HR: 16:00h
AN: V34B-01    [Abstracts]
TI: Mantle Plume Temperature Variations Immediately Following Continental Breakup of the Northern North Atlantic
AU: * Parkin, C J
EM: parkin@esc.cam.ac.uk
AF: Bullard Laboratories, Cambridge University, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: White, R S
EM: rwhite@esc.cam.ac.uk
AF: Bullard Laboratories, Cambridge University, Madingley Road, Cambridge, CB3 0EZ United Kingdom
AU: Kusznir, N
EM: sr11@liverpool.ac.uk
AF: Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, L69 3BX United Kingdom
AB: The amount of melt generated by mantle decompression beneath an oceanic spreading centre and hence the oceanic crustal thickness is controlled in part by the temperature of the mantle. By measuring the thickness of the oceanic crust formed immediately after breakup of the northern North Atlantic we are able to deduce the maximum elevated mantle temperatures caused by the presence of the Iceland Mantle Plume. Crustal thickness variations are caused by temporal variations in the mantle plume temperature: at the present Reykjanes Ridge spreading centre the plume temperature pulses on a 3-5 Myr timescale with temperature variations of c.30K. We show results from the oceanic end of the Hatton-Rockall iSIMM (integrated Seismic Imaging and Modelling of Margins) project, where for this study, 45 OBS (Ocean Bottom Seismometers) were deployed across the oceanic crust of the Iceland Basin adjacent to the rifted margin. The OBS were deployed perpendicular to the margin extending 200km oceanwards from the continent-ocean boundary at Hatton bank and along a 90km strike line on the oceanic crust. OBS spacing was 10km across the oceanic crust with a denser spacing of 4km adjacent to the margin. The profile spans magnetic anomalies 18-24 (39-56 Ma) with the strike line parallel and coincident with magnetic anomaly 20 (44Ma). The seismic source was a 101.4 Ltr (6340 cu inch), low frequency, broadband airgun source designed to optimise seismic penetration at large offsets. Magnetics, bathymetry and gravity data were acquired as well as seismic reflection data using a 3km multichannel streamer (MCS). Processing of MCS reflection data has allowed accurate determination of the sediment velocity structure covering the igneous oceanic layers. Incorporation of sediment structure into a joint reflection and refraction tomographic inversion of the wide-angle OBS data has enabled us to map crustal thickness across the oceanic crust. Results span the first 17Myr of formation of the northern North Atlantic from breakup to mature seafloor spreading. With no apparent decrease in spreading rate thinning of the crust oceanwards suggests a temperature decrease of 70K from immediate post rift formation to normal oceanic crustal thickness 17Myr after breakup. Mantle plume temperature variations during this period would cause rapid changes in uplift of the north-west European margin and probably controls much of the Tertiary sedimentation patterns west of Britain.
UR: http://www.badleys.co.uk/isimm-public/
DE: 9325 Atlantic Ocean
DE: 9604 Cenozoic
DE: 7220 Oceanic crust
DE: 3025 Marine seismics (0935)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting