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Feldspar Weathering in Lateritic Saprolite

Published online by Cambridge University Press:  02 April 2024

R. R. Anand ,
R. J. Gilkes ,
T. M. Armitage  and
J. W. Hillyer
R. R. Anand
Affiliation:
Department of Soil Science and Plant Nutrition, University of Western Australia, Nedlands, Western Australia 6009, Australia
R. J. Gilkes
Affiliation:
Department of Soil Science and Plant Nutrition, University of Western Australia, Nedlands, Western Australia 6009, Australia
T. M. Armitage
Affiliation:
Department of Soil Science and Plant Nutrition, University of Western Australia, Nedlands, Western Australia 6009, Australia
J. W. Hillyer
Affiliation:
Electron Microscopy Center, University of Western Australia, Nedlands, Western Australia 6009, Australia
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Abstract

Feldspars in granitic saprolite in southwestern Australia have altered to halloysite, kaolinite, and gibbsite with no evidence of noncrystalline material. The secondary minerals are commonly present as intimate mixtures within altered feldspar grains, but discrete zones of gibbsite or halloysite-kaolinite also are present. Variations in the chemical microenvironment within micrometer-size zones in grains apparently controlled the type and distribution of secondary minerals. The alteration of both plagioclase and alkali feldspars involved congruent dissolution by soil solution and crystallization of halloysite, kaolinite, and gibbsite from this solution. Highly altered feldspar grains consist of etched feldspar fragments embedded within a highly porous framework of subhedral to euhedral platy crystals of kaolinite and gibbsite, or of spherical and felted aggregates of halloysite.

Резюме

Резюме

Фельдшпаты в гранитовом сапролите в юго-западной Австралии изменялись в галлуазит, каолинит и гиббсит, без доказательства присутствия некристаллических материалов. Вторичные минералы находятся обычно как внутренные смеси в зернах фельдшпата, но дискретные зоны гиббсита или галлуазита-каолинита также присутствуют. Перемены в химическом микроокружении внутри микроскопических зон в зернах, кажется, контролируют тип и расположение вторичных минералов. Видоизменение обоих плагиоклаза и щелочных фельдшпатов включало соответственно растворение в почвенном растворе и кристаллизацию галлуазита, каолинита, и гиббеита из этого раствора. Значительно видоизмененные зерна фельдшпата состоят из изъеденных фрагментов фельдшпата, окруженных сильно пороватой сетью субгедральных до евгедральных плоских кристаллов каолинита и гиббеита, либо сферических и войлочных аггрегатов галлуазита. [E.G.]

Resümee

Resümee

Die Feldspäte in einem granitischen Rückstandsgestein von SW-Australien haben sich in Halloysit, Kaolinit, und Gibbsit umgewandelt, wobei es keinen Hinweis für nichtkristallisierte Substanzen gibt. Die sekundären Minerale treten meist eng vermischt in umgewandelten Feldspatkörnern auf. Es gibt jedoch auch begrenzte Zonen, in denen Gibbsit oder Halloysit-Kaolinit getrennt auftreten. Variationen im chemischen Mikrobereich innerhalb von Mikrometer-großen Zonen in den Körnern kontrollieren offensichtlich die Art und Verteilung der Sekundärminerale. Die Umwandlung von Plagioklas und Alkalifeldspat umfaßt konkruente Auflösung durch Bodenlösung und die Kristallisation von Halloysit, Kaolinit und Gibbsit aus dieser Lösung. Stark umgewandelte Feldspatkörner bestehen aus angelösten Feldspatfragmenten, die in einem stark porösen Gerüst aus hypidiomorphen bis idiomorphen tafeligen Kristallen von Kaolinit und Gibbsit liegen oder in einem Gerüst aus kugeligen und dichten Aggregaten von Halloysit eingebettet sind. [U.W.]

Résumé

Résumé

Des feldspars dans de la saprolite granitique en Australie du sud-ouest se sont altérés en halloysite, kaolinite et gibbsite, sans évidence de matériel non-cristallin. Les minéraux secondaires sont communément présents en tant que mélanges intimes au sein de grains de feldspar altéres, mais des zones discrètes de gibbsite ou d'halloysite-kaolinite sont également présentes. Des variations dans le microen-vironement chimique au sein de zones de taille micrométrique dans les grains ont apparemment contrôlé le type et la distribution de minéraux secondaires. L'altération à la fois de plagioclase et de feldspars alkalins a impliqué la dissolution congruente de solution de sol et la cristallisation d'halloysite, de kaolinite et de gibbsite à partir de cette solution. Les grains de feldspar fort altérés consistent en des fragments gravés de feldspar enfoncés au sein d'une matrice très poreuse de cristaux sousédraux à euédraux de kaolinite et de gibbsite, ou d'aggrégats sphériques et feutrés d'halloysite. [D.J.]

Keywords

FeldsparGibbsiteHalloysiteKaoliniteNoncrystalline materialWeathering
Type
Research Article
Information
Clays and Clay Minerals , Volume 33 , Issue 1 , February 1985 , pp. 31 - 43
Copyright
Copyright © 1985, The Clay Minerals Society

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References

Agar, A.W. and Kay, D., 1967 Operation of the electronmicroscope Techniques for Electron Microscopy Oxford Blackwell Scientific Publications 1–43.Google Scholar
Berner, R. A., Holdren, G. R. Jr., 1977 Mechanism of feldspar weathering. I. Some observational evidence Geology 5 369–372.2.0.CO;2>CrossRefGoogle Scholar
Berner, R. A., Holdren, G. R. Jr., 1979 Mechanism of feldspar weathering. II. Observations of feldspars from soils Geochim. Cosmochim. Acta 43 1173–1186.CrossRefGoogle Scholar
Diamond, S. and Bloor, J. W., 1970 Globular cluster microstructure and endellite (hydrated halloysite) from Bedford, Indiana Clays & Clay Minerals 18 309–312.CrossRefGoogle Scholar
Eggleton, R. A. and Buseck, P. R., 1980 High resolution electron microscopy of feldspar weathering Clays & Clay Minerals 28 173–178.CrossRefGoogle Scholar
Eswaran, H. and Bin, W. C., 1978 A study of a deep weathering profile on granite in Peninsular Malaysia. III. Alteration of feldspars Soil Sci. Soc. Amer. J 42 154–158.CrossRefGoogle Scholar
Eswaran, H., Stoops, G. and Sys, C., 1977 The micro-morphology of gibbsite forms in soils J. Soil Sci 28 136–143.CrossRefGoogle Scholar
Exley, C.S., 1976 Observations on the formation of kaolinite in the St. Austell granite, Cornwall Clay Miner 11 51–63.CrossRefGoogle Scholar
Gandolfi, G., 1967 Discussion upon methods to obtain X-ray powder patterns from a single crystal Min. Petrogr. Acta 13 67–74.Google Scholar
Garrels, R. M. and Christ, L. L., 1965 Solutions, Minerals and Equilibria New York Harper and Row.Google Scholar
Gilkes, R. J., Scholz, G. and Dimmock, G. M., 1973 Lateritic deep weathering of granite J. Soil Sci 24 523–536.CrossRefGoogle Scholar
Gilkes, R. J. and Suddhiprakarn, A., 1980 Scanning electron microscope morphology of deeply weathered granite Clays & Clay Minerals 28 29–34.CrossRefGoogle Scholar
Honjo, G., Kitamura, N. and Mihama, K., 1954 Study of clay minerals by single crystal electron diffraction diagrams—the structure of tubular kaolin Clay Min. Bull 2 131–141.CrossRefGoogle Scholar
Hughes, J. C. and Brown, J., 1977 Two unusual minerals in a Nigerian soil. (1) Fibrous kaolin. (2) Bastnaesite Clay Miner 12 319–329.CrossRefGoogle Scholar
Keller, W. D., 1978 Kaolinization of feldspar as displayed in scanning electron micrographs Geology 6 184–188.2.0.CO;2>CrossRefGoogle Scholar
Lodding, W., 1972 Conditions for the direct formation of gibbsite from K-feldspar—discussion Amer. Mineral 57 292–294.Google Scholar
Lunderstrom, I., 1970 Etch pattern and albite twinning in two plagioclases Ark. Mineral. Geol 5 63–91.Google Scholar
Parham, W.E., 1969 Formation of halloysite from feldspar: low temperature artificial weathering versus natural weathering Clays & Clay Minerals 17 13–22.CrossRefGoogle Scholar
Peck, A. J., Williamson, D. R., Hurle, D. H., Yendle, P. A. and Trotter, C., 1982 Groundwater observations in the Darling Range, Western Australia CSIRO Div. Land Resources Management Tech. Memo 1–7.Google Scholar
Rich, C. I., 1972 Potassium in soil minerals Potassium in Soil 15–31.Google Scholar
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.CrossRefGoogle Scholar
Tardy, Y., Bocquier, G., Paquet, H. and Millot, G., 1973 Formation of clay from granite and its distribution in relation to climate and topography Geoderma 10 271–284.CrossRefGoogle Scholar
Tazaki, K., 1976 Scanning electron microscopic study of formation of gibbsite from plagioclase Paper Inst, for Thermal Spring Research 11–24.Google Scholar
Wilke, B. S., Schwertmann, U. and Murad, E., 1978 An occurrence of polymorphic halloysite in granite saprolite of the Bayerischer Wald, Germany Clay Miner 13 67–77.CrossRefGoogle Scholar
Wilson, M.J., 1975 Chemical weathering of some primary rock-forming minerals Soil Sci 119 349–355.CrossRefGoogle Scholar
Wilson, M. J., Bain, D. C. and McHardy, W. J., 1971 Clay mineral formation in a deeply weathered boulder conglomerate in North-East Scotland Clays & Clay Minerals 19 345–352.CrossRefGoogle Scholar
Wilson, M. J. and McHardy, W. J., 1980 Experimental etching of a microcline perthite and implications regarding natural weathering J. Microscopy 120 291–302.CrossRefGoogle Scholar