| Research Abstract |
The oxidation and dehydrogenation processes for amphibole-group minerals were investigated using the Mossbauer, infrared and XRD methods.The series of amphiboles studied were : (1) Fe-Mg-Mn amphiboles of holmquistite, anthophyllite, cummingtonite-grunerite, tirodite-dannemorite, (2) Ca-amphiboles of tremolite-ferroactinolite, hornblende-ferropargasite, (3) Na-Ca amphiboles of manganoan richterite, and (4) alkali amphiboles of magnesioarfvedsonite and the glaucophane-riebeckite series. Although there are many series in the amphibole-group minerals, the oxidation and dehydrogenation processes occur in similar ways :
(1) At temperatures ranging from 350ﾟC to 650ﾟC,Fe^<2+> ion in the M1 and M3 sites are oxidized, yielding Fe^<3+> one electron. A proton from the (OH)^- is liberated, and combines with the electron, forming a hydrogen atom.
(2) In Fe^<2+>-poor amphiboles, some Fe^<2+> ions in the M2 and M4 sites migrate to the M1 and M3 sites, and then are oxidized in a similar way. Residing Fe^<2+> in the M2 and M4 sites are also oxidized by the breaking of the (Mg・Mg・Mg/Fe^<3+>)-(OH)to(Mg・Mg・Mg/Fe^<3+>)-0, liberating an electron or decomposing the amphibole structure.
(3) When some Fe^<2+> still remain (in the case of ferro-actinolite), this iron is oxidized by the breaking down of the amphibole structure at higher temperatures, leaving oxide minerals and quartz.
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