24

Inthology. The sills and dykes vary in composition between diorite,
hornblende diorite, diabase, gabbro, and hornblende gabbro. The dyke
south of Groundhog lake is a hornblende diorite, consisting of idiomorphic
to hypidiomorphic grains of common hornblende, hypidiomorphic to
allotriomorphic plagioclase (near andesine) much felted with secondary
mica, some interstitial quartz and micropegmatite, and small jointed
prisms of apatite. The diorite dyke of the Point hydraulic pit consists of
abundant, short, idiomorphic, rectangular grains of andesine-oligoclase
with prominent albite twinning, common hornblende, and quartz in minor
amount. The sills consist principally of the following mineral groups:
hornblende-oligoclase-andesine, _uralite-andesine, hornblende-plagioclase
(kind undeterminable), diallage-saussurite, augite-labradorite with ophitic
pattern, plagioclase (probably andesine) -augite-chlorite with ophitic
pattern, and augite-andesine-labradorite with ophitic pattern, irregularly
replaced by siderite.

Mapped as Antler Creek 1 Mt. Murray si//s
chert end sro/liite

7

YA

hmestone

Slide Mountain

Aa

Guret
Greerber,

(Ghtmile_ _ _
| Creek
2 ol
conglomerate

Ei

Mount Murray Antler Creek Greenberry Guyet
si//s FOrMmation Formation Formation

Geological Survey, Caneda

Figure 2. Structure section, Slide mountain, showing lit-par-lit injection of Mount Murray
sills into Antler Creek cherts and argillites.

A single sill of quartz porphyry was found on mount Murray, in which
partly resorbed phenocrysts of quartz occur in a very fine grained to glassy
matrix, showing spherulitic structure.

Strange to relate, some of the narrowest sills (less than one foot) are
very coarse-grained and show practically no change in size of grain from
centre to boundary, whereas many of the thick ones are fine-grained and
dense. It is quite probable that some of the denser ones are submarine
flows, which should be correlated with the W averly formation.

Small quartz stringers cross the sills in many places and represent the
filling of small cross-range fissures. No mineralization was observed in
these veinlets.

Metamorphism. Very few of the types are perfectly fresh. The feldspars
are usually felted with secondary mica, much of the augite is uralitized,