Manganese deposits of the Noda-Tamagawa mine occur as a banded and folded stratiform in chert bed of the Akkagawa formation which belongs to Jurassic age, and were thermally metamorphosed by intrusion of Tanohata granite. In result, they generally became rhodonite (outside), tephroite (inside) and hausmannite (center) which formed ore zones with a banding structure as shown in Fig. 2.
Rhodonite and tephroite from each zone were quantitatively analyzed by EPMA to know their chemical compositions, as given in Tables 1, 2 and 3. According to these data, compositional ranges of rhodonite are 1.2-13.8 mole% FeSiO₃, 62.3-88.9 mole% MnSiO₃, 1.3-13.2 mole% MgSiO₃ and 2.3-17.8 mole% CaSiO₃, while those of tephroite are 0.5-11.5 mole% Fe₂SiO₄, 70.7-91.9 mole% Mn₂SiO₄, 6.2-21.2 mole% Mg₂SiO₄ and 0.0-1.8 mole% Ca₂SiO₄. The compositions of rhodonite and tephroite differ with not only localities, but also at a same place as shown in Figs. 4 and 5, respectively. They also change irregularly their compositions in the ore zones of both hanging and foot-wall sides at same place as shown in Fig. 6. Such compositional changes of rhodonite and tephroite are thought to reflect those of primary materials such as rhodochrosite and bementite etc. Although rhodonite and tephroite were formed by thermally metamorphic reaction between rhodochrosite and silica occurred primarily as hydrothermal sedimentary products due to postaction of submarine volcanism (WATANABE et al., 1970a, b), diffusion of atoms such as Fe, Mg, Ca and Si etc. in the ore bed by the metamorphism is considered to be slow. From the data of compositional changes of both minerals, the distance of the atomic diffusion is limited within a few centimeters.

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The Myoho deposit, Kii Peninsula, consists of numerous copper veins filling mostly extensional fractures, and rarely faults. The veins trend generally N-S and NW-SE. Branch veins are found frequently to form ore shoots. The branches are generally predominant on the hanging wall. The fractures played a role of the pathway of mineralizing fluid, but some of faults dammed up the fluid. From the center outwards, the horizontal hypogene zoning is shown by barren quartz, chalcopyrite-bornite, galena-sphalerite, Au-Ag minerals, and chal-cedonic quartz as shown in Fig. 11.

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The Toyoha zinc-lead-silver ore deposits are typical vein-type ones in the Green Tuff Region of Southwest Hokkaido. It is well known that the veins of the Motoyama deposits are divided into two different groups, the earlier stage veins (Tajima, Harima etc.) and the later ones (Soya, Izumo, Sorachi etc.). The wall rocks of the deposits composed of andesite, dacite, basalt, pyroclastic and sedimentary rocks of Miocene age are hydrothermally altered. The wall rock alteration around the Tajima, Soya, Izumo and Sorachi veins which have different miner-alogical features is summarized as follows:
(1) Hydrothermal alteration around the Motoyama deposits is divided into the following five alteration zones.
A Chlorite-calcite
B Quartz-chlorite-calcite-albite K-feldspar
C Quartz-chlorite-sericite-pyrite
D Quartz-sericite-pyrite
E Quartz-sericite-kaoline-pyrite
(2) Chemistry of chlorite shows that Mg-Fe chlorite ((Fe+Mn)/(Fe+Mn)+Mg=0.3) was formed by alteration A, Fe-Mg chlorite (0.5) by B, and Fe chlorite (0.9) by C. Sericites from alteration zone of B, C and E scarcely contain any expandable layer, while sericite from alteration zone of D contains a small amount of expandable layer.
(3) As to the alteration process: 1. Regional alteration of A occurred widely around the Toyoha mine;
2. Alteration of B occurred locally in the mineralized area; 3. Alteration of C and D enveloped the veins; 4. Geothermal alteration of E took place at the Sorachi vein only.
(4) The hydrothermal alteration observed in the Tajima, Soya, Izumo and Sorachi veins is almost the same. The chemistry of chlorite, however, from the alteration zones of the Toyoha mine differs from that of the hydrothermally produced chlorite in the Chitose (Au-Ag) and the Ohe (Mn-Zn-Pb) mines of the same metallogenic province as the Toyoha mine.

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Mineralization of the Arakawa No. 4 vein, one of the representative veins in the Kushikino mine, was investigated. Four periods of mineralization are recognized. They are, from earlier to later stages, period I (quartz-calcite zone), period II (high grade "Ginguro" ore zone containing polybasite, electrum, pyrite and tetrahedrite), period III (brecciated quartz-calcite-clay zone), period IV (banded "Ginguro" zone containing polybasite, electrum and pyrite). Period II can be divided into earlier one (period IIa containing polybasite and pyrite) and later one (period IIb containing electrum, polybasite, pyrite, sphalerite and chalcopyrite). No compositional variations were found in electrum and tetrahedrite. On the other hand, decrease of iron content of sphalerite, and increases of selenium contents of polybasite and naumannite-acanthite series minerals from earlier to later stage were observed. Filling temperature of fluid inclusions decreases slightly from earlier to later periods; 240-200°C for period I, 240-180°C for period II and 220-170°C for period IV. Based on the variations in the iron content of sphalerite and filling temperatures of fluid inclusions, sulfur fugacity for period II is estimated to be 10^-11-10^-13 atm. Decreasing of temperature under the relatively oxidizing environments can explain the variations of selenium contents of polybasite and naumannite-acanthite series minerals.

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