The Ohmine granitic rocks of Miocene age occur in the central Kii peninsula, Outer Zone of Southwest Japan. These rocks fall into two distinct types; S-type and I-type (Dorogawa and Shirakura rocks). Trace elements (Ba, Ce, Co, Cr, Cs, Nb, Ni, Rb, Sc, Sr, Y, Zr, and F) of the rocks were determined by photon activation, colorimetry, and ion-electrode analyses. The S-type granitic rocks are high in SiO₂, F, and Rb/Sr and low in Sr compared with the I-type ones. The Shirakura rocks formed early stage in the intrusive sequence are higher in D. I., Ce, Rb, and Nb and lower in MgO/(MgO+FeO^t), Co, Cr, Ni, and Sr than the Dorogawa ones. The S-type magma, from which biotite, plagioclase, and orthoclase must have fractionated, would be formed by partial melting of biotite and orthoclase containing sedimentary and/or metasedimentary rocks at about 700°C and 5 kbar. The I-type granitic rocks were probably generated by partial melting of Caamphibole and plagioclase containing intermediate igneous and/or metaigneous rocks. Fractional crystallization mainly of plagioclase, Ca-amphibole, and biotite must have occurred in the I-type magma. The Shirakura magma would be produced by lower degree of partial melting than the Dorogawa one. The crystallization course of the I-type magma was different from that of the S-type one ; orthoclase precipitated next to quartz in the I-type magma, on the contrary quartz crystallized after orthoclase in the S-type magma. On the basis of trace elements behavior, it is unlikely that the granitic rocks are products of large scale magma-crust interaction and of mixing between basaltic and granitic magmas.
On the criteria of alumina saturation and isotope ratio, revised classification of calc-alkali granitic rocks are proposed; C-type (sub to metaluminous, SrIo⟩ 0.708) and W-type (per. aluminous, SrIo⟨0.708) in addition to I-type and S-type. C-type rocks are, however, not found yet. The parental materials and fractionating phases of the I-type, W-type, and the S-type in the world are estimated from publicated data. The estimated parental materials and fractionating phases of the I- and W-type and the S-type are the same as those of the Ohmine I-type and the Ohmine S-type, respectively. The I- and W-type rocks are, therefore, in lower range of Rb/Sr than the S-type ones. Many I- and W-type granitic rocks occur in mature continental regions composed of basaltic and granitic layers. The S-type granitic rocks would, on the other hand, occur in the regions consisting of immature crust without basaltic layer (e. g. southern part of the Outer Zone of Southwest Japan), and in the regions of crust exceeding 50km in thickness such as continental margins (e. g. western Bolivia) and continent-continent collision zone (e. g. High Himalaya).

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Tholeiitic basalts characterized by very high TiO₂ contents have been found in the northeast Japan arc. These basalts (the Motokozawa basalts) occur as lavas and minor dikes in the lower Miocene Motokozawa Formation which is distributed in the eastern part of Tochigi Prefecture, Northeast Japan.
The Motokozawa basalts are uniform, non-porphyritic and subophitic in texture. The essential constituent minerals are plagioclase, clinopyroxenes (augite, ferroaugite, subcalcic augite and pigeonite) and Fe-Ti oxides. Fe-Ti oxides occur sporadically as euhedral crystals (3.8-6.4 modal%) and also as very fine grained crystals in the mesostasis. The Motokozawa basalts are high alkali tholeiite or quartz tholeiite according to the classification of Kuno (1968b) and Yoder and Tilley (1962), respectively.
The quartz-normative tholeiites having high TiO₂, FeO^* (FeO+0.9 Fe₂O₃) and low K₂O contents are predominantly found in the east Pacific Ocean floor, though less abundantly in other ocean floors.
Discussions and considerations on the genesis of ocean floor tholeiites with high TiO₂ and FeO_* contents suggest that the Motokozawa basalts may not be produced by the fractional crystallization from the primary magma having low TiO₂ and K₂O contents. One of the reasonable explanations for the genesis of the Motokozawa basalts is the fractional crystallization from the primary TiO₂-rich, K₂O-poor magma generated in the upper mantle which had been previously enriched in Ti and depleted in K through a preceded partial melting under hydrous conditions.

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In central-north Kyushu, a large volume of Pliocene-Quaternary volcanic rocks are distributed in and around the east-west elongated graben (40×30 km), which is considered to be a volcanotectonic depression (VTD). The radiometric ages of the volcanic rocks are isochronally zonated in concordant with the outline of the VTD, so that the ages increase from the center to the rim of the VTD. In this study, K-Ar ages were determined upon four volcanic rocks from the northern rim of the VTD. K-Ar ages of the volcanic rocks from the Hikosan area (northwest part of the VTD) were determined as 5.0±0.4, 4.0±0.2 and 4.7±0.3 Ma, which show close agreement with the respective FT dates (Watanabe et al., in press). In the Yamaga area (northeast part of the VTD), the andesite lava from the Yabakei Formation, whose FT age is reported as 12.1 Ma (Hayashi et al., 1983), was dated by K-Ar method as 5.7±0.3 Ma. The K-Ar ages of the Usa Group which is overlain by the Yabakei Formation near the Yamaga area show 4.8±0.4, 5.3±0.3 and 4.9±1.1 Ma (Kamata, 1985b). Accordingly the previous FT age (12.1 Ma) for the Yabakei Formation is apparently too old, which may account for corrections made for thermal alteration of the specimen and/or contamination of accidental particles. On the other hand, the K-Ar age (5.7 Ma) is considered to be close to the eruption age of the Yabakei Formation in this area. These results indicate that the oldest volcanic rocks, which are distributed on the rim of the VTD, were erupted 5-6 Ma ago. Therefore it is suggested that the VTD has been formed since 5-6 Ma ago in centralnorth Kyushu.

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The Pliocene Futamata and Tomuraushi pyroclastic flow deposits and their granitic inclusions in central Hokkaido, form a series of volcano-plutonic association. The newly obtained K-Ar ages of the granitic inclusions are 1.1-1.2 Ma for whole rocks. These K-Ar ages are much younger than the ages which are expected from stratigraphic correlation. This discrepancy in age suggests loss of radiogenic ⁴⁰Ar from the pyroclastic flow deposits and their granitic inclusions during thermal event of subsequent volcanism.

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