The Early Eocene continental breakup was magma-rich and formed part of the North Atlantic Igneous Province. Extrusive and intrusive magmatism was abundant on the continental side, and a thick oceanic crust was produced up to a few m.y. after breakup. However, the extensive magmatism at the Vøring Plateau off mid-Norway died down rapidly northeastwards towards the Lofoten/Vesterålen Margin. In 2003 an Ocean Bottom Seismometer profile was collected from mainland Norway, across Lofoten, and into the deep ocean. Forward/inverse velocity modeling by raytracing reveals a continental margin transitional between magma-rich and magma-poor rifting. For the first time a distinct lower-crustal body typical for volcanic margins has been identified at this outer margin segment, up to 3.5 km thick and ∼50 km wide. On the other hand, expected extrusive magmatism could not be clearly identified here. Strong reflections earlier interpreted as the top of extensive lavas may at least partly represent high-velocity sediments derived from the shelf, and/or fault surfaces. Early post-breakup oceanic crust is moderately thickened (∼8 km), but is reduced to 6 km after 1 m.y. The adjacent continental crystalline crust is extended down to a minimum of 4.5 km thickness. Early plate spreading rates derived from the Norway Basin and the northern Vøring Plateau were used to calculate synthetic magnetic seafloor anomalies, and compared to our ship magnetic profile. It appears that continental breakup took place at ∼53.1 Ma, ∼1 m.y. later than on the Vøring Plateau, consistent with late strong crustal extension. The low interaction between extension and magmatism indicates that mantle plume material was not present at the Lofoten Margin during initial rifting, and that the observed excess magmatism was created by late lateral transport from a nearby pool of plume material into the lithospheric rift zone at breakup time.

Item Type:	Refereed Article
Keywords:	plume, dynamic topography, magmatism, plate tectonics, ocean bottom seismometers, large igneous provinces, marine magnetics, continental breakup
Research Division:	Earth Sciences
Research Group:	Geology
Research Field:	Structural geology and tectonics
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the earth sciences
UTAS Author:	Breivik, AJ (Associate Professor Asbjoern Breivik)
ID Code:	122307
Year Published:	2017
Web of Science® Times Cited:	14
Deposited By:	Oceans and Cryosphere
Deposited On:	2017-11-09
Last Modified:	2018-05-25
Downloads:	0