The Sangdong tungsten-molybdenum skarn deposits are embedded in the Pungchon limestone and limestone interbeds in the Myobong slate Formation of Cambrian age. The orebodies are composed of massive skarns and hydrothermal quartz veins. Sangdong granite of Cretaceous age (87.5 m.y.) which is recently found below the orebodies, has been slightly sericitized and pyritized, and it might be responsible for the W-Mo mineralization.
The orebody exibits well defined zonal distribution which consists, from periphery to center, of pyroxenegarnet-wollastonite zone, amphibole-mica-quartz zone and quartz-mica zone.
Stable isotope data of calcites and carbonate host rocks show mixing trend between regionally metamorphosed marble (δ ¹³C=0.6‰, δ ¹⁸O=+19.1‰) and fluids in equilibrium with deep seated granitic magma. Oxygen isotopic values of silicate minerals of the granite range from +10.1 to +11.3‰ which is rather homogeneous isotopic composition. Meanwhile, ore bearing skarn silicates and W-bearing hydrothermal vein quartz have a relatively scattered value ranging from +7.4 to +13.6‰ in δ ¹⁸O. Isotope geothermometry yields temperature of 860°C for the Sangdong granite, 670°C for the pyroxene-garnet zone, 630°C for the amphibole-mica zone and less than 350°C for the quartz-mica zone, the results of which indicate a retrograde metasomatism.
The calculated δ ¹⁸O and D/H values of H₂O equilibriating with quartz and hydrous mineral of W-bearing skarn silicates suggest that meteoric water influx increase toward later stage of tungsten mineralization.
Judging from the mineralogical, stable isotopic and chronological data, the metasomatic and hydrothermal ore fluids were derived primarily from the Sangdong granitic magma. This is also strongly supported by its sulfur isotope data of being δ³⁴S _Σs=+3-+5‰.

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Ten major inorganic elements in five Paleogene coal seams of the Ashibetsu colliery in the Ishikari coalfield were analyzed by X-ray fluorescence method. The vertical distributions of these elements and ash in five coal seams which were formed with similar depositional cyclothem were investigated. Some characteristics of major inorganic elements and ash are discussed in relation to the correlation among them and summarized as follows.
Silicon, aluminium, potassium and titanium correlate well with each other and ash content, suggesting that these elements could be associated with silicate minerals transported from the surroundings during coal deposition.
Iron and chlorine do not correlate with ash content. Their distributions in the coal seam are relatively even except pyritic iron near the top and the differences of their concentrations among the coal seams are not remarkable.
Magnesium is also uniformly distributed in comparison with other elements. The coal seams do not differ greatly in the concentration of magnesium, but it shows high correlation with ash content as for Torakawa seam. Magnesium appears to be associated with both silicate minerals and the other forms.
Calcium is unevenly distributed in some coal seams, but the average calcium content in every seam is approximately the same.
Strontium is highly concentrated in some parts of the coal semas and its concentration is in the same range of that of potassium. Atom ratio of strontium to calcium in the coal seams is very high compared with calcareous substances, plant and sea water. But the correlation between strontium and'calcium is not so high.
The coal seams differ greatly in the concentrations and distributions of strontium and phosphorus. The distribution patterns of them coincide well and give high correlation coefficient r=0.98 for them. Phosphorus is also highly concentrated in the coal seams, showing the maximum content 1.13%. This value may be the highest phosphorus content of coals in the world. The substance with which strontium and phosphorus could be associated is not clear.

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A boulder of orbicular chromite ore which is very rare in the world was found from the Omi district, Niigata Prefecture, central Japan. There has not been found any other chromitite in the vicinity.
The orbicular globule with chromitite-shell has 1-2cm of external diameter and the thickness of the chromitite-shell is 2-3 mm on average. Modal ratio of the orbicular globules to interglobular serpentinite is estimated to be 1:1.
The chromite grains, 0.3-1 mm across are generally euhedral but some of them are subhedral. EPMA analyses for three grains of chromite show that the chromites belong to high-chromium type with 50 wt.% Cr₂O₃ and are characterized by an increase in Fe ³⁺ and Ti, and a decrease in Al and Mg at the rim with constant Cr₂O₃ throughout the grain. The reason for this chemical substitution was interpreted as a result of interaction between chromite and a liquid of late magmatic stage under high fO ₂ condition using experimental data on the systems FeO-Fe₂O₃-Cr₂O₃ and FeO-Fe₂O₃-TiO₂at 1300°C as a function of oxygen fugacity.
It is presumed that the boulder of orbicular chromite ore might be derived from the foliated serpentinite melange cropping out along the middle stream of the Omi river.

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To understand the mode of differentiation of granitic magmas of Southwest Japan, neutron activation analyses have been made to measure the trace element abundance of the granitic rocks. During plagioclase-quartzbiotite fractionation, Ba and Rb enrich in successive solids and melt, while Sr is depleted. The incoming of Kfeldspar as a solid phase causes Ba to be depleted along with Sr in successively formed solids, while Rb continues to be enriched. As suggested by MCCARTHY and ROBB (1978), a change in liquidus mineralogy from plagioclase-quartzbiotite to plagioclase-quartz-K-feldspar-biotite during the in situ fractional crystallization of a granitic magma has a marked effect on the abundance of and interrelationships between Ba, Rb and Sr. In general, trace element data from the granitic rocks of Southwest Japan fit the model well, although the observed scatter of the data is somewhat greater than predicted by simple variation in cumulus-intercumulus proportions-possibly due to a diffeence in Ba, Rb and Sr contents of original melts, to the effect of assimilation, and to the change in the Sr partition coefficients for plagioclase during cooling.

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The Toyoha mine is a zinc-lead-silver vein-type deposit which is located in the Green Tuff Region of southwestern Hokkaido. Neogene Tertiary strata which consist mainly of volcanic and pyroclastic rocks are widely distributed around the Toyoha mine. They are composed of Koyanagizawa, Motoyama, Nagato, Oshidorizawa, Sanbonmata and Oheyama Formations and Younger andesite in ascending order.
Fission track age determination by zircon grains from some acidic tuffs of Motoyama, Oshidorizawa and Sanbonmata Formations was carried out using external detector method. Following fission track ages were obtained;
Motoyama Formation: 14.2±0.4 Ma and 13.3±0.9 Ma
Oshidorizawa Formation: 8.8±0.3 Ma
Sanbonmata Formation: 3.3±0.2 Ma
It is concluded that Motoyama Formation, and Nagato and Oshidorizawa Formations are correlated to Miocene Kunnui and Yakumo Formations of the standard stratigraphy of southwestern Hokkaido of Neogene Tertiary System. Sanbonmata and Oheyama Formations are correlated to Pliocene Kuromatsunai Formation respectively, and the strata of latest Miocene to early Pliocene are considered to be absent in the Toyoha mining area.

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