--> Abstract: Magmatism and Break-up on the NE Atlantic: The Nature and Influence of the Lower Crustal Body on Margin Structure, by Mohamed Mansour Abdelmalak; #90177 (2013)

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Magmatism and Break-up on the NE Atlantic: The Nature and Influence of the Lower Crustal Body on Margin Structure

Mohamed Mansour Abdelmalak

The NE Atlantic Volcanic rifted margins are characterized by massive occurrences of mafic extrusive and intrusive rocks formed during continental breakup between NO and Greenland. Commonly observed along the margin, high P-wave velocity bodies (Vp> 7km/s) (Lower Crustal Bodies: LCB) are interpreted by many authors as breakup-related mafic underplating or/a highly intruded lower crust. On the Vøring margin a strong amplitude reflection (the so called T-Reflection) has been identified and interpreted as the top LCB. Located in the outer part of the margin, the T-Reflection represents a prominent and semi-regional, dome-shape feature and characterized by: (1) high impedance boundary associated with a high Vp velocity body, (2) a clearly related positive Bouguer anomaly but (3) a low magnetic signal. The nature of the T-Reflection and the LCB is still an ongoing debate. Previously interpreted as magma underplating, some authors have alternatively suggested that LCB in the continental part of the margin may relate to inherited high grade metamorphic rocks, possibly mixed with intrusion or partially serpentinised mantle. Such interpretation is particularly supported by the fact that the lower crustal dome controls the outer Vøring Basin structure and sedimentation long before the onset of breakup magmatism. Some authors have suggested also that the LCB may represent partially serpentinized mantle related to Early Cretaceous hyperextension. In this study we have attempted to refine the regional mapping of the top LCB and T-Reflection in the Norwegian margin. For this issue we have used all available deep seismic reflection and refraction data in addition to magnetic and gravimetric data. Such mapping allowed us to determine with more confidence the geometry and nature of the T-Reflection and if it defines, everywhere, the LCB top. We extended this study to the NE Greenland conjugate margin and the SW Barents Sea margin where similar dome shape and high amplitude reflections with high gravity/ Low magnetic anomalies have been identified. We discuss the LCB nature in the NE Atlantic area and its influence on continental breakup and formation of the rifted margin.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013