NERC/DTI LINK OCEAN MARGINS THEMATIC PROGRAMME

1. NERC/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

2. 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.

3. 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.

4. 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

5. 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)

6. 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 • ·

7. 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.

8. 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.

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

12. 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.

13. 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.