Oxidation state and distribution of Fe in pumpellyite from northen part of Chichibu zone, Ehime Prefecture, Japan

Abstract

Oxidation state and distribution of Fe among the octahedral X and Y sites in pumpellyite from green rocks in the north part of the Chichibu zone, Ehime Prefecture, Japan, were investigated. By applying the Fe²⁺:Fe³⁺-ratio determined by Mössbauer analysis, Fe(X) and Fe(Y) occupancies refined by Rietveld method together with chemical composition, the chemical formulae of pumpellyites with 10.01 and 16.04 wt% average total Fe₂O₃ were constructed as (Ca7.96Na0.01K0.02)Σ7.99(Al1.62Mg1.19Fe³⁺0.57Fe²⁺0.53Mn0.09)Σ4.00(Al6.47Fe³⁺1.53V0.02Ti0.01)Σ8.03Si12.25O40.75(OH)15.25 and (Ca8.07K0.01)Σ8.08(Al1.21Mg0.96Fe³⁺1.00Fe²⁺0.83Mn0.02)Σ4.02(Al5.69Fe³⁺2.33V0.01)Σ8.03Si12.02O47.40(OH)8.60. The K_D-values ([Fe³⁺/Al]^X/[Fe³⁺/Al]^Y) were 1.49 for the former, and 2.02 for the latter.