Thermal lithosphere across the Trans-European Suture Zone in Poland

Significant lateral variations of surface heat flow occur in the Polish Lowland area, ranging up to 30+/–10 mW/m2 across the transition from the East European Craton (EEC) and the northeastern part of the Teisseyre-Tornquist Zone (TTZ) to the accreted terranes in the south-west (Palaeozoic Platform) and up to 25 mW/m2 of change within the Trans-European Suture Zone (TESZ). Modelling of the crustal temperatures for the deep seismic profiles parallel to TESZ (P1, P5 and TTZ) and perpendicular to it (LT-7, P2, LT-2, P4, LT-4 and LT-5) shows evidence of extensive crustal-mantle warming (elevated mantle heat flow in the area between the Sudetes and the EEC). The EEC and the northern part of the TTZ have a much lower mantle heat contribution. Mantle heat flow variations are significant (approximately 20–40 mW/m2). Significant are also variations in thermal lithosphere thickness ranging from ca. 150–200 km in the craton and the northern part of the TTZ to 100–150 km (locally less than 100 km) in the accreted terranes to the south-west of the TTZ and in the central part of the TTZ. The TTZ is a thermally inhomogeneous zone.The thermal transition between the Palaeozoic Platform and the EEC is not a sharp one. Significant variations in the thickness of the thermal lithosphere do not follow major tectonic units of the crust.