The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis
| العنوان: | The Lovisa Stratiform Zn-Pb Deposit, Bergslagen, Sweden: Structure, Stratigraphy, and Ore Genesis |
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| المؤلفون: | Stefan Sädbom, Nils Jansson, Paul Spry, Kjell Billström, Rodney Allen |
| المصدر: | Economic Geology. 113:699-739 |
| بيانات النشر: | Society of Economic Geologists, 2018. |
| سنة النشر: | 2018 |
| مصطلحات موضوعية: | chemistry.chemical_classification, iron oxide, sulfide, 010504 meteorology & atmospheric sciences, Sulfide, Bergslagen, Geochemistry, Geology, 010502 geochemistry & geophysics, 01 natural sciences, Geophysics, Ore genesis, Stratigraphy, chemistry, Geochemistry and Petrology, VMS, Geologi, Economic Geology, SEDEX, 0105 earth and related environmental sciences |
| الوصف: | Medium- to high-grade metamorphosed, 1.9 Ga, stratiform, syngenetic Zn-Pb±Ag sulfide deposits comprise 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 iron 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 iron formations stratigraphically below the Lovisa Zn-Pb deposit indicate a suboxic-anoxic depositional environment. The uppermost Mn-rich iron formation contains disseminated, inferred syngenetic Pb-Ag mineralization with mainly negative δ34S values in sphalerite and galena (-6.1 to -1.9‰). Deposition of this iron 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 δ34S values (-0.9 to +4.7‰). This was succeeded by deposition of more sphalerite-galena stratiform mineralization with δ34S 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, sulfur isotopes and alteration geochemistry suggest that the metalliferous fluids and the depositional environment were H2S-deficient (S-poor or SO42--dominant). The source of sulfur is interpreted to have been a mixture of H2S derived from bacterial and thermochemical seawater sulfate reduction, and sulfur 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, syn-eruptive felsic volcaniclastic massflow deposits. Coeval volcanism was likely important for driving hydrothermal activity and supplying a reservoir of metals and sulfur. 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 post-volcanic pelitic rocks. Validerad;2018;Nivå 2;2018-05-04 (andbra) Conceptual modelling and exploration criteria for stratiform Zn-Pb-Ag-(Cu) Deposits in Bergslagen, Sweden |
| وصف الملف: | application/pdf |
| تدمد: | 1554-0774 0361-0128 |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::2ad2827920303fc2d5a60fd3fabcdad5Test https://doi.org/10.5382/econgeo.2018.4567Test |
| حقوق: | OPEN |
| رقم الانضمام: | edsair.doi.dedup.....2ad2827920303fc2d5a60fd3fabcdad5 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 15540774 03610128 |
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