Ani mine, situated in the so-called Green Tuff belt of Northeast Japan, is vein-type copper mine. On the basis of studies of geologic structure, mode of occurrence of ores and results of induced polarization, blind ore deposits have been found at the Inari Adit area. Procedures of the successful prospecting were described in this paper.
Important guidelines through the prospecting works are as follows:
1) Nature and shape of basaltic rocks. Copper bonanzas in these veins are found at extensions of sheet and dike of the basaltic rocks in some occasions.
2) Frequency effect anomalies to indicate areas of mineralization and hydrothermal alteration.
3) Resistivity values to indicate shape of trachy-andesite. A funnel shape was figured out on the trachy-andesite with the resistivity analyses. Well fractured zone was presumed at the margin of this intrusive body; then some veins were found.
Procedures above mentioned and later exploratory adit works were able to detect several new copper veins at depth of the Inari Adit area, where un-mineralized lava flows of trachyandesite and dacite crop out.

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Exploration works at the Huanzala Mine in the district of Huallanca, Province of. Huanuco, Peru was commenced in May, 1964 by Mitsui Mining & Smelting Co., Ltd. Then, detailed geological mappings, surface and underground diamond drillings and tunnel drivings have been carried out. The mine has come into operation since April, 1968.
Ore deposits are composed chiefly of sphalerite, galena, chalcopyrite and pyrite, and accompanied by accessory minerals such as bornite, covellite, tennantite, etc., and gangue minerals such as calcite, quartz, fluorite, chlorite, micas, etc.
As a result of the above-mentioned exploration works, the following geological features have been clarified;
1) The country rock is an alternation of limestone and shale, that is, the so-called Huanzala Ore Formation of Mesozoic age. It must be noted that the most favorable bed for mineral deposition is a finely banded alternation of limestone and shale. Also a characteristic feature is the strati-bound development of ore bodies in the shape of lens, vein or irregular mass. Such mineralization is continuously found for kilometers in the Huanzala Ore Formation whose thickness is about 180 meters.
2) Several dykes of quartz porphyry intrude along the bedding planes of the Huanzala Ore Formation. Though they are weakly mineralized, it is not clear whether the igneous activity is directly related with the mineralization.
3) Highly pyritized zones are formed in parallel with the Pb-Zn-Cu ore zones. The zonal distribution of ore minerals can be often locally observed arround the highly pyritized zone. However, regional feature of the zonal distribution can not be recognized for the time being.
As there are still many geological problems to be solved, the afore-mentioned features may suggest an important key to promote more exploration works.

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The Kamiokkope mine is one of the important limestone mines in Hokkaido. The production was begun in 1934. This mine consists of Migiyama, Hidariyama and Hommanosawa orebodies, all of which belong to the Kamui horizon of Jurassic Hidaka Group. These orebodies occur as irregular layer, lens or at some places massive body.
The Migiyama orebody is the first operated one and has been almost mined out. The Hidariyama orebody is the second, initiated in 1941. Recently a very hard part that is unsuitable for mining was discovered at the lower part of the orebody. It is now under investigation by drilling. The writer has collected various samples from this hard part and compared them with the other normal limestone.
Almost all of limestone at this mine show strong recrystallization texture; while recrystallization of the lower part is much stronger than the others. This was previously thought cause of the hardening. Field and microscopic observations indicate evidences of severe crushing at the lower part besides recrystallization, namely many sliding planes observed in field and crushed textures under the microscope. Recrystallization may not be only reason for the hardening.
Unsoluble residue test for rocks from the lower part revealed existence of abundant silica material. Electron microscopic observation also supports this result. No.13 specimen looks entirely pure limestone by naked eyes, yet it belongs to the hard type. Abundant microscopic chert was found in the matrix of the specimen. Very fine particles of chert or cherty sandstone seem to be the main reason for the hardening of limestone at the lower part of Hidariyama orebody.

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Before conducting information and outline drilling on a porphyry copper deposit, it is most advisable that the grade of copper of the target may be previously estimated by detailed geochemical study on soil sampling. To illustrate how this estimation may be carried out, geochemical data and copper contents of three porphyry copper deposits in tropical terrain, St. Niño (Philippines), Nungkok (Malaysia) and Chaucha (Equador), are compared.
1) St. Niño: The topography is very steep with very thin overburden. There are distinct dry and wet season. The average of T-Cu, Cx-Cu, Cx-Cu/T-Cu and copper content of drill cores in ore zone are 3, 048 ppm, 16.8 ppm, 0.55 percent and 0.477 percent respectively. Thus the copper content in ore body is 1.6 times the T-Cu in the soil.
2) Nungkok: The topography is also very steep. There are heavy rains all the year round in this area. The average of T-Cu, Cx-Cu, Cx-Cu/T-Cu and copper content of drill cores in the northern and southern ore zones are 2, 031 ppm, 181 ppm, 14 percent, and 0.344 percent respectively. Thus the copper content of the ore zone is 1.7 times the T-Cu in the soil.
3) Chaucha: The deposit is located about 1, 700 m above the sea level and the climate is relatively warm. The dry season starts at the middle of May and ends at the middle of October. The total rain fall in the wet season is around 1, 300 mm. The deposit is covered by the very thick overburden. The geochemical data and their relation to the drill core assay are as follows:
Therefore, the ratio of Cx-Cu/T-Cu may be one of the important factors affecting the calculation of ore grade, and this ratio may be influenced by thickness of overburden. According to the ratio of Cx-Cu/T-Cu, the copper content of ore boby will be from 1.5 to 3 times the total copper value in the soil above the ore body.

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