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Granduc -
Engineering and Planning cont...
MINING
PRACTICE
The Granduc
deposit consisted of a number of separate orebodies designed as "A";
"Dl" and "82"; "C", which was the largest and in which a minor zone
designated "Ch" (the "h" being for hanging wall) was providing much of
the production tonnage at the time of Western Miner's mine tour; and "F"
which is under development and which lies to the north beyond a granitic
dike. The "82" zone merges with the "C" zone in the southern portion of
the mine and in turn the widening "C" zone roughly parallels the " A "
zone as they continue to the north.
 During
mining in the "81" and "82" orebodies there would be a tendency to bring
down too great a proportion of dirt fines from the surface. Therefore,
on the steep hillside overlooking the Leduc glacier, the overburden was
being bulldozed to remove these fines. The work was being done by
Caterpillar D-8 tractors, with removal of the waste and dumping by
Scooptrams.
Mineralization
throughout the ore zones had been found to be generally uniform in grade
and composition and is primarily chalcopyrite and pyrrhotite with
associated pyrite and minor amounts of magnetite, galena, and sphalerite.
A great deal of study went into the methods to be used in mining and
extracting the ore, resulting in the decision to use a sub-level caving
method. Later use of the open-stope method is not discounted depending
on the ability of the stopes to support the rock.
The sub-level
caving decision was made following a visit to Sweden where a study was
made of the same method being used. Sub-level intervals, after being
initially set at 40 feet reverted to 30 feet principally due to the
flattening of the "C" orebody in the upper levels and the fact that it
was felt that the 30- ft. interval offered a better opportunity for
control.
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