Hudson Bay and Hudson Strait.

The territory comprised in this group includes the islands of Southampton, Coats, Nottingham, Salisbury, Charles and Resolution, along with the shores of the northwest part of Hudson bay, and the south shore of Hudson strait.

The geological information concerning this group obtained prior to the present voyage is contained in the reports of Dr. Bell, Tyrrell and the writer.

Crystalline gneisses, schists and granites occupy the eastern and northern parts of Southampton, extending northward from Seahorse point to Frozen strait at the northern end of the island. The rocks near the junction of the ArchÆan with the Silurian at Seahorse point are largely a very quartzose, light-gray mica-gneiss, associated with bands of rusty-weathering, fine-grained mica-gneiss holding graphite in small flakes, the rusty colour being due to the decomposition of small grains of pyrite disseminated through the rock. This rusty gneiss closely resembles that found in the vicinity of Cape Wolstenholme at the entrance to Hudson strait, and both appear to be similar to the sillimanite gneiss of the Grenville series of southern Canada. Both of the above rocks are cut and twisted by masses of a coarser granite-gneiss pink to red in colour, with pearly feldspar and smoky quartz. All are cut by dikes of feldspathic pegmatite containing much of the pearly feldspar.

The only notes relating to the ArchÆan area to the north of Seahorse point are those of Parry and Back, both of whom mention the occurrence of granites and crystalline rocks in several places to the northward.

The band of ArchÆan rocks which crosses the eastern part of Coats island has never been examined closely, and our knowledge of it is confined to observations made from the ship in passing.

The high rocky shores of the eastern and northern sides of Salisbury island were closely followed by the Neptune, so that the red, crystalline rocks forming its cliffs could easily be seen. The prevailing rock was red, or pink, and only occasionally were darker masses seen.

Nottingham, which lies south of Salisbury in the western part of Hudson strait, was visited by Dr. Bell in 1884 and 1885, when he examined the rocks in the neighbourhood of Port De Boucherville, in its southeast part, and he there found along with the common varieties of gneiss a number of patches of fine-grained red syenite.

Charles island is wholly formed of ArchÆan gneisses. The prevailing rock in the western part is a fine-grained light-gray, or pink mica-gneiss, associated with medium to coarse-grained mica-hornblende granite-gneiss; the latter cutting and altering the light-coloured gneisses.

Resolution island has never been visited by a geologist, and consequently its rocks can only be described from observations made while passing it in the ships. The rocks everywhere appear to be crystalline ArchÆan, a red variety predominating.

The southern shores of Hudson strait from Douglas harbour to the mouth of George river in the southeast part of Ungava bay were examined by the writer in 1897, and a detailed statement concerning them is given in the report of that year. The remaining portions of this side of Hudson strait were examined on the voyage of the Neptune, the part westward from Douglas harbour to Cape Wolstenholme while sketching the coast-line from the ship, and the greater part of that between Cape Chidley and the mouth of George river by Mr. Caldwell in a boat during the absence of the Neptune to the north in 1904. These examinations connect with the work of the writer beyond Cape Wolstenholme, and thus practically finish the examination of the north and west sides of the Labrador peninsula.

The rocks of the south coast of the strait westward from Cape Chidley, as examined by Mr. Caldwell, show that large masses of red and pink mica and mica-hornblende-granite, in a more or less foliated condition, occupy the greater part of the coast area. These granites are newer than the other crystalline rocks associated with them, which they have inclosed and altered. The older rocks are largely of basic igneous origin, and vary in composition from anorthosites almost free from bisilicates, to hornblendic and chloritic schists containing very little feldspar. A series of light-coloured, high quartzose gneisses is also found, and probably represents altered bedded rocks associated with the basic igneous ones.

The basic rocks and the light-coloured gneisses are penetrated by many large dikes of pegmatite from the granites. In many places these dikes are very quartzose, and where they cut the basic masses often contain pyrite and give indications of other minerals. Associated with the lighter gneisses are large long masses of rock, which carry in places considerable quantities of graphite, in others an impure iron ore. The study of these bands has not been sufficient to pronounce as to whether they are veins or beds.

Ancient crystalline rocks occupy the entire coast-line from the mouth of George river at Ungava bay to Cape Wolstenholme at the eastern entrance to the strait. Mica-granite and, in less quantities, mica-hornblende granite, both more or less foliated, occur along the greater length of this coast. In many places these granites are associated with other gneisses, which are usually lighter in colour, finer in texture, and contain more quartz than the eruptive granite. These lighter gneisses usually are garnet-bearing, the crystals of that mineral being often of large size. In a greater number of places the gneisses of these two series are so closely mingled as to render a separation impossible; but there are localities, notably along the west side of Ungava bay, where such a separation can be made, and the lighter coloured gneisses are seen to be cut and foliated by the intrusion of the coarser and garnet-free granite-gneisses. At the mouth of Payne river and about the mouth of Hopes Advance bay the change from unaltered clastic rocks to the light-coloured gneisses is plainly seen in a number of places. The unaltered series consists of impure dolomites, sandstones, cherts and bedded iron ores similar to the series of rocks found in the central parts of Labrador and along the east coast of Hudson bay. This series bears a close resemblance to the iron-bearing rocks of Lake Superior, and there is little doubt that they are of the same age. In former reports they have been termed so-called Cambrian, but by the new classification they represent one or more members of the Huronian. These rocks are associated, as elsewhere, with great outbursts of basic igneous matter in the form of sills, dikes and irregular masses. Where the newer granites have cut and inclosed masses of this series, the different rocks forming it are seen to have undergone considerable alteration. The bedding has been disturbed, so that the strata lie at angles approaching the vertical, and have been broken, and minutely penetrated by quartzose injections, both along and across the bedding planes. Foliation and schistosity have been induced, and the arrangement of the chemical constituents has been altered so that new minerals are formed. The impure cherty limestone is changed to hornblendic schists, the impure sandstone and quartzite to garnet-bearing quartzose gneisses, and the cherty iron ores to a gneissic rock consisting of layers of quartz and specular iron.

An examination of a number of the contacts between the granites and the Huronian rocks shows an alteration, from a slight crumpling and baking to highly tilted and contorted crystalline schist and gneiss. The accompanying basic igneous rocks, originally fine-grained traps or diabase, are changed in like manner to strongly foliated hornblendic and chloritic schists, usually freely penetrated by quartz veins holding quantities of pyrite and other minerals.

In passing westward from Ungava bay the granite predominates along the coast, and the areas of the altered bedded rocks and their accompanying traps are much smaller, and are so intimately intruded by the granite that it is very difficult to separate them. The gneisses of the altered Huronian rocks can only be guessed at, by their texture, light colour and the presence of garnet in them. The ancient traps and greenstone masses are more easily separated from the complex, but they are so penetrated by the granites that it is impossible to trace them except on a large scale detailed map, which would require many years’ work to complete.

Large masses of these basic rocks occur along the coast in several places between Cape Hopes Advance and Douglas harbour, most noticeably about Wakeham and Fisher bays, where quartz veins are numerous, and carry considerable quantities of sulphides.

The examination of the coast to the westward of Douglas harbour was only such as could be made from the ship, and lacks all the detail of the eastern portion. Red granite gneisses appear to occupy the greater portion of the coast, with areas of dark basic rocks at intervals. At Sugluk bay, where a closer examination was made, a medium to coarse-grained pink to red mica and mica-hornblende granite-gneiss was most abundant. This granite inclosed bands of a lighter coloured quartzose-gneiss, and also intruded large masses of dark-green altered diabase.

The granite-gneisses occupy the coast to within a few miles of Cape Wolstenholme, when the prevailing rock is a rusty fine-grained sillimanite-gneiss containing scales of graphite and considerable pyrite in small grains disseminated through the rock. These dark gneisses are inclosed and penetrated by the granite-gneisses, and probably represent portions of the ancient bedded series.

Beyond Cape Wolstenholme, gneisses occupy the eastern coast of Hudson bay to within a short distance of Cape Smith, where a high ridge of trap runs inland in a northeast direction and has a width of several miles. Further south the gneisses again predominate along the coast to the Portland promontory in latitude 58° N.