|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1996 : ¥1,700,000 (Direct Cost : ¥1,700,000)
Characteristics of the occurrence of gold, silver and rare metals in the Toyohaand around the Teine hydrothermal metallic deposits were examined on the basis of mineral chemistry and microthermometry of fluid inclusions.
In the southwestern part of the Toyohapolymetallic vein-type deposits, gold, silver and rare metals such as bismuth, indium and tellurium are locally concentrated.Gold occurs as electrum containing 14-55 atom.% Ag, and the temperature of gold deposition is estimated to be 230-290ﾟC.The Ag content and the temperature are low and high, respectively, compared with the data from the veins formed by earlier stage mineralization. Silver and bismuth occur as pb-Bi-Ag minerals and are contained in galena up to a few wt.%. Silver also occurs as hessite, Te-bearing canfieldite, canfieldite and Ag-bearing tetrahedrite (3-19 wt.% Ag). Indium is mainly contained in kesterite (up to 6.8 wt.%), stannite (2.3 wt.%) and sphalerite (4.8 wt.%). The temperatures and salinities of the silver and indium minralization are estimated to be 250-320ﾟC and 4-5 wt.%.
The Teine ore deposits and Harukayama minerlized area are characterized by gold, silver, tellurium and bismuth minerals. The homogenization temperatures and salinities of fluid inclusions in both epithermal mineralization are almost the same. Therefore, the natures of epithermal gold mineralization in southwestern Hokkaido may be regarded as having changed from high sulfidation type characterized by gold-silver-telllurium- (bismuth) in 5-3.6Ma (Teine, Harukayama and Kobetsuzawa) to low sulfidation type charaterized by gold-silver-selsnium at 1 Ma (Koryu).