Thermal regime of the earth's crust in the transition zone from the Baltic Shield to the Barents Sea Plate

Abstract

Introduction: The problems of studying the thermal regime of the earth's crust in the zone of transition from the Baltic shield to the Barents Sea plate are discussed. The performed analysis is based on the results of temperature measurements in the deep borehole P-1, drilled on the isthmus between the Sredny and Rybachy peninsulas, data on the natural radioactivity of the rocks exposed by it, and their thermal conductivity. Methodology: General information about the structure of the upper part of the earth's crust in the area of drilling a well is provided based on the materials of geological and seismic studies. A brief description of the complex of geophysical surveys and geological and technological tests along the P-1 well bore is provided with an emphasis on the results of field temperature measurements in the well. Laboratory measurements of the thermal conductivity of core samples from well P-1 ,which demonstrated some differences between the terrigenous rocks of the Riphean and the Archean crystalline rocks were performed. The generalized results of determination of the concentration of radiogenic elements in the core rocks of the well , showing a significant differentiation of the terrigenous rocks of the Riphean and the crystalline rocks of the Archean are presented. Results and discussion: Based on the data of complex studies, an insignificant role of the hydrogeological regime in the perturbation of the temperature field along the well was shown. The Horner’s method was used to calculate the unperturbed temperatures at the bottom-holes of the drilling intervals of the well and to estimate the geothermal gradient for deep Archean horizons of the section, where the heat flux was estimated at 32 mW/m2. For the Riphean terrigenous complex of the P-1 well section, the value of the undisturbed heat flux was estimated at 20 mW/m2, which indicates the influence of near-surface temperature during the last glaciation. The values of heat generation of rocks calculated based on the data on the content of radiogenic elements allowed to estimate the total value of the unperturbed surface heat flow in the area of well P-1 at a level of approximately 34 mW/m 2. Conclusions: The main results of the study of the totality of characteristics of the thermal regime of the earth's crust in the transition zone from the Baltic Shield to the Barents Sea Plate were formulated.