Tectonic setting of post-orogenic granites within SW Fennoscandia based on deep seismic and gravity data

Within the Sveconorwegian Province of SW Scandinavia granite intrusions are abundant. Prominent ones are the Bohus-Iddefjord and the Fla granites, the so- called Bohus-Fla Granite belt. The age of these granites, consistent at approximate to 900 Ma, coincides with the late extensional stage of the Sveconorwegian-Grenvillian orogen. Gravity observations and deep seismic profiling Lines are presented that also cover the Skagerrak Sea. The geophysical data suggest that the Bohus granite continues seaward for at least 80 km and its thickness, offshore, is estimated to be 2-4 km. Where the seismic profiling Lines intersect the inferred seaward extension of the Bohus granite, a distinct reflection pattern is observed at approximate to 1.6 s. TWT. This coincides with a gravity modelled thickness of approximate to 4 km. The seismic profiles also show a large Moho offset beneath the modelled granite. It is proposed that this offset is related to Sveconorwegian crustal underthrusting and that the granite melt could have formed by anatexis of mid-crustal rocks downthrusted to greater depths in the vicinity of the seismically observed Moho offset.