S57

mainly fine-grained to dense, and grcen, grey, red, brovm, or
purple. Due to irregularity in texture, shape, and size of
individual members they are generally fractured and sheared
irregularly and, therefore, the mineral deposits formed in the
fractures and shear zones are ‘commonly irregular and discontinu-
ous. In places, however, unusual stresses or dykes caused the
formation of zones favourable for deposits of greater extent
and regularity. These rocks where sheared or fractured were
favourable for replacement mineralization. The massive
volcanic rocks are by far the most extensive in both Babine and
Bulkley mountains southward from near Porphyry creck.

The other groups, which are younger than most of the
massive rocks but in part are intermediate between them, show
distinct banding due to well-defined bedding. They include
mainly argillites, quartzites, greywackes, conglomerates, and
tuffs with locally some lavas and limestone. Because of their
bedded character they are not so badly fractured as the massive
rocks, but the many well-defined though irregular bedding
planes afforded excellent channels along which mineral deposits
tended to form. Except in the case of the rare limestone
members and included volcanics the rocks were not favourable
for replacement deposits. These rocks are extensively exposed
in the northern parts of the mountain ronges and they continue
south to near Porphyry creek. In the southern parts of the
ranges they commonly occur in relatively small areas and are
probably not very thick. The rocks older than the Skeena form-
ation are commonly designated as the Hazelton group.

The Skeena formation occurs extensively in the low
areas between the mountains. Here it is made up mainly of
nearly flat-lying, soft shales, sandstones, conglomerates, and

bituminous coal. On the east slope of Hudson Bay mountain