22

zine minerals from the same source, the four copper-bearing areas may
be continued underground in a roughly horizontal copper-bearing zone,
over which and around the side of which gradations exist to a zone char-
acterized by the presence of silver-lead-zine deposits.

The grouping discussed above refers to the segregation of all the
copper-bearing deposits into a few small localities in the map-area. The
only grouping noted in connexion with the silver-lead-zine deposits refers
merely to a greater number of deposits in certain localities than in others.
The explanation of this is not so obscure as in the core of the copper
deposits and is indeed usually self evident. On the south fork of Marmot
river, silver-lead-zine deposits form a fringe to the batholithic contact.
Most of them lie in a belt of argillite that is in contact with, and dips
away from, the batholith. It is likely that the argillite did not fracture
readily enough to permit any but the strongest fractures to pass through
the formation. The ore deposits occupying the fractures would then be
mostly close to the batholith and in the argillite. Another group or line
of deposits crosses the lower part of Glacier creek. These deposits are
located along a strong fissure zone known as the Portland Canal fissure
zone. ‘The veins were deposited along the many planes of weakness within
the fissure zone.

STRUCTURAL RELATIONS

The mineral deposits of the map-area do not appear to exhibit any
marked relationship to geological structure except in two small areas. It
seems that in general they were deposited in all available open spaces
regardless of structure. Geological structure may, however, have affected
the formation and location of some of the mineral deposits in Marmot
River valley and in the Portland Canal fissure zone. In Marmot River
valley as already stated, a band of argillite lies in contact with, and dips
away from, the batholith. Differential movement in an argillite forma-
tion does not as a rule result in large, open fractures. The argillite on
Marmot river was apparently not greatly fractured and ore solutions from
the batholith could not, as a rule, penetrate the argillite. It is probable
that had the dip of the argillite been toward the batholith, the bedding
planes of the argillite would have served as channel ways for ore solution
with the result that mineral deposits would have been present over a
larger area. Marmot River area, thus, seems to present an example of
how geological structure may control mineralization in this case with
unfavourable results. On the other hand, in the Portland Canal fissure
zone, argillites dip westward, probably toward the source of the mineral
deposits. The rocks are sheared, fissured, and faulted along planes that
dip west also and in many places coincide with bedding planes. Zones of
shearing, fissuring, and faulting, and the bedding planes, dip towards the
source of mineralization, and mineralization is comparatively widespread.
Had the dips of the strata, shear planes, fissures, and faults been east-
ward, mineral deposits would probably have been relatively scarce.