Precious metals assemblages at the Mikheevskoe porphyry copper deposit (South Urals, Russia) as proxies of epithermal overprinting

Plotinskaya, O. Yu.; Azovskova, O. B.; Abramov, S. K.; Groznova, E. O.; Новоселов, К. А.; Seltmann, Reimar; Spratt, John

doi:10.1016/j.oregeorev.2018.01.025

Cited by 24 publications

(9 citation statements)

References 34 publications

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“…Sample Z-1461/164.5 comes from the Zapadnoe deposit located immediately to the west from the Mikheevskoe porphyry copper deposit, Chelyabinsk Oblast, Russia. The latter was described by Plotinskaya and co-workers (Plotinskaya et al ., 2015, 2018 b ). The sample represents seriate diorite porphyry with phyllic alteration and a network of quartz veinlets ~0.5 cm thick with molybdenite nests up to 2 mm and later chlorite stringers.…”

Section: Sample Selection and Analytical Methodsmentioning

confidence: 99%

Grain-scale distribution of molybdenite polytypes versus rhenium contents: μXRD and EBSD data

Plotinskaya

Shilovskikh

Najorka

et al. 2019

MinMag

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Molybdenite from two porphyry copper mineralisation sites within the South Urals was studied by electron microprobe (EMPA), micro x-ray diffraction (μXRD) and electron backscattered diffraction (EBSD) methods. Elevated contents of rhenium (0.2 to 0.4, sometimes up to 1.1 wt.%) form linear zones from several to tens of micrometres wide and up to hundreds of micrometres long parallel to the elongation of molybdenite flakes. In most cases Re-rich zones are composed of the rhombohedral (3R) polytype of molybdenite, while the rest of the molybdenite flakes with ca. 0.1 wt.% of Re consist of hexagonal (2H) molybdenite. In rare cases Re-rich zones are confined to grain boundaries of molybdenite-2H. It is shown that both μXRD and EBSD are the most appropriate tools to distinguish different polytypes within a single grain of molybdenite.

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Section: Sample Selection and Analytical Methodsmentioning

confidence: 99%

Grain-scale distribution of molybdenite polytypes versus rhenium contents: μXRD and EBSD data

Plotinskaya

Shilovskikh

Najorka

et al. 2019

MinMag

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“…Although common in epithermal environments, precious metal-bearing selenides and tellurides are rare in porphyry environments, leading Plotinskaya et al (2018) to suggest that these minerals formed through interaction of the sulphides through a late epithermal fluid. The concentration of the microparticles at the edges of or along fractures within the sulphides would be consistent with this interpretation.…”

Section: Direct Precipitation From a Fluidmentioning

confidence: 99%

Precious and Critical Metal-Bearing Assemblages in the Ann Mason Copper Porphyry Deposit, Yerington, Nevada

Aird¹,

Purcell²,

Witt³

et al. 2021

Preprint

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Porphyry deposits are an important source of copper and their value may be upgraded by minor contents of precious metals, if they are extractable. The mechanisms for enrichment of precious and base metals in these systems are not well understood. This study investigates the deportment of trace metals in the Ann Mason porphyry deposit, including gold, silver, palladium, mercury, lead and bismuth. Petrographic and geochemical data are integrated to characterize the size and habit of minerals, the host mineral assemblages, and their association with alteration assemblages. Ann Mason is one of several ore deposits hosted by the Yerington batholith in Nevada, and is being assessed for copper extraction from bornite and chalcopyrite ore assemblages, associated with potassic alteration. Mineralization assemblages at Ann Mason have been categorized as chalcopyrite-bornite, chalcopyrite-pyrite and pyrite>chalcopyrite zones. Limited two-metre assay data indicates that gold is most closely associated with bornite, although it is found in all three mineralization zones. Analysis by SEM-EDS shows that trace elements are mostly present as microparticles hosted by sulfide minerals. Of the 438 grains measured, 89% are hosted by a sulfide mineral, with 68% hosted by bornite. Silver is most commonly present as hessite and gold as electrum, hosted by bornite and associated with potassic alteration. Palladium, mercury and bismuth are most commonly observed as telluride and selenide minerals. Palladium minerals are associated with potassic alteration, while mercury and bismuth minerals are mostly found with sericitic alteration. High fineness native gold is observed as three round blebs hosted by pyrite or silicates. Observations suggest that the trace metals in the chalcopyrite-bornite zone may have been incorporated by bornite and chalcopyrite, and exsolved upon cooling. In the chalcopyrite-pyrite and pyrite>chalcopyrite zones, the trace metals may have been deposited directly from a mineralizing hydrothermal fluid and incorporated into the growing sulphide minerals. These findings have implications for the paragenesis of porphyry deposits, as well as for the milling processes that would be needed to extract precious metals at the Ann Mason porphyry deposit.

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“…Although these deposits also contain a range of silver tellurides, neither of them are reported to contain sopcheite, suggesting the Ag and PGE in those deposits are either transported by different mechanisms or are temporally or spatially separate. There are a wider variety of PGM reported in the porphyry -epithermal transition Ore Geology Reviews 99 (2018) 344-364 zone of deposits such as Mount Milligan, with naldrettite and stibiopalladinite present (Lefort et al, 2011), and the Mikheevskoe deposit (South Urals), with merenskyite and rare sopcheite reported (Plotinskaya et al, 2018). Skouries however has the largest variety of PGM reported within the higher temperature potassic alteration zone of a porphyry deposit.…”

Section: Pgm In the Skouries Depositmentioning

confidence: 99%

“…However, there are documented examples of veins bearing PGM in the porphyry-epithermal transition zone. For example, the late stage 'sub-epithermal' veins in the Mount Milligan porphyry deposit, British Columbia contain PGM associated with electrum and Hg-rich pyrite (Lefort et al, 2011), and PGM have also been documented in the epithermal overprint of the Mikheevskoe porphyry deposit (Plotinskaya et al, 2018).…”

Section: Pgm In the Skouries Depositmentioning

confidence: 99%

“…Additionally stibiopalladinite [Pd 5 Sb 2 ] and vysotskite [(Pd,Ni)S] have been identified in sulphide concentrates from Santo Tomas II (Piestrzynski, 1994), while merenskyite has been identified in sulphide concentrates from Aksug, Majdanpek and Mamut (where sperrylite [PtAs 2 ] was also identified; Tarkian and Stribrny, 1999). A greater variety of PGM have been identified in transitional porphyry-epithermal veins and a range of telluride minerals, including PGM, are often present in alkalic epithermal Au deposits (Lefort et al, 2011;Plotinskaya et al, 2018;Watterson et al, 1977).…”

Section: Introductionmentioning

confidence: 99%

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Platinum-group minerals in the Skouries Cu-Au (Pd, Pt, Te) porphyry deposit

McFall

Naden

Roberts

et al. 2018

Ore Geology Reviews

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A B S T R A C TThe Skouries deposit is a platinum-group element (PGE) enriched Cu-Au porphyry system located in the Chalkidiki peninsula, Greece, with associated Ag, Bi and Te enrichment. The deposit is hosted by multiple porphyritic monzonite and syenite intrusions, which originated from a magma chamber at depth. An initial quartz monzonite porphyritic intrusion contains a quartz-magnetite ± chalcopyrite-pyrite vein stockwork with intense potassic alteration. The quartz monzonite intrusion is cross cut by a set of syenite and mafic porphyry dykes and quartz-chalcopyrite-bornite ± magnetite veins which host the majority of the Cu and Au mineralisation. Late stage quartz-pyrite veins, with associated phyllic alteration crosscut all previous vein generations. Electron microprobe and scanning electron microscopy shows that the PGE are hosted by platinum-group minerals (PGM) in the quartz-chalcopyrite-bornite ± magnetite veins and within potassic alteration assemblages. The PGE mineralisation in Skouries is therefore part of the main high temperature hypogene mineralisation event. [PdBi]. The most common platinum-group mineral is sopcheite. The PGM in Skouries are small, 52 µm 2 on average, and occur as spherical grains on the boundaries between sulphides and silicates, and as inclusions within hydrothermal quartz and sulphides. These observations support a "semi-metal collector model" whereby an immiscible Bi-Te melt acts as a collector for PGE and other precious metals in high temperature hydrothermal fluids. This mechanism would allow the formation of PGM in porphyries without Pt and Pd fluid saturation.

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Precious metals assemblages at the Mikheevskoe porphyry copper deposit (South Urals, Russia) as proxies of epithermal overprinting

Cited by 24 publications

References 34 publications

Grain-scale distribution of molybdenite polytypes versus rhenium contents: μXRD and EBSD data

Grain-scale distribution of molybdenite polytypes versus rhenium contents: μXRD and EBSD data

Precious and Critical Metal-Bearing Assemblages in the Ann Mason Copper Porphyry Deposit, Yerington, Nevada

Platinum-group minerals in the Skouries Cu-Au (Pd, Pt, Te) porphyry deposit

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