T9.4 : Soil studies and climatic implications
While most igneous rocks show a notable isotopic homogeneity, early works on soils from temperate areas have in contrast uncovered significant iron isotope fractionations (Fantle and DePaolo, 2004; Emmanuel et al., 2005; Wiederhold et al., 2007), probably related to partial changes in the oxidation state of the iron stocks involved. However, tropical lateritic soils, which are among the thickest and that integrate the longest history, show almost no isotopic fractionation (Poitrasson et al., 2008)! This likely results from a nearly quantitative oxidation of the iron from the parent rock, without subsequent change. This contrast in the isotopic fractionation of iron from soils depending on the climatic context may lead to possible uses of the isotopic composition of this element for the study of climate change. This new research avenue, also highlighted by others (Ingri et al., 2006, Thompson et al., 2007), is being explored in our group in Cameroon, Brazil and Russia through the study of soils and rivers.