Photogeology in Japan has been considered to be very difficult, because, bf small geological units, complicated geological structures, thick surface soil, and artificial forests in the fields. Overcoming these difficulties, however, photogeology has been utilized in the various fields, particularly in the oil fields and limestone areas.
The writers attempted to establish a photogeological standard in the Kamaishi Fe-Cu mining area where Paleozoic sedimentary rocks and Cretaceous igneous rocks (plutonic and hypabyssal) are distributed. They expected to apply it to the exploration of metal mining to get some geological data which was not clear in the previous conventional survey.
From observation of mosaic and stereography of air photographs, using such elements for interpretation as drainage patterns, drainage anomalies, sink holes, mountain ridges, phototonalities, grain textures and fracture patterns, the writers identified igneous rocks and sedimentary rocks, and classified each rock facies as follows:
1) Most of dendritic drainage patterns develop in the area of sedimentary rocks, while parallel or sub-parallel drainages are found in the area of igneous rocks.
2) Drainage anomalies showing anticlines and synclines exist in the areas of sedimentary rocks.
3) Limestones and slates can be identified by the presence of grain texture, phototonality and sink holes.
4) Ganidake granodiorite and porphyrite can be identified by the features of grain texture, photo-tonality and difference of fracture pattern.
5) Tono granodiorite shows typical granitic topography and can be distinguished from other rock facies.
6) In the areas influenced by mineralization, drainage pattern is dendritic, but fracture pattern shows the characteristic of igneous rocks.
7) Anomaly of stream and various kinds of fault topographies were very effective in finding out or in pursuing faults.

View full abstract

Mae La Noi Mine, located about 110 km west-southwest of Chieng Mai City in the northern Thailand, produces fluorite concentrates for metallurgical use.
The ore deposits occur as dissemination, net-work veins, replacement, and veins in a large measure in limestones of probably Ordovician age interbedded with sandy shales, and are grouped from their shape into 3 types: massive type, bedded type, and independent vein.
Geologically the area in operation at present is divided into 3 portions, each of which is characterized by different type of ore deposit due for the most part to structural control.
Disseminated ores forming major part of large-scale massive type deposits consist of porous and siliceous materials with mottled colors, and are, therefore, easily distinguished from products of any other mine in Thailand. In addition, some fine-banded ores are found mostly in bedded type deposits. The ores of this kind, quite similar to shale in appearance, are assumed to have replaced part of platy limestones.
While the present area is not so favorable for new ore-finding, an area to the north seems to warrant, from structural point of view, further exploration for large-scale massive type deposits.

View full abstract

Weathered granitic rocks were classified into five layers according to their occurrences and the degree of weathering at Iizuka, Kyuragi and Yasu in the northern part of Kyushu Island. The writers investigated chemical component, mineral constituents, degree of liberation of mineral particles, particle size distribution and porosity of these weathered granitic rocks. The results obtained are summarized as follows :
1) The total H₂O, porosity (bulk density) and particle size distribution can be used as properties to indicate the degree of weathering.
2) Owing to the difference of stability of the individual constituents against weathering, there is a concentration trend of the constituents according to the particle size. As weathering proceeds, plagioclase disappears most rapidly among the main rock-forming minerals, though potash feldspar which is more desirable for ceramics than plagioclase remains even in the extremely weathered layers. Kaoline clay is present in a range of fine paticle size.
3) Degree of liberation of mineral particles increases gradually as the particle size becomes finer and weathering proceeds. And almost all particles are liberated into each mineral in a range of particle size finer than 0.25 -0.4 mm.
4) The weathered and decomposed granitic rocks except the surface layer may be used as industrial materials. Especially, it is able to produce ceramic clay from the extremely weathered but not contaminated layers through scrubbing and sizing of it, and also able to obtain the aggregate for construction in good yield from the decomposed granitic rock at the early stage.
5) The most useful kind of granitic rocks as industrial mineral resources is the one that is rich in quartz and potash feldspar, such as Sawara, Saga, Kaho and Masaki granites in the northern parts of Kyushu Island.

View full abstract

The Arabian shield of Saudi Arabia is mainly composed of granite, gneiss and volcanic rocks, age of which ranges from about 1000 to 500 m.y. These rocks are separated by two distinct tectonic lines, the Najd fault system and the Yemen fault system, that trend NW-SE direction and are 300 km apart (Fig. 1). Separated blocks are tentatively called, from north to south, the Northern block, the Central block and the Yemen block. Each of these large blocks consists of many various sized tectonic basins or blocks, which are controlled by NW-SE trending faults and subsidiary N-S or NE-SW trending faults.
Copper-zinc-lead mineralizations associated with mainly acidic volcanisms are found in the Halaban group or Jiddah formation. There are some indications that the volcanic rocks are formed under submarine condition. Sulfide minerals occur in the manner of massive, stratabound, network, vein and dissemination.
The mineralized area are located nearly at the boundary of individual blocks or intersections of tectonic elements. It seems likely that the submarine volcanisms took place along the boundaries between the uplifted and subsided blocks.
We have enough background for such tectono-volcanic environment in the Japanese green tuff region. The geologic structures in the Arabian shield are quite similar to those of the green tuff region, and environment of the mineralizations resembles that of Kuroko-type mineralization. The Precambrian base metal mineralization in the Arabian-African shield region may need some re-examinations with knowledge on geology in the green tuff region in Japan.

View full abstract