Lower crustal bodies in the Møre volcanic rifted margin: Geophysical determination and geological implications
Résumé
Understanding nature, structure and age of Lower Crustal Bodies (LCBs) and their relation to the crustal structure of the Møre margin (Mid-Norwegian margin), and in a more general way, of magma-rich rifted margins, is a key issue to decipher the tectono-magmatic processes found in volcanic rifted margins. In light of 2D potential field modelling combined with reflection and refraction seismic data, we reinvestigated the crustal nature of the Møre margin and adjacent Jan Mayen corridor. In the proximal domain, our study shows that the LCBs most likely rep-resent inherited crustal bodies and not necessarily rift-related serpentinised mantle as previously proposed. To fit all geophysical observations, both lower and middle crustal layers need to be preserved over a large part of the Møre Basin. For the distal margin, the interpretation of the LCBs is more difficult. Our preferred interpretation is that they are mainly made of boudins of hyper-extended, pre-rift lower continental crustal rocks more or less intruded by Early Tertiary magmatic material. Our seismic, magnetic and gravity data does not easily support large scale exhumation of serpentinised mantle in the inner and is unlikely in the outer parts of the Møre Basin. The deep structures of the Mid-Norwegian magma rich rifted margin result from the poly-phase stretching and thinning of complex inherited crustal structures, locally intruded by Early Tertiary magmatic material.