The Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists

The study of the equilibrium in the system FeS-S₂ (I) Dissociation equilibrium of pyrite at the low temperature

Shimpei Kano, Matsuo Nambu

1967 Volume 57 Issue 3 Pages 81-97
Published: March 05, 1967
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.57.81

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In the system FeS-FeS₂ below 325°C, there have not been ascertained what kind of solid phase coexists at equilibrium with pyrite (FeS₂), though some investigators have suggested it may be monoclinic pyrrhotite (Fe₇S₈). In order to establish the phase relation in this area, the authors measured the equilibrium of the system Fe_1-xS-FeS₂-S₂ with the natural pyrite, in the temperature range 240-180°C, using the transportation method by the hydrogen gas stream.
The experimental results show that the solid phase coexisting at equilibrium with pyrite is hexagonal pyrrhotite, whose d₁₀₂-value is 2.070±0.001 A, corresponding to the composition 47.7 atomic % Fe and is not depending upon the temperature. The temperature dependance of the dissociation pressure is gained as follows:
2FeS₂(Py)=2FeS(po)+S₂
log Ps2=18662/T+19.27
(180°-240°C)
From the additional heating experiment carried out in the air-atmosphere it is suggested that the monoclinic pyrrhotite may be produced under the existence of oxygen at the temperature below 325°C.

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Heavy mineral analyses of the surface Neogene sediments and the cuttings from Higashi Ishinazaka Oil Well.

Masaharu Watanabe, Nobuyoshi Ushijima

1967 Volume 57 Issue 3 Pages 98-110
Published: March 05, 1967
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.57.98

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studies were made on the heavy mineral assemblages of the coarse clastic sediments, - tuffs, tuffaceous sediments and sand-stones, - obtained from the Dewa hilly land in the east of Sakata city, Yamagata prefecture.
The same studies were carried out on the cuttings from Higashi Ishinazaka R-1 Oil Well.
The results showed a fairly close correlation between the surface and the subsurface data, and also showed the usefulness of the heavy mineral analyses to the subdivision of the formation.
Studies on the refractive indices of the plagioclases in the tuffs of this area revealed a dacitic composition.

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Kaersutite pyroxenite inclusion in trachybasalt from Takenotsuji, Iki Island

Ken-ichiro Aoki

1967 Volume 57 Issue 3 Pages 111-119
Published: March 05, 1967
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.57.111

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Kaersutite pyroxenite niclusion has been found in the Takenotsuji trachybasalt scoria fall, Iki Island, southwestern Japan, It consists of 65% by volume of augite and 35% of kaersutite (completely changed to oxykaersutite). It includes less than 0.1% of orthopyroxene and the same volume of chromian spinel as accessory minerals. Both augite and kaersutite have been separated and analysed chemically.
From its petrographic and mineralogical character, it is concluded that the inclusion does not represent a fragment of the upper mantle; instead, it represents a cumulus phase, crystallized from an alkali olivine basalt magma at the middle to upper portion of the crust (about 20 to 10km beneath the surface).

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[title in Japanese]

1967 Volume 57 Issue 3 Pages 123-135
Published: 1967
Released on J-STAGE: July 13, 2012

DOIhttps://doi.org/10.2465/ganko1941.57.123

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