LATERITIC DEEP WEATHERING OF GRANITE |
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| Authors: | R J GILKES G SCHOLZ G M DIMMOCK† |
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| Institution: | Department of Soil Science and Plant Nutrition, Institute of Agriculture, University of Western Australia, Nedlands, W.A., 6009;Division of Soils, CSIRO, Rural Sciences Laboratory, Floreat Park, W.A., 6014 |
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| Abstract: | Chemical and mineralogical analyses of two representative laterite profiles developed from granite in south-western Australia have shown that several depth zones defined by particular mineral suites and geochemistry may be recognized. These zones are not simply related to the conventional morphological pallid, mottled, and ferruginous zones. Changes in geochemistry in both profiles can be related to the stability of the major mineral species and to the common isomorphous substitutions occurring in them. Ca, Na, and Mg, which are mainly present in plagioclase feldspars and ferromagnesian minerals, are removed during the earliest stage of alteration of the parent granite. K, Mn, Zn, and residual Ca, Na, Mg, and Sr decrease as microcline and micas alter to kaolin. Al and Fe are most abundant in the surface zones which contain secondary sesquioxide minerals. |
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