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Lithosphere extension in 3-D (oblique rifting, rift propagation)

Lithosphere extension in 3-D (oblique rifting, rift propagation). Jolante van Wijk & Donna Blackman SIO. Lithosphere extension: 2-D or 3-D. Jan Mayen Fracture Zone. Outline. * 3-D cases and tectonic processes involved -oblique rifting -rift propagation

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Lithosphere extension in 3-D (oblique rifting, rift propagation)

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  1. Lithosphere extension in 3-D(oblique rifting, rift propagation) Jolante van Wijk & Donna Blackman SIO

  2. Lithosphere extension: 2-D or 3-D Jan Mayen Fracture Zone

  3. Outline * 3-D cases and tectonic processes involved -oblique rifting -rift propagation -mantle flow beneath rifts * Prior modeling approaches -numerical -analogue * Our approach: Tekton & FELIB * Other options

  4. Lithosphere extension: 3-D processes Rift propagation Woodlark Basin

  5. Lithosphere extension: 3-D processes Rift propagation Gulf of Aden

  6. Lithosphere extension: 3-D processes Pre-structured lithosphere, oblique rifting NAGF North American craton West African craton Caledonian- Hercynian belts

  7. Lithosphere extension: 3-D processes EARS follows pre-structured lithosphere Extension of continental lithosphere Mechanical stretching Magmatic extension Ebinger, 2005

  8. Lithosphere extension: 3-D processes Rift branches Proterozoic mobile belts Africa Madagascar

  9. Lithosphere extension: 2-D processes Decompressional melting during extension Extension of continental lithosphere Mechanical stretching Magmatic extension Ebinger, 2005

  10. Lithosphere extension: 3-D processes Tectonic processes involved Setup geometry lateral variations in lithosphere architecture, different geological provinces Boundary conditions laterally varying boundary conditions, oblique extension Basics needs: Thermo-mechanical model? Layered lithosphere?

  11. Existing numerical models Elastic Plate Model: Hubert-Ferrari et al., 2003 Rift propagation (=crack propagation) Assumption: lithosphere is an elastic plate in which viscous/ductile behavior plays no (important) role

  12. Existing numerical models Finite Element Models: Dunbar and Sawyer, 1996 Rift propagation - Symmetrical model - Equations: creeping flow, heat flow

  13. Existing numerical models Boundary Element Models: Katzman, ten Brink & Lin, 1995 Pull-apart basin formation

  14. Analogue modeling studies Sand & silicone experiments + fault structures - thermal effects, rheology (Tron and Brun, 1991)

  15. Analogue modeling studies of oblique rifting Centrifuge model + fault structures - thermal effects, rheology More analogue results (Giacomo Corti, 2004)

  16. Our modeling approach Thermo-mechanical model Finite element model, Lagrangian approach Mechanical part: based on Tekton Thermal part: based on FELIB

  17. Numerical modeling of oblique rifting Mechanical part Thermal part Visco-elastic deformation, Heat flow equation correction for plastic/brittle Heat production in crust behavior Buoyancy forces T-dependent power- law rheology

  18. Numerical modeling of oblique rifting Model setup

  19. Oblique rifting Results: Map view of model domain, crustal thinning Normal rifting Oblique rifting Oblique rifting

  20. Oblique rifting Results: Surface heat flow for oblique rifting test

  21. * Rift zones follow the weak trend as a group, but are individually oriented according to extension direction * Asymmetric development of individual rifts

  22. * Rift zones follow the weak trend as a group, but are individually oriented according to extension direction * Asymmetric development of individual rifts

  23. *Asymmetric development of individual rifts *Alternating asymmetric rifts, linked through accommodation zones

  24. Example of alternating rift asymmetry can be found in the Malawi Rift Lake Malawi topography Ebinger et al., 1987

  25. Mantle flow beneath rift basin Rift parallel Rift perpendicular

  26. Rift propagation modeling Model setup

  27. Rift propagation: end-member modes Evolution of crustal thinning, map view of model domain Strong plate Inter- mediate Weak plate

  28. Rift propagation: end-member modes Rift-parallel component of velocity field, map view Stalled rift Continuous propagation

  29. Rift propagation: end-member modes Horizontal shear stress, map view Stalled rift Continuous propagation

  30. * Flexibility of geometry, initial setup and boundary conditions * Application to deformation of oceanic lithosphere * Modeling of large scale structures What works fine * Modeling of smaller scale structures * Grid spacing, calculation time * Remeshing, large deformation * Brittle/ductile behavior Improvements needed

  31. Other options SNAC? Commercial codes such as ANSYS ABAQUS ….. FLAC

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