Not easy to see the difference in coloured areas between these two images. Looks like area 2 is larger in the 1% cut off model..
This should give a good order of magnitude and way better than my thought model.
Still wonder where the near doubling at higher grade comes from if the projected surface area is not the main cause.
Area x depth x SG give the simple volume. [MRE block modes are effectively the sum of a similar calculation for each + complex statistical analysis - Realm of resource geos that is highly specialised.] SG is unlikely to change much unless more fresh rock (higher SG) is included So if area is only +10-20% then depth is likely the main factor that would cause a significant increase in the MRE Very simplistic as grade continuity at different cut offs would also impact.
Why use 0.25% as a cut off? Most simple explanation might be that it gave a nice round 1% for the initial MRE.
From memory the residual grade for holes with multiple higher grade intersections is commonly 0.2-0.5+-% and produces bulk grades well over the 1% level.. Thus using 0.25% cut off does include the bulk zones in many instances.
Two near random choices to show the latter point.
HOLE ID
intersections
metres
Nbx
1
ac 24-2
main
64
1.11
2
FR-TO
incl 1
19
2.4
3
29- 93
1
2.03
4
2
1.23
5
Residual
42
0.5
HOLE ID
intersections
metres
percent
1
ac 24-4
main
43
2.73
2
FR-TO
incl 1
25
4.36
3
29-72
incl 2
4
incl 3
5
Residual
18
0.5
Using a .25% cut of would include the 'bulk' holes like these.
Would not effect the MRE but recently (since 2024) WA1 have taken to drilling more vertical holes moving away from inclined (mainly -60). IMO it makes sense for the sub horizontal mineralisation in the weathered profile where little benefit would come from inclined holes - more industry standard for first pass and useful at times for some purposes.
================== What is the source for the block model and any discussion of underlying assumptions? Will be good if it is giving a fair approximation of the upcoming MRE.
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