鳥取県多里地方のクロム鉄鉱と産状に関する研究(第1報)(I)

抄録

The Tari district is situated at about 43km southeast of Matsue city. The geological map of this district surveyed by the writer is shown in Figure 1. The Paleozoic sediments were intruded by chromite bearing ultra-basic rocks. As the chromites are always associated with serpentinized olivine or enstatite, the assumption is rejected that these chromites were originated from hydrothermal liquid. The size of disseminated chromite is 0.3 to 0.5mm. In thin section, the disseminated chromite has generally black margin and the massive chromite is commonly brownish yellow in color. The chromite is enriched in iron oxide and the serpentinite is relatively iron poor. The black materials of chromite are presumably ferrian chromite or chromian magnetite. The chromite from the deposite in the region is comparatively higher in MgO and Al₂O₃ contents, and it is lower in Cr₂O₃ than those from other areas in Japan. The content of FeO+Fe₂O₃ in disseminated chromite which is related to serpentinite is generally higher than that of massive chromite and has a reverse relation to that in green to yellow serpentinite. The disseminated chromites in the leuchtenbergite rocks, which are rich in A1₂O₃ content and poor in FeO+Fe₂O₃, are poor in A1₂O₃ and rich in FeO+Fe₂O₃.