[in Japanese]

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Molybdenum and tungsten deposits provide clear examples of ores related to granitic rocks. The writer (ISHIHARA, 1971a) has pointed out that tungsten deposits tend to be associated with less acid intrusions than molybdenum deposits and that scheelite (not wolframite) in non-calcareous wall rocks occurs where the source granitic magma is calcic. He also proposed a new scheme of the Mo-W metallogenic provinces of Japan, the Kitakami district of which shows a reverse pattern in lateral zoning of those of the Inner Zone of Southwest Japan (ISHIHARA, 1971b). Fundamental data and reasons for the above proposals taken from the Kitakami district have not yet been 'published. This paper, as a sequel to the previous two papers, describes zonal distribution of the metals and nature of the granitic rocks of the Kitakami district. Genesis of the metallogenic provinces of Japan is discussed in terms of the plate tectonics model.
The Cretaceous-Paleogene granitic rocks in the Honshu Island show definitely regional variation in composition. It is basic at one side (either continental or oceanic) and becomes acidic at the other side. This is tentatively called "Lateral differentiation trend", and is shown by changes in regional bulk composition and in ratios of Fe⁺³/Fe⁺², NA/K, Th/K, U/K, Rb/K, etc. of the granitic rocks, and distribution of the Mo-W deposits. One suite of these variation is considered as the most fundamental unit of petrogenetic province. Each province consists of subprovinces such as Mo-, W-, and Barren provinces.
The lateral diffentiation trend is continentward in the Inner Zone of Southwest Japan (arrows in Fig. 9), but oceanward in the Abukuma and Kitakami Belts. Hence, the most distinct discontinuity appears some place along the present Tanakura tectonic line. The asymmetrical zoning in the Inner Zone of Southwest Japan (see Table 5) can be explained by a magmatic differentiation model during ascending of granitic magma along a continentward-dipping weak zone in crust or Benioff zone itself. This hypothesis was discussed in this paper in emphasizing role of H₂O and differences on volatilities of Cl- and F-complexes. This hypothesis implies that Northeast Japan belonged to a different plate from that of the Inner Zone of Southwest Japan and also the paleo-Benioff zone or the conduit of the granitic magma inclined steeply oceanward at the Cretaceous time.

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This study on the vein-type mineralization in the Josen Honpi mining area, Kishu mine, involves statistical analyses and some genetic considerations derived from various results of the analyses and conventional geological data. The factors used for the analyses are strike, dip, width and grade of the veins. The statistical distribution charts obtained from these factors are given in figures on the Schmidt's net and frequency figures of the veins. These figures respectively show the vein structure and close relationship between the vein system and the geologic structure. Some situations of mineralization are calculated from the correlation between Cu% and S%, dip and strike, richness (grade × width of vein), width, etc.
The distribution graphs of Cu% and value of S/Cu show the position of copper bonanza and suggest ore shoot. The main current of copper-bearing solution passed through the E14 block at No.5 adit level and rose diagonally to the west and then went through the E12 block at No.3 adit level and reached No.2 adit level. In other words, it rose to the upper part in the D member (alternation of sandstone and shale) and then farther to the C member (medium-grained sandstone).One of the tributaries to the main current flowed into fissures at right angles to the synclinal axis of the country rocks in this area and formed the veins of the W1 block at No.2 adit level. Then, the tributary went down to the W1 block at No.3 adit level.

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[in Japanese]

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