### Związki elementów pola cieplnego z wiekiem konsolidacji obszaru Polski

#### Abstract

RELATIONS BETWEEN HEAT FIELD AND CONSOLIDATION AGE OF THE BASEMENT IN THE AREA OF POLAND

Summary

Two problems are discussed in the present paper. The first problem concerns the more precise reconnaissance of the temperature field of the upper part of the Earth's crust within the area of Poland. On the basis of 54 temperature measurements the values of both gradient and geothermal degree at a depth intelrval 0,5-1,5 km have been calculated (Table 1). Moreover, the values of temperature are given as to the following depths: 500 m, 1000 m, and 1500 m, examined in bore holes made by the Geological Institute. The calculated weighted averages of geothermal degree were a basis to construct the map of geothermal degree contour lines (Fig. 1).

The general changes in geothermal degree can be considered in terms of the influence of conductivity and the correlation with tectonic development. According to the author, the second factor is here of considerable importance. A distinct contrast can be .observed in values q and G between the Mazury-Suwałki and Sławatycze elevations, and the area comprised by the Variscan consolidation of the basement. A divergence of opinions as to the problem of the western boundary of the Precambrian East-European platform, the course of the Caledonides, and the boundary of the front of the Variscan consolidation in some areas cannot be the basis for the correlation of geothermal parameters with the age of consolidation surface in the individual regions.A decrease in the value of geothermal degree in the continuation of the Brześć deep, i.e. within the Podlasie depression, ascertained due to calculations, is characteristic of the Precambrian platform area of East Europe. This fact can be related to a deep tectonic fracture. It is proved by the data obtained from the territory of the Soviet Union.

The second problem concerns the relations between the elements of heat field and the consolidation age of the basement. To obtain objective data concerning the relation of the geothermal gradient with the areas of the Precambrian and Palaeozoic orogenies a statistical analysis has been made. The analysis of the values for Eurasia has proved the relations between the gradient and the age of the orogenies.

To some extent, this fact explains the changes in gradient observed to appear in a SW-NE direction within the area of Poland. At the same time, the influence of tectonic processes upon the geothermal parameters becomes more and more visible.

Both the obtained displacement of distributions and the difference of average values of gradients (Fig. 3) allowed the author to draw conclusion as to the geothermal activity in both areas. Simulatenously, the ascertained differentiation in the value of gradient was a basis to analyse the geothetrmal activity of the Earth's crust and upper mantle within the areas of the Precambrian and Palaeozoic orogenies. Values of probability of relations between the geothermal gradient and the areas of Precambrian orogeny have been obtained a posteriori. This fact can be a contributory information in the reconnaissance of the basement consolidation, obtained from geothermal data. Fig. 1 shows the present state of knowledge of the heat flow in the area of Poland.