Sulphur isotopes from the gruvåsen sulphide skarn deposit, Bergslagen, Sweden

Hellingwerf, Rob H.; Raaphorst, J.G. van

doi:10.1007/bf01164699

Cited by 6 publications

(1 citation statement)

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“…Most studies of S isotope compositions of syngenetic, polymetallic sulfide deposits in Bergslagen have reported relatively narrow δ 34 S ranges: for example, at Hällefors (δ 34 S = -0.6 to 2.7‰; Wagner et al, 2005), Gruvåsen (δ 34 S = -1.4 to 1.5‰; Hellingwerf and van Raaphorst, 1988), Falun (δ 34 S = -2.3 to -0.2‰; Gavelin et al, 1960), and Svärdsjö (δ 34 S = -4.0 to 3.0‰; Billström, 1991). These examples, along with average δ 34 S values close to 0‰, led Wagner et al (2005) to conclude that the majority of these deposits contain S leached from volcanic rocks with or without a direct magmatic-hydrothermal input, whereas S sourced from reduction of seawater SO 4 2was minor.…”

Section: Source Of Sulfurmentioning

confidence: 99%

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%