sie

east of Nina Lake, and in limestone north of Wolverine Lake.

Altered Diorite

“if The hill north of the settlement of Manson Creek is
underlain by altered, gneissic diorite, and sheared andesite.
Apparently the diorite occurs as sills in the andesite, but

- due to extensive alteration of both rocks they are difficult
to separate. The diorite is a medium-grained, greyish green
rock composed of feldspar, hornblende, chlorite, and biotite.
It is probably related in origin to the andesite, and the
latter is telieved to belong to the Cache Creek group. ~

Peridotite! ana Serpentine

Small lenses of peridotite and serpentine, each less
than a quarter of a square mile in area, are exposed at several
places in the belt of Cache Creek rocks. They have been
hydrothermally altered along shear zones to buff-coloured
‘carbonate-quartz-mariposite. rock. .

Takla, Group

~The Takla group wes named from its abundant
occurrence in the Takla map-area adjoining the Manson Creek
area to the westl. It consists of an apparently conformable

1
Geol. Surv., Canada, Paper Mate OM) iets

succession of interbedded volcanic and lesser sedimentery rocks,
ranging in age from Upper Triassic to Upper Jurassic.
In the Manson Creek map-area formations of the Takla
group comprise more than 5,000 feet of interbedded lava, tuff,
breccia, agglomerate, and minor sedimentary rocks. The lavas
are best exposed in the mountains north and south of Nation
~ Lakes and north of Germansen Lake, and are mainly green, grey,
black, and red, porphyritic and non-porphyritic andesites and
basalts. The porphyritic types contain phenocrysts of feldspar, .
pyroxene, and amphibole. In places amygdaloidal flows were
observed. The amygdules are normally less than a quarter inch
in diameter, and consist of quartz and chlorite. Pillow
structures were also noted in the more basic lavas. Tuffs
predominate north of Omineca River and are thinly bedded,
dense, green and red, andesitic types.

Agglomerate and flow breccia are common in the Takla
group, being most abundant north of Germansen Lake. The
fragments vary from w/i2 inch to 2 feet or more in diameter,
and cansist of red, green, and grey, porphyritic and non-
porphyritic andesite and basalt... In the breccias the
fragments are angular and the matrix is andesitic, whereas

fragments in the agglomerate are sub-rounded to rounded and
lie in a tuffaceous matrix.. RNa i

Bands of grey and black argillite and fine-grained
to dense greywacke up to 100 feet thick are interbedded with
the volcanic rocks. A 50-foot bed of conglomerate, intercalated
with lavas north of Chuchi Lake, is composed of pebbles of red
chert and black argillite in a red arenaceous matrix.