McDAME

GLACIAL DRIFT,
TALUS , DUMPS

“| SANDPILE

CASSIAR
4 INTRUSIONS KECHIKA
McDAME UPPER
SERPENTINITES : ATAN

SYLVESTER < LOWER
ARGILLITES NY S ATAN

UPPER
GOOD HOPE

SYLVESTER
VOLCANICS.

UPPER
McDAME

LOWER
GOOD HOPE

FIGURE 2— Plan of local geology.

McDame syncline near the base of the Sylvester Group
(Fig. 2). The orebody strikes approximately north-
south, with a dip of 30-45 degrees to the east. Approxi-
mate present surface dimensions are 700 ft (213 m)
by 1500 ft (457 m). The northern limit has been par-
tially eroded by glacial action, leaving a large cirque
filled with serpentine and argillaceous talus and
debris. The host body consists of blocky, locally slick-
ensided, light to dark green serpentine containing
numerous veinlets of chrysotile asbestos (Fig. 3). In
some areas of lesser serpentinization, bastites of ser-
pentine pseudomorphous after rhombic orthopyroxene
are evident. Magnetite is fairly abundant, occurring
in microscopic veinlets and larger veins throughout
the serpentine. Disseminated magnetite is conspicu-

~ ously absent. Other minerals associated with the ser-

pentine emplacement include: picrolite, magnesite,
nemalite, brucite, tremolite and antigorite.

Locally, the Sylvester rocks comprise argillite,
argillaceous quartzite, volcanics (greenstones) and
graphitic schist. The contact between these rocks and
the serpentine is conspicuously marked on the foot-
wall by a zone of broken and incompetent argillite
and graphitic schists. In general, the footwall argillites
are grey-brown to black, fine grained and graphitic.

Wall-building characteristics are poor, and this has
resulted in an inter-ramp footwall slope design at
37 degrees. On the hanging wall, the contact is much
less conspicuous and consists of a zone of indurated
argillite locally referred to as the “alteration zone”.
This zone is composed of a zoisite-quartz-tremolite
hornfels with local irregular bodies of nephrite jade

ey es