What is the best way to model a fold in Leapfrog Geo

LorennyGonzalez
LorennyGonzalez Posts: 1
in Leapfrog
Am trying to model a Fold which includes multiple lithologies (Sediments and volcanics) and haven´t get yet with the best tool in Leapfrog Geo to do it, could it be planar structural data? as a surface? with point or polylines?
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Answers

  • MustafaKaplan
    MustafaKaplan Posts: 5
    I guess form interpilant that uses planar structural data would be a good solution. You need to be careful about your data. I would suggest planar structural data should be well distributed inti different litologies and different limbs of the same fold. I would also suggest using data from lithologic contacts if thickness is variable within folded units. Best way is to try to model, and add data where model is not representing geology due to lack of data.
  • WarrenCarter
    WarrenCarter Posts: 3
    Use Structural Modelling > Form Interpolants to create isosurfaces from your structural dataset. Dip and dip direction from a planar surface is all you need. Play with the spacing on isosurfaces until you get something representative of your stratigraphy. Export an iso surface to apply as a trend in your Geological Models. You could model ptygmatic folds with enough structural measurements in your database.
  • Ulziibayar3199
    Ulziibayar3199 Posts: 3

    i tried but it is not work well.

  • JamesLally
    JamesLally Posts: 29 Calcite Rank Badge

    When using structural data you do need to be aware of how the polarity of the structural discs affects generated structural surfaces and therefore the resulting fold. You haven't mentioned the geometry of your fold - the dip of the axial plane (upright, inclined or recumbent), the interlimb angle (isoclinal to open) and the plunge (constant or varying). Orientations of say bedding will have opposite polarity on the overturned limb of a recumbent fold for example. Note that if your structural data is all imported from mapping or some other external dataset there is currently no easy way to change the polarity of a selection of data at the same time - you have to do it for each point manually.

  • GrahamEllsworth
    GrahamEllsworth Posts: 4 Calcite Rank Badge

    Agree, what is the style of folding or is there a fold analog model to follow. I suggest then domaining the Fold into parts - limbs, hinges, axis, penetrating faults, overturned limbs… Then as suggested above use structural discs to create the orientation data of fold geometry paying attention to the desired polarity as you step through each sub-domain. Polarity is 1 for upright bedding and Polarity is -1 for overturned bedding, this is easy enough to change with user generated structural discs.

    Disappointingly, Leapfrog is not as flexible changing the polarity from data loaded into the program. So field collected data (compass, televiewer…) will default to a Polarity is 1. The only work around is to create a selection field in the structural data table and label the sub-domains of the fold via the Scene View and Stereonet. This is why its crucial to have an analog or working interpretation of the fold model (IMO), this way after fold is subdivided into domains you can export the table and in a spreadsheet change the data polarity if necessary based on the fold-domains and reimport into Leapfrog.

    Finally, as other suggest above, use the Form Interpolant to build the fold-domains and scale up combing domains until the Form Interpolant Isosurfaces reflect a reasonable fold geometry.

  • JohnTyrrell
    JohnTyrrell Posts: 5

    Don't forget about offset surfaces if your lithologies are getting squeezed and end up being too narrow in some areas.

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