The Hosokura Mine is situated 84 km north of the Sendai City, Miyagi Prefecture. The area is located geologically at the eastern margin of so-called "green tuff region" in Northeast Japan. The ore deposits of this mine are lead-zinc fissure filling veins of epithermal or mesothermal type.
In this paper, geological features of fissure systems and ore shoots of Oiwake veins located at the northwestern margin of the Hosokura Mine are described. They are summarized as follows ;
(1) The geology of this area consists of massive propylite, brecciated propylite, tuff breccia or sandy tuff (Hosokura lower formation) and tuff breccia, pumiceous or sandy tuff (Hosokura upper formation) in ascending order.
(2) Two fissure systems, NW-SE and NE-SW are developed in the area. The NE-SW fissure system forms the Oiwake veins reported in this paper.
(3) Ore shoots of the Oiwake veins are developed along a major fault, Hanzashinpi fault. Several notable ore shoots are recognized at the uppermost part of Hosokura lower forma-tion as well.
It is considered that the exploration plannings for Oiwake area in the future should be based on the facts mentioned above.

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The Kamaishi Mine is one of the major producers of copper-iron ores of skarn type in Japan. In this paper the geological structure of the Kamaishi mining district is described.
The Kamaishi mining district is located in the Southern Kitakami terrain with abundant limestone near the boundary to the Northern Kitakami terrain with abundant chert. The district is covered by Paleozoic and Mesozoic formations intruded by igneous rocks of Early Cretaceous.
The geological structure of the Paleozoic formations is characterized by a large anticlinolium trending N-S. The deformed Paleozoic formations are covered unconformably by Mesozoic Maginouchi Formation and Ganidake igneous complex is emplaced into the axial part of the anticlinolium. At a stage between the deposition of Maginouchi Formation and the intrusion of Ganidake igneous complex, fault movement occurred resulting in the separation of the area into several geological blocks. Eastern wing of the anticlinolium was displaced downward several hundred meters from the western wing by Nakanosawa fault.
The ore deposits are formed at the neighborhood of the contact of Paleozoic limestone and Ganidake igneous complex. The igneous complex consists of Ganidake granodiorite, diorite, diorite porphyry, gabbro and monzonite. The diorite porphyry is intruded along thrusts and faults providing with favourable condition for skarnization and metallic mineralization of the western orebodies of the Kamaishi deposits. "Sennin porphyrite" which has been considered as a member of Ganidake igneous complex was ascertained to be pyroclastics of Carboniferous Tsuchikura Formation. After the intrusion of the Ganidake igneous complex Kurihashi granodiorite was emplaced. Ganidake granodiorite body swells downward while Kurihashi granodiorite body pinches in the depth. This suggests that the former is exposed in its upper level while the latter is deeply eroded.

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Modes of acidic volcanic activity preceding kuroko deposition provide with a clue for prospecting targets of kuroko deposits. Nature of acidic volcanism was made clear in the area of Fukasawa kuroko deposits, Hokuroku district. Chemical analyses of underlying volcanics were also made. The results of this study are summarized below.
(1) The Neogene Yukisawa dacite lavas in the Fukasawa area should be classified into 4 types, D1 lava dome, D2 lava flow, D3 lava flow, and D4 lava dome.
(2) The Fukasawa kuroko deposits were formed in connection with the activity of the Fukasawa D4 lava dome.
(3) Chemical analyses of 628 core samples of the Fukasawa D4 lava dome revealed a distinct distribution pattern of Na, K, Ca, Mg, Cu, Pb, Zn, Fe, and Mn making haloes around the orebodies.
The effective delineation of prospecting targets may be done based on these geological features.

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The Gunpowder Mine is located in North Western Queensland, Australia and has been developed by underground trackless method in a joint venture form of Consolidated Gold Fields Australia and Mitsubishi Group since October, 1971.
To date the mine has produced about one million tons of ore containing 2.8 percent copper, all of which have been shipped to Japan as copper concentrates.
The area around the mine is underlain by Lower Proterozoic sedimentary rocks; Eastern Creek Volcanics, Myally Beds, Gunpowder Creek Formation and Paradise Creek Formation.
Gunpowder Mine consists of three major deposits; Mammoth deposit, Esperanza deposit and Mount Oxide deposit. The host rocks of these deposits are quartzite and sandstone of Myally Beds (Mammoth), siltstone and shale of Gunpowder Creek Formation (Mount Oxide) and chert and siltstone of Paradise Creek Formation (Esperanza).
Mammoth deposit is now under production and the mine is subdivided into three major orebodies as No.1, No.2 and No.3 orebody.
Ore reserves of the Gunpowder Mine have successfully been increased to 10 million tons with an average grade of more than 3 percent copper after three years' integrated explora-tion work by Gold Fields and Mitsubishi.
The Mammoth ores are mainly composed of chalcocite, bornite, pyrite and chalcopyrite. Oxidation has taken place to 100 meters below surface and chalcocite occurs as deeply as 500 meters below surface. The mineralization should be more studied in relation to regional geological setting, structure including local faulting and brecciation and supergene process.

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The Chapi Mine is one of medium size copper mine in Peru and is located in the Polobaya District, Arequipa Prefecture, Southern Peru.
Geology in the area is composed of andesite lavas of the Lower Jurassic period and marine sediments of the Upper Jurassic period, being intruded by stocks and dykes of acidic igneous rocks of the Lower to Middle Tertiary period.
In the mine area there are two huge faults with NW-SE trend, Chapi fault and America fault. The Chapi ore deposits are of the Manto type and occur mainly within sandstone beds of the D formation of the Chapi Group distributed between the two faults. The mineralization of the porphyry copper type is recognized in the northern side of the Chapi fault where the acidic igneous rocks are dominated and fissure-filling veins are scattered throughout the area.
The occurrence of the Chapi ore deposits is restricted in sedimentary beds, and the deposits are composed of the leached-out zone, secondary enrichment zone and primary sulfide ore zone from the upper side to the lower. Major ore minerals in the secondary enrichment zone are digenite and pyrite and a small quantity of chalcopyrite, bornite, covellin etc. is also contained.

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A hidden porphyry copper deposit of primary ore has been discovered in Andes Mountains, southern Peru. The exploration works were initiated by aeromagnetic survey and interpretation of colored aerial photo followed by detailed geological mapping combined with geoche-mical and I.P. surveys. Thus Quechua was finally selected for diamond drilling.
The deposit, consisting of flat laying parallel veinlets with minor dissemination of chalcopyrite and garnet magnetite chalcopyrite skarn, occurs in a fracture zone, developed in Cretaceous sediments which are intruded by numerous flat laying dykes of porphyry. Wall rock alteration is characterized by carbonatization with moderate silicification while potassic alteration is rather weak.
These features suggest that the Quechua deposit was formed at offshoots far from a possible intrusive stock, and sulphide mineralization took place after solidification of porphyritic intrusives.

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A fair amount of magnetite occurs both in unaltered and specific altered facies of granodiorite porphyry which comprises a major host rock of the porphyry copper deposit at Michiquillay, Peru. Magnetite occurs as sporadically disseminated discrete grains in unaltered rocks, and both as disseminated discrete grains and veinlet fillings in altered rocks.
Microprobe analysis of minor elements (Ti, V, Al) of magnetite has been carried out for 17 specimens of unaltered and altered rocks. The alteration types are petrographically determined in the hand specimens and are classified into 4 categories; unaltered, potassic, incipiently retrograded potassic, and retrograded potassic-I. The latter two are interpreted to have been formed by the superimposition of the later stage alteration on the earlier potassic assemblage.
The results obtained are as follows: (1) Remarkable differences are observed between magnetite in unaltered rocks and that in altered rocks in the contents of minor elements and in the occurrence of titanium. (2) fairly systematic changes in minor elements are observed among the groups of magnetite from different alteration types.
The writer suggests, though further studies and confirmation are necessary, that these mineralogical characteristics might be applicable for exploration purposes as a tool to locate and distinguish altered and unaltered facies, and to establish alteration zones and/or sub-zones, even in case that hypogene alteration minerals have been obliterated by the superimposition of supergene-or later stage-alteration.

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