TAKU RIVER AREA. d1

The Coast Range granodiorite batholithic rocks constitute the bulk of the lower area of
Taku river, from its mouth to within 5 miles west of the International boundary-line. There
the contact crosses the river, striking in a northerly direction, and apparently follows this
course about 6 miles west of the Tulsequah river. The rocks east of the contact consist mainly
of the older igneous groups, probably Triassic or Jurassic, with some limestone and altered
sedimentaries. This series is intruded by younger rhyolite, dacite, and felsite dykes and siils,
which in turn are intruded by basic rocks of lamprophyre type.

The igneous rocks of the Tulsequah area are much altered and difficult to identify in the
field. They are generally fine-grained and compact, heavily silicified, and in places characterized
by widespread development of epidote and other products of alteration. They appear, however, to
be of andesitic type. Associated with these are fine-grained interbedded tuffs of light-grey
eolour. Although a definite brecciated structure was noted in some of the volcanics, they are
generally of dense texture and no large areas of coarse fragmentaries were noted. A belt of
micaceous schists occurs on the west bank of the Tulsequah, as a probable resultant of meta-
morphosed sediments.

Argillites and slates are reported by prospectors to oceur towards the head of the Tulsequah
river. Flanking the east and west sides of Tulsequah glacier, two deep-red coloured mountains
of about 5,000 feet altitude, surrounded by the general grey igneous and volcanic rocks of the
area, are prominent features of the landscape. This red coloration may have resulted from the
oxidation of pyritized argillites; it is, however, significant of a mineralized area and would be
well worth prospecting. Up to the time of examination few prospectors had penetrated that
distance up the river, and although several attempts had been made, none were met who had
actually examined the rocks of this region. Several other zones, heavily discoloured by iron
oxides, can be observed in the higher altitudes. These are all well worth immediate prospecting.

Folding and evidence of acute stress is observed near the contact west of the International
boundary. Basterly this condition is gradually minimized, and the structure, well defined in
certain localities, assumes the more stable and definite character that would be conducive to the
confined circulation of mineralizing solutions and the deposition of sustained ore-bodies. No
evidence of acute regional folding was observed in the area adjacent to the Tulsequah river.
Major fracturing, accompanied in places by well-defined shearing, has occurred along both a
north-easterly and a north-westerly direction.

“Mieht” areas are observed in some localities, but adjacent to these are generally areas of
well-defined structure. This condition, if due to differences in the rock texture and association,
would have a minimizing effect on the regional dispersal of circulating mineral-bearing solutions
and would tend to confine structural stresses to certain definite directions. A confined zonal
circulation of mineral solutions should result from such a condition, and it is consequently
indicative of sustained ore-bodies of good width where conditions for mineral precipitation have
been favourable. Prospecting, if intensified in these structurally fayourable localities in this
area, should result in the discovery of important ore-bodies.

ECONOMIC GEOLOGY.

The region embraces a section of the eastern contact margin of the Coast Range batholith.
Within this there are areas of favourable structure. These are prime factors in the deposition
of ore-bodies of economic importance. The discoveries already made and the structural eondi-
tions affecting the area indicate the probable occurrence of appreciable potential tonnage ore-
bodies. These factors, coupled with the already known mineralization, do not promise excep-
tionally high-grade ore-bodies with restricted widths, nor bonanza values in the precious metals.
Isolated occurrences of high-grade silver ores will doubtless be discovered, but these cannot be
expected to be a general characteristic of the region.

A low to medium grade general tenor of the ore-bodies with an essentially base-metal
mineralization can be expected. This is a factor, however, that tends towards a healthy and
prosperous industrial condition. Appreciable base-metal production calls for populous com-
munities, metallurgical expansion, establishment of both foreign and home markets, and, most
important of all, the necessary establishment of industries for the manufacture of finished
articles for consumption by these markets. The economic influence of a possible appreciable
base-metal production from the Taku River area on the industrial future of British Columbia’s

coastal area is of great importance.