Thesé serpentinized rocks aro commonly traversed by
numerous shearing planes along which light groon serpentine has

been developed. Between the shearing planes the rock is broken and
rounded into ollipsoidal fragments, = inch to 3 feet in diameter,
each cllipsoid consisting of dark green serpentine free from
shearing. This feature is best scon on the weathered surfaccs.e

In the area lying botween Trembleur Lake and Mount
Williams about 10 per cont of the serpentinized peridotites have
been altered to carbonate-quartz-mariposite, and carbonate-tale rocks.
These altered rocks occur in fractured zones ranging in width from
10 to 500 fect, separated by zones of wmaltored serpentinized peori-
dotites of approximately the samo width. The largest quantity of
such rocks was observed alorg Mount Williams ridge whore they were
traccd for more than 2 miles,

The carbonate-quartz=mariposite rocks are buff to yellow-
browm, and medium to coarsely crystalline. They are composed of
buff-coloured ankeritic carbonate, quartz, and the bright green
chrome=bearing mica mariposite, crroncously thought by many of the
prospectors in the region to be a copper mineral. These rocks are
intersected by a network of quartz stringers.

The carbonate-tale rocks are less abundant than the
carbonate-quartz=emariposite rocks, They have a groasy feeling, are
grconish buff in colour, and are composed of 40 per cont ankcrite
carbonate, and the romaining 60 per cent of tale. The high por cent
of tale imparts to them a dense appearance. Both types of altered
rocks contain specks of pyrite and chalcopyrite.

The gabbros and diabase are mcedium-to coarsce-graincd,
dark greon rocks consisting essentially of pyroxens (dinllage) and
a basic plazioeclase feldspar. Tho pyroxene is usually partly altered

to hornblende, and the feldspar to zoisite and sausserite.

The amphibolites are dense to fine-grained, pistachio to
dark green rocks composed of hornblende, epidote, and sausscrite.
They normally have a crude foliation.

rocks, In the Middle River Range the basic intrusives are cut by a
pody of granite, and south of Stuart Lake they are cut by stocks of
augite diorite, and syenite. In no place wore the basic intrusives
seen to cut the Mesozoic (?) acid intrusives or younger rocks.

The Mesozoic (7?) basic intrusives intruce the Carboniferous