8

An andesine diorite porphyry dyke 12 feet wide, on the Grotto group,
has a gold-quartz vein along one side. Nearby is a small tongue of andesine
quartz diorite. Small dykes of albite quartz diorite occur about 1,000 feet
farther west. A 6-foot dyke of the andesine diorite porphyry occurs in the
workings on the Toulon group. An oligoclase diorite porphyry dyke on
the Diorite property is intrusive into a mineralized quartz-albite dyke.
On the Singlehurst claim an 8-foot dyke of andesine diorite was intruded
and faulted prior to vein formation. A thick sill of oligoclase diorite
porphyry on the Windfall claims outcrops about 200 feet above the mineral
deposit, and an altered, fine-grained quartz diorite sill on the Patmore
property contains small vein deposits. A granodiorite dyke on the Fiddler
group seems to have played a part in damming vein solutions, thereby
causing the widest part of the Fiddler vein to form nearest the dyke.

Quartz-albite dykes composed of about equal proportions of fine-
grained quartz and albite, in some places micrographically intergrown and
containing a little sericite are numerous in the area from Thornhill moun-
tain north to Legate creek. These dykes are of economic interest as many
of them have quartz veins along their walls, as on the Dardanelle and St.
Paul properties. Vein deposits associated with these dykes were seen
during the 1936 season on the Zona May, Diorite, Silver Mitts, Galena,
Frisco, and Bornite King properties. On the Zona May claim the quartz-
albite dyke is altered and cut by a younger lamprophyre dyke. Where
coarsely crystalline these quartz-albite dykes are sometimes referred to as
alaskite dykes.

PLEISTOCENE AND RECENT

Boulder clay and glacial erratics are seen along the valleys of the
tributary streams. Recent morainal gravel deposits occur at the base of
all the alpine glaciers. Skeena River valley is floored with thick gravel
deposits, and recent gravel deposits are continually forming at the mouths
of the tributary streams during flood periods. A marl deposit occurs on a
wide gravel bench at Ritchie, 1 mile west of the river and 100 feet above
present high-water mark. Between Cedarvale and Woodcock a second marl
deposit occurs on an upper gravel bench one mile west of the Skeena, at an
elevation of 1,000 feet or 500 feet above high-water mark. This bench may
have formed during the wane of the glacial period when the Skeena valley
was ice filled. An elevated rim 10 fect high along the outer edge of this
upper gravel bench suggests the presence of ice during its formation.

Most of the mountain slopes have a shallow drift cover, but where
steep ground is encountered prospecting is hindered by extensive rock talus
slides. Rock exposures are abundant above timber-line.

ECONOMIC GEOLOGY
HISTORY OF MINING ACTIVITY

Placer gold deposits on Lorne, Chimdemash, Fiddler, and Kleanza
creeks were worked as early as 1884. Chimdemash and Fiddler creeks
were worked for only a short time, but individual operators still carry on
small-scale sluicing operations on Lorne and Kleanza creeks. Large-scale