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Zinkgruvan, Knalla, Nygruvan, Ammeberg |
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Sweden |
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Zn Pb Ag
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Super Porphyry Cu and Au
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The two main Zinkgruvan (Ammeberg) deposits are located in the southern part of the Bergslagen District in south-western Sweden, WSW of Stockholm.
For detail of the setting and geology of the Bergslagen District see the separate Bergslagen District Base Metals record.
The orebodies are present in a thin (<20 m thick) sub-vertical, folded & faulted band which contains concordant to semi-concordant massive and semi-massive sulphide lenses and pods, as well as disseminated and vein sulphides developed over a strike length up to 5 km and >1300 m in vertical extent. In addition there are discordant stockwork and network stringers and veinlets. The mineralised system is hosted by Palaeoproterozoic (1900 Ma) metamorphics comprising granite gneisses, marble, chert, diopsidic and garnetiferous calc-silicates, quartz-feldspar-biotite gneiss and migmatites which are interpretted to comprise strongly metamorphosed and deformed felsic volcanics, volcaniclastics and chemical sediments.
The ore is hosted by the calc-silicates within an imediate host sequence interpretted to have been derived from volcanic siltstones, chemical sediments and a limestone-dolomite skarn. The deposits are interpretted to represent a metamorphosed volcanic hosted massive sulphide ore deposit and falls within the broader Garpenberg District with a number of smaller mines. All primary textures have been obliterated by the metamorphism.
The principal sulphide minerals are sphalerite, galena, chalcopyrite and pyrrhotite.
The operation serves two orebodies which together contained >43 Mt of ore in two mines, namely:
Nygruvan Mine with an average grade of 10% Zn, 1.5% Pb, 45 g/t Ag, and
Knalla Mine with 6% Zn, 5.5% Pb, 100 g/t Ag
The total production to 2000 amounted to approximately:
3.5 Mt of Zn metal (average ore grade of 8% Zn),
1.45 Mt of Pb (average ore grade of 4% Pb), and
3035 t of Ag (average ore grade of 70 g/t Ag)
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1994.
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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Selected References:
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Hallberg, A., Bergman, T., Gonzalez, J., Larsson, D., Morris, G. A., Perdahl, J. A., Ripa, M., Niiranen, T. and Eilu, P., 2012 - Metallogenic areas in Sweden: in Eilu, P., 2012 Mineral deposits and metallogeny of Fennoscandia, Geological Survey of Finland, Special Paper 53, pp. 139-206.
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Hedstrom P, Simeonov A, Malmstrom L 1989 - The Zinkgruvan ore deposit, south-central Sweden: a Proterozoic, proximal Zn-Pb-Ag deposit in distal volcanic facies: in Econ. Geol. v84 pp 1235-1261
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Kumpulainen R A, Mansfeld J, Sundblad K, Neymark L, Bergman T 1996 - Stratigraphy, age, and Sm-Nd isotope systematics of the country rocks to Zn-Pb Sulfide deposits, Ammeberg district, Sweden: in Econ. Geol. v91 pp 1009-1021
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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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