MOSSBAUER-SPECTROSCOPY OF MINERALS .3. OCTAHEDRAL-SITE FE2-ANNITE SERIES( QUADRUPOLE SPLITTING DISTRIBUTIONS IN THE PHLOGOPITE)

We develop the methodology of quadrupole splitting distribution (QSD) analysis by evaluating the influences of absorber thickness, absorber texture, and the assumed Lorentzian width on the extracted QSD. We the n present the first study to describe the Mossbauer spectra of members of a mineral family in terms of QSDs. The Fe2+ QSD and its characteri stics (average QS, peak QS, skewness, and standard deviation) show gra dual trends with changing Fe/(Fe + Mg) in a synthetic Al-deficient phl ogopite-annite series. Al-deficient natural samples of phlogopite and annite show similar behaviour. The Fe2+ QSDs can be interpreted as pop ulation distributions of local distortion environments (LDEs) and, as such, contain much information that will become more accessible as the oretical calculations linking particular LDEs to corresponding QS valu es are developed.