Molybdenite Re-Os dating, petrology, and geochemistry of granitoids in the Bondar Hanza porphyry Cu deposit (Urumieh-Dokhtar magmatic arc), Iran: Insight into petrogenesis, mineralization, and tectonic setting

摘要

The Bondar Hanza porphyry Cu deposit, hosted by a granitoid stock, is located 120 km south of Kerman city in the elongated NW-SE trending Urumieh-Dokhtar magmatic arc (UDMA), Iran. The granitoid stock is a multiphase intrusive body, 2 km(2) in surface area, which comprises microdiorite-microquartz diorite and granite-granodiorite. Petrological and geochemical analyses show that granitoids are peraluminous, magnesian, calcic to alkali-calcic, and non-adakitic intrusions characterized by negative Eu* anomalies. Thermobarometric and oxygen fugacity calculations indicate that magma emplacement occurred at 719-784 degrees C, <100 MPa, and at a log fO(2) of NNO +1.6 to +3.2. Sulphur isotopic composition of sulphide minerals (delta S-34 = 5.0-6.8 parts per thousand) are similar to other porphyry Cu deposits worldwide. Molybdenite separates yield Re-Os ages of 28.22-28.03 Ma, indicating that the Cu mineralization and associated magmatism occurred during the Oligocene. The Bondar Hanza is one of the several granitoids from small porphyry Cu deposits in the UDMA that is related to island arc sub-productive granitoids. It seems that the largest ore-hosting porphyry systems within the UDMA are generally restricted to Miocene intrusions with adakitic affinity (e.g., Sarcheshmeh granitoids) and that the temporally discrete non-adakitic magmatic systems are sub-productive to barren. These data are interpreted to show that magmatism in the Bondar Hanza region was likely associated with partial melting of juvenile lower crust induced by north-eastward subduction of the Neo-Tethys oceanic lithosphere.