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About 6,500 feet stratigraphically above the lowest exposed beds, both
the schists and the quartzites become markedly porphyroblastic, and this
character is maintained throughout almost the entire upper part of the
Tenakihi group section. Garnet is by far the most common porphyroblast
developed in these rocks, and occurs mainly as rough, equidimensional,
rusty brown to reddish grains =; to 4 inch in diameter, being smallest in the
fine-grained schistose quartzites and largest in coarse, crumpled mica
schist. In several places the garnets show good euhedral crystal form, but
all those observed had rough exteriors and contained flakes of sericite or
chlorite. In favourable beds, up to 10 feet thick, garnets were observed to
comprise as much as one-half of the rock volume.

About 600 feet stratigraphically above the lowest level at which garnets
were observed, porphyroblasts of kyanite become abundant. These have a
stratigraphic range of about 3,100 feet, within which they were found to
occur in all beds carefully examined. Porphyroblasts of kyanite were found
to be more plentiful than those of garnet in only a few groups of beds,
rarely more than 50 feet thick. In these beds the kyanite occurs as dark
brown-grey to blue-grey, euhedral prismatic crystals, with very rough
exteriors, up to 3 inches in length. The larger crystals are in many cases
curved, and, although lying in the plane of schistosity, are in general not
oriented in any obvious relation to the regional lineation.

Near the lower part of the stratigraphic interval in which kyanite por-
phyroblasts are conspicuous, brownish prismatic crystals of staurolite are
found in the schistose porphyroblastic biotite-muscovite quartzite. The
staurolite porphyroblasts were not recognized in the field as a mineral dis-
tinct from kyanite, and their relative abundance and stratigraphic distrib-
ution is not exactly known. From their occurrence in the samples collected
it would appear that the staurolite porphyroblasts are mainly less than
4 inch in length, and are much less abundant than the garnet or kyanite
porphyroblasts in the same rocks. Kyanite apparently persists to much
higher stratigraphic levels than does staurolite.

At about the highest stratigraphic level at which kyanite porphyro-
blasts were identified (about 10,000 feet stratigraphically above the base of
the exposed section in the Tenakihi Range), a slightly feldspathic, garnet-
iferous, schistose quartzite contains clusters of epidote up to 4 inch in
diameter.

The uppermost 3,000 feet of the Tenakihi group section exposed in the
Tenakihi Range show a general lessening of grain size compared with strati-
graphically lower beds, and a predominant greenish colour due to the
presence of green biotite and, in places, chlorite.

Rocks in the Chase Mountain Area

In that part of the map-area between Mesilinka River and the middle
and lower reaches of Swannell River, west of Tomias Lake, a stratigraphic
thickness of about 8,000 feet of Tenakihi group rocks is exposed in a large
anticline that extends through the summit of Chase Mountain. The strata
of the southern part of this region have been relatively complexly deformed,
and have suffered more intense metamorphism than most of the Tenakihi
group rocks. Stratigraphic and lithological correlation with the ‘normal’
Tenakihi group is difficult in detail, although an over-all correspondence of