Studied is metachert, which has been subjected to the low P/T type Ryoke regional metamorphism, in central Kinki, Japan. Deformed radiolarian remains included in metachert indicate that the deformation during the metamorphism seems to be uniaxial and the maximum extensional direction is parallel to the principal lineation, as already demonstrated in the Sanbagawa metamorphic terrane, forming “a pair” with the Ryoke metamorphic terrane. The grain size paleopiezometer (Mercier et al., 1977) and the dislocation density paleopiezometer (McCormick, 1977) of quartz give about 75 MPa and 40 MPa of the flow stress in the low metamorphic grade zone and about 10 MPa and 8 MPa in the high grade zone, respectively. The natures of the paired metamorphic belts seem to be very similar in such rheological aspects as the apparent uniaxial strain of fossils and the magnitude of differential stress.

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The Hongu-san area of the Ryoke metamorphic belt consists of schists, gneisses and granites. Schists and gneisses have been divided into three progressive zones (andalusite, sillimante and sillimanite-K-feldspar zones) and one contact zone (andalusite-K-feldspar zone), based on pelitic mineral assemblages.
The obliquities of 75 K-feldspars and infrared data of 64 K-feldspars from quartzfeldspathic rocks of these zones and granite are presented. These data indicate that monoclinic K-feldspar was formed by regional metamorphism in three progressive zones, where the inversion of triclinic to monoclinic K-feldspar might have occurred under the condition below the andalusite zone. In the contact zone K-feldspars showing broad 131 peak (types II and III) and more ordered infrared absorption have resulted from a granite intrusion.

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The Kamuikotan gorge area of the Kamuikotan metamorphic belt, west of Asahikawa, Hokkaido, is underlain by the Kamuikotan metamorphic rocks and serpentinite. This area is divided into two zones, the central and green rock zones, respectively. The metamorphic rocks of the central zone are basic and pelitic schists of the jadeite-glaucophane schist facies, retrograded in the lawsonite-albite facies, and those of the green rock zone are of the lawsonite-albite facies retrograded in the greenschist facies. No simple metamorphic zonation is possible in the Kamuikotan gorge area, because tectonic disturbance caused by the intrusion of serpentinite resulted in the mix-up of the rocks formed at different conditions, even though this area could roughly be divided into two zones.
The mineralogy of alkali pyroxenes with the emphasis on the retrograde change of chemistry and texture are described in some detail.

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Large amounts of mafic igneous rocks are distributed in the Mesozoic formations of Amami-Oshima, Ryukyu Islands. Especially, the Yuwan Formation belonging to the upper Jurassic to lower Cretaceous contains large amounts of allochthones, and mafic rocks are intercalated in and/or intrude into allochthones and autochthonous part. Camptonite and spessartite occur in the Yuwan Formation as sheet and dyke forms. Camptonite is composed mainly of titan-augite, kaersutite, anorthoclase, plagioclase, and in parts aegirineaugite. Chief constituents of spessartite is Ti-rich pargasite, plagioclase, K-feldspar and chlorite after biotite. Chemically, camptonite belongs to typical alkali rock series of nenormative and is characteristically rich in Ti0₂, whereas spessartite is Q-normative. Titanaugite and kaersutite in camptonite have a wide compositional range. Titan-augite in camptonite shows the ranges of Mg/(Mg+Fe)=0.77-0.17, Al^IV=0.22-0.51, Al^VI=0.02-0, 13 and Ti=0.09-0.20, and shows hourglass structure of paler-coloured sector being rich in Mg and of deeper-coloured sector rich in Ti, Fe and Al^VI. Ti/Al^IV ratio of titan-augite are plotted between 1/2 and 1/3 lines. Compositional trend of titan-augite indicates substitutions of Ti+2Al for (Mg, Fe²⁺)+2Si and Fe²⁺+Ti⁴⁺+2Al for 2Mg+2Si. Aegirine-augite is the last of the mafic minerals to be crystallized, and shows wide ranges of Al=0.04-0.10, Fe³⁺=0.13-0.68, Fe²⁺=0.17-0.73, Ca=0.20-0.47, Na=0.39-0.82, whereas Mg is very low throughout wide compositional range of other components. The Mg-Fe²⁺-Na ratios of pyroxene in camptonite show a trend under extremely low f_O2, condition similar to that of Ilimaussaq pyroxene. Kaersutite also has strong compositional zones from core to rim, showing distinct decrease of Mg and Ti, and increase of Fe, Al^VI and Mn.
It is suggested from the chemical characteristics of camptonite poor in SiO₂ and extremely rich in TiO₂ and alkalies that the situation of present area may have been oceanic islands or sea mounts during the late Jurassic to early Cretaceous.

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K-Ar age determinations were carried out on 19 homblendes and 4 biotites from 9 granitic masses and two metamorphic rocks in the southern Abukuma Plateau, Northeast Japan. Hornblende ages for granitic rocks range from 96.4 to 119 Ma and are apparently not correlated with area or mass. Biotites show a limited age range of 96.1-97.8 Ma. The variation in hornblende age is attributed to the difference in cooling rate of granitic rocks. Hornblende ages for the Gosaisho and Tamadare metamorphic rocks are 115 and 103 Ma, respectively, and nearly equal to those for the adjacent granites.
No old ages were found on hornblendes from the Ishikawa, Miyamoto and Samegawa masses, which constitute the older type granites and gave Rb-Sr whole-rock ages of about 400 Ma. This may impose a severe constraint on the thermal history of the older type granites.

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