秋田県餌釣黒鉱鉱床の金銀鉱石

• 小野 修司

  北海道大学工学部資源開発工学科

• 佐藤 壽一

  北海道大学工学部資源開発工学科

書誌事項

タイトル別名

• Gold and silver ores from the Ezuri Kuroko ore deposits, Akita Predecture, Japan.
• アキタケン エズリ クロコウ コウショウ ノ キン ギン コウセキ

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)₂⁻ complex mainly owing to cooling and a decrease in H₂S concentration of ore-forming fluids caused by mixing with seawater and/or by precipitation of metal sulfides.

収録刊行物

• 岩鉱

  岩鉱 90 (8), 268-279, 1995

  一般社団法人　日本鉱物科学会

キーワード

• Ezuri ore deposit
• Kuroko
• Electrum
• Silver mineral
• FeS content of sphalerite
• Fluid inclusion
• Homogenization temperature

詳細情報

• CRID: 1390001206234775680
• NII論文ID: 10002029426
• NII論文ID: 30022306415
• NII書誌ID: AN10047992
• DOI: 10.2465/ganko.90.268
• COI: 1:CAS:528:DyaK2MXosFCgurk%3D
• ISSN: 18813275
• ISSN: 09149783
• NDL書誌ID: 3624121
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I3624121
• 本文言語コード: ja
• データソース種別:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可