Chapter II: Part 2

Certain abrupt disturbances of the general uniform attitude suggest differential movements. Along the West branch below Wapus creek the dip and strike of the shale and greywacke are constant, until where the river’s course changes to due east. Along the shores of this stretch the rocks are mostly hidden by swamp, but where they do outcrop they are standing vertically or dipping steeply to the south, and the strike corresponds with the course of the stream; that is, their positions are at right angles to those farther south. Disturbances of this sort are known, due to the contiguity of igneous intrusions, but at this point no such intrusive is known. It will also be seen from the map that exactly in the same line the East branch makes a similar abrupt change in course. Whether a line of low relief is continuous across the interval between the two streams at this point is not easily determined; however, as a possible explanation of the conditions stated, faulting along this line is suggested. A similar abrupt change from conditions of approximate horizontality to a dip S. 60 W., < 80° and strike of S. 30° E. was noted on the west side of Firth lake.

_Relations to other Formations._

The intrusion of the quartz diabase into the Huronian was gently accomplished at most points, and the beds of the latter, both above and below the intrusives, are inclined only a few degrees more steeply than in localities where no diabase can be found. Evidence of intrusion, however, is common, and at some points the Huronian next to the diabase has suffered local but intense physical change. Near the middle of the east shore of Firth lake a rocky islet only a few square yards in extent consists of coarse diabase and conglomerate in intimate contact, little tongues of the former being protruded into the sedimentary rock and peripherally chilled. Most remarkable, however, is the change in condition of the conglomerate; a few chains away on the main shore it is of ordinary character, but on the islet the pebbles lie within a fairly well foliated schist, standing vertically and striking about east and west. An identical condition exists at the south end of a little pond lying 40 chains west of Mosher lake. The vertical foliation of the conglomerate suggests the neighbouring diabase intrusion to have been by vertical ascension rather than lateral spread, so that these points may represent portions of vents through which the diabase magma ascended, and for that reason are more affected than where sills have been quietly injected.

Ordinarily these contacts occur in low ground, usually ravines, the bottoms of which are soil filled and consequently unfavourable for geological observation, but at some points on Duncan lake the contacts are exposed and the Huronian is seen to be much fractured across a zone extending many feet from the diabase. In addition to the fracturing the greywacke is hardened and the bedding planes rendered obscure, the total effect being to weaken its power of resistance to erosion.

In the neighbourhood of these contacts the Huronian is well supplied with quartz veins whose ‘comb’ structure and chalcopyrite-galena mineralization identify them with similar veins in the diabase. Also the sediments exhibit certain mineralogical alterations referable to action of the diabase. West of Gowganda, on the West branch below Duncan lake and at other places the greywacke for a width of about two feet from the diabase has been hardened, bleached a light grey colour and filled with circular black spots 1/16ʺ in diameter. Microscopic examination shows the main portion to consist of a mosaic of small quartz, orthoclase and acid plagioclase grains, through which are distributed patches of chlorite. This spotted phase of the greywacke evidently represents an early stage in the development of adinole, a characteristic contact product of shales, intruded by basic rock.

The relations of the Huronian to the Archæan, exhibited in larger as well as minor features, indicate that the surface of the latter had been carved into a condition not greatly unlike the present topography, before its submergence and sedimentation in Huronian times. Some of the hills of this ancient land have been uncovered by the removal of their sedimentary blanket, leaving vestiges of the latter around their bases as in the case of the hills south-west of Mosher lake. There the dip of the sedimentary beds is much less than the slope of the hills, so that the latter must project up through them as cores. In the bay on the east side of Pigeon lake Huronian shales dipping with an angle of about 15° abut against the side of an Archæan hill composed of hornblende granite and green schist. At almost any part of the region where both Huronian and Archæan occur together, similar evidence is available concerning the unevenness of the pre-Huronian land surface. The amount of topographical relief cannot be estimated with any degree of accuracy, for tops of the Keewatin hills now exposed have probably been removed by post-Huronian erosion, the lowest depressions are still filled by Huronian and the whole may have been disarranged by post-Archæan faulting. However, near Mosher lake there was a minimum relief of 300 feet.

This old pre-Huronian surface is not often accessible for study, the contacts being vertical or hidden by soils and vegetation. At one point, however, at the end of the portion of Wapus creek shown on the map, exceptionally favourable circumstances were encountered. Here glaciation has developed a rounded knoll of mixed Keewatin and Laurentian rocks upon which are tightly fastened a few scale-like vestiges of Huronian conglomerate. A few square feet of the original Archæan surface exposed by chiseling away the Huronian, was found to be much more highly polished than the immediately adjoining, recently glaciated surface which had been exposed to the atmosphere. The protected material seemed to be of about the same freshness as that exposed. This pre-Huronian surface is evidently a water-worn one, or the result of Huronian glaciation, but no characteristic markings were observed upon it.

_Origin and Correlation._

From the foregoing consideration of the Huronian as seen in the Montreal River region it will be plain that it is composed at all points of clastic sedimentary deposits. Fossils have never been found, so the correlation of these rocks in various areas is based upon their lithological similarities and continuity. Upon these grounds the Huronian of the present district is considered to be equivalent to the same formations in the Cobalt, Larder Lake, and other neighbouring districts, known as the Lower Huronian. The succession and physical character of the different formations are essentially identical. It is not necessary to review the facts upon which the decision to so place these formations is based, the evidence being the harmonious results of years of investigation by capable geologists. Accepting their conclusion, and calling the main sedimentary series of the Montreal River district, Lower Huronian, it is of interest to note indication of sedimentary materials still older. The conglomerate pebble found in the basal conglomerate on Pigeon lake must have originated by the destruction of a pre-Huronian conglomerate formation.

It has also been stated that ground for differentiating between a Lower and Middle Huronian in this area has not been obtained, although the similarity of the arkose to a formation in the Cobalt district believed to belong to the Middle Huronian suggests it to be of the same age. It is, therefore, thought desirable to apply to the whole the term Huronian. No clearness or additional truth would be gained by making a distinction between Lower and Middle divisions in this district, and so far as the economic exploitation of the district is concerned the arkose seems to be as much a part of the Lower Huronian as the conglomerate or greywacke.

POST-HURONIAN ERUPTIVES.

There are two kinds of diabase known in the district, one of which greatly exceeds the other in extent and economic importance. This disparity is tacitly recognized by the common use of the generic term diabase for the important quartz diabase, the other member of the family being ignored or unknown.

_Quartz Diabase._

_Character of contacts and distribution._—Bodies of this rock are not restricted to any one formation or locality; but, as may be seen by reference to the map, occur with various dimensions over the whole area, with the exception of the country lying north-west of Duncan lake. It may be noted that virtually all the large areas are enclosed by Huronian, the bodies within the Archæan being numerous but small. It is not proposed to apply this distinction generally, but in the Montreal River region it seems to be more than an expression of the law of probability. In the Archæan practically all of the observed diabase bodies are dikes, in approximately vertical positions, seldom 100 feet in width and of undetermined length. A knowledge of all those in the Huronian could not be obtained, but in some cases they are sills, whose greater exposed dimensions are parallel to the bedding planes of the enclosing sedimentaries.

_Macroscopic character._—It is fortunate for the easy recognition of the diabase that it is more or less continuously exposed, and that there are not many other igneous rocks of similar character in its proximity, for it presents a variety of types such that a representative collection of hand specimens presents surprisingly great petrological differences. During the process of solidification, magmatic differentiation evolved from the cooling material a group of forms of different mineralogical composition and physical appearance, the end members of which are very unlike.

The common type is a dark green massive diabase, ranging in texture from one in which the individual minerals are barely distinguishable to others containing amphibole crystals an inch in length. The combination of black amphibole—an alteration product of augite—and grey or flesh-coloured plagioclase give the surface of ordinary textured phases a colouration of sufficient determinative value. In a large diabase body the coarseness is equal to that of ordinary granite, and the diabasic structure is not readily perceptible. At the edge of the large dikes and throughout the smaller ones the rock is black in colour and much finer grained on account of its more rapid solidification.

In the dikes the mineralogical composition is tolerably constant, and specimens selected from different points show no notable difference except that they are usually less decomposed than the coarse grained varieties. Within the larger bodies, where cooling may be considered to have been slower, a series of rock types differing from one another in mineral composition, and consequently in physical appearance, are associated. At many localities these differentiated varieties are intimately intermingled, so that within an area of a few square yards almost the whole series may be found. Conditions of this sort were first and best observed in the Lett properties on Wapus creek, where the extensive stripping and trenching greatly facilitated geological study. A suite of specimens was obtained which exhibit an unbroken gradation from ordinary gabbro to the fine grained pink rock known as aplite. With a decreasing pyroxene content and increasing abundance of feldspar the rock grades from a dark green diabase at the basic end through a reddish phase into a type which, in the field, might be termed a syenite, being of granitic texture, red colour, and without visible quartz. These phases are cut by aplite dikes which at first glance do not very closely resemble them, but their comparison has shown that they too include a group whose coarsest and most basic form does not differ greatly from the syenitic type of the diabase series. From a pale flesh-coloured rock of fine granitic texture in which a little dark mineral is visible, the successive phases of the aplite graduate toward a dike material of light pink colour and saccharine texture almost devoid of ferromagnesian constituents.

_Microscopic character._—The consanguinity of diabase and aplite is further established by microscopic study. It was intended to make a somewhat complete comparative study; but, at the outset, the materials, although fresh looking in the hand specimens, were found to be much decomposed, sometimes so completely that the original composition could not be satisfactorily inferred, and an outline must suffice therefore until fresher material is secured.

The common gabbro type consists essentially of long prisms of plagioclase embedded in light reddish augite. This ophitic structure, upon which the distinction between diabase and gabbro depends, is well developed, but does not show in hand specimens, so that for field use the distinction is impracticable; ordinarily the term gabbro is applied to the coarse grained, and diabase to the medium and finer grained varieties. The plagioclase of the coarse grained specimens could not be identified, being entirely altered to a coarse saussurite in which the epidote was aggregated into large grains. The augite is almost equally changed to strongly pleochroic hornblende possessing green and blue green pleochroic tints. This hornblende is not a fibrous variety but forms compact individuals, hence in the specimens studied it could not be certain that some of it was not primary. In some cases it is further altered to chlorite. Reaction between plagioclase and pyroxene seems to have taken place, for chlorite occurs among the plagioclase decomposition products as well as those of the pyroxene. Next to these, ilmenite is the most abundant constituent, occurring as irregular masses largely altered to leucoxene in which the original ‘gridiron’ structure is distinct. Quartz is present in subordinate amounts usually in micrographic intergrowth with the plagioclase. Small, well defined hexagonal rods of apatite, titanite crystals, and rare zircons are also present. The structure and mineral constitution render the term quartz-diabase appropriate. Finer grained specimens secured from dikes were found to be much fresher than the coarser types and yielded more satisfactory thin sections; the ophitic structure is more pronounced, but the mineral composition is the same. The plagioclase laths of one section were determined optically to be an intermediate labradorite. Small flakes of biotite partially altered to chlorite occur accessorily.

The aplite is also so much weathered that doubt sometimes exists as to its original composition. Thin sections consist very largely of plagioclase and quartz, coloured constituents being small in quantity. The plagioclase is twinned according to albite, pericline, and carlsbad laws, and in one case a baveno twin was observed; optically it behaves as almost pure albite and is decomposed to sericite instead of epidote. A poikilitic arrangement is more or less distinct; the feldspar is also micrographically intergrown with quartz. No orthoclase could be identified in any of the specimens. Quartz does not appear to be much more abundant than in the diabase. The only recognizable ferro-magnesian mineral is a strongly pleochroic reddish brown biotite, which occurs sparingly in small ragged flakes, partly altered to chlorite. Leucoxene representing ilmenite is surprisingly abundant considering the scarcity of iron bearing silicates. Apatite is an abundant accessory mineral, forming small prisms, while zircon crystals are rare. The rock in the specimens examined is remarkably rich in calcite, which in amount ranks next to the plagioclase.

Comparison of sections from specimens intermediate between the aplite and the ordinary diabase brings out some features of the differentiating process. The governing changes are in the proportion of pyroxene, and in the composition of the plagioclase. A specimen somewhat paler in colour than the typical diabase was found to contain considerably less augite and more abundant plagioclase, the other constituents remaining fairly constant. The plagioclase was an acid andesine of the composition (Ab 65 An 35). A still lighter coloured type possessed oligoclase (Ab 72 An 28) and a small amount of blue green hornblende, representing the wholly altered pyroxene. Orthoclase could not be found in any of the sections, so that none of these rocks can be properly called syenite or granite.

_Local description._—Diabase is most abundantly exposed in the area between Gowganda lake and the portage route connecting Firth and Elkhorn lakes, where it forms three parallel tongues of approximately equal dimensions. Coarse grained types prevail in which the differentiation of acid phases is pronounced. Aplite dikes up to 10 feet in width, fairly coarse grained and sometimes tolerably rich in dark constituents, are abundant. The rugged surface of this part of the country is largely due to the presence of the diabase, the peculiar arrangement of which has produced a constant system of north and south ridges. The contacts with the Huronian occupy the bottoms of gullies, with the main body of diabase forming high ground. This highly relieved and consequently well exposed surface has greatly facilitated the exploitation of this area, as indeed is the case for the whole district. Terminally each of the three bodies tapers out or forks, but these details were not closely mapped. In the case of the most easterly one the portions reaching the east side of Firth lake are darker and more decomposed than the ordinary diabase, and during the field operations were considered of other character. Laboratory study of the specimens shows them, however, to be basic diabase in which hornblende has completely replaced the pyroxene. In consequence of this misconception the connexions of the exposures on Firth lake were not well worked out, but they almost certainly lie as shown in the map and may form a continuous connexion with the large diabase body farther north. The two areas north-east of Firth lake present much the same appearance as those of the Gowganda district.

The most extensive body is that which coincides in direction with Duncan lake, resembling a great hook, the shank of which is traceable for twelve miles, the crooked end lying about midway between the West branch and Firth lake. Neither termination was found, on account of the swampy or sandy character of the country, so that the present representation may not be complete. Just east of L’Africain lake there are some diabases which may be continuations of it, but owing to their altered appearance they could not be distinguished with certainty in the field from similar Keewatin forms. Along Duncan lake it appears to represent the edge of a sill about 300 feet thick lying in the bedding plane of the Huronian sediments which lie both above and beneath it. From the attitude of the latter the sill is believed to dip eastward at an angle of 30 or 40 degrees. The exposed width is usually less than in the Gowganda area and its composition is more homogeneous, but at the wider portions the same intermingling of basic and acid phases and aplite dikes obtains, as for example where it crosses Wapus creek. The full extent of that portion which extends north-westward from Mosher lake is not known. The formation at that point is obscured by gravelly soil; it appears, however, to be unusually wide and well differentiated. An apparently large body of diabase lies between the north part of Duncan lake and the West branch. The mapping of this was left incomplete, so that its total southern extent cannot be given. Its northern part presents nothing unusual, but about Vipond lake a syenitic phase is developed, probably indicating a mingling of differentiated rock varieties as at Gowganda lake or Wapus creek.

The remaining diabase bodies are dikes. Probably these are very numerous and widespread, but this can only be determined by work of much more widespread nature than the economic possibilities of such an investigation warrant at present. They are most frequently seen in the Laurentian, probably not so much because they are more numerous there, but because they are more conspicuous in the granites than in the Keewatin schists and Huronian, from which they differ less in colour. They attain widths of 60, 100 or more feet, in which cases the texture is like that of the large masses, but differentiated types and aplite dikes do not seem to accompany them. The smaller dikes, diminishing to a width of 1 foot, are compact black rocks of microcrystalline habit, but like the gabbroid varieties mineralogically.

_Age._—The time of intrusion of these rocks can only be defined as post-Huronian or post Middle Huronian, there being no younger formations with which to correlate them. They are identical with the diabase in other parts of the Montreal River region and of Cobalt. As already noted the larger masses have produced very limited metamorphic changes in the adjoining rocks, developing incipient adinole zones in the Huronian greywackes, besides hardening and fracturing them. Usually the contact edge of the diabase has been deeply eroded along with the adjoining rock to form narrow ravines, but wherever it persists a slight chilling is perceptible. The fine grained edges are much more apparent in dikes where the mass of hot material being much less was more susceptible to the influence of cold surroundings. The intrusive nature is also demonstrated by angular blocks of Huronian materials enclosed within the diabase, instances of which may be seen on Wapus creek.

_Olivine Diabase._

At the first rapid above Kenisheong lake the Huronian is cut by a broad dike of different character from those belonging to the quartz-diabase intrusion. It is a remarkably fresh compact rock of dark grey colour and medium texture in which an ophitic structure is prominent, acicular prisms of glassy feldspar penetrating the dark main mass. Its density is 2·991. Under the microscope it is holocrystalline and the constituent minerals occur in only one generation. The constituents as determined by linear measurements were found to be plagioclase, 67·5 per cent; olivine, 14 per cent; augite, 1·5 per cent; iron ore, probably ilmenite, 5 per cent; apatite, 1·8 per cent; biotite, 1·3 per cent; and zircon, 0·03 per cent. The rock is remarkably fresh, even the olivine showing no signs of decomposition. The plagioclase was determined by optical methods to be a labradorite of the composition Ab 1 An 1. It forms laths, twinned according to albite, pericline and carlsbad laws, which penetrate the ferromagnesian minerals. A few large crystals show fine zonary lamellation. Olivine is in idiomorphic or rounded grains, occasionally bordered by a little rim of biotite, possibly a product of reaction during the period of crystallization. The augite is reddish brown in colour and later than either olivine or plagioclase, filling the interstices between the feldspar laths. Irregular masses of black iron ore, probably ilmenite, are scattered throughout the section, in some cases showing good crystal forms. A deep brown strongly pleochroic biotite with a very small optical angle occurs accessorily in small shreds. Apatite is mostly in slender but sometimes stout hexagonal prisms. Minute crystals of zircon are rare.

The rock may be designated an olivine diabase of markedly fresh aspect. It penetrates the Huronian, but judging by its unusually fresh condition it must be comparatively young.

PLEISTOCENE.

The present glaciated pre-Cambrian surface is scantily covered by unconsolidated glacial sands and gravel which are being collected by natural agencies from the hills and more elevated parts into the depressions. As a consequence the hills are bare, while the valleys and ravines are soil-filled and support a strong forest growth. Neither sand nor gravel show signs of stratified arrangement. They play an unimportant part in the topographical appearance of the country; the only elevation composed of such materials being a small gravel hill to the east of Porphyry lake. Between that point and the hills near Mosher lake is a considerable extent of flat sandy country, the gentle contour of which contrasts with that of the surrounding hills.

A rather peculiar low apron of sand occupies the very end of the peninsula between Duncan lake and the West branch. It is of small extent, and is probably due to river deposition, the West branch at this point being sluggish and the surface of the sand showing indications of shifting stream beds.

An extensive area of sand lies at the end of Duncan lake, from whence it extends northward for several miles, also westward and south-westward toward the 550 foot hill shown on the map. Seen from any neighbouring hill this plain appears flat in comparison with the ordinary surface of the country. It consists of a fine, yellowish, unstratified sand. The several brooks crossing it are distinguished from those of other parts of the country by their tortuous courses which are constantly changing, and which render them unfit for canoe travel. The shallow character and sandy shores at the north end of Duncan lake have been caused largely by the transportation of sand into it by these brooks.

Glacial boulders are scattered over the whole district.

ECONOMIC GEOLOGY.

SILVER.

DISTRIBUTION.

With the knowledge acquired from exploitation of James township, and other of the more recently discovered silver-cobalt camps, prospectors in the Montreal River district gave exclusive attention to the diabase formation, recognizing it to be closely connected with mineralizations of this kind. Some work was done in 1907 and more in the following season, with the result that on August 4, the first native silver discoveries were made, almost simultaneously and at short distances apart, by Messrs. Mann and Dobie, in the diabase just west of Gowganda lake. The remarkably rich surface showings at once attracted the attention of the whole prospecting body in the Elk Lake country, and an activity began which, since the spreading of information to outside points, has developed into a ‘rush’ of large dimensions.

The known silver bearing area is restricted as yet to about ten square miles lying between Gowganda lake and the portage route from Elkhorn to Firth lakes, and is commonly known as Gowganda. Extensive prospecting only commenced in September, about the close of the field season, so that only the earlier discoveries are known to the writer, and a knowledge of the surface details could only be derived by examination of the few beginnings of patient and continued exploration by claim owners. The present account must accordingly be accepted as incomplete and by no means representing the present status of the Gowganda camp.

SURFACE INDICATIONS.

Conditions in the region are such as to demand exploration of the closest and most intensive order, for the indications of mineralization are negative rather than positive in character. The Gowganda area was entirely forested at the beginning of 1908, and a carpet of moss and vegetable mould covered most of the rock surface. Glacial materials are also fairly abundant, and sometimes thick enough to render surface exploration arduous and expensive. Added to this the veins are eroded more deeply than the country rock, and are represented at the surface by crevices filled with soil, and thereby rendered inconspicuous. Were the country a flat one the difficulties in the way of successful prospecting would be very serious, but fortunately it is rugged, especially near the diabase. Steep ridges of this material are a regular topographical feature. The sides of these ridges are bare or readily exposed and offer fine opportunities for examination. It is significant that the first silver discoveries were made in the sides of such rock walls. The pink bloom found at the surfaces of the veins and the adjacent country rock is also an indicator whose value is fully understood by those working in the region.

STRUCTURE OF VEINS.

The deposits are in the form of well-defined veins occupying fissures in the diabase. The amount of surface work done in September was not enough to throw much light on the continuity of the veins, but a few had been traced for distances of 300 or 400 feet, and in one case across several contiguous mining claims, so that they may be said to occupy persistent fissures. They vary in width from 1ʺ up to 20ʺ. Little could be learned concerning their attitudes except where they traverse hillsides; in such cases they are approximately vertical. It is not yet known whether any regularity exists in their arrangement, but some extend east and west while others are north and south. The diabase shows no signs of extensive deformation, all geological evidence indicating that since its solidification its history has been uneventful, yet the cracks which the veins occupy appear too persistent to be the result of contraction by cooling. Besides the strong veins there are others of the gash type, but the latter are small, not very continuous and poorly or not at all mineralized.

COMPOSITION OF VEINS.

From comparison of veins at Gowganda, Duncan lake, and Wapus creek a general uniformity of structure, though not of mineralization, is found to obtain. The whole mineral association is not found in any one vein, nor are the relative proportions either of ore or gangue at all constant. The gangue minerals are quartz and calcite, always mutually arranged in definite manner. The sides of the veins are composed of white quartz, which may form only an insignificant coating on the walls or may occupy nearly the whole space, but in all cases there remains a central cavity into which the pointed ends of quartz crystals project freely. At the surface this central portion is empty owing to weathering, but farther down it is filled by calcite. Veins with predominant quartz filling seem especially abundant in the Huronian adjacent to the diabase. The rich veins near Gowganda, so far as ascertainable, are poor in quartz.

Practically all of them carry chalcopyrite either as diffuse grains or in considerable amounts. Pyrite is equally abundant but less constant. Galena is not uncommon. All these occur with the quartz; their presence in the calcite is not certainly known. Many of the veins show diffuse stains of reddish pink colour due to cobalt bloom, which though not in itself of value is important as a sign of the existence of smaltite from which it is formed by oxidation. The minerals enumerated thus far are widespread, but economically insignificant; the silver-cobalt association is present in some cases, however. Little opportunity existed in 1908 for favourable study of these minerals, so that only a list of those found at the surface can be given. There native silver, argentite, smaltite and cobalt bloom have been found, and a few feet down small lumps of native bismuth. Because they occur either in calcite or in loose decomposition materials filling the space which the calcite formerly occupied they are believed to be associated with that gangue. Infrequently gangue minerals are almost absent and the vein filled by massive ore.

LOCAL DISTRIBUTION.

Valuable argentiferous veins were known in 1908 only in the Gowganda district, and, so far as yet known, discoveries have been confined to the diabase west of that lake. Most of them occur in the southern portion of the central diabase strip which lies a short distance from the shore and extends northward for about seven miles from Elkhorn lake. On one of the Mann claims (T.R. 1966), now owned by Messrs. Foster, an east and west vein averaging 4ʺ or 5ʺ in width had been traced for 300 feet, the original discovery being made in the exposed face of a low diabase wall. At its surface the vein material had been weathered out for a depth of about 15ʺ and the cavity filled by a brownish mass of the decomposed matter mixed with vegetable mould and sand. Nuggets of mossy or arborescent silver were scattered richly through this dirt, and a fairly continuous spine of the same metal, sometimes an inch thick, extended along the middle of the crevice. A test pit sunk about 8 feet, but barricaded at the time of the writer’s visit, had exposed, according to Mr. Mann, silver and smaltite in a calcite vein. On the adjoining claim (T.R. 1982), a vein of massive smaltite about 1ʺ wide was seen; a little silver had been found at its surface and streaks of argentite and disseminated grains of smaltite were seen in the wall rock. Aplite dikes on another claim were found to be stained by cobalt bloom, and full of disseminated chalcopyrite.

The properties owned by Messrs. Crawford and Dobie about half a mile farther south were not visited, but were generally reported to be of about the same richness as that in T.R. 1966. Immediately north of Hanging-stone lake Mr. F. A. McIntosh was conducting active prospecting in a coarse gabbroid, locally syenitic, form of the diabase, intersected by aplite dikes. A discovery of native silver has been made since then and the property sold to Messrs. F. R. Bartlett & Co., of Toronto, together with other claims located between the north-east and north-west arms. Other discoveries are reported just south-east, also a short distance north of Milne lake.

No silver had been obtained in the eastern diabase strip, although the geological conditions appear identical and calcite veins are abundant. An exceptionally large vein, about 18ʺ wide, and traceable across two adjoining claims was seen on the property of Messrs. McLaughlin and McIntosh, about half a mile north-east of the north-west arm. Mineralization in it near the surface was very slight. Several veins carrying small amounts of chalcopyrite, pyrite, bloom and smaltite were seen on the properties of Messrs. Elstone and Reilly (T.R. 1961, 1962 and 1903). In one of them small amounts of bismuth are present; another contains an unusually heavy black substance which proved to be calcite filled with minute crystals of magnetite.

In the western strip less exploration had been performed and little could be learned about the ore deposits. Loose pieces of native silver had been found by W. H. Margueratt in narrow fissures on M.R. 1798, but the vein material was not exposed.

Outside the Gowganda area systematic prospecting was in progress at only one point—Wapus creek. Under the management of Mr. Robert Lett a group of nine claims was being stripped and trenched, with the result that numerous calcite veins had been traced through a diabase showing the same complex intermingling of basic and acid phases and aplite dikes as at Gowganda. Chalcopyrite and cobalt bloom were abundant, and smaltite had been found as disseminations in the wall rock. Lumps of native bismuth weighing several ounces had been taken from a fissure in an aplite dike, analyses of which showed it to contain silver.

Tentative exploration was being conducted along Duncan lake and east of Firth lake, but not with the closeness and persistence which the topography of these veins require. In general the veins seen on Duncan lake are exceptionally rich in quartz, and gash veins are common. Chalcopyrite, pyrite and galena are the most noticeable metalliferous minerals, but cobalt bloom stains are frequently observable. So far as known no attention has been given to the large diabase body between Duncan lake and the West branch, although its size and varied composition are thought to make it a desirable prospecting ground.

FUTURE POSSIBILITIES.

The present knowledge of the Gowganda area indicates it to be highly mineralized, at least in so far as number of veins and surface showings are concerned. The number of discoveries within its area of ten square miles is steadily increasing. The area, character of the mineral association and the richness of the surface showings are comparable with those of Cobalt. There is a general similarity in the geological conditions. The mineralized veins in Gowganda occur in the diabase as do some of the good Cobalt veins. There are, it is true, local differences, but the resemblances are more pronounced than the differences and lead to the hope that exploitation will reveal similar underground conditions. The well mineralized veins are sufficiently long and uniform on the surface to suggest similarly persistent vertical dimensions. Further geological work may reveal something definite concerning the character and size of the diabase bodies which form the country rock, and thus afford a basis for predicting their subterranean distribution. While there are grounds for hoping that the veins will persist in depth, this has not yet been proved, nor, if this is the case, that the mineralization and values are also persistent.

The relative importance of Gowganda is therefore a matter of uncertainty as yet, but it may be confidently affirmed that for its state of development the outlook is very favourable, and the number of veins, area of mineralization and rich surface showings afford good grounds for hoping that some at least of the veins will be found to be commercially important.

The details of igneous intrusion, differentiation and mineralization may never be sufficiently understood to allow of accurate prediction regarding the location of silver deposits, but a general conception of the sequence of events culminating in their formation does permit of the formulation of certain criteria useful in the search for ores. Evidence is accumulating to show that the silver-cobalt mineralizations in the Timiskaming region are connected with a late stage of differentiation in the magma which supplied the quartz diabase and aplite. It seems reasonable, therefore, to anticipate ore deposits in or near such bodies, especially if they are of large size and have undergone important chemical differentiation, that is, if they contain a varied and extensive association of basic and acid phases of the diabase. Pre-existing channels to receive the mineralizers are also necessary and their distribution a matter of vital importance, but in this region they appear to have been everywhere abundant.

These conditions appear to exist quite as fully at several other localities besides Gowganda. At Wapus creek they seem identical and, indeed, results obtained thus far indicate that some mineralization of the silver-cobalt type exists. Between Duncan lake and the West branch the conditions require further study, but, as now known, are not discouraging.

COPPER.

The chalcopyrite, which seems a much more constant constituent of the veins associated with the quartz diabase, is sometimes aggregated into bunches which yield ore specimens of such excellent appearance as to arouse interest. The ore is, however, confined to veins a few inches in width and so scattered as to render them valueless. Occurrences of this kind characterize most of the great diabase bodies, examples of which occur on Mosher lake, between the North-east and North-west arms of Gowganda lake and elsewhere. The chalcopyrite is sometimes superficially altered to malachite and azurite.

IRON ORE.

_Hematite._—Excellent specular and kidney ore is known to exist a short distance east of Nest lake, but the locality was not visited owing to the more urgent requirements of other portions of the district. Specimens of the ore obtained, however, proved to be of excellent character, with little admixture of silica or other foreign matter. The ore body is thought to be of vertical tabular form, occupying a fissure-like space. Its limits are not known, consequently nothing can be yet stated regarding the commercial possibility of the deposit.

Specular ore was seen on mining claim T.R. 2009, near the north-east end of Firth lake, occupying a fissure in the Keewatin. The ore is of good quality, but the outcrop is of insignificant size, the fissure being only about 2 feet wide, and no ore occurring in either the chlorite schist or reddish granite which lie on either side.

Specular ore also occurs in the basal conglomerate of the Huronian series, filling the interstices between the pebbles where an original cement was deficient. At the south end of Kenisheong lake the conglomerate appears at the water’s edge, and the hematite may be observed while paddling near shore. The same thing occurs at the narrows on Duncan lake, just south of the central expansion. In neither case is the ore in commercially valuable quantity.

_Magnetite._—Keewatin iron formation exists about one-half mile to the north-east of Gowganda lake. A brief visit was paid to some claims belonging to Mr. Cryderman where the formation is well exposed. The Keewatin, which is partially overlain by Huronian and traversed by diabase, consists of dark grey or black, banded chert or quartzite associated with chlorite schist. The dark bands, usually only a few inches in width, are full of disseminated magnetite grains. No concentrations were noticed and the richest bands would probably yield less than 30 per cent metallic iron, consequently the present showings cannot be considered valuable.

ASBESTOS.

_Distribution._

In the Keewatin area between Firth and Obushkong lakes there occur masses of a basic igneous rock through whose decomposition serpentine and asbestos have been developed. The localities given in connexion with the description of the Keewatin may be briefly restated. Two bodies were found. One of these, lying east of Foot lake and 20 chains from Obushkong was traced for a width of 4 chains, but nothing learned of its north and south extent. It consists very largely of green serpentine traversed by a network of fine, white weathering veins of asbestos. More extensive outcrops exist along the east shore of Firth lake. At somewhat more than a mile from the foot of the lake and near a small log shack at the water’s edge a considerable mass of partially decomposed wehrlite, serpentine, and asbestos is visible. The main mass is of dark green colour, the asbestos traversing it abundantly as a series of glistening bright green threads. The seams are small, none being found more than 1/4ʺ in width, but the asbestos fibres are fine and elastic. The serpentine is often coarsely fibrous but brittle.

ORIGIN.

Microscopic examination shows the serpentine and asbestos to be the product of decomposition of the wehrlite, a nearly black medium grained igneous type. Alteration has obscured its original character, but sufficient of the primary constituents remain to admit of its determination. It consisted of olivine, diallage, and common hornblende, with considerable ilmenite and apatite, but plagioclase is apparently absent. Hornblende and diallage form the basis of the section in which lie abundant rounded or idiomorphic grains of olivine. The latter is completely altered to a matted intergrowth of fibrous serpentine containing scattered grains of black iron ore. Diallage persists as colourless bi-refringent remnants enclosed by a felted mass of decomposition products, chiefly long scales of talc. The hornblende is fresher and strongly pleochroic, the tints being green; its alteration begins by bleaching, followed by development of colourless fibres of low bi-refringence, possibly serpentine. Primary ilmenite is replaced by irregular patches of leucoxene, showing gridiron structure. The final product of alteration is a soft green serpentine rock composed almost wholly of that mineral.

The limits of these masses are exceedingly difficult to define, owing to the fact that they are associated with other Keewatin rock and basic forms of the post-Huronian diabase, to which it presents considerable resemblance. The asbestos actually seen is probably too short and small in amount to be valuable, but the high commercial value of this material renders delimitation of the wehrlite masses advisable. Asbestos of very good quality has been found by Mr. George Rahn in the vicinity of Sinclair mountain, so that this mineral may be one of the district’s latent resources.

CANADA

DEPARTMENT OF MINES

GEOLOGICAL SURVEY BRANCH

HON. W. TEMPLEMAN, MINISTER; A. P. LOW, LL.D., DEPUTY MINISTER;
R. W. BROCK, DIRECTOR.

----------------------------------------------------------------

SELECTED LIST OF REPORTS AND MAPS

(SINCE 1885)

OF SPECIAL ECONOMIC INTEREST

PUBLISHED BY

THE GEOLOGICAL SURVEY BRANCH

* Publications marked thus are out of print.

Reports of the Mines Section—

No. 245. Report of Mines Section for 1886.
272. " " 1887.
300. " " 1888.
301. " " 1889.
334. " " 1890.
335. " " 1891.
360. " " 1892.
572. " " 1893-4.
602. " " 1895.
625. " " 1896.
662. " " 1897.
698. " " 1898.
718. " " 1899.
744. " " 1900.
800. " " 1901.
835. " " 1902.
893. " " 1903.
928. " " 1904.
971. " " 1905.

Mineral Production of Canada—

No. 414. For 1886.
415. " 1887.
416. " 1888.
417. " 1889.
418. " 1890.
419. " 1891.
420. " 1886-91.
421. " 1892.
422. " 1893.
555. " 1894.
577. " 1895.
612. " 1896.
623. " 1886-96.
640. " 1897.
671. " 1898.
686. " 1899.
719. " 1900.
719a. " 1901.
813. " 1902.
861. " 1903.
896. " 1904.
924. " 1905.
981. " 1906.

Mineral Resources Bulletins—

No. *818. Platinum.
851. Coal.
*854. Asbestos.
857. Infusorial Earth.
858. Manganese.
859. Salt.
860. Zinc.
869. Mica.
872. Molybdenum and Tungsten.
877. Graphite.
880. Peat.
881. Phosphate.
882. Copper.
913. Mineral Pigments.
953. Barytes.
984. Mineral Pigments (French).

Reports of the Section of Chemistry and Mineralogy—

No. *102. For 1874-5.
*110. " 1875-6.
*119. " 1876-7.
126. " 1877-8.
138. " 1878-9.
148. " 1879-80.
156. " 1880-1-2.
169. " 1882-3-4.
222. " 1885.
246. " 1886.
273. " 1887-8.
299. " 1888-9.
333. " 1890-1.
359. " 1892-3.
580. " 1894.
616. " 1895.
651. " 1896.
695. " 1898.
724. " 1899.
821. " 1900.
*958. " 1906.

745. Altitudes of Canada, by J. White. 1899.

*972. Descriptive Catalogue of Minerals and Rocks, by R. A. A. Johnston
and G. A. Young.

YUKON.

*260. Yukon district, by G. M. Dawson. 1887. Maps Nos. 274, scale 60 m.
= 1 in.; 275-277, scale 8 m. = 1 in.

295. Yukon and Mackenzie basins, by R. G. McConnell. 1889. Map No. 304,
scale 48 m. = 1 in.

687. Klondike gold fields (preliminary), by R. G. McConnell. 1900. Map
No. 688, scale 2 m. = 1 in.

884. Klondike gold fields, by R. G. McConnell. 1901. Map No. 772, scale
2 m. = 1 in.

*909. Windy Arm, Tagish lake, by R. G. McConnell. 1906. Map No. 916,
scale 2 m. = 1 in.

943. Upper Stewart river, by J. Keele. Map No. 938, }
scale 8 m. = 1 in. }
} Bound together.
951. Peel and Wind rivers, by Chas. Camsell. Map No. }
942, scale 8 m. = 1 in. }

979. Klondike gravels, by R. G. McConnell. Map No. 1011, scale 40 ch. =
1 in.

982. Conrad and Whitehorse mining districts, by D. D. Cairnes. 1901. Map
No. 990, scale 2 m. = 1 in.

1016. Klondike Creek and Hill gravels, by R. G. McConnell. (French). Map
No. 1011, scale 40 ch. = 1 in.

BRITISH COLUMBIA.

212. The Rocky mountains (between latitudes 49° and 51° 30ʹ), by G. M.
Dawson. 1885. Map No. 223, scale 6 m. = 1 in. Map No. 224, scale 1-1/2
m. = 1 in.

*235. Vancouver island, by G. M. Dawson. 1886. Map No. 247, scale 8 m. =
1 in.

236. The Rocky mountains, geological structure, by R. G. McConnell.
1886. Map No. 248, scale 2 m. = 1 in.

263. Cariboo mining district, by A. Bowman. 1887. Maps Nos. 278-281.

*271. Mineral wealth, by G. M. Dawson.

*294. West Kootenay district, by G. M. Dawson. 1888-9. Map No. 303,
scale 8 m. = 1 in.

*573. Kamloops district, by G. M. Dawson. 1894. Maps Nos. 556-7, scale 4
m. = 1 in.

574. Finlay and Omineca rivers, by R. G. McConnell. 1894. Map No. 567,
scale 8 m. = 1 in.

743. Atlin Lake mining division, by J. C. Gwillim. 1899. Map No. 742,
scale 4 m. = 1 in.

939. Rossland district, by R. W. Brock. Map No. 941, scale 1,600 ft. = 1
in.

940. Graham island, by R. W. Ells. 1905. Map No. 921, scale 4 m. = 1
in., and Map No. 922, scale 1 m. = 1 in.

986. Similkameen district, by Chas. Camsell. Map. No. 987, scale 400 ch.
= 1 in.

988. Telkwa river and vicinity, by W. W. Leach. Map No. 989, scale 2 m.
= 1 in.

996. Nanaimo and New Westminster districts, by O. E. LeRoy. 1907. Map
No. 997, scale 4 m. = 1 in.

ALBERTA.

*237. Central portion, by J. B. Tyrrell. 1886. Maps Nos. 249 and 250,
scale 8 m. = 1 in.

324. Peace and Athabaska Rivers district, by R. G. McConnell. 1890-1.
Map No. 336, scale 48 m. = 1 in.

703. Yellowhead Pass route, by J. McEvoy. 1898. Map No. 676, scale 8 m.
= 1 in.

949. Cascade coal-field, by D. B. Dowling. Maps (8 sheets) Nos. 929-936,
scale 1 m. = 1 in.

968. Moose Mountain district, by D. D. Cairnes. Maps No. 963, scale 2 m.
= 1 in.; No. 966, scale 1 m. = 1 in.

SASKATCHEWAN.

213. Cypress hills and Wood mountain, by R. G. McConnell. 1885. Maps
Nos. 225 and 226, scale 8 m. = 1 in.

601. Country between Athabaska lake and Churchill river, by J. B.
Tyrrell and D. B. Dowling. 1895. Map No. 957, scale 25 m. = 1 in.

868. Souris River coal-field, by D. B. Dowling. 1902.

MANITOBA.

264. Duck and Riding mountains, by J. B. Tyrrell. 1887-8. Map No. 282,
scale 8 m. = 1 in.

296. Glacial Lake Agassiz, by W. Upham. 1889. Maps Nos. 314, 315, 316.

325. North-western portion, by J. B. Tyrrell. 1898. Maps Nos. 339 and
350, scale 8 m. = 1 in.

704. Lake Winnipeg (west shore), by D. B. Dowling. }
1898. Map No. 664, scale 8 m. = 1 in. }
} Bound together.
705. Lake Winnipeg (east shore), by J. B. Tyrrell. }
1898. Map No. 664, scale 8 m. = 1 in. }

NORTH WEST TERRITORIES.

217. Hudson bay and strait, by R. Bell. 1885. Map No. 229, scale 4 m. =
1 in.

238. Hudson bay, south of, by A. P. Low. 1886.

239. Attawapiskat and Albany rivers, by R. Bell. 1886.

244. Northern portion of the Dominion, by G. M. Dawson. 1886. Map No.
255, scale 200 m. = 1 in.

267. James bay and country east of Hudson bay, by A. P. Low.

578. Red lake and part of Berens river, by D. B. Dowling. 1894. Map No.
576, scale 8 m. = 1 in.

*584. Labrador peninsula, by A. P. Low. 1895. Maps Nos. 585-588, scale
25 m. = 1 in.

618. Dubawnt, Kazan and Ferguson rivers, by J. B. Tyrrell. 1896. Map No.
603, scale 25 m. = 1 in.

657. Northern portion of the Labrador peninsula, by A. P. Low.

680. South Shore Hudson strait and Ungava bay, by A. P. }
Low. Map No. 699, scale 25 m. = 1 in. }
} Bound together.
713. North Shore Hudson strait and Ungava bay, by R. }
Bell. Map No. 699, scale 25 m. = 1 in. }

725. Great Bear lake to Great Slave lake, by J. M. Bell. 1900.

778. East Coast Hudson bay, by A. P. Low. 1900. Maps Nos. 779, 780, 781,
scale 8 m. = 1 in.

786-787. Grass River region, by J. B. Tyrrell and D. B. Dowling. 1900.

815. Ekwan river and Sutton lakes, by D. B. Dowling. 1901. Map No. 751,
scale 50 m. = 1 in.

819. Nastapoka islands, Hudson bay, by A. P. Low. 1900.

905. The Cruise of the _Neptune_, by A. P. Low. 1905.

ONTARIO.

215. Lake of the Woods region, by A. C. Lawson. 1885. Map No. 227, scale
2 m. = 1 in.

*265. Rainy Lake region, by A. C. Lawson. 1887. Map No. 283, scale 4 m.
= 1 in.

266. Lake Superior, mines and mining, by E. D. Ingall. 1888. Maps Nos.
285, scale 4 m. = 1 in.; 286, scale 20 ch. = 1 in.

326. Sudbury mining district, by R. Bell. 1890-1. Map No. 343, scale 4
m. = 1 in.

327. Hunter island, by W. H. C. Smith. 1890-1. Map No. 342, scale 4 m. =
1 in.

332. Natural Gas and Petroleum, by H. P. H. Brumell. 1890-1. Maps Nos.
344-349.

357. Victoria, Peterborough and Hastings counties, by F. D. Adams.
1892-3.

627. On the French River sheet, by R. Bell. 1896. Map No. 570, scale 4
m. = 1 in.

678. Seine river and Lake Shebandowan map-sheets, by W. McInnes. 1897.
Maps Nos. 589 and 560, scale 4 m. = 1 in.

723. Iron deposits along Kingston and Pembroke railway, by E. D. Ingall.
1900. Map No. 626, scale 2 m. = 1 in; and plans of 13 mines.

739. Carleton, Russell and Prescott counties, by R. W. Ells. 1899. (See
No. 739, Quebec.)

741. Ottawa and vicinity, by R. W. Ells. 1900.

790. Perth sheet, by R. W. Ells. 1900. Map No. 789, scale 4 m. = 1 in.

961. Sudbury Nickel and Copper deposits, by A. E. Barlow. (Reprint).
Maps Nos. 775, 820, scale 1 m. = 1 in.; 824, 825, 864, scale 400 ft. =
1 in.

962. Nipissing and Timiskaming map-sheets, by A. E. Barlow. (Reprint).
Maps Nos. 599, 606, scale 4 m. = 1 in.; No. 944, scale 1 m. = 1 in.

965. Sudbury Nickel and Copper deposits, by A. E. Barlow. (French).

970. Report on Niagara Falls, by J. W. Spencer. Maps Nos. 926, 967.

977. Report on Pembroke sheet, by R. W. Ells. Map No. 660, scale 4 m. =
1 in.

992. Report on North-western Ontario, traversed by National
Transcontinental railway, between Lake Nipigon and Sturgeon lake, by
W. H. Collins. Map No. 993, scale 4 m. = 1 in.

998. Report on Pembroke sheet, by R. W. Ells. (French). Map No. 660,
scale 4 m. = 1 in.

QUEBEC.

216. Mistassini expedition, by A. P. Low. 1884-5. Map No. 228, scale 8
m. = 1 in.

240. Compton, Stanstead, Beauce, Richmond and Wolfe counties, by R. W.
Ells. 1886. Map No. 251 (Sherbrooke sheet), scale 4 m. = 1 in.

268. Megantic, Beauce, Dorchester, Levis, Bellechasse and Montmagny
counties, by R. W. Ells. 1887-8. Map No. 287, scale 40 ch. = 1 in.

297. Mineral resources, by R. W. Ells. 1889.

328. Portneuf, Quebec and Montmagny counties, by A. P. Low. 1890-1.

579. Eastern Townships, Montreal sheet, by R. W. Ells and F. D. Adams.
1894. Map No. 571, scale 4 m. = 1 in.

591. Laurentian area north of the Island of Montreal, by F. D. Adams.
1895. Map No. 590, scale 4 m. = 1 in.

670. Auriferous deposits, South-eastern portion, by R. Chalmers. 1895.
Map No. 667, scale 8 m. = 1 in.

707. Eastern Townships, Three Rivers sheet, by R. W. Ells. 1898.