Cu–(Ni–Co–Au)-bearing massive sulfide deposits associated with mafic–ultramafic rocks of the Main Urals Fault, South Urals: Geological structures, ore textural and mineralogical features, comparison with modern analogs

The pyrite nodules from ore diagenites of the Urals massive sulfide deposits associated with various background sedimentary rocks are studied using optical and electron microscopy and LA-ICP-MS analysis. The nodules are found in sulfide–black shale, sulfide–carbonate–hyaloclastite, and sulfide–serpentinite diagenites of the Saf’yanovskoe, Talgan, and Dergamysh deposits, respectively. The nodules consist of the core made up of early diagenetic fine-crystalline (grained) pyrite and the rim (±intermediate zone) composed of late diagenetic coarse-crystalline pyrite. The nodules are replaced by authigenic sphalerite, chalcopyrite, galena, and fahlores (Saf’yanovskoe), sphalerite, chalcopyrite and galena (Talgan), and pyrrhotite and chalcopyrite (Dergamysh). They exhibit specific accessory mineral assemblages with dominant galena and fahlores, various tellurides and Co–Ni sulfoarsenides in sulfide-black shale, sulfide–hyaloclastite–carbonate, and sulfide-serpentinite diagenites, respectively. The core of nodules is enriched in trace elements in contrast to the rim. The nodules from sulfide–black shale diagenites are enriched in most trace elements due to their effective sorption by associated organic-rich sediments. The nodules from sulfide–carbonate–hyaloclastite diagenites are rich in elements sourced from seawater, hyaloclastites and copper–zinc ore clasts. The nodules from sulfide–serpentinite diagenites are rich in Co and Ni, which are typical trace elements of ultramafic rocks and primary ores from the deposit.

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“…The thin ore layers are intercalated with black shales at the flanks of the deposit and form bedded bodies up to 20 cm thick. [27,28,37]).…”

Section: Saf'yanovskoe Depositmentioning

confidence: 99%

Authigenesis at the Urals Massive Sulfide Deposits: Insight from Pyrite Nodules Hosted in Ore Diagenites

et al. 2020

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“…It should be noted that anomalously high metal concentrations in hydrothermal fluids can form ore deposits for other metals including Zn and Pb (Wilkinson et al, ). Various hydrothermal sulfide deposits have shown high Co concentrations, such as in the 13°N hydrothermal field on the East Pacific Rise (Fouquet et al, ), West Magnitogorsk paleoisland arc of the South Urals (Artemyev & Zaykov, ), the southern portion of the Main Urals Fault (Melekestseva et al, ), and the MAR Ashadze‐1 Field (Firstova et al, ), which could leave open the possibility of high concentrations of Co in hydrothermal fluids. These potentially high Co concentrations in hydrothermal fluids, owing to alteration of ultramafic rocks by seawater at high temperature and pressure, and limited Co‐mineral formation before 2500 Ma (Figure ), could have resulted in enhanced organic complexation in the Archean ocean.…”

Section: Factors Influencing Biological Co Utilizationmentioning

confidence: 99%

“…Rise (Fouquet et al, 1996), West Magnitogorsk paleoisland arc of the South Urals (Artemyev & Zaykov, 2010), the southern portion of the Main Urals Fault (Melekestseva et al, 2013), and the MAR Ashadze-1 Field (Firstova et al, 2016), which could leave open the possibility of high concentrations of Co in hydrothermal fluids. These potentially high Co concentrations in hydrothermal fluids, owing to alteration of ultramafic rocks by seawater at high temperature and pressure, and limited Co-mineral formation before 2500 Ma (Figure 1), could have resulted in enhanced organic complexation in the Archean ocean.…”

Section: 1002/2017jg004067mentioning

confidence: 99%

Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon

et al. 2018

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The geosphere and biosphere coevolved and influenced Earth's biological and mineralogical diversity. Changing redox conditions influenced the availability of different transition metals, which are essential components in the active sites of oxidoreductases, proteins that catalyze electron transfer reactions across the tree of life. Despite its relatively low abundance in the environment, cobalt (Co) is a unique metal in biology due to its importance to a wide range of organisms as the metal center of vitamin B12 (aka cobalamin, Cbl). Cbl is vital to multiple methyltransferase enzymes involved in energetically favorable metabolic pathways. It is unclear how Co availability is linked to mineral evolution and weathering processes. Here we examine important biological functions of Co, as well as chemical and geological factors that may have influenced the utilization of Co early in the evolution of life. Only 66 natural minerals are known to contain Co as an essential element. However, Co is incorporated as a minor element in abundant rock‐forming minerals, potentially representing a reliable source of Co as a trace element in marine systems due to weathering processes. We developed a mineral weathering model that indicates that dissolved Co was potentially more bioavailable in the Archean ocean under low S conditions than it is today. Mineral weathering, redox chemistry, Co complexation with nitrogen‐containing organics, and hydrothermal environments were crucial in the incorporation of Co in primitive metabolic pathways. These chemical and geological characteristics of Co can inform the biological utilization of other trace metals in early forms of life.

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“…The concentrations of trace elements in the ores from the SMSs, especially those that are mobilized at relatively low temperatures, are remarkably sensitive to the source rock concentrations in different tectonic settings (e.g., [3,7,57]). For example, mafic-and ultramafic-hosted SMSs at mid-ocean ridges are often enriched in Ni and Co [3,4,58], whereas felsic-hosted deposits in volcanic arc settings are enriched in Pb, As, Ag, Sb, and Sn [7]. Previous studies concluded that the presence of elevated Ni and Co concentrations in the sulfide minerals from ultramafic SMS deposits originates from the ultramafic substrate (1960 ppm Ni and 106 ppm Co in depleted mantle versus 104 ppm Ni and 44 ppm Co in MORB [59,60]).…”

Section: Comparison With Mafic-and Ultramafic-hosted Sms Depositsmentioning

confidence: 99%

“…Previous studies concluded that the presence of elevated Ni and Co concentrations in the sulfide minerals from ultramafic SMS deposits originates from the ultramafic substrate (1960 ppm Ni and 106 ppm Co in depleted mantle versus 104 ppm Ni and 44 ppm Co in MORB [59,60]). However, depositional conditions may also play significant roles in determining the final metal concentrations in the sulfide minerals [58].…”

Section: Comparison With Mafic-and Ultramafic-hosted Sms Depositsmentioning

confidence: 99%

Trace Metal Distribution in Sulfide Minerals from Ultramafic-Hosted Hydrothermal Systems: Examples from the Kairei Vent Field, Central Indian Ridge

et al. 2018

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The ultramafic-hosted Kairei vent field is located at 25°19′ S, 70°02′ E, towards the Northern end of segment 1 of the Central Indian Ridge (CIR-S1) at a water depth of ~2450 m. This study aims to investigate the distribution of trace elements among sulfide minerals of differing textures and to examine the possible factors controlling the trace element distribution in those minerals using LA-ICP-MS spot and line scan analyses. Our results show that there are distinct systematic differences in trace element distributions throughout the different minerals, as follows: (1) pyrite is divided into three types at Kairei, including early-stage euhedral pyrite (py-I), sub-euhedral pyrite (py-II), and colloform pyrite (py-III). Pyrite is generally enriched with Mo, Au, As, Tl, Mn, and U. Pyrite-I has high contents of Se, Te, Bi, and Ni when compared to the other types; py-II is enriched in Au relative to py-I and py-III, but poor in Ni; py-III is enriched in Mo, Pb, and U but is poor in Se, Te, Bi, and Au relative to py-I and py-II. Variations in the concentrations of Se, Te, and Bi in pyrite are most likely governed by the strong temperature gradient. There is generally a lower concentration of nickel than Co in pyrite, indicating that our samples precipitated at high temperatures, whereas the extreme Co enrichment is likely from a magmatic heat source combined with an influence of serpentinization reactions. (2) Chalcopyrite is characterized by high concentrations of Co, Se, and Te. The abundance of Se and Te in chalcopyrite over the other minerals is interpreted to have been caused by the high solubilities of Se and Te in the chalcopyrite lattice at high temperatures. The concentrations of Sb, As, and Au are relatively low in chalcopyrite from the Kairei vent field. (3) Sphalerite from Zn-rich chimneys is characterized by high concentrations of Sn, Co, Ga, Ge, Ag, Pb, Sb, As, and Cd, but is depleted in Se, Te, Bi, Mo, Au, Ni, Tl, Mn, Ba, V, and U in comparison with the other minerals. The high concentrations of Cd and Co are likely caused by the substitution of Cd2+ and Co2+ for Zn2+ in sphalerite. A high concentration of Pb accompanied by a high Ag concentration in sphalerite indicates that Ag occurs as Pb–Ag sulfosalts. Gold is generally low in sphalerite and strongly correlates with Pb, suggesting its presence in microinclusions of galena. The strong correlation of As with Ge in sphalerite from Kairei suggests that they might precipitate at medium temperatures and under moderately reduced conditions. (4) Bornite–digenite has very low concentrations of most trace elements, except for Co, Se, and Bi. Serpentinization in ultramafic-hosted hydrothermal systems might play an important role in Au enrichment in pyrite with low As contents. Compared to felsic-hosted seafloor massive sulfide deposits, sulfide minerals from ultramafic-hosted deposits show higher concentrations of Se and Te, but lower As, Sb, and Au concentrations, the latter often attributed to the contribution of magmatic volatiles. As with typical ultramafic-hosted seafloor massive sulfide deposits, Se enrichment in chalcopyrite from Kairei indicates that the primary factor that controls the Se enrichment is temperature-controlled mobility in vent fluids.

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Cu–(Ni–Co–Au)-bearing massive sulfide deposits associated with mafic–ultramafic rocks of the Main Urals Fault, South Urals: Geological structures, ore textural and mineralogical features, comparison with modern analogs

Cited by 50 publications

References 45 publications

Authigenesis at the Urals Massive Sulfide Deposits: Insight from Pyrite Nodules Hosted in Ore Diagenites

Authigenesis at the Urals Massive Sulfide Deposits: Insight from Pyrite Nodules Hosted in Ore Diagenites

Geological and Chemical Factors that Impacted the Biological Utilization of Cobalt in the Archean Eon

Trace Metal Distribution in Sulfide Minerals from Ultramafic-Hosted Hydrothermal Systems: Examples from the Kairei Vent Field, Central Indian Ridge

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