Whole-rock and mineral geochemistry of magmatic rocks from the polymetallic Jizvan ore deposit, Tarom- Hashtjin Metallogenic Province, NW Iran: Implications for petrogenesis and tectonic setting

The Jizvan polymetallic ore deposit in northwestern Iran is formed by the intrusion of Oligocene igneous bodies into the Eocene pyroclastic-volcanic rocks. The Eocene volcanic rocks are basaltic trachyandesite to trachyandesite with a calc-alkaline to shoshonitic character. Intrusive and volcanic rocks from the Oligocene fall into the syenite and phonolite to trachyte domains, respectively, and are shoshonitic. The multi-element diagrams of magmatic rocks, normalized for the primitive mantle, show similar patterns to the post-collisional magmas, with some fractionation processes. The chondrite-normalized REE patterns for Eocene volcanic rocks resemble those of oceanic island basalts. The geochemical indicators for trace elements and rare earths show that the magmatic rocks were formed by partial melting of an enriched mantle source containing spinel and garnet. The diagrams identifying the tectonic setting show the formation of studied igneous rocks in the continental and post-collisional arcs. The data from microprobe analysis show that the formation temperature of biotite in syenite ranges from 650 to 850 °C, on the basis of the Ti versus Mg/(Mg+Fe) diagram. Thermobarometry, which is based on the composition of clinopyroxene in syenite, reveals that the formation temperature and pressure of this mineral range from 1030 to 1191 °C and from 1.26 to 13.27 kbar, respectively. The AlVI+2Ti+Cr versus Na+AlIV diagram shows the formation of clinopyroxene under conditions of high oxygen fugacity.