Geology of the West Coast of Hudson’s Bay.

Eskimo Point to Chesterfield Inlet.

Marble Island.

Prof. Tennant.

During the past season I have received from a friend a carefully labelled collection of rock-specimens from the north-west coast of Hudson’s Bay, between Eskimo Point and Chesterfield Inlet; and in connection with these a few remarks may be made on the geology of this region. Other specimens from this part of the coast were obtained in 1884 and referred to in my report for that year (page 34 D D.) My own explorations on this coast, beyond Churchill, consist of a boat voyage to a point a short distance north of Button’s Bay, in 1879, and an examination of Marble Island in 1884. The general character of the land about Chesterfield Inlet could be plainly seen from the ship when we were in that vicinity in the latter year. I have, however, received from friends who have travelled in these parts many particulars in reference to this coast. Professor James Tennant, of London, has described some rock-specimens from the north-west side of Hudson’s Bay, and also from Repulse Bay, further north. From these various sources of information some light is thrown on the geology of the coast.

Coast from Seal River to Eskimo Point.

Probable area of limestone.

Between Seal River and Eskimo Point, a distance of about 140 statute miles, the shore-line appears to be uniform with a low country behind it, broken only by an occasional hummock, probably of drift. The shingle of the beach is said to consist largely of limestone, and it is not improbable that behind this section of the coast, there is a considerable area of the flat-lying limestones, similar to those along the lower parts of the Churchill and Nelson Rivers. If this part of the coast were occupied by crystalline rocks, we should probably have a hilly country with a broken coast-line, like that further north, whereas the low appearance of the land and the even trend of the shore are analogous to the conditions which prevail where the Silurian rocks are met with further south on the Bay.

Varieties of rocks.

Veinstones.

Iron pyrites.

Gold and silver.

Pyrites from veins.

Gold in quartz.

From Eskimo Point to the entrance of Chesterfield Inlet, the distance is about 180 statute miles, in a straight line. The rock-specimens from this section embrace fine-grained hornblende-schists, greenstones, quartz and epidote rock, light grey, coarse-grained sandstone, altered to quartzite, and holding fragments of indurated red shale, compact banded white quartz-rock, with crystals of iron pyrites in some of the layers, quartzite like that of Marble Island, grey felsites, crystalline hornblende rock, diorite consisting of compact white felspar with long crystals of dark hornblende, banded grey hornblende and quartz-rock, with some layers approaching chert, mica-schists of different kinds, mixed hornblende- and mica-schist, chocolate-colored porphyry with flesh-colored crystals of felspar and grains of clear quartz, granulite, red jasper with dull fracture, hard, brownish-red sandstone, grey felsitic quartzite with lenticular patches of dark mica-schist, chloritic schist, about fifty pounds of granular iron pyrites, several hundreds of cubes of iron pyrites, the largest measuring about one inch in diameter, taken from a dark, glossy schist, quartz veinstone with large scales of light-colored mica, with garnets, calcspar veinstone with embedded crystals of quartz and having grey steatitic rock adhering to it, also a veinstone of quartz, containing silky radiating aggregates of hornblende and a few specks of calcspar and iron pyrites; some soft greenish schist is attached to this specimen. There are eleven specimens of the granular iron pyrites, which were collected at different points in the above distance. Small pieces of soft dark-greenish schist adhere to some of them. Mr. Hoffmann has made an assay of one of the specimens of pyrites from a bay south of Cape Jones, which forms the southern horn of Rankin Inlet, and found it to contain no copper, but to show traces of gold and 0.175 of an ounce of silver to the ton of 2,000 pounds. A specimen of similar pyrites, obtained from a place on this coast which the Eskimo call Iñari, in 1879, had a small quantity of light bluish-grey magnesian limestone adhering to it. These specimens, which all resemble the pyrites from Tilt Cove in Newfoundland and Capelton in the Eastern Townships, except in the absence of copper, are evidently from good-sized veins. The mineral is in common use among the Eskimo for striking fire. The discovery of traces of gold and silver in the specimen last assayed by Mr. Hoffmann is interesting. Specks of gold are mentioned by Tennant in a specimen of quartz from Repulse Bay.

Huronian series on the N. W. side of Hudson’s Bay.

The majority of the lithological specimens brought from the coast in the whole interval between Eskimo Point and Repulse Bay, correspond with the rocks of the Huronian series. Laurentian types are absent from the collections. So far as we know, therefore, the probabilities are that Huronian rocks prevail all along the north-west coast of Hudson’s Bay, from Eskimo Point to Chesterfield Inlet, and again at Repulse Bay; possibly also, in the interval between the last mentioned localities.

Quartzite of Marble Island.

Quartzite on mainland.

Quartzite in the interior.

Marble Island, as far as examined, consists mainly of light-colored, fine grained quartzite, associated with glossy mica-schists. Among the specimens obtained from the mainland, is one of similar quartzite of a delicate pink or flesh-color, from a point on the south side of Nevil Bay. On Marble Island the average strike is south-westward or in this direction, so that the two localities may occupy the same geological horizon. White quartzite is reported as occurring further south-west in the interior, especially in the region to the north-east of Hatchet or Wollaston Lake, and in my report for 1882, page 28 C C, it was stated that boulders of this rock are abundant at the Long or Methy Portage, still further south-west.