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Nakata, Masataka*; Sasao, Eiji; Komuro, Kosei*
Resource Geology, 63(4), p.404 - 411, 2013/10
Times Cited Count：0 Percentile：0.04(Geology)Various secondary uranium minerals yield in oxidized zone near surface. These minerals indicate retardation of uranium in oxidized zone. Calcium and magnesium-bearing sabugalite occurs as aggregations of yellowish platy crystals in veinlets or druses in conglomerate from the oxidized parts of the Tono uranium deposit, Central Japan. X-ray powder diffractometry of this mineral has reflections consistent with previous powder diffraction data of sabugalite. Chemical analysis reveals the chemical composition of the minerals. SEM-EDS mapping shows that the mineral is compositionally uniform with no micron-scale layering. Charge of cations including Ca and Mg in the cation-H
O layer is 1.98 being identical to that of autunite group minerals. This suggests that the charge balance in the cation-HO layer of the mineral could be made by the alkaline earth or alkaline elements rather than by hydrogen ions.
Sasao, Eiji; Nakata, Masataka*; Komuro, Kosei*
Shigen Chishitsu, 62(3), p.225 - 233, 2012/11
Heavy minerals are examined in uranium ores, sandstones and basement granite around the Tsukiyoshi orebody, Tono uranium deposit. Heavy minerals in the uranium ores are composed mainly of biotite, hornblende and opaque minerals. One ore sample contains topaz, cassiterite, garnet and allanite. Heavy minerals in the non-mineralized sandstone consist mainly of hornblende, pyroxene and opaque minerals. Heavy minerals in basement granitic rocks are composed mainly of biotite. On the basis of heavy mineral composition, three sources of detritus are estimated, i.e., granitic rock, volcanic ash, and pegmatite or hydrothermal deposit. Uranium ores are proved to be embedded in the detritus mainly of granitic source, whereas the other sandstones in the Mizunami Group are mainly from volcanic source. Topaz and cassiterite in the ores are estimated to be derived from the pegmatite or hydrothermal deposits within the Naegi granite developed at the northeastern side of the Tsukiyoshi orebody.
Sasao, Eiji; Komuro, Kosei*; Nakata, Masataka*
Shigen Chishitsu, 59(3), p.209 - 217, 2009/10
Study of the stability and alteration of radioactive minerals in a placer deposit in the Naegi District, southeastern Gifu Prefecture, Central Japan contributes to understanding the modes of nuclide migration under various hydrogeological environments in the tectonically active Japanese Island Arc system. Under the optical and scanning microscopes, many grains of zircon have well-preserved crystal faces, whereas those of thorite were highly abraded and corroded. Most of monazite and fergusonite have partly abraded and corroded forms. This result indicates that uranium is strongly leached under oxidized hydrogeological environment but the behaviour is different for different minerals, being well harmony with the thermodynamic estimation. Leaching or release of uranium from radioactive minerals to surface geological environment is estimated to extend over long time under oxidized hydrogeological environment.
