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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.
Komuro, Kosei; Sasao, Eiji
JNC TY7400 2004-003, 707 Pages, 2004/05
This cooperative research program between University of Tsukuba and Japan Nuclear Cycle Development Institute performs a natural analogue study of uranium deposits, specially the Tono uranium deposit, using many methods to understand a material cycle, with the aim of clarification of long-term preservation and migration of radionuclide in various geological environments in Japan.
; Sato, Kazuhiko; Komuro, Kosei
Proceedings of Migration '97, 0 Pages, 1997/00
None
; Komuro, Kosei
Proceedings of Migration '97, P. 87, 1997/00
None
Koyama, Kazutoshi; Komuro, Kosei*
Annual report of the Institute of Geoscience, the University of Tsukuba, 19, p.73 - 78, 1993/00
None
Yui, Mikazu; Takeda, Seietsu; Komuro, Kosei*; Makino, Hitoshi; ; ; Ishiguro, Katsuhiko
PNC TN8410 92-166, 174 Pages, 1992/09
None
Clozel, B.*; Komuro, Kosei; Nakashima, Satoru*; Nagano, Tetsushi*; Masaki, Nobuyuki*; Hayashi, Hisato*
PNC TN6410 92-004, 32 Pages, 1992/03
Rock samples from different world U deposits mainly in sedimentary rocks have been studied by Electron Spin Resonancc (ESR) spectroscopy and Cathodoluminescence (CL) measurement in order to characterize radiation damage centers in clays and quartz. The presence of kaolinite-like radiation centers ill ESR spectra in some of the samples containing kaolin group minerals suggests that this type of radiation damages can be used as an indicator of U behavior during supergene and hydrothermal alteration of U ores. Other clay minerals such as smectite and illite were not found to exhibit radiation damage centers by ESR. CL measurement on quartz grains iadicated the presence of radiation damage rims for the samples containing high U content. These rims can also be recognized for older samples with low U cocentration because of the longer contact of quartz with U. Although much more systematic studies are need for the reconstruction of the U behavior, these two methods have been proven useful for the characterization of radiation damage histories recorded in minerals.
Sasao, Eiji; Komuro, Kosei
no journal, ,
no abstracts in English
Yaguchi, Masashi*; Komuro, Kosei*; Sasao, Eiji
no journal, ,
Minor amount of daughter radionuclides such as radium and radon are detected in the groundwater of the Tono area, where sandstone-type uranium deposits are embedded. Recently, lead isotopic ratios are measured for the uranium ores and two distinct different isochrons are found in the 
Pb/
Pb-
U/Pb diagram, showing that distinct radionuclides migration have not been occurred recently. In order to understand the radionuclides migration and its effect on lead isotopic ratios, simulation of radionuclides migration on the basis of transport theory are made for groundwater and ores in the Tono uranium deposits. The results on the basis of the proper assumption for the Tono area will be reported. The lead isotopic results would not be incompatible with the results of uranium series disequilibria.
Komuro, Kosei*; Yaguchi, Masashi*; Sasao, Eiji
no journal, ,
The Tono sandstone-type uranium deposits occur in the basal conglomerates of middle Miocene Toki lignite-bearing formation in the Mizunami group, which rest on the late Cretaceous granitic basement. In order to understand the age, origin, formation process, and radionuclides migration behavior of the deposits, lead isotopic compositions were measured for uranium ores and the associated sedimentary and granitic rocks. The Tono sandstone-type uranium deposits were formed by initial deposition caused by reduction of uranium in association with the decomposition of the plant materials at the time of the deposition of host conglomerates and sandstones in the Toki lignite-bearing formation, the uranium of which originated from the granitic basement. At the time of deposition of Seto group after the upheaval of this region, some parts of these ores dissolved by oxidative groundwater and the secondary ores were formed by the subsequent re-deposition by reduction.
