Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Nokleberg, 1996). The serpentinite-hosted asbestos deposits in the Cassiar metallogenic belt are the products of low-grade
metamorphism and alteration of ultramafic rock in the Slide Mountain terranes. The metamorphism and alteration are herein
interpreted as occurring during either Jurassic thrusting of these terranes onto the North American Craton Margin, or more likely,
during younger hydrothermal activity associated with extensive Late Cretaceous granitic magmatism.
- 2000m
Sylvester Basal
Thrust Fault
- 0 200 M
Thrust
South Peak
Sheet
090'
Slide Mountain Terrane
Sylvester Group
Serpentinite
) Limestone
Argillite, chert.
greywacke
j Diorite. gabbro
Volcanic (greenstone)
! Graphitic argillite
North American Continental
Margin
Sandpile Group
Dolomite. limestone
Kechika Group
Argillite
Figure 59. Cassiar (McDame) serpentine-hosted asbestos deposit, Cassiar metallogenic belt, northern British Columbia. Schematic
cross section. Adapted from Burgoyne (1 986).
Francois Lake Metallogenic Belt of
Porphyry Mo Deposits (Belt FL)
Central British Columbia
The Francois Lake metallogenic belt (fig. 49; tables 3,4) (Nokleberg and others, 1997b, 1998) is defined by the
distribution of porphyry Mo deposits in felsic plutons of the Francois Lake Suite (Carter, 1982) which intrude the Stikinia,
Quesnellia and Cache Creek terranes along the eastern part of the Skeena Arch in central British Columbia. The Middle and Late
Jurassic plutons of the Stag Lake (171-163 Ma) and Francois Lake (157-145 Ma) Suites (White and others, 1970; Whalen and
others, 1998), with no identified coeval volcanic rocks, may correlate with the Nelson Plutonic Suite (170-155 Ma) in the
southeastern part of the Canadian Cordillera. Both suites of intrusive rocks are herein interpreted as emplaced during major
accretion and collision of the Stikinia-Quesnellia island arc and associated subduction zone complexes to the west with the North
American Craton Margin.
Endako Porphyry Mo Deposit
The Endako quartz monzonite pluton of the Francois Lake Suite hosts the Endako porphyry Mo deposit, the largest MO
deposit in Canada with initial reserves of 280 million tonnes grading 0.08% Mo. The deposit is essentially a stockwork of quartz -
molybdenite, pyrite and magnetite veins about 350 m wide, which extends for about 3.3 km along a west-northwesterly axis. The
Endako pluton is flanked to the north and south by the younger Casey Alaskite and Francois Granite plutons, respectively.
Potassic and phyllic assemblages envelope quartz-molybdenite and other vein assemblages, and the host rocks are pervasively
kaolinized (Dawson and Kimura, 1972; Dawson and others, 1991; Bysouth and Wong, 1995). Similar, but smaller, Mo deposits
occur at Nithi Mountain, Owl Lake and to the north and northwest of Endako deposit (Dawson, 1972).
Fault