Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

Billström, Kjell; Broman, Curt; Schneider, Jens; Pratt, Warren; Skogsmo, Göran

doi:10.3390/min2030169

Cited by 16 publications

(19 citation statements)

References 45 publications

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“…Recalculated isochron model age diagram (n = 4) for residues and corresponding leachates of sphalerite samples from the basement-hosted Ersmarksberget and Gubbträsk vein deposits and the basement-hosted Åkerlandet vein deposit. (Billström et al, 2012;Saintilan et al, 2012), it seems reasonable to try to combine our Åkerlandet data with those published for the Ersmarksberget and Gubbträsk deposits by Billström et al (2012).…”

Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 79%

“…If so, the following possibility merits some exploration. Billström et al (2012) presented a tentative four-point Rb-Sr isochron age of 531 ± 6.5 Ma (Lower Cambrian; initial 87 Sr/ 86 Sr = 0.716560 ± 660) for sphalerite residues (MSWD = 2.4) from the basement-hosted Ersmarksberget, Svärtträsk, and Gubbträsk vein deposits in the Storuman district, 100 km north of Åkerlandet (Fig. 1A).…”

Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 98%

“…These authors described calcite-fluorite-Zn-Pb sulfide mineralization at Ersmarksberget and Gubbträsk along brittle structures partly discordant to the regional ductile fabric. Given the similarities in mineralogy, texture, and tectonic structures in the host basement rocks at the Ersmarksberget, Gubbträsk, and Åkerlandet deposits Billström et al, 2012), (ii) the Åkerlandet deposit (this study). The sphalerite residues from the Lower Sandstone orebody at Laisvall are shown for reference.…”

Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 99%

“…1A). In all cases, lead isotope studies suggest that Pb in galena was derived from local Precambrian basement rocks (Johansson, 1983a;Johansson and Rickard, 1984;Lindhal and Bjørlykke, 1988;Sundblad, 1990;Romer and Wright, 1993;Billström et al, 2012).…”

Section: Strata-bound Sandstone-hosted Pb-zn Deposit In Autochthonousmentioning

confidence: 96%

“…1A) are hosted by Paleoproterozoic (1.9 Ga) metasedimentary rocks intruded by Revsund granite (1.8 Ga), and Paleoproterozoic (1.9 Ga) migmatitic paragneiss and homogeneous leucocratic granite, respectively (Bergman et al, 2012). The vein deposits are located in brittle structures along shear zones with N-S to NE-SW trends and both strike-slip and dip-slip components of movement (Billström et al, 2012;Saintilan et al, 2012). Johansson (1983bJohansson ( , 1984 and Billström et al (2012) proposed that these vein deposits formed by the mixing of a hot (160°-200°C) saline hydrothermal fluid with a cooler (<70°C), less saline fluid.…”

Section: Calcite-galena Vein Deposits In the Basementmentioning

confidence: 98%

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A Middle Ordovician Age for the Laisvall Sandstone-Hosted Pb-Zn Deposit, Sweden: A Response to Early Caledonian Orogenic Activity

Saintilan¹,

Schneider²,

Stephens³

et al. 2015

Economic Geology

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Ten sphalerite separates isolated from mineralized samples in proximal and distal positions relative to the proposed main feeder fault systems at the Laisvall deposit were used to obtain an absolute age determination of this world-class Pb-Zn deposit hosted by autochthonous Ediacaran to Lower Cambrian sandstone and located currently along the erosional front of the Scandinavian Caledonides in northern Sweden. Residue and leachate fractions of each separate were obtained using the crush-leaching technique. All samples correspond to sphalerite formed using reduced sulfur derived from thermochemical sulfate reduction, three of them from disseminated ore in the Lower Sandstone, two from the disseminated ore in the Upper Sandstone, and five from steeply dipping galena-sphalerite-calcite veinlets interpreted in previous works as remobilization of disseminated ores. The isotope dilution-thermal ionization mass spectrometry (ID-TIMS) data yield an overall complex Rb-Sr isotope pattern with two distinct trends in the 87 Sr/ 86 Sr vs. 87 Rb/ 86 Sr isochron diagram. The three sphalerite residues of disseminated mineralization from the Lower Sandstone orebody show Rb-Sr isotope systematics indicative of undisturbed primary precipitates, and yield an isochron model age of 467 ± 5 Ma (mean square weighted deviation, MSWD, 1.4). Since the isochron is based on three points, the obtained age is to be considered as preliminary. Yet, the obtained age is fully consistent with geologic evidence reported by previous authors and pointing to Middle Ordovician timing of ore formation.The ID-TIMS data were complemented by laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analyses on the same sphalerite samples. The data support the hypothesis that the measured ID-TIMS Rb and Sr contents in these sphalerite residues are held in the sphalerite structure itself and are not related to micro-inclusions. The most viable hypothesis, in agreement with published work, is that during rapid growth, sphalerite may incorporate Rb and Sr ions from the hydrothermal fluids in its structure, most probably in octahedral voids.By contrast, the second trend in the 87 Sr/ 86 Sr vs. 87 Rb/ 86 Sr space defined by most other sphalerite residues and corresponding inclusion fluid leachates from the Upper Sandstone orebody and the veinlet samples is too steep to account for a realistic isochron age determination. This steep linear trend is interpreted to represent a postmineralization disturbance involving fluids rich in Sr. This disturbance of the Rb-Sr isotope system is consistent with the presence of the steeply dipping galena-sphalerite-calcite veinlets and the fact that the Upper Sandstone is, in places, tectonically disrupted because of its proximity to the basal Caledonian décollement. The attempt to date the Granberget deposit, located in tectonically disrupted allochthonous units inside the Caledonian orogen, failed because the Rb-Sr isotope systematics of the three analyzed sphalerite samples are also disturbed.The obtained Middle Ord...

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Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 79%

Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 98%

Section: Interpretation Of the Results From The åKerlandet Vein Depositmentioning

confidence: 99%

Section: Strata-bound Sandstone-hosted Pb-zn Deposit In Autochthonousmentioning

confidence: 96%

Section: Calcite-galena Vein Deposits In the Basementmentioning

confidence: 98%

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A Middle Ordovician Age for the Laisvall Sandstone-Hosted Pb-Zn Deposit, Sweden: A Response to Early Caledonian Orogenic Activity

Saintilan¹,

Schneider²,

Stephens³

et al. 2015

Economic Geology

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Polyphase vein mineralization in the Fennoscandian Shield at Åkerlandet, Järvsand, and Laisvall along the erosional front of the Caledonian orogen, Sweden

et al. 2016

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The Åkerlandet, Järvsand, and Laisvall deposits in Sweden are calcite-fluorite-sulfide vein deposits and occurrences located close to the current erosional front of the Caledonian orogen and hosted by crystalline basement rocks in the Fennoscandian Shield. At Laisvall, basement-hosted veinlets occur beneath Ediacaran to Cambrian sandstones that host a strata-bound Pb-Zn deposit. The mineralized fractures at Åkerlandet and Järvsand occur along fault systems oriented N–S to NNW–SSE. Veins or veinlets strike NNW–SSE and NW–SE at Åkerlandet, NNE–SSW at Järvsand, and NNW–SSE and NNE–SSW to NE–SW at Laisvall. At Åkerlandet and Järvsand, fractures acted as conduits for hydrothermal fluids of variable composition and formed during separate tectonic events. At Åkerlandet, the fault zone with NNW–SSE strike shows kinematic indicators consistent with ~NE–SW bulk horizontal extension. At Järvsand, the calcite-fluorite-galena veins formed along R-Riedel shears related to the host N–S to NNW–SSE fault system. The kinematic indicators are consistent with ~NW–SE bulk horizontal extension, similar to the extensional deformation during the later part of the Caledonian orogeny (Silurian to Devonian). At Åkerlandet, adularia-quartz deposition was followed by sphalerite ± galena and finally by precipitation of fluorite and calcite. 40Ar-39Ar thermochronology of a single adularia sample did not yield a well-defined plateau age but the gas released at higher temperatures suggests an early Tonian (980 to 950 Ma) crystallization age, i.e., during the later part of the Sveconorwegian orogeny, although the data do not exclude other less likely interpretations. Previous fluid inclusion microthermometry and geochronological studies and new petrographic and geochemical results suggest that sphalerite ± galena mineralization formed from saline, relatively oxidizing, moderate-temperature, and slightly acidic hydrothermal fluids, either during the Ediacaran or the Middle Ordovician. Metals and H2S were derived from local basement rocks. Based on petrographic evidence, rare earth element composition, and S, C, and O isotope data, fluorite and calcite precipitated under near neutral and relatively reducing conditions. Occurrence of solid bitumen in veins at Åkerlandet and C and O isotope data of calcite at Åkerlandet and in the Laisvall basement veinlets suggest that the precipitation of calcite and fluorite was triggered by interaction of hot and evolved hydrothermal fluids (87Sr/86Sr = 0.718–0.732) with organic matter. Structural, petrographic, and geochemical data at Laisvall suggest that the basement structures hosting calcite-fluorite ± pyrite veinlets were utilized in the Middle Ordovician as the plumbing system for the oxidizing, slightly acidic, metal-bearing brines that caused the economic Pb-Zn mineralization in the overlying sandstones

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An early Cambrian post-rift basin within the Baltica–Iapetus passive margin (north-central Scandinavian Caledonides)

Greiling,

Kathol,

Kumpulainen

2023

Int J Earth Sci (Geol Rundsch)

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Field data from recent geological mapping over a major part of the north-central Scandinavian Caledonides combined with published information give a detailed view of early Cambrian basin successions, comprising the Gärdsjön formation (Gf; Jämtland supergroup) in the Lower Allochthon and autochthonous equivalents (Dividal Group). The Gf comprises ten units of sandstone and siltstone or mudstone (Gf I—X, > 300 m thick). Green siltstones with red layers (Gf VI, c. 521 to 519 Ma) and green–grey siltstones at the top (Gf X, c. 516.5 to 513.5 Ma) are regional key horizons. Gf V, VI, VII, IX, and X deposition may be related to eustatic events. Restoration of Caledonian shortening reveals a major “Hornavan-Vattudal basin” (HVB; > 330 km NW–SE, > 400 km NE-SW) between the Grong–Olden culmination in the S and the Akkajaure–Tysfjord culmination in the N. Published zircon ages imply the latter separated the HVB from those shed from the Timan orogen in the N. The eastern basin margin straddles the present Caledonian erosional margin. Basement highs identified here within the Nasafjället, Bångonåive, and Børgefjellet “basement” windows define the western margin. They separate the HVB from the outer shelf towards the Iapetus Ocean in the W. The onset of sedimentation is time-related with E–W extension at c. 544–534 Ma. NNE–SSW-directed extension occurs after c. 518 Ma, perhaps related with Timan late-orogenic extension. The HVB is distinctly younger (c. 535–513.5 Ma) than Rodinia break-up and Iapetus ocean formation (> 550 Ma), comparable with post-rift basins in inner parts of modern passive margins. Graphical Abstract

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Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

Cited by 16 publications

References 45 publications

A Middle Ordovician Age for the Laisvall Sandstone-Hosted Pb-Zn Deposit, Sweden: A Response to Early Caledonian Orogenic Activity

A Middle Ordovician Age for the Laisvall Sandstone-Hosted Pb-Zn Deposit, Sweden: A Response to Early Caledonian Orogenic Activity

Polyphase vein mineralization in the Fennoscandian Shield at Åkerlandet, Järvsand, and Laisvall along the erosional front of the Caledonian orogen, Sweden

An early Cambrian post-rift basin within the Baltica–Iapetus passive margin (north-central Scandinavian Caledonides)

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