Abstract
Abstract The Muratdere Cu-Mo (Au) porphyry deposit in western Turkey contains elevated levels of rhenium and is hosted within granodioritic intrusions into an ophiolitic mélange sequence in the Anatolian belt. The deposit contains several stages of mineralization: early microfracture-hosted molybdenite and chalcopyrite, followed by a quartz-pyrite-chalcopyrite vein set associated with Cu-Au grade, a quartz-chalcopyrite-pyrite-molybdenite vein set associated with Cu-Mo-Re grade, and a later polymetallic quartz-barite-sphalerite-galena-pyrite vein set. The rhenium in Muratdere is hosted within two generations of molybdenite: early microfracture-hosted molybdenite and later vein-hosted molybdenite. In situ laser ablation-inductively coupled plasma-mass spectrometry analysis of sulfides shows that the later molybdenite has significantly higher concentrations of Re (average 1,124 ppm, σ = 730 ppm, n = 43) than the early microfracture-hosted molybdenite (average 566 ppm, σ = 423 ppm, n = 28). Pyrite crystals associated with the Re-rich molybdenite have higher Co and As concentrations than those in other vein sets, with Au associated with As. The microfracture-hosted sulfides have δ34S values between −2.2‰ and +4.6‰, consistent with a magmatic source. The vein-hosted sulfides associated with the high-Re molybdenite have a δ34S signature of 5.6‰ to 8.8‰, similar to values found in peridotite lenses in the Anatolian belt. The later enrichment in Re and δ34S-enriched S may be sourced from the surrounding ophiolitic country rock or may be the result of changing redox conditions during deposit formation.
Highlights
Porphyry Cu deposits provide 90% of the world’s rhenium production (Sinclair, 2007; Polyak, 2016)
The large range of Re concentration within molybdenite crystals is similar to that reported for other porphyry deposits globally, and the Re concentrations in the molybdenite samples show no correlation with any other trace elements within the deposit (Fig. 9)
Unlike Re and Se, which were present in all molybdenite samples analyzed (n = 71), the other trace elements analyzed were only above detection limit in some of the crystals
Summary
Porphyry Cu deposits provide 90% of the world’s rhenium production (Sinclair, 2007; Polyak, 2016). Rhenium is an essential element in a number of industrial applications, including superalloy production to make Ni-Re alloys for use in turbine blades for jet and industrial gas turbine engines and Pt-Re catalysts that improve the efficiency of crude oil refining (John, 2015). The relative restriction of supply of Re and the lack of viable alternative elements for its industrial uses has led to Re being classified as a “critical metal” by the United Kingdom and Russia (Chakhmouradian et al, 2015). The Muratdere Cu-Mo (Au-Re) porphyry deposit, located in the Tethyan metallogenic belt, Turkey, has a Joint Ore Reserves Committee (JORC)-compliant inferred resource of 51 million tonnes, including 186,000 tonnes Cu, 204,296 oz Au, 3.9 million oz Ag, 6,390 tonnes Mo, and 17,594 kg Re (Stratex International, 2017), with whole-rock Re concentrations of up to 2.37 ppm. Rhenium in porphyry deposits is typically hosted in molybdenite (MoS2) (Fleischer, 1959) with average concentrations of Re in molybdenite between 0.5 and >5,000
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