鉄-チタン酸化鉱物のEPMA (ElectronProbe Microanalyzer) による研究

抄録

The oxide minerals belonging to FeO-Fe₂O₃-TiO₂ system are studied by means of reflection microscope and electron probe microanalyzer. The studied samples are placer iron ores, iron are minerals in gabbro and iron ores from some pyrometasomatic deposits. Iron, titanium, vanadium, manganesein the iron are minerals are analyzed quantitatively by electron probe microanalyzer. Iron placer in the Ariake Bay (Western Japan) derived from the decomposition of andesites and their pyroclastics is mainly composed of titaniferous magnetite, magnetite, titaniferous hematite and ilmenite. Exsolution textures of magnetite (titaniferous magnetite) ilmenite and of magnetite-hematite (titaniferous hematite) are recognized. It is noticeable that in the above exsolution texture of magnetite-hematite the titanium is detected in hematite, and not in magnetite. Refering the results of analyses of titanium in magnetite and hematite to the phase diagrams, it is inferred that these minerals would be formed under the unequlibrium condition of rapid cooling. This interpretation may be verified by the fact that these minerals were derived from the decomposition of andesites and their pyroclastics.
A little or no titanium and vanadium are detected in magnetite or hematite genetically related to granitic rocks.