FE-57 MOSSBAUER SPECTROSCOPIC CHARACTERIZATION OF A FERROMANGANESE NODULE FROM THE CENTRAL INDIAN-OCEAN

The iron bearing phases present in a ferromanganese nodule from the Ce ntral Indian Ocean have been determined using Fe-57 Mossbauer spectros copy. The Mossbauer results have been corroborated by XRD, IR and TG-D TA studies. The Mossbauer spectrum of a ferromanganese nodule shows a broad line width which indicates the presence of more than one iron be aring paramagnetic oxide or oxyhydroxide phases where iron is present as Fe3+. gamma-FeOOH has been distinctly characterised as one of the i ron bearing phases in the nodule. Other oxyhydroxide and oxide phases of iron in the nodule have been ruled out. A typical paramagnetic doub let persists even at very high temperature which has been proposed to be due to iron(III)phosphate. Formation of solid solution of Mn2O3-Fe2 O3 has been observed in the heat treated nodule at 1073 K, which has b een characterised by the Mossbauer technique.