Age and geochemistry of the mafic sills, ODP Site 1276, Newfoundland margin

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doi: 10.1016/j.chemgeo.2006.07.001
Author(s): Hart, S. R.; Blusztajn, J.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Woods Hole, MA, United States
Volume Title: Chemical Geology
Source: Chemical Geology, 235(3-4), p.222-237. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. Includes appendices. 61 refs.; illus., incl. 3 tables, sketch map
Summary: Site 1276, Leg 210 of the Ocean Drilling Program, was located on the Newfoundland margin in a seismically-defined ∼128 Ma "transitional" crust just west of the 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 1739 m hole was terminated 90-160 m 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.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 03 Geochronology; Absolute age; Alkaline earth metals; Alteration; Ar/Ar; Basalts; Canada; Chemical composition; Continental drift; Continental margin; Cretaceous; Crust; Dates; Diabase; Eastern Canada; Geochemistry; ICP mass spectra; Igneous rocks; Intrusions; Isotope ratios; Isotopes; Lead; Leg 210; Mafic composition; Magmatism; Magnetic anomalies; Mantle; Mass spectra; Mesozoic; Metals; Mid-ocean ridge basalts; Nd-144/Nd-143; Neodymium; Newfoundland; Newfoundland and Labrador; ODP Site 1276; ODP Site 1277; Ocean Drilling Program; Oceanic crust; Pb-208/Pb-204; Plate tectonics; Plutonic rocks; Radioactive isotopes; Rare earths; Rifting; Sills; Spectra; Sr-87/Sr-86; Stable isotopes; Strontium; Trace elements; Volcanic rocks; X-ray fluorescence spectra
Coordinates: N452400 N452400 W0444700 W0444700
N451200 N451200 W0442600 W0442600
Record ID: 2007064343
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands