General Geology
Faults

In the Hazelton group rocks of Whitesail Lake area, the lack of
distinctive marker beds, the general similarity of the various rock types,
and the discontinuous character of the strata make recognition and extension
of faults difficult. As a result relatively few have been mapped though it is be-
lieved faults are common within the group. Faults were recognized at the head
of Whitesail Lake, on Whitesail Range and Tahtsa Range, on Lindquist Peak,
and at the head of Tesla Lake.

On Core Mountain a distinctive fault is marked by a small stream that
flows from the lake on the mountain top. Rocks in the stream bed are
highly sheared and pyritized. The fault strikes north 40 degrees east almost
parallel with the direction of Whitesail Lake, and the dip of the shearing
is vertical. In part, the north wall of this fault consists of a small gabbro
mass that forms part of the hill. The fault crosses a small red granite body
where it is marked by two narrow ponds, and it may continue southwest
across the head of Whitesail Lake.

The large quartz veins in the Hazelton group rocks on Lindquist Peak
are crossed by a series of north-striking faults that offset the vein as much
as 900 feet in some instances.

On Mount Sweeney the strata are marked by gouge seams between the
beds and are offset by transverse faults across them. The sedimentary beds
towards the west end of Whitesail Range were probably brought to the surface
by faults and the crushed zones near the granite contacts on this range
suggest other faults.

To the south in the vicinity of Tesla Lake faults were observed trending
both parallel with and transverse to the batholithic contact and most of the
topographic features in this region are a result of fault patterns.

The Aluminum Company of Canada’s tunnel driven westward from the
head of Tahtsa Lake ran through several thousand feet of broken ground.
There the volcanic rocks had been intruded by a swarm of small red granite
bodies and dykes. The contacts of each of these bodies were marked by
a seam of gouge, indicating movement. The whole area in this vicinity is
apparently much shattered. Although no major structural faults were
identified the long narrow lakes characteristic of the area are due to fractures
in the main body of Coast Intrusions and adjacent Hazelton rocks. These
lakes accord with the transverse fracture system of the Coast Intrusions and
are probably due to the same structural conditions responsible for the fiords
of the British Columbia coast.

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