); 2The Open University, Mil-ton Keynes, UK; 3Space Research Centre, University of Leicester, UK; 4ATOMKI, Debrecen, Hungary, 5MPI, Mainz, Germany 6Southern Illinois University, Carbondale, IL, USA; 7NASA Ames Research Center, Moffett Field, CA USA; 8Lunar and Planetary Institute, USRA, Houston, TX, USA; 9Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA; 10Southwest Research Institute, Boulder, CO USA.  Introduction:  Water and fluid chemistry are central to the question of Martian habitability. On Earth, ser-pentinization of olivine, especially Fe-bearing fayalite, provides molecular hydrogen as an energy source and as a source of electrons [1-3], which can be efficiently utilized by chemosynthetic organisms [4]. This also holds for Martian rocks [5]. Water serves as the solvent to ena-ble alteration, but its composition matters – even if life can adapt to a wide range of conditions [6-11]. Thus, those factors are a focal point of Martian research in-cluding landed missions [12-14], meteorite investiga-tions, analog studies [15-21], and the predictions of possible biomarkers (e.g., [22]). In this study, we con-duct experimental and geochemical modeling investi-gations to study the pairing of mineral surface–fluid chemistry under circumneutral Martian analog condi-tions, such as those expected on Amazonian Mars based on the nakhlite meteorites [19]. Experiment and methods:  Water-rock reaction experiments were conducted in the Aqueous Simula-tion Facility at NASA Ames [23,24], with alteration experiments at 35 °C under simulated Mars atmosphere (98 % CO2 and 2 % Ar, 30 ppm Kr and 8 ppm Xe), lasting 1, 3, and 9 months (Run 1, 2, and 3). We used a variety of mineral mixtures to approximate the miner-alogies of Martian rocks, including the nakhlite mete-orites (Tab. 1). Here we report on newly measured fluids, and mineral surface chemistry and mineralogy. Earlier results were reported by Bullock et al. [25] and Schwenzer et al. [26-28]; further new results are re-ported in two other LPSC 2018 contributions [29,30].  Analytical methods are as follows. Grains of minerals from the reaction vessels were imaged under a scan-ning electron microscope (FEI Quanta 650 SEM at SwRI).  Elemental abundances were measured with an energy dispersive X-ray spectrometer (EDS, IXRF Systems).  Mineral alterations were further examined with Raman spectroscopic microanalysis (Hori-ba/Jobin-Yvon LabRam HR Evolution Raman Micro-scope at SwRI).  Chemical analyses of fluids of Run 1 were done at University of Colorado Boulder [25], and those of Run 3 at SwRI San Antonio by Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP-AES), on a Perkin Elmer Optima (Model 7300DV) and a Thermo Jarrell Ash ICAP (Model 61E) Trace Purge. Thermochemical modeling was done with CHIM-XPT, see e.g., [26-28].  Table 1. Chemical composition (wt.%) of Ol=forsterite, Pyx=augite, Plag=andesine, Fay = fay-alitic glass [26-29]. Our runs contained a variation of combinations from pure minerals, 1:1 mixtures, and mixtures of three or all four phases; also, some mix-tures contained trace phases such as apatite or pyrite, or additions such as hydrochloric acid.    Ol Pyx Plag Fay SiO2 41.8 52.1 63.4 31.84 Al2O3  2.4 21.6 4.43 TiO2  0.6  0.33 FeO 7.1 9.5 0.06 55.03 CaO 0.1 19.1 2.3 1.48 MgO 56.7 14.6  0.78 Na2O  0.3 8.6 0.38 K2O   3.8 1.23  Results: We report fluid composition and surface che-mistry. For clay mineralogy see [30], for noble gases [29]. Fluids. Concentrations of the major elements in the 9 month long run (1 month runs in brackets) cover the following ranges (in mg/L; Fig. 1): sodium 0.4 to 11.8 (0.5 to 5.7), potassium 0.5 to 9.2 (0.5 to 4.6), magnesi-um 0.07 to 270 (1.6 to 248), calcium 1.72 to 82.6 (6.46 to 99.6), manganese 0.007 to 1.63 (0.12 to 1.21), iron 0.151 to 0.213 but mostly below detection limit (below detection limit), aluminium 0.079 to 3.42 but often below detection limit (~0.11, but mostly below detec-tion limit), silicon 1.16 to 89.9 (12.2 to 56.2), and sul-phur 0.071 to 102 (0.478 to 2.14). Models.  Modelling a composition of 30 % Fay, 20 % Ol, 25 % Plag, 25 % Pyx, results in an overlap of Na/Mg ratios between our models and the measured fluids at around W/R of 5000–6000. Taking into ac-count the observation that olivine and plagioclase dis-solve more readily than the fayalitic glass, results in a starting composition of 50 % ol, 40 % plag, and 5 % of Fay and Pyx each. In this case, the Na/Mg ratio of the models match the measured fluids at about W/R 3000. However, Ca/Na and K/Na ratios are lower in the mod-els than in the measured fluids, with a lower Ca/Na in the more realistic model due to less Ca in the starting composition. 1688.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)Fig. 1. Plot from [10] with experimental fluids from this study added. a) Na vs K, b) Na vs Ca, c) Na vs Mg. For References in brackets, see [10].  Surface mineralogy.  Raman investigation of the mineral surfaces showed compositional alterations after only one month, the most salient of which occurred on the Ol grains.  Other alterations included magnesite and calcite phases, which occurred in mixtures containing Ol+Plag.  Discussion:  Fig. 1 shows a comparison of our ex-perimental fluids with a range of terrestrial, Mars ana-log experimental and modeled fluids, and two models from this study. Our fluids are comparably low in Na, especially compared to Icelandic fluids, but have great-er K abundances than fluids with similar Na concentra-tions (Fig.1a). This is likely due to the nature of plagi-oclase and the fayalitic glass (Tab. 1), but also suggests that the Icelandic fluids have a sea salt contribution, either by seawater or salt spray. Ca and Mg concentra-tions are well within the range of other experimental fluids (Fig.1b,c). Our modeled fluids are lower in K and Ca than the measured fluids, which indicates leach-ing rather than full dissolution and will be investigated further. However, measured Ca concentrations are sim-ilar to, but Mg concentrations are higher than modeled Martian fluids, which reflects the clay formation pro-cesses, dominated by serpentine in our experiment [19]. In the models Fe-Mg clay are precipitated when modeling the experiments and when modeling Martian fluids [e.g., 8,10]. This will be investigated further. References: [1] Oze, C. & Sharma, M. (2007) Icarus, 186: 557–561 [2] Schulte,M., et al. (2006) Astrobiology, 6: 364-376. [3] Stevens, T. O. & McKinley, J. P. (1995) Sci-ence, 270: 450-455. [4] McCollom, T. M. (2007) Astrobiol-ogy, 7: 933-950. [5] Varnes, E. S., et al. (2003) Astrobiolo-gy, 3: 407–414 [6] Fisk, M. R. & Giovannoni, S. J. (1999) JGR, 104: 11805-11815. [7] Rothschild, L. J. & Mancinelli, R. L. (2001) Nature, 409: 1092-1101. [8] Westall, F. et al. (2013) Astrobiology, 13: 887-897. [9] Tosca, N. J., et al. (2008) Science, 320: 1204–1207. [10] Fox-Powell, M. G. et al. (2016) Astrobiology, 16: 427-442. [11] Cockell, C. S. et al. (2016) Astrobiology, 16: 89-117. [12] Grotzinger, J. P. et al. (2014) Science, 343, DOI: 10.1126/science.1242777. [13] Squires, S. W. et al. (2004) Science, 306: 1698-1703 [14] Squires, S .W. et al. (2004), Science, 305: 794-799. [15] Hurowitz, J. A., and McLennan, S. (2007): EPSL, 260: 432-443. [16] Tosca, N. J. et al. (2008): Science, 320: 1204-1207. [17] Schulte, M. et al. (2006): Astrobiology, 6: 364-376. [18] Filiberto, J. et al. (2014): EPSL, 401: 110-115. [19] Bridges, J. C., Schwenzer, S. P. (2012): EPSL, 359-360: 117-123. [20] Leveille, R. et al. (2014): JGR, 119: 2398–2415. [21] Schwenzer et al. (2016) MAPS, 51: 2175–2202 [22] Olsson-Francis, K. et al. (2017): Front. Microbiology, doi: 10.3389/fmicb.2017.01668. [23] Bullock M.A., et al. (2004): Icarus 170, 404-423. [24] Moore J.M., and Bullock M.A. (1999): JGR. 104: 21925–21934. [25] Bullock, M. A., et al. (2015): 46th LPSC, abstr. #1235. [26] Schwenzer et al. (2016): 47th LPSC, abstract 1889.  [27] S. P. Schwenzer et al. (2016) 79th Annual Meeting of the Meteoritical Society, abstr #6099. [28] Schwenzer, S. P., et al. (2017): 48th LPSC, abstr. # 1344. [29] Schwenzer et al., this conference. [30] Bridges et al., this conference. Acknowledgement:  We acknowledge funding through NASA MFRP grant Grant NNX14AJ94G.  1688.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)

Mineral Surface and Fluid Chemistry in Nakhlite Analog Water-Rock Reactions

Mineral Surface and Fluid Chemistry in Nakhlite Analog Water-Rock Reactions

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