Differences Between Recent Heat Flow Maps of Poland and Deep Thermo-Seismic and Tectonic Age Constraints

Abstract

Poland is situated in a place of contacts between three continental scale geologic structural units: the Precambrian East European Craton (EEC) to the northeast, the Variscan West European Platform (WEP) terranes to the southwest, and the younger Carpathian Alpine arc in the south. The Trans-European suture zone (TESZ) between the EEC and WEP is a deep-seated discontinuity zone reaching down to a depth of about 200 km. The conjunction of all these continental scale geologic units is reflected in the complex tectonic structure of this area. Apart from the complex seismic structure, this area is also associated with pronounced gravity, magnetic and heat flow anomalies. Significant differences exist between heat flow maps of Poland published in recent works, with values reaching 20 to 30 mWm-2. Examples are differences in heat flow based on models that use well log interpreted mineral and porosity content and assigned world averages of rock and fluid thermal conductivities versus ones based on averaging thermal conductivity values measured using borehole cores only. These differences in heat flow between the methods are discussed in the context of their relationship with tectonic age. Also considered are depth differences between lithosphere – asthenosphere boundary (LAB) derived from thermal model vs those that obey seismological constraints. Higher heat flow estimates reaching up to or more than 100 mWm-2, based on conductivity values derived from well-logs, are found to be quite improbable. This likely reason for overestimate of heat flow is discussed.