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Niwa, Masakazu; Ueki, Tadamasa*; Hoshi, Hiroyuki*; Sugisaki, Yuichi*
JAEA-Research 2020-003, 33 Pages, 2020/07
JAEA-Research-2020-003.pdf:5.69MB
Ages of volcanic rocks are helpful information to understand the impact of volcanism concerning a site characterization and a safety assessment for geological disposal. In this study, mineralogical and geochemical data of altered volcanic rocks were collected using a polarizing microscope, X-ray diffractometer, X-ray fluorescence spectrometer, X-ray analytical microscope, and electron probe microanalyzer, to select targets suitable for reliable K-Ar dating. In addition, sample preparation procedures such as freeze-thawing and HCl treatment were examined to concentrate unaltered plagioclase which is one of major phenocrysts in volcanic rocks. These data and procedures were compiled in this report.
Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Tamura, Hajimu; Shibata, Kenji
no journal, ,
X-ray diffraction analysis and K-Ar dating were applied for fault gouges in the late Cretaceous Kojaku Granite, Tsuruga Peninsula. The fault gouge includes smectite, 1M
type illite, and kaolinite, based on the X-ray diffraction analysis. The K-Ar dating shows approximately 39 to 45 Ma for the 
0.1 
m size fractions separated from the gouges. The K-Ar ages and the reconstructed cooling history of the granite suggest that the 1M illite was formed at 60 to 110 
C (approximately 2 to 4 km in depth for 30 C/km of geothermal gradient).