The contact metamorphism was superimposed on the regional glaucophanitic one in the deeper levels of the Besshi deposit. The mineral assemblages change progressively with increasing depth by this event. Sulfide mineral assemblages were studied on regional and contact metamorphosed ores of the deposit.
Pyrite, chalcopyrite and sphalerite assemblage is the majority of ores suffered the regional metamorphism. Pyrite-chalcopyrite-bornite and pyrite-hematite-magnetite assemblages, which constitute univariant equilibria in Cu-Fe-S and Fe-S-O systems, are sometimes observed in these ores. T and fS ₂ of the metamorphism were discussed from the mutual relation of these univariant equilibria. T and fS ₂ were also obtained at high pressures from FeS contents of sphalerite (0.48-0.90 mole %) associated with pyrite-chalcopyrite-bornite assemblage. They are 280°-350°C and 10 ^-8.7 -10 ^-6.4 atm, supposing 5 Kb lithostatic pressure.
By contact metamorphism, pyrrhotite is formed from pyrite in the levels deeper than 18 L. Fe contents of pyrrhotite increase with increasing depth, from monoclinic modification containing 46.7 atomic % Fe and hexagonal one with 47.3 atomic % Fe in 18-25 L to 47.5-48.0 atomic % Fe in 26-33 L. FeS contents of sphalerite associated with pyrrhotite are in the range of 16 to 20 mole %, which does not correspond to pyrrhotite with 47.5-48.0 atomic % Fe. Hexagonal pyrrhotite coexists commonly with pyrite, which shows sometimes euhedral shape. This association is incompatible in the light of the low temperature phase relation of Fe-S system. hitherto established. Pyrrhotite alone may have changed its composition during the retrogressive metamorphism, reflecting the T-fS ₂ environments. Sphalerite and pyrite, on the contrary, may preserve the high temperature states. It is therefore difficult to obtain metamorphic T and fS ₂ from the compositions of coexisting sphalerite and pyrrhotite, unless detailed study is made on the compositional change of these minerals in the retrogressive metamorphism. The association of hexagonal pyrrhotite and euhedral pyrite may be showing that pyrrhotite of high temperature type and pyrite were once in equilibrium at the climax of the metamorphism.
Sphalerite has no exsolution dots in the contact metamorphosed ores. The absence of exsolution dots will be due to the low fS ₂ environments in the retrogressive metamorphism, corresponding to pyrrhotite with 47.5-48.0 atomic % Fe.

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The Neogene formations of the Aizu district have a total thickness of about 3000m, of which volcanic and pyroclastic rocks constitute the dominant part. Structually, the district is made up of eight basins and several upheaval zones, which have resulted from block movements of the basement rocks simultaneous with sedimentation of the Neogene formations. Diagenetic alteration zones of the Neogene acidic volcanics are arranged in the following succession from top to bottom; fresh glass, clinoptilolite-mordenite, analcime, laumontite, and albite-chlorite-sericite zones. In the basins these zones are distributed in subparallel to the stratigraphic boundaries. In the upheaval zones, the zeolite zones are thin or absent, and various types of hydrothermal alteration zone are superimposed on the diagenetic alteration zones.
The Kuroko and Kuroko-type gypsum deposits occur in the Miocene strata, being located in the margins of the basins. Hydrothermal alteration zones around the ore deposits are outwardly arranged as follows: silicified, quartz-sericite, albite-chlorite-sericite, and montmorillonite zones in the floor of the ore depotits; and sericite, sericite-chlorite, and montmorillonite zones. in the roof of the ore deposits. The outer zones of hydrothermal alteration grade outward and upward into the diagenetic alteration zones. Veins of gold, silver, copper, zinc and lead occur in the upheaval zones, and are enclosed by hydrothermal alteration zones. The arrangement of the zones, from center to periphry, is as follows: silicified, quartz-sericite, adularia, and albite-chlorite-sericite zones. Sericite and kaolin deposits also occur in the upheaval zone. The sericite deposits are hydrothermal alteration products caused by the submarine volcanic activities of the Miocene age. On the other hand, kaolin deposits have their origin in the terrestrial volcanic activities of the Miocene and Quaternary ages.

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Systematic field and laboratory studies of profile of several nickeliferous laterite deposits in the Southwestern Pacific area, show their genetic relationship with the underlying ultramafic rocks. The transformation of the fresh parent rock to the final product was traced mineralogically, petrographically and geochemically. Deposits can be divided into two layers. The upper part is composed of oxidized red laterite ore and the lower one contains so-called garnieritic ore, actually saprolite or decomposed serpentinite.
A clear difference exists between the chemical compositions and mineralogy in the upper and lower layers. Goethite is the principal mineral in the upper layer and serpentine is most common in the lower one. In some cases, a thin secondary silica layer is intercalated near the boundary. Conversion of serpentinite to laterite is reflected by an increase in Fe₂O₃ and a decrease in SiO₂ and MgO. Minor elements show no difference between serpentinite and laterite. Iron in laterite occurs mainly as hydrated oxide. Nickel is concentrated with goethite in laterite and partly with hydrous nickel-iron-magnesium silicates in the decomposed serpentinite layers.
Electron-Probe microanalyses of laterite have shown that the concentration of Ni and Fe in laterite is relatively uniform. On the other hand, the replacement of Mg by Ni and Fe is clearly evident in the decomposed serpentinite layer.
Mobilities of Ni and Fe by leaching in both the laterite and the garnieritic ores were examined by the citric acid method. The amount of soluble nickel and iron in laterite is higher than that of decomposed serpentinite.
X-ray diffraction studies on numerous garnierite samples in the district indicate that they contain either abundant 10Å (talc-like) minerals or a mixtures of 10Å and 7Å (serpentine group) minerals. Samples containing only 7Å minerals are scare.

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The modes of occurrence, associated mineral assemblages, and chemical compositions of alabandites from the bedded manganese ore deposits in Paleozoic formations of the Seta district, Gumma Prefecture, are described on the basis of microscopic observation and electron probe microanalysis. 22 samples were studied from five mines-Hagidaira, Rito, Hanawa, Showa, and Nakanoyama. From the results obtained, the conditions of formation of alabandite can be considered as follows.
1) Both wall rocks and ore minerals of the Hagidaira mine have been thermally metamorphosed by the intrusion of the Sori granodiorite, the former to biotite hornfels, while the latter are now composed mainly of rhodonite and tephroite, associated with pyrite, pyrrhotite, sphalerite, and chalcopyrite. The amount of alabandite in Hagidaira is significantly greater than in the other mines and its grain size is also larger. Furthermore, the FeS content of the alabandite varies considerably from 0.3 to a maximum of 10.0 mol.%.
2) The other four deposits, Rito, Hanawa, Showa, and Nakanoyama, occur in unmetamorphosed Paleozoic sediments. These ore deposits are composed mainly of fine-grained rhodochrosite, and small amounts of alleghanyite and pyroxmangite. Alabandite from these deposits is less in amount and its grain size is very small. The content of FeS in the alabandite varies only slightly over the range 0.2 to 2.0 mol.%.
3) The difference in the mode of occurrence and chemical composition of alabandite between the Hagidaira mine and the other four mines can be attributed to thermal metamorphism caused by the granodiorite. However, the variation of FeS content in alabandite in the orebody of the Hagidaira mine does not depend on temperature, but is due to changes in fs ₂ produced by fo ₂ and fCO₂ variations between coexisting manganese oxide, silicate, and carbonate minerals.
4) On the other hand, it is considered that the formation of alabandite in the Rito, Hanawa, Showa, and Nakanoyama deposits is independent of thermal metamorphism.

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