Bulletin of the Geological Survey of Japan Top Page

Bulletin of the Geological Survey of Japan Vol.53 No.5/6 (2002)

Cover photograph | Table of Contents | Abstract

Cover photograph

Tungsten quartz veins of the Otani mine, Kyoto.

   The Otani mine, one of the largest tungsten mines in Japan mined until 1983, is composed of scheelite-chalcopyrite-pyrrhotite-quartz veins filling NNE fractures formed by right-lateral shearing in late Cretaceous biotite granodiorite with 98.9 Ma Rb-Sr age. The sulfides of the host granodiorite and ore veins have negative δ³⁴S values indicating a sedimentary biogenic source(see p. 461 - 477 in the text). This picture is taken at the Chuo Adit Level of No.2 Vein at north mining face of August. 1980. "Greisenization"was seen along the granodiorite contact.

(Photographed by Shunso Ishihara)

Table of Contents

Title	Author	PDF
Article
Paired Sulfur Isotopic Belts : Late Cretaceous-Paleogene Ore Deposits of Southwest Japan.	Shunso Ishihara and Akira Sasaki (461-478)	53_05_01.pdf [8,724 KB]
Short Article
Re-Os age of molybdenite from the Busetsu two-mica granite, central Japan.	Shunso Ishihara, Holly J. Stein and Ryoji Tanaka (479-482)	53_05_02.pdf [1,647 KB]
Notes and Comments
Distribution of mollusc shells in the Sea of Okhotsk, off Hokkaido.	Akihisa Kitamura, Ikuo Kawakami, Fushima Okamoto, Ken Ikehara, Atushi Noda and Hajime Katayama (483-558)	53_05_03.pdf [15,764 KB]

Abstract

Paired Sulfur Isotopic Belts: Late Cretaceous-Paleogene Ore Deposits of Southwest Japan

Shunso Ishihara and Akira Sasaki

   Sulfides from late Cretaceous-Paleogene ore deposits of the Inner Zone of Southwest Japan were analyzed for ³⁴S/ ³²S ratios (δ³⁴SCDT values) on 5 samples from the Ryoke Belt, 18 from the Sanyo-Naegi Belt, 15 from the Uetsu- Kanto District and 47 samples from the Sanin-Shirakawa Belt. Together with the published data, the average δ³⁴S values are calculated for individual deposits of the whole region; 109 localities for the ilmenite-series granitic belt and 56 localities for the magnetite-series granitic belt.
   The sulfur isotopic ratios vary regionally rather than with sulfide species or types and commodities of the ore deposits. The δ³⁴S values are generally negative in the fore-arc, ilmenite-series belt, and positive in the back-arc, magnetite-series belt. This regional variation is considered to reflect the ilmenite-/magnetite-series pairing of the genetically related granitic or volcanic activities, in which the positive δ³⁴S ore sulfur was derived from a deep igneous source, but the negative δ³⁴S sulfur was originated in biogenic sulfur of the accreted sedimentary complex. Within each terrane, δ³⁴S values and mineral commodities vary locally, which is called domains in this paper. A few negative δ³⁴S minima are observed in the Kinki, Hiroshima and Mino domains. These anomalies may have been brought by the most sediments-dominant granitic magmas generated within the accretionary sedimentary complex.
   The paired δ³⁴S belts, called the Japanese-type pattern, may be unique to island arcs where their fore-arc sediments have been accreted in the arc- front associated with the back-arc rifting.

Re-Os age of molybdenite from the Busetsu two-mica granite, central Japan.

Shunso Ishihara, Holly J. Stein and Ryoji Tanaka

   Molybdenite discovered in a pegmatitic dikelet in a quarry exposure of the Busetsu Granite in Okazaki City was dated at 76.4 ± 0.3 Ma using the Re-Os method. This age records the final stage of solidification of the Busetsu Granite and agrees well with previously reported CHIME monazite ages.