On the use of major and trace elements composition of pyroxene and amphibole in the genesis of Boroujerd quartz-diorite

Boroujerd plutonic complex (granodiorite, quartz-diorite, and granite) is located in northern Sanandaj-Sirjan Zone. In this study, abundance of trace elements in clinopyroxene and amphibole from the quartz-diorite is measured and then composition of the parental melt of the minerals calculated. The melts are chemically compared with: 1- whole rock composition of the host quartz-diorite, and 2- quartz-diorite and ultramafic rock from the neighboring Aligoodarz plutonic complex. Geochemical modelings indicate that a melt chemically comparable with Aligoodarz quartz-diorite, affected by concurrent ultramafic rock assimilation and fractional crystallization to generate a new evolved melt from which pyroxene and amphibole crystallized. Then this melt mixed with Aligoodarz quartz-dioritic melt to generate a new melt that is comparable with Boroujerd quartz-diorite. The role that ultramafic rocks played in genesis of the Boroujerd quartz-diorite indicates that despite scarcity of ultramafic rocks on the surface, they are much more voluminous at depth.