A MOSSBAUER-EFFECT INVESTIGATION OF CORRELATED HYPERFINE PARAMETERS IN NATURAL GLASSES (TEKTITES)

Room temperature Fe-57 Mossbauer effect spectroscopy has been used to investigate the Fe quadrupole splitting distribution in tektites from strewn fields in the Czech Republic (Moldavite), Australasia (Rizalite ) and North America (Bediasite). In all cases the Mossbauer effect spe ctra show a broadened, slightly asymmetric quadrupole split doublet. T wo quadrupole distributions, corresponding to Fe2+ and Fe3+ sites, hav e been used tb-fit the resulting spectra. The Fe2+ distribution shows two components corresponding to Fe with octahedral coordination and Fe with tetrahedral coordination. The Fe3+ distribution shows a single c omponent centered near zero splitting. Fe3+/Fe2+ ratios and Fe2+ tetra hedral/octahedral ratios have been determined from the relative areas of the various spectral components. Variations in the hyperfine parame ters between samples from different strewn fields seem to be more sign ificant than variations within a strewn field. Fitted parameters may b e correlated with mean quadrupole splitting values and are discussed i n terms of possible differences in tektite formation conditions. (C) 1 998 Elsevier Science B.V.