A Geological and Petrological Study on Plutonic and Metamorphic Rocks in the Southern Abukuma Mountains

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Plutonic and metamorphic rocks in the Abukuma mountains were studied. schistose tonalite, granodioritic rocks and Takanuki metamorphic rocks are distributed in the Samegawa to Hanawa area. These rocks distributing near the Tanakura tectionic line show cataclastic features, such as granulation, elongation and wavy extinction of quartz, bent cleavace and wavy extinction of plagioclase, and kink band and wavy extinction of biotite. The more close to the Tanakura tectionic line, the more intense the cataclastic features are, suggesting that the tectionic line has been active since about 100 ma ago. Partial melting of amphibolite and formation of gabbroic to trondhjemitic veins are observed in the Aakanuki amphibolite in an contact aureole of a dioritic pluton. the host amphibolite is composed of fine grain hornblende + plagioclase (An 70-80) + ilmenite and poor in SiO_2 (-45%), Na_2O and K_2O the veins continuously change their texture, Mineralogy and chemistry from a gabbroic part (SiO_2-45%) to dioritic, and finally to tonalitic or trondhjemitic (SiO_2-70%) Parts.Granitic rocks in the uzumine area, one of pegmatite-producing spots in the central Abukuma mountains are described. the younger porphyritic two-mica granitic rocks which are considered to be intimately related with pegmatite containing rare element minerals, such as euxenite, monazite and xenotime are the highest in SiO_2 content and exhibit s-type like petrological features.