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

Tertiary plutonic rocks in western Chügoku

Nobuhide Murakami

1959 Volume 43 Issue 4 Pages 167-178
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.167

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The four areas of Miocene age are distributed in western San-in; namely, in Kawato, Hamada, Masuda, and Susa district, from east to west. The lower parts of these Tertiary formations are composed of andesites, liparites, and plutonic rocks (dioritic and granitic rocks), which are considered of Oligocene age, by the field evidence and by the zircon method. In this paper, the petrographic features of these plutonic rocks are discussed briefly.

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Actinolite in the eastern part of the Kanto Mountains

Yôtarô Seki

1959 Volume 43 Issue 4 Pages 179-184
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.179

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Glaucophanitic regional metamorphic terrain in the eastern part of the Kanto Mountains can be divided into the following two parts; pale coloured actinolite zone and greenish blue actinolite zone. Though the greenish blue actinolite is only found in the highest grade part of the terrain; “spotted schist zone”, pale coloured actinolites are chiefly distributed in the non-spotted schists, phyllites or weakly metamorphosed Paleozoic formation. These two kinds of actinolite can be easily discriminated to each other by their optical properties (Figure 1).
Chemical, optical and X-ray data of these two actinolites are also given in this paper.

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Potash felspars in some metamorphic rocks

Mitsuo Shimazu

1959 Volume 43 Issue 4 Pages 185-193
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.185

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Potash felspars in the Akka metamorphics (contact metamorphic rocks), several other metamorphics and granites are studied optically and by the x-ray powder method. Triclinicity values (Δ) in potash felspars of the Akka metamorphics show monoclinic symmetry, not only in orthoclase zone (higher part of amphibolite facies), but also in cordierite zone. Potash felspars in hornfelses close to granite mass seem to show diffuse reflection and large optic angle.
In other metamorphic terrains, potash felspars show extremely low triclinicty values, while those in the Hida gneiss, as well as the Hida granite, show large triclinicity values. From these results, the relations between symmetry change of potash felspar and metamorphism are discussed. From the albite molecular percent in some alkali felspars, the temperature of potash felspar formation is determined by the Barth's method.

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The problem of the stability of reciprocal main axis in polysynthetic twin

Yukio Takano, Kotoyo Takano

1959 Volume 43 Issue 4 Pages 194-202
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.194

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In the course of the crystal analyses of autunite and xanthophyllite several common crystallographical properties, in particular, constancy of reciprocal main axes observed across the stage of crystal transition were found. Similar character were also observed in silicate minerals such as quartz, feldspars and pyroxenes, and in sulfide minerals such as digenite and sphalerite.
Writers discusscd also the relation between twinning axis and reciprocal main axis, and proposed to introduce a conception of reciprocal lattice for clear and accurate descriptions of twinning, especially for those of monoclinic or triclinic crystals.

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On the maghemite in the effluent fume from the open-hearth furnace

Kenzo Ito

1959 Volume 43 Issue 4 Pages 203-207
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.203

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The red iron oxide fume given off by the open-hearth furnace in which pure oxygen was injected into the molten iron to speed up the steel-making reactions was studied mineralogically.
This fume is mainly composed of maghemite, which has a=8.362 A and transforms to hematite at certain temperature between 200°C and 500°C.

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On the igneous activities and the ore deposit at Hamanaka area, Hokkaido

Tetsuo Fujiwara

1959 Volume 43 Issue 4 Pages 208-214
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.208

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The copper deposit of the Hamanaka area is located in the southern part of East Hokkaido. This ore deposit was discovered in the outer zone of Kuril arc, and is considered to be originated by the igneous activies of alkaline basic rocks. It must be a remarkable thing. The geological complex developed in the neighbourhood of this ore deposit are the Hamanaka formation with alkaline rocks of upper Cretaceous and some deposits of Quaternary age. The ore deposit is generally observed as massive or stratified bodies in the alternation member of black mudstone and tuffaceous sandstone, and these ore bodies consist of yellowish massive ore and dark gray Kuroko-like ore. The important minerals are pyrite and chalcopyrite, with minor quantities of sphalerite, galena, marcasite, quartz, and rarely calcite and barite.
After all, this ore deposit is considered to be a cupriferous iron sulfide deposit from its geological situation, occurrence of ore bodies, and its distinctive character of ore. And it is an ore deposit that have been replaced by hydrothermal solutions.

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Study of felsic metamorphic rocks and its associated inclusions which lie in gabbro-diorite at the up-stream of Horoman river, Hidaka piovince, Hokkaido (Appendix)

Especialy on the behaviors of magnetite, pyrrhotite as the accessory minerals of the rocks

Hiroshi Asai

1959 Volume 43 Issue 4 Pages 215-227
Published: August 01, 1959
Released on J-STAGE: August 07, 2008

DOIhttps://doi.org/10.2465/ganko1941.43.215

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The said rocks include scaly magnetite, hematite, pyrrhotite, chalcopyrite, and limonite as the accessory minerals. It is observed that these opaque minerals are deposited from the early to later stage, replacing the biotites. In the basic inclusions of felsic metamorphic rocks or in micro or medium gabbrodiorite, the volume per cent of scaly magnetite and pyrrhotite is higher than in felsic metamorphic rocks.
Chalcopyrite always occurs, but a little in volume Hematite also occurs a little, in felsic metamorphic rocks. Limonite is also formed in some rocks as pseudomorph after pyrrhotite.
At the stage of the scaly magnetite, the clouding and cleaning of plagioclase and crystallization of hornblende, occur instead of forming biotite, accompanying basification of plagioclase, and at the simultaneous or a little later, sulphides are fixed as pyrrhotite or chalcopyrite.
The geologic conditions for forming these rocks are discussed in the present paper.

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