| 概要 |
The modes of occurrence, parageneses, and chemical composition of alabandite and associated minerals in sixty-three samples from nineteen manganese deposits in Japan are described on the basis of micr...oscopic observation, X-ray powder diffraction, and electron probe microanalysis. From the results obtained, the parageneses and chemical composition of alabandite are grouped into three types by the differences of the modes of occurrence. In the first type, alabandite occurs in coarse-grained rhodochrosite ore in Tertiary vein-type deposits with FeS content of 0.6 to 5.8 mol.%. In the second type, alabandite is dispersed in fine-grained rhodochrosite ore in unmetamorphosed bedded-type deposits with FeS range of 0.2 to 6.6 mol.%. In the third type, alabandite occurs abundantly in manganese silicates and oxides ore in thermally metamorphosed bedded-type deposits and has 0.3 to 13.5 mol.% FeS. The two bedded-type deposits were formed in Paleozoic to Mesozoic age. In the second and third types, the FeS content in alabandite is closely correlated to the kinds of the associated minerals. Namely, the FeS content in alabandite associated with manganese oxides ore, tephroite ore, and rhodonite ore is less than 2 mol.%, 4 mol.%, and 13.5 mol.%, respectively. Especially in the third type, the above data indicate that FeS content of alabandite generally increases from the central to the peripheral parts of ore bodies. This variation of the FeS content is explained not only by the differences in the distribution ratios of iron between alabandite and associated manganese oxides and silicates but also by the introduction of iron accompanied with sulfur into ore body during thermal metamorphism. Moreover, considering the stability field of alabandite which was thermochemically calculated by using the selected principal reactions, it seems that alabandite could be frequently found in nature.続きを見る
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Mendeley出力
24_04_p207