Geochemical discrimination of intrusions in the Choran CuAu deposit, Iran, using silicate chemistry

Abstract The Choran Cu Au deposit is located 70 km of Bardsir in the southern part of Urumieh-Dokhtar magmatic belt (UDMB). In this area, mineralization is associated with Oligocene –Miocene quartz diorite and granodiorite intrusions emplaced within Eocene volcanic–pyroclastic – sedimentary sequences. Main hydrothermal alterations in the Choran region include sodic-potassic and potassic as well as phyllic, alunite and kaolinite which extended mostly in the granodiorite. Mineralizations at the Choran deposit involve pyrite, arsenopyrite, chalcopyrite, chalcocite, covellite and sphalerite. The composition of the plagioclase in the granodiorite and quartz diorite rocks ranges from albite (66.8 to 48.7) and (64.8 to 51.4) respectively. Also, Al/(Ca + Na + K) ratios of plagioclase in granodiorite samples (average; 1.50) are higher than that of quartz diorite intrusions (average; 1.33) which is analogous to those reported previously for mineralized porphyry systems. All studied primary and re-equilibrated biotites are collectively clustered in the Mg-biotite field. However, based on the log (XMg/XFe) versus log (XF/XOH) of biotite, granodiorite units are associated with I-type moderately crustal contaminated (I-MC) suite, whereas quartz diorite biotites represent I-type weakly crustal contaminated (I-WC) character. Comparison of biotite halogen contents indicates that F and Cl values increase from quartz diorite to granodiorite intrusions. Importantly, biotite thermometry of granodiorite and quartz diorite samples indicate temperatures of