In order to clarify the temporal and spatial patterns in arc volcanism, 55 K-Ar ages of volcanic rocks from 17 volcanoes in Shin-etsu Highland, central Japan were determined. In addition, life spans, volume of erupted materials and eruption rates of each volcano were estimated. Graphical analysis demonstrates that volume of ejecta varies proportionately with both life span and eruption rate, and that there is no significant correlation between eruption rate and distance from the volcanic front.
The life span of each volcano in this Highland is less than 0.6 m. y. In the central Shiga and southern Asama area, the volcanism started at 1 Ma and is still active. However the former had a peak in the activity at around 0.5 Ma, while the latter is apparently most intense at present. Northern Kenashi area has the volcanism without peak in 1.7-0.2 Ma, though the activity within a volcanic cluster or chain in central Japan lasts generally for 1 m. y. or less with a peak.

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Early Cretaceous Orikabe plutonic complex, in South Kitakami Mountains, Northeast Japan, consists of two plutons: Main and North. The Main pluton is divided into three rock types: Tokusenjo, Orikabe, and Sasamori. In the Orikabe type, three subtypes 0-1, 0-2 and 0-3 are recognized. The North pluton is also composed of three rock types: Tsuwamonozawa, Tamogi and Murone. The rocks of the Tokusenjo, Orikabe and Murone types are Kf ?? Qz, while those of the Sasamori and Tamogi types are Qz>Kf.
The Main pluton makes up a zoned pluton having more felsic composition outward and a little younger age inward. From the outside to the center of the pluton, rock types are arranged as follows: Tokusenjo, 0-1, 0-2, 0-3, and Sasamori. At each boundary of the rock types and subtypes, rock facies and modal composition change sharply, so that main mechanism of the formation of the zonal structure is considered due to multiple stage of the intrusion. The Tokusenjo type and Orikabe type might have been derived from the same original magma. But the Sasamori type had a different crystallization history from the Orikabe type, because the Sasamori type is characterized by euhedral hornblende and is lower in K, Rb, Ce, Nb, F than the Orikabe type in the same SiO₂containing rocks.
Major and trace element abundances of the Tokusenjo-type gabbro are similar to those of basalt of Niitsuki Formation, erupted a little earlier than the intrusion of the Orikabe complex. They are produced from the same origin of magmas, which have chemical characteristics of calcalkali basaltic magma of island arc or continental margin.

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Rb-Sr and Sm-Nd isotopic compositions and REE abundances were measured on the Gray granite in the upper Kubusu River area, Hida mountains. The Gray granite is grouped into two based on the Rb-Sr age. The majority are plotted along an isochron giving an age of about 500 Ma, which is assumed to be the age of emplacement for the Gray granite. The remaining samples of the Gray granite give a Rb-Sr age of about 180 Ma, and they may be correlated to the Funatsu granitic rocks.
The Nd model ages for the Gray granite are also divided into two; about 180 Ma and 1300-1500 Ma in harmony with Rb-Sr data. The older Gray granite is probably originated in the late Precambrian. REE patterns of the Gray granite are characterized by a marked enrichment in light REE, although there is a difference in abundance between the older and younger samples.

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REE and trace metals in some GSJ granitoids reference samples were determined by means of inductively coupled argon plasma/optical emission spectrophotometer (ICP). Samples are dissoluted with a mixed acid solution of H₂SO₄+HCIO₄+HNO₃+HF. The separation and preconcentration of the REE and trace metals from 1g sample, and the conditions of the spectrometry follow Tagiri and Fujinawa's method. REE and trace metal analyses of JG-1 show that the H, SO, dissolution method is much suitable for REE analyses of granitoids, but not good for Ba, Sc and Zr analyses. Comparing the results of the H₂SO₄ dissolution method with the non-H₂SO₄ method, it is concluded that the most important carrier of REE in granitoids and pelitic gneisses is REE minerals, such as monazite and xenotime. More than 50% of REE in granitoids is generally contained in REE minerals.

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