EVIDENCE FOR THE FE(II)-FE(III) GREEN RUST FOUGERITE MINERAL OCCURRENCE IN A HYDROMORPHIC SOIL AND ITS TRANSFORMATION WITH DEPTH

Mossbauer spectroscopy is used to characterize a Green Rust as a natur al mineral for the first time. Samples are taken from a hydromorphic s oil under the forest at Fougeres (Brittany, France) during spring seas on. Spectra are compared with those of synthetic Green Rusts (GRs), i. e. hydroxy-chloride, -sulphate, -carbonate and display one ferric and one or two ferrous sites. Fe(II)/Fe(III) abundances ratio cannot be at tributed definitely to one of those stoichiometric compounds. Therefor e, the counter-anion species cannot be specified even though hyperfine parameters perfectly match values of synthetic samples. The Fe(II)/Fe (III) ratio obtained from the Mossbauer spectra decreases with samplin g depth. The ''fougerite(dagger)'' originates likely from the reductio n of deeper Fe(In)-mineral species by anoxic waterlogging.