157

Sarita river. He submits no descriptions of these deposits, but outlines
in a general way his ideas of their genesis and relationship to the country
rocks, as follows.

_ “In the southern part of Vancouver island the largest bodies of magne-
tite occur in the Nitinat limestones. . . . The deposits of the Nitinat
formation occur in the contact metamorphosed limestones at the contacts
with plutonic rocks, diorite always being the contacting phase of the
eruptive bodies. . . .

The metallic minerals occur usually in closest association with the
sheared, contact metamorphosed limestone, in which are occasional lenses
of residual marble. . . . The marble has been metamorphosed in
places to a typical ‘‘contact rock” . . . . composed essentially of
massive brown garnet and small grains of green diopside ze

The intrusive plutonic rocks are the Saanich granodiorite and the
Beale diorite. . . . The diorite in the vicinity of the deposits is as a
rule richer in hornblende. . . . Near the contact the diorite passes
into hornblende-rich phases, fine-grained, and sometimes porphyritic in
texture. . . . As the occurrence of the magnetite bodies is restricted
to the contacts of the marble and the intrusive plutonic rocks, there can
be little question that they owe their origin to the contact action of the
plutonic rocks on the marble. . . .

The magnetite deposits of the Nitinat formation not only owe their
origin to the intrusion of the plutonic rocks, but, since it seems as if the
original limestones were pure, the minerals of the deposit have apparently
been derived from the intruding batholith. After the limestones had
been more or less contact metamorphosed, as inclusions of silicates occur
in the magnetite, solutions of magnetite, with small amounts of sulphides,
penetrated the contact zone, and replaced it in part. The solutions were
apparently very concentrated, virtually magnetite magma, since they
intruded and brecciated the sheared diorite and unaltered marbles in
much the same manner as rock magma intrudes and brecciates.’”!

The above quotation from Clapp is included since it presents the
earliest clean-cut explanation of the occurrence and genesis of these magne-
tite deposits and because of its advocacy of the ore injection hypothesis.
The detailed data of occurrence recited under the subsequent descriptions
of the individual deposits give the criteria by which this hypothesis of
Clapp may be tested.

In 1913 Cooke (23, 24) made a detailed geological study of Sooke
peninsula, and his reports contain brief descriptions of the magnetite
deposits there.

The last published personal investigation of these West Coast iron
deposits was made by Brewer in 1916 for the British Columbia Department
of Mines (21). He gives a brief review of the history of iron ore explora-
tion and mining on the west coast, a map of Vancouver island showing the
locations of the principal properties, a description of each deposit visited
with the extent of development work accomplished, and an estimate of
actual, probable, and possible ore. Brewer does not include maps of the
various deposits, nor does he state the mathematical basis upon which he
estimates tonnages. It is interesting to note in passing the following
quantities which he reports (for West Coast deposits alone): actual ore,
470,000 tons; probable ore, 1,060,000 tons; possible ore, 3,417,000 tons.

1 Ibid, pp. 189-193.
17135—11}