Statistical studies of the clastic sediments of the Shinjo group have been carried out under the same mechanical treatment as in the previous work. In this paper the Masugata and Kawaguchi areas are used as the test areas for investigating the characteristics and the variations of the sediments.
Four types are recognized as the result of the mechanical analysis (median diameter, coefficient of sorting, standard deviation, skewness, and kurtosis). The types Ma and Mb in the Masugata area are practically correlated with the Mitsumori-Sakegawa-Yamuke and Shimizu-Izumikawa formations, and the types Ka and Kb in the Kawaguchi area with the Sakegawa-Yamuke and Shimizu-Izumikawa formations respectively.
At least it is possible to be recognized that the marker bed K₄ between the Yamuke and the Shimizu is found to be the clear indicator in the vertical differentiation also in these areas as shown in the previous discussion.

View full abstract

Under the microscope, skeletal crystals of sphalerite are found in chalcopyrite from the Kawayama, Oya, Ashio and Daira mines. They are belived as due to exsolution of a solid solution. The writers have made thermal studies on skeletal crystals of sphalerite. No change of skeletal crystals of sphalerite in chalcopyrite is found at 4OO°C for 24 hours. At temperatures from 425°C to 450°C for 24 hours, the skeletal crystals are absorbed partly by chalcopyrite, and disappear completely at 480°C for 48 hours (Oya), at 500°C for 24 hours (Kawayama), at 500°C for 48 hours (Daira) and at 515°C for 24 hours (Ashio). The solid solutions of chalcopyrite and sphalerite, obtained by heating at temperatures from 475°C to 530°C, show slightly the unmixing process at various constant temperatures from 200°C to 400°C for 24 hours. The sphalerite, then, appears in fine worm-like, drop-shaped or skeletal crystals.

View full abstract

The writer describes the petrographical chracters of the plagioclase garnet hypersthene hornblende rock found as a block on the River Horobetsu, Hidaka prov. and gives some considerations on its genesis.

View full abstract

In the Sanbagawa metamorphic region of the Tenryu river basin, the basic and ultrabasic intrusion can be divided into the following three stages.
1 st stage: The synkinematic intrusion of sills of “Topfstein” and epidote-amphibolite. The later was derived from a basic intrusive rock. Accompanying the intrusion of these rock, the crystalline schist were subjeoted to metasomatisms which were formed of the albitization and the chloritization.
2 nd stage: The intrusion of saussurite gabbro, periodtite, metadiabase and amphibolite. The latest was derived from basic and ultrabasic rocks. In the last of this stage, the banded rock, is composed of the peridotite and the saussurite gabbro, intruded into the space (Mikabu Zone) between the crystalline schist and the non-metamorphic palaeozoic rock.
3 rd stage: The intrusion of the serpentin was accompanied by the fault.

View full abstract

Spinel-bearing inclusions are found in the quartzporphyritic rocks near Osuzuyama.
These inclusions show zonal structure: the core, a large crystal of sillimanite; the next outer zone, aggregate of fine spinel grains; the outermost zone, aggregate of rather large plagioclase crystals.
About the genesis of spinel, the writer prefers metamorphic differentiation taken place in the inclusion, rather than interaction between magma and the inclusion.
The distribution of spinel bearing-inclusions in igneous rocks, in Japan, except basic rocks, bears some relation to underlying base rocks.

View full abstract