Genesis of the Falun sulphide ores, central Sweden

Gavelin, Sven

doi:10.1080/11035898909452704

Cited by 4 publications

(4 citation statements)

References 7 publications

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“…Sheath folds have been identified in the massive sulphides, resulting in stretched and steeply plunging, rodshaped geometries, which extend down to approximately 450 m below sea-level (Kampmann et al, 2016). This also explains the thinning of massive sulphide bodies and associated convergence of rock units, including the porphyritic felsic dykes, towards the base of the deposit (Gavelin, 1989;Kampmann et al, 2016).…”

Section: Falun Zn-pb-cu-(au-ag) Sulphide Depositmentioning

confidence: 92%

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Kampmann

Stephens

Ripa

et al. 2016

Precambrian Research

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a b s t r a c t U-Th-Pb (zircon and monazite) ion probe data have provided constraints on the timing of emplacement and metamorphism of magmatic rocks close to the Palaeoproterozoic, Falun base metal sulphide deposit in the Bergslagen lithotectonic unit, Fennoscandian Shield, Sweden, and, thereby the timing of mineralisation. Hydrothermal alteration and mineralisation at Falun are constrained to a short interval of several million years between a 207 Pb/ 206 Pb weighted average age of 1894 ± 3 Ma for a rhyolitic sub-volcanic rock in the felsic volcanic to sub-volcanic host rock suite, and a 207 Pb/ 206 Pb weighted average age of 1891 ± 3 Ma for a post-sulphide, porphyritic dacite dyke. Magmatism also included the emplacement of granite plutons with igneous crystallization ages of 1894 ± 3, 1894 ± 2 Ma and 1893 ± 3 Ma. The felsic sub-volcanic to volcanic activity and the emplacement of dacite dykes and granite plutons overlap in age within their respective analytical uncertainties, indicating hydrothermal alteration and sulphide mineralisation inside a narrow time span of intense magmatic activity, and burial of the supracrustal rocks. Two distinct patchy and homogeneous metamorphic monazite types in a felsic volcanic rock around and hydrothermally altered rocks at the Falun deposit yield 207 Pb/ 206 Pb weighted average ages of 1831 ± 8 Ma and 1822 ± 5 Ma, respectively. These ages fall well within the temporal range of a younger 1.84-1.81 Ga (M 2 ) metamorphic episode during the 2.0-1.8 Ga Svecokarelian orogeny, with the older episode (M 1 ) inside the Bergslagen lithotectonic unit at around 1.86 Ga. This shows the major influence of the M 2 event in the north-western part of this unit, leading to a complete resetting of the U-Th-Pb isotope system in monazite.

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Section: Falun Zn-pb-cu-(au-ag) Sulphide Depositmentioning

confidence: 92%

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Kampmann

Stephens

Ripa

et al. 2016

Precambrian Research

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“…Geijer (1927Geijer ( , 1961 interprets the high MgO contents to be the result of regional 'magnesia metasomatism' related to granitic emplacements, although the source of Mg is now considered to be the result of dedolomitization (e.g. Gavelin, 1989) or sea-water interaction (Baker etal., 1988). The minor rare earth mineralization at Koberg is related to, and contemporaneous with these cerium deposits, where the origin of the REE bearing fluids, although uncertain, is probably related to local hydrothermal systems restricted to narrow, structurally-controlled zones of high fluid flow (see e.g.…”

Section: -mentioning

confidence: 99%

“…Although the mine is no longer accessible, on the mine dumps the most common rock types to be found are a pure white limestone marble, a light-green coloured skarn material, and intergrowths of these two types. Less common are blocks of dolomite, diabase, mica-rich fracture filling 'skOl' (an alteration product consisting of almost pure biotite, muscovite, chlorite, +talc and minor cordierite, almandine and anthophyllite; Gavelin, 1989) and sulphide ore.…”

Section: Introductionmentioning

confidence: 99%

Rare-earth minerals yttrian zirconolite and allanite-(Ce) and associated minerals from Koberg mine, Bergslagen, Sweden

Zakrzewski¹,

Lustenhouwer²,

Nugteren³

et al. 1992

Mineral. mag.

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A study of mine dump material from Koberg, Bergslagen, Sweden has revealed a varied mineral assemblage, including Zr-, REE-, Th- and U-bearing minerals associated with the sulphide ore deposit. Detailed descriptions and microprobe analyses are presented of the rare earth minerals yttrian zirconolite and allanite-(Ce), and the zirconium oxide baddeleyite. Yttrian zirconolite is patchily zoned in the actinide elements Th and U, and the low analytical totals suggest the presence of several weight per cent of H2O. The implications of these features with respect to synthetic zirconolite in SYNROC and to radioactive waste management are briefly discussed. Chemical zoning of individual REE in yttrian zirconolite is described and the REE distribution compared with those of zirconolites from other localities. Allanite-(Ce) is generally unzoned, but contains REE-rich rims which are considered to be sub-micron intergrowths of allanite plus a bastnäisite-type mineral phase. The MgO content of allanite-(Ce) is unusually high and appears to be a characteristic feature of allanite from other cerium and mineral occurrences of Central Sweden. The rare earth minerals at Koberg are interpretated as having been formed as a result of localized remobilization of elements including Ti and Zr with H2O- and CO2-rich fluids.

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“…Genetic models for the deposit, established during the previous century (Geijer, 1917;Koark, 1962), are in need of revision. More recent studies have either a more regional focus (Kresten, 1985;Bromley-Challenor, 1988;Smeds, 1994), or investigated specific aspects of the Falun deposit (Weijermars, 1987;Gavelin, 1989;Åberg and Fallick, 1993).…”

Section: Introductionmentioning

confidence: 99%

Systematics of Hydrothermal Alteration at the Falun Base Metal Sulfide Deposit and Implications for Ore Genesis and Exploration, Bergslagen Ore District, Fennoscandian Shield, Sweden

Kampmann

Jansson

Stephens

et al. 2017

EconGeo

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The Paleoproterozoic Falun Zn-Pb-Cu-(Au-Ag) pyritic sulfide deposit in the Bergslagen ore district, Sweden, is enveloped by hydrothermally altered rocks metamorphosed to the lower amphibolite facies. Immobile-element ratios suggest that the alteration precursors were volcanic rocks of mainly rhyolitic to dacitic composition. Least altered examples of these rocks plot along magmatic fractionation trends outlined by late-to post-ore feldsparphyric metadacite dikes and post-ore granitoid plutons, consistent with a comagmatic relationship between these calc-alkaline, coeval (<10-m.y.) suites. Dolomite or calcite marble, as well as diopside-hedenbergite or tremolite skarn, form subordinate but important lithologic components in the hydrothermally altered zone. Marble occurs as fragments in the massive pyritic sulfide mineralization, suggesting that at least some mineralization formed by carbonate replacement. Mass-change calculations suggest that the hydrothermally altered volcanic rocks gained Mg and Fe and generally lost Ca, K, and Na. Proximal, quartz-anthophyllite-rich altered rocks additionally gained Si, whereas several types of biotite-rich altered rocks lost this element. These mass changes along with mineral chemical data for anthophyllite, biotite, cordierite, and garnet, and the common occurrence of quartz indicate that chloritization, sericitization, and silicification were the dominant premetamorphic alteration styles. A zonation from distal sericitized and silicified volcanic rocks to intermediate sericitized rocks, partly overprinted by chloritization (Mg-rich chlorite), and proximal siliceous and intensely chloritized (Fe-rich chlorite) rocks has been identified. Furthermore, mass changes in more peripheral parts of the altered zone toward the southeast of the deposit suggest that the alteration weakens gradationally toward the volcanic and subvolcanic rocks surrounding the deposit. These patterns represent vectors toward mineralization. Intensely chloritized rocks, largely represented by a single, rhyolitic precursor, envelop the central pyritic massive sulfide bodies to the east, south, and west, supporting a structural model in which the massive sulfide mineralization formed the stratigraphically highest preserved unit in the center, surrounded in a tubular manner by stratigraphic footwall rocks. The northern side represents a portion of the footwall, which was separated by a major shear zone. These spatial relationships also have implications for near-mine exploration, since quartz-rich footwall rocks locally host disseminated to semimassive stockwork Cu-Au mineralization. Cooling of a hot (300°-400°C), acidic (pH ≤4) and reducing fluid carrying metals and sulfur is suggested for formation of stockwork Cu-Au vein mineralization and hydrothermal alteration in the stratigraphic footwall. The Zn-Pb-Cu-rich massive sulfide mineralization is inferred to have formed by fluid neutralization upon interaction with carbonates and mixing with cooler seawater upon fluid entry into porous pumice breccia in a su...

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Genesis of the Falun sulphide ores, central Sweden

Cited by 4 publications

References 7 publications

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Time constraints on magmatism, mineralisation and metamorphism at the Falun base metal sulphide deposit, Sweden, using U–Pb geochronology on zircon and monazite

Rare-earth minerals yttrian zirconolite and allanite-(Ce) and associated minerals from Koberg mine, Bergslagen, Sweden

Systematics of Hydrothermal Alteration at the Falun Base Metal Sulfide Deposit and Implications for Ore Genesis and Exploration, Bergslagen Ore District, Fennoscandian Shield, Sweden

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