Cordillera Lith Removal Models

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Cordillera Lith Removal Models

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Scroll below image box for models and movies.

Figures for Roy:

1) Topographic map showing locations of cross sections and archean v proterozoic cratons. Geol_Prov.png

2) Cross sections through Baos model: Cross_sect2.png

3) An attempt at making a 3D view of the tomography and how it lines up with cratons and the RMT: tomography.png

Lydia's scratch area:

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    Nonlinear viscosity in the ashthenosphere and mantle lithosphere with variable density contrasts across Craton-Cordillera Boundary

    • Models to look at the deformation of the edge of the craton due to edge driven convection
    1. MODEL NAME: MINVISC_NOSLAB_BUOY4_DBLM1    "B4_M1"
      1. Viscosity Model
      2. Density Model
      3. Particle Model
    2.  
    Parameters Table
    Model Name Crat Rho (max/ref) L Crat Rho (max/ref) Lith Rho Crat Visc L Crat Visc Lith Visc
    B4_M1 3300/3220 3330/3250 _/3300 Min Dif/Dis Dryx2 Min Dif/Dis Dry Min Dif/Dis

     

     

    Dynamic mode viscosity

    We use temperature, pressure and strainrate dependent viscosity based on the equations for diffusion and dislocation creep of olivine. The effective viscosity resulting from diffusion or dislocation creep deformation has a similar magnitude in the upper mantle \citep{Karato1993} however at each timestep we take the minimum viscosity from all 4 deformation mechanisms (dislocation wet, dislocation dry, diffusion wet, diffusion dry) to provide the effective viscosity \citep{Eaton20091}.  See figure below.

     

    Buoyancy of the cratonic lithosphere is relative to the adjacent asthenosphere.

    Since the adjacent asthenosphere is slightly hotter than the craton, in order to achieve neutral buoyancy we must reduce the density - temperature relationship for the craton. We then compare the integrated density of the asthenosphere and craton to ensure neutral, positive and negative buoyancy of the craton relative to the adjacent asthenosphere. (see figure below)

     

    Integrated density of the craton adjacent asthenosphere from 120 km - 200 km is: 3289 kg/m3. This value should be use to evaluate relative buoyancy of the craton
    Model Name Density Movies OBS
    MINVISC_NOSLAB_BUOY Integrated cratonic density from 120 km - 200 km is 3281 kg/m3 MINVISC_DENS.avi MINVISC_PARTICLE.avi MINVISC_VISCOSITY.avi Advance
    MINVISC_NOSLAB_NORMAL Integrated density is 3324 kg/m3 MINVISC_NORMAL_DENS.avi MINVISC_NORMAL_PARTICLE.avi MINVISC_NORMAL_VISCOSITY.avi RETREAT
    MINVISC_NOSLAB_NEUTRAL Integrated density is 3290 kg/m3< These models are old and had a slightly more dense craton. The new models will be exactly like the plot below. MINVISC_NEUT_DENS.avi MINVISC_NEUT_PARTICLE.avi MINVISC_NEUT_VISCOSITY.avi
    Layered Cratonic Viscosity models with no slab dip boundary
    Model Name Density Viscosity OBS
    NL7LO_noslab_mod7 NO LAYER: L1: Low density(3260) L2: 3260 max NO LAYER:ASTH min diswet, LITH diswet, COH=100 : CRAT L1 DisDry, L2 DisDry Advance
    NL7LO_noslab_mod6 NO LAYER: L1: Low density(3260) L2: 3260 max NO LAYER:ASTH min difdis, LITH diswet, COH=100 : CRAT L1 DisDry, L2 DisDry Advance
    NL7LO_noslab_mod5 NO LAYER: L1: Low density(3250) L2: 3250 max NO LAYER: ASTH LITH min difdis COH=1000 : CRAT L1:DisDry L2: DisDry Advance
    NL7LO_noslab_mod4 NO LAYER: L1: Low density(3250) L2: 3250 max NO LAYER: Lith, Asth COH=100 : CRAT L1:DisDry L2: DisDry Advance follows delam
    NL7LO_noslab_mod3 L1: Low density(3280) L2: 3290 max Lith, Asth COH=1000 : CRAT L1:DisDry L2: DisWet 1COH ???
    NL7LO_noslab_mod2 L1: Low density(3250) L2: 3280 max Lith, Asth min difdis COH=100 : CRAT L1:DisDry L2: DisWet 1COH some adcance
    NL7LO_noslab_mod L1: Low density(3280)L2: 3290 max Lith, Asth COH=100 : CRAT L1:DisDry L2: DisWet 1COH Delam, no advance
    Layered Cratonic Viscosity models
    Model Name Density of Craton Layers Viscosity of Craton Layers Movies
    ShiftSlab_NL7LO-Layered6 L1: Low density(3290) L2: 3300 max L2 cohesion 1000 MPa, L2 visc discl wet COH=1e-6. Cordilleran lith and asth have minimum visc based on SR, temp, press
    ShiftSlab_NL7LO-Layered5 L1: Low density(3290) L2: 3300 max L2 cohesion 1000 MPa, L2 visc Disl. Wet COH=1e-6
    ShiftSlab_NL7LO-Layered4 Low density (3290) both layers L2 cohesion 1000 MPa, L2 visc Disl. Wet COH=1e-6 SNL7LO_L4_particle.mp4 SNL7LO_L4_dens.mp4
    ShiftSlab_NL7LO-Layered3 Low density (3290) both layers L2 Cohesion 1000 MPa, L2 visc Disl. Wet COH=100e-6 (cord lith) SNL7LO_L3_particle.mp4 SNL7LO_L3_dens.mp4
    ShiftSlab_NL7LO-Layered2 Low density (3290) both layers L2 Cohesion 100 MPa, L2 visc Disl. Wet COH=100e-6 (cord lith) SNL7LO_L2_particle.mp4 SNL7LO_L2_dens.mp4
    ShiftSlab_NL7LO-Layered1 L1 Low density (3290), L2 temp dep dens L2 Cohesion 100 MPa, L2 visc Disl. Wet COH=100e-6 (cord lith) SNL7LO_L1_particle.mp4
    Density variations parameters
    Density Name Criteria
    V Dense Set the Cordillera reference density to 3400 kg/m3 at a temperature of T=1300C.
    Dense Set the Cordillera reference density to be 3350 kg/m3 at a reference temperature of T=1300 C
    Oceanic The expected density at temperature for normal oceanic lithosphere defined by 3300 kg/m3 at T=1300C
    Neutral Neutral buoyancy is made by making the craton density be less than or equal to 3300 kg/m3, since this is the density of asthenospheric mantle at 1300C then this would make the craton neutrally buoyant with the asthenosphere.
    Slightly Less Dense Set the maximum density in the craton to not exceed 3290 kg/m3
    Less Dense Set the maximum density in the craton to 3250 kg/m3
    Models Run with no slab boundary on the LHS
    Model Name Cordillera Density Craton Density Movies RESULT
    M7LO No Slab Oceanic Slightly Less Dense M7LONSdensity.avi M7LONSparticle.avi M7LONSviscosity ADVANCE
    M15 No Slab Oceanic Less Dense M15NSdensity.avi M15NSparticle.avi M15NSviscosity.avi ADVANCE
    M12:No Slab Oceanic Neutral M12NSdensity.avi M12NSparticle.avi M12NSviscosity.avi RETREAT
    These models have a slab with no buoyancy so that it acts as a buffer to flow only: Non Buoyant Slab (NBS)
    Model Name Cordillera Density Craton Density Movies Result: Advance or Retreat
    M14:NBS Oceanic Oceanic M14NBSdensity.avi M14NBSparticle.avi M14NBSviscosity.avi RETREAT
    M12:NBS Oceanic Neutral M12NBSdensity.avi M12NBSparticle.avi M12NBSviscosity.avi STATIONARY
    M7L:NBS Dense Slightly Less Dense ADD OUTPUT HERE NOT COMPLETE M7LONBSdensity.avi M7LONBSparticle.avi M7LONBSviscosity.avi ADVANCE
    M7LO:NBS Oceanic Slightly Less Dense M7LONBSdensity.avi M7LONBSparticle.avi M7LONBSviscosity.avi ADVANCE
    M7:NBS Dense Less Dense M7NBSdensity.avi M7NBSparticle.avi M7NBSviscosity.avi ADVANCE
    M15:NBS Oceanic Less Dense M15NBSdensity.avi M15NBSparticle M15NBSviscosity ADVANCE
    These models had a little negative buoyancy in the slab
    Model Name Cordillera Density Craton Density Movies RESULT:ADVANCE OR RETREAT
    Model 13 V Dense Oceanic Delamination at 9.4Myr M13density.avi M13particle.avi M13viscosity.avi M13strainrate.avi RETREAT
    Model 13b Dense Oceanic M13bdensity.avi M13bparticle.avi M13bviscosity.avi RETREAT
    Model 14 Oceanic Oceanic M14density.avi M14particle.avi M14viscosity.avi RETREAT
    Model 9 Dense Neutral M9density.avi M9particle.avi M9viscosity.avi M9Density.avi M9dens.avi M9particle.avi M9viscosity.avi ~RETREAT
    Model 12 Oceanic Neutral M12density.avi M12particle.avi M12viscosity.avi ~RETREAT
    Model 7l Dense Slightly Less Dense M7Ldensity.avi M7Lparticle.avi M7Lviscosity.avi ADVANCE
    Model 7LO Oceanic Slightly Less Dense M7LOdensity.avi M7LOparticle.avi M7LOviscosity.avi ADVANCE
    Model 7 Dense Less Dense M7density.avi M7particle.avi M7viscosity.avi ADVANCE
    Model 15 Oceanic Less Dense M15density.avi M15particle.avi M15viscosity.avi ADVANCE

    Dipping Craton viscosity examples

    We know there is a dip in the craton near the border with the proterozoic terranes. Therefore it is applied in these models. This section has linear but temp and press dependent viscosity with a yield strength.

    1) LinVisc-test3-stronger-DipCraton -Super nice example! LV_Dip.avi

    2) LinVisc-test3-stronger-DipCraton2 - Craton too weak: LV_Dip2.avi

    3) LinVisc-test3-stronger-DipCraton4 - Just weathers away cord lith: LV_Dip4.avi

     

    Non linear viscosity dipping craton examples

    These models have non linear viscosity 

    1) Model NL1: LinVisc_test3-Stronger-DipCratonNL : LV_DC_NL_viscosity.avi

    2) Model NL2: LinVisc_test3-Stronger-DipCratonNL2

    3) Model NL3: LinVisc_test3-Stronger-DipCratonNL3

    4) Model NL3: LinVisc_test3-Stronger-DipCratonNL4

    5) Model NL3: LinVisc_test3-Stronger-DipCratonNL5: LV_DC_NL5_viscosity.avi, LV_DCLNL5_density.avi

    6) Model NL3: LinVisc_test3-Stronger-DipCratonNL6

    Non-Linear Viscosity MODEL TABLE

    Models Lith Visc Crat Visc Coh Lith
    Model 1: Nonlinear DisDry x4 DifDry 5 MPa
    Model 2: Nonlinear DisWet DisDry 200 MPa
    Model 3: Nonlinear DisWet DisDry 100 MPa
    Model 4: Nonlinear DisWet DisDry 50 MPa
    Model 5: Nonlinear DisWet DisDry 5 MPa
    Model 6: Nonlinear DisWet DisDry 10 MPa

    Linear Viscous models

    Models:

    Models Lith Visc Crat Visc Coh Lith Lower Crust Viscosity
    Model 1:LinVsic_test DisDry 100 20 MPa 0.1
    Model 2: LinVisc_test-5 DisDry 100 20 MPa 0.05
    Model 3: LinVisc_test3 DisDry DifDry 5 MPa 0.1
    Model 3:LinVisc_LikeSuccess_StrongerLith DisDry 100 100 MPa 0.1
    Model 3:LinVisc_test2 DisDry DisDry 20 MPa 0.1
    Model 3:LinVisc_test3-stronger DisDry x2 DifDry 5 MPa 0.1
    Model 3:LinVisc_success DisDry 100 20 MPa viscostiyFnLCrust
    • Model 1: LinVisc_test Movie viscosityLV_t.avi
    •  
    • Model 2: LinVisc_test5
      • Movie viscosity: LV_t5.avi
      •  
      • Same as above but with weaker L Crust. Very similar behaviour
    •  
    • Model 3: LinVisc_test3
      • A Rayleigh-Taylor instability, due to a very low Cohesion.
      • Craton has DifDry- strong craton but not as strong as 100.
      • Movie viscosity: LV_t3.avi
    •  
    • Model 4: LinVisc_LikeSuccess_StrongerLith
      • Very strong lith, the Co is 100 MPa.
      • This was too strong. Lith did not thin, code does not converge
      • Viscosity Movie: LV_t_SL.avi
    •  
    • Model 5: LinVisc_test2
      • Thins and the thinning concentrates near the craton
      • Craton Lith is DisDry same as Lith
      • Viscosity Movie: LV_t2.avi
    •  
    • Model 6: LinVisc_test3_stronger
    • Model 7: LinVisc_success
      • No real difference to Model1: LinVisc_test
      •