Mössbauer investigation of niningerite solid solutions (Mg,Fe)S |
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| Authors: | Margery D Osborne Michael E Fleet |
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| Institution: | 1. Department of Geology, University of Western Ontario, N6A 5B7, London, Ontario, Canada
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| Abstract: | 57Fe Mössbauer spectra of (Mg,Fe)S solid solutions (niningerite) quenched from 1,000° C exhibit a singlet only within the composition range 8.4 to 50.0 mol. percent FeS. The isomer shift decreases progressively with increasing FeS content (from 0.99 to 0.95 mm/s) and extrapolates to a value of about 0.9 mm/s for FeS (halite structure), in close agreement with the isomer shift for FeS (troilite). Line width increases progressively with increasing FeS content (from 0.32 to 0.47 mm/s) and with decreasing temperature. The broadened singlet spectrum is interpreted as an unresolved composite quadrupole split doublet, which is attributed to local site distortion by next-nearest neighbor cation substitution. The ground state splitting is estimated to be 40 cm?1 in (Mg0.5Fe0.5)S. The next-nearest neighbor effect in niningerite is anomalously small compared to that observed in spinel and (Mg,Fe)O compositions. |
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