吉備製鉄遺跡周辺地域の磁鉄鉱ざくろ石スカルン鉄鉱石の鉱物学的・地球化学的特徴

We conducted mineralogical and geochemical analysis of ore samples taken from locations surrounding the Jinmu, Sanpō, and Kōmoto mines in order to determine the source of iron ore uncovered from archaeological sites. The mineral composition of the magnetite-garnet bearing skarn deposits varies from mine to mine: while clinopyroxene and amphibole are present in the Jinmu and Sanpō samples, only a small amount of clinopyroxene occurs in the Kōmoto samples. The chemical compositions of magnetite and garnet are distinctive for each mine. Among the trace elements contained in the magnetite, Mg and Mn tend to be higher in the Kōmoto samples, Ti in the Jinmu samples, and Ca and Si in the Sanpō samples. The garnet from all the mines is andradite, but while the Kōmoto samples contain almost no Al, it is present in the Jinmu and Sanpō samples. Although samples were taken from a limited number of mine areas (three), our analysis provides an index for comparison with iron ore uncovered from archaeological sites, which will aid in provenance determination.