On the so-called metamorphosed calcareous concretions in felsic metamorphic rocks which lie in the basic rocks at the upstream of Horoman river, Hidaka province

Abstract

The writer discusses the origin of the so-called metamorphosed calcareous concretions in felsic metamorphic rocks in Hidaka province. The metamorphosed calcareous concretions form originally at the crest of the microfolding, at the inner part of the semicircular mylonitic arc, or at the mylonitic part, of biotite hornfels in a small scale. In the metamorphosed calcareous concretions, basic plagioclase, hornblende, diopside, vesuvianite, calcite, ilmenite and ore generally occur accopanying the concentration and the dispersion of biotite of biotite hornfels. He concludes that the origin is attributed to neither of addition of materials from the surrounding coarse metamorphic rocks or from basic rocks, nor to the original one in sedimentary rocks, but to the metamorphic differentiation which take place in biotite hornfels at the time of the mechanical movement of its own.