At least 14 1/2 million square miles of the ocean floor, according to recent discoveries, are strewn over with nuggets of valuable minerals. Typically shaped like potatoes, ranging from a pigeon's egg to a football in size these brown and black lumps of light porous rock are called manganese nodules.
The lumps of rock average 20 percent manganese, 15 percent iron, and half a percent eack of cobalt, nickel and cooper, respectively. The nodules covering a single square mile hold \18×10⁷ worth of metals.
Mining of the more easily accessible nodules may be soon under way. John L. Mero of University of California declares, "a commercial venture may now be possible" where the depth is within 4, 000 feet.

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Two normal faults of Akenobe and Miyamoto are significant on the geologic structure as well as the structural control of ore deposits in the Akenobe mine. The Akenobe group may be divided into the following formations in descending order:
Formation
Narabe f.
Fujiidani f.
Daisen f.
Thickness
800m+
700m+
800m+
The Ryusei and Fudono veins in the southern part, and the western part of the area, has been recently developed. The former is a cassiterite-chalcopyrite vein, and the latter an excellent zinc-blende-chalcopyrite vein.
On the basis of Sn distribution which indicates the last stage of mineralization, the followings are recognized :
(1) The source of ascending Sn solution appears to be identical with a crater of intrusive diorite.
(2) The ascending Sn solution branches off along the direction of diorite intrusion and along thee hanging wall.
(3) As a whole, the veins become a wider and higher grade bonanza in the sedimentary rocks rather than in the diorite.
The intrusive diorite is a important key in prospecting.

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The Tsumo mine, one of the pyrometasomatic deposits, is in the inner zone of south-western Japan.
The geology in the vicinity of the mine consists of palaeozoic sediments and late Cretaceous or early Tertiary igneous rocks. The Palaeozoic formations consist of slate, sandstone, quartzite, limestone, etc. They have complex geologic structures by foldings and faultings. The igneous rocks are granite-porphyry, quartz-porphyry, guartz-diorite, granite, porphyrite, etc. The ore deposits were formed by replacement of the calcareous or limestone beds, which are intercalated 'side by side within the quartzite bed, with such skarns as banded skarn, wollastonite skarn, brown garnet skarn, green skarn, diopside skarn, phlogopite skarn, etc. The ore minerals are pyrrhotite, chalcopyrite, sphalerite, magnetite, galena, gold and silver, etc.
The ore deposition was controlled by the following geologic factors : (1) presence of calcareous beds (especially, of the banded or transitional facies), (2) saddles of foldings, (3) cross foldings, (4) presence of fissures and quartz-porphyry dykes.
Geologic history of the ore deposition may be given as follows : (1) sedimentation of the Permo-Carboniferous rocks, (2) primary foldings (formation of the anticlinorium with the NE-SW trend), (3) secondary folding with the NW trend and faultings, (4) successive faultings with igneous activities of the following order : granite-porphyry→quartz-porphyry→quartz-diorite→granite, (5) post igneous skarnization and mineralization, (6) faultings, (7) after cessation of faultings, intrusion of porphyrite dykes.

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The Huanzala Mine, in the District of Huallanca, Department of Huanuco, Peru, has been explored by the Mitsui Mining & Smelting Co., Ltd. since 1964 by surface/underground diamond drilling and also tunnel-drifting. The Mine will be in operation in April 1968.
The ore deposits are of a Zn-Pb-Cu mesothermal metasomatic type mainly replacing the Jurrasic limestone formations. The ore-bodies were controlled by deformation of the limestone beds due to some group of thrust faults cutting the limestone beds at low angles, They have a clear zonal distribution of pyrite, Cu, Zn and Pb from the center onward.
The center of mineralization and the ore solution passages are apparently two main sheared breccia zones of high pyritization, along the quartz porphyry dike. High-grade Zn-Pb ore bodies are formed around the breccia zones.
Field data suggest a certain relationship between the mineralization and the quartz porphyry dikes, although it may be indirect.

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Renewed exploration of the old copper prospect in Whitehorse, Yukon Territory, by field studies, geophysical prospecting and diamond drilling, had led to finding and evaluation of significantly workable ore reserves. The mining operations and shipping activities by the New Imperial Mines Ltd. were opened at the end of 1966.
The ore deposits are of a pyrometasomatic copper deposit type with several kinds of contact-metamorphic silicates. Bornite and chalcopyrite are the principal copper sulphides in most of the deposits, while valleriite is found locally.
Mineralization is in both Triassic limestone and adjoining granitic rocks. There are two distinct. classes of skarn ore bodies as listed below.
(1) Copper sulphides associated with magnetite or magnetite and hematite.
(2) Copper sulphides associated with contact metamorphic silicate minerals.
The former prevails in the central part of the "Copper Belt", while the latter lies in the northernand southernmost parts.
Some diagnostic characters of the deposits are as follows:
(1) Bornite and chalcopyrite are commonly disseminated throughout silicate-and iron-rich skarns while, pyrite is found in relatively small amounts.
(2) The existence of valleriite, cubanite and scheelite suggests that some deposits are formed at fairly high temperatures.
(3) In general, skarn minerals in this "Copper Belt" are of high magnesian content, compared with similar ore deposits in Japan.
(4) A Keewenaw ore deposit resembles the "porphyry copper" type deposit, although its scale is small.

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Kosaka is one of the typical so-called "black ore type" deposits in Miocene greentuff formations. In this mining district, the Motoyama and Uchinotai deposits, which consist of black, yellow, and siliceous ores and gypsum, are well known.
Recently from 1962 to 1966 the Uwamuki deposits of four isolated ore bodies were explored at about 300 to 600 meters southeast of the Uchinotai. These ore bodies are distributing from nortn to south.
Geologically, they were ore beds in a tuff-breccia formation, with the footwall of sericitized white rhyolite. These country rocks are called the Uwamuki-formation. of the Miocene age.
The Uwamuki deposits consist of three kinds of ores, namely, black, siliceous and gypsum ores. On the other hand, yellow ores are absent. The black ores can be classified into two types; the "compact type" of mainly massive sphalerite, galena and barite, and the "disseminated type" of sphalerite and galena in brecciated rock matrices.
The siliceous ores, which are commonly found below the black ores, were formed in brecciated white rhyolite and explosion breccia of rhyolite. Sphalerite, galena, barite, and quartz are the interstitial minerals in the cracks or matrices of the rocks.
A high content of silver in the compact type black ore is notably characteristic. The silver content ranges from several hundred to thousand grams per ton of the ore. Evidently, it has remarkably sympathetic correlation with the amount of tetrahedrite, as revealed by the microscopical observation and chemical assay.
Characteristic differences between the two deposits, Uchinotai and Uwamuki, are the absence of yellow-ore masses, the rare occurrence of chalcopyrite and pyrite, and the important presence of tetrahedrite in the Uwamuki ore deposits. The mineral assemblages of siliceous ores of the Uwamuki show distinct, differences from those of the Uchinotai, in which the presence of chalcopyrite and pyrite is common.
The development of the Uwamuki deposits is now in progress by sinking a vertical shaft and driving underground drifts. They are expected to become a important producer of silver, zinc and lead in near future.

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Recently, a number of extensive Kuroko deposits have been discovered in the Hokuroku district. Most of them are covered deposits which lie within a certain horizon.
On exploration for a new deposit of this type which may be far from the known ore body, we may use the natural radio-active anomaly as one of prospecting methods.
According to the recent investigation in the Hokuroku district, it has been confirmed that the natural radio-active anomaly is closely related with the Kuroko deposit. Hence, it can be used as one of reliable methods for locating the ore horizon and for estimating the extent of mineralization.

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