Database name: |
World Fe-oxide+/-Cu-Au-U (IOCG) deposits |
Compilers: |
Sunil S. Gandhi |
Release date: |
2015-03-04 |
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Deposit name(s): |
Exportfältet; Grängesberg |
Political location(s): |
Sweden; Province or state: Dalarna; Nearest community: Ludvika (20 km SW) |
Deposit clan (type): |
Kiruna-type |
Deposit (sub) types: |
stratabound massive magnetite lenses stacked in a sequnece of rhyolite flows and agglomerates; disseminations in the volcanic rocks common; some magnetite occurs as breccia-fillings, veins and dykes; Reference: Magnusson, N. H., 1970: The Origin of the Iron Ores in Central Sweden and the History of their Alterations; Sveriges Geologiska Undersökning, Serie C, Part 1 and 2, Publication code 643, 491 p. magnetite dominant over hematite; both regarded as primary ore minerals; apatite concentrated on the hanging wall side; range up to 9 % P; hematite altered to magnetite near pegmatite veins; Reference: Magnusson, N. H., 1970: The Origin of the Iron Ores in Central Sweden and the History of their Alterations; Sveriges Geologiska Undersökning, Serie C, Part 1 and 2, Publication code 643, 491 p. |
Deposit status: |
past producer; Size category: 100 Mt |
Geologic province: |
Svecofennian Orogen |
Geologic subprovince: |
Southern Svecofennian |
Geologic district: |
Bergslagen (Ore District) |
Commodities: |
Fe |
Mineralization styles: |
massive magnetite lenses; banded; disseminations around massive bodies |
Geological ages: |
Late Paleoproterozoic (host rocks) Late Paleoproterozoic (mineralization) |
Tectonic setting: |
continental marginal arc-fore-arc; convergent; Formal name: Late Svecofennian arc (host rocks) |
Coincident features: |
stratification in host sequence (massive ore lenses nearly concordant with the host strata, but some intrusive features like veins and breccia-fillings) |
Regional tectonic structure: |
folded volcanic sequence (late Svecofennian deformation and metamorphism, followed by emplacement of younger granites) Tectonic structure name: Ludvika-Grängesberg fold belt monoclinal sequence dipping 60 to 65 degrees to the southeast (between two late Svecofenian plutons, a small red granite to the northwest and a large granodiorite to the southeast) |
Host rocks: |
(1) volcanic; felsic volcanic rocks (variably altered potassic and sodic rhyolites); Magma series/sedimentary package/metamorphic group: calc-alkaline; Depositional setting: continental arc; Metamorphic grade: greenschist-amphiboliteExternal host rock forms: | flows, agglomerates | Host rock protoliths: | rhyolites (original composition altred by pervasive alkali metasomatism and skarnification) | Internal host rock structures: | porphyritic, fine grained granular and gneissic | Individual lithologies: | potassic and sodic rhyolites (red potassic rhyolites in the footwall and grey sodic rhyolites in the hanging wall ) |
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Related igneous rocks: |
(1) intrusive; quartz monzonite-monzogabbro suite (post-ore dykes; up to 40 % of ore zones); Magma series: calc-alkaline; Depositional setting: continentalIndividual lithologies: | andesite-dacite (dykes postdate the main phase of mineralization; affected by later deformation and granite intrusions) |
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Country rocks: |
(1) felsic volcanics; (flows, volcaniclastics and sediments); Metamorphic grade: greenschist-amphibolite |
Metallogenic signatures: |
Fe-P |
Alteration signatures: |
potassic alteration: potash feldspar, biotite, muscovite; What was altered: feldspars skarn: garnet, diopside, epidote, calcite, apatite; What was altered: calcareous material, calcic silicates reducing alteration: magnetite; What was altered: hematite |
Mineralogy: |
(alteration): garnet, biotite, chlorite, epidote, muscovite, quartz (mineralization): magnetite, hematite, apatite, actinolite |
Deposit shape: |
zone of stacked tabular bodies and lensesDeposit dimensions: | strike length: 1,400 metres thickness: 90 metres depth: 1,000 metres |
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Qualified comments: |
(Applies to: discovery and development) This deposit was mined from the 16th century to 1910 by open pit 100 m deep; then underground mine to 685 m; approximately 100 Mt of ore mined till closure in 1980s; massive and disseminated ores: range 63 to 45 % Fe. remaining resources at deeper levels of the mine and in the deposits nearby, including other past producers Risbergfältet, Strandbergsfältet, Ormbergfältet and Blötberget, amount to some 100 Mt of ore. |
References: |
Anonymous, 2000 |
Swedish Database of Mineral Deposits |
Email |
Frietsch, R., 1973 |
The Origin of Kiruna Iron Ores |
Geologiska Föreningens i Stockholm Förhandlingar, Volume 95, p. 375 - 380 |
Frietsch, R., 1977 |
The Iron Ore Deposits in Sweden |
in The Iron Ore Deposits of Europe and Adjacent Areas: Explanatory Notes to the International Map of the Iron Ore Deposits of Europe, 1:2,500,000 (Text and Figures), Edited by Walther, H. W.; Zitzmann, A., International Geological Congress, Commission for the Geological Map of the World, Subcommission for the Metallogenic Map of the World, Bundesanstalt fur Geowissenschaften und Rohstoffe, Postfach 51 01 53, D-3000 Hannover 51, Volume I, 418 p, p. 279 - 293 |
Frietsch, R., 1978 |
On the Magmatic Origin of Iron Ores of the Kiruna Type |
Economic Geology, Volume 73, p. 478 - 485 |
Frietsch, R.; Papunen, H., 1986 |
Metallogenesis of the Bergslagen Province and Southwestern Finland |
in Mineral Deposits of Southwestern Finland and the Bergslagen Province, Sweden, Edited by Lundström, I.; Papunen, H., Sveriges Geologiska Undersökning, Ser. Ca, International Association on Genesis of Ore Deposits / 7th IAGOD Symposium and Nordkalott Project Meeting, Geological Survey of Sweden, NR 61, 44 p, p. 11 - 16 |
Magnusson, N. H., 1970 |
The Origin of the Iron Ores in Central Sweden and the History of their Alterations |
Sveriges Geologiska Undersökning, Serie C, Part 1 and 2, Publication code 643, 491 p. |
Zitzmann, A. Editor(s)), 1978 |
The Iron Ore Deposits of Europe and Adjacent Areas: Explanatory Notes to the International Map of the Iron Ore Deposits of Europe, 1:2,500,000 (Lists and Tables) |
International Geological Congress, Commission for the Geological Map of the World, Subcommission for the Metallogenic Map of the World, Bundesanstalt fur Geowissenschaften und Rohstoffe, Postfach 51 01 53, D-3000 Hannover 51, Volume II, 386 p. |
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