The Fukazawa kuroko deposits were discovered in the central part of the Hokuroku district by a systematic drilling work in 1969 to 1971. Since 1965 we have investigated the stratigraphy in the area by means of detailed geologic mapping and micro-fossil analysis. A concrete exploration work has been planned and carried out successfully based on the geologic information obtained and comparison to the geologic environment of other kuroko deposits such as those at the Kosaka and Hanaoka mines.
The area is occupied largely by volcanic rocks and pyroclastics of the Miocene age, which are divided into four units named Menaichizawa, Yukisawa, Kagoya and Shigenai formations in ascending order. The ore deposits consist of three main orebodies and several small ones. The orebodies are stratiform in general and occur at the top of the Yukisawa formation. Each orebody is composed of black ores and subordiante amounts of yellow ores, siliceous ores, and gypsum ores.
In the mine the production of crude ores was commemced in the rate of 10, 000 tons per month in November, 1973, and will be increased to 15, 000 tons in October, 1974.

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The contents of total copper (T-Cu) and cold-extractable copper (Cx-Cu) and the percentages of Cx-Cu to T-Cu in stream sediments were examined for three types of copper deposits, net-work, vein, and porphyry copper type deposits. The study indicates that geochemical exploration only by Cx-Cu in stream sediments is not adequate for locating orebodies, because hydromorphic trains are found at greater distances from mineralized areas. The anomalies delineated by T-Cu in stream sediments are composed of clastic and hydro-morphic trains. In some places, the latter is so storng, especially in humid tropic areas, that the anomalous areas delineated by T-Cu do not always related to the mineralized areas. In such cases, only clastic anomalies can disclose mineralized areas.
Variation of the. percentages of Cx-Cu to T-Cu may be a useful indicator for mineralization and it may be considered that the decreasing point of the percentages shows the entrance of a clastic anomaly which may be located above mineralized bodies. If values of Cx-Cu and T-Cu at each sampling site are nearly same and only hydromorphic anomalies are obtained, we may consider that blind copper ore deposits are expected near the hydromorphic anomalies which are caused by mixing drainage and ground water running through blind ore deposits.
(1) Kamanai deposit (Miyagi Pref., northern Japan)
A net-work deposit occurs in Miocene propylyte covered by post-mineralization dacite tuffs of Pliocene. An anomalous level of T-Cu appears in the area of the mineralization, but the values of Cx-Cu do not show much difference between the mineralized area and the non-mineralized area in the downstream. The percentages of Cx-Cu to T-Cu decrease sharply in the mineralized area, showing the hydromorphic precipitation in the downstream.
(2) Kunimiyama deposit (Miyagi Pref., northern Japan)
The deposit consists of many small copper veins in Miocence andistic tuff. The level of T-Cu does not show any difference between the mineralized and non-mineralized areas, but that of Cx-Cu decreases sharply in the mineralized area, showing high precipitation of hydromorphic copper in the downstream. This high precipitation of Cx-Cu seems to be caused by abundant supply of leached copper from old dumps. Such an abundant supply of leached copper from copper deposits would be common in tropical humid terrains.
(3) Mamut deposit (Sabah, Malaysia)
This deposit is located on the eastern flanks of Mt. Kinabalu (4, 101 m), the highest mountain in Borneo. The topography is very rough with heavy forest cover. The annual pre-cipitation is about 3, 500 mm. The deposit is of porphyry copper type and consists of dissemination of pyrite, chalcopyrite, chalcocite, and a small amount of molybdenite in association with storong siliciacation of diorite porphyrite stock which intruded into Tertiary sedimentary rocks and ultrabasic rocks. The anomalous levels of T-Cu and Cx-Cu appear in the downstream of the ore deposit. But the percentages of Cx-Cu to T-Cu clearly decrease in the area of the ore deposit, showing high precipitation of leached copper from the deposit.

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Platinum grains from Yubdo, western Ethiopia, have been studied. The grains occur in lateritic layers covering ultrabasic rocks and birbirites. Most of the grains are subangular and are coated by iron hydroxides and iron oxides. One of the grains consists of two kinds of platimum alloy which resemble each other under the microscope. Chemical analysis of the outer and core parts has been made by using a Shimadzu-ARL electron microprobe X-ray analyzer, EMX-SM. Their compositions correspond to (Pt_1.98Rh_0.06Os_0.05Pd_0.03)_2.12(Fe_1.34Ni_0.14)_1.48Cu_0.40 and (Pt_0.75Rh_0.10Pd_0.02)2.87Fe_1.03Cu_0.10 as total sum of metals=4, respectively. The composition of an osmium grain included in the outer zone corresponds to Os_1.77Ir_0.13Ru_0.04Pt_0.03Rh_0.02Fe_0.01 as total sum of metals=2. The ratio of Os:Ir:Ru is 91.6:6.7:1.7.
An occurrence of ferroplatin containing some amount of Au was described from the area by OTTEMANN and AUGUSTITHIS(1967), but Au has not been detected in the grains analysed in the present study.

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The Matsumine ore deposit of the Hanaoka mine, Akita Prefecture, Japan, is one of the typical Kuroko (copper-lead-zinc sulfide) deposits, which are recently considered by many geologists as submarine exhalative origin. It occurs in the Miocene marine pyroclastic rocks. Alteration zones surrounding the ore deposit consist successively of silicified zone (IV), clay zone (III), sericite-chlorite zone (II), and montmorillonite zone (I) from lower or inner to upper or outer.
Zone IV, which is altered rhyolite lava dome, is characterized by association of quartz and well-crystallized sericite. Zone III is a lenticular clay bed, enclosing the main ore deposits, and is abundant in interstratified sericite/montmorillonite, particularly at the marginal hanging wall and the end of clay bed. Mg-chlorite, gypsum, and pyrite are also common in the main part of zone III (IIIB), but at the end of clay bed (IIIA) they are rare and plagioclase is found. The main part of zone II(IIA) is compósed principally of sericite minerals (sericite and interstratified sericite/montmorillonite), chlorite, quartz, and feldspar, the last of which is lacking in the portion of this zone right above the ore deposits (IIB). Zone I, characterized by common occurrence of montmorillonite, contains mordenite in the lower portion and opal in the upper, but right over the ore deposits mordenite is almost lacking and the lowest level of opal is close to the boundary with Zone II. The boundary of zones I and II crosses stratigraphic boundaries.
These complicated zonal patterns may have both stratigraphic and concentric natures, and together with the variation of mineralogical properties of sericite minerals suggest that there were syngenetic and epigenetic alterations. The syngenetic alteration, which formed the clay bed, is inferred as reactions between the hydrothermal ore solutions and volcanic glasses in the sea bottom. The epigenetic alteration, which formed the concentric zonings after accumulation of pyroclastics above the ore deposits, may have been principally made by a hydrothermal solution which continued to ascend after ore mineralization.

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