Geoscience Reference
In-Depth Information
Fig. 14.22
Partial view of estimated TCu grades, Bench 2440
exceptions. The rotation angles used to specify the search
ellipsoids are given according to the following convention:
•
Θ
1
= left-hand rotation of the
X-Y
axes about the
Z
-axis,
clockwise is positive (azimuth).
•
Θ
2
= right-hand rotation of the
Y
′
-Z
′ axes about the
X
′-
axis, positive is up (dip).
•
Θ
3
= left-hand rotation of the
X
′
-Z
′ axes about the
Y
′-axis,
positive is down (plunge).
Figure
14.22
shows a partial view of the estimated grades for
Bench 2,440 m, in the southern area of the deposit. Note in
this view a NNE-trending zone of higher grades (in red and
blue, TCu > 1.50 %), which corresponds to one of the major
structural controls in the deposit.
more restrictive kriging pass, then it has closer and better
information than any block estimated during the second or
third passes. If the passes (kriging plans) are related to and
influenced by geologic knowledge, then they can be inter-
preted in the same general sense that is required by current
resource classification systems. Additional aspects to con-
sider are:
• If the kriging passes are to be used as the basis for resource
categorization, then basic geologic and geostatistical cri-
teria must be met. In the case of Cerro Colorado, this is
the case because the search radii used in pass is related
to the correlogram ranges and anisotropies. The kriging
passes are different for each Domain (just as the correlo-
gram models are), and therefore they reflect the different
geologic characteristics of each Domain.
• The use of kriging passes as a basis for resource catego-
rization implies more complexity than most of the other
options used in practice. Criteria such as the minimum
distance or the kriging estimation variance are simpler, in
the sense that they rely on a smaller number of variables
to determine the category of each block. Also, it is some-
14.1.23
Resource Classification
The method used to classify resources is based initially on
the kriging passes described above. These passes provide
a measure of the quantity and quality of information used
to estimate each block. If a block has been estimated in the
