Mining Geology

Relationships Among Carbonate-Replacement Gold Deposits, Gold Skarns, and Intrusive Rocks, Bau Mining District, Sarawak, Malaysia

Timothy J. PERCIVAL, Arthur S. RADTKE, William C. BAGBY

1990 Volume 40 Issue 219 Pages 1-16
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.1

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Three distinct styles of gold mineralization are spatially associated with Miocene microgranodiorite porphyry stocks in the Bau mining district, Sarawak, Malaysia. These include: (1) gold-bearing calcic skarns; (2) several varieties of veins near and distal to calcic skarns; and (3) carbonate-replacement ore bodies in sedimentary rocks peripheral to the veins and typically furthest from the stocks. Most of the gold produced to date from the Bau district originated from the carbonate-replacement deposits. These deposits exhibit strikingly similar mineralogical and geochemical features with Carlin-type deposits that occur in the western United States.
Similarities in key mineralogical and chemicall features of the ores indicate that all three styles of mineralization are not only spatially, but genetically, related to the microgranodiorite porphyry stocks. Preliminary fluid inclusion measurements on quartz from the three gold ore types suggest decreasing thermal and salinity gradients with increasing distance from the stocks.

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Mineralization Ages of Some Epithermal Gold-Silver Vein-type Deposits in the Central Kitami Mining District of the Kitami Metallogenic Province, Hokkaido, Japan

Hiroyuki MAEDA

1990 Volume 40 Issue 219 Pages 17-22
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.17

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The mineralization ages of some epithermal gold-silver vein-type deposits in the Kitami metallogenic province, Hokkaido, Japan have been studied based on the K-Ar dating on the vein adularia and quartz mixtures. The Kohnomai mineralization took place in Middle Miocene time (12.9±0.4 Ma). On the other hand, the gold-silver mineralization in the Ikutahara-Rubeshibe area occurred in Late Miocene to Early Pliocene time (Ryuo mine: 7.7±0.2 Ma; Shakinzawa mine: 7.4±0.2 Ma; Muka mine: 6.6±0.2 Ma; Saroma mine: 5.3±0.5 Ma).

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Mineralization Characteristics in the Cumbre Area, Huanala Mining District, Central Peru

Yasumasa FUKAHORI, Kaoru SAKOGAICHI

1990 Volume 40 Issue 219 Pages 23-33
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.23

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Ores in the deposits of Cumbre area located about 2km south of the Huanzala mine, Peru, are divided into the clayey ores, pyritic ores and Shiroji ores, based on their mineral compositions. The skarn ores which have been reported from the Huanzala mine area are absent in this area, while the clayey ores have been identified from this area.
In the Cumbre area, the pyritic ores and dolomitic ores are principal primary ores. The Shiroji alteration following the primary mineralization has formed silicified zone around the pyritic ores. By the Shiroji alteration, the dolomitic ores were converted in part to the Shiroji ores.
When these primary ores were uplifted and eroded, gossan has been formed near the surface by oxidation. Strong argillization has occurred in the portions underneath the gossan by down-going meteoric water and lead has redeposited as anglesite and lead-bearing jarosite in the argillized zone by reaction of galena with ferric sulfate-bear-ing water. However, zinc sulfate thus formed has been leached out due to its high solubility in water.

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Indium-Bearing Ore from the Goka Mine Naegi District, Southwestern Japan

Satoshi MURAO, Masanori FURUNO

1990 Volume 40 Issue 219 Pages 35-42
Published: March 31, 1990
Released on J-STAGE: December 14, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.35

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Indium-containing ore was found from the Goka mine. The ore is mainly composed of sulfides like chalcopyrite, sphalerite, stannite, arsenopyrite, galena, cassiterite and gangue minerals. Microprobe analyses indicate that the indium carriers in the Goka mine are sphalerite (<1.89 wt%In), stannite (<9.63 wt%In), chalcopyrite (<0.4 wt%In), and cassiterite (<1.21 wt%In).
In addition to the minerals mentioned above, Zn-Cu-Fe-In-Sn-S minerals of varying chemical composition are observed. Their formula is expressed as mCu(In, Sn)S₂·n(Zn, Fe)S, where most of the analysis data show m:n=1:2 or 1:4.
The occurrence of the indium minerals at the Goka mine gives an additional evidence that the tin-polymetallic veins are important indium concentrating geologic bodies.

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[title in Japanese]

1990 Volume 40 Issue 219 Pages 43-69
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.43

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[title in Japanese]

1990 Volume 40 Issue 219 Pages 70-74
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.70

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[title in Japanese]

1990 Volume 40 Issue 219 Pages 72-74
Published: March 31, 1990
Released on J-STAGE: June 12, 2009

DOIhttps://doi.org/10.11456/shigenchishitsu1951.40.72

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