Schist xenoliths in ultrabasic body accompanied with Kurosegawa tectonic zone in eastern Shikoku and their K-Ar ages

Xenoliths in the Kitomyo ultrabasic body (NS-2.5 km, EW-4.5 km in width) in Kizawa village, Tokushima Prefecture, are composed mainly of amphibolites, psammitic and basic schists with albite spot, quartzose schists, greenstones and sedimentary rocks, the latter two being derived from country rocks. The mode of occurrence, petrographic features and chemical analyses of garnet, chlorite and amphiboles of the metamorphic rocks are described. Petrographically, the low grade schist xenoliths are quite similar to basic and psammitic schist of the Sanbagawa metamorphic belt, and they are distinct from the Terano metamorphic rocks. But the K-Ar ages of muscovites in psammitic and quartzose schist with albite spot are 402 m.y. and 405 m.y. respectively. The significance of the presence of Sanbagawa-type schists in the ultrabasic body of the Kurosegawa tectonic zone is briefly discussed. (author)