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3D model of a Ni-Cu-PGE ore body - Margaux Le Vaillant and June Hill (CSIRO)

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This talk describes the process of generating a 3D model of the Kevitsa (Finland) ore body through wavelet transform of geochemistry obtained from drill core. Tesselation is then used to determine an appropriate scale of study for the data and 3D modelling. Subtle signals are identified, while the effects of analytical noise are dampened through this process. A genetic model for ore body formation was also formulated due to the success of the data filtering process.

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3D model of a Ni-Cu-PGE ore body - Margaux Le Vaillant and June Hill (CSIRO)

  1. 1. 3D Model of a Ni-Cu-PGE Ore Body MINERAL RESOURCES Margaux Le Vaillant, June Hill and Stephen J. Barnes May 2017 The Kevitsa Cu-Ni-Au-PGE mine, northern Finland
  2. 2. Layered Intrusions A simplified ore body model | Margaux Le Vaillant and June Hill2 | • Repositories of some of the largest ore bodies on earth of Cu, Ni PGE, Cr, V… • Large intrusions presenting compositional layering  This layering gives us information on the genetic magmatic processes at play…  Need for a meaningful way to visualise these variations in 3D
  3. 3. Kevitsa Intrusion A simplified ore body model | Margaux Le Vaillant and June Hill3 |
  4. 4. Kevitsa Ore A simplified ore body model | Margaux Le Vaillant and June Hill4 | plag ol px sulf
  5. 5. Kevitsa 3D Model A simplified ore body model | Margaux Le Vaillant and June Hill5 | Variations within the intrusion poorly modelled
  6. 6. Kevitsa 3D Model A simplified ore body model | Margaux Le Vaillant and June Hill6 |  But access to a gigantic assay database! (>92,000 analyses) Variations within the intrusion poorly modelled
  7. 7. Ore Classification A simplified ore body model | Margaux Le Vaillant and June Hill7 | Ni < 2% - ‘False Ore’ S < 0.5% - ‘Not Ore’ Ni > 2% and Pd > 1,500 ppm ‘Normal Ore – High Pd’ Ni > 2% and Pd < 1,500 ppm ‘Normal Ore – Low Pd’ Ni > 10% ‘High Ni-PGE Ore’
  8. 8. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill8 | Assay points visualised and classified individually / no ‘lumping’ or domaining
  9. 9. A simplified ore body model | Margaux Le Vaillant and June Hill9 | 3D visualisation Need for an objective & fast simplification of the model in order to distinguish the large scale variations from the small scale one  Upscaling method using continuous wavelet transform (CWT) and tessellation methods WORKFLOW
  10. 10. Multiscale Boundary Detection A simplified ore body model | June Hill10 | Signal Signalsmoothing Increasingscale
  11. 11. Multiscale Boundary Detection A simplified ore body model | June Hill11 | Signal Signalsmoothing inflection point in signal: best estimate of boundary location Increasingscale many boundaries few boundaries
  12. 12. A simplified ore body model | June Hill12 | continuous wavelet transform using 2nd derivative of Gaussian wavelet (convolve wavelet with signal over range of scales) (smooth & find inflection points) Method zero contours of 2nd derivative
  13. 13. A simplified ore body model | June Hill13 | Multiscale Spatial Domaining “Tessellation” of continuous wavelet transform Method involves depth-correction of zero contours
  14. 14. A simplified ore body model | June Hill14 | signal Filter One scaleTessellation
  15. 15. A simplified ore body model | June Hill15 | Combine Domain Boundaries
  16. 16. A simplified ore body model | June Hill16 | Classify Combined Domains
  17. 17. Classification by Domain vs Interval A simplified ore body model | June Hill17 | Low S High S, Low Ni Mod Ni, Low PGE Mod Ni, High PGE High Ni ORETYPES IntervalDomain
  18. 18. Effect of Filtering Level A simplified ore body model | June Hill18 | Low S High S, Low Ni Mod Ni, Low PGE Mod Ni, High PGE High Ni ORETYPES Weak filter Strong filter 50% 70%
  19. 19. Effect of Filtering Level A simplified ore body model | June Hill19 | Low S High S, Low Ni Mod Ni, Low PGE Mod Ni, High PGE High Ni ORETYPES weak changes disappear strong changes are preserved Filter
  20. 20. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill20 | unfiltered
  21. 21. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill21 | 70% Filtered
  22. 22. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill22 | Unfiltered 100
  23. 23. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill23 | 70% Filtered 100
  24. 24. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill24 | Unfiltered
  25. 25. 3D visualisation A simplified ore body model | Margaux Le Vaillant and June Hill25 | 70% Filtered
  26. 26. Interpretation A simplified ore body model | Margaux Le Vaillant and June Hill26 |
  27. 27. A simplified ore body model | Margaux Le Vaillant and June Hill27 | Interpretation
  28. 28. Genetic Model A simplified ore body model | Margaux Le Vaillant and June Hill28 | Interconnected sill sediment-complex choked with country rock inclusions
  29. 29. Genetic Model A simplified ore body model | Margaux Le Vaillant and June Hill29 | Larger magmatic chamber
  30. 30. Genetic Model A simplified ore body model | Margaux Le Vaillant and June Hill30 | Freely convecting magma chamber
  31. 31. Genetic Model A simplified ore body model | Margaux Le Vaillant and June Hill31 |
  32. 32. Conclusions A simplified ore body model | Margaux Le Vaillant and June Hill32 | • Consistent and objective reduction of the number of units in each drill hole, and creation of a simplified 3D model of the orebody  Insights on the genetic processes at play • Advantages of automated domaining process:  Consistent results over whole data base  Time saving • Domaining using CWT and tessellation results in domains whose size is a reflection of the location of major changes in the variable values – not fixed length like in conventional compositing of drill holes
  33. 33. A simplified ore body model | Margaux Le Vaillant and June Hill33 | Thank you!
  34. 34. A simplified ore body model | June Hill34 |
  35. 35. 35 | S NiS PdIntervals Domains Low S High S, Low Ni Mod Ni, Low PGE Mod Ni, High PGE High Ni A simplified ore body model | Margaux Le Vaillant and June Hill Making Sense of the Results

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