83

also that the Ingenika group rocks have undergone at least one deformation
that has not affected the Takla group strata, and has been independent of,
oriented differently from, and thus, presumably, older than, the deformation
that has produced the present major structures in both groups.

In the southeastern part of the map-area, the contact between the
Ingenika and Cache Creek groups lies in the drift-covered valleys of
Tenakihi Creek, Osilinka River, and possibly the small creek west of the
Beveley group of mineral claims. In each place the rocks of the two
groups strike directly toward each other, and in the lack of any indication
of sharp folding or nosing, the two groups would appear to be most probably
separated by a steeply dipping fault.

METAMORPHISM

MINERALOGICAL AND TEXTURAL CHANGES
General Sequence of Metamorphic Changes

All the Ingenika group rocks have suffered regional metamorphism.
As with the underlying Tenakihi group rocks, the range of metamorphic
grade is relatively uniform over all parts of the map-area where these rocks
are exposed, and in any one area where the stratigraphic sequence within
the group can be established, the grade of metamorphism increases with
successively lower stratigraphic horizons. The increase of metamorphic
grade with stratigraphic depth is entirely conformable with, and a direct
projection of, that observed in the Tenakihi group rocks, and it is at once
apparent that the two groups were metamorphosed together.

The metamorphism of the Ingenika group rocks, with the exception
of those forming part of the Wolverine complex, is all of low grade.
Chlorite, usually accompanied by sericite, is the characteristic metamorphic
mineral of the entire assemblage. The degree of metamorphic recrystalliza-
tion is very slight in the subgreywackes of the uppermost beds exposed in
the Espee Range, where the original texture is essentially unchanged and
the only authigenic minerals are chlorite and sericite, which are probably
a product of diagenetic rather than metamorphic reconstitution. It is
highest in the completely crystalloblastic quartzites and quartz-chlorite-
biotite-garnet schists near the contact with the Tenakihi group rocks. The
Ingenika group rocks present, on the whole, a fairly wide diversity in
chemical and mechanical composition; and thus an increase of temperature,
hydrostatic pressure, and shearing stress have had different effects on
different beds. The metamorphic changes are most pronounced and easily
traced in the finer grained, impure subgreywackes.

The least metamorphosed rocks have, for the most part, a sheared,
slaty texture. The finest grained pelitic varieties consist of a uniform
aggregate of chlorite, sericite, calcite, siliceous material, and indefinite
cloudy clay-like matter. In places the whole has a cataclastic appearance.
Scattered quartz and feldspar grains are completely unaltered, except for
a small amount of replacement by sericite. This fine-grained, partly
mylonitic aggregate forms the matrix of the impure siltstones, quartzites,
and conglomerate, which differ only in the proportion and size of detrital