Forming process of Utsuno volcanic rock in backbone range of NE Japan

Abstract

Mid Miocene volcanic rock (Utsuno volcanic rock) that is occurred in backbone range of NE Japan was observed to understand that forming process by OM, SEM-EDX, TEM. The phenocrysts of augite, orthopyroxene and plagioclase were crystallized at 1100 degrees C, >10kbar in the magma. After that, the magma mixed another Fe-rich magma and augite and orthopyroxene were altered to pigeonite at 1100 degrees C, 5-<10 kbar. In addition, plagioclase was resolved and made reveres zoning rim. Finally, rapidly erupted to the near the surface.