Wieloznaczność tektonicznej interpretacji rozkładu pola geotermicznego na obszarach platformowych Polski

Abstract

ON AMBIGUITIES IN INTERPRETATION OF GEOTHERMAL FIELD DISTRIBUTION Summary The paper deals with ambiguities in tectonic interpretation of geothermal field parameters in Poland. Zones differing in geothermal regime do not always match well tectonic units established with reference to the age of basement consolidation. The highest values of grad T and heat flow Q are generally recorded in area of Variscan externides and their foreland, west of the Teisseyre-Tornquist Line. However, the Line, regarded as western boundary of the Old East-European Platform, fails to appear as a sharp one in the case of distribution of geothermal parameters. Low Q and grad T values, comparable with typical of Polish part of the Old Platform, are also recorded in Pomerania west of the Koszalin - Chojnice zone, i.e. in area considered as consolidated in the Bailkalian epoch by some authors (20) and in the Caledonian by others (27). The values are also low west of that line in south-western Poland, including the external zone of the Carpathian orogen. In western Poland, a positive anomaly of heat flow and grad T has been found in area characterized by anomalous structure of the Barth crust in zone transitional to the Upper Mantle (according to DSS data - see (9)) and volcanic activity in the Autunian and at the same time, the lack of positive anomalies of ΔZ vertical component of the magnetic field (6). The anomaly may be related to an increased radiogenic heat generation in deep-seated crystalline basement and substantial amounts of remnant heat related to very deep-seated sources active in the Late Variscan epoch. There are presented the results of studies on radiogenic heat in Precambrian basement in north-eastern Poland, characterized by very low values. The studies showed that heat flow in sedimentary cover is significantly lower than in the crystalline basement in north-eastern Poland. This is especially the case of zones of groundwater recharge in northern part of the Mazury - Suwałki Elevation.