Cu and Pb–Zn–Ba deposits in the Great Duchy of Luxembourg: role of brines penetrating the basement and place in the post-Variscan tectonic history of Western Europe - Université de Lorraine Accéder directement au contenu
Article Dans Une Revue International Journal of Earth Sciences Année : 2023

Cu and Pb–Zn–Ba deposits in the Great Duchy of Luxembourg: role of brines penetrating the basement and place in the post-Variscan tectonic history of Western Europe

Résumé

The Great Duchy of Luxembourg comprises a Variscan basement, part of the Ardennes-Rhenish fold-and-thrust belt and an unconformable Mesozoic sedimentary cover representative of the eastern margin of the Paris Basin. The basement hosts several vein-type ore deposits, which remain almosundocumented until now, except for a few geological and mineralogical descriptions. The Stolzembourg Cu-deposit and the Martelange and Soleuvre Pb-Zn-Ba deposits occur at the boundary of several ore deposit provinces in Belgium and Germany. By coupling the mineralogy of fracture infillings and P-T-X reconstruction thanks to a detailed fluid inclusion study, the primary fluid events and associated metal transfer and deposition are described and compared with other Mesozoic deposits in the nearby areas. At Stolzembourg copper-only deposit, the anisothermal mixing between two highly saline (a Ca-Na and a Na-only rich end-member) fluids of ca.27 wt % eq NaCl and low-salinity water resulted in the chalcopyrite-Fe-dolomite deposition. The process occurred at temperatures ranging from c. 160°C to c.140°C under hydrostatic conditions at a depth of around 3 km. By contrast, the quartz preceding and following copper deposition recorded a circulation of lower-temperature brines. The copper fluid event was thus related to a transient heat advection and brine convection. Such an event is likely the Mid-Cretaceous thermal event detected at the scale of Western Europe in response to the coeval openings of the Biscaye Bay (to the west) and Valaisan (to the east) oceanic tracts. This event occurred between 130 and 100 Ma and is synchronous with a series of ore deposits in Western Europe. Similar to the Ardennes Pb-Zn deposits, the small Pb-Zn showings would probably have been formed simultaneously in the same conditions. The Hercynian basement in Luxembourg follows a similar history to other West-European Variscan massifs after peneplaination, particularly the penetration of brines, probably in part issued from Trias formations, during a series of stages linked to major Mesozoic geodynamic events.
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hal-04272625 , version 1 (06-11-2023)

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Christian Marignac, Michel Cathelineau, Olivier Belcourt, Simon Philippo. Cu and Pb–Zn–Ba deposits in the Great Duchy of Luxembourg: role of brines penetrating the basement and place in the post-Variscan tectonic history of Western Europe. International Journal of Earth Sciences, 2023, 112 (6), pp.1771-1801. ⟨10.1007/s00531-023-02325-2⟩. ⟨hal-04272625⟩
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