岡山県山宝鉱山産の含錫鉄鉱石について (第1報)

Abstract

The iron deposits of the Sanpo mine, Okayama Prefecture have been emplaced in Palaeozoic limestone, and are of contact-metasomatic origin genetically related to granitic rocks of the late Cretaceous or the early Tertiary age. It is a remarkable fact that magnetite ores from the iron mine contain appreciable amounts of Sn, ranging from O. OX to O. X per cent.In a series of studies, of which this is the first, an attempt will be made to clarify the mode of distribution of Sn in the ore-bodies, and the manner of the presence of Sn in the stanniferous iron ores by means of field work, microscopic observation, spectrochemical analysis, X-ray diffractometry and electronprobe microanalysis. This first report dealt with the mode of distribution of Sn in ore-bodies and led to the following results:(1) In the central zone of iron mineralization (zone of massive magnetite ore), the Sn content is high as much as O. X per cent order. Whereas the outer zone (zone of magnetite and calcite) at the limestone side decreases Sn content, showing usually O. OX per cent order.(2) At the end of ore-bodies on the underground geological plan map, where iron mineralization is very slight, Sn content is usually low as much as 0.0X per cent order.(3) No definite relationship between paragenesis of main metallic minerals and the Sn content in the iron ores was recognizable.(4) Post-ore dykes of porphyrite did not affect the Sn content of the ore-bodies.(5) Cassiterite showing minute subhedral crystals was optically identified in the iron ore having maximum contents of Sn (No.4-12).(6) The magnetite concentrate obtained by use of magnetic separator showed remarkable decrease of Sn content as compared with the crude ore, and this suggests that almost whole of Sn is not contained in magnetite structure by ionic substitution, but contained in cassiterite and other Sn-bearing crystalline phases.