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Fig. 4.8 Illustration of occurrence of deposits with respect to 16 (10 km
10 km) cells within a
(40 km
40 km) unit area. Three smaller cells (
k
¼
3) contain one or more deposits. This could be
a realization of a random variable with expected value
m
¼
4 that is shown on the contour map.
Suppose that this random variable has a binomial distribution, then the probability that
k
¼
3
amounts to 21 % (Source: Agterberg and David
1979
, Fig. 3)
4.4 Abitibi Copper Hindsight Study
The Abitibi area copper potential map constructed in 1971 was based on 1968
statistics for production and reserves (Agterberg et al.
1972
). During the 1970s a
considerable amount of exploration for additional massive sulphide deposits was
undertaken in this region. Agterberg and David (
1979
) evaluated the prognostic
copper potential contours constructed from 1968 data on the basis of the locations
and sizes of seven discoveries made between 1966 and 1977 (Millenbach, Louvem,
Conigo, Iso-Copperfield, New Insco, Corbet and Montcalm deposits). The first
three of these deposits already had been discovered when the original statistical
analysis was performed but published figures on production and reserves were not
yet available for them at that time. All seven new discoveries occurred either within
the vicinity of one or more of the original set of 41 deposits, or within the three
relatively high copper potential subareas without known deposits in 1968 men-
tioned before (also see Wellmer
1983
). Together the 41 deposits contained 3.12 Mt
of copper at the end of 1968. In 1977, the set of (41 + 7
) 48 deposits contained
5.23 Mt Cu. This increase was largely due to increased production and reserve
estimates for the Kidd Creek mine (near Timmins, Ontario). The overall change in
geographic distribution of large copper deposits from 1968 to 1977 can be seen by
comparing Fig.
4.10b
with Fig.
4.10a
. Later discoveries (until 2008) are considered
in Fig.
4.10c
.
¼
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