Thermal lithosphere across the Trans-European Suture Zone in Poland

Abstract

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.