Ore deposits of the Ôe mine are of epithermal fissure-filling vein type, ore of which consists mainly of rhodochrocite, sphalerite, galena, chalcopyrite and pyrite with small amount of native gold and silver minerals.
On the basis of the alteration mineral assemblages, the alteration halo of the mineralization may be divided into the following four types inwardly from the halo rim.
(I) Albite-chlorite-(sericite)-(calcite)
(II) Chlorite-(sericite)-(quartz)
(III) Sericite-(quartz)-(chlorite)-(kaolin)
(IV) Quartz-sericite-(kaolin)
It is one of the most important problems for the mining geologist to delimit the exploration target by paying attention to the alteration halo.
In this meaning, the alteration type (III) and (IV), which are closely associated with the metallic mineralization, are quite noticeable. The type (III) having relatively wide distribution in contrast to the type (IV) can be the exploration target.
Rocks in the type (III) are easily distinguished from others by their brittleness which is correlated with the RQD (Rock Quality Designation) value. RQD data on logging the drill core are thus found to be very useful to delimit the exploration target in this mining area.

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The Akenobe deposit has been cited as one of the best-known examples of the xenothermal tin-bearing polymetallic vein-type mineralization. It occurs in a formation of slate, basic tuff and basic lava of middle to late Permian Maizuru group as well as Yakuno basic complexes. Detailed examination on the distribution of metals in each vein and the entire mineralization field revealed that the mineralization is roughly divided into three groups; Cu-Zn type, Cu-Sn type and Cu-Zn-Sn type and that a positive correlation exists between zonal arrangement of ores and type of mineralization. In general, Cu-Sn type is dominant in the central portion of the mining field, mainly along NE-SW trending major faults. On the other hand, Cu-Zn type is distributed in the outer zone, especially in the northwestern and southeastern areas.
The Chiemon vein swarm and Ginsei vein both belong to Cu-Zn-Sn type, although they are quite different each other in their metal zoning patterns. The former is composed of Cu-Zn and Cu-Sn type mineralizations which occurred with a considerable tectonic gap, while the latter seems to have been a product of more or less continuous ascending of ore solutions with copper, zinc and tin.
Taking into consideration the mineral zoning patterns and results of stress field analysis, it is concluded that the Chiemon vein swarm has been formed under NW-SE trending compressional stress and the No. 3 fault has served as channelways for ascending ore solutions. Recent exploration works based on these conclusions seem to be quite successful.

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The newly discovered Ezuri kuroko deposits are located in the southwestern part of Hokuroku area in Akita Prefecture, Japan. Detailed geological study on the stratigraphy of acidic volcanic activities in the Fukazawa-Ezuri district had indicated possible existence of the kuroko-bearing formation in this particular area. As a result of a few drillings, favourably altered acidic volcanic rocks were encountered and a systematic exploration program started which included geochemical examination of the behavior of alkali and alkaline earth metals in pre-mineralization acidic volcanic lavas, geophysical survey (time domain IP method), magnetic susceptibility measurement, and systematic grid drillings.
In May 1975, the Iwagami deposit and in July 1976 the Ezuri deposit were discovered. The Ezuri mine comprising these deposits, now has possible or reserved ore of about 3 million tons with a grade of 0.89% Cu, 3.3% Pb, 10.1 % Zn. Since October 1979, the mine has been in operation on a scale of 7, 500 tons per mounth.
The geology of the area is characterized by an intensive volcanic activity. Pyroclastic rocks, lavas and intrusive rocks of the Nishikurosawa and Onnagawa stages of the Miocene age are the major constituents. These are subdivided into three units, Yukisawa, Kagoya, and Shigenai formations in the ascending order, which can be correlated with the stratigraphic column in the nearby Fukazawa area. The orebodies occur at the top of dacitic volcanics of Yukisawa formation and is overlain by a sheet like porphyritic dacite and in turn by basic tuff. Each orebody is mainly composed of stratiform black ores accompanied with minor amount of yellow ores, dissemi-nated or stockwork ores and gypsum ores.

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[in Japanese]

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The Huanzala mine is a copper, lead and zinc deposit in Peruvian Andes. Being emplaced in a limestone formation of Cretaceous age, the orebodies are bedded or lenticular in form and occur in limited horizons. A few sheets of quartz porphyry exist close to the ore horizons.
Ore deposit of the Huanzala mine is considered to be a product of skarnization and succeeding hydrothermal replacement processes related to the activity of the quartz porphyry. On the basis of their mode of occurrence and mineral assemblage, Pb-Zn ores are divided into three types; pyritic ore, skarn ore and "shiroji" ore (argillized ore). "Shiroji" ore is a hydrothermal alteration product of pyritic and skarn ores. Cu ores are also divided into three types; pyritic, "shiroji" and vein-like. Main Cu minerals of each of the three ore types are chalcopyrite, bornite+chalcopyrite, and tennantite, respectively.
In the Huanzala mine, two types of sphalerite are recognized. One is the iron-rich type, called "red sphalerite" because of its reddish and/or brownish color, occurring in the pyritic and skarn ores. The other is the iron-poor type, called "black sphalerite", which is microscopically black due to the numerous small dots of chalcopyrite inclusion. This type of sphalerite is generally accompanied by "shiroji" ore. Microscopic examination indicates that the "red sphalerite" has formed earlier than the "black sphalerite".
The sequence of the mineralization in the Huanzala deposit is considered to be as follows; pyritization nearly simultaneous with quartz porphyry intrusion→skarnization and "red sphalerite" mineralization→galena mineralization followed by chalcopyrite mineralization→"shiroji" alteration and "black sphalerite" mineralization→bornite+chalcocite mineralization→tennantite mineralization.
Although the pattern is not very simple, zonal distributions of elements and ores which can be related to the paragenetic sequence are distinct in the deposit. Systematic analysis of these data is very useful for an exploration guide and some encouraging results have already been obtained.

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Ore-prospecting and engineering geological survey have so many common grounds as to their technique and object that the two fields should cooperate more closely. Among the techniques and knowledges employed in the engineering geological survey, the following may be of particular importance to ore-prospecting, that is, seismic survey, numerical analysis of fault-and fracture-systems based on rock mechanics, knowledge of rock mass classification and groundwater hydrology. On the contrary, application of the ore-prospecting techniques to engineering geological survey may be most useful in surface and underground geological survey, geophysical and geochemical surveys, drilling, etc. Because of the growing trend of larger scale civil engineering construction these days, underground geologic data such as those required in mining geology are becoming more and more important in engineering geological survey. In view of the close relationship between the above two fields of the applied geology, it is desirable for young geologists working in either field to have experience of the counter field as much as possible.

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