Weathering sequence of soils from volcanic ash involving allophane and halloysite, New Zealand

The clay minerals in a series of soils from rhyolitic ash having the same stratigraphy but different leaching environments were estimated quantitatively by oxalate dissolution, infrared spectroscopy, differential thermal analysis, electron microscopy and X-ray diffraction. Three soils were studied in detail. These were the Kereone soil (mean annual rainfall 1200 mm), the Ohaupo soil (1400 mm) and the Mairoa soil (2600 mm). The Kereone soil...