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We present a 3D potential field model covering the offshore extension of the Norwegian Caledonides in the southwestern Barents Sea; it is built within the IGMAS software.
The model is made of vertical cross-sections of integrated 2D models. The 3D geometry is obtained by inter-profile triangulation of the 2D geometries. Well data and main seismic horizons are used to model the sedimentary succession. Seismic refraction and reflection are used as constrains for the definition of top basement and deep crustal structures. The distribution of density, magnetic susceptibility and Q-ratio values allows distinguishing three different basement units (Precambrian gneiss, Caledonian Nappes and mafic intrusions).
The modelling allows estimating the thickness of Caledonian nappes resting over the Precambrian shield. An important thickening of the Caledonian nappes is observed at the east of the Loppa High. Localised mafic intrusions are also mapped northeast of the Loppa High and intruding into the Norsel High. In addition, high-density (3100 kg/m3) lower crustal bodies are modelled and constrained by reflectivity data. One exhibits a peculiar 2D bulge and lies along the western side of the Loppa High and it is interpreted as a core complex. The other high-density bodies could be related to occurrence of lower crustal intrusions. At the vicinity of the margin the magnetic and gravity signal are complex. We suggest that a none-magnetic block belongs to the segmented margin. Here, lack of good seismic imaging prevents a full understanding of the crustal architecture and an advanced geological interpretation. Another basement domain extents over the Vestbakken Volcanic Province; this unit is made of intruded basement and overlain by volcanics.
The 3D geophysical model characterise the crust and deep crust. It further contributes to our understand of the basement lithology distribution and the geodynamics processes that have affected the region. It helps to address issues like the persistence of the Loppa High as a basement high since Devonian times. This 3D model is also devoted to constrain thermal modelling focussing on heat flow estimation at the top basement. The resulting crustal temperature and heat flow fields take into account parameters of heat conductivity and heat production adjusted for each lithology.
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