The mid-Norwegian margin: a discussion of crustal lineaments, mafic intrusions, and remnants of the Caledonian root by 3D density modelling and structural interpretation

Abstract

The high-density lower crustal body (LCB) on the mid-Norwegian margin is almost universally interpreted to represent magmatically underplated material, added to the crust during Early Tertiary opening of the NE Atlantic. The thickness of the LCB is uneven, and its distribution along the margin is sharply limited by margin-perpendicular lineaments. Three-dimensional density modelling constrained by petrophysical and seismic data was performed to investigate the expression of the various lineaments (Bivrost, Jan Mayen, Gleipne, etc.) in the crustal architecture, with and without the LCB. The Bivrost Lineament, separating the Vøring and Lofoten margin segments, is clearly expressed and so is arguably a lineament in the SW Vøring margin. Notably, most of the lineaments can be interpreted as offshore prolongations of major onshore detachments stemming from Late Caledonian orogenic collapse. An alternative interpretation of the LCB is thus that it represents high-grade metamorphic rocks, remnant from the Caledonian root. Determining the nature of the LCB has profound effects for the volume estimate of magmatic rocks in the North Atlantic Igneous Province, and consequently also for the degree of crustal thinning and heat flow.

Extension, hyperextension and mantle exhumation offshore Norway: a discussion based on 6 crustal transects

“…More recently acquired refraction data (Breivik et al, 2011;Kvarven et al, 2014) and potential field-based crustal models provide additional constraints (e.g., Ebbing et al, 2006;Ebbing & Olesen, 2010). Recent works on hyperextended margins elsewhere have presented a number of concepts that should be considered when discussing the Norwegian margin (e.g., Blaich et al, 1997;Osmundsen & Ebbing, 2008;Péron-Pinvidic et al, 2013).…”

“…To constrain the crustal thickness along the seismic reflection profiles used in this study, we have used existing 3D geophysical models of the Mid-Norwegian margin as a basis (e.g., Ebbing et al, 2006Ebbing et al, , 2009Reynisson et al, 2011Kvarven et al, 2014. We have employed the gravity and magnetic data described above and the IGMAS, which calculates the potential field effect of a crustal model by triangulation between modelling planes (Götze & Lahmeyer, 1988), to expand and refine the 3D models used in previous works (see Ebbing et al, 2006;Osmundsen & Ebbing, 2008;Reynisson et al, 2011 for details). The most important parameters in the construction of the 3D model are the crustal geometry and petrophysical properties (density, magnetic susceptibility and Q-ratio) for the crust and upper mantle.…”

“…The deep structure of the Møre margin has been updated using the results of three modelled OBS profiles by Kvarven et al (2014). For a more detailed discussion on velocity, density and magnetic parameters, see Ebbing et al (2006Ebbing et al ( , 2009 and Kvarven et al (2014). The modelled parameters for the different stratigraphic units and crystalline crustal types (Table 2) were based on data obtained from basement 2011; Franke, 2012;Péron-Pinvidic et al, 2013;Savva et al, 2014;Stica et al, 2014;Tugend et al, 2014).…”

Potential mechanisms for the genesis of Cenozoic domal structures on the NE Atlantic margin: pros, cons and some new ideas

“…These are plotted in Figure 10, the values broadly derived from the work of Ebbing et al (2006). From the depth to basement map we generated a total sediment thickness map.…”

Controls on the location of compressional deformation on the NW European margin

“…In the central segment of the Vøring margin, HVLC with a thickness of up to 8 km has been mapped by many seismic refraction and reflection experiments, and additionally constrained using gravity data and isostatic modelling (e.g. Gernigon et al 2003Gernigon et al , 2004Ebbing et al 2006;Mjelde et al 2009a;Reynisson et al 2010). HVLC has also been detected on the Møre margin, south of the Jan Mayen Lineament, and in that area an additional zone has been detected in the east, close to the shelf edge (Kvarven et al 2014).…”