- 85 -

la Ronge-Wollaston Belts Base Metals Project: Geo!]e Hills, Johnson and Kaz Lakes

and Geikie River Areas by W. Coombe

In 1977 an examination of several zinc-lead, lead and copper occurrences,

hosted by Aphebian Wollaston Group metasediments of the Wollaston domain, was under-

taken. Recent advances in the understanding of sandstone-type zinc-lead deposits

prompted the writer to focus on two widely separated and contrasting areas of mine-

ralization. In the Sito Lake area (Fig. 1) there are at least 5 known zinc-lead

occurrences within an area of 200 km2 . The mineralization is restricted to a

quartzite membeY of the lower part of the Wollaston Group of pelitic and semioelitic

gneisses (see Potter, this volume).

The George Lake area, approximately 80 km2 (where Falconbridge Nickel Mines

Ltd. have outlined an uneconomic deposit of zinc-lead of 5 million tons averaging

2.65 percent Zn and 0.35 percent Pb (Karup-M¢11er and Brummer , 1970)) was mapped at

a scale of 1:12,000 by the author, utilizing previously cut grids. The mineralized

zone occurs near the top of a thick grey quartzite unit, in the lower part(?) of

the stratigraphic sequence.

In addition to these areas, the author visited the following (Fi g . 1) :

(a) Hills Lake (zi~c-lead)

(b) Johnston Lake (Marina showing) (lead)

(c) Kaz Lake (copper)

(d) Geikie River area (copper-molybdenum in boulders)

George Lake Area

The rocks of the George Lake area belong to the Compulsion River Fold Belt of

Pyke and Partridge (1967), Karup-M0ller (1970), Karup-M0ller and Brummer (1970) and

the Courtenay Lake-Cairns Lake Fold Belt of Scott (1970).

The area mapped by the author (Fig. 2) extends from Courtenay Lake in the south-

west, to George Lake in the northeast and is largely covered by muskeg. Outcrops

are restricted in general, t o areas adjacent to rneltwater channels e.g. George Lake

and Causier Lake channels.

Predominant meta-sediments, with minor intrusives and ?volcaniclastics occupy

a synform trending 055-060° (Assuming no other repetition of strata they fo rm a

single synform). An estimated thickness of the sequence (Fig. 3) in the southeastern

limb of the synform at George Lake i s 5000 m. The geology of the northwestern l imb

D . D E] . .

- 86 -

A rho b c:i1co Fo, rnor,on

IH•h• •onl

Wollo1ton G roup Sup roc r uuo l Roe lu

IAohob,on)

104'

O 20 •o,m 0 20M,

Explanat ion

• O uon z11e -hos te d t •l"I C -leod occvrren ce~ 1 G• o•ge Lo ~• 2 Hil u Lo._ , ) Joh"ISOl'I lClitt 4 S,•o lWi 5 5,•o :; ; · 6 5·•o :sw1 7 G eo rge a Foole Lo._• 9 Segm,erH Lot\•

+ MePo ·coni;, l cm• r c:ne o nd m e1 0 - a rll.ose ~h o sre d coop•, occur, e nc• 1

l ll:ofu1• t o\:e 2 Ko z: Lai.• J. J cu ,1 c e l..o k • 4 J u >\ o La••

• Robb,r La ite uron, 1,1m m ine

& Kitr Loh· uron1um dei;:0,11

• Dudd,,d ,ge Lake, meto .. cong l ome, o re Ol"ld quorr1 :1e-hosted u,o n ivm 1- cooDt r) occ.v r r e nce X Mud l o kP molybd e n1.1m occurte ric e

Bo,emenl Granite !Remobil,zed A rch eon '?) 0

Fig. 1 . Location map, s howing distribution of selected mineral deposi t t ypes within the Wollaston domain. Areas investigated during the s tudy: I, Sito Lake area; II, George Lake area; III, Hi l ls Lake; IV, Johnson Lake; V, Kaz Lake; VI, Geikie River area.

is l ess c l early understood . due to lack of outcrop (concentrated i n the Causier Lake

a rea) and control (no cut lines) . Estimated thickness i s in exc ess of 1000 m.

The Southeastern Limb . On the southeastern l imb 'way-up' structures i ndicate (i) a

general f i ning of lithotypes towards the northwest and (ii) a change i n charac ter

from terrestrial / shallow marine t o calcareous marine sedimentation.

Lower Me t a - a rkose Unit . The Lower Meta-arkose unit is exposed at the end of

Courtenay Lake and can be traced intermittent ly northeastwards . It appears to

thicken i n tha t direc tion , ranging from approxima tely 1000 min the s outhwest

to 2000 min the northeast.

• A,p-py-po-eo-• occ1,,11,.,,o

0

0

- 87 -

Nott "'••ttern ,...,.,

)ohnson Riv., b•rtlotith (.,. .. .....i ........... ,

J km

2 Mi

LEGEND

~ . . 6J ~ EITJ [] j."';"1 t.:..:..J

10J'A5'

SI••• ""'ut

G,.,. ouanci•• unit

Fig . 2. Geological sketch map of geology of the George Lake area.

The unit comprises a elastic member and an extrusive (?intrusive in part)

member. The elastic member which predominates , includes a variety of lithofacies,

ranging from cross-bedded me ta-arkoses, through graded s cour-and-fill units to

boulder meta-conglomerates and breccia-meta-conglomerates. All are characterized

by a pink-cream (to pink-red) colour and an abundance of accessory magnetite and

ilmenite. Cross bedded units are commonl y less than 15 cm in thickness, and

indicate tops to the northwest. Boulder meta-conglomerates are usually less

than 2-3 m thick and composed of slightly flattened clascs up to 30 cm in length

(average length: width ratio~ 3:1) . Boulder: matrix ratios are commonly high

s.w.

. . . . . . . ..

.,/ .,/

..,.,,, ...---

----- -- --

...........

- 88 -

N.E.

... .. . .

UPPER META- ARKOSE UNIT

CALCAREOUS QUARTZITE UNIT

Asp, PY, po, go, sp

CALCAREOUS META-ARGILLITE UNIT

~ PY, PO SLATE UNIT

- PY, po ~ Sp, ga, py, po

. . . . . . . e.O."'c, o·.~c,·•o

- 89 -

(3: 1). Meta-conglomerates are poorly sorted and polymictic; predominant clasts

are of whitish-grey feldspathic quartzite with lesser vein quartz and granite

cobbles . Pebbly lenses in the troughs of c ross-beds are coonnonly composed of

quartz and (K-) ~eldspar clasts less than l cm in diameter.

Amphibolite occurs at least at two horizons within the Lower Meta-arkose

unit. The lower amphibolite is fairly heterogeneous and comprises predominant

amphibolite with epidosite lenses and sheets and intercalated semipelite and

pelitic gneisses . Some amphibolite layers resemble hyaloclastite, but no obvious

pillows were observed. The upper amphibolite is more homogeneous, lacking marked

pelit ic interlayers, and ranging from a massive amphibolite to amygdaloidal and

podifo rm t ypes. These two amphibolite units can be traced continuously across

the area by their high-relief magnetic expression.

The southeastern contact of the Lower Meta-arkose unit is grarlational over

a width of up to 1000 m with Biotite (after amphibole) granite. Towards the contact

the meta- arkoses become less distinctly cross-bedded, and relic bedding is evi-

denced only by thin lenses of oxides . The field relations suggest that the

granite is intrusive , although the contact is in part, sheared. Shear zones,

up t o 100 min width, transect t he basal beds and trend 055-060°, approximately

parallel t o t he bedding. Where the s hear zone cuts the porphyroblastic facie s,

the meta-arkose becomes an augen gneiss, with quartz-sericite matrix.

The uppermos t 600 m of the Lower Meta-arkose unit appears to be only present

towards the nor t heast, and is we ll exposed at the southern end of Souter Lake

where it comprises massive and subordinate thin-bedded (less than SO cm) pink

(to maroon) ' glassy' quartzites and feldspathic quartzites. A distinctive

quartz- sericite s chist , with porphyroblasts of andalusite and biotite after

staurolite (Scott, 1970), i s f ound approximately 240 m below the top of the

unit. Likewise, layers of meta-argillite and grey quartzi te also occur. They

are up to 1 m but an average 10 to 20 cm in thickness and form beds less than

15 m thick.

Grev Quartzite Unit . The Grey Quartzite unit i s distinguished by not only the

absence of pink meta-ar koses but, apart from minor amounts within gr ey biotitic

quartzites of the uppermost Lower Meta-arkose unit , coi ncides also wi th the

appearance of sul phides in the sequence. It thins from appr oximately 1000 min

the vicinity of George Lake to less than 350 ma t the north end of Court enay

Lake.

The basal bed is a black slatey meta-ar gillite, approximatel y 80 m thick,

- 90 -

that contains abundant porphyroblasts of chiastolite at i t s base, and becomes

graphitic and pyrite-pyrrhotite bearing, towards the top. Ahove this bed the

unit is mostly composed of a variety of grey to grey-white, and rarely white

feldspathic quartzites and quartzites with intercalated meta-argillites. The

unit is characterized by rapid facies changes both along strike and across it .

Immediately overlying the black slar.ey meta-argillite are approximately 150- 200 m

of thin-bedded grey, pyrrhotite-bearing, biotite quartzites and interlayered meta-

argillites. These quartzites commonly show graded bedding and scour-and-fill

structures. The overlying 350 mis unexposed; frost - heaved boulders contain a

number of pebble and boulder meta-conglomerate layers. Clasts of quartz and

feldspar predominate with lesser meta-argillite and pebbly quartzite . The quart-

zite clasts are up to 15 cm in length.

The uppermost 500 m (at George Lake) is comprised of an interlayering of

several quartzite types which range from graded, gritty units a few centimetres

thick, to garnetiferous biotitic varieties that show lensing from 1.5 m t o less

than 10 cm. Meta-argillites (generally l e ss than 25-30 cm thick) are common

within this part of the sequence both as graded tops and discrete thinly layered

beds. Quartzites with beds less than 1 cm in thickness are also present.

The ore zone is unexposed, but frost-heaved boulders from this zone differ

from the rest of the unit in that they are more massive and finer textured.

They vary from a grey to grey-white to whi te feldspathic quartzite. The follow-

ing description of the zcne is extracted from Karup-M~ller and Brummer (1970) :

1, The mineralized zone occurs approximately 25-30 m below the top of the

Grey Quartzite unit.

2. The zone averages 30-40 min width, and extends for approximately 600- 700 m

along strike.

3. Mineralization is concentrated in a grey quartzite, and appears to decrease

with increasing biotite content.

4. The grey quartzite contains up to 15 percent feldspar, minor biotit e,

muscovite and rare garnet. The grey quartzite becomes a white quartzite wi t h

decreasing feldspar, biotite, muscovite and garnet. The biotite quartzit e

contains variable amounts of biotite, garnet, muscovite, rare tremolite and

hornblende.

5. Sphalerite is the predominant sulphide, minor galena and pyri te are oft en

present. Pyrrhotite is erratically distributed.

6. The sulphides occur as disseminated specks, averaging 1 mm in diameter,

and rarely as hair-line cross-cutting fracture fillings.

- 91 -

7. The mineralized zone has been traced south-westerly at least 2.5 km.

Slate Unit. The Slate unit overlies the Grey Quartzite unit and at George

Lake is approximately 500 m thick thinning to half this thickness at Courtenay

Lake. The lowermost member is a grey meta-argillite, approximately 25 m thick,

that overlies biotite (-garnet) quartzite of the Grey Quartzite unit. The Slate

unit is composed of a number of lithofacies, but slates and slatey argillites

predominate. These are very fine-grained, dark-grey to black, thin bedded in

part, and varyingly graphitic. They co!Dlllonly contain up to 1 to 2 percent

pyrite, both as disseminated blebs (framboids) and later fracture-fills. In

detail they vary from dark siltstone to mudstone. The slates occur as two

distinct bands, reflected by high magnetic relief which average 80-100 min

thickness and are occasionally garnetiferous. Distinctive chert bands, cherty

quartzites, greywacke (tuff), and minor laminated meta-argillite occur as inter-

beds. The chert is well bedded, striped, and up to 20-30 m thick. Individual

beds average 1-2 cm in thickness, and alternate light and dark grey. The

cherty quartzites are more thickly bedded, cream-buff, and very fine-grained.

Up to 1 percent pyrrhotite is the predominant sulphide in the cherts and cherty

quartzites, occurring as disseminations. Although thin the chert beds appear

continuous over at lease 4 km.

Calcareous Meta-argillite Unit. The Calcareous Meta-argillite unit is approxi-

mately 800 m thick at George Lake, and thins slightly to the southwest. It

comprises predominant meta-argillaceous laminites with calcareous layers, and is

typically light to medium grey, delicately laminated (1-2 llllll scale) and siliceous.

The calcareous component may range from less than 5 percent to consistent calc-

silicate and marble bands. A distinctive unit along the northwestern shore of

George Lake is a very fine-grained well laminated (1-5 llllll) greenish rock,

composed of alternating green calcite-tremolite and quartzose meta-argillite

with some thin layers of white, calcareous, feldspathic quartzite. Elsewhere,

light brown layers, less than l m thick, of quartz-feldspar-garnet-tremolite

(scapolite) occur. Highly calcareous light grey layers, 1-2 m thick, are

occasionally present, especially near the top of the unit in the southwest.

Dark grey and black meta-argillites and slatey meta-argillite~ are present

as layers within the Calcareous Meta-argillite unit. Northeast of Courtenay

Lake, dark grey and black meta-argillites and slatey meta-argillites are inter-

layered with cherts and cherty quartzites that resemble those in the Slate unit .

They present high-relief magnetic signatures, which enable the horizon to be

traced intermittently to the northeast. Near George Lake the cherts and cherty

- 92 -

quartzites appear to be absent.

A meta-argillite bed near George Lake, exposed along the northwest shore

of the small lake, 1000 m northwest of Souter Lake contains abundant arseno-

pyrite. The arsenopyrite is present as fine disseminations (earlier) and

coarsely-recrystallized porphyroblasts (later). In places it comprises up to

50 percent of the rock over a few centimetres, but probably averages less than

5 percent. It is associated with abundant pyrite, pyrrhotite and minor galena

and sphalerite. Arsenopyrite-bearing quartz veins anastomize throughout the

bed, and there does appear to be a marked concentration towards the veins.

The same association is also seen 5.8 km along strike to the northeast,

where the zone appears to be continuous along strike for 120-150 m. At this

locality fracture-fill relationships were observed by the author. Grab samples

* from this zone, taken by E.F. Partridge ran up to 8 percent Pb .

Calcareous Quartzite Unit. The Calcareous Quartzite unit appears to be restric-

ted to the northeast part of the area, and possibly thickens northeasterly into

the Spence Lake region. It is approximately 350 m thick northwest of George

Lake, and thins out about 2.4 km to the southwest where it may be truncated by

the Upper Meta-arkos e unit. Though heterogeneous, the unit i s characterized by

white calcareous, massively bedded feldspathic quartzites, up to several meters

thick, interlayered with laminated siliceous argillite, calc-silicate and impure

marble. Northeast of the area are distinctive brown-weathering intraformational

carbonate breccias and near Spence Lake apparent dessication cracks were obser-

ved. In general these occur in beds less than 50 cm to several meters thick.

Upper Meta-arkose Unit. The Upper Meta-arkose unit appears to be at least 600 m

thick, and comprises predominant pink and pink-grey medium-grained meta-arkoses.

These are commonly massive, but occasionally show light grey and pink colour

banding on a scale of 1-2 cm.

The basal beds, especially to the southwest, are formed by distinctly banded

calcareous meta-arkose, up to 50 m thick. Alternating 1-2 cm thick layers are

rich in actinolite and epidote and contain traces of calcite.

The Northwestern Limb. On the northwestern limb of the synform outcrops ar e confined

to an area southwest of Caus ier Lake. The creek flowing southwesterly f rom Causier

Lake follows the contac t between two subtly different pelitic units.

Northwest of the creek, the 'northwescern pt lites' ar e t ypically mottled red-brown

* DMR Assessment fil e 64E12SE0021

- 93 -

and dark-grey weathering, phyllitic to. schistose rocks which include variable amounts

of garnet and sillimanite and ubiquitous biotite and muscovite. They are generally

massive, although some thin (up to 15 cm) more psammitic (silty?) bands occur.

White, tremolitic quartzite that forms a massive bed approximately 30-50 m thick is

exposed along the creek. To the northwest it becomes interlayered with the pelites.

White, muscovite-bearing pegmatite invades the pelites, as sheets up to 10-15 m thick

sub-parallel to the layering/foliation. Thes~ sheets are commonly sheared and

granulated.

The heterogeneous 'southeastern pelites', which differ from the northwestern pelites by containing little garnet and sillima.nite, by being gritty in character and

by being interlayered with cherts, cherty-quartzites and calc-silicates, outcrop south-

east of the creek. For approximately 300 m southeast from the creek, the predominantly

biotite-muscovite pelites, contain a variable proportion of grit-sized clasts (quartz

and felsic fragments?). In some thin units very angular clasts (?meta-arkose) reach

dimensions of more than l cm. Layering is present locally in these rocks and the

entire sequence may represent a greywacke-turbidite succession. Southeast of the

gritty pelites, the rocks are also characteristically pelitic, with thin psammitic

bands, but here dark green-black amphibole may form up to 20 percent of the rock.

These are thought to represent the equivalent of the Calcareous Meta-argillite unit

farther southeast.

Pyrite and pyrrhotite are disseminated in trace amounts throughout, but are more

abundant in the more siliceous layers.

Structure and Metamorphism. Bedding is well preserved throughout t he area, and primary

sedimentary structures and textures can be readily identified.

In addition to bedding (s0

) two ages of foliation (S1

and s2) are cot!lllonly developed. s

1 is parallel to s

0, and trends 050-060°, except in two isolated loca-

lities where it is axial planar to tight, shallow, southwesterly plunging F1

folds.

The F1

folds were found near the south end of Causier Lake (within the northwestern

pelites) and northwest of George Lake (within the Calcareous Meta-argillite unit).

They possess subvertical axial planes, and are presumably s ynchronous with the major

synform of the area. Locally a rodding lineation (L1) i s parallel to F1fold axes.

s2 , a strain-slip cleavage, is present throughout the area, in the cores of minor Z-style F2 folds. The F2

structures plunge steeply northeast and have sub-vertical

axial surfaces trending 035-0li0°.

No significant faults were identified. Numerous narrow shears, parallel to s1,

- 94 -

are present throughout the area. These are expecially prominent towards the base of

the Lower Meta-a rkose unit , and within pegmatites that invade the northwestern pelites

of the Causier Lake area ,

Metamorphic conditions appear to range from the upper greenschist to the uppe r

amphibolite facies. Generally there appears to be an increase in grade towards the

southeastern and northwestern margins of the area.

Indicator minerals include muscovite, garnet, tremolite-actinolite, andalusite,

staurolite, 'hornblende ' , and sillimanite.

l. Along the southeastern margin, dark green-black amphibole is predominant within

the amphiboli te horizons. Rare pelitic interlayers are coarse-grained and gneissic.

2. Within the upper part of the Lower Meta-arkose unit, chiastolite, andalusite and

s taurolite have developed as porphyroblasts within iron and alumina rich pelitic

interlayers.

3. Garnet is widespread through the area.

4. Tremolite-actinolite is the predominant amphibole within calc-silicate horizons

of the Calcareous Me ta-argillite unit.

5. Muscovite is sparingly present within rocks of the southeastern limb, but

abl.l;ldant in pelites of the northwestern limb.

6. Sillimanite is c ommon within the 'northwestern pelites' of the Causier Lake area

The mai n me tamorphic event appears to have been approximately synchronous with

F1

. Rotation of sillimanite knots occurred duri ng F2

.

The Bills Lake Zinc-Lead Occurrence

The Hi lls Lake Zn-Pb occurrence (Fig. 4) lies within the Morell Lake (W ~) area.

The geology of the area has been described by Chadwick (1966). In the vicinity of

Hills Lake there are two major rock units . Granitic rocks, which are part of the

northwestern flank of the J ohnson River ba tholi th, occupy much of the area. Itmne-

diately in contact with the gr ani tic r ocks (and pres umably unconformable upon them)

a t Hills Lake i s a s eries of pelitic and semipe litic gneisses containing some impure

quartzite layers. The pelites a r e c ommonly gr aphit i c , and often garnetiferous. Over -

lying (?) these gneisses is a seq uence of meta- arkosic and calc-silicate rocks.

Numerous mineralized boulders have been discovered, over an a r ea of approximately

SOOm x 200 m, at the south end of the Hills Lake. These average l ess than one meter

i n maximum dimension and are sub-angular. They are predomi nantly medium- to coarse-

grained ' quart zit e ' and vary from light grey (least mineralized) to dark buff -brown

(highl y mineralized). The 'quartzite ' contains a high percent age of fel dspar (40-50

57°34'

- 95 -

103· 55'

103°55'

~ Wolloston G roup met ased iments f+"""J G ran itic rocks - largely 'Johnston L±_J Ri ver Bat hot i th' ( assumed basement)

® Mineral ized boulders

/ Em conductor

Fig. 4 . Location of Hills Lake Zn- Pb occurrence. Geo l ogy after Chadwi"ck (1966)

percent) and va=ies from an equigr anular, sugary- t extured rock to a ' br eccia' . The

' breccia ' is composed of large angular feldspars ( ?porphyrobl asts) , 3-4 mm in diameter ,

and quartz grains set in a finer quarrzo- feldspathic matrix. It is uncertain whether

t his ' breccia ' is of depositional, me tamorphic o r tectonic origin.

Mineralization consists of sphalerite and mi nor galena in association wi th

pyrite, pyrrhoti t e a nd magneti t e . Spha l erite (_dark black variet y) and magnetit e are

predominant . The sul phi des occur as f ine and coarse di sseminations throughout boc.h

- 96 -

the equigranular quartzite and 'breccia'. In addition slip planes coated with

pyrite, sphalerite and magnetite are abundant, both concordant and discordant to the

weak foliation.

A diamond drill hole near the southern end of Hills Lake intersected 3 percent

* Zn over a core length of 3.6 m. The host rock is described as 'feldspar-biotite-hornblende rock with indistinct banding'.

The Marina Lead-Zinc Occurrence, Johnson Lake

The Marina occurrence is located on the northwestern shore of Johnson Lake

(Fig. 5), on the northwestern flank of the Johnson River Batholith (Scott, 1969), an

assumed Archean basement inlier (Money et al., 1970), the margins of which suffered

mobilization during the Hudsonian. Samples of granite from the Marina occurrence

and adjacent area yield a Rb/Sr whole rock isochron indicating an age of 1717 ± 68

m.y. i.e. late Hudsonian (Cumming and Scott, 1976).

Briefly the Johnson River Batholith comprises gneissic granite, whereas the

overlying Wollaston Group metasediments are formed predominantly by pelitic and meta-

arkosic rocks with local calc-silicates (Scott, 1969).

The Marina showing oc~rs in a 'quartzite' in direct contact with the catacla-

sised augen granite. At the contact with the mineralized 'quartzite', the granite

is cream-pink weathe~ing whereas elsewhere it is pink-red weathering. The contact

itself is exposed in two outcrops and is somewhat obscure. In one outcrop there is

little evidence of a chilled margin, and the contact is marked by an increased amount

of pegmatite, which locally encloses 'xenoliths' of semipelite, whereas in the other

it is marked by a narrow (10 cm) zone of chilled granite with abundant quartz strin-

gers, and in places a biotite-rich selvage. A pod of near-massive fluorite occurs

at the contact, together with abundant amazonite-bearing pegmatite.

The 'quartzite' bed varies in width from approximately 3 m to 15 m, this varia-

tion possibly being in part original, but probably being largely due to cross-cutting

by the granite. The 'quartzite' itself is white weathering, coarse-grained and

comprises approximately 70 percent quartz, 25-30 percent feldspar and 1-2 percent

biotite. It is partly stratified, due to alteration of coarser- (pebbly?) and finer-

grained beds. The quartz grains are commonly flattened in a direction sub-parallel

to the cataclastic fabric in the granite. Minerali zation consists largely of medium-

to fine-grained disseminated pyrite or marcasite, galena and sphalerite. Galena pre-

dominates and is found as disseminations, as concentrations in thin layers (? parallel

* DMR Assessment File 64El20020

57• 25'

- 97 -

+

+

~ Wollaston Group

{+ + +1 Granite , includes _.,-.- Em conductor

104• 10'

+ +

+ +

+ + + +

+ + + +

+ + +

+

+ + + + + + + +

O I 2 km ..., ______ _

O Mi .

104• 10'

metaseciiments

57• 25'

Johnson River Batholith

e Areas of mineralized quartzite bo~ders Fig. S Location o( Johnson Lake Pb-Zn occurrence. Geo l ogy after Scott ( 1969)

to bedding) and as segregations filling discordant thin fractures . Pyri t e/marcasite

commonly coats small vugs within the ho s t rock .

The mineralized quartzite is invaded by numerous sheets of amazonite-bearing white

pegmatite . It is in sharp contact to the northwest with a dark semipelitic to peli tic

biotite gneiss, which elsewhere near t he contact carries trace to 2 percent of gra-

phite and abundant garnet. These graphitic pel ites form a strong e l ectro- magnetic

conduc t or which has enabled the contact zone to be traced to the southwest (Fig . 5.)

- 98 -

The Kaz Copper Occurrence

The Kaz occurrence (Fig. 6) is one of a number of similar copper prospects in

an area of approximately 25 km2 The rocks belong to three units (Scott, 1973) . In

the northwest are cordierite-sillimanite gneisses, which possibly represent the base

of the Wollaston Group in the area. Above these are meta-arkoses, which actually

show all gradations from meta-arkoses t o calcareous meta-arkoses to biotite-actino-

lite rocks, calc-silicates and marbles, and arkosic 'meta-conglomerates', which are

the host rocks to the mineralization at Kaz.

Many variants of the 'meta-conglomerates• exist, some of which are clearly con-

glomeratic in aspect whereas others are better described as 'nodular'. True meta-

conglomerates are t ypically 'candy-striped' and composed of flattened white, fine-

grained arkosic(?) cla~ts in a pink arkosic matrix. Occasionally the clasts are

somewhat more angular, and the rock approaches a breccia. The 'nodular' rock is

essentially a pink-cream to pink weathering meta-arkose with white 'nodules' of

coarse-grained feldspar-quartz-amphibole. These nodules are generally round, but

exhibit a range of shapes. They average 6-10 cm in diameter. Their origin is not

clear ; they possibly represent clasts or concretions, however, they do appear to be

different from irregular pods of pink-red pegmatitic neosome that are also locally

present. In the mineralized zones the 'meta-conglo•erates' are invaded by narrow,

straight-walled, pegmatites.

The mineralization is disseminated and consists of vis i ble chalcocite, native

copper, "azurite" and "malachite". Covellite and bornite occur in trace amounts. The

available assay data indicate mineralized zones, 1 m thick, that lie parallel to the

bedding. These zones contain 1-2 percent Cu. Chalcocite and native copper also occur

within pegmatite at Kaz Lake and elsewhere in the area chalcopyrite and bornite bearing

pegmatites are reported (Rath and Morton, 1969; Scott, 1973). Presumably these

represent remobilized copper segregations .

At Kaz Lake, numerous mineralized angular boulders have been located. These

boulders are of pink and grey, equig ranular meta-arkose. Scott (1973) notes that

these boulders contain chalcopyrite-galena, chalcocite-bornite and chalcoci te-

chalcopyrite, There appear to be two basic types: (i ) pink meta-arkose with dissemi-

nated chalcopyrite-galena (- s phalerite) and minor magnetite and (ii) grey meta-

arkose with disseminated pyrite-galena (-spha lerite) and mi nor magneti t e . None of these

mineralizations has been located i n outcrop.

56° 55'

56° .52'

- 99 -

0 I

104" 55 '

+ Cu - c. c . in 'meta - conglomerate' and meto - arkose

• Cu - c.c . in boulders of obove

o Ga - c . c . boulders

G Ga - c.p. boulders

2 km

I Mi .

[EZJ Predominantly meta - orkose , minor ca lc - silicate fifto] Metoconglomerote ~ Pelitic gneisses (? basal Wolloston Group }

Fi g. 6 . Location of ~halcocite-native copper occurrence~ in the Kaz Lake are3. Geology after Scott ( 19 73 ) .

- 100 -

Comparisons with Other Copper Occurrences in the Area. Similar chalcocite-native

copper mineralization occurs at Janice Lake and Rafuse Lake in 'meta-conglomerate'

and at Juno Lake chalcocite-native copper-chalcopyrite mineralization is present in

a possible outcrop of pink meta-arkose.

In addition to the 'in-place' mineralizations, a variety of mineralized boulders

have been located. At Juno Lake, meta-arkose contains covellite, chalcocite, bornite,

malachite, ilmenite, hematite and spinel. At Rafuse Lake, as well as 'meta-conglome-

rate' containing chalcocite-native copper mineralization, two boulders of a mafic-

ri ch 'biotite granulite', containing galena-chalcocite-malachite-azurite-pyrite are

present (Scott, 1973).

The writer suggests that these mineralizations may all have their source within

the same 'meta-conglomerate'-meta-arkose sequen~e. Furthermore there seems a dis-

tinct possibility that the mineralization is stratiform, if not essentially strata-

bound, and that the variation of assemblage is a product of local zoning, as exempli-

fied below:

'meta-conglomerate'

chalcocite

native copper

(covellite)

(bornite)

(chalcopyrite)

pink meta-arkose

(chalcocite)

(native copper)

chalcopyrite

galena

(sphalerite)

magnetite

grey meta-arkose

(chalcocite)

galena

pyrite

increasing Fe/Cu ratio

Geikie River Copper-Molybdenum Occurrences

•

During 1967 E.F. Partridge prospected the Geikie River area (Fig. 1) and dis-

covered a l arge number of mineralized boulders over a down-ice trend of SO km and a

width of approximately 5 km. Detailed prospecting carried out the fo llowing year in

two areas within the trend, s ub sequentl y led to the discovery of molybdenum mi nera-

liza t ion at Mud Lake . Partridge logged the majority of mineralized boulders as

" quartzite " and "feldspathic quartzite". These carry a trace to minor amounts of

one or more of the following: disseminated pyrite , pyrrhoti te, chalcopyrit e and

mol ybdenit e .

In 1977 the more accessible part of the mineralized boulder trend, approximately

5 km s outh of t he Geikie River was visit ed. Outcrop i s spar se and no minera lization

- 101 -

has been found in situ. The area is underlain by biotite gneisses and rneta-arkoses

(Chadwick, 1968) and the writer observed outcrops of graphitic pelitic gneisses

(?lower Wollaston Group) in the vicinity of the boulders. The mineralized boulders

themselves are generally angular-subangular, uniform light grey, massive, medium-

grained equigranular meta-arkos e with occasional coarser-grained zones, which possibly

repres ent anatectic fractions. Mineralization is remarkably uniform in a large num-

ber of boulders, and comprises disseminated chalcopyrite, with minor pyrite, molybde-

nite and bornite(?). Chalcopyrite is very evenly distributed and forms up to 1-2

* percent of the rock. Typical assay values returned 0.5-1 percen t Cu. Predominantly , the sulphides are intergranular, average 0.5 DDll diameter, but tend to show some

segregation into anatec.tic fractions.

Some Aspects of the Mineralization and Metallogeny of the Wollaston Domain

Base metal mineralization is widespread throughout the Wollaston domain (Fig . 1)

and is, in large part, stratiform in nature. Available evidence suggests that much

of the mineralization is essentially 'syngenetic ' with local modifications due to

Hudsonian events.

Ray (1974, 1975) , Gilboy (1975) and Potter (this volume) have recognized a cohe-

rent stratigraphy in the central part of the Wolla s ton domain. The Wollaston Group

supracrustals lie unconformably upon Archean granitic basement and comprise basal

pelites and semipelites (often graphitic) with subordinate quartzites, overlain by

meta-arkoses and calcareous meta -arkoses and interlayered calc-silicates . To a large

extent mineralization reflects the stratigraphy and is particularly concentrated in

the basal sequence:

(a) In the graphitic pelites pyrite-pyrrhotite-graphite zones occur, often in c lose

proximity to basement. The graphitic pelites are commonly invaded by anatectic

pegmatites that carry miner values of copper, molybdenum and uranium . Sibbald et al.

(1976) have suggested that these represent syngenetic concentrations remobilized

during the Hudsonian orogeny. In addition, the Key Lake uranium-nickel mineraliza-

tion is a s s oc iated with graphitic metasediments in the lower part of the basal

sequence (Ray, 1976; Dahlkamp and Tan, 1977).

(b) Quartzite members of the basal succession carry zinc-lead minera lization. This

t ype of mineralization is apparently r es tricted t o the Sito Lake a nd George Lake

areas( ? regional zoning).

* DMR Assessment File 64El2NW004

- 102 -

The origin of these deposits remains controversial. Harper (1975) drew attention

to the similarity between the Sito Lake occurrences and the Eocambrian deposits of

Scandinavia (e.g . Laisvall, Vassbo) which have been described by Grip (1967, 1973).

Other occurrences of this type include the Triassic deposit of Largenti1 re, France

(Foglie"rini et al., 1965; Samama 1968), the Cretaceous deposits of Bou-Sellam,

Morocco and Kroussou, Gabon (Caia, 1976) and the Carboniferous( ?) deposit of Cape

Breton Island, N.S. (The Northern Miner, March 3, 1977).

Samama (1968) proposed a syngenetic-sedimentary model for the Largentiere

deposit, in which heavy metals are derived from the Hercynian basement during the pre-

Triassic weathering cycle.

Lead isotope data for galenas from the Wollaston domain (Cumming~ al., 1970;

Sangster, pers. COlID!I . , 1976) yield a two stage model which supports the theory that

lead derived from Archean basement was deposited in Aphebian metasediments.

Within the constraints of such a model, regular tabular mineralized zones would

probably be an exception. Such features as paleotopography, paleochannels, presence

of argillaceous interlayers, etc. would act as controls to produce zones of complex

geometry.

(c ) At the southern end of the Wollaston domain, in the vicinity of Duddridge Lake,

the base(?) of the Wollaston Group is marked by a thick sequence of quartzites and

meta-conglomerates. Uranium-copper-vanadium mineralization is present within lenses

in carbonaceous quartzites. Sibbald et al. (1976) suggest that this occurrence may

represent an Aphebian Colorado Plateau-type deposit.

(d) Meta-conglomerate- and meta-arkose-hosted chalcocite-native copper mineraliza-

tion in the Kaz Lake area appears to be unrelated to local structural features,

igneous rocks or alteration of host rocks. The primary control may be stratigraphic.

Chalcocite-native copper mineralization is characteristic of red-bed environments

(e.g. Tourtelot and Vine, 1976). The host rocks in the Kaz Lake area are commonly

pink to grey meta-arkoses, that contain variable, but ubiquitous, amounts of hematite

and magnetite. Various authors (e.g. Rose, 1976) have emphasized the spatial asso-

ciation of red-bed copper occurrences and evaporites; within the Kaz Lake area

calcareous meta-arkoses, calc-silicates and marbles occur. It is possible that

evaporites have not been recognized.

The as sociat ion of copper and lea d in mineralized boulders within the Kaz area

presents a problem worthy of further s tudy . I t is not clear wh ether this as socia-

tion represents a possible Cu-Pb-Zn r egi onal zoning, or is a locali zed Cu-Pb sulphide

facies variation within an areally restricted basin environment.

- 103 -

The chalcopyr ite-mol ybdenite bearing boulders hsve not been traced t o a sour ce

(other than molyb denum mineralization at Mud Lake, Fig. 1) but it i s i nteresti ng to

note that these boulders may have been derived froo a widespread 'source bed' t hat

i s part of the upper calcareous meta-arkoses and calc-silica tes of the Wolla ston

Group.

In conclusion, the importance of boulder tracing cannot be over emphasized. A

large number of the base metal occurrences within the Wollaston domain have been dis-

covered through this method; and the use of geochemical methods is conspicuous by i ts

absence. I n telligent geochemical til l and overburden s ampling could pr ovide a suitable

s c ientific alternative to t he rapidly declining era of the methodical prospector.

References

Caia, J. (1976): Paleogeographical and Sedimentological Contro ls of Copper, Lead , and Zinc Mineralizations in the Lower Cre t aceous Sandstones of Africa. Econ. Geol ., v. 71 , p . 409- 422.

Chadwick, B. (1968): The Geology cf the Morell Lake Area (West Half ) , Saskatchewan ; Sask . ~ept. Min. Res ., Rept . 116.

Cumming, G.L. , Tsong , F. , and Gudjurgis, P. J. (1970): Fractional r emoval of lea d from rocks by volatilization. Ear t h Planet Sci. Lett ers V. 9, P. 49- 54.

and Scott., B. ( 1976) : Rb /Sr dating of r o.cks from the Wollaston Lake Belt , Saska t chewan . Ca n. J. Earth Sci. 13, p . 355-364.

Dahl k.amp, F.J. and Tan, B. (1977): Geol ogy and Mineralogy of the Key Lake U-Ni Deposits , Northe rn Saskatchewan. Symp. Geology , Mining, Extractive Processing of Ur anium. London .

Foglie'rini , F. , Brutt de Remur, M., Napoly , J. and Testut, R. (1965): Gisement de plomb et de zinc de Largenti~re (Ardeche). Annales des Mines , Paris. No. VI , p. 392- 410 .

Gilboy , C. F. (1975) : Foste r Lake Area , Saskatchewan, i n Summar y of I nves t i-gations by the Saskatchewan Geol ogica l Survey; Sask. Dept. Mineral Resources.

Grip, E. (1967): On the Genesis of Lead Ores of the Eastern Border of t he Caledonides in Scandinavia; in Genesis of Stratiform Lead-Zinc-Ba rite-Fluori te Deposits , A Symposium. Econ. Geol. , Mono . 3, p. 208-217 .

(1973): Sulfidmalrr. i fjallkedjan och fla ckhavson:.radet, in Grtp , E. and Fre itch , R., }~lm i Sv erige 2 . Stockholm, Almqvist and Wiksell, p.10- 37 .

Harper, C.T. (1975): The Geology of the Zinc -Lead Deposit a t Si to Lake , Norther n Saska tchewan. Unpub . M.Sc . Univer s ity of Saskatoon .

- 104 -

Karup-Moller, S. (1 970): Geology of the Compuls ion River Fold Belt. Western Miner, p. 35-51.

and BrUllllller, J.J. (1970): The George Lake Zinc Deposit, Wollaston Lake Area, Northeas t ern Saskatchewan. Econ. Geo l . v. 65, p. 862-874.

Money, P.L., Baer, A.J., Scott, B.P., and Wallis, R.H. (1970): The Wollaston Lake Belt, Saskatchewan, Manitoba, Northwest Territories, in Symposium on Basins and Geosynclines of the Canadian Shield. G.S.C. Paper 70-40.

Pyke , M.W . and Partridge, E.F. (1967): Occurrence of ·Base Metal Mineralization along the Wollaston- Sandfly Lakes trend, Northern Saskatchewan, unpub. paper, Industrial Exposition and Mi neral Symposium.Regina.

Rath, U. and Morton, R.D. (1969): Bas e Me tal Occurrence in the Wollaston Lake Belt of Northern Saskatchewan. Canadian Institute of Mining and Metallurgy Bulletin, v. 62, p. 961-966 .

Ray, G.E. (1974): Foster Lake (South) - La Ronge (N.W.) Area, Saskatchewan, in Sunnnary of Investi gations by the Saskatchewan Geological Survey ; Sask. Dept . Mineral Resources.

(19 75): Foster Lake (N .E. ) - Geikie Ri ver (S . E. ) Area, Saskatchewan, in Summary of Investigations by t he Saskatchewan Geological Survey ; Sask. Dept . Minera l Resour ces .

(1976): Fos te r Lake (N.W . ) - Geikie Ri ver (S .W.) Ar ea, Saska t chewan ; in Summary of Investigations by the Saskat chewan Geological Survey; · Sask. Dept. Mineral Resources.

Rose, A.W. (19 76): The Effect of Cupr ous Chloride Complexes in the Origi n of Red-Bed Copper and Related Deposits . Econ . Geol. v. 71, p. 1036-1048 .

Samama, J . C. (1968) : Contr~le de t ype "Red-Beds ". v. 3, p. 261-2 71.

d' 1 / "' . d . " li . 1' et mo e e genetique e minera zations en ga ene Gisement de Largenti~r e . Mineralium Deposita,

Scott, B.P . (1969): The Beckett Lake Ar ea (East Half) , Saskatchewan. Sask. Dept . Mineral Re sources, Rept. 122 .

(1970) : The Geol ogy of the Combe Lake Area, Saskatchewan. Sask. Dept. Mineral REsources, Rept. 135 .

(19 73) : The Geo l ogy of the Pendle t on Lake Area (West Half), Saskatchewan . Sas k. Dep t . Mineral Resources, Rept. 154.

Sibbald, T.I.I., Munday , R.J.C. , and Lewry , J.F. (1976) : The Geo l ogical Setting of Urani um Mineralization in Northern Saskatchewan. Sask. Geol. Soc. Special Publ. No. 3.

Tourtelot, E.B. , and Vine, J . D. (1976): Copper Deposits in Sedimentary and Volcanogenic rocks . U.S. G. S. Prof. Paper 907- C.