Reductive dissolution and Mossbauer spectroscopic study of Fe forms in thefine fractions of Slovak Fe-rich bentonites

Four samples of <2 mu m fractions of Fe-rich bentonites from the area of th e Zvolenska kotlina Basin (Slovakia) have been investigated by Mossbauer sp ectroscopy and reductive dissolution in ammonium hydrogen oxalate (pH = 2.7 ). Both methods have shown the presence of goethite in the samples. The rel ative amount of Fe bound in goethite varied more within the samples of bent onite from Zvolenska Slatina, which was redeposited after transport over a short distance, than in the authigenically altered bentonite from Hrochot'. The results of the fits of the reductive dissolution curves suggest size d istribution, variation in Al-for-Fe substitution in goethite particles and/ or different access of extracting solution to goethite particles present in the analysed fine fractions of bentonites.