The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany

Insight from detailed sulfur isotope studies

verfasst von: Thomas Wagner, Martin Okrusch, Stefan Weyer, Joachim Lorenz, Yann Lahaye, Heiner Taubald, Ralf T. Schmitt
Abstract: The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ³⁴S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between -44.5‰ and -3.9‰, whereas the δ³⁴S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ³⁴S values, whereas vein-type deposits have consistently more negative δ³⁴S values. The observed pattern of sulfide δ³⁴S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ³⁴S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ³⁴S values.
Externe Organisation(en): ETH Zürich
Julius-Maximilians-Universität Würzburg
Goethe-Universität Frankfurt am Main
Eberhard Karls Universität Tübingen
Humboldt-Universität zu Berlin (HU Berlin)
Typ: Artikel
Journal: Mineralium deposita
Band: 45
Seiten: 217-239
Anzahl der Seiten: 23
ISSN: 0026-4598
Publikationsdatum: 03.2010
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Geophysik, Geochemie und Petrologie, Ökonomische Geologie
Elektronische Version(en): https://doi.org/10.1007/s00126-009-0270-2 (Zugang: Unbekannt)

BibTeX

@article{4349c40709ba440d84fa2636b7e99fe3,
title = "The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany: Insight from detailed sulfur isotope studies",
abstract = "The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ34S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between -44.5‰ and -3.9‰, whereas the δ34S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ34S values, whereas vein-type deposits have consistently more negative δ34S values. The observed pattern of sulfide δ34S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ34S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ34S values.",
keywords = "Base metals, Germany, Kupferschiefer, Laser-ablation MC-ICP-MS, Sulfur isotopes",
author = "Thomas Wagner and Martin Okrusch and Stefan Weyer and Joachim Lorenz and Yann Lahaye and Heiner Taubald and Schmitt, {Ralf T.}",
note = "Funding information: This project was made possible by funding from the German Research Council (DFG). The mineral concentrates were carefully prepared by Maria Kirchenbaur (W{\"u}rzburg). Uli Sch{\"u}ssler (W{\"u}rzburg) is thanked for his help and assistance during electron-microprobe analysis. The conventional sulfur isotope analyses were performed with the assistance of Bernd Steinhilber (T{\"u}bingen), whose help is gratefully acknowledged. Further thanks are due to Klaus-Peter Kelber (W{\"u}rzburg) for the microphotographs and Peter Sp{\"a}the (W{\"u}rzburg) for the preparation of the polished sections. Adrian Boyce and Bernd Lehmann are thanked for their constructive comments that have helped to improve our paper.",
year = "2010",
month = mar,
doi = "10.1007/s00126-009-0270-2",
language = "English",
volume = "45",
pages = "217--239",
journal = "Mineralium deposita",
issn = "0026-4598",
publisher = "Springer Verlag",
number = "3",
}