Genesis of the Zinkgruvan stratiform Zn-Pb-Ag deposit and associated dolomite-hosted Cu ore, Bergslagen, Sweden

Jansson, Nils; Zetterqvist, Anders; Allen, Rodney L.; Billström, Kjell; Malmström, Lars

doi:10.1016/j.oregeorev.2016.12.004

Cited by 31 publications

(42 citation statements)

References 48 publications

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“…However, the data yield an average of 2.0‰, and 75% of the data yielded δ 34 S between -3.0 and 3.0‰. Jansson et al (2017) suggested that Zinkgruvan formed upon venting of oxidized (SO 4 2-> H2S), metalliferous brines at a near-neutral pH into a reduced brine pool. The source of S at Zinkgruvan was interpreted as a mixture of S leached from volcanic rocks (δ 34 S ≈ 0‰) and H2S derived from abiotic or bacterial sulfate reduction of contemporaneous seawater SO 4 2-(δ 34 S ≈ 17‰).…”

Section: Source Of Sulfurmentioning

confidence: 99%

“…Two samples from the Lovisa Fe formation, however, have Sc/Th lower than normal pelitic rocks, implying a contribution from more maficintermediate volcaniclastic material. Bergslagen mafic rocks based on data in Johansson and Hålenius (2013), Bergslagen pelite based on data in Jansson et al (2017), N. Jansson (unpub. data, 2017), and Post-Archean Australian Shale values from Taylor and MacLennan (1985).…”

Section: Genesis Of the Fe Formationsmentioning

confidence: 99%

“…As in other stratiform deposits in Bergslagen (e.g., Zinkgruvan), we find that the mineralogy and textures can be explained by regional metamorphism of preexisting hybrid rock types containing a variable content of quartz, feldspars, phyllosilicates, Fe oxides, and carbonates (cf. Hedström et al, 1989;Jansson and Allen, 2011;Jansson et al, 2013Jansson et al, , 2017.…”

Section: Genesis Of the Sulfide Depositsmentioning

confidence: 99%

“…It would then be difficult to explain how the ascending hydrothermal fluid could traverse the Håkansboda limestone without losing most of its base metal content upon neutralization (cf. Jansson et al, 2017). Neutralization of hot, acidic hydrothermal fluids carrying metals and H2S together has been demonstrated as a highly efficient mechanism for forming massive, stratabound limestone-and skarn-hosted polymetallic sulfide deposits elsewhere in Bergslagen, such as at Stollberg (Jansson et al, 2013) and Falun (Kampmann et al, 2017).…”

Section: Source Of Sulfurmentioning

confidence: 99%

“…Zinkgruvan has variably been classified as a Broken Hilltype deposit (e.g., Beeson, 1990;Walters, 1996), sedimentary-exhalative (SEDEX) deposit (Hellingwerf, 1996), volcanogenic massive sulfide (VMS) deposit (Billström, 1991), and a VMS-SEDEX hybrid (Hedström et al, 1989). Recently, Jansson et al (2017) argued that the deposit formed upon exhalation of oxidized saline brines at a near-neutral pH into a reduced (H2S > SO 4 2-) water column above a thick succession of dominantly felsic volcanic rocks. The inferred fluid chemistry differs from typical VMS models, Selwyn-type SEDEX models, and most fluid models for Broken Hill but has similarities to MacArthur-type SEDEX models (cf.…”

Section: Introductionmentioning

confidence: 99%

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The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

et al. 2018

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Medium-to high-grade metamorphosed, 1.9 Ga, stratiform, syngenetic Zn-Pb ± Ag sulfide deposits constitute an economically important type of ore deposit in the Bergslagen lithotectonic unit of the Fennoscandian Shield. The Lovisa Zn-Pb deposit occurs in a metamorphosed succession of rhyolitic ash-siltstone, rhyolitic mass flow deposits, limestone, and Fe formation, deposited at a stage of waning volcanism in Bergslagen. Accessory graphite, absence of Ce anomalies in shale-normalized rare earth element (REE) data, and absence of hematite in Mn-rich Fe formations stratigraphically below the Lovisa Zn-Pb deposit indicate a suboxic-anoxic depositional environment. The uppermost Mn-rich Fe formation contains disseminated, inferred syngenetic Pb-Ag mineralization with mainly negative δ 34 S values in sphalerite and galena (-6.1 to-1.9‰). Deposition of this Fe formation terminated during a pulse of explosive felsic volcanism. The Lovisa Zn-Pb deposit is interpreted to have formed in an alkali-rich brine pool developed immediately after this volcanic event, based on lithogeochemical and stratigraphic evidence. The first stage of mineralization deposited stratiform sphalerite mineralization with mainly positive δ 34 S values (-0.9 to 4.7‰). This was succeeded by deposition of more sphalerite-galena stratiform mineralization with δ 34 S values close to 0‰ (-2.1 to 1.5‰). The more galena-rich mineralization partitioned strain and was partly remobilized during later ductile deformation. The stratigraphic context, sulfide mineralogy, S isotopes, and alteration geochemistry suggest that the metalliferous fluids and the depositional environment were H2S deficient (S poor or SO 4 2dominant). The source of S is interpreted to have been a mixture of H2S derived from bacterial and thermochemical seawater sulfate reduction and S derived from leaching of volcanic rocks, with the latter becoming more important over time. Lovisa formed in a setting where basin subsidence was periodically punctuated by the deposition of thick, syneruptive felsic volcaniclastic mass flow deposits. Coeval volcanism was likely important for driving hydrothermal activity and supplying a reservoir of metals and S. However, the high rate of deposition of volcaniclastic sediment in Bergslagen also precluded the establishment of long-lived, deep, and anoxic environments favorable for accumulation of organic matter and H2S. This stratigraphic pattern is common in Bergslagen and may explain why large stratiform Zn-Pb deposits are uncommon in the region and restricted to the uppermost part of the metavolcanic succession, directly stratigraphically beneath postvolcanic pelitic rocks.

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Section: Source Of Sulfurmentioning

confidence: 99%

Section: Genesis Of the Fe Formationsmentioning

confidence: 99%

Section: Genesis Of the Sulfide Depositsmentioning

confidence: 99%

Section: Source Of Sulfurmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

et al. 2018

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Origin of Palaeoproterozoic, sub-seafloor Zn-Pb-Ag skarn deposits, Sala area, Bergslagen, Sweden

Jansson

Allen²,

Skogsmo³

et al. 2021

Miner Deposita

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Unravelling the genesis of metamorphosed mineral deposits can be complicated due to difficulties in separating between primary features and features that formed during the metamorphic overprint. Such uncertainty exists for stratabound and dolomite- and skarn-hosted Zn-Pb-Ag sulfide deposits in 1.89 Ga rocks in the Bergslagen lithotectonic unit (BLU) of Sweden, where a metasomatic vs. regional metamorphic origin for skarns has long been discussed. By integrating geological mapping with new lithogeochemical, mineralogical, and stable isotope data (C, O, S), we show that complexly zoned garnet and clinopyroxene skarns in the Sala area of the central BLU predate mineralization. Sphalerite-galena mineralization formed after the deposition of a younger, more Mn-rich ferroan diopside and andradite-grossular garnet, and is associated with phlogopite, tremolite-actinolite, chlorite, serpentine, and calcite. Mineralization in conjunction with a transition from high-T metasomatism to hydrolytic alteration is inferred. An average δ34SV-CDT of 1.6 ± 1.9‰ in sulfides is consistent with a primordial sulfur source. Trends defined by negative shifts in δ18OV-SMOW and δ13CV-PDB in dolomite and calcite are consistent with fluid infiltration at 300–500 °C. The alteration system is sharply truncated by unaltered, c. 1.89 Ga calc-alkaline granite and porphyritic intrusions, which along with F1 folding of the alteration zones and mineralization suggest that mineralization predate regional metamorphism. The Sala deposits are interpreted as Zn skarn deposits formed in conjunction with the emplacement of intrusions into penecontemporaneous marine volcanic and dolomitized limestone strata. The unusually Mg-rich mineralogy in relation to Zn skarns worldwide most likely reflects the dolomitic precursor.

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Types of ore deposits and their origin

Macheyeki¹,

Kafumu³

et al. 2020

Applied Geochemistry

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Genesis of the Zinkgruvan stratiform Zn-Pb-Ag deposit and associated dolomite-hosted Cu ore, Bergslagen, Sweden

Cited by 31 publications

References 48 publications

The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis

Origin of Palaeoproterozoic, sub-seafloor Zn-Pb-Ag skarn deposits, Sala area, Bergslagen, Sweden

Types of ore deposits and their origin

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