Mangmatic differentiation of the Himekami pluton in the northwest Kitakami Mountains

Abstract

Two kinds of magma are probably derived from the initial magma in the Himekami pluton. The content of magnesium is the major difference between the two magmas. They produce the present four rock groups through two different processes in which the ratio of FeO to FeO^* decreased, or did not change largely. Both processes are well explained with the removal of cumulates in some combinations of olivine, pyroxenes, plagioclase, magnetite, biotite and hornblende.
The North pluton was differentiated through the process in which the ratio of FeO to FeO^* decreased. The Shiroishi pluton is the latest-stage product of the differentiation.