Abstract
Diamond drill-hole grades are known to be of better quality than those of blast holes; is this true? We present a formal study of a porphyry copper deposit in Chile where the variogram of 3 meter long drill hole samples is compared to 15 meter long blast hole ones and we show that the blast holes can be assumed to regularizing the point information deduced from the drill holes, except for a nugget effect specific to the blast samples. Complementary analyses based on migrated data show that the drill holes also have their own errors.
Highlights
The present study establishes a formal link between blast and drill holes which leads to linear systems:■■Removal by kriging of the blast error; ■■Deconvolution of the blast measurements to transform them into point ones; ■■Block modeling where drill and blast holes are used together
This study shows how to combine measurements known on two different supports, a very complex challenge
First conclusions If we omit the problem of the nugget effect, we see that both blast and drill holes can be considered as a regularization of the same reality according to their respective supports
Summary
The present study establishes a formal link between blast and drill holes which leads to linear systems:. The data comes from an open-pit copper mine in Northern Chile of which a 600 × 400 × 125 m3 sub domain is analysed (Figure 1) as it is almost homogeneously covered by around 3,000 drill-hole samples(3 m long) and 13,000 blast-hole samples (15 m long). Over this sub domain, the averaged copper grades of the blast and the drill holes are almost identical (around 0.6%). The variograms of blast and drill holes have similar behaviours (Figure 2), a high percentage of nugget effect (around 40%) and they differ mainly by their sills (0.12 for drill holes, 0.8 for blast holes), a comprehensible property as the blast support is larger
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