Thermal and rheological structures along the seismic POLAR profile in the northern Fennoscandian Shield

Terra Nova, 25, 2–12, 2013 Abstract Extensive study is carried out to resolve the detailed lithospheric thermal and rheological structures of the seismic profile POLAR in the northern Fennoscandian Shield. The constructed 2-D models are based on the latest seismic velocity models, material parameters and measured heat flow (HF) values. Thermal results indicate the mantle HF to be low (13–15 mWm−2) and the thermal lithosphere-asthenosphere boundary to be at a depth of 190–225 km. Rheologically southwest (SW) and northeast (NE) parts of the profile differ significantly, e.g. the depth of the brittle-ductile transition varies from 24–38 km in the SW to 12–18 km in the NE. The estimated values of the effective elastic thickness of the lithosphere show large variation between the depths of 63 and 132 km.