The formation of maghemite and hematite from lepidocrocite and goethite in a Cambisol from Corsica,France

The influence of a recent forest fire on the iron oxide phases, present in the A and the B horizon of a brown earth from Corsica, was examined by X-ray diffraction and chemical analysis. In the B horizon goethite and lepidocrocite, in the A horizon maghemite and hematite were identified. From the Al/(Al+Fe) ratio, which was determined for all four minerals by XRD, it was concluded that goethite was the precursor of hematite and lepidocrocite the precursor of maghemite respectively. The proportion of maghemite formed in the A horizon was calculated from the difference in Fe_d between the untreated sample and that free of maghemite. Because of substantial dissolution of clay minerals even after 5 citrate-bicarbonate treatments, it was not possible to determine Al_d correctly.