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GENERAL GEOLOGY

Upper Quinsam lake lies in an area of disturbed and variously altered
sediments and volcanics penetrated by large and small masses of granitic
rocks. The sediments and volcanics, so far as known, are mainly perhaps
almost entirely of Triassic age. The plutonics are of late Jurassic or,
possibly, early Cretaceous age. All are older than the coal-bearing Upper
Cretaceous sediments of the east coast of Vancouver island. The pre-
plutonic rocks are largely of volcanic rocks both intrusive and extrusive,
but with them occur clastic and limestone strata which in places have a
very considerable thickness and are developed over considerable areas.

In the neighbourhood of Upper Quinsam lake and forsome distance north-
wards granodiorite and granite are the prevailing rocks. In the vicinity
of Iron hill, granodiorite outcrops on the lower slopes of the ridge, which is
nearly 1 mile long. The summit of the ridge is mainly occupied by dark
voleanic rocks which vary in grain from very fine to medium and in places
are porphyritic, amygdaloidal, or agglomeratic. They are presumably a series
of lavas and intrusive bodies. Their general attitude was not determined.
Dark, basic dykes cut them and occasional pale-coloured dykes from
the granodiorite mass are also present. At the northeast end of the flat
top of the ridge, pale grey, nearly white, very pure crystalline limestone
outcrops over an area 1,100 feet long by 400 feet wide. The limestone
in places is faintly banded white and grey, but no distinct evidence of
bedding was noted. It overlies the finely granular, basic, voleanic rocks
and the course followed by its lower boundary, considered with reference
to the topography, indicates that the mass of limestone, though affected
by minor undulations, dips northeasterly at angles of 10 to 20 degrees
or less. The patch of limestone is presumably a remnant of a very con-
siderable bed and has been preserved as a result of the development of a
body of magnetite-bearing garnetite along the contact between the lime-
stone and the underlying volcanic rocks. The resistant magnetite-
garnetite outcrops as a border to the limestone mass.

DESCRIPTION OF THE ORE OCCURRENCES

The main occurrence is a series of outcrops of magnetite and garnetite
in varying proportions, which form a nearly completely exposed annular
zone enclosing the area of crystalline limestone and surrounded by the
dark, fine-grained voleanic rocks. The limestone and the encircling
zone of magnetite and garnetite form an elliptical area whose major
axis trends nearly due east and has a length of 1,300 feet, and whose
minor axis measures 600 feet. The elliptical area contains about 12 acres,
of which somewhat more than one-half is underlain by magnetite and
garnetite. The area of limestone and ore lies at the north end of a narrow,
comparatively flat-topped ridge which trends southwesterly. The out-
crops are mainly on the summit, but are in part on the upper north slope.
The limestone, the magnetite-garnetite, and the surrounding voleanie
rocks are well exposed over the summit of the ridge, but are poorly exposed
on the north slope where large areas are wholly drift covered. The inner
boundary of the magnetite-garnetite, against the limestone, is well defined,
but the outer limit is drift covered except along the south margin. On
any part of the annular zone of magnetite-garnetite, the immediately
adjacent outcrops of limestone are above, and the voleanic rocks are