Hydrothermal Alteration in the Tanakami Granite Pluton, Shiga Prefecture, Southwest Japan

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1 No., pp., * ** *** Hydrothermal Alteration in the Tanakami Granite Pluton, Shiga Prefecture, Southwest Japan Satoshi NAKANO, Norihiro YOSHIMI and Katsutoshi TOMITA Abstract The hydrothermal alteration of the Tanakami medium to coarse grained biotite granite has been studied in the Kumoi mine, Koka city, Shiga prefecture, Japan, by the field observations, microscopic observations and powder X ray diffraction analyses. As the results, it has been clarified that the hydrothermal alteration of its constituent minerals are sericitization and clay mineral formation, and extremely feldspathization syenitization including albitization and K feldspathization with quartz dissolution, and that the color variation of biotite to the naked eye is a useful tool for the field mapping of hydrothermally altered granites. Using the color varition of biotite, field observations were made to clarify the distribution pattern of hydrothermally atered granites over the area of the Tanakami granites. Dane and Ford, ; * ** ***

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$Shiga University ῌ t t H w x wΐx abc hi { }~ 7 ( ῑ 8$ aῌ ^_`+, $ 2 ( < mm 7b 8$ bῌ $ cῌ $ +, ^_l# $ 2(< mm 7w x a b c 8$$ $, ῒ8 ῐ X ῌ 9: ; <=>? @2ABCDCEFG# \ ] VW%^_`+, abcd 7Brown and Parsons, ῑ ; Walker et al.$

8 Shiga University ῌ t t H w x wΐx abc hi { }~ 7 ( ῑ 8$ aῌ ^_`+, $ 2 ( < mm 7b 8$ bῌ $ cῌ $ +, ^_l# $ 2(< mm 7w x a b c 8$ y z mno { }~ $ ( ῑ 8$ 2 ( < w ΐ x c $ aῌ mno$ bῌ h mno$ cῌ mno$ JES no P # $ KL 6MENOP # 7QRS T ῐ ῒ8$ UU VW% X #!"# < '()*+, YZ E P $ $ % & '()*+, -./ Brown and Parsons, ῑ ; Lee and Parsons, ΐ ; Lee et al., ῒ8 ῐ X ῌ 9: ; \ ] VW%^_`+, abcd 7Brown and Parsons, ῑ ; Walker et al., e ῒ8$ HI J %mnohi p # qrstu rstv '()*+, fg/chi jk l

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14 London Cooling histories of feldspars in the Tanakami and Shigaraki granites from the southeast to Lake Biwa, Japan, Asayama, T Radium content and chemical composition of granitic rocks in Japan, especially in the Tanakami Mikumo and Hiei regions, Shiga and Kyoto Prefectures. Mem. Fac. Ind. Arts, Kyoto Tech. Univ., Sci. & Tech., B. p.. Brown, W. L. and Parsons, I. Exsolution and coarsening mechanisms and kinetics in an ordered cryptoperthite series. Contributions to Mineralogy and Petrology,,. Brown, W. L. and Parsons, I. Alkali feldspars : ordering rates, phase transformations and behavior diagrams for igneous rocks. Mineral. Mag.,. Brown, W. L. and Parsons, I. Feldspars in igneous rocks : Parsons, I. ed. Feldspars and their reactions. NATO ASI Ser. C,. Dana, E. S. and Ford, W. E. Atextbook of mineralogy, th edition, Modern Asia edition, Jhon Wiley & Sons Inc., pp..,.,. p....,. Lee, M. R, Waldron, K. A. and Parsons, I. Exsolution and alteration microtextures in alkali felsdspar phenocrysts from the Shap granite. Mineral. Mag.,. Lee, M. R. and Parsons, I. Dislocation formation and albitization in alkali feldspars from the Shap granite. Am. Mineral.,. Le Maitre, R. W. Aclassification of igneous rocks and glossary of terms. Blackwell Sci. Public., pp. London, D. The application of experimental petrology to the genesis and crystallization of granitic pegmatites. Canad. Mineral.,,.

15 London, D. Granitic pegmatites. Trans. Royal Soc. Edinburgh, Earth Sci.,. London, D. Granitic pegmatites : an assessment of current concepts and directions for the future. Lithos,,.. Masutomilite,. p......,.. Parsons, I Feldspars and fluids in cooling pultons, Mineral. Mag,,. K Ar pp...,.,. Magma,,.... p.. Yoshizawa H., Ishizaka K., Kaneko, K. and Kawahara M. Geology and petrology of the Hira granite and mutual relations between granites in the North eastern Kinki district, Japan Mem. Coll. Sci., Univ. Kyoto, B,, Walker, F. D. L., Lee, M. R and Parsons, I. Micropores and micropermeable texture in alkali feldspars : geochemical and geophysical implications. Mineral. Mag.,.

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