The role of iron in the weathering of a climosequence of soils derived from schist

Mossbauer spectra were obtained of the whole soil and clay fractions and some of the sand fractions, as well as some rock samples that were taken from eight soils forming a climosequence on schist in South Island, New Zealand. They show that the main changes in iron across the sequence involve the oxidation of ferrous ions in muscovite mica and its initial weathering products to ferric ions in these minerals and also in oxyhydroxides. The extremes of weathering in the sequence led to the mobilization of iron from primary minerals in soils at the surface of profiles into oxyhydroxides that were deposited lower down in these profiles. While these changes in iron have occurred alongside the loss of K+ from the interlayers of the micas to form expanded phases, there is not a close parallel between the changes on oxidation and those from the initial loss of interlayer potassium.