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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.
Sasao, Eiji; Iwatsuki, Teruki; Amano, Yuki
Shigen Chishitsu, 56(2), p.125 - 132, 2006/12
In the Tono uranium deposit, most of the uranium has been preserved, even though the deposit has been subjected to the effects of several cycles of uplift, erosion and subsidence since its formation. In order to enhance confidence in the demonstration of long-term safety of a geological disposal system for high-level radioactive waste in a geologically active area such as the Japanese Islands, it is necessary to understand how geological phenomena have affected deep geological environments. To contribute the studies of the Tono uranium deposit to paleohydrogeology, it is important to determine any long-term changes and to evaluate the stability of the geological environments. Because the deep geological environment is affected by many factors such as groundwater flow, microbes, water-rock interaction and so on, a paleohydrogeological approach is essential to know the state of ancient, deep geological environments which might influence the the preservation or mobilization of uranium.
Shoji, Tesuya*
Shigen Chishitsu, 46(2), p.95 - 112, 1996/00
None
Yang, X.
Shigen Chishitsu, 46(4), p.233 - 243, 1996/00
None
