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How Do I Calculate Tonnage of a WF Model?

Michael Tangwari 3 months ago in Forum updated 3 months ago 3

I am doing a first pass estimation of how much Au is at 1g/t in a gold block/wireframe I created. I will I go about to get a rough calculation of the grade tonnage or the volume of my 1g/t wireframe...???

Please help.

Cheers

Mikes

+2

Hi Michael, 

If you have a block model, your best option is to do a block model report. If you've assigned the WF to the BM using sub blocks that will account for the volume, or if you've used a block factor, specifiy the block factor in the form. Alternatively you can specify a wireframe under the options tab if you haven't already applied factors or sub blocks. 

  • Specify a cut-off set under estimation and this will give you a grade tonnage table, be sure to use "largest value down" option. Make sure your final bin is greater than the largest value in your BM, otherise you'll miss the tail. 
  • Note the BM report will give you the grade and tonnage in each bin, and a cummaltive tonnage and grade.
  • Alternatively apply a filter to the BM for Au>1 and report with non (Global)
  • Remember to specify your grade unit and the metal (g/t) and metal unit (ozt)

If you dont have the block modelling module, and are using a BM provided by someone else, I think you can still use Grade Tonnage Curve, under the Analysis section on the Stats Tab. Generating descriptive statistics on the block model will allow you to do the same if you give each block a tonnage. 

If you dont have a block model and only have assay data, you can produce a wireframe grade tonnage report, but this wont tell you about the grade tonnage relationship. For that you'll need to do a change of support on the assay data (preferably composited first) to tell you the portion of the population which is above cut-off grade and what the average grade above cu-off is. Note that this process is sensitive to non stationarity and clustering so can give misleading results without due consideration. 

There's always more than one way to skin a cat in Micromine! 

+1

Hi Michael,

As Richard says, there are many ways to skin a cat, and all his methods are perfectly valid. If your wireframe is >1g/t and all you want is the average grade of the composites within it, then the Grate Tonnage from 3D points will work. This is a raw number and will likely overstate the grade unless you use a fairly heavy topcut (although I have found 97 percentile works well enough depending on the grade distribution), and you might like to decluster the data as well (use Stats/Cell declustering) as this helps "smooth" the grade a bit (which helps jump through all the messy statistical hoops, select the decluster weighting field in the GT form under weighting). I find this gives me a fairly representative average grade and tonnage for the volume (you will need an average SG) and is a good thumb suck for a working number...But definitely not something you would take to the bank and bet your house on. If you are after the full GT curves and a series of cut-offs, then Richard's suggestions are better options.

Thank you very much Ronald. problem is I do not have the Block Model module.