November 2001

iSIMMNERC/DTI LINK OCEAN MARGINS THEMATIC PROGRAMME

Mapping & Modelling Heterogeneous Stretching & Volcanism on the NW European Atlantic Margin

integrated Seismic Imaging and Modelling of Margins (iSIMM)

•Principal Investigators

•Prof. Nick Kusznir - Liverpool University•Prof. Bob White - Cambridge University•Dr Phil Christie - Schlumberger Cambridge Research•Dr Alan Roberts - Badley Earth Science Ltd.

•Project Partners•NERC, DTI•Agip, Amerada Hess, Anadarko, BP, Conoco, Phillips, Statoil, Western Geco & Shell

November 2001

iSIMM

Scientific Objectives

•To develop and test new quantitative models of rifted margin formation, incorporating heterogeneous stretching, the effects of melt generation and emplacement and varying thermal anomalies in the mantle.

•To test these models using state-of-the art seismic imaging using long-offset and wide-angle techniques.

•Models and imaging techniques will be applicable to both volcanic and non-volcanic rifted continental margins world-wide.

November 2001

iSIMM

Development of New Rifted Margin Model

•Existing quantitative models of rifted margin formation are not adequate

•Existing models do not quantitatively describe•heterogeneous stretching •mantle exhumation•volcanic addition

•New quantitative model of structural, volcanic, thermal and subsidence processes at rifted margins needed.

•Two-phase flow models of mantle flow and melt transport, successfully applied to ocean ridges.

•Two-phase flow models will be used to model the initiation of sea-floor spreading and the formation of rifted margins.

November 2001

iSIMM

Development of New Rifted Margin Model

Volcanic continental margins (e.g.NW European margin) need new modelling strategies

Improved quantitative models need to take account of •heterogeneous stretching•mantle exhumation •melt generation•non-conservation of mass by volcanic addition•dynamic uplift from mantle plumes

Required for the prediction of •subsidence•temperature •maturation history•interpretation validation

November 2001

iSIMM

Modelling Rifted Margins We believe that the formation of outer parts of rifted margins owes more to sea-floor spreading initiation than to intra-continental rifting processes

Two-phase flow models of mantle flow and melt transport•Successfully applied to ocean ridges •Adapt to rifted margin formation•Use to model initiation of sea-floor spreading

(Perfit 1999)

November 2001

iSIMM

Testing of New Rifted Margin Model•New model will be tested

•at non-volcanic margins using existing observations of heterogeneous stretching•on NW European Atlantic volcanic margins using new observations from this study

•Maps of heterogeneous stretching, subsidence and volcanic addition for the NW European volcanic margin will be used to

•test the new model of rift margin formation, •determine the timing of depth-dependent stretching with respect to the initiation of sea-floor spreading

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November 2001

iSIMM

Why NW European Atlantic Margin ?

•An excellent natural laboratory to observe rifted margin properties and to test theoretical models.

•Best-known volcanic margin world-wide, with a wealth of regional surveys and oil company data available to embed research.

•Crustal seismic and ODP drilling data available on the conjugate margins of East Greenland.

•Considerable amount of work already exists on the Iceland mantle plume.

November 2001

iSIMM

Faeroes Seismic Survey•Field acquisition of a 330km-long wide-angle seismic profile extending north-south from the Faroes-Shetland Trough, crossing the Faroes shelf and across the northern transform margin into the Vøring Basin. •Will use

•cutting-edge, 12km, Q-streamer system from Schlumberger Geco-Prakla, comprising high-density sampling of each individual sensor for optimal grouping, •together with 100 closely-spaced ocean bottom seismometers (OBS), to provide a detailed crustal image from the sediments, through the basalt flows and into the possibly intruded or underplated lower crust.

November 2001

iSIMM

Wide-angle Sub-basalt Imaging – FLARE(from Fliedner & White, First Break, May 2001, p 247-252)

November 2001

iSIMM

November 2001

iSIMM

November 2001

iSIMM

Hatton-Rockall Seismic Survey•Field acquisition using a grid of 100 OBS and conventional seismic reflection profiles•Mapping the transition from continental crust to fully oceanic crust across the Hatton-Rockall Basin and rifted continental margin. •Profile will extend well out onto the oceanic crust to map crustal thickness variations associated with gravity lineations thought to represent pulsing of the mantle plume.•Acquisition lies in a region of rapid change in the impact of the Iceland mantle plume at the time of breakup.

November 2001

iSIMM

Deliverables - Scientific & Technical

•Development of a new quantitative model of structural, volcanic, thermal and subsidence processes at rifted margins. •Rifted margin modelling software incorporating structural, volcanic, thermal and stratigraphic processes.•Development of new sub-basalt and lower crustal imaging strategies including incorporation of wide-angle 3-component data and possible converted S-wave imaging. •Crustal structure (incl. sediment and volcanic thickness) for Faroe-Shetland and Hatton-Rockall Basins.•Profiles for UK and adjacent Atlantic margins of stretching histories, bathymetry and subsidence evolution, and top basement heatflow with time.•Temperature and maturation history at selected locations.•Generic models for structural, stratigraphic and volcanic components of rifted margin formation.