Rb-Sr whole-rock and K-Ar mineral ages of granitic rocks in Japan.

Cretaceous Research: A New Constraint on the Paleostress Regime of Southwest Japan Based on Microfabric Analysis of a Granitic Pluton

“…Considering the ages reported for the host rock [7][8][9], the dike swarm was emplaced in the final stage of the Late Cretaceous extensive igneous activity, as Kinoshita [26] interpreted as resulting from subduction of oceanic plates' divergent margin. Oikawa et al [24] stated that their K-Ar age for the andesitic dike provides the upper limit of the intrusion event.…”

“…The pluton has yielded a CHIME monazite age of 68.3 ± 1.8 Ma [7] and whole-rock Rb-Sr ages of 72.3 ± 3.9 Ma [8] and 68.2 ± 1.1 Ma [9]. It is a stock, 14 km × 12 km in areal extent [10], having a vertical thickness of at least 1.5 km based on borehole investigations by JAEA.…”

Groundwater chemistry and fracture mineralogy in the basement granitic rock in the Tono uranium mine area, Gifu Prefecture, Japan. Groundwater composition, Eh evolution analysis by fracture filling minerals.

“…The Tono uranium mine is located in the Tono district, Gifu, in the central part of Japan ( Fig. 1 The length of boreholes: 500 m (DH-1, DH-2 and DH-4), 840 m (DH 20 Ma) and the Seto Group (0.7-5 Ma), with a combined total thickness of less than 200 m (Itoigawa, 1974), unconformably overlying the Toki granite (72.3± Ma; Shibata and Ishihara, 1979). The Toki granite consists of medium to coarse-grained biotite granite and medium-grained homblende-biotite porphyry, and is partly intruded by quartz porphyry and aplite dikes.…”

Isotopic ages of the Pankenushi olivine gabbro complex, Hidaka magmatic belt, central Hokkaido, Japan: implications for the tectonic setting of Hidaka magmatism

“…Location 1: Magarisawa tonalite (Shibata et al, 1984;Kemp et al, 2007); locations 2 and 3: Pankenushi gabbro (2: Maeda et al, 1990 andKemp et al, 2007;3: Maeda et al, this study, underlined ages); and location 4: Memurodake diorite . Ages reported for the Nissho Toge granite are shown on this map (Shibata and Ishihara, 1979;Ishihara and Terashima, 1985;Kuramoto et al, in press). Simplified geological boundaries are also shown.…”

“…16.6 0.7 Ma K-Ar Terashima, 1985 17.3 Ma Shibata andIshihara, 1979 Rb Table 1 30 kg Komatsu et al, , 1994. Abbreviations: Chl = chlorite, Ms = muscovite, Bt = biotite, Grt = garnet, Crd = cordierite, Opx = orthopyroxene.…”