The Aff t f R di                        Th Affect of Radiometric T                                             t i Truckk ...
Introduction• The intention of this  presentation is to:  – Di    Discuss th i            the importance                  ...
What is change of support?•   Support is another name for volume•   The most obvious support change in a mining operation ...
Mining is a selection process•   Mining is a selection process;    –   Define a cutoff    –   Using this criterion, select...
Why is support important?• Example:100 tonneblocks;1600             0.35 % Cutofftonnes at0.4%400 tonneblocks;1600        ...
Why is support important?• The outcome of  applying the selection  criteria (a cutoff of  0.35%) has a  pronounced effect ...
Real Data•   Some real data comes from ERA’s    Ranger #3 Uranium mine, located    approximately 250km east of    Darwin, ...
Real Data            Large blocks are the            block model             Small blocks             are trucks
Global Results•   The results show that the estimate of what will be mined is    very close to what was actually mined•   ...
Support and selection criteria•   However, when we apply a cutoff grade of 0.12% U3O8 we    find that there is a deviation...
Predicting the tonnes and grade•   Before a new area is mined it would be highly desirable to    predict the tonnes and gr...
How to predict the tonnes and grade•   We can use Geostatistics•   I will demonstrate 2 methods:    –   Affine Correction ...
Demonstration of change of support•   In order to demonstrate some    examples of change of support,    a data set has bee...
Simulated Data•   A data set has been created by a geostatistical simulation•   There is a single bench with a mining heig...
Simulated Data – 1 metre spacing                               N = 354,690                               Mean U3O8 grade =...
Simulated Data – Reblocked to 3 by 3 m                               N = 39,480                               Mean U3O8 gr...
Simulated Data – Reblocked to 25 by 25 m                               N = 574                               Mean U3O8 gra...
Grade and Tonnage at Cutoff 0.12% U3O8•   Applying a cutoff of 0.12% U3O8 for the three supports of    simulations:•   Poi...
Sample Data              N = 329              Mean U3O8 grade = 0.152%              Minimum value = 0.024%              Ma...
Semi-Variograms for U3O8   SAMPLES   SIMULATED VALUES   Cross validation:                                Mean of error = 0...
Kriged estimate over bench                             N = 574                             Mean U3O8 grade = 0.153%       ...
Kriged estimate over bench•   Applying a cutoff of 0.12% U3O8 for the kriged estimate:•   Kriged 25 by 25m support: 4.37 M...
First method of change of support – AffineCorrection•   Using an Affine Correction to predict the tonnes and grade:•   Kri...
Discussion on Affine Correction•   The Affine correction is rarely used in practice•   The reason behind this is that esti...
Second method of change of support –Conditional Simulation•   Using the sample data, 10 conditional simulations were made•...
Second method of change of support –Conditional Simulation•   If we make a simulation with a sufficiently dense grid of   ...
Second method of change of support –Conditional Simulation•   We don’t have one answer –    we have 10 equally probable   ...
Conditional Simulation – 25 by 25m reblock                                       25 by 25m blocks from simulation - Grade ...
Conditional Simulation – 3 by 3m reblock                                         3 by 3m blocks from simulation - Grade   ...
Conclusions•   It is important to consider the change of support for mine    planning purposes•   It is possible to perfor...
Final Comment•   If we want to know the support on 3 metres, why don’t we    just estimate into 3 metre blocks?•   Why not...
ReferencesKENDALL, C. J. (1990). Ranger Uranium Deposits. In: Geology of the Mineral Deposits of   Australia and Papua New...
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The Affect Of Radiometric Truck Discrimination On Reconciliation

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Presentation from 2011 Uranium Conference in Perth, Australia. Focuses on selection and the support effect using a case study.

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The Affect Of Radiometric Truck Discrimination On Reconciliation

  1. 1. The Aff t f R di Th Affect of Radiometric T t i Truckk Discrimination on Reconciliation J Carpenter, S Hackett, N Anderson International Uranium Conference Perth, 2011 XstractGroup.com Xstract - Excellence from the OutsetENVIRONMENT GEOLOGY MINING PROCESSING VALUATION RISK TECHNOLOGIES
  2. 2. Introduction• The intention of this presentation is to: – Di Discuss th i the importance t of sample support to grade control – Demonstrate some methods that can be used for “change of change support”
  3. 3. What is change of support?• Support is another name for volume• The most obvious support change in a mining operation is the difference in support between the block model used for planning and the truck volumes that are actually minedPlanning using a Block Model... ...mining using Trucks
  4. 4. Mining is a selection process• Mining is a selection process; – Define a cutoff – Using this criterion, select material above the cutoff and send it criterion to the mill, and – Send material below the cutoff to the waste stockpile.• In I some open cut uranium mines, radiometric truck t i i di t i t k discriminators are used to sort each truckload leaving the pit• This creates a situation where “Perfect Selection” may be assumed
  5. 5. Why is support important?• Example:100 tonneblocks;1600 0.35 % Cutofftonnes at0.4%400 tonneblocks;1600 0.35 % Cutofftonnes at0.4%
  6. 6. Why is support important?• The outcome of applying the selection criteria (a cutoff of 0.35%) has a pronounced effect on the mined grade and tonnages• Fewer tonnes, higher grade
  7. 7. Real Data• Some real data comes from ERA’s Ranger #3 Uranium mine, located approximately 250km east of Darwin, Northern Territory, Australia at latitude 120 41’ S, longitude 1320 55’• Ranger 1 Anomaly 3 (colloquially g y ( q y known as Ranger #3) is situated in Early Proterozoic sediments of the South Alligator Group g p Table adapted from Kendall (1990)
  8. 8. Real Data Large blocks are the block model Small blocks are trucks
  9. 9. Global Results• The results show that the estimate of what will be mined is very close to what was actually mined• This is an excellent outcome: Blocks: 8.08 million tonnes at 0.043 % U3O8 Trucks: 8.02 million tonnes at 0.042 % U3O8
  10. 10. Support and selection criteria• However, when we apply a cutoff grade of 0.12% U3O8 we find that there is a deviation away from what the block model has predicted p Blocks: 803,120 tonnes at 0.232% U3O8 Trucks: 774,800 tonnes at 0.278% U3O8• Outcome: Fewer tonnes, higher grade
  11. 11. Predicting the tonnes and grade• Before a new area is mined it would be highly desirable to predict the tonnes and grade that will be mined on the truck scale• How do we predict the tonnes and grade of material on a truck support above a cutoff grade? t k t b t ff d ?
  12. 12. How to predict the tonnes and grade• We can use Geostatistics• I will demonstrate 2 methods: – Affine Correction – Conditional Simulation
  13. 13. Demonstration of change of support• In order to demonstrate some examples of change of support, a data set has been created by y simulation. It is necessary to do this for a few reasons: – Confidentiality of company data – Real data has additional complexities
  14. 14. Simulated Data• A data set has been created by a geostatistical simulation• There is a single bench with a mining height of 5 metres and a g g g bulk density of 2.8 t/m3• There is a cutoff grade of 0.12% U3O8• The mine is mined by open cut using 130 tonne trucks (which equates to a support of 3 by 3 by 5 metres)• The simulation has been sampled on 25 by 25 metre and 50 by 50 metre centres – this is the drillhole data
  15. 15. Simulated Data – 1 metre spacing N = 354,690 Mean U3O8 grade = 0.152% Minimum value = 0.023% Maximum value = 0.278% Variance = 2.13 x 10-3 (%)2
  16. 16. Simulated Data – Reblocked to 3 by 3 m N = 39,480 Mean U3O8 grade = 0.152% Minimum value = 0.023% Maximum value = 0.276% Variance = 1.51 x 10-3 (%)2
  17. 17. Simulated Data – Reblocked to 25 by 25 m N = 574 Mean U3O8 grade = 0.152% Minimum value = 0.074% Maximum value = 0.238% Variance = 0.79 x 10-3 (%)2
  18. 18. Grade and Tonnage at Cutoff 0.12% U3O8• Applying a cutoff of 0.12% U3O8 for the three supports of simulations:• Point support: 3.66 Mt at 0.173% U3O8• 3 by 3m support: 3.93 Mt at 0.167% U3O8• 25 by 25m support: 4.38 Mt at 0.159% U3O8 b 25 t 4 38 t 0 159%• We will call these the “TRUE” values ill al es
  19. 19. Sample Data N = 329 Mean U3O8 grade = 0.152% Minimum value = 0.024% Maximum value = 0.278% Variance = 2.24 x 10-3 (%)2
  20. 20. Semi-Variograms for U3O8 SAMPLES SIMULATED VALUES Cross validation: Mean of error = 0.0003% Mean squared error = 0.0021(%)2 Mean kriging variance = 0.0019(%)2 (small mean error, theoretical variance within 10% of true variance)
  21. 21. Kriged estimate over bench N = 574 Mean U3O8 grade = 0.153% Minimum value = 0.092% Maximum value = 0.220% Variance = 1.00 x 10-3 (%)2
  22. 22. Kriged estimate over bench• Applying a cutoff of 0.12% U3O8 for the kriged estimate:• Kriged 25 by 25m support: 4.37 Mt at 0.159% U3O8• “True” 25 by 25m support: 4.38 Mt at 0.159% U3O8 y pp
  23. 23. First method of change of support – AffineCorrection• Using an Affine Correction to predict the tonnes and grade:• Kriged 3 by 3m support: 4.03 Mt at 0.165% U3O8• “True” 3 by 3m support: 3.93 Mt at 0.167% U3O8• Close! But no thumbs up
  24. 24. Discussion on Affine Correction• The Affine correction is rarely used in practice• The reason behind this is that estimates are always “normalised” – the histogram of the estimates are more “bell shaped” than the samples bell shaped• The normalising effect is due to the Central Limit Theorem• The change in the shape of the histogram makes this method less reliable
  25. 25. Second method of change of support –Conditional Simulation• Using the sample data, 10 conditional simulations were made• A conditional simulation is any method that maintains the following 5 conditions: – The simulation h the same statistics as the data h l has h h d – The simulation has the same spatial statistics as the data – The simulation has the same multivariate statistics – The simulated value and the data value are the same at the same location – Th simulated variable considers th geology The i l t d i bl id the l
  26. 26. Second method of change of support –Conditional Simulation• If we make a simulation with a sufficiently dense grid of points, points we can re-block the simulations on different re block supports• The 10 conditional simulations are on a 1 by 1 m grid, same as the original simulation, then re-blocked to the 3 and 25m dimensions
  27. 27. Second method of change of support –Conditional Simulation• We don’t have one answer – we have 10 equally probable answers!
  28. 28. Conditional Simulation – 25 by 25m reblock 25 by 25m blocks from simulation - Grade 25 by 25m blocks from simulation - Tonnage Comparison Comparison 0.163 4550000 0.162 0.162 4,488,750 4500000 0.162 4,471,250 cted Grade for 5 by 5m blocks cted Grade for 5 by 5m blocks 4450000 4,427,5004,427,500 0.161 0.161 4,410,000 4400000 4,370,000 4,380,000 0.160 0.160 0.16 4,348,750 4350000 4,322,500 0.159 0 159 b b 0.159 0.159 0.159 0.159 0.159 0.159 4300000 4,287,500 4,243,750 0.158 4250000 0.157 4200000 4,182,500 0.157 4150000Predic Predic 0.156 4100000 0.155 4050000 0.154 4000000
  29. 29. Conditional Simulation – 3 by 3m reblock 3 by 3m blocks from simulation - Grade 3 by 3m blocks from simulation - Tonnage Comparison Comparison 0.168 4100000 0.167 0 168 0.168 4,047,7504,049,136 0.167 4050000 cted Grade for 5 by 5m blocks cted Grade for 5 by 5m blocks 0.167 0.167 4,030,000 4,012,344 4,005,414 4000000 3,987,0183,988,656 0.166 0.166 0.166 3,969,378 0.166 0.165 3,951,864 0.165 0 165 b b 3950000 3,930,000 0.165 0.165 0.165 3900000 0.164 3,865,806 3,859,254 0.164 3850000Predic Predic 0.163 3800000 0.162 3750000
  30. 30. Conclusions• It is important to consider the change of support for mine planning purposes• It is possible to perform change of support using geostatistical methods; e.g. Affine correction, Uniform eg correction Conditioning, Multiple Indicator Kriging, Disjunctive Kriging, Conditional Simulation to name a few• They all do the same thing – predict the tonnes and grade above a cutoff for a certain support
  31. 31. Final Comment• If we want to know the support on 3 metres, why don’t we just estimate into 3 metre blocks?• Why not? Because the answer will be about the same as if we estimate into 25 metre blocks!!• Kriged 25 by 25m support: 4.37 Mt at 0.159% U3O8• Kriged b 3 K i d 3 by 3m support: 4.26 Mt at 0.159% U3O8 t 4 26 t 0 159%• Affine corrected 3 by 3m support: 4.03 Mt at 0.165% U3O8
  32. 32. ReferencesKENDALL, C. J. (1990). Ranger Uranium Deposits. In: Geology of the Mineral Deposits of Australia and Papua New Guinea. Vol 1 ed. F. E. Hughes, pp. 799 – 805. The Australian Institute of Mining and Metallurgy, Melbourne.

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