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QUEBEC DEPARTMENT OF NATURAL RESOURCES

MINERAL DEPOSITS SERVICE

RADIOACTIVE OCCURRENCES IN THE GRENVILLE OF

MONT LAURIER — CABONGA DISTRICT

Ministère des Richesses Nature}les, Quebec r;. LA DtJCI: Nï`c:N'; t;T tON TECHNIQUE

Date:...21 ~. ../ .q: No

L. Kish

1975 INTRODUCTION

The predominant portion of Quebec's radioactive occurrences are found in the Grenville geological Province. The occurrences can be grouped into radioactive districts by their areal concentrations, such as can be outlined around Kipawa lake, in the Gatineau Park area north of , in a broad belt NNW of Mont Laurier, and in several other places along the north shore of the St-Lawrence river.

The subject of this report is the district that extends north of

Mont-Laurier and east of Cabonga reservoir. The geological map that accom- panies this report is limited by longitudes 75° and 76°45' and latitudes

46°45' and 47°30' and covers an area of about 4000 square miles. Subsequent-

ly this map is referred to as "the compilation map".

PREVIOUS WORK

The first published geological reconnaissance work and the earliest reference to radioactivity in the area is by Retty (1934) (p. 147), who noted that the "pegmatite dykes are a possible source of radioactive minerals".

Systematic geological mapping on a scale of one mile to one inch by Quebec Department of Natural Resources started around Cabonga reservoir in 1959. Preliminary reports used in the compilation are by Laurin (1960,

TABLE OF CONTENTS

Page INTRODUCTION 1

Previous Work 1 Sources of information 2

GEOLOGY 3

Rocks of the Pre-Grenville Group 4 Rocks of the Grenville Group 5 Migmatites 6 Intrusive rocks (except granite and pegmatite) 7 Granite 7 Pegmatites 7 Structural relations 9

RADIOACTIVE OCCURRENCES AND ANOMALIES IN THE MONT LAURIER - CABONGA DISTRICT 11

Canadian Johns-Manville Property 11 Mont Laurier Uranium Mines Inc. Property 14 Gulf Minerals Ltd. Property 17 Scandia Mining and Exploration Ltd. 17 Other occurrences 19 Baskatong occurrences 20 Capri Mining Corp. Ltd. Property in Sicotte township 21 Stream sediment Geochemistry in the Cabonga Area 21 Airborne Radiometric Survey east of 23

SUMMARY OF CONCLUSIONS 24

References 27

MAP Mont Laurier - Cabonga Compilation map (in pocket) Page

ILLUSTRATIONS

Figure 1 Plasticly deformed Grenville gneisses 28

Figure 2 Boudinage in the Grenville gneisses 28

Figure 3 Partially mobilized feldspathic quartzite from a radioactive zone 29 Figure 4 Autoradiograph of the feldspathic quartzite 29 Figure 5 Hand specimen of a radioactive pegmatite 30 Figure 6 Autoradiograph of the radioactive pegmatite 30 1961), Sabourin (1963) and Jacoby (1966, 1968). The eastern half of the district was mapped on a scale of four miles to one inch by the Geological

Survey of Canada (Wynne-Edwards et al., 1966).

The radioactive mineral occurrences of Quebec, known up to 1955, are summarized in a report by Shaw (1958).

SOURCES OF INFORMATION

The sources of the data presented in the compilation map are diverse government publications, assessment work on file with the Mineral Deposits

Service of the Department of Natural Resources, and the writer's field work during the summer of 1973.

Samples for elemental analysis were chosen from the hand specimens collected in the field. These are representative with the restrictions des- cribed in the text.

The distribution of the radioactivity in the field was studied by a scintillometer, which discriminates between the energies of the characteristic gamma rays from thorium and uranium isotope series, and so permits on-the- spot estimates of the Th/U ratios. -o4541V.!011.....M

GEOLOGY

The Mont Laurier - Cabonga radioactive district is in the Grenville

Province and the majority of the rocks are highly metamorphosed gneisses, which have been deformed in a plastic state and completely recrystallized.

Some of these gneisses clearly derive from sediments, and the origin of some others is unknown. The common igneous rocks are granite and pegmatite.

Syenite and gabbro are present in minor quantities.

The compilation map presents the geological relations in a simpli- fied form, and groups the gneisses into two major associations:

One association is characterized by the abundance of those rocks, which derive from mature siliceous and aluminous sediments, or calcareous chemical sediments. Conforming to the general usage in the Gatineau area, the rocks of this association are referred to as the rocks of the Grenville

Group.

Another association consists of quartzofeldspathic gneisses or

granitic gneisses, which are devoid of the metamorphic equivalents of mature or chemical sediments. These rocks are stratigraphically below the Grenville

gneisses and are thus assigned to the Pre-Grenville Group. Table of Formations

Precambrian Pegmatite Pink granite Syenite Intrusive rocks Gabbro

Gneisses of the Paragneisses, quartzites Grenville Group Calcsilicate rocks, marble, "Metamorphic pegmatites", granulites

Gneisses of the Quartzofeldspathic and Pre-Grenville granitic gneisses Group

For a detailed discussion on age relations in the Grenville the

interested reader is referred to the article and the exhaustive list of refer-

ences given by Wynne-Edwards 0972),

ROCKS OF THE PRE-GRENVILLE GROUP

The formations of the Pre-Grenville Group are exposed in a broad

belt that extends from Lecointre lake southwestward and includes the areas

around Bark lake, and Cabonga reservoir. They are made up of quartzofelds-

pathic rocks which have a restricted variation of mineral composition and

texture.

In the Cabonga area the hornblende-biotite granitic gneisses are

thinly layered (Laurin, 1960, 1961). Layering is shown by "differences in texture" or by "the variation in the proportions of certain minerals such as... biotite or hornblende". These rocks are well exposed along the road that joins highway 58 with Cabonga dam.

The Pre-Grenville formations, which are exposed between Lecointre lake and Petawaga lake, are "leucocratic gneisses of granitic and quartz-dioritic composition" (Wynne-Edwards et al., 1966, pp. 11-12). These gneisses are des- cribed as "equigranular, grey or pink in color and well foliated".

The Pre-Grenville formations north of Baskatong lake were mapped by

Jacoby (1968, p. 3) as quartz-dioritic and granitic greisses.

ROCKS OF THE GRENVILLE GROUP

In this association of formations a great variety of gneisses of

sedimentary origin is present, many of which derive from mature siliceous and

aluminous sediments and chemical precipitates. Most of these rocks were

recrystallized in the amphibolite grade of regional metamorphism, but in some

places granulite facies mineral assemblages are found. The compositional

variation is abrupt on outcrop scale.

Grenville gneisses occur in abundance in the eastern part of the

Mont Laurier district and east of Cabonga reservoir. Quartzites are associated

with biotite paragneisses, and sillimanite garnet gneisses south of Patibre

lake, in the south east corner of the area. The quartzites are coarse in

grain, and the quartz is dark-colored and intensively cracked. Ortho-quartzite,

biotite quartzite and feldspathic quartzite are the main varieties. Some of the coarse feldspathic quartzite is often mistaken for a granitic pegmatite.

East of Cabonga reservoir the quartzite is interlayered with silli- manite -garnet gneiss and graphite-bearing, rusty weathering gneiss in a sequence that is several thousand feet thick. The sillimanite gneiss may contain up to 25% of garnet.

Marble and calcsilicate rocks are especially abundant around Baskatong reservoir.

Part of the south east corner of the area in underlain by granulite- grade gneisses which were assigned by We nne-Edwards (1966) to a "green-rock complex" (shown on the compilation map). Granulite--grade rocks are not favour- able for radioactive exploration and they are not discussed further in this report. The amphibolite-grade gneisses are described in some details in the chapter on mineralized zones,

MIGMATITES

Migmatites(also referred to as injection gneiss by some authors) occur in both Grenville and Pre-Grenville gneisses. In some gneisses around

Cabonga reservoir "layering is pronounced by introduction of leucocratic material" (Laurin, 1961, p. 6).

In the Grenville formations of the Baskatong area the migmatite mapped by Jacoby (1968, p. 7) is a "mixture of paragneiss and granite... in all ratios". In the Pre-Grenville gneisses some quartz-diorite gneisses are thoroughly injected by "stringers of pink granitic material".

INTRUSIVE ROCKS (EXCEPT GRANITE AND PEGMATITE)

Diverse intrusive rocks form discrete units in the area: syenite, monzonite and gabbro are present in relatively small quantities and are not shown separately on the compilation map.

GRANITE

A pink granite cuts both the Grenville and the Pre-Grenville gneisses.

This rock is a fine-to-medium-grained, two-feldspar granite with less than 5% dark minerals.

PEGMATITES

By definition a pegmatite is "an exceptionally coarse-grained igneous rock... usually found... at the margins of batholiths", and represents" the last and most hydrous portion of magma to crystallize..." (Glossary of Geology,

AGI, 1972, P. 253).

In the Mont Laurier area pegmatite is a loosely used collective term for coarse, quartzofeldspathic rocks, and, in fact, very few of these rocks satisfy the above definition. A large part of the so-called pegmatitic rocks are in intimate mixture with gneisses and have transitional contacts. The pegmatitic fraction contains gneisses in various stages of resorption: they may be inclusions, or their former presence may be indicated by a biotite-rich

clot, or simply by a change in color or grain size. Evidence are plentiful

to conclude that this complex mixture iS the product of high temperature meta-

morphic processes, which resulted in partial melting of the pre-existing rocks.

In the present report, the rocks crystallized fro:i this locally generated

liquid are distinguished from pegmatite proper and are named "metamorphic

pegmatites".

a) "Metamorphic pegmatites"

Local concentrations are present in both Grenville and Pre-Grenville

gneisses. The "metamorphic pegmatite" commonly associated with the Grenville

rocks is white on the fracture surface and is creamy-yellow on the weathered

surface. The rock is medium to coarse in grain, the texture is coarse granitic,

.rather than pegmatitic, and individual crystals never attain huge size. The

essential constituents are quartz and microcline, and minor biotite is unevenly

distributed in the rock, Pyrite is a common accessory mineral, is oxidized on

the weathered surface and gives a rusty-dotted appearance to the outcrop.

The relation between the radioactivity and the white metamorphic

pegmatite is discussed in the next chapter.

The essential constituents of the "metamorphic pegmatite" associated

with the Pre-Grenville quartzofeldspathic rocks are similarly quartz and

K-feldspar, but this latter is pale pink in color. Magnetite is the common

accessory mineral. The grain size ranges from medium to coarse, and locally graphic texture is observed. Because of the restricted compositional varia- tion of the Pre-Grenville gneisses, the differences between the pink "meta- morphic pegmatite" and the associated gneisses are less pronounced than those of the white "metamorphic pegmatite" and the Grenville gneisses.

In some outcrops of the Grenville - Pre-Grenville contact zone the white and pink "metamorphic pegmatites" are mixed.

In general, the gneisses cut by "metamorphic pegmatites" may be either migmatitic or non-migmatitic, which suggests that the migmatitization and the generation of the pegmatitic liquids are two distinct processes, separated in time.

b) Pegmatite proper

Different from the "metamorphic pegmatites" is the pegmatite proper of the district. This pegmatite has crystallized from a homogeneous liquid, and is emplaced at a considerable distance from its locus of generation. The dikes and veins have sharp contacts and those with sufficient thickness are zoned. The grain size is coarse and graphic exsolution is common. The pegma- tite contains variable amounts of plagioclase beside the K-feldspar, and allanite and magnetite are the common minor minerals. Radioactive varieties of the pegmatite are described in the next chapter.

STRUCTURAL RELATIONS

Structural trends are indicated by the compositional layers and by the foliation of the gneisses. The gneisses of the Grenville and Pre-Grenville Groups are complex- ely deformed. Plasticly deformed rocks are illustrated in Figures 1 and 2.

A regional fold pattern is evident from the compilation map. The Grenville formations occupy a basin, which has been compressed into broad folds, the axes of which strike northeasterly. Northeast trending plunges indicate that the major fold east of the Cabonga reservoir is a syncline and that at

Lecointre lake is an anticline.

Tight isoclinal folds are observed on outcrop scale mainly whithin the area of the Grenville gneisses. The apparent thickness of the metasedi- mentary formations does not correspond to the thickness of the pre-metamorphic sedimentary sequence.

The contact relations between the rocks of the Grenville and Pre-

Grenville Groups are confused by the metamorphism and tectonic events. -

In the contact zone, which may have been a major unconformity, the rocks of both groups are infolded and, in apparent contradiction, Grenville gneisses are included in older, quartzofeldspathic gneisses. This is also the area, where white and pink metamorphic pegmatites are mixed. Near Cabonga reser- voir, the contact zone is marked by a narrow erosional valley, which separates granitic gneisses from marble and cale-silicate rocks, and the "metamorphic pegmatite" is scarce. In the southeast corner of the area, the infolded contact zone is relatively wide and ill defined, and dirty quartzites are abundant near the base of the Grenville Group. Some of these quartzites may have derived from quartz-rich conglomeratic material. RADIOACTIVE OCCURRENCES AND ANOMALIES IN THE MONT LAURIER - CABONGA DISTRICT

Radioactive occurrences studied in some detail by exploration companies are described in the first part of this chapter, government geochem- ical and geophysical studies are reviewed in the second part.

CANADIAN JOHNS-MANVILLE PROPERTY (SEE JMV ON THE COMPILATION MAP)

The property is located north and west of Patibre (Axe) lake in

Leman Township. The work, which started in 1968, includes detailed mapping surface work (trenching, blasting), and diamond drilling. Presently two

groups of claims are retained by the company: the larger group is north of

Patibre lake, and the smaller is west of this lake.

The two typical examples described below are from the area, north

of Patibre lake:

1.) In a layered sequence the Grenville gneisses are represented by silica-

rich paragneisses and calcsilicate rocks. Layering is well marked by

compositional changes and this indicates that in spite of the high

grade regional metamorphism there was no active migration of the calc-

alkali elements. Free quartz is present in each layer, including those

with diopside and scapolite. Table 1 shows the mineralogical and some

elemental variations in a 30-foot sequence, with layers foot to 2

feet thick. The biotite paragneiss in the central part of the sequence

is highly radioactive but the U and Th contents of the bordering scapo-

lite-diopside gneisses are of no economic interest. The radioactive

TABLE 1.

Mineralogical and elemental variations across a radioactive zone of the JMV property

P.P.M. Ratio Minerals Th U Y Sr Th/U Y/Sr Scapolite-gneiss K-feldspar,Plagiocl.(An38) 65 62 31 966 1.05 0.03 Scapoli.te,Diopside, Quartz,Hornblende, Sphene

Porphyroblastic, Quartz,K-feldspar, 1803 20300 280 99 0.09 2.82 ji radioactive biotite-para- biotite,sphene apatite, 1009 9760 182 279 0.10 0.65 w samples gneiss layers uraninite,(minor plagio- 566 6550 73 226 0.09 0.32 N selected clase) '

Leucocratic Quartz,K-feldspar, 59 88 27 450 0.64 0.06 siliceous layer biotite,diopside with minor diop- side

Scapolite-gneiss Quartz,Scapolite 51 147 32 996 0.34 0.03 diopside,Hornblende Sphene,biotite

White,"metamorphic Quartz,K-feldspar, 118 366 21 382 0.32 0.06 pegmatite" biotite

K-feldspar K-feldspar 36 87 14 463 0.41 0.03 porphyroblast of the radio- active zone paragneiss is porphyroblastic, and the foliation is well marked by a

streaky alignment of the biotite. Quartz and feldspar form a fine-grained

matrix to the K-feldspar porphyroblasts,which are up to 1 cm in diameter.

Sphene is a common constituent of the rock. The radioactive mineral is

uraninite, and it is present in tiny cubes, which are surrounded by

rusty-brown haloes. Autoradiographs indicate the presence of uranium

in the form of tiny streaks in hair cracks, and parallel to the foliation

of the gneiss. A yellow stain of uranophane is present in the fractured

surface-specimens.

2.) In a second type of association biotite paragneiss and dirty quartzite

are mixed with "metamorphic pegmatite". In these rocks quartz, K-feldspar

and biotite are the main constituents, but the proportion of these mine-

rals, and the grain size vary from one type to another. Radioactive rocks

are the paragneiss and the intermixed "metamorphic pegmatite". The analyses

in Table 2 compare some compositional characteristics of a radioactive

gneiss and the K-feldspar of the gneiss. Uraninite is the radioactive

mineral, its appearance and alteration characteristics are the same, as

described above.

TABLE 2.

Partial analysis of a radioactive mixed gneiss and its K-feldspar from the JMV property

P.P.M. Ratio Th U Y Sr Th/U Y/Sr

Mixed gneiss V-1 233 1555 35 160 0.15 0.22

K-feldspar from V-1 37 334 10 280 0.11 0.03 The company's property west of Patibre lake is in the complexely infolded contact zone of the Grenville and Pre-Grenville formations, where inclusions of quartzite and calcsilicate rocks in the quartzofeldspathic or granitic gneisses may be seen.

This is the only place in the area, where 1 to 2 cm thick veinlets of black uranium oxide were found. Analysis indicates a complex uranium- oxide, with traces of Ti, Nb, and Y. Although they are exceptionally rare, these veinlets indicate the presence of a secondary vein-type uranium mineral- ization in the area.

In summary, on the JMV property the Th/U ratios of the radioactive zones examined are around 0.1, and range from 0.3 to 1.1 in layers bordering these zones. The tenor of Sr varies up to 350 ppm in the highly siliceous environment, and reaches about 1000 ppm in the rocks with diopside and scapolite.

The low tenor of Y of the radioactive zones means presumably a general scarcity of the RE elements. Diamond drilling shows the same rapid variation of the tenor of uranium in depth as is observed in the outcrop.

MONT LAURIER URANIUM MINES INC. PROPERTY (SEE MLU ON THE MAP)

The main activities of the company are in Perodeau township. Explo- ration work started in 1970 around Cornes lake, and progressed northward up to the border of the JMV property. The evaluation work, including diamond drilling, extended over three zones: the H-zone, (for Hanson); the T-zone

(for Tom Dick); and the N-zone (for North). Over these zones the claims are in good standing. The N-zone is adjacent to the JMV property. The radio- activity is in a dirty (biotitic and feldspathic) quartzite, in which biotite

may mark the foliation. Table 3 gives the partial analysis of some dirty

quartzites collected from highly radioactive pits.

TABLE 3.

Partial analyses of some radioactive dirty quartzites from the N-Zone of the MLU property

P.P.M. Ratio NO. Th U Y Sr Th/U Y/Sr

N-34D 4525 6000 74 49 0.75 1.52

N-60 2776 2647 42 20 1.05 2.08

N-66 3592 2575 48 48 1.39 0.99

The radioactive minerals, readily visible in the hand specimens,

are thorian uraninite and uranothorite. The uraninite cubes are 1 to 2 mm

in size and are randomly scattered in the rock. Microscopic examination

indicates marginal alteration of the grains. The uranothorite is present in

brownish, soft, altered prismatic crystals. This mineral is metamict and

yields no X-ray diffraction pattern.

In places, the yellow stain of uranophane is seen in hand specimen and migration of some radioactive material into fractures is indicated by

the autoradiographs. Figures 3 and 4 illustrate the hand specimen and the

auteradiograph of a feldspathic quartzite. -16 -

Uraninite may be concentrated in part of the radioactive outcrop and in some other part the uranothorite is more abundant. The variation in

Th/U ratios shown by the analyses are caused by the varying proportions, uneven distribution, and the degree of alteration of the radioactive minerals.

This variation is observed within short distances,

The T-zone is in the hilly area east of the outlet of Magin (Tom. Dick) brook

The proportion of the biotite paragneiss and calcsilicate rocks to the quartzite is higher in the T-zone than in the N-zone. "Metamorphic pegmatite" is mixed with the gneisses. The radioactive minerals are thorian uraninite and uranothorite. The common accessory minerals are sphene, graphite and molybdenite.

The analyses of selected radioactive samples (see Table 4) indicate somewhat higher Th/U ratios, than those of the N-zone.

TABLE 4.

Partial analyses of some radioactive mixed gneisses from the T-Zone of the MLU property

P.P.M. Ratio Th U Y Sr Th/U Y/Sr T-2 1887 1250 29 129 1.51 0.23

T-3 2477 1326 42 103 1.87 0.41

T-5 1243 948 35 68 1.31 0.51 The H-zone is situated about 5 miles south of the T-zone. Field measurements indicate that Th predominates over U in the radioactive outcrops.

In conclusion, the presence of the radioactive elements in several mineral phases causes a more pronounced variation in Th/U ratios on the MLU property than on the JMV property. A general increase of the Th/U ratios is indicated by the averages on a regional scale from north to south.

GULF MINERALS CANADA LTD. PROPERTY (SEE GLF ON THE MAP)

A claim group retained by the company is located east of Patibre lake, in Franchêre township. Here radioactive zones were located by geophys- ical survey, and were evaluated by diamond drilling. The prospecting work was carried out in 1970-,71. The rocks are Grenville gneisses, among which quartzite and sillimanite gneisses predominate, and carbonate rocks are rare. The radioactive zones are in dirty quartzite and the "metamorphic pegmatite" fraction is scarce. The quartz of the radioactive samples is dark, and fractured. The visible radioactive mineral is uraninite, and the Th/U ratios of the specimens measured are very low.

SCANDIA MINING AND EXPLORATION LTD. (SEE SCD ON THE MAP)

Scandia Mining and Exploration Ltd. explored the area west of

Mitchinamecous reservoir. A major part of the work has been carried out since 1968, and under agreements with other exploration companies, among them

Allied Mining Corp. Ltd., United Asbestos Inc., and Transterre Explorations

Ltd. In contrast to the above described prospects, the radioactivity on the Scandia property is in pegmatite proper. The dikes are up to 120 feet wide and have sharp, well-defined contacts with the country rock. The main minerals are quartz, K--feldspar, and plagioclase (An22-24). Biotite, allanite and magmetite are concentrated locally. Zircon is a common accessory mineral.

The grain size varies from coarse to very coarse. Zoning can be observed from the margins inward by an increase in grain size in the tenor of K-feldspar.

Graphic exsolution texture is coirnuon.

Partial analyses of four radioactive specimens are summarized in

Table 5.

TABLE 5

Partial analyses of radioactive pegmatites from the SCD property

Percent P.P.M. Ratio K20 Na20 Th U Y Sr Th1U Y/Sr i 1 1 3.15 3.00 1019 1.924 73 112 0.53 0.65 _ _: _r__ 1/B 3.70 4.35 1311 556 46 257 2.35 0.18 --r------i 2 0.71 5.91 3267 1709 ( 72 l 178 1.91 0.40

3 0.74 4.63 1124 665 1 61 193 1.69 0.32 Two varieties of pegmatites are listed in Table 5: specimens 1 and 1/B are two-feldspar pegmatites, and specimen 2 and 3 are rich in plagio- clase. Radioactive mineralization is found in both types. The radioactive minerals are allanite and a variety of uranium oxide. A hand specimen and its autoradiograph are shown in Figures 5 and 6. Allanite is present in up to 3 cm long blades, which are surrounded by anastomosing cracks. An allanite concentrate was found to contain 7122 ppm Th, 2327 ppm U, 535 ppm Y and 294 ppm Sr.

The U-rich grains are metamict and their cubic form suggests that the mineral belongs to the uraninite-thorianite series.

The proportions of the radioactive minerals vary in different parts of the pegmatite and this is one reason for the variation of the Th/U ratios in the hand specimens analysed.

OTHER OCCURRENCES (SEE "R" ON THE MAP)

Several less intensively prospected radioactive zones are known in the area. At Connor falls, on Mitchinamecous river (Gatineau 50 township), radioactive pegmatite has been prospected by Guardian Mining Ltd. Presently the pit is abandoned. The pegmatite is similar to that on Scandia property, however, it is of small extent.

In Gatineau 61 township, Phelps-Dodge Corp. of Canada Ltd. investi- gated some radioactive outcrops several years ago. Minor cubes of thorian uraninite were found in some paragneisses and in the mixed granitic material. Beside those described on the preceeding pages, mining claims are in force in Gatineau 61, 62, 71, 72, Chopin, Leman, Franchère, Gatineau 50 and Laurentides-Labelle 40 townships.

BASKATONG OCCURRENCES

The earliest prospected radioactive mineralizations in Quebec are distributed in a broad area that extends north-northwest of Ottawa and is outlined by the Ottawa - Grand-Calumet Island-Baskatong triangle. In this report the area is named Gatineau Park radioactive district. With a few exceptions the localities described in a previous account on the radioactive occurrences of Quebec (Shaw, 1958), fall in this district.

For comparative purposes some radioactive outcrops around Baskatong lake were examined. Partial findings are summarized here. In general, marble and cale-silicate rocks in the Gatineau Park district are far more abundant than in the Mont Laurier area.

Radioactive occurrences around Baskatong lake are numerous. A meta- morphic pyroxenite from Baskatong township, and a pink granitic pegmatite from

Lytton township are illustrative examples. (I) The metamorphic pyroxenite is composed of calcite, diopside, actinolite. Thorite is the radioactive mineral, and the Th/U ratio of an average specimen is 30. Uranium is present only in traces and the Sr content is around 5000 ppm. (2) The pegmatite has about 10% magnetite, 5580 ppm Th, 160 ppm U, and 3180 ppm zirconium. CAPRI MINING CORP. LTD. PROPERTY IN SICOTTE TOWNSHIP

This is the most extensively studied property around Baskatong

lake. It is situated east of Gatineau river and about 2 miles north of Grand

Remous, and was prospected between 1968 and 1971, however, only a small

number of the claims has been retained by the company.

A north northwest trending contact that runs along the eastern

shore of Curtis lake, a prominent topographic feature of the property, sepa-

rates igneous rocks of dioritic, quartzmonzonitic and syenitic composition

(east of the contact), from metasedimentary formations (west of the contact)

Calcsilicate rocks predominate among the latter. A dark green crumbly tactite,

composed of diopside and variable proportions of calcite, K-feldspar, plagio-

clase, sphene, apatite and quartz, is commonly radioactive. The radioactive

mineral is present in minute yellow-brown grains, which are intensively altered

and do not yield a diffraction pattern. The mineral is probably a (Th, U) -oxide.

In the tactite samples analysed, Th is about seven times more abundant than U,

Y varies between 9 and 24 ppm, and Sr ranges from 246 to 392 ppm.

In summary, the radioactive mineralizations in the Baskatong area are

characterized by high Th/U ratios and an abundance of carbonate rocks.

STREAM SEDIMENT GEOCHEMISTRY IN THE CABONGA AREA

Stream sediment sampling by the Quebec Department of Natural Resources

east of Cabonga reservoir covered an area of 1800 square miles. The results

of the analyses are listed in a report by Kelly et al. (1972) and are illus-

trated on maps in form of rolling means (RM) contours. Areas of RM contours of 6 elements with ppm values as shown in the table below are reproduced on the compilation map of this report.

U RM contour higher than 2.4 ppm 2% of the population Zn " 79 5% Cu " 30 2% Pb " 29 5% Co 23 4% Ni " 22 4%

The anomalous RM values are within the limits of the Grenville formations and are concentrated near Cabonga reservoir and at Lecointre lake.

Cabonga anomaly - Several small uranium RM-anomalies were indicated near the contact of the Grenville and Pre-Grenville formations east of the south end of Cabonga reservoir. Narrow pegmatite dikes with three times background radiation were located by a ground scintillometer survey. The pink granitic and syenitic pegmatite dikes cut the gneisses of the contact zone.

Lecointre anomaly - RM-anomalies at the northwest end of Lecointre lake were checked by scintillometric traverses. Here calcsilicate rocks of the Grenville

Group are in contact with Pre-Grenville granitic gneisses. The contact zone is cut by dikes of pegmatite in a similar way to those at the Cabonga reservoir.

Chips collected from the radioactive part of the pegmatites contain 610-1920 ppm U and 73-118 ppm Th.

At the southeast extension of the lake the exposure is poor and during a brief check the cause of the anomalies was not found. -23-

AIRBORNE RADIOMETRIC SURVEY EAST OF GATINEAU RIVER

An airborne radiometric survey that was conducted by the Geological

Survey of Canada in 1971, covers about 800 square miles east of Gatineau river.

The results were published in the form of computer-plotted contour maps. The geographic limits of the survey and the contours that outline anomalous areas of Th

(from 200 counts up) and U (from 120 counts up) are shown on the compilation map. High Th and U counts were registered around Montagne lake (W of Mitchi- namecous reservoir), and high U counts were shown around Bressani lake and north of Patibre lake. A summary of the follow-up work is given by Char- bonneau (1973).

Among the intensively studied prospects, the trenches and surface- blasting of the JNV property north of Patibre lake are well shown by high U contours. There is no overlap of the areas covered by the geochemical survey

(W of Gatineau river) and the airborne radiometric survey (E of Gatineau river) and a comparison of the anomalous indications of the two surveys is presently not possible. SUMMARY OF CONCLUSIONS

1. In the Mont Laurier - Cabonga radioactive district the gneissic rocks

belong to two major associations of formations: a) the Grenville Group, in which metamorphic equivalents of mature sedi-

ments and chemical precipitates are present in abundance; and b) the Pre-Grenville Group, which is made up essentially of quartzofelds-

pathic gneisses of granitic and quartz-d io ritic composition.

2. Coarse granitic and pegmatitic rocks occur with the gneisses of both

Groups. a) "metamorphic pegmatites" were crystallized from liquids generated locally

by partial melting of the gneisses. They are intimately mixed with the

gneisses and have diffuse contacts. b) pegmatite proper is emplaced as dikes or veins, and has sharp contacts.

The dikes of sufficient thickness may be zoned.

3. The rocks of the Grenville Group occupy a basin. It has been compressed

to broad folds. The fold axes strike northeast.

4. Geochemical anomalies, radiometric U an Th anomalies, and the locations

of known radioactive occurrences fall in the areas underlain by amphibo-

lite grade gneisses of the Grenville Group, In the granulite-grade,

dry assemblages radioactive indications were not found.

Geochemical U anomalies tend to be concentrated in the noses of major

folds of the Grenville gneisses and near the contact zone of these gneisses with some older rocks. 5. Radioactive mineralisations are found (a) in metasediments and associated

"metamorphic pegmatites"; (b) in pegmatite proper, (c) rarely as veinlets.

a) Biotite paragneiss and dirty quartzite commonly contain the radioactivity

in the mineralized zones of the southeast part of the district. Visible

radioactive minerals are uraninite, thorian uraninite, uranothorite and

a common alteration product which is thought to be uranophane. If "meta-

morphic pegmatites" are mixed with the gneisses of the radioactive zones,

they carry the same mineralization as the gneisses. b) In pegmatite proper, such as those found in the northeast part of the

district, allanite and thorian uraninite mark the radioactive zones. c) Vein-type U-oxide is known from one locality and although economically

not significant, it indicates that relics of a vein-type U-mineralization

exist in the area.

6. The radioactive zones of the Mont Laurier district are characterized by

the: a) patchy, discontinuous nature of the radioactivity, and by a b) variation in Th/U ratios.

7. The abundance of metamorphic rocks of distinctly sedimentary composition

and a persistence of compositional layering indicate that the metamorphism

has resulted in an isochemical reconstitution of the rocks and that there

has not been any intensive migration of the major elements.

The effect of the metamorphism on the migration of the minor and radio- active elements is less evident. It is very likely that the variations

in ratios, and the patchy character of the mineralization, are not primary

features and are due to a differential redistribution of U and Th during

the regional metamorphism. High P-T laboratory studies on the solubility

of U and Th with varying PH20 and Pc02 are presently in progress. These

experiments may reveal the causes of the variations.

8. Favourable areas for U prospecting are those occupied by dirty quartzites

and biotite paragneisses of the Grenville Group, and by pegmatitic rocks.

The distribution of some anomalies also suggests as target areas the

noses of major folds and the Grenville - Pre-Grenville contact zone.

Because of the intricate structural relations, a prerequisite to systematic exploration is a very detailed geological mapping.

Standard prospecting methods to search for U in the district should be used with precautions. The dispersion of U in the soil and stream sedi- ments is widespread and the cause of the geochemical anomalies should be found in the bedrock before one contemplates drilling.

In radiometric surveys, the limited penetration of gamma-rays should be considered. Estimates of U and Th contents from scintillometric measurements are valid only if equilibrium exists in the isotope series of these elements.

In certain- cases of disequilibrium (that may occur in the district in spite of the Precambrian age of the radioactive rocks) the scintillometric anomalies do not reflect anomalous concentration of U and samples collected from zones of high "kicks" may show disappointingly low U values by chemical analysis. REFERENCES

CHARBONNEAU, B.W. (1973) Ground Investigation of the Mont Laurier Airborne Radioactivity Survey, Geol. Survey Can. Paper 73-1, Part A.

JACOBY, R.S. (1966) Baskatong Reservoir Area (East Half), Quebec Dept. of Natural Res. Prelim. Report 558.

(1968) Baskatong Reservoir Area (West Half), Quebec Dept. of Natural Res. Prelim. Report 572.

KELLY, R. et al. (1972) Geochimie des Sédiments de Ruisseau, Région Est du Réservoir Cabonga, Ministère des Richesses naturelles, Québec, Rapport 5-138.

LAURIN, A.F. (1960) Turquetil-Emard Area, Quebec Dept. of Mines Prelim. Report 424.

- (1961) Dieskau-Loubias Area, Quebec Dept, of Mines Prelim. Report 452.

RETTY, J.A. (1934) Upper Gatineau Region, Quebec Bureau of Mines, Annual Report for 1933, Part D.

SABOURIN, R.J.E. (1963) Bourbonnais - Limousin Area, Quebec Dept. of Natural Res. Prelim. Report 509.

SHAW, D.M. (1958) Radioactive Occurrences of the Province of Quebec, Quebec Dept. of Mines Geol. Report 80.

WYNNE-EDWARDS, H.R., et al. (1966)

Mont Laurier and Kenlpt Lake Map-Areas, Quebec Geol. Survey Can. Papers 66-32.

WYNNE-EDWARDS, H.R. (1972) The Grenville Province, In "Variations in Tectonic Styles in Canada", Ed. Price and Douglas, Geol. Assoc. Can. Spec. Paper Number 11. Fig. 1 - Plasticly deformed Grenville gneisses

Fig 2 - Boudinage in the Grenville gneisses Fig. 3 - Partially mobilized feldspathic quartzite from a radioactive zone (1:1)

Fig. 4 - Autoradlo.graph of the above specimen Fig. 5 - Hand specimen of a radioactive pegmatite (1:1) A = Allanite, M = Magnetite

• • r

Fig. 6 Autoradiograph of the above specimen