GEOCHEMICAL JOURNAL

K-Ar ages of the Izu-Bonin Islands

Ichiro Kaneoka, Naoki Isshiki, Shigeo Zashu

1970 Volume 4 Issue 2 Pages 53-60
Published: 1970
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.4.53

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Several volcanic rocks from O-shima, Kozu-shima and Hachijo jima of the Izu Islands, from Chichi jima and Haha jima of the Bonin Islands and from Iwo jima of the Iwo Islands were dated by K-Ar method. The rocks from the Izu Islands give the ages of less than 2-3 m.y., while the ages of the rocks from Chichi jima and Haha jima are about 30-40m.y. The rock from Iwo-jima indicates a very young K-Ar age of about 0.03m.y. These results confirm that there is a clear difference in age of volcanic activity between the Izu Islands and the Bonin Islands. This difference has also been suggested geologically.

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Calcium chloride type water discharged from the Matsushiro area in connection with swarm earthquakes

Ryuma Yoshioka, Setsuo Okuda, Yasushi Kitano

1970 Volume 4 Issue 2 Pages 61-74
Published: 1970
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.4.61

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The authors determined the chemical composition of ground water which gushed out in connection with swarm earthquakes in the Matsushiro area (Nagano Pref., Central Japan), from September 1966 to December 1968. This paper shows the variation in the chemical composition of the ground water with time and the remarkable increase in the calcium, chloride and carbon dioxide contents with increasing activity of the swarm earthquakes. A hypothesis on the origin of the waters is also presented.

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Detection of zonal structure of garnet by activography

Shohei Banno, Masanobu Sakanoue, Takashi Nakanishi

1970 Volume 4 Issue 2 Pages 75-81
Published: 1970
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.4.75

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The distribution of Mn and Fe in thin sections of rocks can be detected by activography (activation auto radiography). This technique was applied to detect the zonal structure of garnet. It is shown that garnets of low-temperature eclogites are commonly zoned having Mn-rich core and Mn-poor rim.

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³⁶CI in iron meteorites

Hideki Matsuda, Kinuko Horie, Masatake Honda

1970 Volume 4 Issue 2 Pages 83-86
Published: 1970
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.4.83

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³⁶Cl contents were determined in some iron meteorites, and the results were compared with the ²⁶Al, ²¹Ne and ³⁶Ar contents of the same meteorite samples. Terrestrial ages and cosmic ray exposure ages of these meteorites were estimated with these nuclide contents. Similar cosmic ray exposure ages were obtained from ³⁶CI and ²⁶Al with terrestrial age correction.

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Copper and Showashinzan zinc in fumarolic gases of volcano, Hokkaido, Japan

Yoshihiko Mizutani

1970 Volume 4 Issue 2 Pages 87-91
Published: 1970
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.4.87

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The concentrations of Cu and Zn in the fumarolic gases of Showashinzan volcano were determined. Gases with high Cl and low H₂S contents contain more Cu and Zn than do those with low Cl and high H₂S contents. The deposition of Cu and Zn as sulfides may be an important factor controlling the behavior of volatile Cu and Zn compounds in fumarolic gases. The amounts of Cu and Zn discharged from fumarole A-1 in 1958 are estimated as 4.8 and 540kg, respectively.

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