A Mid‐Triassic paleomagnetic age of the Kupferschiefer mineralization in Poland, based on a revised apparent polar wander path for Europe and Russia
Authors: Jowett E. Craig , Pearce G. William , Rydzewski Andrzej 
Published: February 2008

Extensive mineralization occurs in southwest Poland as zoned blankets of Cu‐Ag‐(Pb‐Zn) sulphides in the Kupferschiefer and Zechstein Limestone across the base of the Late Permian Zechstein restricted marine sequence, and in the Weissliegendes sandstone at the top of the Early Permian Rotliegendes continental volcanic and siliciclastic sequence. The Rote Fäule (RF) zone, an oxidized, hematitic equivalent of the normally pyritic basal Zechstein, directly underlies the copper ore and is part of the metal zoning. Although the origin has generally been considered to be syngenetic, geologic controls of the RF‐ore systems in Poland suggest a late diagenetic origin by converting metalliferous brines migrating through the Rotliegendes clastic redbeds up along basement highs, oxidizing the pyritic Kupferschiefer to form the RF, and precipitating base and precious metals on the reduced side of this oxidation‐reduction front. A paleomagnetic study of the ore zone in five mines in Poland, the RF zone in three mines, and of the barren pyritic basal Zechstein from outcrops and quarries in Poland, Germany, and England was undertaken to determine the absolute age of the mineralization. In the barren pyritic rocks and the copper sulphide ore, thermal demagnetization and vector subtraction revealed an unstable low‐temperature first‐remanence component (76.9°N, 12.2°E; A63 = 1.6°), parallel to the ambient field, and a second, higher temperature component (82.6°N, 145.9°E; A63 = 1.9°), which could be Miocene (10–20 Ma) or, less likely, Cretaceous (110 Ma) or Jurassic (180 Ma). This second component is erased at 350°–400°C and is thought to be carried by a product of weathering after Alpine age uplift and erosion. No primary magnetization could be isolated in the copper or pyritic zones. The RF hematite, however, contained a very stable third, reversed component (49.0°N, 157.2°E; A63 = 2.2°) which was revealed typically between 500° and 620°C, and is considered to represent a secondary chemical remanent magnetization acquired during the mineralizing process. In order to date the isolated magnetic components, Carboniferous to Neogene apparent polar wander (APW) paths for Europe and Russia were constructed using paleopole catalogs. Mean paleopoles every 10 Ma from 350 to 0 Ma, with A63 circles of confidence, were calculated as running averages using overlapping 20‐ and 30‐Ma time intervals. The RF pole, corresponding to the third remanence component, coincides extremely well with a Middle Triassic age of 240 Ma on the 20‐Ma APW path and a Late Triassic age of 230 Ma on the 30‐Ma APW path. Statistical analysis yields upper and lower age limits of 250 and 220 Ma. This Triassic paleomagnetic age supports the proposed late diagenetic origin of the Kupferschiefer ore deposits, and suggests that the RF‐ore systems were formed immediately after Triassic continental rifting associated with the opening of the Tethys ocean to the south—a likely source of the thermal anomaly necessary to initiate adequate convective velocities within the Rotliegendes clastic basins.