The composition and structure of volcanic rifted continental margins in the North Atlantic: Further insight from shear waves

Imaging challenges caused by highly attenuative flood basalt sequences have resulted in the understanding of volcanic rifted continental margins lagging behind that of non-volcanic rifted and convergent margins. Massive volcanism occurred during break-up at 70% of the passive margins bordering the A...

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Bibliographic Details
Published in:Tectonophysics
Main Authors: Eccles, JD, White, RS, Christie, PAF
Format: Article in Journal/Newspaper
Language:English
Published: ELSEVIER SCIENCE BV 2011
Subjects:
Science & Technology
Physical Sciences
Geochemistry & Geophysics
Volcanic rifted continental margin
North Atlantic Igneous Province
Ocean Bottom Seismometers
Seismic tomography
LARGE IGNEOUS PROVINCES
OCEANIC CRUSTAL THICKNESS
SPREAD SEISMIC PROFILES
FAEROE-SHETLAND BASIN
FAROE-ISLANDS
BASALT FLOWS
NE ATLANTIC
FLOOD BASALTS
ROCKS
MANTLE
Faroe Islands
Faroes
North Atlantic
Online Access:http://hdl.handle.net/2292/19108
https://doi.org/10.1016/j.tecto.2010.02.001
Description
Summary:Imaging challenges caused by highly attenuative flood basalt sequences have resulted in the understanding of volcanic rifted continental margins lagging behind that of non-volcanic rifted and convergent margins. Massive volcanism occurred during break-up at 70% of the passive margins bordering the Atlantic Ocean, the causes and dynamics of which are still debated. This paper shows results from traveltime tomography of compressional and converted shear wave arrivals recorded on 170 four-component ocean bottom seismometers along two North Atlantic continental margin profiles. This traveltime tomography was performed using two different approaches. The first, a flexible layer-based parameterisation, enables the quality control of traveltime picks and investigation of the crustal structure. The second, with a regularised grid-based parameterisation, requires correction of converted shear wave traveltimes to effective symmetric raypaths and allows exploration of the model space via Monte Carlo analyses.The velocity models indicate high lower-crustal velocities and sharp transitions in both velocity and Vp/Vs ratios across the continent-ocean transition. The velocities are consistent with established mixing trends between felsic continental crust and high magnesium mafic rock on both margins. Interpretation of the high quality seismic reflection profile on the Faroes margin confirms that this mixing is through crustal intrusion. Converted shear wave data also provide constraints on the sub-basalt lithology on the Farces margin, which is interpreted as a pre-break-up Mesozoic to Paleocene sedimentary system intruded by sills. (C) 2010 Elsevier B.V. All rights reserved.

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