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change right up to the sharp contact. Undoubtedly, one of the factors
that account for the general lack of contact metamorphism is the pre-
dominantly volcanic nature of the Takla group, with an over-all chemical
composition relatively similar to, though probably less siliceous than, that
of the average intrusive rock.

The detailed contact relations of the Hogem batholith are described
elsewhere in this report (See page 181). The most significant change noted
in the Takla group andesites near the contact has been a recrystallization
of the rock within 50 feet of the contact. This phenomenon is well
illustrated on the ridge east of the east fork of Matetlo Creek, where the
andesite, still retaining its normal porphyritic texture, has a slightly
denser appearance in the hand specimen. In thin section this rock is seen
to have a well-developed crystalloblastic texture of rounded grains with
sutured interlocking contacts. About 60 per cent of this rock is fresh-
looking hornblende, pleochroic olive-green to green-brown, in poikilitic
grains up to 2 mm. in diameter. These grains are commonly clustered in
masses, up to 5 mm. long, with more or less equidimensional outlines,
which have the appearance of altered pyroxene phenocrysts. Approxi-
mately 30 per cent of this rock is feldspar, present in two distinct varieties:
(1) much altered, subhedral grains largely replaced by sericite and epidote,
rarely showing good twinning but almost invariably zoned; and (2) fresh-
appearing, polysynthetically twinned, unzoned, poikilitic, but free of fine
cloudy alteration products and minute inclusions. In addition, the rock
contains considerably more magnetite than the average andesite of the
area. In this case the contact metamorphism seems to have consisted of
the alteration of an original pyroxene andesite through uralitization of the
pyroxene, producing hornblende and magnetite, and through clearing the
feldspar by absorption of the sericite and epidote developed in previous
(diagenetic ?) incipient alteration, accompanied by a partial re-combina-
tion of the albitic feldspar and epidote, previously developed by saussuriti-
zation, to form new albite-oligoclase. The contact metamorphism observed
east of Matetlo Creek has been just sufficient to reorganize the rock
material into a rock with poikilitic crystalloblastic texture. This appears
to be a straightforward instance of thermal metamorphism of a relatively
basic rock.

The impure calcareous tuffs west of Kliyul Creek have undergone a
distinctive contact metamorphism against the intrusive bodies. The normal
rock, to within about 300 feet of the contact, is a grey-green, bedded tuff
containing up to 30 per cent granular calcite, which appears to be part
of the original groundmass of the tuff, distinct from the shreds and irregular
patches of carbonate developed during later alteration. Adjacent to the
contact, no change of colour is apparent, but the rock becomes harder,
with a slightly more granular texture. In thin section, the rock at the
contact is seen to consist almost entirely of calcite, garnet, and epidote.
The bedding is well preserved, outlined in the contact metamorphosed
rock by segregated bands of different mineral composition. Some bands
consist primarily of anhedral, semi-equidimensional grains of calcite up to
0-1 mm. in diameter, with minor quartz and much epidote and clinozoisite
in very minute, rounded grains. Other bands contain up to 80 per cent
garnet, in ragged elongate masses up to 2 by 4 mm., crowded with small,
rounded inclusions of calcite and epidote or clinozoisite. The masses of

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