68

buff to reddish brown, and generally coarse grained, with, in exceptional
instances, rhombic crystals up to 6 inches a side. This rock is apparently
developed entirely as a later hydrothermal alteration of the limestone, and
is in many places associated with metallic mineralization.

The remarkable degree of brecciation of some of the limestones has
already been described. Such structures appear to be best developed in
the thick, massive, relatively pure beds. Microscopically, no obvious
difference can be seen between brecciated and unbrecciated material, and
the fragments in the breccia differ from the matrix material only in their
finer crystal size. Coarsely crystalline limestones are best developed in
beds 10 to 50 feet thick intercalated with relatively coarse, clastic, sedi-
mentary strata. One such bed on the west side of Espee Range is a white,
holocrystalline rock composed almost entirely of very clean, unstrained,
untwinned calcite crystals up to 5 mm. long, whose smooth, mutually
rounded outlines contrast sharply with the sutured, interlocking borders of
less coarsely crystalline limestones, and in which the argillaceous impurities
are limited to a few interstitial ‘pockets’ between otherwise clean-fitting
grains.

Stylolitic structures, ranging in size from those with serrations covering
a band 2 inches wide to those visible only in thin section, were noted in
several places, but are not abundant.

Chemical Analyses. Samples of Ingenika group limestones from vari-
ous places in the map-area were analysed by R. J. C. Fabry of the
Mineralogical Division, Geological Survey of Canada, who reported as
follows (a composite analysis of ‘average limestone’ (“A”) is included
for comparison) :

= 23R, 33W 203R | 204R | 389R | 181C | 216C | 221C ATE

CaOre an teste 54-32 | 48-86 | 38-42 | 49-24] 54-82] 50-58 | 52-24] 55-30 42-61
COM eis bsiccsnie ee 41-14 | 39-20] 31-64] 38-78 | 43-14] 41-06] 42-04] 42-66 41-58
MeOigeeseeacannn 0-51 0-34 2-60 0-36 0-21 1-20 1-68 0-20 it
(FeAl)20s.......... 0:77 2-44 3-86 1-08 0-18 0-92 0-80 0-60 1-35

ADS ootposcouoaed 1-58 0-72 1-88 0-68 0-70 1-38 0-88 0-86
Shiite) La qabegetneseoe 2-30 8-50 | 22-34 9-50 0-76 5-16 2°72 OZ50) seer
otal Meneses 100-62 | 100-05 | 100-74 | 99-64] 99-81 | 100-30 | 100-36 | 100-12

23R. Pale purple and buff-grey, fine-grained, crystalline, poorly bedded limestone,
from about the middle of the thick limestone member exposed on the crest
of the ridge north of Osilinka River, east of Tenakihi Creek.

33W. Ivory-buff coloured granular limestone containing abundant oriented flakes of
muscovite up to 1 mm. long. From the east side of Tenakihi Creek Valley,
north of Osilinka River, 400 feet stratigraphically above spec. 23R.

203R. Banded, pale green and silver-buff, sugary, micaceous limestone, containing a
multitude of sericite flakes and a few grains of detrital quartz scattered through
a sheared, medium-grained, recrystallized calcite matrix. From the northeast
side of Swannell River Valley, west of Orion Creek, 1,200 feet stratigraphically
above spec. 204R.

204R. Ivory-buff to rose-yellow crystalline limestone, poorly bedded to slaty, with
very thin sericitic and chloritic partings. From the northeast side of Swannell
River Valley, west of Orion Creek, 400 feet stratigraphically above the top
of the main limestone member, 4,100 feet above the base of the Ingenika group.

389R. Light grey, medium-grained, fairly well-bedded, crystalline limestone contain-
ing beds and streaks of white, slightly more coarsely crystalline, finely bedded
material. From the north end of Butler Range, 3 miles due south of the
summit of Ingenika Cone.