Genesis of the Heneshk IOCG deposit, Iran: magnetite mineral chemistry and sulfur isotope
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Geosciences Journal
GJ
Genesis of the Heneshk IOCG deposit, Iran: magnetite mineral chemistry and sulfur isotope Morteza Mizan1* and Xiao-Wen Huang2 1
Department of Earth Sciences, College of Sciences, Shiraz University, Shiraz, Iran State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
2
ABSTRACT: The Heneshk Fe ± Cu deposit, a metamorphosed IOCG (Iron Oxide Copper Gold) is situated in Sanandaj–Sirjan Zone, SW Iran. Mineralization occurs as two stratabound ‘U’ shape ore bodies, hosted by a meta-dolomite member of a metamorphic complex. The ore and gangue minerals comprise magnetite, chalcopyrite, hematite, martite, mushketovite, pyrite, barite, calcite, dolomite, and quartz. The successive mineral assemblage formed in the five paragenetic stages (I to V) during an ongoing deformation regime from the plastic to the brittle deformation regime. The mineralization stages comprise stage I, III, and IV. Stage I–III and IV formed in the plastic and the brittle deformation regime by the metamorphic processes in a shear zone, respectively. The concomitant alteration products of these stages comprise sodic, Fe, K, hydrolytic and silicification. The sodic and Fe alterations occur as a pre-mineralization stage and each mineralization stage is accompanied by K and hydrolytic alterations. A late barite-calcite-quartz assemblage (stage V) overprinted on the previous stages (I to IV). Stage I mineralization formed at a depth of ~10 km and temperature of ~300 °C (a high pressure-low temperature environment). The partitioning and substitution of the Mg, Al, Ti, Ni, Cr, Mn, Si, and Zn elements increased in this relatively higher pressure environment cause of the highest concentrations of the Al, Ti, Ni, Cr, and Zn, in comparison with metamorphic magnetite. The mineral chemistry of the Heneshk magnetite (average elemental concentrations) is in accordance with the metamorphic magnetite and can consider as a pure magnetite with the low elemental concentration. Also, the δ34SH2S Heneshk mineralized fluid ranges between 39.8 to 40.6‰, indicating the contribution of the paleo-evaporates. The pleo-evaporates leached from the older strata during metamorphism, and their precipitation in the form of the sulfide minerals occurs through the TSR (Thermochemical Sulfate Reduction) mechanism. Key words: Heneshk IOCG, metamorphic magnetite, magnetite mineral chemistry, elemental substitutions, paleo-evaporates Manuscript received November 17, 2018; Manuscript accepted July 9, 2019
1. INTRODUCTION Heneshk Fe ± Cu deposit, economically one of the largest iron deposits of Dehbid district, with controversial genetic aspects, is located approximately 4 km north-east and 4.8 km south-east of the Heneshk and Goushti villages respectively (Fig. 1b). Fe and Cu metals merely occur as magnetite-hematite and chalcopyrite minerals. First assessment of the Heneshk mine went back to 1977 by Alric and Virlogeus, proposed a metamorphic origin. Later, Rajabzadeh and Rasti (2017) proposed
