Stndy of felsic metamorphic rock and its associated inclusion in gabbro-diorite of Horoman river, Hidaka province, Hokkaido

Abstract

At the up-stream of the Horoman river, Hidaka province, felsic metamorphic rocks which are mainly composed of biotite hornfels, biotite migmatite, tonalitic migmatite and coarse biotite diorite are enclosed in gabbro-diorite on a small scale. The biotite hornfels is not homogeneous and has clots of plagioclase-biotite rock with sub-glomeroporphylitic texture of biotite. In biotite and tonalite migmatites, the sub-igneous textures are recognized, and in their inclusions such as plagioclase-biotite or plagioclase-hornblende rocks the sub-diabase texture are also observed. The migmatites, coarse biotite diorite, and their inclusions are considered to be the products of the metamorphism which differentiated from biotite hornfelsic rocks in the early and middle stages of the mechanical movement. The gabbro-diorite has the relict texture of the migmatite and it seems that the gabbro-diorite was intruded before the stage of the migmatization. No contact effects are found between the felsic metamorphic rock and the gabbro-diorite.