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1. Provenance of the Trainor's Rocks microconglomerate, Northern Ireland: a mid-Silurian (Hawick Group) submarine channel fan deposit in the closing Iapetus Ocean.

Author

Moles, Norman R., Cooper, Mark R., Hollis, Steven P., and McConnell, Brian

Subjects
*OUTCROPS (Geology), *METAMORPHIC rocks, *VOLCANIC ash, tuff, etc., *SUBMARINE fans, *ISLAND arcs
Abstract

A pebbly gritstone–microconglomerate outcrop at Trainor's Rocks in the Mourne Mountains is one of the youngest (c. 430 Ma) coarse clastic units within the Ordovician–Silurian Southern Uplands–Down–Longford Terrane. The c. 400 m by 1 km outcrop lies within fine-grained Hawick Group (Wenlock) strata, and is rich in extraformational clasts including granite, rhyolite, andesite, basalt, vein quartz and metamorphic rocks, plus intraformational rip-up clasts of mudstone. Detrital zircons, analysed by sensitive high-resolution ion microprobe (SHRIMP), yield predominantly Ordovician U–Pb ages of 450–490 Ma, peaking at c. 470 Ma, coincident with arc-related magmatism in the Midland Valley Terrane. Whole-rock geochemical data are consistent with derivation from a calc-alkaline continental arc, with clast provenance matching 473–464 Ma arc volcanic and intrusive rocks from the Tyrone Igneous Complex. A small proportion of analysed zircons have Proterozoic and Neoarchean ages typical of sediments derived from the Dalradian Supergroup (Grampian Terrane). The youngest zircon analysed, 435 ± 8 Ma, may indicate that magmatism continued during closure of Iapetus in the Llandovery. In these samples there is no evidence for Gondwana-derived sediment. The influx of detritus from the volcanic arc–Laurentian hinterland suggests episodic tectonic unroofing in response to syndepositional strike-slip movements. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Syn-Sedimentary Exhalative or Diagenetic Replacement? Multi-Proxy Evidence for Origin of Metamorphosed Stratiform Barite–Sulfide Deposits near Aberfeldy, Scottish Highlands.

Author

Moles, Norman R., Boyce, Adrian J., Warke, Matthew R., and Claire, Mark W.

Subjects
*SULFUR isotopes, *PRECIPITATION (Chemistry), *BARIUM carbonate, *BARITE, *BARIUM sulfate
Abstract

Bedded barite, Fe-Zn-Pb sulfides, carbonates, and cherts within Ediacaran (Dalradian Supergroup) graphitic metasediments near Aberfeldy in Scotland have previously been interpreted as chemical sediments precipitated from hydrothermal fluids episodically exhaled into marine basins filled with organic-rich mud, silt, and sand. Lithological variation and compositional diversity in pyrite and sphalerite reflect varied redox environments and proximity to hydrothermal discharges. Thick beds (>2 m) of barite have relatively uniform δ34S of +36 ± 1.5‰, considered to represent contemporaneous seawater sulfate, as negative Δ17O indicates incorporation of atmospheric oxygen during precipitation in the water column. However, certain features suggest that diagenetic processes involving microbial sulfate reduction modified the mineralogy and isotopic composition of the mineralization. Barite bed margins show decimeter-scale variation in δ34S (+32 to +41‰) and δ18O (+8 to +21‰), attributed to fluid-mediated transfer of dissolved barium and sulfate between originally porous barite and adjacent sediments, in which millimetric sulfate crystals grew across sedimentary lamination. Encapsulated micron-sized barium carbonates indicate early diagenetic barite dissolution with incorporation of sulfur into pyrite, elevating pyrite δ34S. Subsequently, sulfidation reactions produced volumetrically minor secondary barite with δ34S of +16 to +22‰. Overall, these processes affected small volumes of the mineralization, which originally formed on the seafloor as a classic SEDEX deposit. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Deciphering microbial communities involved in marine steel corrosion using high‐throughput amplicon sequencing.

Author

Shibulal, Biji, Smith, Martin Peter, Cooper, Ian, Burgess, Heidi Marie, Moles, Norman, and Willows, Alison

Subjects
MICROBIOLOGICALLY influenced corrosion, MICROBIAL enzymes, IRON corrosion, BACTERIAL communities, POLYMERASE chain reaction, SOIL corrosion, COASTAL sediments
Abstract

To characterize the source and effects of bacterial communities on corrosion of intertidal structures, three different UK coastal sites were sampled for corrosion materials, sediment and seawater. Chemical analyses indicate the activity of sulfate‐reducing microbes (SRBs) at 2 sites (Shoreham and Newhaven), but not at the third (Southend‐on‐Sea). Microbial communities in the deep sediment and corrosion samples are similar. The phylum Proteobacteria is dominant (40.4% of the total ASV), followed by Campilobacterota (11.3%), Desulfobacterota and Firmicutes (4%–5%). At lower taxonomic levels, corrosion causing bacteria, such as Shewanella sp. (6%), Colwellia sp. (7%) and Mariprofundus sp. (1%), are present. At Southend‐on‐sea, the relative abundance of Campilobacterota is higher compared to the other two sites. The mechanism of action of microorganisms at Shoreham and Newhaven involves biogenic sulfuric acid corrosion of iron by the combined action of SRBs and sulfur‐oxidizing microbes. However, at Southend‐on‐sea, sulfur compounds are not implicated in corrosion, but SRBs and other electroactive microbes may play a role in which cathodic reactions (electrical MIC) and microbial enzymes (chemical MIC) are involved. To contribute to diagnosis of accelerated intertidal corrosion types, we developed a rapid identification method for SRBs using quantitative polymerase chain reaction high‐resolution melt curve analysis of the dsrB gene. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Formation of the giant Aynak copper deposit, Afghanistan: evidence from mineralogy, lithogeochemistry and sulphur isotopes

Author

Waizy, Hamidullah, Moles, Norman R., Smith, Martin P., and Boyce, Adrian J.

Abstract

Aynak is the largest known copper deposit in Afghanistan, with indicated resources of 240 Mt grading 2.3% Cu placing it in the ‘giant’ category. Host rocks are Neoproterozoic metasediments comprising dolomitic marble, carbonaceous quartz schist and quartz-biotite-dolomite schist containing garnet, scapolite and apatite. Chalcopyrite and bornite dominate the hypogene ore with lesser pyrite, pyrrhotite, cobaltite and chalcocite, and rare sphalerite, molybdenite, uraninite and barite. Sulphides occur as bedding-parallel laminae, disseminations, metamorphic segregations and crosscutting veins. Sulphide δ34S ratios range –14.5 to +17.3‰ in bedded and disseminated sulphides (n = 34). This broad range favours biogenic reduction of seawater sulphate as a major source of sulphur, although thermochemical reduction processes are not precluded. The narrower δ34S range of –6 to +12.2‰ in vein and segregation sulphides (n = 21) suggests localized redistribution and partial homogenization during metamorphism. Geochemical associations suggest that Al, P, Ca, Ti and Fe were primary sedimentary constituents whereas Cu, Mg, S, Se, As, Co and Bi were introduced subsequently. We infer that Aynak originated as a shale- and carbonate-hosted stratabound replacement deposit, resembling orebodies of the Central African Copperbelt, although underlying red-beds are absent at Aynak and mafic volcanics were the probable copper source. These giant deposits formed worldwide in the Cryogenian probably due to marine enrichment in copper, magnesium and sulphate coincident with profuse basaltic volcanism and ocean oxidation.

Published
2021

18. Abstracts from the 2017–2018 Mineral Deposits Studies Group meeting

Author

Santoro, L., primary, Yav, St. Tshipeng, additional, Pirard, E., additional, Kaniki, A., additional, Arfè, G., additional, Mondillo, N., additional, Boni, M., additional, Joachimski, M., additional, Balassone, G., additional, Mormone, A., additional, Cauceglia, A., additional, Robb, W., additional, Smith, T. L., additional, Currie, David, additional, Stuart, Finlay, additional, Faithfull, John, additional, Boyce, Adrian, additional, Chelle-Michou, C., additional, Cretella, S., additional, Scognamiglio, G., additional, Tarallo, M., additional, Putzolu, F., additional, Pirajno, F., additional, Aitbaeva, Saltanat, additional, Mizernaya, Marina, additional, Dyachkov, Boris, additional, Martin, Andrew J, additional, McDonald, Iain, additional, MacLeod, Christopher J, additional, McFall, Katie, additional, Prichard, Hazel M, additional, Jenkin, Gawen R T, additional, Kennedy, B., additional, McDonald, I., additional, Tanner, D., additional, Longridge, L., additional, Borst, A. M., additional, Finch, A. A., additional, Friis, H., additional, Horsburgh, N. J., additional, Gamaletsos, P. N., additional, Goettlicher, J., additional, Steininger, R., additional, Geraki, K., additional, Cloutier, Jonathan, additional, Piercey, Stephen J., additional, Allen, Connor, additional, Storey, Craig, additional, Darling, James, additional, Lasalle, Stephanie, additional, Dobrzanski, A., additional, Kirstein, L., additional, Walcott, R., additional, Butler, I., additional, Ngwenya, B., additional, Dobrzanski, Andrew, additional, Howard, Simon, additional, Troalen, Lore, additional, Davidson, Peter, additional, Walcott, Rachel, additional, Drummond, Drew, additional, Blakeman, Robert, additional, Ashton, John, additional, Marquis, Eva, additional, Goodenough, Kathryn, additional, Estrade, Guillaume, additional, Smith, Martin, additional, Zygouri, E., additional, Kilias, S. P., additional, Zack, T., additional, Pitcairn, I., additional, Chi Fru, E., additional, Nomikou, P., additional, Argyraki, A., additional, Ivarsson, M., additional, Finch, Adrian A., additional, Borst, Anouk M., additional, Hutchison, William, additional, Horsburgh, Nicola J., additional, Andersen, Tom, additional, Simonsen, Siri, additional, Waizy, Hamidullah, additional, Moles, Norman, additional, Hollis, Steven P., additional, Menuge, Julian F., additional, Doran, Aileen L., additional, Dennis, Paul, additional, Davidheiser-Kroll, Brett, additional, Marca, Alina, additional, Wilkinson, Jamie, additional, Güven, John, additional, Cooper, Mark R., additional, Stephen Daly, J., additional, Turner, Oakley, additional, McConnell, Brian, additional, Hughes, Hannah S. R., additional, Matusiak-Małek, Magdalena M., additional, Williamson, Ben, additional, Williams, James, additional, Dishaw, Guy, additional, Rees, Harri, additional, Key, Roger, additional, Bate, Simon, additional, Moore, Andy, additional, Tanner, Dominque, additional, Keith, Manuel, additional, Haase, Karsten M., additional, Smith, Daniel J., additional, Klemd, Reiner, additional, Schwarz-Schampera, Ulrich, additional, Bach, Wolfgang, additional, Walding, Sam J, additional, Jenkin, Gawen RT, additional, James, Daniel, additional, Clark, David, additional, Hart-Madigan, Lisa, additional, Armstrong, Robin, additional, Graham, Hugh, additional, Smith, Daniel J, additional, Abbott, Andrew P, additional, Holwell, David A, additional, Zygouri, Eva, additional, Harris, Robert C, additional, Stanley, Christopher J, additional, Grant, Hannah L.J., additional, Hannington, Mark D., additional, Petersen, Sven, additional, Frische, Matthias, additional, Zhang, Fei, additional, Williamson, Ben J., additional, Hughes, Hannah, additional, Smiles, Joshua, additional, Nathwani, Chetan, additional, Sievwright, Robert, additional, Loader, Matthew, additional, Blanks, Daryl E., additional, Holwell, David A., additional, Smith, W.D., additional, Darling, J.R., additional, Bullen, D.S., additional, Scrivener, R.C., additional, Boyce, Adrian J., additional, Broom-Fendley, Sam, additional, Brady, Aoife E, additional, Hudson-Edwards, Karen, additional, Hollis, Steve, additional, McClenaghan, Sean, additional, Doran, Aileen, additional, Fallon, Emily K., additional, Brooker, Richard, additional, and Scott, Thomas, additional

Published
2018
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20. A natural laboratory for critical metals investigations in the Mourne Mountains granites

Author

Young, M.E., Moore, Kathryn, Moles, Norman, Lusty, Paul, Young, M.E., Moore, Kathryn, Moles, Norman, and Lusty, Paul

Abstract

Certain metals that are vital for many modern technologies occur naturally in the Mourne Mountains Complex of County Down, Northern Ireland. These include niobium, tantalum and the rare earth elements. Using the Tellus geochemistry data and the results of more detailed sampling, we have investigated their geological sources in granite bedrock and their dispersion in stream sediments. From this research, an exploration methodology has emerged that can assist in the search for critical metals globally. Planned follow-on studies include investigations of the environmental fate of these metals and the potentially toxic elements with which they are naturally associated.

Published
2016

26. Abundant sulphate in the Neoproterozoic ocean: implications of constant δ34S of barite in the Aberfeldy SEDEX deposits, Scottish Dalradian

Author

Moles, Norman R., Boyce, Adrian J., and Fallick, Anthony E.

Abstract

The timing and extent of ocean oxygenation is controversial. Proterozoic sulphur isotope datasets often show marked fluctuations over small stratigraphic intervals, suggesting that oceanic sulphate concentrations were much lower than modern values. A large accumulation of Neoproterozoic sulphate (>8 million tonnes preserved), as stratiform barite rock, is located in the Grampian Highlands near Aberfeldy. Diagenetic/metamorphic alteration has caused pronounced δ34S variations near bed margins. This aside, barite throughout the deposits shows a narrow range in δ34S, mean 36±1.5‰. We infer that this is representative of contemporaneous seawater sulphate, and that δ34Sseawaterwas constant during deposition of a stratigraphical thickness >250 m of mostly fine-grained clastic sediments. Uniformity of δ34Sseawaterduring barite precipitation, even in thick (>10 m) beds and with the co-occurrence of abundant sulphides incorporating bacteriogenically reduced sulphur, implies no limit to availability of seawater sulphate during hydrothermal exhalative events. Our data, combined with previous δ34S research on Dalradian metasediments, suggest a stability, abundance and constancy of ocean sulphate in the Neoproterozoic. This contrasts with isotopic data using trace sulphate in limestones. It appears that, around the time of the Marinoan glaciation (c.635 Ma), the ocean, although stratified at least locally, comprised a substantial reservoir of sulphate-bearing oxygenated seawater.

Published
2015
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27. Sphalerite composition in relation to deposition and metamorphism of the Foss stratiform Ba-Zn-Pb deposit, Aberfeldy, Scotland

Author

Moles, Norman R.

Abstract

AbstractSphalerite is a common constituent of the mineralized rocks and host metasediments of the Foss baryte-base metal deposit, located near Aberfeldy in the central Scottish Highlands. Microprobe analyses of sphalerite show a wide range in minor element content (0–17 mol. % FeS, 0–3 mol. % MnS), and sphalerites of contrasting composition are often found in the same rock. This suggests that equilibrium domains in some rocks were minute (< 1 mm), during regional metamorphism. Pressures derived from the selective application of the sphalerite geobarometer are consistent with other mineralogical evidence of peak metamorphic pressures in the range 7–10 kbar, at 540–580 °C. However, there is considerable evidence of partial retrograde re-equilibration of sphalerite, by continued buffering with pyrite+ pyrrhotine and by outward diffusion of iron. Marginal depletion of Fe and Mn in sphalerite within coarse carbonate rocks is attributed to partitioning reactions following recrystallization. Sphalerite which has retained its pre-metamorphic composition shows systematic variations in composition through profiles of mineralized beds, which may be related to depositional environments. Bimodal primary compositions can be explained by precipitation of zinc sulphides under the contrasting chemical environments of hydrothermal vents and cooler, exhaled brine layers on the sea floor.

Published
1983
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29. Rare Earth Element (REE) mobility in alkaline igneous rocks and the potential impact on the formation of ion adsorption type REE ores of the Ambohimirahavavy alkaline complex

Author

Marquis, Eva, Moles, Norman, Smith, Martin, and Goodenough, Kathryn

Subjects
553.4
Abstract

Ion Adsorption Deposits (IAD) are a major source of Heavy Rare Earth Elements (Gd – Lu; HREE) to global markets. Most currently known IAD are hosted in thick regolith profiles, developed in temperate to tropical climates from metaluminous to peraluminous granites that have experienced varying degrees of metasomatic alteration. However, typically these granites are not strongly Rare Earth Element (REE)-enriched. In contrast, alkaline to peralkaline syenitic to granitic complexes are known to contain elevated concentrations of REE – leading to the hypothesis that if IAD can form on relatively REE poor protoliths, then regolith profiles developed upon REE-enriched alkaline to peralkaline rocks should contain IAD more strongly enriched in REE. The alkaline to peralkaline Ambohimirahavavy Complex is covered by regolith profiles developed in a tropical climate. The petrogenesis and controls on REE mineralisation of the Ambohimirahavavy Complex’s south-eastern Ampasibitika intrusion have been investigated here. The Ampasibitika Intrusion is a heterogeneous sub-volcanic intrusion, where silica-undersaturated to –oversaturated intrusive rocks are exposed alongside volcanic units. Petrographic features, mineral chemistry and whole rock major and trace element geochemistry indicate the Ampasibitika Intrusion evolved via fractional crystallisation and differentiation of a weakly peralkaline melt, sourced from low degree partial melting of a metasomatised mantle source, in a shallow crustal magma chamber to emplacement of heterogeneous crustal mushes and melts to higher crustal levels during caldera forming events. The coalescence of highly evolved residual/immiscible melts in the magma chamber roof zone and assimilation of crustal material and/or previously crystallised syenites formed silica-oversaturated trachytic to peralkaline granitic melts, which were emplaced as a concentric dyke swarm. Varying degrees of fractional crystallisation and melt differentiation, and possible salt-silicate melt immiscibility, resulted in variable REE-enrichment. REE concentrations generally increase with progressive melt evolution and volatile-enrichment. The emplacement of crystal mushes and melts to higher crustal levels was associated with melt/fluid immiscibility/exsolution, causing late magmatic to hydrothermal alteration. Mineral stable isotope signatures indicate most alteration fluids were of magmatic origin. Potential source minerals of REE for the Ampasibitika IAD include REE-fluorcarbonate, britholite, allanite, titanite, which are generally late magmatic to hydrothermal mineral phases, and early magmatic calcic-amphibole and -clinopyroxene. However, late magmatic to hydrothermal alteration may also produce REE-poor phases (e.g. sodic-amphibole/clinopyroxene) or REE-enriched minerals resistant to dissolution during weathering (e.g. zircon). Thus, the alteration style controls the development of REE source minerals of varying benefit to IAD formation. Within the Ampasibitika IAD, REE are principally adsorbed to kaolinite and/or halloysite; thus, the formation conditions of kaolinite derived from a range of regolith profiles and depths were investigated using stable isotope methods. The results suggest that, although some kaolinite present is of hypogene origin, these potential REE-host minerals are principally of supergene origin, and therefore the products of intense chemical weathering. Overall, REE mobility during late magmatic to hydrothermal alteration has variably influenced the availability of REE for subsequent IAD. Thus, although magmatic processes may produce extreme REE-enrichment in alkaline to peralkaline intrusions, it is generally the late magmatic to hydrothermal evolution that affects the development of IAD REE-source minerals of the Ampasibitika Intrusion.

Published
2019

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