秋田県餌釣黒鉱鉱床の金銀鉱石 Gold and silver ores from the Ezuri Kuroko ore deposits, Akita Prefecture, Japan

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著者

    • 小野 修司 ONO Shuji
    • 北海道大学工学部資源開発工学科 Department of Mineral Resources Development Engineering, Faculty of Engineering, Hokkaido University
    • 佐藤 壽一 SATO Juichi
    • 北海道大学工学部資源開発工学科 Department of Mineral Resources Development Engineering, Faculty of Engineering, Hokkaido University

抄録

The Ezuri Kuroko deposits are located approximately at 140°36'of east longitude and 40°15' of north latitude in the Hokuroku district of Akita Prefecture. The ore deposits are hosted by basaltic tuff and dacitic rocks of the Miocene age, and they are composed mainly of stratiform black ores.<br>   In this paper, the features of Au- and Ag-bearing ores and minerals are described, and the environment of the mineralization is estimated from the FeS content of sphalerite and the data of fluid inclusions in sphalerite.<br>   Gold- and/or silver-bearing minerals identified by microscopic examination and electron microprobe analysis are electrum, stromeyerite, pearceite, mckinstryite, argyrodite and fahlore (up to 7.8 atomic % Ag). These minerals are particularly found in fine-grained massive black ore. Most of electrum contains 30-40 atomic % Ag, and Ag distribution of an individual grain is comparatively homogeneous. Silver content of black ore (20-1, 260 ppm) is dependent on the amount of fahlore as well as of other silver minerals.<br>   The ranges of homogenization temperatures of fluid inclusions in sphalerite are 236°-283°C (breccia-like black ore), 210°-279°C (massive black ore) and 165°-230°C (coarse-grained sphalerite filling cavities in massive black ore), respectively. The FeS content of sphalerite coexisting with electrum is less than 0.2 mole%. Taking account of the effect of pressure, it is deduced from these data that Au- and Ag-bearing ores were formed in a range of ca. 240°-290°C under the condition of a high activity of sulfur. Furthermore, it appears that gold was precipitated from Au(HS)<sub>2</sub><sup>−</sup> complex mainly owing to cooling and a decrease in H<sub>2</sub>S concentration of ore-forming fluids caused by mixing with seawater and/or by precipitation of metal sulfides.

収録刊行物

  • 岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology  

    岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology 90(8), 268-279, 1995-08-05 

    Japan Association of Mineralogical Sciences

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各種コード

  • NII論文ID(NAID)
    10002029426
  • NII書誌ID(NCID)
    AN10047992
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    09149783
  • NDL 記事登録ID
    3624121
  • NDL 刊行物分類
    ME51(鉱物・鉱床)
  • NDL 雑誌分類
    ZM46(科学技術--地球科学--岩石・鉱物・鉱床)
  • NDL 請求記号
    Z15-71
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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