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

Jolante van WijkJolante van Wijk

&&

Donna BlackmanDonna Blackman

SIOSIO

Lithosphere extension: 2-D or 3-DLithosphere extension: 2-D or 3-D

Jan Mayen Fracture ZoneJan Mayen Fracture Zone

OutlineOutline

* 3-D cases and tectonic processes involved* 3-D cases and tectonic processes involved-oblique rifting-oblique rifting-rift propagation-rift propagation-mantle flow beneath -mantle flow beneath rifts rifts

* Prior modeling approaches* Prior modeling approaches -numerical-numerical-analogue-analogue

* Our approach: Tekton & FELIB* Our approach: Tekton & FELIB

* Other options* Other options

Woodlark BasinWoodlark Basin

Rift propagationRift propagation

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

Gulf of AdenGulf of Aden

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

Rift propagationRift propagation

Caledonian-Caledonian-HercynianHercynianbeltsbelts

NAGFNAGF

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

Pre-structured lithosphere, oblique riftingPre-structured lithosphere, oblique rifting

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

EARS follows pre-structured lithosphereEARS follows pre-structured lithosphere

Ebinger, 2005Ebinger, 2005

Extension of continental Extension of continental lithospherelithosphere

MechanicalMechanicalstretchingstretching

MagmaticMagmaticextensionextension

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

Rift branches Proterozoic mobile beltsRift branches Proterozoic mobile belts

MadagascarMadagascar

AfricaAfrica

Lithosphere extension: 2-D processesLithosphere extension: 2-D processes

Decompressional melting during extensionDecompressional melting during extension

Ebinger, 2005Ebinger, 2005

Extension of continental Extension of continental lithospherelithosphere

MechanicalMechanicalstretchingstretching

MagmaticMagmaticextensionextension

Lithosphere extension: 3-D processesLithosphere extension: 3-D processes

Tectonic processes involvedTectonic processes involved

Setup geometry Setup geometry lateral variations in lithosphere lateral variations in lithosphere architecture, different geological architecture, different geological provincesprovinces

Boundary conditionsBoundary conditions laterally varying boundary conditions,laterally varying boundary conditions,oblique extensionoblique extension

Basics needs:Basics needs:

Thermo-mechanical model?Thermo-mechanical model?Layered lithosphere?Layered lithosphere?

Existing numerical modelsExisting numerical models

Elastic Plate Model: Elastic Plate Model: Hubert-Ferrari et al., 2003Hubert-Ferrari et al., 2003

Rift propagation (=crack propagation)Rift propagation (=crack propagation)

Assumption: lithosphere is an elasticAssumption: lithosphere is an elasticplate in which viscous/ductile behaviorplate in which viscous/ductile behaviorplays no (important) roleplays no (important) role

Existing numerical modelsExisting numerical models

Finite Element Models:Finite Element Models: Dunbar and Sawyer, 1996 Dunbar and Sawyer, 1996

Rift propagationRift propagation

- Symmetrical model- Symmetrical model- Equations: creeping flow, heat flow- Equations: creeping flow, heat flow

Existing numerical modelsExisting numerical models

Boundary Element Models: Boundary Element Models: Katzman, ten Brink & Lin, 1995Katzman, ten Brink & Lin, 1995

Pull-apart basin formationPull-apart basin formation

Analogue modeling studiesAnalogue modeling studies

(Tron and Brun, 1991)(Tron and Brun, 1991)

Sand & silicone experimentsSand & silicone experiments

+ fault structures+ fault structures - thermal effects, rheology- thermal effects, rheology

More analogue results

Analogue modeling studies of oblique riftingAnalogue modeling studies of oblique rifting

(Giacomo Corti, 2004)(Giacomo Corti, 2004)

Centrifuge modelCentrifuge model

+ fault structures+ fault structures - thermal effects, rheology- thermal effects, rheology

Our modeling approachOur modeling approach

Finite element model, Lagrangian approachFinite element model, Lagrangian approach

Mechanical part: based on TektonMechanical part: based on Tekton

Thermal part: based on FELIBThermal part: based on FELIB

Thermo-mechanical modelThermo-mechanical model

Numerical modeling of oblique riftingNumerical modeling of oblique rifting

Mechanical part Mechanical part Thermal partThermal part

Visco-elastic deformation,Visco-elastic deformation, Heat flow equationHeat flow equationcorrection for plastic/brittlecorrection for plastic/brittle Heat production in crustHeat production in crustbehaviorbehavior

Buoyancy forcesBuoyancy forces

T-dependent power-T-dependent power-law rheologylaw rheology

Numerical modeling of oblique riftingNumerical modeling of oblique rifting

Model setupModel setup

Oblique riftingOblique rifting

Results: Map view of model domain, crustal thinningResults: Map view of model domain, crustal thinning

ObliqueOblique riftingrifting

ObliqueOblique riftingrifting

NormalNormal riftingrifting

Oblique riftingOblique rifting

Results: Surface heat flow for oblique rifting testResults: Surface heat flow for oblique rifting test

* Rift zones follow the weak trend as a group, but are* Rift zones follow the weak trend as a group, but are individually oriented according to extension directionindividually oriented according to extension direction

* Asymmetric development of individual rifts* Asymmetric development of individual rifts

* Rift zones follow the weak trend as a group, but are* Rift zones follow the weak trend as a group, but are individually oriented according to extension directionindividually oriented according to extension direction

* Asymmetric development of individual rifts* Asymmetric development of individual rifts

*Asymmetric development of individual rifts*Asymmetric development of individual rifts

*Alternating asymmetric rifts, linked through *Alternating asymmetric rifts, linked through accommodation zones accommodation zones

Example of alternating rift asymmetry can beExample of alternating rift asymmetry can befound in the Malawi Riftfound in the Malawi Rift

Lake MalawiLake Malawi topographytopography

Ebinger et al., 1987Ebinger et al., 1987

Mantle flow beneath rift basinMantle flow beneath rift basin

Rift parallelRift parallel

Rift perpendicularRift perpendicular

Rift propagation modelingRift propagation modeling

Model setupModel setup

Rift propagation: end-member modesRift propagation: end-member modes

Evolution of crustal thinning, map view of model domainEvolution of crustal thinning, map view of model domain

StrongStrongplateplate

WeakWeakplateplate

Inter-Inter-mediatemediate

Rift propagation: end-member modesRift propagation: end-member modes

Rift-parallel component of velocity field, map viewRift-parallel component of velocity field, map view

Stalled riftStalled rift

Continuous Continuous propagationpropagation

Rift propagation: end-member modesRift propagation: end-member modes

Horizontal shear stress, map viewHorizontal shear stress, map view

Stalled riftStalled rift

Continuous Continuous propagationpropagation

* Modeling of smaller scale structures * Modeling of smaller scale structures

* Grid spacing, calculation time* Grid spacing, calculation time

* Remeshing, large deformation* Remeshing, large deformation

* Brittle/ductile behavior* Brittle/ductile behavior

Improvements neededImprovements needed

What works fineWhat works fine

* Flexibility of geometry, initial setup and boundary conditions* Flexibility of geometry, initial setup and boundary conditions

* Application to deformation of oceanic lithosphere* Application to deformation of oceanic lithosphere

* Modeling of large scale structures* Modeling of large scale structures

SNAC?SNAC?

Commercial codes such asCommercial codes such as ANSYSANSYSABAQUSABAQUS……....FLACFLAC

Other optionsOther options