Geochemical characteristics of igneous rocks associated with Baghu gold deposit in the Neotethyan Torud-Chah Shirin segment, Northern Iran

摘要

The Baghu gold deposit, hosted by a granitoid stock as well as volcanic rocks, is located in Northern Iran. The igneous rocks consist of granodiorite and granite as well as volcanic rocks, such as basaltic andesite and andesite, which are cut by dioritic dykes. The igneous rocks have metaluminous, high K calc-alkaline, and island-arc signatures, characterized by enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSEs). Zircon separates yield U-Pb ages of 47, 43, and 38 Ma for the volcanics, granitoid rocks, and dyke, respectively, indicating that the magmatism associated with gold-copper mineralization occurred during the Eocene. The low Ba/Th, Th/Nb, Ba/La, and Th/Yb ratios in igneous rocks indicate that their mantle source was not likely modified by subduction activity. A comparison of La/Sm against La (ppm), similar Th/Nb and Th/Yb, and average (La/Yb)(n) ratios to the crust and lower continental crust (LCC) suggests that the magmatism in the Baghu was likely associated with partial melting of juvenile lower crust, induced by north-westward subduction of the Neo-Tethys oceanic lithosphere in an extensional setting.