Geochemistry, petrology and U-Pb geochronology of Ghazan mafic-ultramafic intrusion, NW Iran

Ghazan mafic-ultramafic intrusive is a small igneous body at the extremity of NW of Sanandaj-Sirjan zone in the NW of Iran، intruded into the early Paleozoic sedimentary rocks. This body includes non-mineralized mafic and mineralized ultramafic part (containing Fe-Ti oxides). The mafic rocks are composed mainly of pegmatite gabbro to micro gabbro، metagabbro and anorthosite، with a simple mineral assemblage (plagioclase، clinopyroxene، orthopyroxene، ilmenite). The ultramafic rocks include pyroxenite and wherlite (with high proportion of ilmenite and titanomagnetite) in accompany by large to small blocks of pure Fe-Ti oxide are widespread in the area. The ultramafic part is located within the intrusion and enclosed by mafic rocks. Based on the results of chemical analyses، the primary magma of mafic-ultramafic rocks، derived from a mantle source. During magma ascent the composition of magma has been changed from alkaline to sub-alkaline. U-Pb dating، of a primary and magmatic zircon، gives an age of 299 Ma and dating on metamorphic and inherited zircons shows maximum age of 541 Ma. The younger age represents the the Upper Paleozoic plutonism in the northern part of the Sanandaj-Sirjan zone. The older ages related to the Precambrian basement rocks or older basement rocks on the way of magma، which are incorporated in the magma as exnocryst. The greenschist facies metamorphism، high-temperature deformation as well as altered rocks are widely observed in the area.