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most part these bodies are relatively fresh, uniformly coarse grained, slightly
gneissic, light grey rocks, the grain size of most specimens averaging from
2 to 5 mm.; a few rocks are composed chiefly of grains about 8 mm. in
diameter. Thin sections of representative specimens show the rock to con-
tain about 30 per cent quartz; 45 per cent oligoclase-andesine (An,5-35),
commonly twinned and zoned; 0 to 20 per cent potash feldspar, mainly
microcline, but some sections show many grains of orthoclase; and
up to 10 per cent dark minerals, mainly biotite or, occasionally, hornblende.
Accessory minerals are magnetite, sphene, and apatite. No systematic
difference in composition or texture between the centre and borders of the
various bodies could be discerned.

The granodiorite bodies have relatively smooth, sharp contacts against
the schist they intrude, and in general have the shape of steep-walled stocks,
fairly regular in plan outline, with irregular but relatively flat roofs. The
prominent southwest shoulder of the massif northeast of Blackpine Lake
appears to consist of a relatively thin roof or capping of gneiss, much
intruded by pegmatite, resting on the granodiorite, which is exposed on
three sides almost up to the top of the shoulder. In the entire, excellently
exposed upper contact of the largest body northeast of Blackpine Lake,
which was examined in detail, no apophyses of granodiorite into the gneiss
were found. In many places the contact between the granodiorite body
and the gneiss is occupied by a quartz-feldspar-muscovite pegmatite dyke,
which shows intrusive or replacement relations against both rocks. Else-
where, the contact is invariably sharp, but not everywhere knife-edged; in
places the distinctive layers of strongly banded gneiss lose their individual-
ity and give way to uniform granodiorite within about half a centimetre.
No difference could be noted between the granodiorite truncating bands of
amphibolite and that intruding quartz-mica-feldspar gneiss; and the folia-
tion of the granodiorite is not oriented in any apparent relation to the
bedding foliation of the schist, gneiss, and migmatite. Inclusions of gneiss
within the granodiorite appear to be lacking, with the possible exception
of a few relatively large bodies near the margins of the stocks, which could
be interpreted as roof pendants.

The foliation of the larger granodiorite body northeast of Black-
pine Lake is in most places inconspicuous, and is not uniformly developed;
many exposures appear massive. In general the planes of foliation are
relatively flat-lying, though quite variable, near the roof, and somewhat
more steeply dipping at levels 3,000 feet lower. In plan, the foliation
appears to form broad sweeping curves that roughly parallel the face
of the rounded mountain spur on which the rock is exposed, and curve
into the mountain at the east and north contacts. The contact relations
suggest that the granodiorite body is a more or less regular dome-shaped
body, of which somewhat more than half the upper part is exposed, and
which is nowhere deeply eroded. Within the dome the planes of foliation
appear to be crudely concentric, forming shells roughly paralleling the
contact.

Leucogranite

A medium-grained, light brown, granitic rock occurs as numerous
sills, dykes, and irregular bodies in the feldspathic quartzites and quartz-
mica-feldspar gneisses between Blackpine Lake and the headwaters of