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Reaction Mechanisms of Smectite Illitization Associated with Hydrothermal Alteration from Ponza Island, Italy

Published online by Cambridge University Press:  28 February 2024

Robert F. Ylagan ,
Stephen P. Altaner  and
Antonio Pozzuoli
Robert F. Ylagan*
Affiliation:
University of Illinois, Department of Geology, 1301 W. Green, Urbana, Illinois 61801 USA
Stephen P. Altaner
Affiliation:
University of Illinois, Department of Geology, 1301 W. Green, Urbana, Illinois 61801 USA
Antonio Pozzuoli
Affiliation:
Universita degli Studi di Napoli ‘Federico II’, Dipartimento di Geofisica e Vulcanologia, Largo S. Marcellino 10, 80138 Napoli, Italy
*
†Present address: ExxonMobil Upstream Research Co., P.O. Box 2189, Houston, Texas 77252-2189, USA.
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Abstract

A hydrothermally altered rhyolitic hyaloclastite from Ponza island, Italy, has four alteration zones with unique clay assemblages: (1) a non-pervasive argillic zone characterized by smectite; (2) a propylitic zone with interstratified illite-smectite (I-S) containing 10–85% illite (I); (3) a silicic zone composed of I-S with ≥90% I and pure illite; and (4) a sericitic zone with I-S ranging from 66% I to pure illite. Atomic force microscopy reveals abrupt changes in particle morphology with illitization, including initial changes from anhedral plates to laths and then to euhedral plates and hexagonal plates. I-S particles progressively thicken with illitization and mean particle area (basal plane) remains constant from pure smectite to I-S with 80% I. However, particle area increases from 90 to 100% illite. Computer modeling of I-S structural forms indicates octahedral cation ordering progressively changes from cis- vacant smectite to interstratified cis- and tnuis-vacant I-S, and then to trans-vacant illite. In addition, polytypes progressively change from 1 Md to 1M, and then to 2M, illite. Electron-microprobe and X-ray fluoresence analyses show that I-S chemistry progressively changes during illitization, evolving toward a phengitic composition with ∼0.89 fixed interlayer K+ per O10(OH)2. Octahedral Mg2+ shows little change with illitization, varying from 0.3 to 0.5 cations per O,10(OH)2. The layer charge of smectite is ~0.38 equivalents per O10(OH)2.

On the basis of abrupt changes in morphology and progressive changes in polytype and chemistry, smectite illitization on Ponza involved a dissolution and recrystallization mechanism with multiple stages of nucléation and crystal growth. In this multi-step model, temperature of alteration provided the major control for the layer composition, polytype, and morphology of I-S crystallites. Other factors that may play a secondary role include: K+ availability, water-rock ratio, and permeability. Alternatively, the mechanism of I-S and illite formation at Ponza and other hydrothermal environments may occur by direct precipitation of I-S crystallites from rhyolite glass and may not involve progressive reactions of smectite precursors.

Keywords

Atomic Force MicroscopyChemical AnalysisIllitePolytypeSmectiteXRD
Type
Research Article
Information
Clays and Clay Minerals , Volume 48 , Issue 6 , December 2000 , pp. 610 - 631
Copyright
Copyright © 2000, The Clay Minerals Society

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References

Ahn, J.-H. and Peacor, D.R., (1986) Transmission and analytical electron microscopy of the smectite-to-illite transition Clays and Clay Minerals 34 165–179 10.1346/CCMN.1986.0340207.Google Scholar
Altaner, S.P. and Ylagan, R.F., (1997) Comparison of stmctural models of mixed-layer illite-smectite and reaction mechanisms of smectite illitization Clays and Clay Minerals 45 517–533.CrossRefGoogle Scholar
Altaner, S.P. Weiss, C.A. and Kirkpatrick, R.J., (1988) Evidence from 29Si NMR for the structure of mixed layer illitesmectite clay minerals Nature 331 699–702.CrossRefGoogle Scholar
Awwiller, D.N., (1993) Illite-smectite formation and potassium mass transfer during burial diagenesis of mudrocks: A study from the Texas Gulf Coast Paleocene-Eocene Journal of Sedimentary Petrology 63 501–512.Google Scholar
Barberi, E. Borsi, S. Ferrara, G. and Innocenti, F., (1967) Contributo alia conoscenza vulcanologica e magmatologica delle Isole dell’Arcipelago Pontino Memorie della Societa Geologica Italiana 6 581–606.Google Scholar
Barronnet, A., (1982) Ostwald Ripening in solutions: The case of calcite and mica Estudios Geologicos 38 185–198.Google Scholar
Baronnet, A. and Buseck, P.R., (1992) Polytypism and stacking disorder Minerals and Reactions at the Atomic Scale: Transmission Electron Microscopy Michigan Mineralogical Society of America, Chelsea 231–288.CrossRefGoogle Scholar
Baxter Grubb, S.M. Peacor, D.R. and Jiang, W.-T., (1991) Transmission electron microscope observations of illite polytypism Clays and Clay Minerals 30 540–550.CrossRefGoogle Scholar
Beccaluva, L. Brotzu, P. Macciotta, G. Morbidelli, L. Serri, G. Traversa, G., Bonafede, M. B. Piccardo, G.B. and Vai, G.B., (1989) Cainozoic tectono-magmatic evolution and inferred mantle sources in the Sardo-Tyrrhenian area The Lithosphere in Italy Rome Accademia Nazionale dei Lincei 229–248.Google Scholar
Bethke, C.M. Vergo, N. and Altaner, S.P., (1986) Pathways of smectite illitization Clays and Clay Minerals 34 125–135.CrossRefGoogle Scholar
Blum, A., Nagy, K.L. and Blum, A., (1994) Determination of illite-smectite particle morphology using scanning force microscopy Scanning Probe Microscopy of Clay Minerals Colorado Clay Mineral Society, Boulder 171–202.Google Scholar
Brusewitz, A., (1986) Chemical and physical properties of Paleozoic potassium bentonites from Kinnekulle, Sweden Clays and Clay Minerals 34 442–454.CrossRefGoogle Scholar
Capaldi, G. Civetta, L. and Gillot, P.Y., (1985) Geochronology of Plio-Pleistocene volcanic rocks from southern Italy Rendiconti della Societa Italiana Minerologica Petrologia 40 25–44.Google Scholar
Carmassi, M. De Rita, D. Di Filippo, M. Funiciello, R. and Sheridan, M.F., (1983) Geology and volcanic evolution of the island of Ponza, Italy Geologica Roma 22 211–232.Google Scholar
Christidis, G.E., (1995) Mechanism of illitization of bentonites in the geothermal field of Milos Island, Greece: Evidence based on mineralogy, chemistry, particle thickness and morphology Clays and Clay Minerals 43 569–585.CrossRefGoogle Scholar
Christidis, G. and Dunham, A.C., (1993) Compositional variations in smectites: Part I: Alteration of intermediate volcanic rocks. A case study from Milos Island, Greece Clay Minerals 28 255–273.CrossRefGoogle Scholar
Civetta, L. Francalanci, L. Manetti, P. Peccerillo, A., Boriani, A. Bonafede, M. Piccardo, G.B. and Vai, G.B., (1989) Petrological and geochemical variations across the Roman comagmatic province: Inference on magma genesis and crust-mantle evolution The Lithosphere in Italy Rome Accademia Nazionale dei Lincei 249–269.Google Scholar
Clauer, N. Furlan, S. and Chaudhuri, S., (1995) The illitization process in deeply buried shales of the Gulf Coast area Clays and Clay Minerals 43 257–259.CrossRefGoogle Scholar
Dewey, J.F., (1988) Extensional collapse of orogens Tectonics 7 1123–1139.CrossRefGoogle Scholar
Di Marco, M.J. Ferrell, R.E. and Lowe, D.R., (1989) Polytypes of 2:1 dioctahedral micas in silicified volcaniclastic sandstones, Warrawoona group, Pilbara block, western Australia American Journal of Science 289 649–660.CrossRefGoogle Scholar
Drits, V.A., Schultz, L.G. van Olphen, H. and Mumpton, F.A., (1987) Mixed-layer minerals: Diffraction methods and structural features Proceedings of the International Clay Conference, Denver, 1985 Indiana Clay Mineral Society, Bloomington 33–45.Google Scholar
Drits, V.A. Plancon, A.B. Sakharov, B.A. Besson, G. Tsipursky, S.I. and Tchoubar, C., (1984) Diffraction effects calculated for structural models of K-saturated montmorillonite containing different types of defects Clay Minerals 19 541–561.Google Scholar
Drits, V.A. Weber, F. Salyn, A.L. and Tsipursky, S.I., (1993) X-ray identification of one-layer illite varieties: Application to the study of illites around uranium deposits of Canada Clays and Clay Minerals 41 389–398.CrossRefGoogle Scholar
Drits, V.A. Salyn, A.L. and Sucha, V., (1996) Structural transformations of interstratified illite-smectite from Dolnâ Ves hydrothermal deposits: Dynamics and mechanisms Clays and Clay Minerals 44 181–190.CrossRefGoogle Scholar
Eberl, D.D. and Srodon, J., (1988) Ostwald ripening and interparticle-diffraction effects for illite crystals American Mineralogist 73 1335–1345.Google Scholar
Eberl, D.D. Srodon, J. Lee, M. Nadeau, P.H. and Northrop, H.R., (1987) Sericite from the Silverton caldera, CO: Correlation among structure, composition, origin, and particle thickness American Mineralogist 72 914–935.Google Scholar
Eberl, D.D. Srodon, J. Kralik, M. Taylor, B.E. and Peterman, Z.E., (1990) Ostwald ripening of clays and metamorphic minerals Science 248 474–477.CrossRefGoogle Scholar
Ferrara, G. and Tonarini, S., (1985) Radiometric geochronology in Tuscany: Results and problems Rendiconti della Societa Italiana Minerologica Petrologia 40 111–124.Google Scholar
Ferrara, G. Giuliani, O. Tonarini, S. and Villa, I.M., (1988) Datability and isotopic disequilibrium in anatectic volcanites from San Vincenzo and Tolfa (Tuscany-Latium) Rendiconti della Societa Italiana Minerologica Petrologia 7 72.Google Scholar
Fornaseri, M., (1985) Geochronology of volcanic rocks from Latium (Italy) Rendiconti della Societa Italiana Minerologica Petrologia 40 73–106.Google Scholar
Grim, R.E. and Güven, N., (1978) Bentonites: Geology, Mineralogy, Properties and Uses Elsevier Amsterdam.Google Scholar
Güven, N. and Grim, R., (1972) X-ray diffraction and electron optical studies on smectite and cristobalite associations Clays and Clay Minerals 20 89–92.CrossRefGoogle Scholar
Hajish, A. and Chandler, G.W., (1981) An experimental investigation of high-temperature interactions between seawater and rhyolite, andesite, basalt, and peridotite Contributions to Mineralogy and Petrology 78 240–254.CrossRefGoogle Scholar
Hawkesworth, C.J. and Vollmer, R., (1979) Crustal contamination versus enriched mantle: 143Nd/144Nd and 87Sr/86 Sr evidence from the Italian volcanics Contributions to Mineralogy and Petrology 69 151–165.CrossRefGoogle Scholar
Hower, J. and Longstaffe, F.J., (1981) Shale diagenesis Clays and the Resource Geologist 60–80.Google Scholar
Hunziker, J.C. Frey, M. Clauer, N. Dalimeyer, R.D. Friedrichsen, H. Flehmig, W. Hochstrasser, K. Roggwiler, P. and Schwander, H., (1986) The evolution of illite to muscovite: Mineralogical and isotopic data from the Glarus Alps, Switzerland Contributions to Mineralogy and Petrology 92 157–180.CrossRefGoogle Scholar
Inoue, A. and Kitagawa, R., (1994) Morphological characteristics of illitic clay minerals from a hydrothermal system American Mineralogist 79 700–711.Google Scholar
Inoue, A. and Utada, M., (1983) Further investigations of a conversion series of dioctahedral mica/smectites in the Shinzan hydrothermal alteration area, northeast Japan Clays and Clay Minerals 31 401–412.CrossRefGoogle Scholar
Inoue, A. Minato, H. and Utada, M., (1978) Mineralogical properties and occurrence of illite/montmorillonite mixed layer minerals formed from Miocene volcanic glass in Waga-Omono district Clay Science 5 123–136.Google Scholar
Inoue, A. Kohyama, N. Kitagawa, R. and Watanabe, T., (1987) Chemical and morphological evidence for the conversion of smectite to illite Clays and Clay Minerals 35 111–120.CrossRefGoogle Scholar
Inoue, A. Velde, B. Meunier, A. and Touchard, G., (1988) Mechanism of illite formation during smectite-to-illite conversion in a hydrothermal system American Mineralogist 73 1325–1334.Google Scholar
Inoue, A. Watanabe, T. Kohyama, N. and Brusewitz, A.M., (1990) Characterization of illitization of smectite in bentonite beds at Kinnekulle, Sweden Clays and Clay Minerals 38 241–249.CrossRefGoogle Scholar
Lanson, B. Velde, B. and Meunier, A., (1998) Late-stage diagenesis of illitic clay minerals as seen by decomposition of X-ray diffraction patterns: Contrasted behaviors of sedimentary basins with different burial histories Clays and Clay Minerals 46 69–78.CrossRefGoogle Scholar
Lee, J.H. Ahn, J.-H. and Peacor, D.R., (1985) Textures in layered silicates: Progressive changes through diagenesis and low-temperature metamorphism Journal of Sedimentary Petrology 55 532–540.Google Scholar
Li, G. Peacor, D.R. and Coombs, D.S., (1997) Transformation of smectite to illite in bentonite and associated sediments from Kaka Point, New Zealand: Contrast in rate and mechanism Clays and Clay Minerals 45 54–67.CrossRefGoogle Scholar
Lindgreen, H. Jacobsen, H. and Jakobsen, H.J., (1991) Diagenetic structural transformations in North Sea Jurassic illite-smectite Clays and Clay Minerals 39 54–69.CrossRefGoogle Scholar
Lombardi, G. and Mattias, P., (1981) Guidebook for the Excursions in Sardinia and Central Italy Rome Association pour l’Etude des Argiles (AIPEA).Google Scholar
Lonker, S.W. and Fitz Gerald, J.D., (1990) Formation of coexisting 1M and 2M polytypes in illite from an active hydrothermal system American Mineralogist 75 1282–1289.Google Scholar
Lupino, R., (1954) Sulla bentonite dellTsola di Ponza La Ri- cerca Scienza 24 2326–2339.Google Scholar
Lynch, F.L. Mack, L.E. and Land, L.S., (1997) Chemical and mineralogical burial-diagenesis of illite-smectite in shales and the origins of authigenic quartz and secondary porosity in sandstones Geochimica et Cosmochimica Acta 61 1995–2006.CrossRefGoogle Scholar
Marino, M.C., (1992) Caratteristiche vulcanologiche e geochimiche delle Isole di Ponza e Ventotene Italy Degree thesis, University of Naples, Naples.Google Scholar
McCarty, D.K. and Reynolds, R.C., (1995) Rotationally disordered illite-smectite in Paleozoic K-bentonites Clays and Clay Minerals 43 271–284.CrossRefGoogle Scholar
Mukhamet-Galeyev, A.P. Pokrovskiy, V.A. Zotov, A.V. Ivanov, I.P. and Samotoin, N.D., (1985) Kinetics and mechanism of hydrothermal crystallation of 2M, muscovite: An experimental study International Geological Review 27 1352–1364.CrossRefGoogle Scholar
Nadeau, P.H. and Bain, D.C., (1986) Composition of some smectites and diagenetic illitic clays and implications for their origin Clays and Clay Minerals 34 455–464.CrossRefGoogle Scholar
Nadeau, P.H. Wilson, M.J. McHardy, W.J. and Tait, J.M., (1984) Interstratified clays as fundamental particles Science 225 923–925.CrossRefGoogle ScholarPubMed
Nadeau, P.H. Wilson, M.J. McHardy, W.J. and Tait, J.M., (1985) The conversion of smectite to illite during diagenesis: Evidence from some illitic clays from bentonites and sandstones Minerolgical Magazine 49 393–400.CrossRefGoogle Scholar
Newmann, A.C.D. Brown, G., Newmann, A.C.D. and Brown, G., (1987) The chemical constitution of clays Chemistry of Clays and Clay Minerals London Mineralogical Society 1–128.Google Scholar
Passaglia, E. Artioli, G. Gualtieri, A. and Camevali, R., (1995) Diagenetic mordenite from Ponza, Italy European Journal of Mineralogy 7 429–438.CrossRefGoogle Scholar
Pearce, R.B. and Clayton, T., (1995) Tschermak substitution as an indicator of palaeotemperature in Silurian K-bentonites from the southern uplands of Scotland and northern Ireland Clay Minerals 30 15–25.CrossRefGoogle Scholar
Peccerillo, A. Conticelli, S. and Manetti, P., (1987) Petrological characteristics and the genesis of the recent magmatism of southern Tuscany and northern Latium Per Mineral 56 157–172.Google Scholar
Pichler, H., (1965) Acid hyaloclastites Bulletin of Volcanology 28 293–312.CrossRefGoogle Scholar
Poli, G., (1992) Geochemistry of Tuscan archipelago granitoids, central Italy: The role of hybridization processes in their genesis Journal of Geology 100 41–56.CrossRefGoogle Scholar
Pollard, C.O., (1971) Semidisplacive mechanism for diagenetic alteration of montmorillonite layers to illite layers Appendix: Geological Society of America Special Paper 134 79–93.Google Scholar
Pozzuoli, A. and Konta, J., (1988) Mineralogy, geochemistry, and origin of alteration products in the Pontian archipelago, Italy: I. The genesis of the Ponza bentonite Proceedings of the 10th Conference on Clay Mineralogy and Petrology Czechoslovakia Ostrava 89–98.Google Scholar
Pozzuoli, A., (1992) Genesis and time of formation of the Ponza island bentonite (Italy) Trends in Mineralogy 1 57–63.Google Scholar
Reynolds, R.C., Newmann, A.C.D. and Brown, G., (1980) Interstratified clay minerals Chemistry of Clays and Clay Minerals London Mineralogical Society 249–303.Google Scholar
Reynolds, R.C., (1985) NEWMOD-A computer program for the calculation of basal diffraction intensities of mixed-layered clay minerals, R.C. Reynolds, 8 Brook Road New Hampshire Hanover.Google Scholar
Reynolds, R.C., (1992) X-ray diffraction studies of illitesmectite from rocks, <1 μm randomly oriented powders, and <1 μm oriented powder aggregates: The absence of laboratory-induced artifacts Clays and Clay Minerals 40 387–396.CrossRefGoogle Scholar
Reynolds, R.C., Reynolds, R.C. and Walker, J.R., (1993) Three-dimensional X-ray powder diffraction from disordered illite: Simulations and interpretation of the diffraction patterns Computer Applications to X-ray Powder Diffraction Analysis of Clay Minerals Colorado Clay Minerals Society, Boulder 44–78.Google Scholar
Reynolds, R.C., (1993) WILDFIRE-A Computer Program for the Calculation of Three-Dimensional Powder X-ray Diffraction Patterns for Mica Polytypes and Their Disordered Variations, R.C. Reynolds, 8 Brook Road New Hampshire Hanover.Google Scholar
Reynolds, R.C. and Thomson, C.H., (1993) Illite from the Potsdam sandstone of New York: A probable noncentro- symmetric mica structure Clays and Clay Minerals 41 66–72.CrossRefGoogle Scholar
Rogers, N.W. Hawkesworth, C.J. Parker, R.J. and Marsh, J.S., (1985) The geochemistry of potassic lavas from Vulsini, central Italy and implications for mantle enrichment processes beneath the Roman region Contributions to Mineralogy and Petrology 90 244–257.CrossRefGoogle Scholar
Savelli, C., (1983) Eta’ K/Ar delle principali manifestazioni riolitiche dell’isola di Ponza Rendiconti della Societa Italiana 6 39–42.Google Scholar
Savelli, C., (1987) K/Ar ages and chemical data of volcanism in the western Pontine Islands (Tyrrhenian Sea) Bolletino della Societa Geologica Italiana 106 537–546.Google Scholar
Shiraki, R. Sakai, H. Endoh, M. and Kishima, N., (1987) Experimental studies on rhyolite- and andesite-seawater interactions at 300°C and 1000 bars Geochemical Journal 21 139–148.CrossRefGoogle Scholar
Small, J.S. Hamilton, D.L. and Habesch, S., (1992) Experimental simulation of clay precipitation within reservoir sandstones 1: Techniques and examples Journal of Sedimentary Petrology 62 508–519.CrossRefGoogle Scholar
Small, J.S. Hamilton, D.L. and Habesch, S., (1992) Experimental simulation of clay precipitation within reservoir sandstones 2: Mechanism of illite formation and controls on morphology Journal of Sedimentary Petrology 62 520–529.CrossRefGoogle Scholar
Smith, J.V. and Ribbe, P.H., (1966) X-ray emission microanalysis of rock-forming minerals III. Alkali feldspars Journal of Geology 74 197–216.CrossRefGoogle Scholar
Srodori, J. Eberl, D.D. and Bailey, S.W., (1984) Illite Micas Michigan Mineralogical Society of America, Chelsea 495–544.Google Scholar
Srodoh, J. Morgan, D.J. Eslinger, E.V. Eberl, D.D. and Karlinger, M.R., (1986) Chemistry of illite-smectite and endmember illite Clays and Clay Minerals 34 368–378.CrossRefGoogle Scholar
Srodon, J. Eisass, F. McHardy, W.J. and Morgan, D.J., (1992) Chemistry of illite-smectite inferred from TEM measurements of fundamental particles Clay Minerals 27 137–158.CrossRefGoogle Scholar
Sucha, V. Kraus, I. Mosser, C. Hroncova, Z. Soboleva, K.A. and Siranova, V., (1992) Mixed-layer illite-smectite from the Dolna Ves hydrothermal deposit, the western Carpathians Kremnica Mts Geologica Carpathia 1 13–19.Google Scholar
Taylor, H.P. and Turi, B., (1976) High lsO igneous rocks from the Tuscan magmatic province, Italy Contributions to Mineralogy and Petrology 55 33–54.CrossRefGoogle Scholar
Taylor, H.P. Gregory, R.T. Turi, B. and Helgeson, H.C., (1987) 18O/l6O evidence for fluid-rock interaction in the upper mantle: Data from ultramafic nodules and K-rich volcanic volcanic rocks in Italy Stable Isotopes at High Temperatures Michigan Mineralogical Society of America, Chelsea 1–37.Google Scholar
Tsipursky, S.I. and Drits, V.A., (1984) The distribution of octahedral cations in the 2:1 layers of dioctahedral smectites studied by oblique texture electron diffraction Clay Minerals 19 177–193.CrossRefGoogle Scholar
Turi, B. and Taylor, H.P., (1976) Oxygen isotope studies of potassic volcanic rocks of the Roman province, central Italy Contributions to Mineralogy and Petrology 55 1–31.CrossRefGoogle Scholar
Turi, B. Taylor, H.P. Ferrara, G., Taylor, H.P. O’Neil, J.R. and Kaplan, I.R., (1991) Comparisons of 18O/16O and 87Sr/86Sr in volcanic rocks from the Pontine Islands, M. Enrici, and Campania with other areas in Italy Stable Isotope Geochemistry: A Tribute to Samuel Epstein 307–324.Google Scholar
Velde, B., (1965) Experimental determination of muscovite polymorph stabilities American Mineralogist 50 436449.Google Scholar
Velde, B. and Hower, J., (1963) Petrological significance of illite polymorphism in Paleozoic sedimentary rocks American Mineralogist 48 1239–1254.Google Scholar
Warshaw, C.M., (1960) Experimental studies of illite Clays and Clay Minerals 5 303–316.Google Scholar
Whitney, G. and Northrop, H.R., (1988) Experimental investigation of the smectite to illite reaction: Dual reaction mechanisms and oxygen-isotope systematics American Mineralogist 73 77–90.Google Scholar
Whitney, G. and Velde, B., (1993) Changes in particle morphology during illitization: An experimental study Clays and Clay Minerals 41 209–218.CrossRefGoogle Scholar
Yamagishi, H. and Dimroth, E., (1985) A comparison of Miocene and Archean rhyolite hyaloclastites: Evidence for a hot and fluid rhyolite lava flow Journal of Volcanology and Geothermal Research 23 337–355.CrossRefGoogle Scholar
Yau, Y.-C. Peacor, D.R. and McDowell, S.D., (1987) Smectite-to-illite reactions in Salton Sea shales: A transmission and analytical electron microscopy study Journal of Sedimentary Petrology 57 335–342.Google Scholar
Ylagan, R.F., (1996) Mineralogy and geochemistry associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza island, Italy. Ph.D. thesis Illinois University of Illinois, Urbana.Google Scholar
Ylagan, R.F. Altaner, S.E. and Pozzuoli, A.P., (1996) Hydrothermal alteration of a rhyolitic hyaloclastite from Ponza island, Italy Journal of Volcanology and Geothermal Research 74 215–231.CrossRefGoogle Scholar
Zielinski, R.A., (1982) The mobility of uranium and other elements during alteration of rhyolite ash to montmorillonite: A case study in the Troublesome formation, Colorado, U.S.A Chemical Geology 35 185–204.CrossRefGoogle Scholar