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Weathering of Basalt: Changes in Rock Chemistry and Mineralogy

Published online by Cambridge University Press:  02 April 2024

Richard A. Eggleton
Affiliation:
Department of Geology, Australian National University, Canberra, ACT 2601 Australia
Chris Foudoulis
Affiliation:
Department of Geology, Australian National University, Canberra, ACT 2601 Australia
Dane Varkevisser
Affiliation:
Department of Geology, Australian National University, Canberra, ACT 2601 Australia

Abstract

The weathering of eastern Australian basalts, sampled from the rounded, hard, core-stone to the rind of softer weathered material, has been examined by bulk chemical analyses, thin section petrography, electron microprobe, and X-ray powder diffraction analyses. Using density as a measure of weathering intensity, data from four core-stones show that at a stage of weathering in which the total loss due to dissolution is – (i.e., at the core-stone rim), the percentages lost of the following major elements are: Ca, 85; Mg, 80; Na, 70; K, 50–80; P, 55; Si, 45; Mn, 40; Al, 5; Fe, 0; and Ti, 0. With more intense weathering, deposition of some elements, particularly rare earths and Ba, and mobilization and deposition of Al and Fe make quantification impossible. The rate of weathering of individual minerals is consistent with the well-known susceptibility series: glass ∼ olivine > plagioclase > pyroxene > opaque minerals. Clay minerals in the core-stones are dominated by smectites, whereas those in the surrounding more intensely weathered rinds are dominated by halloysite and goethite.

Type
Research Article
Copyright
Copyright © 1987, The Clay Minerals Society

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References

Banfield, J. F., 1985 Mineralogy and chemistry of granite weathering Australia Australian National University, Canberra.Google Scholar
Claridge, G. G. C. and Campbell, I. B., 1984 Mineral transformation during the weathering of dolerite under cold arid conditions in Antarctica New Zealand J. Geophys. 27 537546.CrossRefGoogle Scholar
Colman, S. M. (1982) Chemical weathering of basalts and andesites: Evidence from weathering rinds: U.S. Geol. Sun. Prof. Pap. 1246, 51 pp.Google Scholar
Craig, D. C. and Loughnan, F. C., 1964 Chemical and mineralogical transformations accompanying the weathering of basic volcanic rocks from New South Wales Australian J. Soil Res. 2 218234.CrossRefGoogle Scholar
Henderson, P., 1982 Inorganic Geochemistry New York Pergamon Press.Google Scholar
Hendricks, D. M. and Whittig, L. D., 1968 Andesite weathering, Part II. Geochemical changes from andesite to saprolite Soil Sci. 19 147153.CrossRefGoogle Scholar
Jones, J. G. and Veevers, J. J., 1982 A Cainozoic history of Australia’s Southeast Highlands Geol. Soc. Aust. 29 114.Google Scholar
Kesson, S. E., 1973 The primary geochemistry of the Monaro alkaline volcanics, southeastern Australia—Evidence for upper mantle heterogeneity Contr. Mineral. Petrol. 42 93108.CrossRefGoogle Scholar
Loughnan, F. C., 1969 Chemical Weathering of the Silicate Minerals New York Elsevier.Google Scholar
Norrish, K. and Holmes, J. W., 1968 Some phosphate minerals in soils Trans. 9th Conf. Int. Soil Sci. Soc., Adelaide, Vol. 2 Australia Angus and Robertson, Sydney.Google Scholar
Norrish, K., Chappell, B. W. and Zussman, J., 1977 X-ray fluorescence spectrography Physical Methods in Determinative Mineralogy New York Academic Press.Google Scholar
Wilson, R. E., 1978 Mineralogy, petrology and geochemistry of basalt weathering .Google Scholar