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SERPENTINE [J ARGILLITE
ALTERATION ZONE

CASSIAR ASBESTOS CORPORATION LIMITED
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SECTION 23,400 N

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(] FAULT ZONE = ADIT
8 DIAMOND DRILL HOLE

FIGURE 5— Cross section: 23,400 N.

voleanic flows are encountered, until, in the “south
peak” area of the mine, the wall rock is predominently
volcanic. These rocks are generally structureless, with
the general flow direction sub-parallel to the ser-
pentine emplacement. A major fault system (striking
east-west and essentially vertical), sub-parallel to the
west fault and 70° shear, occurs in the southern
portion of the pit. This system, known as the south
fault, can be considered as an important area of future
exploration due to its apparent southern termination
of the ore and its genetic relationship with other
major systems.

Geological mapping of all fresh faces is conducted
throughout the pit to provide the geological base for
pit planning and slope analysis.

Mine Development
SURFACE DIAMOND DRILLING

An annual program of HQ diamond drilling was in-
itiated in 1971 within the Cassiar pit to provide the
on-going grade and fibre characteristics needed for
mine planning, and to explore the fibre zone currently
beneath the open-pit design limits. Preliminary dia-
mond drilling was attempted on the main orebody in
1951, but was largely unsuccessful due to poor core
recovery. Diamond drilling was also carried out in
1961 and 1963 in the cirque to the north of the orebody
to determine if any fibre-bearing structures followed
the serpentine band. Pit waste dumps are now located

in this area. Total footage drilled to date is nearly
39,000 ft (11,887 m) (Fig. 5).

Diamond drilling at Cassiar presents problems. Some
are unique to serpentine, whereas many are common
to the mining industry. Drilling within the orebody is
attempted on 100-ft (30.5-m) grid centres where pos-
sible. The nature of the serpentine host rock, chrysotile
fibre veinlets and shear zones make core recovery dif-
ficult. However, much success has been achieved since
the initial 1951 drilling using HQ wireline equipment,
with reduction to NQ where necessary. Deviation of
planned hole direction in the serpentine is minimal.

Drilling from the hanging-wall argillites into the
serpentine presents other problems. Due to the domi-
nant hanging-wall bedding, all drill holes deviate to
the north. This has resulted in holes being laid out to
compensate for the expected deviation, which naturally
precludes vertical holes. Down-the-hole methods in the
argillites will be investigated in 1978 to obtain a ver-
tical hole, with coring starting at the serpentine. Drill-
ing in 1978 and subsequent years will be carried out
in the pit to obtain further information for future
mining and from the peak to determine the extent of
the fibre zone at its southern end (Fig. 6). By the
fall of 1980, a final decision must be made on the final
design, which will influence both this and succeeding
designs. Each design has a maximum waste yardage
to be weighed against former ore. However, if by
drilling, the ore is shown to be appreciably reduced
(automatically increasing waste yardage), then the

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