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Pyroxene weathering to smectite: Conventional and cryo-field emission scanning electron microscopy, Koua Bocca ultramafic complex, Ivory Coast

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Clays and Clay Minerals

Abstract

Air-dried and high-pressure frozen/freeze-etched samples of clinopyroxene and smectite in a saprolitized clinopyroxenite from Koua Bocca, Ivory Coast, West Africa, were compared to characterize textures developed during natural weathering of chain silicates. Comparison with air-dried material allowed evaluation of high-pressure cryofixation as a technique for preserving textures of hydrated clay minerals. Air-dried pyroxene surfaces appear very smooth. Small, flat lamellae, oriented parallel to the c axis, lend a distinct splintery appearance to pyroxene surfaces in fully hydrated samples. These lamellae often display a combination of straight (110) pyroxene edges and a crinkled border, suggestive of smectite. Narrow lenticular (110) open cleavages occur in both preparations and are not a pressurization artifact. Most often these openings contain no secondary minerals. Spaces between pyroxene denticles, lined with collapsed smectite in air-dried samples, are filled with thin packets of anhedral smectite crystallites oriented face to face when hydrated. Smectite microboxwork preserves original topotactic textures developed during isovolumetric pyroxene transformation, and smaller nanoporosity appears in hydrated cryofixed examples. Occasional regions of edge-to-face ‘house of cards’ texture also occur. Elimination of sample preparation artifacts induced by surface tension during air drying demonstrates that pores actually present during a hydration reaction-driven weathering episode are smaller and more numerous than would be inferred from examining air-dried materials.

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References

  • Banfield, J.F. and Barker, W.W. (1994) Direct observation of reactant-product interfaces formed in natural weathering of exsolved, defective amphibole to smectite; evidence for episodic, isovolumetric reactions involving structural inheritance. Geochimica et Cosmochimica Acta, 58, 1419–1429.

    Article  Google Scholar 

  • Berner, E.K. and Berner, R.A. (1996) Global Environment: Water, Air, and Geochemical Cycles. Prentice-Hall, Englewood Cliffs, New Jersey, USA.

    Google Scholar 

  • Berner, R.A. and Schott, J. (1982) Mechanism of pyroxene and amphibole weathering — II. Observations of soil grains. American Journal of Science, 282, 1214–1231.

    Article  Google Scholar 

  • Berner, R.A., Sjöberg, E.L., Velbel, M.A., and Krom, M.D. (1980) Dissolution of pyroxenes and amphiboles during weathering. Science, 207, 1205–1206.

    Article  Google Scholar 

  • Bowser, C.J. and Jones, B.F. (2002) Mineralogic controls on the composition of natural waters dominated by silicate hydrolysis. American Journal of Science, 302, 582–662.

    Article  Google Scholar 

  • Brantley, S.L. (2005) Reaction kinetics of primary rock-forming minerals under ambient conditions. Pp. 73–117 in: Surface and Ground Water, Weathering, and Soils (J.I. Drever, editor). Treatise on Geochemistry vol. 5 (edH.D. Holland and K.K. Turekian, editors). Elsevier-Pergamon, Oxford, UK.

    Google Scholar 

  • Brantley, S.L. and Chen, Y. (1995) Chemical weathering rates of pyroxenes and amphiboles. Pp. 119–172 in: Chemical Weathering Rates of Silicate Minerals (A.F. White and S.L. Brantley, editors). Reviews in Mineralogy, vol. 31, Mineralogical Society of America, Washington, D.C.

    Chapter  Google Scholar 

  • Bricker, O.P., Jones, B.F., and Bowser, C.J. (2005) Mass-balance approach to interpreting weathering reactions in watershed systems. Pp. 119–132 in: Surface and Ground Water, Weathering, and Soils (J.I. Drever, editor). Treatise on Geochemistry vol. 5 (H.D. Holland and K.K. Turekian, editors). Elsevier-Pergamon, Oxford, UK.

    Google Scholar 

  • Casey, W.H., Banfield, J.F., Westrich, H.R., and McLaughlin, L. (1993) What do dissolution experiments tell us about natural weathering? Chemical Geology, 105, 1–15.

    Article  Google Scholar 

  • Cole, W.F. and Lancucki, C.J. (1976) Montmorillonite pseudomorphs after amphibole from Melbourne, Australia. Clays and Clay Minerals, 24, 79–83.

    Article  Google Scholar 

  • Colin, F., Nahon, D., Trescases, J.J., and Melfi, A.J. (1990) Lateritic weathering of pyroxenites at Niquelandia, Goias, Brazil: The supergene behavior of nickel. Economic Geology, 85, 1010–1023.

    Article  Google Scholar 

  • Courchesne, F., Turmel, M.-C., and Beauchemin, P. (1996) Magnesium and potassium release by weathering in Spodosols: Grain surface coating effects. Soil Science Society of America Journal, 60, 1188–1196.

    Article  Google Scholar 

  • Dahl, R. and Staehelin, A.A. (1989) High-pressure freezing for the preservation of biological structure: theory and practice. Journal of Electron Microscopy Technique, 13, 165–174.

    Article  Google Scholar 

  • Delvigne, J. (1983) Micromorphology of the alteration and weathering of pyroxenes in the Koua Bocca ultramafic intrusion, Ivory Coast, West Africa. Pp. 57–68 in: Pétrologie des Altérations et des Sols, Volume II (D. Nahon and Y. Noack, editors). Sciences Géologiques, Mémoires (Strasbourg), vol. 72.

    Google Scholar 

  • Delvigne, J. (1990) Hypogene and supergene alterations of orthopyroxene in the Koua Bocca ultramafic intrusion, Ivory Coast. Chemical Geology, 84, 49–53.

    Article  Google Scholar 

  • Delvigne, J. (1998) Atlas of Micromorphology of Mineral Alteration and Weathering. The Canadian Mineralogist, Special Publication 3, 495 pp.

  • Eggleton, R.A. (1975) Nontronite topotaxial after hedenbergite. American Mineralogist, 60, 1063–1068.

    Google Scholar 

  • Eggleton, R.A. and Boland, J.N. (1982) Weathering of enstatite to talc through a sequence of transitional phases. Clays and Clay Minerals, 30, 11–20.

    Article  Google Scholar 

  • Fisk, M.R., Popa, R., Mason, O.U., Storrie-Lombardi, M.C., and Vicenzi, E.P. (2006) Iron-magnesium silicate bio-weathering on Earth (and Mars?). Astrobiology, 6, 48–68.

    Article  Google Scholar 

  • Hochella, M.F., Jr., and Banfield, J.F. (1995) Chemical weathering of silicates in nature: A microscopic perspective with theoretical considerations. Pp. 353–406 in: Chemical Weathering Rates of Silicate Minerals (A.F. White and S.L. Brantley, editors). Reviews in Mineralogy, vol. 31, Mineralogical Society of America, Washington, D.C.

    Chapter  Google Scholar 

  • McKay, D.S., Gibson, E.K., Jr., Thomas-Keprta, K.L., Vali, H., Romanek, C.S., Clemett, S.J., Chillier, X.D.F., Maechling, C.R., and Zare, R.N. (1996) Search for past life on Mars: possible relic biogenic activity in Martian meteorite ALH84001. Science, 273, 924–930.

    Article  Google Scholar 

  • Nahon, D.B. (1991) Introduction to the Petrology of Soils and Chemical Weathering. J. Wiley, New York.

    Google Scholar 

  • Nahon, D.B. and Colin, F. (1982) Chemical weathering of orthopyroxenes under lateritic conditions. American Journal of Science, 282, 1232–1243.

    Article  Google Scholar 

  • Nugent, M.A., Brantley, S.L., Pantano, C.G., and Maurice, P.A. (1998) The influence of natural mineral coatings on feldspar weathering. Nature, 395, 588–591.

    Article  Google Scholar 

  • Pačes, T. (1983) Rate constants of dissolution derived from the measurements of mass balance in hydrological catchments. Geochimica et Cosmochimica Acta, 47, 1855–1863.

    Article  Google Scholar 

  • Proust, D., Caillaud, J., and Fontaine, C. (2006) Clay minerals in early amphibole weathering: Tri- to dioctahedral sequence as a function of crystallization sites in the amphibole. Clays and Clay Minerals, 54, 351–362.

    Article  Google Scholar 

  • Ransom, B. and Helgeson, H.C. (1994) Estimation of the standard molal heat capacities, entropies, and volumes of 2:1 clay minerals. Geochimica et Cosmochimica Acta, 58, 4537–4547.

    Article  Google Scholar 

  • Schaetzl, R.J., Mikeseil, L.R., and Velbel, M.A. (2006) Soil characteristics related to weathering and pedogenesis across a geomorphic surface of uniform age in Michigan. Physical Geography, 27, 170–188.

    Article  Google Scholar 

  • Schott, J. and Berner, R.A. (1983) X-ray photoelectron studies of the mechanism of iron silicate dissolution during weathering. Geochimica et Cosmochimica Acta, 47, 2233–2240.

    Article  Google Scholar 

  • Schott, J., Berner, R.A., and Sjoberg, E.L. (1981) Mechanism of pyroxene and amphibole weathering — I. Experimental studies of iron-free minerals. Geochimica et Cosmochimica Acta, 45, 2123–2135.

    Article  Google Scholar 

  • Smyth, J.R. and Bish, D.L. (1988) Crystal Structures and Cation Sites of the Rock-Forming Minerals. Allen & Unwin, Boston, USA.

    Google Scholar 

  • Velbel, M.A. (1985) Geochemical mass balances and weathering rates in forested watersheds of the southern Blue Ridge. American Journal of Science, 285, 904–930.

    Article  Google Scholar 

  • Velbel, M.A. (1986) Influence of surface area, surface characteristics, and solution composition on feldspar weathering rates. Pp. 615–634 in: Geochemical Processes at Mineral Surfaces (J.A. Davis and K.F. Hayes, editors). ACS Symposium Series, No. 323, American Chemical Society.

  • Velbel, M.A. (1989a) Weathering of hornblende to ferruginous products by a dissolution-reprecipitation mechanism: petrography and stoichiometry. Clays and Clay Minerals, 37, 515–524.

    Article  Google Scholar 

  • Velbel, M.A. (1989b) Effect of chemical affinity on feldspar hydrolysis rates in two natural weathering systems. Chemical Geology, 78, 245–253.

    Article  Google Scholar 

  • Velbel, M.A. (1990) Influence of temperature and mineral surface characteristics on feldspar weathering rates in natural and artificial systems: A first approximation. Water Resources Research, 26, 3049–3053.

    Google Scholar 

  • Velbel, M.A. (1993a) Formation of protective surface layers during silicate-mineral weathering under well-leached, oxidizing conditions. American Mineralogist, 78, 408–417.

    Google Scholar 

  • Velbel, M.A. (1993b) Constancy of silicate-mineral weathering-rate ratios between natural and experimental weathering: Implications for hydrologic control of differences in absolute rates. Chemical Geology, 105, 89–99.

    Article  Google Scholar 

  • Velbel, M.A. (2004) Laboratory and homework exercises in the geochemical kinetics of mineral-water reaction: rate law, Arrhenius activation energy, and the rate-determining step in the dissolution of halite. Journal of Geoscience Education, 52, 52–59.

    Article  Google Scholar 

  • Velbel, M.A. (2007) Surface textures and dissolution processes of heavy minerals in the sedimentary cycle: examples from pyroxenes and amphiboles. Pp. 113–150 in: Heavy Minerals in Use (M. Mange and D. Wright, editors). Developments in Sedimentology, 58, Elsevier, Amsterdam.

    Chapter  Google Scholar 

  • Wentworth, S.J., Gibson, E.K., Velbel, M.A., and McKay, D.S. (2005) Antarctic dry valleys and indigenous weathering in Mars meteorites: implications for water and life on Mars. Icarus, 174, 382–395.

    Article  Google Scholar 

  • White, A.F. and Brantley, S.L. (2003) The effect of time on the weathering of silicate minerals: why do weathering rates differ in the laboratory and field? Chemical Geology, 202, 479–506.

    Article  Google Scholar 

  • Wilson, M.J. (1986) Mineral weathering processes in podzolic soils on granitic materials and their implications for surface water acidification. Journal of the Geological Society, London, 143, 691–697.

    Article  Google Scholar 

  • Wilson, M.J. (2004) Weathering of the primary rock-forming minerals; processes, products and rates. Clay Minerals, 39, 233–266.

    Article  Google Scholar 

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Authors and Affiliations

  1. Department of Geological Sciences, Michigan State University, 206 Natural Science Building, East Lansing, MI, 48824-1115, USA

    Michael A. Velbel

  2. Department of Geology and Geophysics, University of Wisconsin-Madison, Madison, WI, 53706, USA

    William W. Barker

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  1. Michael A. Velbel
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  2. William W. Barker
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Correspondence to Michael A. Velbel.

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Velbel, M.A., Barker, W.W. Pyroxene weathering to smectite: Conventional and cryo-field emission scanning electron microscopy, Koua Bocca ultramafic complex, Ivory Coast. Clays Clay Miner. 56, 112–127 (2008). https://doi.org/10.1346/CCMN.2008.0560110

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  • DOI: https://doi.org/10.1346/CCMN.2008.0560110

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