A heat generation model for continental crust based on deep drilling in the Baltic Shield

Abstract

This paper presents a heat generation model for the old continental crust on the basis of a new petrological model on the origin, evolution and deep structure of the crust in which petrological, geochemical and geophysical data obtained from the Kola superdeep borehole and other deep boreholes drilled into the crystalline basement of the East European Platform are taken into account. The petrological section obtained from the borehole observations was extrapolated down to the Moho boundary taking into consideration the evolution and generalized seismic model of the continental crust. In our model the continental crust is subdivided into three layers: a granite-gneiss layer (0–17 km), a charnokite-enderbite layer (17–30 km) and a basic layer including autochthonous restites of the protocrust (30–40 km). The boundaries between the layers correspond to seismic surfaces K 1 and K 2. The crustal contribution to heat flow is estimated to be about 25 mW/m 2 (52% of the total heat flow) for the Baltic Shield and the mantle heat flow is 22–24 mW/m 2. A comparison is made between the heat generation model obtained in this study and the ones estimated from seismic velocity structure. The difference in the heat generation value between these models may originate from the differing geological and tectonic history of the sampling localities.