岩手県釜石鉱山天狗森鉱床のスカルン型銅鉱石の炭素・酸素同位体組成

• 春名 誠

  Department of Geosciences, The Pennsylvania State University University Park

• 大本 洋

  Department of Geosciences, The Pennsylvania State University, University Park

書誌事項

タイトル別名

• Oxygen and Carbon Isotope Studies on the Skarn-Type Ores at the Tengumori Copper Deposit of the Kamaishi Mine, Northeastern Japan
• Oxygen and Carbon Isotope Studies on th

抄録

The Tengumori deposit of the Kamaishi mine, Northeastern Japan, is a skarn-type copper ore deposit that develops near granitic intrusive rocks of Cretaceous age. Hydrothermal activity at the Tengumori deposit is divisible into three stages: 1) calc-silicate (divisible into clinopyroxene and garnet phases), 2) ore mineralization (chalcopyrite+pyrrhotite+quartz), and 3) calcite. The δ¹⁸O (SMOW) values were determined to be: +6.6to +7.8‰ for clinopyroxene (calc-silicate stage, 7 samples), +4.2 to +7.0‰ for garnet (calc-silicate stage, 14 samples), +12.0 to +13.7‰ for quartz (ore mineralization stage, 13 samples), and +10.6 to +12.8‰ for calcite (calcite stage, 19 samples). The oxygen isotopic temperatures calculated from the coexisting (but not contemporaneous) mineral pairs give consistent values of -330-460°C. However, they are higher than both of the pressure-corrected homogenization temperatures of fluid inclusions (-180-330°C) and the uppermost temperature of stability of chalcopyrite and hexagonal pyrrhotite (325°C). This temperature discrepancy is the result of changing δ¹⁸O_H2O value from -+7 to +9‰ in the cal-silicate stage, -+2 to +7‰ in the ore mineralization stage, and +1 to +5‰ in the calcite stage. The δ¹⁸O values of the calc-silicate stage solution can be interpreted as the unexchanged magmatic water or water in equilibrium with the host rocks. The hydrothermal solution of the ore mineralization stage is either magmatic water partially reequilibrated with the cooling pluton, water in equilibrium with the country rocks, or mixed solution with externally-derived water, e.g., local meteoric water. The δ¹³C (PDB) values of calcite crystals (calcite stage) range from -5.44 to -0.37‰. The calculated δ¹³C_H2CO3 values of the hydrothermal solution range from -5.8 to +1.4‰ and suggest that carbon was derived from both the granitic magma and the host limestone. Contributions of magmatic fluids to the calcite stage solution were recognized from the high salinity values (up to 23 wt. % equivalent NaCl) and the δ¹³C values of the calcite crystals.

収録刊行物

• 資源地質

  資源地質 46 (257), 125-136, 1996

  資源地質学会

キーワード

• Kamaishi mine
• Tengumori copper deposit
• Skarn
• Oxygen and carbon isotopes

詳細情報

• CRID: 1390282679444875008
• NII論文ID: 10002858418
• NII書誌ID: AN10379890
• DOI: 10.11456/shigenchishitsu1992.46.125
• ISSN: 21854033
• ISSN: 09182454
• NDL書誌ID: 4019555
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I4019555
• データソース種別:
  • JaLC
  • NDL
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可