A MOESSBAUER STUDY OF TWO AXINITES FROM POLAND

摘要

Two samples of ferroaxinites from Poland were analysed using Moessbauer spectroscopy. The spectrum of the sample from Pokrzywna was relatively simple, composed of one Fe~(2+) and one Fe~(3+) doublet, the latter from ferric iron compensating Al deficiency. The spectrum of the Strzegom axinite was more complex. Two Fe~(2+), one Fe~(3+), one Fe~(3+) and the Fe~(2.5+) mixed valence doublets have been distinguished in it. The Fe~(2+) doublets result probably from boron deficiency compensated by Si and Al, forming two different arrangements in the second coordination shell of Fe~(2+): with B~(3+), or with Si or Al if boron is absent. The Fe~(3+) doublet can be an effect of the Fe~(3+) + O~(2-) → Fe~(2+) + OH~- or (Al, Fe)~(3+) + (Al, Fe)~(3+) → Fe~(2+) + Si~(4+) substitutions, or the Al-Fe~(3+) disordering between the Al(1) or Al(2) and Fe sites. The Fe~(3+) doublet could be linked with the compensation of Si deficiency, apart from Al also by ferric iron. The Fe~(2.5+) mixed valence doublet is probably associated with electron delocalization between the Fe~(2+) (Fe site) and Fe~(3+) at the Al(1) site, but its abundance is comparable with analytical error, and the doublet is insignificant.