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Black Angel |
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Greenland |
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Zn Pb Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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Black Angel is a stratabound massive sulphide Fe-Pb-Zn deposit on the central west coast of Greenland, hosted by evaporitic marbles in the upper section of the Palaeoproterozoic Marmorilik Formation in the Karrat Basin. The ore and hosts have been strongly deformed in three phases and metamorphised at temperatures of 450 to 500°C under low confining pressures. Deformation includes isoclinal folding and thrusting.
The Middle Paleoproterozoic Karrat Group of the Karrat Basin is an ~8.5 km thick metasedimentary sequence, deposited after ~2.0 Ga (Kalsbeek et al., 1998), unconformably overlying the Archaean Umanak Gneiss Complex in northern West Greenland (Henderson and Pulvertaft 1967, 1987). According to Henderson and Pulvertaft (1987), the Karrat Group includes the lower (mainly siliciclastic) Qeqertarssuaq Formation, the carbonate-dominated Mârmorilik Formation, and the upper turbiditic Nûkavsak Formation that locally contains pyrrhotite-chert-graphite bearing beds. Intercalated within the lower part of the Nûkavsak Formation, there are mafic metavolcanic rocks (Rosa et al., 2023).
The Marmorilik Formation is believed to be around 2000 m thick and was deposited within a shallow-water, stromatolite-bearing marine carbonate platform (Pedersen1978). It was deposited on an eroded surface and commences with irregularly interbedded quartzite, meta-arkose, semi-pelite, calcareous schist and small pockets of conglomerate. These basal clastics are overlain by a succession of marble making up the majority of the unit, the lower 500 to 600 m of which are massive banded dolomites with intercalated calcite marble, graphite bearing calcite-dolomite and chert. These are followed by 500 m of light coloured massive calcite marble. The orebodies are localised where the dolomite marble, graphite and anhydrite/gypsum become important components of the calcite-marbles. This sequence is then capped by 400 m of meta-argillite, meta-siltstone, meta-psammite and chert with minor graphite-pyrrhotite schist.
The orebody is a ductile deformed tabular body of 42% pyrite, 22% sphalerite and 7% galena with minor chalcopyrite, stannite, tennantite, arsenopyrite, loellingite, enargite, bornite, polybasite, electrum, rutile, hematite, magnetite and graphite. The orebody varies from 0.5 to 35 m in thickness with a length of 3 km and width of up to 600 m. It has been divided into: i). massive and banded ore, ii). porphyroclastic ore and iii). remobilised sulphides.
The deposit encompasses eight different ore bodies and two satellite ore bodies (the Nunngarut orebodies) located ~4 km to the SW. Further outcropping
mineralised occurrences are found in similar settings, 4 to 10 km to the SE and ~85 km to the SW of Black Angel.
One estimate of the resource has been quoted as 10 Mt @ 13.5% Zn, 4.5% Pb, 31 g/t Ag,
although the reserve has also been given as 7 Mt @ 15% Zn, 5.5% Pb, 30 g/t Ag. Rosa et al. (2023) quote pre-mining reserves after Thomassen (1991) of 13 Mt @ 12% Zn, 4% Pb, 29 ppm Ag.
The deposit was actively underground mined between 1973 and 1990 (Rosa et al., 2023).
The most recent source geological information used to prepare this decription was dated: 2023.
Record last updated: 11/1/2023
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Horn, S., Dziggel, A., Kolb, J. and Sindern, S., 2019 - Textural characteristics and trace element distribution in carbonate-hosted Zn-Pb-Ag ores at the Paleoproterozoic Black Angel deposit, central West Greenland: in Mineralium Deposita v.54, pp. 507-524.
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Pedersen F D 1980 - Remobilization of the massive sulfide ore of the Black Angel mine, central west Greenland: in Econ. Geol. v75 pp 1022-1041
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Rosa, D., Leach, D., Guarnieri, P. and Bekker, A., 2023 - The Black Angel deposit, Greenland: a Paleoproterozoic evaporite‑related Mississippi Valley‑type Zn-Pb deposit: in Mineralium Deposita v.58, pp. 51-73. doi.org/10.1007/s00126-022-01125-z.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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