Characterization of sills associated with the U reflection on the Newfoundland margin: evidence for widespread early post-rift magmatism on a magma-poor rifted margin

Details Characterization of sills associated with the U reflection on the Newfoundland margin: evidence for widespread early post-rift magmatism on a magma-poor rifted margin Characterization of sills associated with the U reflection on the Newfoundland margin: evidence for widespread early post-rift magmatism on a magma-poor rifted margin

Jul 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010geoji.182..113p&link_type=abstract

Geophysical Journal International, Volume 182, Issue 1, pp. 113-136.

Astronomy and Astrophysics

Astronomy

1

Ocean Drilling, Continental Margins: Divergent, Hotspots, Atlantic Ocean

Scientific paper

Drilling during ODP Leg 210 penetrated two post-rift sills (dated as ~105.3 and ~97.8Ma) in the deep sediments overlying basement of the continent-ocean transition zone on the magma-poor Newfoundland margin. The sill emplacement post-dated the onset of seafloor spreading by at least 7-15Myr. The shallower of the two sills coincides with the high-amplitude U reflection observed throughout the deep Newfoundland Basin, and strong reflectivity in the sub-U sequence suggests that a number of other sills are present there. In this paper, we use multichannel seismic reflection data and synthetic seismograms to investigate the nature, magnitude and extent of this post-rift magmatism in the deep basin. Features observed in seismic profiles that we attribute to sill injection include high-amplitude reflections with geometries characteristic of intrusions such as step-like aspect; abrupt endings, disruptions and junctions of reflections; finger-like forms; differential compaction around possible loci of magma injection and disruption of overlying sediments by apparent fluid venting. Interpreted sills occur only over transitional basement that probably consists of a mixture of serpentinized peridotite and highly thinned continental crust, and they cover an area of ~80 000km2. From analysis of synthetic seismograms, we estimate that sill intrusions may comprise ~26 per cent of the sub-U high-reflectivity sequence, which yields a crude estimate of ~5800km3 for the total volume of sills emplaced by post-rift magmatism. This is significant for a margin usually described as `non-volcanic'. We discuss competing hypotheses about the source of the magmatism, which is still uncertain.

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