Preliminary Report on Tadoussac Map-Area, Charlevoix, Chicoutimi and Saguenay Counties Province of Quebec, Canada

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RP 266(A) PRELIMINARY REPORT ON TADOUSSAC MAP-AREA, CHARLEVOIX, CHICOUTIMI AND SAGUENAY COUNTIES PROVINCE OF QUEBEC, CANADA

DEPARTMENT OF MINES

GEOLOGICAL SURVEYS BRANCH

PRELIMINARY REPORT

TADOUSSAC MAP-AREA

CHARLEVOIX, CHICOUTIMI

AND

SAGUENAY COUNTIES

M. L. MILLER

QUEBEC 1952

P. R. No. 266 PRELIMINARY REPORT

TADOUSSAC MAP-AREA

CHARLEVOIX, CHICOUTIMI, AND SAGUENAY COUNTIES

M.L. Miller

I N T R O D U C T I'O N

Location and Access

The Tadoussac map-area is on the north shore of St. Lawrence river about 120 miles northeast of the city of Quebec. The area, which was examined in 1951, is largely in the fifteen-minute quadrangle bounded by latitudes 48°00' and 48°15', and by longitudes 69°45' and 70°00'. About three-quarters of the area lies southwest of Saguenay river, and the remainder, northeast of it.

Access to the area is provided by Provincial highway 15 from Quebec city, which follows St. Lawrence river more or less closely, and highway 16, a few miles west of the western boundary, which links St. Simeon and Chicoutimi. Highway 15 is interrupted at Saguenay river, but a car ferry crosses between Baie Ste. Catherine and Tadoussac several times a day. Tadoussac is a port of call for summer cruise ships of the Canada Steamship Lines and during the summer months is also served by a.car ferry from Riviére du Loup on the south shore of St. Lawrence river. Several secondary roads and bush roads suitable for auto- mobile travel extend into the area from the 'two Provincial highways; of these, the most useful are from highway 16 to lake dos Côtes,.Baribeau lake, and David lake, and from highway 15 to Buteux lake, Chicane lake and lake du Basque. A network of roads along the alluvial valleys in the vicinity of Sacré Coeur pro- vides ready access to most parts of the area northeast of Saguenay river. In addition to these roads, numerous bush trails are useful once their location has been determined..... ;The most useful of these trails; now somewhat overgrown, follows an old telephone line from the road end at lake des Côtes to the bush road north of Malbaie lake. Examination of the map suggests that Saguenay river itself should be useful for travel within the area, but precipitous cliffs, which.flank the river in most places, make but little of the area accessible from it.. The only waterway providing reasonably easy travel within the area is the chain of eight lakes, from lake Lyonne to lake Druillettes. A good, short portage connects lake Buteux and lake Druillettes; Fleury, Honorat, Caron, and Buteux lakes, differ in elevation by only a. few feet, and are connected by short rapids down which empty canoes can be lined. A. portage.betWeen Jamay lake and Fleury lake apparently is seldom used and is rather obscure.. Portages between lakes Lyonne, Guay, and Jamay were not seen, but may well exist.

'.1-2887 2

The most satisfactory supply centres in, or close to, the area include Sacré Coeur and Tadoussac northeast of Saguenay river. Southwest of that river they include Baie Ste. Catherine, St. Siméon, and Petit Saguenay.

General Description of the Area

Precipitous slopes bordering most of St. Lawrence and Saguenay rivers bound the upland portions of the area, which is a part of the Laurentian up- lands. Although the upland in general. is. classed as a pene.plain, local relief in this map-area is moderate to high, averaging about 400 feet. Relief is lower in sections underlain by granite, except in areas close to Saguenay river. A ridge-and-valley topography is prominent in areas underlain by a complex of Grenville rocks and granite. Because dips are high in most places, hogback ridges are the most prominent landscape feature, but low cuesta-like ridges occur in the few places where. dips are low, notably in the area underlain by granite gneiss between lakes Honorat and Buteux.

Previous Geological Work

Faessler (1) examined parts of this and adjoining areas along the St. Lawrence during reconnaissance surveys in 1928 and 1929. .Greig (2) mapped the Bergeronnes-Pontgravé area, northeast of the present area, in 1941. In 1943, Ross (3) examined parts of Callières, Chauveau, Dumas, Sagard, and Saguenay townships. Miller (4) mapped the,St. Siméon area, immediately south of the pres-- ent sheet, during the summer of 1950.

p é and the (1) FAESSLER, Carl, Notes on the Geological Traverses between Beau 4 FIL 1 Saguenay River, in the Counties of Montmorency and Ghar~`ovoic; Que. Bur. Mines, Rept. Min. Oper. in the Prov. of Que. during the year 1928 (1929).

Geological Exploration on the North Shore, Tadoussac to Escou- mains; Que. Bur. Mines, Ann. Rept. for 1929, Pt. D (1930).

(2).. GREIG, E.W., Preliminary Report on Bergeronnes-Pontgravé Map-area, Charle- voix-Saguenay County; Que. Bur. Mines, P.R. No. 166 (1942); Final map, No. 629 (1947).

(3) ROSS, S.H., Preliminary Report on the Geology of the Sagard-Callières Re- gion, Charlevoix, Chicoutimi and Saguenay Counties; Que. Dept. Mines, P.R. No. 244 (1950)

(4) MILLER, M.L., Preliminary Report on St. Siméon Map-Area; Que. Dept. Mines, P.R. No. 252 (1951)

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GENERAL GEOLOGY

General Statement

The consolidated rocks of the map-area are igneous and metamorphic rocks of Precambrian age. About one-tenth of the area is underlain by Grenville- type metamorphic rocks, such as hornblende and mica schists and gneisses, and quartzites. The remaining rocks are chiefly granitic and occur as long, relatively thin layers with Grenville rocks, or as more or less separated masses. In general, the larger granitic masses are gneissic, especially close to their margins, although the central parts are commonly devoid of readily-apparent gneissosity. Pegmatite dykes are common throughout the map-area and appear to be genetically related to the granites. One large mass of highly quartzose rock termed "silexite" is of undetermined origin. The more extensive and continuous areas of Quaternary sediments occur inland in valleys or on low ground near St. Lawrence and Saguenay rivers.

Table of Formations

Pleistocene 'and recent gravel, sand, Quaternary CENOZOIC and clay

Silexite

Pegmatite Intrusive rocks ' Pink leucocratic granite

Biotite granite, gneissoid biotite granite, biotite granite gneiss PRECAMBRIAN

Hornblende schists and gneisses (including partly granitized equivalents) Grenville series Mica schists and gnoisses, quartzites (including partly granitized equivalents)

Grenville Series

The Grenville rocks of the area may be assigned to one or other of two units shown on the accompanying map. The mica schists and gnoisses, and quartzites, are derived from sedimentary rocks. Most of the hornblende schists and gneisses probably were also once sedimentary rocks, but some of them may haire formed in part by metamorphism of basic intrusive rocks. - a -

Mica Schists and Gneisses, Quartzites (including partly granitized equivalents)

These metasedimentary rocks are found mainly as three irregular masses in the southern half of the area. Two of these form parts of a crescent-shaped band, about half a mile wide, in the southwestern corner of the map-area. At the northeastern end of this band, hornblende gneisses and mica gneisses inter- f;inger, but within the band there is no interlayering of these two rock types on a mappable scale. The third metasedimèntary mass, a roughly triangular-shaped area in the vicinity of Lyonne and Malbaie lakes, is about four miles long. It terminates on the west against the mass of hornblende gneiss mentioned above, and on the east separates into two thinning and diverging "fingers" trending northeastward and southeastward, respectively, with granite gneiss between them.

. The micaceous metasedimentary rocks consist chiefly of rusty-weather- ingr highly-contorted, biotite-muscovite schists and gneisses shot through with irregular white pegmatites. Some layers have distinct oval to lenticular white "eyes", up to one inch long, which appear to be aggregates of sillimanite or muscovite, or both. Garnet is rare. Granitization (i.e., the process by which rock is made more like granite by recrystallization and by introduction of minerals such as quartz and feldspar) in some places has altered the rock to such an extent that it has come to resemble closely biotite granite gneiss,.from which it is distinguishable only with.difficulty. Micaceous metasedimentary rocks are found mostly in the band mapped near the western boundary of the map- area.

The Lyonne lake-Malbaie lake metasedimentary mass consists principal- ly of quartzite, which in most places is so highly granitized as to resemble a fine-grained, quartz-feldspar pegmatite. Mica gneiss occurs toward the western extremity of the mass. The quartzite is a dense-looking, white or light grey weathering rock, usually with a smoothly glaciated surface. Layering is absent or obscure, but locally the quartzites, particularly in the darker units containing some biotite, have a laminar parting which may be relict bedding. Feld- spathization is common and is shown by anhedral pink to flesh-coloured feldspar in short branching streaks.

Dykes and irregular masses of pegmatite are common in the gneissic rocks such as the mica and hornblende gneisses, but they are rarely seen in the quartzites. The massiveness and competence of the quartzites was not favour- able for the formation of larger bodies of pegmatite.

Hornblende Schists and Gneisses (including partly granitized equivalents)

Rocks with hornblende (or hornblende and biotite) in excess of 25 per cent and exposures with more than 25 per cent hornblende schist or gneiss have been included with the hornblende schist and gneiss unit on the accompanying map. Thus, many of the units shown on the map as hornblende schist and gneiss are actually largely granitic. In general, the thinner bodies of hornblende gneiss are the more. highly granitized.

Hornblende gneiss forms numerous thin bands around the borders of the three major granite bodies of the area, and the layers are more numerous and thicker the farther they are from the centres of the masses. Gross interlayering of hornblende gneiss, pink leucocratic granite, and biotite granite gneiss is,.characteristic of the border zones of the granite bodies. Interlayer- ing of hornblende gneiss and biotite granite gneiss on a -small scale is common in the mappable units of hornblende gneiss.

The hornblende-bearing rocks of the area are of diverse appearances. Some green or greenish-black rocks consist almost entirely of hornblende, but these are relatively rare. More commonly these rocks are granular with gneissic..structure only faintly.shown by a few needles or rod-like aggregates of nee- diés.°o.fhernblende. Large, irregular porphyroblasts of red garnet occur in a fëw'places. Hornblende porphyroblasts which. stand out.as knobby protuberances on the'weathered surface are rare.

Intrusive Rocks

Biotite Granite, Gneissoid Biotite Granite, Biotite Granite Gneiss

Three large, more:or less distinct bodies of this unit (referred to hereafter as biotite granite. :or biotite granite gneiss) oceur::in the area. Of these, the St. Etienne granite, on both sides of Saguenay river in the northern part of the area, is of batholithic dimensions; the other two: - the Sagard granite in the southwest corner west of Buteux lake, and the Roger Lake granite, in the south-central part - are much smaller than the St. Etienne body. Apart from these larger masses, much of the granitic rock outcrops as compara- tively narrow bands, chiefly in the hornblende gneiss. The .orders:. of the main bodies of granite are poorly defined, the masses being delimited for the .,host part by the greater incidence and thickness of layers of rocks of the Grenville type. The Sagard granite and the Roger Lake granite almost everywhere.she# pronounced gneissic structure, although in the Sagard granite gneissic structure ig. obscure near the centre of the mass. The concordant nature of these bodies is striking; nowhere is there any suggestion of truncation of the structure of invaded rocks by the granite bodies.

The lithology of the biotite granite gneiss is highly variable. In general these rocks are medium- to coarse-grained, pink or light grey, and consist of biotite, quartz, and feldspar. .TheSagard granite has a core that is pink in most places, whereas the edges of the mass are grey, probably a result of `contamination. The Roger Lake granite is grey in most places and shows gneissic struèture almost everywhere. The St. Etienne granite isiight__grey, coarse-grained, and massive, except near its borders, and is characterized by lenticular to. rregular clots of pink feldspar ranging from one-halr"to.one inch long, suggesting the descriptive name "pink-eyed granite". This- characteristic structure is evident on good clean exposures almost everywhere in the mass.

Pink Leucocratic Granite

Pink leucocratic granite is exposed as narrow bands alternating with usually broader bands of hornblende gneiss and biotite granite gneiss. Charac- teristically it is well jointed, and slopes underlain by it are covered with talus. An increasing amount of biotite in the leucocratic granite creates dif- ficulties in distinguishing it from the pink biotite granite; indeed from their 6

—close spatial relationship and Local• convergence in mineralogical composition, it appears that the two rocks are genetically related, the pink granite proba bly being but little younger than the biotite granite.

Pegmatite

Pegmatites abound in the map-area. They appear to be of two differ- ent types: one is pink or grey and consists of quartz and feldspar with minor amounts of biotite, and hornblende or.'magnetite; the other is grey or white and is mostly quartz and white or pale pink feldspar, commonly with muscovite, mi- nor biotite, and, in a few places, tourmaline.' '

The spatial arrangement and distinctive composition of the two varieties of pegmatite suggest that they are genetically distinct. The, pink and grey biotite pegmatite probably is related to the biotite granite and granite gneiss, whereas the white and .grey muscovite pegmatite is thought to be related to the garnetiferous biotite granite gneiss that occurs in the northwestern part of the St. Siméon area to the south (1) and extends northwesterly to just west of the southern third of the present map-area. The relative ages of the two, pegmatites is uncertain, but it has been suggested that the biotite pegmatite is younger than the muscovite pegmatite (2).

Silexito

A massive-looking rock consisting almost entirely of quartz and termed silexite is exposed in several white hills about half a mile west of the southern end of Druillettes lake. In places the silexite contains thin laminae of muscovite or short streaks of cream feldspar. Pale pink patches are proba- blÿ due to small amounts of; 'iron oxide. The rock is fairly well join d and as a result has an uneven weathered surface. On the largest hill greenish-black hornblende gneiss is exposed within the silexite mass as a band, twenty feet wide and several hundred feet long, which disappears under drift at both ends.

Cenozoic Gravels, Sands and Clays

Pleistocene and recent gravels, sands and clays are abundant throughout the map-area. Glacial drift is abundant in the upland sections and masks effectively most of the bedrock. In the southwestern corner of the area, chiefly south of Druillettes lake, a deposit 'of glacial drift with an irregular rolling surface ,covers all but a few hills. At lower elevations near Baie Ste. Catherine and'St. Etienne, 'and in the valley near Sacré Coeur, well-strat- ified deposits of sand and clay are common. Distinct terraces can be seen near Baie Ste. Catherine and St. Etienne, and they are particularly prominent around Tadoussac.

STRUCTURAL GEOLOGY

The map-area is underlain by a complex of granitic massifs and smaller sill-like bodies of granite intruded into an assemblage of gneissic* Grenville

(1) MILLER, M.L., op. cit., p. 5. (2) MILLER, M.L., op. cit., p. 6. rocks which now occur only as thin and discontinuous septa between the granite masses. The tabular habit of inclusions in the granites and the absence of structural discordance between elongation of inclusions and gneissic structure in granite gneiss around them suggest that the. Grenville rocks were gneis.se.s before the granites were emplaced, and.that the intrusion was not forcible:,'but rather by slow, gentle and "permissive" injections guided by structures in the older rocks. In the smaller intrusive bodies at least there was little thrust- ing aside of the wall rock. Probably some of the smaller granite bodies are metasomatic granites formed by replacement of pre-existing Grenville rocks.

Structural control of the position of the pegmatite bodies is striking. Pegmatites occur chiefly as sills of small extent and'except for some smaller bodies have strictly concordant contacts with the wall rock. The fact that pegmatites are rare within the large granite masses and that those that .do occur are'.of'the-Simpletype (consisting of feldspar, quartz, and mica, and little else) suggests that erosion has cut deeply into the cores of the granite massifs.

Gneissic structures in the Grenville rocks are invariably parallel to. the bedding at those few places where bedding can be seen. It is likely that the folds and gneissic structure. formed before intrusion by granite, since •iii many instances the gneissic structure appears to have guided the intrusive fluids. Folds in the Grenville rocks are suggested in several places, but they are relatively small and discontinuous. The folds are virtually isoclinal.

Aerial photographs show strong linears x throughout the area with the exception of the central part of the St. Etienne granite mass. Most linears reflect faithfully the gneissic structure.of the bedrock. Some linears that sharply transect directions. of gneissic structure mark zones of close jointing; others-mark loci of faults. One of the latter linears determines the elonga- ti.on.ofi,_the string of lakes from Jamay to Druillettes and at several placer in tre.fiel.d;,is marked by a zone.of brecciation up to 15 feet wide. Breccia zones are well exposed at the west end of the portage between Druillettes lake and Buteux lake, at the east end of Caron lake, and at the east end of Fleury lake. The exposure at the east end of Caron lake is particularly significant; here the fault is marked by a 15-foot-thick zone of breccia consisting of angular fragments of red granite in a matrix of greenish-grey, clayey gouge. The fault zone strikes N.65°E. and dips:820N., and one wall has slickensides plunging steeply east. A sé'cond fault is exposed on the southwest shorë Of-Saguenay river'opposite Anse.:de:la Boule as a breccia zone 100 feet thick. The breccia here consists of angular fragments of grey granite gneiss in a grey clayey gouge. A third fault sone,.alsb,mârked by breccia, is exposed on the east side of a. small hill of granite gneiss projecting above the drift in lot 1, Range Est Chemin Albert, Tadoussac.,township. Those faults are late stage adjustments which took place well after the consolidation of the granite bodies that they cut. The steep dip of the fault zones and the clean-cut breccias marking them suggest normal faulting. No mappable displacement.was observed along any of them.

Linear is used for a marked linear topographic feature without implication as to its origin. - 8 -

ECONOMIC GEOLOGY

Minerals of possible economic importance include mica, quartz, and uranium minerals. Sand,and gravel deposits and accumulations of broken rack suitable for ballast and fill are exploited for local use.

Mica

Of the several varieties of mica utilized in industry, muscovite and phlogopite are the most sought for. As sheet mica commands higher prices than ground mica, "books" (parallel aggregates of sheets) are desirable. :.In this map-area only the grey and white pegmatites in the southwestern part' contain appreciable quantities of muscovite. These white pegmatites abound in the band of mica schist end gneiss that roughly parallels the western boundary of the. area.. Although no large books of muscovite were seen in these pegmatites in the course of the field work, it is possible that detailed prospecting would result in the discovery of deposits of potential economic value. Some large books of muscovite were seen not far away, in the northwestern corner of the St. Siméon area (1). Biotitè was seen in large books in pegmatites along the south shore of Fleury lake, and is present in most of the pink pegmatites. Usu- ally it is- more abundant in those pegmatites that cut hornblende gneiss and un- doubtedly is at least partly a product of contamination.

Quartz

Quartz is used for glass making, sandpaper, polishes and scouring compounds, and in metallurgical operations. It is possible that the silexite in the southwest corner of the map-area might furnish quartz sufficiently pure and with such physical properties as to lend itself to these uses. However, • the demand of some of the uses is not great,• and quartz is of such common oc'- currence that an area remote from potential markets could hope to compete with other sources only if the material is especially desirable.

Uranium Minerals

In 1949 the discovery on the shore of St. Lawrence river, at a place about ten miles upstream from the southern boundary of the present area, of a pegmatite containing radioactive minerals resulted in the staking of many claims. The staked ground forms a belt extending roughly northwest from the original discovery to beyond lake aux Canards in the St. Simeon area and thence north- ward as far as David lake, the eastern extremity of which projects from .the west into the present area just south of the Sagard-Dumas township line. At the. southeast end of David lake three shallow test-pits have been sunk-in a 10-foot- thick, fine-grained, pink pegmatite sill in greenish-grey hornblende gneiss. The attitude of the sill and wall rock structure is variable, but on the aver- age'it strikes N.32°E. and dips 70°'southeast. Large clots of biotite are present where fragments of hornblende gneiss have been included in the pegmatite. Vaguely-bounded, greenish-yellow areas in the pegmatite resemble the pe- culiar greenish pegmatite in which uraninite occurs in the St. Simeon area.

(1) MILLER, M.L., op, cit.; p. 8. -- 9 -

The pegmatite: is said to be radioactive, but neither a radioactive mineral nor gossan was seen by the writer, although a sample said to be.from this pegmatite was tested by him in the fall of 1950 and found to be radioactive.

Without wishing to discourage prospecting for uranium in the pegmatites of this area, it may be pointed out that, in the,opinion of prominent in- vestigator.s,,.pegmatites have not yet been proved to be an .important source of, uranium." Page (1) states that uranium-bearing minerals in pegmatites "rarely oceiirin sufficient quantities to be economically important as a source of uranium. Die 'Madagascar pegmatites are the only ones that have furnished appreciable tonnages of uranium minerals". Lang (2) states that "no pegmatite deposit has been mined successfully for uranium or thorium in Canada, but some have been mined on a small scale in other parts of the world"., and goes on to de- scribe a number of Canadian deposits of uranium in pegmatites, including the discoveries in the Black Lake region of Saskatchewan most of which "sire under- stood to be pegmatite deposits or occurrences of radioactive minerals in schist and gneiss"(3).

Calcite Veins

Veins of calcite occur at several places in the area. Although none of these is known to contain any economically important mineral, they are mentioned here.

One exposure occurs in lot 1, range 2, Saguenay township, near the village of Baie Ste. Catherine, where a vertical vein of calcite two feet thick cuts directly across the gneissosity of hornblende gneiss. Large angular fragments of apparently unaltered wall rock are enclosed in the vein, which contains a few crystals of pyrite. In a road-cut on highway 15 about two miles southwest of the bridge over Canards river, calcite occurs in a breccia cementing angular fragments of cherry-red leucocratic granite; here also a few crystals of pyrite were noted in the calcite matrix.

Sand and Gravel'

Deposits of sand and gravel of potential value occur near Baie Ste. Catherine, St. Etienne, Sacré Coeur, and Tadoussac. These deposits afford an almost unlimited supply of road-building material, and have been used exten- sively for road construction in the area. In general, no deposits of gravel suitable for road-building are to be found at elevations greater than 450 feet. Most glacial drift is unsuitable for road-building because of high clay content, large boulders, and variable nature and extent. During the summer of 1951 only one small gravel pit was in operation. It is about a mile and a half northeast

(1) PAGE, L.R., Uranium in Pegmatites; Econ. Geol., Vol. 45, No. 1, 1950, pp. 12-13.

(2) LANG, A.H., Summary Account of Canadian Uranium Deposits; Can. Inst. Min. Met., Bull., Vol. 43, No. 460, Aug. 1950, p. 428.

(3) LANG, A.H., op. cit., p. 432. - 10 -

of Malbaie lake. Gravel from this: pit was used in the construction of the pri- vate bush road being extended to and beyond Chicane lake.

Rock Ballast and Fill

'Ready-broken, easily accessible rock ballast occurs in a talus slope resting against well-jointed pink leucocratic granite exposed on a hillside on the east side of highway 15 about two miles southwest of the bridge over Canards river, and was used in the construction of the ferry dock at Baie Ste. Catherine. A quarry in grey granite gneiss on the west side of highway 15, about a mile and half north of Tadoussac, was the source of fill used in the construction of a Canada Steamship Lines dock at Tadoussac. Here, however, blasting was necessary to break up the rock.