Along the Hidaka mountain range, which constitutes the geological back-bone of the island of Hokkaido, several ore deposits are found closely associated with basic igneous rocks. Shizunai mine described in this paper is an antimony deposit.
Around the mining district extensive schalstein and slate formations trend N 20-30°W; their structure was determineded by tectonic effects similar to those which formed the back-bone region.
The ore deposits are imbedded in a "mineralized sheared zone" which trends N 70°W through a normal diabase mass. The mineralized sheared zone is characterized by altered rocks such as 1) albite-chloritized diabase, 2) chlorite rock, and 3) carbonitized rock. These rock types are-arranged in zones around a stibnite-quartz vein, the core of the deposit. The stibnite-quartz vein is contained only in the carbonitized rock, which constitutes such a characteristic feature for developement of the deposits that the veins and carbonitized rock have long been treated inclusively as "Hinouchi" by Japanese miners.
Carboriitized rock, the main constituent of "Hinouchi" is subdivided as follows:
1) chlorite-carbonate part.
2) carbonate-sericite part.
3) quartz-sericite part.
The quartz-sericite part represents the thin sheath of the ore body; it is surrounded by the carbonate-sericite part which is thicker.
The vein consists chiefly of stibnite and quartz, and diverges into many units about 3m long which are arranged in a "scale-like structure."
Ore minerals are stibnite and a small amount of sphalerite, chalcopyrite, and native gold. Stibnite is in the form of small acicular crystals in low grade ores, but is in columnar aggregates with deformational textures in high grade ores.

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Some data and interpretations are presented to solve the problem on the "bottoming" of sulphur mineralization associated with Cenozoic volcanisms.
Volcanic sulphur deposits are usually found within about 300 meters below the surface of volcanic areas. Among scores of sulphur fields in Japan, no deposit has been found deeper than this. Furthermore, sulphur deposits usually are distributed near what must have been the surface at the time of the mineralization. The main alteration halo of the deposit is usually composed of pyritized, opalized, alunitized and kaolinized rocks. It is to be noted that montniorillonitization is found only in the bottom or in the deeper part of the main halo.
The writer discusses the following two interpretations:
(1) The reason that sulphur deposits are limited to shallow places is that the chemical and sometimes physical properties of the hypdgene mineralizing fluids were changed by contamination by ground water to form a secondary mineralizing fluid. The secondary fluid was mainly responsible for sulphur mineralization and the characteristic alteration.
(2) The juvenile fluid was not strongly acid, while the secondary fluid was strongly acid. The chemical properties and composition of the latter are very similar to those of the volcanic gases or hot waters now being emitted at the surface in solfataric areas.

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In den Nebengesteinen am Rande der "Schwarzerz"-Lagerstätten von der Hanaoka and Hanawa Gruben kann man merkwürdige Zonalverteilung der Tonmineralien beobachten.
Die Verteilung des Silbers in soichen Umgewandelten Zonen ist eingehend bei emissiops-spektrogra-phischer Methode untersucht worden.
Die Anreicherung von Silber in der Nähe von Erzkörpern ist charakterisch.

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Some magnetite veins exist in the pyritic ore bodies in the Yanahara mine. They are several centimeters to several decimeters thick and are composed chiefly of magnetite, calcite, chlorite, biotite and pyrrhotite. The occurrence and paragenesis of the veins suggest formation by reaction between pyrite and a hydrothermal solution which was introduced along fractures in the preexisting pyritic ore bodies. The solution might be the residue of a Cretaceous granite magma.

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During 1955-57, the writer was engaged in a geologic survey of the Amazon Basin, Brazil under the Technical Assistance Program of UNESCO. He was one of 16 members of the FAO-UNESCO Amazon Mission of UN at Belém, Parà. This group helped the SPVEA (Superintendencia do Plano de Valorização Economica da Amazonia) of the Brazilian Government in their economic planning for the development of the Amazon Basin.
Various organizations now engaged in the investigation of mineral resources are as follows:
Organizations:
Federal government:
SPVEA
DNPM (Departamento National da Produção Mineral)
FAO-UNESCO Amazon Mission (UN)
Petróbras (Brazil)
Drill-Ex (USA)
Geophysical Service Inc. (USA)
Schlumberger Co. (USA)
Prakla (W. Germany)
Prospec S/A (Brazil)
Cruzeiro do Sul (Brazil)
Bethlehem Steel Corp. (USA)
Kaiser Aluminum Co. (USA)
Hanna Mining Co. (USA)
Activities:
Aerophotogrammetry, Mineral resources in general Ditto (Araguaia Project)
Mineral resources in general, tropical soils
Drilling for oil
Seismic prospecting
Electrical coring
Seismic prospecting
Aerophotogrammetry, physical prospecting with airborne magnetometer and scintillometer Ditto
Operation of manganese mines
Search for bauxite deposits
Prospecting of iron ore deposits
Mineral deposits of importance which are known in the Amazon are as follows:
Manganese
Iron ore (hematite)
Iron ore (limonite)
Oil
Rock salt & anhydrite
Aluminum phosphate
Bauxite
Rock crystal
Diamond
Tantalite-Columbite
Gold
Residual deposits in pre-Cambrian metamorphic rocks
Iron formation in pre-Cambrian metamorphic rocks
Laterite on diabase
Reservoir in a bed of Mississippian sandstone
Beds in Pennsylvanian series
Phosphatized bauxite
Lateritic bauxite on pre-Cambrian metamorphic and basic igneous rocks
Pegmatites in pre-Cambrian metamorphic rocks
Placer deposits
Geological mapping in the Amazon has been underway since the beginning of this Century so the area is not entirely terra incognita. It is true, however, that the Amazon is still a frontier with vast expanses of virgin forest in interfluves which have never been traversed by geologists or prospectors. Since World War II, the investigations of mineral resources have been conducted by the most modernized field parties equipped with aerial and sub-surface instruments. The Amazon is changing very rapidly.

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