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Yuguchi, Takashi; Sasao, Eiji; Ishibashi, Masayuki; Nishiyama, Tadao*
American Mineralogist, 100(5-6), p.1134 - 1152, 2015/05
Times Cited Count：33 Percentile：74.26(Geochemistry & Geophysics)This paper describes the biotite chloritization process with a focus on mass transfer in the Toki granitic pluton, Central Japan, and also depicts the temporal variations in chemical characteristics of hydrothermal fluid associated with chloritization during the sub-solidus cooling of the pluton. Singular value decomposition (SVD) analysis results in chloritization reaction equations for eight mineral assemblages, leading to the quantitative assessment of mass transfer between the reactant and product minerals, and inflow and outflow of components through the hydrothermal fluid. The matrices for SVD analysis consist of arbitrary combinations of molar volume and closure component in the reactant and product minerals. The eight reactions represent the temporal variations of chemical characteristics of the hydrothermal fluid associated with chloritization: the progress of chloritization results in gradual increase of silicon, potassium and chlorine and gradual decrease of calcium and sodium in the hydrothermal fluid with temperature decrease. The biotite chloritization involves two essential formation processes: Formation Process 1, small volume decrease from biotite to chlorite and large inflow of metallic ions from the hydrothermal fluid, and Formation Process 2, large volume decrease and large outflow of metallic ions into hydrothermal fluid. Chlorite produced during Formation Process 1 dominates over that of Formation Process 2, resulting in the gradual decrease of metallic components in the hydrothermal fluid with chloritization progress. The combination of continuous reactions based on compositional variations in chlorite together with corresponding continuous Al
variations gives an indication of the temporal variations in rates of decreasing and increasing concentration of chemical components in the hydrothermal fluid associated with chloritization.
PNC TJ1412 97-002, 157 Pages, 1997/03
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Onuki, Toshihiko; Murakami, Takashi; Sato, Tsutomu; Isobe, Hiroshi
Nihon Genshiryoku Gakkai-Shi, 34(12), p.1139 - 1142, 1992/12
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Yuguchi, Takashi; Sasao, Eiji; Ishibashi, Masayuki; Nishiyama, Tadao*
no journal, ,
no abstracts in English
Ogita, Yasuhiro; Niki, Sota*; Nagata, Mitsuhiro; Hirata, Takafumi*; Yuguchi, Takashi*
no journal, ,
Alteration process in granitic rocks is important for mass transfer through rock-fluids interactions and the formation of microcracks as a pathway of ground water. Timescale of alteration in granitic rocks is enough unrevealed because limited methodologies are available. Focusing on biotite chroritization and following precipitation of titanite (sphene) during hydrothermal alteration in granitic rocks, hydrothermal titanite leads to geochronological constraint on timescale of alteration. This study reports U-Pb age of hydrothermal titanite from Tono Plutonic Complex (TPC), Kitakami Mountains, northeast Japan, and interprets its age comparing other geochronological data. Thinsection observation suggests that titanite from the TPC sample was secondary precipitated related to biotite chloritization during subsolidus stage. In thinsections, titanite is not enough to analyze using laser ablation-inductively coupled plasma-mass spectrometry. This study conducted U-Pb analysis for separated titanite and obtained age of 118.7
1.5 Ma. The occurrence of titanite shows that titanite was precipitated accompanied biotite chloritization during hydrothermal alteration in the TPC. Thus, the age of titanite is potentially able to constrain on hydrothermal activity during subsolidus stage of TPC. Moreover, the obtained age falls within zircon U-Pb age (1172 Ma) and biotite K-Ar age (122.62.7 Ma) reported from central facies of TPC. This indicates hydrothermal alteration process related to biotite chloritization has experienced short period during cooling on TPC.
