Effect of high temperature oxidation in constituent mineral from Kami-Kometzuka scoria

Abstract

In this study, constituent minerals in the black and red-brown scorias from Kami-Komesuka, Aso, Kumamoto Prefecture, Japan were described in detail, their chemical compositions were determined, and the oxidation state of Fe in olivine were examined using electron microbeam method to evaluate effect of high temperature oxidation on the scoria.  The Kami-kometsuka scoria cone consists of black and reddish-brown scorias. The reddish-brown scoria is covered by black scoria. The red-brown scoria is expected to have subjected high temperature oxidation after eruption and deposition. The textures and chemical compositions of the olivine and pyroxene phenocrysts are changed by the effect of high temperature oxidation. In the olivine phenocrysts from reddish-brown scoria, precipitate minerals, less than few μm in size, are occurred and Fo composition are attend to 99 mol%.