Correlation of Curie point depths, heat flow data and geothermal modeling for Bulgarian territory

The basal depth of the magnetic layer (Curie point depths) of Bulgarian territory was calculated using interpretation of geomagnetic field observation and a map of the variations of this border was produced for the first time. The magnetic layer bottom thus obtained has “normal” (28-32km) values in the Moesian platform and central part of Bulgaria which are the relatively stable part of Bulgaria. Several second order anomalous regions are delineated. They have small amplitude (2-4km) and in the main correspond to areas with recognized geothermal anomalies. In the southern part, calculated depths gradually reach the minimal values of the derived Curie isotherm (up to 14-16km) with relatively high gradient. Heat flow anomalous regions are placed mostly above the CPD gradient zones rather than CPD minimums which could be explained with the complicated neotectonic structure of that region. According to the results from geothermal modeling and Paleomagnetic investigations, magnetic layer’s bottom of the Bulgarian territory corresponds to different Curie temperatures. They vary from about 300oC around Kazanluk, 425oC around Dospat up to 550-600oC in the Moesian platform, West and east Balkan unit.