The Hidaka Series of the Shimokawa mining area consists mainly of an apparent ophiolite suite that comprises ultramafic rocks, gabbro, diabase, massive and pillow basalts, with numerous intercalated pelitic, psammitic and rarely calcareous layers. These rocks are widely altered and the assemblages of replacing min-erals range from prehnite-pumpellyite facies to a transition state from greenschist to amphibolite facies. The alteration mineral zoning and the compositional variation of amphibole from actinolite to magnesio-hornblende downward indicate a thermal gradient estimated to be about 140°C/km. The chemical compositions of amphibole and chlorite formed by the alteration are analogous to those from mid-ocean ridges. It may be considered that the mafic rocks and sediments in Shimokawa area were formed on a sea-floor growing new oceanic crust where an adequate amount of clastics was supplied from the adjacent land and altered by circulating hydrothermal water.

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Magmatists' view of hydrothermal ore formation is evaluated and acessed on the basis of experimental results and computer simulation. The present investigation revealed that the hydrothermal fluids separated from granitic magma have enough potential to generate hydrothermal ore deposits of base metals like copper, zinc, lead, and molybdenum if the granite has the following characters; (1) saturatedd with aqueous fluid; ex-periments (KILINC and BURNHAM, 1972; SHINOHARA et al., 1984) revealed that chlorine is in favor of the fluid phase. High temperature chloride solution is eligible to transport metals, (2) aluminous; because aluminous granite magma has high partition ratios of metals between coexisting fluid and melt (URASE, 1984), (3) high-level pluton; because metals are strongly partitioned to fluid phase at lower pressures, and (4) magnetite-series; probably because of partitioning of sulfur to the fluid phase in the form of SO₂ under high oxygen fugacity of the magnetite-series granite. Computed "ore-forming fluid" is considered to be capable of forming the base metal deposits.

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The studies on the clay minerals occurring in the Arakawa No. 4 vein of the Kushikino Au-Ag deposits and in the host rocks revealed that,
(1) There occur four kinds of clay minerals in the vein, namely, interstratified chlorite/smectite, interstratified mica/smectite, smectite and chlorite. Abundances and kinds of these clay minerals change with the depth of the vein:interstratified mica/smectite, interstratified chlorite/smectite and smectite occur predomi-nantly at the upper, middle and lower portions of the vein, respectively. The occurrence of chlorite is restricted to the brecciated part composed of wall rock and vein-quartz fragment, and
(2) Regularly interstratified chlorite/smectite containing high amounts of Mg is a characteristic clay mineral occurring in the high grade gold and silver ores. Predominant clay mineral in the wall rock is Fe⋅Mg chlorite (including irregularly interstratified chlorite/smectite). This clearly different nature of the charcteristic clay minerals in the vein and wall rocks suggest that the regularly interstratified chlorite/smectite was directly precipitated from the ore fluids responsible for the gold-silver mineralization.

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Gold-bearing massive silicified rocks occur in the volcanic piles of the Neogene Tertiary age in the Makurazaki district, southern Kyushu and are termed as the Nansatsu type gold deposits. Currently three mines, Kasuga, Iwato and Akeshi, are operating. The argillized zones consisting mainly of quartz, kaolinite and minor goethite surround the silicified rocks. Alunite series minerals occur in and around the silicified rocks.
Ages of mineralization have been discussed for many years but were unanswered. K-Ar dating of selected alunite and alunite-bearing rocks from three mines yields ages of 5.5-3.7 m.y. K-Ar ages at Mt. Sonomi of the Kasuga mine (5.5±0.4m.y.) and at the Arabira orebody of the Iwato mine (4.7±1.0m.y.) probably represent the ages of gold mineralization. Slightly younger ages at Mt. Iwato of the Iwato mine (4.4±0.7m.y.) and at the No. 1 orebody of the Akeshi mine (3.7±1.1m.y.) might reflect possible changes in chemical composition of alunite during weathering after mineralization.
Gold-silver mineralization in southern Kyushu took place in the Pliocene to early Pleistocene, except minor silver-rich vein type deposits in the middle Miocene time. This study shows that four values are concordant with each other and indicate the latest Miocene to early Pliocene ages for mineralization of the Nansatsu type gold deposits in the Makurazaki district. The ages are comparable with the vein type gold deposits of the early Pliocene time such as Kushikino (4.0±0.3m.y.) and Hanakago (4.8±2.9m.y.). Another gold mineralization were known in the early Pleistocene time such as Hishikari (1.5±0.3m.y.) and Ora (1.8±0.2m.y.). At present there seems to be only minor gold mineralization between 4 and 2 m.y.

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The thermoelectric power (α) and semiconducting properties are closely related. For a particulate sample of sulfide minerals and ores the former can easily be obtained by measuring the thermo-emf (which does not invole the passage of current) of a packed bed which is subjected to a temperature gradient. In this study an improved apparatus was designed and used to measure α, activation energy for α (Eα) and that for conductivity (Eσ) in the temperature range of 55°-85°(328-358 K).
Sulfide ores involving yellow ores and black ores were supplied from the Matsumine, Ezuri, and Fakazawa mines. Samples for the measurements were prepared by proper methods involving crushing and/or washing to pick up small crystals, crushing and sieving for massive lumps. The composition of the samples was determined by chemical analysis and the mineralogical composition was calculated.
The results obtained are as follows:
(1) The α vs.±E_α plot (Fig. 1) reveals that most of yellow ores are n-type semiconductors and they are distributed differently with each mine. Galena and sphalerite samples are both p-type semiconductors, whereas black ores (mixture of chalcopyrite, pyrite, galena, and sphalerite) are n-type.
(2) α of yellow ores containing pyrite and chalcopyrite is strongly dependent on the chalcopyrite content. A critical value of 1.5 mol% chalcopyrite is found, below which α (-108μV/deg), E_α(0.046 eV) and E_σ (0.20 eV) are irrelevant to the chalcopyrite content. In the range from 1.5 to 20 mol% chalcopyrite, α varies from about 100 to -200 μV/deg and following correlations are obtained (Cp: mol% chalcopyrite).
α=160-300 log(Cp)
-E_α=0.04-0.116 log(Cp)
Correlations are also obtained between α and E_α and between E_α and E_σ.
(3) Galena samples contaminated with 4 mol% chalcopyrite are p-type semiconductors with α: 300-400 μV/deg, E_α:0.40-0.50 eV, and E_σ: 0.28-0.38 eV. Sphalerite samples contaminated with 1-2 mol% chalcopyrite are also p-type semiconductors with α: 200 μV/deg, whereas that contaminated with 6 mol% chalcopyrite is n-type.
(4) The average composition of black ores in mol ratio is chalcopyrite: galena: sphalerite: pyrite=1:0.2:1:1.5. Values of α, E_α, and E_σ of black ores are 0--350 μV/deg, 0-0.45 eV, and 0.11-0.28 eV, respectively.
For the samples from Matsumine ore deposit, α and E_σ tend to decrease with an increase in galena content.
(5) The correlations for yellow ores were discussed. It is shown that α is represented by, α(V/deg)=98×10^-6+0.095/(2eT)-3.9k/(2e)⋅In(Cp)
where e is the charge of an electron, T is the absolute temperature, and k is Boltzmann′s constant.

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