南部阿武隈山地,宮本複合岩体の岩型区分

抄録

Geological and petrological study of the Miyamoto igneous complex in the south Abukuma mountains revealed a division of the following six rock types; ultrabasic rocks, gabbroic rocks (Inubotoke-, Mikabu-, Ishigami-types) and granitic rocks (Arizane- and Domeki-types).
The Arizane-type rocks, the main constituent of the complex, are mostly composed of tonalite. The Domeki-type rocks, the next abundant rock type, consist chiefly of adamellite, The Ishigami-type rocks, though subordinate in volume, range from gabbro to tonalite. The intrusive sequence among the three rock types is the Ishigami, Arizane and Domeki. Thus the composition of intruded magma became more felsic and K-rich toward the later stage.
The Miyamoto igneous complex is a crudely zoned pluton containing a gabbroic margin. Each rock type has its own petrographical characteristic and exhibits unique compositional variation trend which are easily distinguished from the other types by modal and whole-rock chemical compositions. The field occurrances and petrographical data indicate that the zonal structure of the complex was not formed by in-situ differentiation from a single primary magma, but was formed by succesive intrusions of magmas of different origins.