兵庫県，平木鉱山における熱水性カオリン鉱床の地質学的及び地球化学的研究

DOI Web Site 被引用文献1件 参考文献24件
  • ココ ミント
    Department of Earth and Planetary Sciences, Faculty of Science, Hiroshima University
  • 渡辺 洵
    Department of Earth and Planetary Sciences, Faculty of Science, Hiroshima University

書誌事項

タイトル別名
  • Hydrothermal kaolin deposit at the Hiraki mine, Hyogo Prefecture, Japan: Geology and geochemical mass-transfer.
  • 兵庫県,平木鉱山における熱水性カオリン鉱床の地質学的及び地球化学的研究〔英文〕
  • ヒョウゴケン ヒラキ コウザン ニ オケル ネッスイセイ カオリン コウショ

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抄録

A kaolin deposit at the Hiraki mine occurs in the rhyolitic non-welded tuff sandwiched between underlying rhyolite and overlying rhyolitic welded tuff of Late Cretaceous. Volcanostratigraphy of the mine area is designated as follows: (in descending order) the Hiraki rhyolitic vitritic welded tuff; the Hiraki non-welded tuff (with three members), and the rhyolite. The deposit was formed by the interaction between the rhyolitic non-welded tuff and acid fluids whichpassed mainly through the fracture zones formed after the emplacement of the overlying welded tuff. Mineralogically it is composed exclusively of kaolin group with a few chlorite, illite, montmorillonite, mixed-layer clay minerals, sericite and pyrophyllite, confined to fracture zones, and ubiquitous occurrence of quartz throughout the deposit in varying degrees of abundance. Essentially it is a kaolinite monomineralic deposit, showing no distinct zonal distribution of alteration mineral assemblages. Chemically, these volcanic and pyroclastic rocks are all of low alkali and peraluminous. Variation diagrams for incompatible element pairs, both major and trace elements, suggest that the deposit was altered from a single precursor, the rhyolitic non-welded tuff. Mass-transfer calculation and petrographic evidences reveal the followings: (1) dissolution of CaO, Na2O, K2O, Fe2O3 and MnO in the kaolinite zone; (2) slight enrichment of K2O and Fe2O3 in the sericite “zone”* and chlorite “zone”, respectively; (3) dissolution of silica at the initial stage and later precipitated as quartz from the fluid introduced to the system during alteration process; (4) immobility of Zr, Nb, TiO2, and Al2O3 in the whole deposit; (5) concentration of Al2O3 might vary from 15 to 24 wt% within the non-welded tuff.<br>* The word “zone” is used as an informal term for the mineral assemblages with indistinctive boundary in spatial distribution.

収録刊行物

  • 岩鉱

    岩鉱 90 (9), 310-326, 1995

    一般社団法人　日本鉱物科学会

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