Scanning Electron Microscope Morphology of Deeply Weathered Granite

R. J. Gilkes, Anchalee Suddhiprakarn1 and T. M. Armitage
Department of Soil Science and Plant Nutrition, University of Western Australia Nedlands, Western Australia, 6009
1 Permanent address: Department of Soils, Kasetsart University, Bangkok, Thailand.

Abstract: Laterite profiles developed from granite in southwestern Australia were studied by scanning electron microscopy. The morphology of soil materials reflects the mineralogy of secondary minerals formed from feldspar. In the saprolite, etched feldspar surfaces are coated with kaolinite or radiating, spherical aggregates of tubular halloysite. In the lower pallid zone these minerals have replaced most of the feldspar. In the upper pallid zone a porous framework has developed consisting mainly of quartz and gibbsite with 5-µm euhedral gibbsite crystals in voids. Halloysite crystals in the upper pallid zone are partly unrolled and have splayed ends. Differences in mineralogy and morphology between profiles are thought to be due to variations in the intensity of leaching.

Key Words: Feldspar • Gibbsite • Granite • Halloysite • Kaolinite • Scanning electron microscopy • Weathering

Clays and Clay Minerals; February 1980 v. 28; no. 1; p. 29-34; DOI: 10.1346/CCMN.1980.0280104
© 1980, The Clay Minerals Society
Clay Minerals Society (www.clays.org)