Heavy mineral weathering under acidic soil conditions

The weathering of heavy minerals in acid soil profiles (pH 4-5) has been studied in terms of their relative mineral proportions and by using the surface etching features of apatite and hornblende grains. An increasing stability order of: apatite, titanite, hornblende, garnet, epidote, zircon is found in the 45-63 mu m coarse-silt fraction of soils developed on tills in southwestern Sweden. In glaciofluvial deposits, sorting processes during deposition have largely determined the variations in heavy mineral content of soils, and only the dissolution of apatite is significant. Hornblende etching is more extensive in soils with low hornblende content, indicating that the release of cations relative to the amount of hornblende is greater in such soils. (C) 2000 Elsevier Science Ltd. All rights reserved.