Many small granitic bodies covered by Neogene and Quaternary formations are sporadically distributed in the southeastern area of Fukuoka Prefecture and Kunisaki Peninsula, Southwest Japan. These are mostly of Late Mesozoic in age and composed of granodiorite to tonalite, biotite granite and two-mica granite with weak foliation or massive appearance. Small gneissose metamorphic rock masses are found in intimate association with these granitic rocks.
In chemical composition, these granitic rocks have the similarity with a large part of the granites in North Kyushu region in high-content of strontium, whereas the fairly distinct differences can be seen in K₂O/Na₂O and Fe₂O, /FeO ratios between two. The former is lower in these ratios than the latter.
The similar small granitic bodies can be found also in the Kunisaki Peninsula, north part of Ohita Prefecture. The granitic rocks of this peninsula also show the feature of high-content of strontium, although they are distinguished by higher values in K₂O/Na₂O and Fe₂O, /FeO ratios than the granitic rocks from the southeastern area of Fukuoka Prefecture. They are considered to belong to the Ryoke zone together with the associated gneissose metamorphic rocks character-ized by containing fibrolite and almandine garnet.
From these facts and textural and mineralogical data on the associated metamorphic rocks, the granitic rocks of the studied area are divided into four zones trending from NE to SW, as shown in Fig. 10. The southernmost zone is composed of biotite granite to granodiorite of massive appearance, while the next north side zone is distinguished by the strongly foliated granodiorite to tonalite and associated gneissose metamorphic rocks. Massive and weakly foliated texture of the component granites (granodiorite to tonalite and two-mica granite) and associated gneiss are the characteristic feature of the 3 rd zone from the south, although the southern half area of this zone is almost devoid of outcrop of basement rocks, excepting small stock-like bodies of muscovite granite. The northernmost zone consists of various types of granitic rocks. Among them, the broadest area is occupied by the granodiorite to tonalite (Irahara granodiorite). The associated pelitic schist is thermally metamorphosed to hornfels consisting of biotite, muscovite, plagioclase, K-feldspar, cordierite and andalusite partly replaced by sillimanite. Above data suggest the similality of the granites in the northernmost zone to the Itoshima granodiorite in North Kyushu. The other three zones have similar features with the Ryoke Zone, but there are some discrepancies especially in chemical features. Further detailed investigation will be needed.

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The late Cretaceous Takatori tungsten deposit, located in the Yamizo Mountains of Japan, is hosted by sedimentary rocks of the Mesozoic Yamizo Group. The degree of graphitization of carbonaceous material in the sedimentary rocks has been used to examine the thermal influence of the tungsten mineralization. Several hundred samples from surface outcrops (n=392) covering an area of 400km², together with drill cores (n=134), have been analyzed. The degree of graphitization of carbonaceous material separated from the rock samples was measured by X-ray diffraction, whic is given by the GD value, defined as 100x(d₀₀₂-3.7)/log(Lc(002)/1, 000); where Lc (002) and d002 are the crystallite thickness and the lattice spacing, respectively. The GD value is set as 1, 000 when Lc (002) exceed 1, 000. An empirical calibration of temperature for the GD parameter elsewhere suggests an approximate temperature of 400°C for a GD value of 30.
Most of the samples from the surface outcrops have GD values around 14. In the southern part of the study area near a local granite pluton, high GD values have been measured indicating contact metamorphic effects. In an area covering about 2.5×1.5km surrounding the Takatori tungsten deposit, GD values are greater than 30. Moreover, GD values up to 1, 000 are found even closer to the deposit. The steep gradient of GD values associated with the Takatori deposit is in contrast to the shallow GD gradient related to the contact metamorphic aureole found in the southern part of the study area. High temperature hydrothermal fluids which formed the Takatori tungsten deposit are considered to be responsible for the elevated GD values around the deposit. The heat associated with hydrothermal activity can be transferred by infiltration of such fluids into the Yamizo Group. This study shows that an area affected by hydrothermal fluid can be detected by GD data with an appropriate sampling density. Therefore the degree of graphitiza-tion can be utilized for mineral exploration.

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The dacitic lava dome group (DLDG), located on the NNW and SSE flanks of Rishiri volcano, northern Hokkaido, has been considered to be the Tertiary basement or early volcanic products of the Rishiri volcano. Newly obtained K-Ar ages of the rocks from the DLDG are 0.133±0.008 Ma (Peshimisaki lava dome), 0.078±0.005 Ma (Fujino lava dome) and <0.1 Ma (Ishiyama lava dome). These ages suggest that the DLDG are the products of flank eruptions during the early stage of activity of Rishiri volcano, and that the structure of the volcanic eddifice must be revised from those of previous studies. In addition, the chemical compositions of volcanic rocks from adjacent regions has changed from low-K tholeiitic during the Tertiary to alkalic (high Na₂0) during the Quaternary.

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