Geoscience Reference
In-Depth Information
T
able 14.5
Density values used in prior resource models
CuT, Expl. vs Infill, UG=1
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4.00
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is shown, while the distribution of the TCu grades from the
in-fill drill holes is shown in the
Y
-axis.
No corrections of any type were performed, since it is not
clear which of the two drill campaigns tend to be closer to
the true in situ grade. Several options were available, but in
general it would be expected that infill drilling is potentially
less accurate, because it is faster and the samples may be of
lesser quality. This has not been demonstrated, but if it were
the case, then using infill drilling provides a degree of con-
servatism to the overall estimate.
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
CuT, Expl., UG=1
Fig. 14.7
Q-Q TCu plot, showing exploration vs. infill drill holes, Es-
timation Domain 1 (Oxide)
CuT, Exp. vs Infill, UG=4
6.00
5.00
14.1.10
Laboratory Quality Assurance-Quality
Control (QA-QC)
4.00
3.00
A complete QA-QC follow-up of the laboratory assays was done
as the drilling campaign progressed. Details of this QA-QC pro-
gram are not given here, but it followed the concepts discussed
in Chap. 5. In general, TCu analyses are more accurate and pre-
cise than SCu assays, due to the nature of the assaying methods
involved. In both cases, however, the results were satisfactory
and within acceptable standards for this type of deposit.
2.00
1.00
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
CuT, Exp., UG=4
Fig. 14.8
Q-Q TCu plot, showing exploration vs. infill drill holes, Es-
timation Domain 4 (Sulfide)
14.1.11
Topography
source models obtained from exploration drill holes. It
was hypothesized that there may be differences in the Cu
grades obtained by drill holes form the earlier exploration
campaigns (pre-operation), approximately to a 100 × 100 m
grid, compared to later in-fill drill holes, used for detailed
mine planning and budgeting, and drilled approximately on
a 50 × 50 m grid.
Since there were no twinned exploration holes, it is diffi-
cult to perform a statistical comparison that would unequivo-
cally indicate whether older drill holes are biased with re-
spect to newer information. Globally within each estimation
domain, however, it is evident that the initial drill holes (on
a 100 × 100m grid) reported higher Cu grades than the in-fill
drill holes. Figures
14.7
and
14.8
show the Quantile-Quan-
tile (Q-Q) plots for the two TCu grade distributions of the
most important oxide and sulfide domains. On the
X
-axis the
grade distributions from the original exploration drill holes
The topography used in the model is based on an aerial pho-
togrammetric survey, which was tied to control points in the
field. It is considered that the topographic surface is accurate
to ±2 m, both in the horizontal and the vertical directions.
Additionally, the pit surface as of January 31, 2003, was
taken as the actual pit surface for calculation of remaining
resources. This is in addition of the already mentioned aux-
iliary surface created 80 m above current pit surface, used to
select drill holes and blast holes for various data validation
exercises, model calibrations, and reconciliations.
14.1.12
Density
The density database available consists of 1,591 samples
taken from drill hole data, and tested for density in sev-
eral campaigns during the late 1990s. Table
14.5
shows
