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Volume 43, Issue 1
Displaying 1-6 of 6 articles from this issue
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Kazuo Miyagi1959 Volume 43 Issue 1 Pages 1-6
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe so-called trachytic rocks developed in the lower parts of the green tuffs in the Oga peninsula are divided into three members. The basal member is the altered fine grained trachytic lava, and it is successively overlain by the altered hornblende trachytic lava and its tuff, the altered biotite trachytic lava breccia and its agglomerate and tuff.
As the results of microscopical and chemical studies, these rocks can be recognized as the intermediate type between the calc-alkaline and the alkaline-rocks. Some detailed petrographic descriptions and considerations are given in this paper.View full abstractDownload PDF (282K) -
Tadashi Konda1959 Volume 43 Issue 1 Pages 7-14
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSThe numerous dolerites of various types are seen on the Dewa Hills, Northern Honshû. They are the Hirataki, Hatamura, and Nakada types, being lithologically olivine dolerite, hypersthene dolerite with olivine and hypersthene dolerite without olivine respectively.
The hypersthene in the Hirataki dolerite is found in the pyroxene-rich layer in the lower part of the si1l due to the gravitational differentiation, while the hypersthene in the Hatamura and Nakada types is included throughout the whole mass.
The writer has examined the genesis of hypersthene dolerite on the basis of the micrometrical and chemical analysis, concerning the pyroxene rich layer of the differentiated products. It is concluded that the hypersthene dolerite is not derived from the same process as is seen in the Hirataki dolerite due to the gravitational differentiation, but characterized by an increase of SiO2 and A12O3 as well as a decrease of MgO.View full abstractDownload PDF (491K) -
Noboru Oba, Hideo Ishikawa1959 Volume 43 Issue 1 Pages 15-25
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSOrbicular rocks which are characterized by tourmaline were found from the central part of the Takakuma granite mass in the Osumi peninsula, Kagoshima Prefecture. The mode of occurrences, microscopic features, optical properties, twin types of plagioclase, volume ratios of the constituent minerals, estimated chemical composition from mode, and trace elements are given.
It is concluded that the formation of the rocks related to the greisenization and concentration of the boron-rich volatile towards the central part of the granite mass during the deuteric stage of the magmatic cooling.View full abstractDownload PDF (1411K) -
Hiroshi Asai1959 Volume 43 Issue 1 Pages 26-35
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSAt the up-stream of the Horoman river, Hidaka province, felsic metamorphic rocks which are mainly composed of biotite hornfels, biotite migmatite, tonalitic migmatite and coarse biotite diorite are enclosed in gabbro-diorite on a small scale.
The biotite hornfels is not homogeneous and has clots of plagioclase-biotite rock with sub-glomeroporphylitic texture of biotite. In biotite and tonalite migmatites, the sub-igneous textures are recognized, and in their inclusions such as plagioclase-biotite or plagioclase-hornblende rocks the sub-diabase texture are also observed.
The migmatites, coarse biotite diorite, and their inclusions are considered to be the products of the metamorphism which differentiated from biotite hornfelsic rocks in the early and middle stages of the mechanical movement.
The gabbro-diorite has the relict texture of the migmatite and it seems that the gabbro-diorite was intruded before the stage of the migmatization.
No contact effects are found between the felsic metamorphic rock and the gabbro-diorite.View full abstractDownload PDF (682K) -
Mamoru Suzuki, Sumitoshi Sakô, Kôhei Matsui1959 Volume 43 Issue 1 Pages 36-41
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSIn the environs of the south-western Shimofurano, the western end of the Yubari mountains in the Kamuikotan tectonic zone, a small area of hornfels has recently been found, though it has been considered as the characteristic area of the low grade metamorphosed schist.
Around the said area, the pre-Cretaceous and overlying lower or middle Cretaceous formations are disposed with N-S trend. Cutting these Cretaceous shales, many trondhjemite dikes are found with the prominent feature in this zone. It is conclude that the hornfels is closely related to the intrusion of the trondhjemite dikes.View full abstractDownload PDF (809K) -
Studies on the chromites and their occurrences in the Tari district, Tottori Prefecture (3rd report)Jun-ichi Kitahara1959 Volume 43 Issue 1 Pages 42-54
Published: February 01, 1959
Released on J-STAGE: August 07, 2008
JOURNAL FREE ACCESSDykes of dioritic, leucocratic and bastitic rocks, and vein of diopside cut across the ultra-basic rock in the region. Since the diorite dykes cut chromite bodies it is considered that the chromites was originated in a magmatic cycle. The diorite dykes and dyke form inclusion are composed of fine grained plagioclase, hornblende or pargasite, and magnetite or ilmenite as accessory mineral. The leucocratic rocks are mainly composed of quartz and plagioclase. It is supposed that pyrosenite was altered to the bastitic rock by action of later magmatic water. The rock is white with faint greenish tint.
Clinochlore occurring as a secondary mineral in the ultra-basic rock, was derived from aluminous enstatite by the contact metamorphism. The clinochlore crystal contains small amounts of chromic oxide. The melanite was presumably formed by chemical reaction between chromite and the adjacent pyroxene or olivine owing to the contact metamorphism of ultra-basic rock. The melanite is black grossularite-andradite containing 3.11% Cr2O3.
Many calcite veins of hydrothermal origin filled up along various cracks and openings of the ultra-basic rock and chromite body in the said region. Some of these veins include remnants of massive chromite and serpentinite.View full abstractDownload PDF (1597K)
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