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A long body of augite porphyrite near Bromley glacier and a smaller
mass on upper Bear river were not examined in detail. They resemble,
lithologically, the mass on Glacier creek. A roughly circular body, less
than 100 yards in diameter, of augite porphyrite, on Kate Ryan creek,
intrudes argillite of the Bitter Creek formation. Another small body,
probably less than half a mile in diameter, occurs on the south fork of
Marmot river. It appears to be intrusive into argillites of the Bitter
Creek formation at their contact with Bear River volcanics. The rock is
largely augite porphyrite holding numerous angular blocks, of varying
size, of lavas and breccia.

The augite porphyrite is a dark rock mottled with square, black
phenocrysts of augite + inch or less in diameter. Thin sections of augite
porphyrite exhibit large phenocrysts of augite in a fine-grained ground-
mass. In some sections the groundmass consists of fine needles of feldspar
exhibiting flow structure, and in others it is cryptocrystalline and amygda-
loidal. The feldspars in the sections were too much decomposed for iden-
tification.

An elongated, stock-like body of augite-bearing rock outcrops on
Glacier creek. The rock is mainly a dark-coloured augite syenite con-
taining augite orthoclase, and sodic plagioclase. An associated rock, either
a phase of the syenite or a closely associated but separate intrusive, is a
gabbro consisting essentially of augite and labradorite. Several augite
syenite dykes seen elsewhere in the map-area may belong to the same
period of intrusion as the stock on Glacier creek.

The augite porphyrite and augite syenite bodies are cut by granite
and diorite dykes presumably associated in age and origin with the Coast
Range batholith, but probably older than the batholith itself. No augite-
rich rock was noted intruding the granitic rocks of the map-area. The
augite porphyrite and augite syenite, therefore, are in all probability
much older than the Coast Range intrusives. They resemble in general
appearance certain augite-bearing rocks of the Bear River formation and
it is believed that they are associated in origin with the Bear River vol-
canics and that they were intruded while the volcanics were being
extruded. The smaller bodies of augite porphyrite may be plugs repre-
senting former craters that supplied the volcanic materials for the Bear
River formation. Some of the larger bodies may also be plugs, repre-
senting larger craters where foreign rock types have been engulfed. A
stock of augite porphyrite on Salmon river intrudes the lower part of the
Nass formation,! but as higher horizons of this formation contain vol-
game material, this stock also may be associated with the volcanism of
the area.

COAST RANGE INTRUSIVES

The Coast Range intrusives occupy the southwestern corner of
Stewart map-area and form several small stocks in Bear River and Stewart
map-areas. The contact of the batholith enters the area from the south
at Magee pass and continues northwestward across the two branches of

\Schofield, S. J., and Hanson, G.: Geol. Surv., Canada, Mem. 132 (1922).
$1314—2