4D Geomodelling A Tool for Exploration—The Kupferschiefer in The Lubin Region, Poland
Résumé
The Polish Kupferschiefer, with sediment-hosted polymetallic (Cu, Ag, Au, PGE) deposits, is one of the most important sources for copper and silver in the world. Within the framework of the ProMine project, the Lubin region (southwestern Poland), was selected for modelling the geological formations in 3 dimensions and 4 dimensions in order to better understand the distribution of the Cu-Ag mineralization, and possibly to define new potentials. The restoration—decompaction methodology available in gOcad, coupled with PetroMode 1D, were used to reconstruct the temperatures, pressures, hydraulic fracturing favourable conditions, and oil and gas maturation during the burying history of the Lubin Kupferschiefer, Southwestern Poland basin. Conditions for hydraulic fracturing were identified for the base of the Zechstein shales, during an inversion phase at the Late Cretaceous-Early Palaeocene. This Late Cretaceous up lift yields the conditions for hydrothermal recirculation of mineralizing brines explaining the location of Cu (Cu-Fe) sulphides ores in the area. The Zechstein evaporite series played a role of impermeable cover confining the hydrothermal fluids in the lower Zechstein series. The 4D restoring-decompacting modelling allows for reconstructing the burial, deformation and natural hydro-fracturing history of intra-basin sediment-hosted ore deposits. In the Lubin region, the obtained results show a good agreement between the spatial hydro-fracturing index and the emplacement of the Cu (Cu-Fe) sulphides exploited today.