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Quartz diorite porphyrite and finer-grained dacite and fragmental
rocks of similar composition occur at the north end of Hastings arm and
at some places in the Georgia River body. The quartz diorite porphyrite
contains quartz, orthoclase, andesine, much biotite, and some hornblende
and apatite. Except for its coarser grain and holocrystalline nature it is
similar to some andesites of Bear and Salmon River districts.

The feldspar porphyry at the Premier mine is grey, and though locally
it is decidedly porphyritic it is for the most part not noticeably porphyritie.
The phenocrysts are orthoclase and quartz. The groundmass has been
greatly altered in general to sericite, calcite, chlorite, and pyrite. Apatite
is a common accessory mineral. Some facies of the rock, as at the Wood-
bine mine, contain phenocrysts of quartz instead of orthoclase, but the
rock is otherwise the same. Some purplish or reddish porphyritic rocks
north of Premier mine contain quartz and feldspar phenocrysts, consider-
able red iron oxide, and also much epidote. Except for the epidote and
iron oxide the rock resembles the Premier porphyry. These rocks, also,
except for their coarser grain, are very like the felsites of Alice Arm district.

Somewhat similar intrusives at Summit lake contain many pheno-
crysts of hornblende. Commonly the feldspars have been too greatly
altered for identification, but in no case was the plagioclase found to be
as basic as andesine.

A small, elongated stock of augite syenite occurs in Alice Arm district
and another of the same rock also occurs in Bear River district. They
may be closely allied to the augite porphyrite of the area.

It appears that in Portland Canal area east of Georgia river most of
the intrusive types are alike in that the feldspars are more acid than
andesine. At Georgia river intermediate types occur and at Anyox, still
farther west, gabbros are typical.

STRUCTURE OF HAZELTON GROUP

Kast of Alice Arm district the sediments dip east. Minor folds occur
along Illiance river, but as far west as LeRoy mountain the rocks either
dip east or are nearly horizontal. At the head of Kitsault river minor
folds are displayed. From this river westward the prevailing dips are to
the west. The major structure and one that embraces the whole district,
therefore, appears to be a northerly striking anticline. The east limb is
clearly defined, but the western limb is plicated and broken by faults.
The broad arch narrows to half its width at the north end of the district
and has not been traced south of the district. In Anyox district the rocks
have a clearly defined northerly trend. The sediments are severely folded
and locally overturned, but no general structure has been made out.
Apparently the folds are closely spaced and of minor size.

The Cambria snowfield prevents the tracing northward of the features
of Alice Arm district, but west of Salmon glacier and west of Summit lake
the sediments over an area of more than 20 square miles dip west and it
would appear that there too the broad anticline is present. In Bear River
district the anticline is fairly clearly marked but is complicated by numerous
folds and later intrusions. In Salmon River district and farther north the
rocks lie in several southerly trending folds. There is an anticline in Long