Hi Fran (I will send this only once!)
Read any of my papers to see that when I publish stuff it always shows how the statistics can be used to ENHANCE the geology, not the other way round. Read my very first 'real' paper in 1974 (which has no geostatistics in it and was actually criticised for this!). This was written jointly with a consultant geologist and its theme is how geology and statistics work together to produce conclusions that neither party could achieve singly.
I am a little worried by your friend Jim's statement that:
"Kreiging works wonderfully on mature gold placers of the Wits. The trouble comes in when attempts are made to apply it to another type of mineralized zone, one that has not been deposited under the same energy regime as the Wits."
(a) not true, fudge factors -- generally known as Mine Call
Factors or Survey Loss Factors (see my 1996 paper) -- have been used for over 100 years on the Wits mines
(b) "geostatistics" as we know it now was not developed on the Wits but in France
(c) restricting the application of spatial statistics to placer deposits does not make sense. There are many other depositional methods which result in a continuous, quasi-stationary bodies in which values at different locations are related to one another. If they weren't related, there would be little point assaying cores in the first place. It may not be a geostatistical type relationship, but there needs to be some pattern in the values to evaluate a resource from limited sampling, surely?
(d) as for other applications, if they produce sensible semi-variograms then they must have some component of distance-based relationship. If not, what should we use instead? Geology alone will give us the
presence and physical characteristics of ore. It doesn't quantify resources sufficiently to satisfy modern shareholders.
I would certainly heartily endorse Jim Tilsley's last comment:
"Statistics, in my experience, may be applicable in ore reserve estimation, (and will solve many problems if properly applied) providing they are used with due reference to the geological controls on deposition."
Wish I'd said that -- oh yeah, I did.
Isobel
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