The compositional distribution of elements in an epidote from the epidote skarn in the Yaguki tungstencopper mine, northeastern Japan shows an increase in Al and Ca contents with a concurrent decrease of Fe and Mn contents from the core to the margin, which is clearly visualized by colored mapping.
The compositional pattern and quantitative analytical data of the zoned epidote demonstrate that the Fe ³⁺/(Fe ³⁺+Al) ratio in the octahedral site changes continuously in a wide range from 0.28 down to 0.02 and the manganese substitution for calcium in the A site up to 6 percent. Such mineral chemistry of the epidote can be attributed to lowering in the temperature and/or a decrease in the ratio of FeCl₃/(FeCl₃+AlCl₃) in the coexisting fluid.

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Electrum-sulfide mineralization of the Daeil and Yeongbogari mines in the Youngdong area consists of two stages of quartz and calcite veins that fill fault zones in Precambrian metamorphic rocks. Radiometric dating indicates that mineralization of the Daeil mine is Jurassic age (145 Ma), whereas that of the Yeongbogari mine is Cretaceous (132 Ma). Mineralogy of the two mines differs significantly in that only the Yeongbogari mine contains silver-bearing minerals (argentite, argentian tetrahedrite, pyrargyrite) and its electrums are more silver-rich (49.1 to 71.4 wt.%Ag) than those of the Daeil mine (28.0 to 37.8 wt.%Ag).
Fluid inclusion data show that ore mineralization occurred at temperatures between 375° and 246°C from fluids with salinities between 9.1 and 2.6 wt.% equiv. NaCl. The estimated temperature and sulfur fugacity for gold deposition in the Jurassic Daeil mine are much higher (≈350°C, 10 ^-9 atm.) than those for the Cretaceous Yeongbogari mine (≈275°C, 10 ^-12 atm.). Fluid inclusion evidence of boiling indicates pressures of<200 bars, corresponding to depths of 800 to 2, 600 m assuming lithostatic and hydrostatic pressure regimes, respectively.
Sulfur isotope compositions of sulfide minerals are consistent with sulfur from igneous sources in the Daeil and Yeongbogari mines. Estimated δ³⁴SΣS values for the Daeil and Yeongbogari mines are 8 and 3 per mil, respectively, which may reflect differences in the separation of sulfur-bearing magmatic fluids from their associated granitic magmas.
The difference in ages, mineralogy and ore deposition conditions between the Jurassic Daeil and Cretaceous Yeongbogari deposits further validates the idea of multiple gold-silver metallogenic epochs in Korea. Deposits associated with Jurassic granites are formed at typically deeper and higher temperature conditions and are more gold-rich than those associated with Cretaceous granites.

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The manganese micronodules in the zeolitic sediments from the Penrhyn Basin were studied for their abundance, mineralogy, internal texture, and chemical composition by means of ore-microscopy, X-ray diffraction, and electron microprobe analysis. The results are summarized as follows.
(1) The abundance of micronodules ranging in size from 50 to 500 mesh sieve tends to decrease with increasing grain size. These tendencies are similar to the results of micronodules in the siliceous sediments from the Central Pacific Basin. On the whole, the abundance of micronodules ranging in size from 350 to 500 mesh sieve in the zeolitic sediments tends to be higher than that in the siliceous sediments.
(2) The micronodules are classified into four types based on their internal texture; Type-I with dendritic, cuspate or mottled texture, Type-II with columnar or stratified texture, Type-III with alternation texture comprising of ferromanganese oxide layer ("Ox" layer) and ferromanganese oxide layer rich in fine-grained silicate ("S" layer), and Type-IV with flat and stratified texture.
(3) The constituent ferromanganese minerals of micronodules areas follows. Type-I appears to be mainly composed of 10 Å-manganate, while Type-II and Type-III ("Ox" layer) to be of δ-MnO2.
(4) Type-I is characterized by high contents of Mn, Ni, and Cu and low content of Fe, whereas Type-IV is characterized by high content of Fe and low contents of Mn, Ni, and Cu. Type-II and Type-III ("Ox" layer) have intermediate contents of Mn and Fe between Type-I and Type-IV.
(5) With respect to internal texture, chemical composition, and constituent minerals, Type-I micronodules in the zeolitic sediments resemble to those in the siliceous sediments. Similarly, Type-II and Type-III ("Ox" layer) micronodules in the zeolitic sediments resemble to Type-II in the siliceous sediments. But micronodules in the zeolitic sediments generally have higher content of Fe and lower content of Si than those in the siliceous sediments.

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Homogenization temperatures and salinities of fluid inclusions in some minerals from the Kawahira and Seikyu deposits in Shimane Prefecture, Shisou deposit in Hyogo Prefecture, and Nakatatsu deposit in Fukui Prefecture were measured in order to evaluate physico-chemical conditions for the molybdenum mineralization, and to compare them with those for tungsten and other metalliferous deposits in Japan.
Salt-bearing polyphase inclusions as well as liquid-rich two-phase inclusions are found in vein quartz from the Kawahira deposit, in pegmatitic quartz from the Shisou deposit, and in clinopyroxene from the Nakatatsu deposit. CO₂-bearing fluid inclusions as well as liquid-rich two-phase inclusions are found in vein quartz from the Seikyu deposit.
Fluid inclusions in vein quartz from the Kawahira deposit show the homogenization temperatures ranging from 215°to 390°C, and the salinities ranging from 3 to 37 wt% (NaCl eq.). Plots of homogenization temperature against salinity of fluid inclusions show two populations of inclusions. It is concluded that these two populations originated from incomplete mixing of saline solution with dilute one.
Homogenization temperatures and salinities of fluid inclusions from the Seikyu deposit range from 191°to 325°C, and from 4 to 18 wt% (NaCl eq.), respectively.
Data for the Shisou deposit show that the homogenization temperatures range from 205°to 416°, and that salinities range from 11 to 44 wt% (NaCl eq.).
Fluid inclusions in clinopyroxene, vein quartz, and calcite from the Sennou ore body of the Nakatatsu deposit show the homogenization temperatures ranging from 342°to 520°C, from 170°to 467°, and from 140°to 397°, respectively. Salinities of fluid inclusions in clinopyroxene, vein quartz, and calcite range from 2 to 50 wt% (NaCl eq.), from 1 to 15 wt% (NaCl eq.), and from 0 to 11 wt% (NaCl eq.), respectively. It is shown that clinopyroxene precipitated at higher temperatures than quartz and calcite in veins. Plots of homogenization temperature against salinity of fluid inclusions show two populations of inclusions; one for the mineralization of clinopyroxene with large variation in salinity, and the other for the mineralization of quartz and calcite with large variation in temperature.
Compilation of fluid inclusion data for Japanese molybdenum deposits shows that the hydrothermal solutions with high salinities are characteristic for molybdenum mineralization in Japan, compared with Japanese tungsten and other metalliferous deposits.

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