COUNTRY LYING TO THE WEST OF THE ROCKY MOUNTAIN TRENCH.

GEOLOGY.

A belt of batholiths coincides approximately with the central part of the Cassiar-
Omineca Mountain system. It starts with the batholith exposed to the south of Ger-
mansen Lake. Other areas of batholithic rocks are known to outcrop by Silver Creek
on the Omineca River, at the heads of the Osilinka, Mesilinka, and Ingenika Rivers,
and at Fishing Lake, near the head of Finlay River. The extent of the Cassiar batho-
lith is fairly well known. The eastern contact is mapped from a point close to Sifton
Pass to Cottonwood River (a tributary of Dease River), and the western margin from
the head of Turnagain River to Teslin Lake.

The batholith belt is only partly mapped, but present knowledge suggests that
it is a zone of intrusives of different kinds and ages, that there are outlying satellitic
bodies associated with it, that batholithic rocks are not continuously exposed from one
end of the belt to the other, and that the batholithic rocks contain extensive roof-
pendants of older sedimentary and volcanic rocks.

The intrusive rocks are exposed across widths of 20 to 25 miles. They range in
type from granite through granodiorite and quartz diorite to diorite and minor amounts
of more basic rocks. The granitic intrusives cut both Paleozoic and Mesozoic sedi-
mentary and volcanic rocks. Few, if any, Cretaceous rocks are known, and Tertiary
and later voleanics and sediments are all younger than the batholiths. The batholiths
are considered to be mainly or entirely Mesozoic. The granitic rocks are flanked by a
considerable variety of types. In many places along the eastern margin, from Wol-
verine Mountains to the head of Jennings River, the older.sediments and volcanics are
metamorphosed to slates, and schists and gneisses of various kinds.

EVIDENCE OF MINERALIZATION.

Mineralization found in the Cassiar-Omineca Mountain system is considered to
have accompanied the batholithic intrusions. No lode-gold mines have been developed,
and the number of known mineral occurrences is small in comparison to the size of the
area.

Claims near Uslika and Aiken Lakes have been staked on veins carrying values in
gold, copper, silver, lead, and zine. Of eight properties, all held by the Consolidated
Mining and Smelting Company, the Croydon at Aiken Lake has had the most explora-
tory work done on it.

Farther north, several lead-zine deposits in limestone centre around the Ingenika
mine (Ferguson) on the lower part of the Ingenika River. Gold-bearing quartz veins
are reported in the neighbourhood of Thutade Lake and 6 miles east of Sustut Lake,
and veins have been found by prospectors on Bower and Ruby Creeks at the head of the
Finlay River.

Copper-bearing float has been found at various places along the eastern contact of
the batholith between Sifton Pass and Turnagain River and along the western contact
between Teslin River and Tanzilla River. Gold-bearing quartz veins have been found
on McDame Creek.

Placer-gold deposits result from the preservation of gold concentrated during the
erosion and weathering of gold-bearing rocks. Although gold placers by no means
indicate the existence of high-grade gold-bearing veins, nevertheless they do point to
the existence of gold mineralization in the areas in which the placers are found.

By far the richest gold placers were those on McDame, Dease, and Thibert Creeks.
Other gold-bearing placers have been worked at the following places: Goldpan, Wheaton
(Boulder), and Walker Creeks in the Cassiar; at McConnell Creek near the head of
Ingenika River; at Jimmay Creek; and at Vital, Tom, Germansen, Slate, and Manson
Creeks in the Manson Creek belt; and bar-gold has been found along the Kechika,
Finlay, Mesilinka, Osilinka, and Omineca Rivers.

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