Age and geochemistry of the mafic sills, ODP site 1276, Newfoundland margin
Hart, Stanley R.
Blusztajn, Jerzy S.
MetadataShow full item record
Site 1276, Leg 210 of the Ocean Drilling Program, was located on the Newfoundland margin in seismically-defined ~128 Ma “transitional” crust just west of presumed oceanic crust, and the M3 magnetic anomaly. The goal of drilling on this non-volcanic margin was to study the rifting, nature of basement, and post-rift sedimentation in the Newfoundland-Iberia rift. Drilling of this 1739m hole was terminated 90-160 meters above basement, in the lower of a doublet of alkaline diabase sills. We have carried out geochemical studies of the sill complex, in the hopes that they will provide proxy information regarding the nature of the underlying basement. Excellent 40Ar/39Ar plateau ages were obtained for the two sills: upper sill ~105.3 Ma; lower sill ~97.8 Ma. Thus the sills are substantially younger than the presumed age of the seafloor at site 1276 (~128 Ma), and were intruded beneath substantial sediment overburden (250 m for the upper, older sill, and 575 m for the lower younger sill). While some of the geochemistry of the sills has been compromised by alteration, the “immobile” trace elements show these sills to be hawaiites, differentiated from an enriched alkaline or basanitic parentage. Sr, Nd and Pb isotopes are suggestive of an enriched hotspot/plume mantle source, with a possible “added” component of continental material. These sills unequivocally were not derived from typical MORB (asthenospheric) upper mantle.
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Chemical Geology 235 (2006): 222-237, doi:10.1016/j.chemgeo.2006.07.001.
Showing items related by title, author, creator and subject.
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 Peron-Pinvidic, Gwenn; Shillington, Donna J.; Tucholke, Brian E. (John Wiley & Sons, 2010-05-25)Drilling during ODP Leg 210 penetrated two post-rift sills (dated as ∼105.3 and ∼97.8 Ma) in the deep sediments overlying basement of the continent–ocean transition zone on the magma-poor Newfoundland margin. The sill ...
Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – II. Results from a seismic reflection profile Lau, K. W. Helen; Louden, Keith E.; Deemer, Sharon; Hall, Jeremy; Hopper, John R.; Tucholke, Brian E.; Holbrook, W. Steven; Larsen, Hans Christian (2006-03-03)New multi-channel seismic (MCS) reflection data were collected over a 565km transect covering the non-volcanic rifted margin of the central eastern Grand Banks and the Newfoundland Basin in the northwestern Atlantic. Three ...
Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – I. Results from a seismic refraction profile Lau, K. W. Helen; Louden, Keith E.; Funck, Thomas; Tucholke, Brian E.; Holbrook, W. Steven; Hopper, John R.; Larsen, Hans Christian (2006-03-03)A P-wave velocity model along a 565-km-long profile across the Grand Banks/Newfoundland basin rifted margin is presented. Continental crust ~36-kmthick beneath the Grand Banks is divided into upper (5.8-6.25 km/s), middle ...