Abstract
Biotite in deeply weathered granitic rocks in southwestern Australia has altered to exfoliated grains composed of biotite, mixed-layer clay minerals, kaolinite, vermiculite, gibbsite, goethite, and hematite. Discrete vermiculite and vermiculite-dominant mixed-layer clay minerals are not major weathering products. Oxidation of octahedral iron in biotite is associated with ejection of octahedral cations, loss of interlayer K, and a contraction of the b-dimension of the biotite sheet. Si, Mg, Ca, Mn, K, and Na are lost from biotite during weathering, and Ti, Al, Ni, and Cr are retained. Fe and water have been added to the grains during weathering. Much Fe occurs as aggregates of microcystalline, aluminum-rich goethite particles on flake surfaces and within etchpits, with smaller amounts occurring as hexagonal arrangements of lath-shaped crystals of goethite on flake surfaces.
Резюме
Биотит в глубоко выветренных гранитных породах в юго-западной Австралии был изменен в расслоенные зерна, состоящие из биотита, смешанно-слойных минералов, каолинита, вермикулита, гиббсита, гетита, и гематита. Дискретный вермикулит и смешанно-слойные глинистые минералы, в основном содержащие вермикулит, не являются основными продуктами выветривания. Окисление октаэдрического железа в биотите ассоциируется с выбросом октаедри-ческих катионов, потерей межслойного К, и сокращением Ь-измерения пластин биотита. Si, Мg, Са, Мп, К, и Nа высвобождается из биотита во время выветривания, а Тi, Аl, Ni, и Сг остаются. Во время выветривания в зернах появляется добавочная вода и Ре. Много Ре встречается в виде агрегатов микрокристаллических богатых алюминием гетитовых частиц на чешуйчатых поверхностях, меньшие количества встречаются в виде гексагонально расположенных пластинчатых кристаллов гетита на чешуйчатых поверхностях.
Resümee
Der Biotit in den tiefgründig verwitterten, granitischen Gesteinen von Südwest-Australien ist in schuppige Körner umgewandelt, die aus Biotit, Wechsellagerungen, Kaolinit, Vermiculit, Gibbsit, Goethit, und Hämatit bestehen. Einzelne, diskrete Vermiculite und vorwiegend aus Vermiculit bestehende Wechsellagerungen kommen dagegen nicht oft als Verwitterungsprodukte vor. Die Oxidation des okta-edrischen Eisens im Biotit ist mit dem Austritt von oktaedrischen Kationen, dem Verlust von Kalium aus den Zwischenschichten und einer Verkleinerung der Biotitschicht in Richtung der b-Achse verbunden. Während der Verwitterung verarmt der Biotit an Si, Mg, Ca, Mn, K, und Na, während Ti, Al, Ni, und Cr zurückgehalten werden. Fe und Wasser werden den Körnern während der Verwitterung zugeführt. Ein großer Teil des Fe ist in Form von Aggregaten aus mikrokristallinen, aluminiumreichen Goethitpartikeln auf den Blättchenoberflächen und in Atzgruben vorhanden. Ein kleiner Teil kommt in Form von hexagon-alen Anordnungen aus leistenförmigen Goethitkristallen auf den Blättchenoberflächen vor.
Résumé
La biotite dans des roches granitiques profondément altérées d’Australie du Sud-ouest a été altérée en grains exfoliés composés de biotite, de minéraux argileux à couches mélangées, de kaolinite, de vermiculite, de gibbsite, de goethite, et d’hématite. La vermiculite elle-même, et les minéraux argileux à couches mélangées à prédominance de vermiculite ne sont pas des produits d’altération majeurs. L’oxidation de fer octaédrique dans la biotite est associée avec l’éjection de cations octaédriques, avec la perte de l’intercouche K, et avec la contraction de la dimension-b de la feuille de biotite. Si, Mg, Ca, Mn, K, et Na sont perdus par la biotite pendant l’altération, et Ti, Al, Ni, and Cr sont retenus. Fe et de l’eau ont été ajoutés aux grains pendant l’altération. Beaucoup de Fe existe comme aggrégats de particules de goethite microcristallins et riches en aluminium sur des surfaces de lame et dans des crevasses gravées, avec des quantités moindres existant comme arrangements hexagonaux de cristaux de goethite en forme de latte sur les surfaces des lames.
Similar content being viewed by others
References
Brindley, G. W. and MacEwan, D. M. C. (1953) Structural aspects of the mineralogy of clays: in Ceramics—a symposium, British Ceramic Society, Stoke-on-Trent, 15–69.
Eswaran, H. and Bin, W. C. (1978) A study of adeep weathering profile on granite in Peninsular Malaysia: III. Alteration of feldspars: Soil Sci. Soc. Am. J. 42, 154–158.
Eswaran, H. and Heng, Y. Y. (1976) The weathering of Morite in a profile on gneiss in Malaysia: Geoderma 16, 9–20.
Fanning, D. S. and Keramidas, V. Z. (1977) Micas: in Minerals in Soil Environments, J. B. Dixon and S. B. Weed, eds., Soil Science Society of America, Madison, Wisconsin, 195–258.
Farmer, V. C., Russell, J. D., McHardy, W. J., Newman, A. C. D., Alhrichs, J. L., and Rimsaite, J. Y. H. (1971) Evidence for loss of protons and octahedral iron from oxidized biotites and vermiculites: Mineral. Mag. 38, 121–137.
Gandolfi, G. (1967) Discussion upon methods to obtain X-ray powder patterns from a single crystal: Mineral. Petrogr. Acta 13, 67–74.
Gilkes, R. J. (1973) The alteration products of potassium-depleted oxybiotite: Clays & Clay Minerals 21, 303–313.
Gilkes, R. J. and Suddhiprakarn, A. (1979) Biotite alteration in deeply weathered granite II. The oriented growth of secondary minerals: Clays & Clay Minerals 27, 361–367.
Gilkes, R. J., Young, R. C., and Quirk, J. P. (1972) The oxidation of octahedral iron in biotite: Clays & Clay Minerals 20, 303–315.
Jackson, M. L., Lee, S. Y., Brown, J. L., Sachs, I. B., and Syers, J. K. (1973) Scanning electron microscopy of hydrous metal oxide crusts intercalated in naturally weathered micaceous vermiculite: Soil Sci. Soc. Amer. Proc. 37, 127— 131.
Kato, Y. (1965) Mineralogical study of weathering products of granodiorite at Shinshiro City: Weathering of primary minerals, mineralogical characteristics of weathered mineral grains: Soil Sci. Plant Nutr. (Tokyo) 11, 30–40.
Klug, H. P. and Alexander, L. E. (1974) X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials: Wiley, New York, 966 pp.
Leonard, R. A. and Weed, S. B. (1970) Effects of potassium removal on the b-dimension of phlogopite: Clays & Clay Minerals 18, 197–202.
Mitchell, R. L. (1964) Trace elements in soils: in Chemistry of the Soil, F. E. Bear, ed., Reinhold, New York, 320–366.
Norrish, K. (1973) Factors in the weathering of mica to vermiculite: Proc. 1972 Int. Clay Minerals Conf., Madrid, 417–432.
Norrish, K. and Hutton, J. T. (1969) An accurate X-ray spec-trographic method for the analysis of a wide range of geological samples: Geochim. Cosmochim. Acta 33, 431–453.
Norrish, K. and Taylor, R. M. (1961) The ismorphous replacement of iron by aluminium in soil goethite: J. Soil Sci. 12, 294–306.
Radoslovich, E. W. (1963) Cell dimension studies on layer lattice silicates: A summary: Clays & Clay Minerals 11, 225–228.
Radoslovich, E. W. (1975) Micas in macroscopic forms: in Soil Components: Vol. 2—Inorganic Components, J. E. Gieseking, ed., Springer Verlag, New York, 27–57.
Reichenbach, H. Graf von and Rich, C. I. (1975) Fine-grained micas in soils: in Soil Components: Vol. 2—Inorganic Components, J. E. Gieseking, ed., Springer Verlag, New York, 59–95.
Rhoades, J. D. and Coleman, N. T. (1967) Interstratification in vermiculite and biotite produced by potassium sorption. I. Evaluation by simple X-ray diffraction pattern inspection: Soil Sci. Soc. Amer. Proc. 31, 366–372.
Ruiz-Amil, A., Garcia, A. R., and MacEwan, D. M. C. (1967) X-ray Diffraction Curves for the Analysis of Inter-stratified Structures: Volturna Press, Edinburgh.
Sadleir, S. B. and Gilkes, R.J. (1976) Development of bauxite in relation to parent material near Jarrahdale, Western Australia: J. Geol. Soc. Aust. 23, 333–344.
Sawhney, B. L. (1967) Interstratification in vermiculite: Clays & Clay Minerals 15, 75–84.
Schwertmann, U. and Taylor, R. M. (1977) Iron oxides: in Minerals in Soil Environments, J. B. Dixon and S. B. Weed, eds., Soil Science Society of America, Madison, Wisconsin, 145–176.
Suito, E. and Nakahira, M. (1971) Micas and related minerals: in The Electron-Optical Investigation of Clays, J. A. Gard, ed., Mineralogical Society, London, 231–255.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gilkes, R.J., Suddhiprakarn, A. Biotite Alteration in Deeply Weathered Granite. I. Morphological, Mineralogical, and Chemical Properties. Clays Clay Miner. 27, 349–360 (1979). https://doi.org/10.1346/CCMN.1979.0270505
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1346/CCMN.1979.0270505