Download Ccu{>ilation Bedrock Geology: Stony Rapids Area (NTS 74P) by c. F

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Ccu{>ilation Bedrock Geology:
by
c.
F. Gil boy and P. Pamaekers*
The following accoW1t i s intended for use with
the 1 : 250 , 000 bedrock cx:rnpilat ion geology map
(pr e l iminary editi on) {Gilboy , 1980) . The
pre-Athabasca Group geol ogy i s a ccrnpilation
by C. F. Gi lboy of h i s o.,m and other authors '
wor k; although not extensively referred to in
the text of this report, source l i terature is
identified in the r e ference list. The geol ogy
of the Athabasca Group is the original work
o f P. Ramaekers.
In the descripti ons of the Athabasca Group ,
rrarber s of the Manitou Falls Formation have
been ass igned new codes differing as follows
from those which appear on the map: for Ar1Fa
read~ (as in.thi s acoount} and f o r ~ ,
re.ad ~d; Awa 1.s unchanged.
General Geol ogy
The Stony Rapi ds area covers approx:imately
12, 800 km2 . Four geologica lly distinctive
sul:rareas are recognized:
1.
2.
3.
4.
Stony Rapids Area (NTS 74P)
Mlrljatik Danain (in the east} ,
Dcrlge IXnain (in the northwest} ,
Tantato Danain (in the west) ,
Athabasca Group sedirrents (al ong the
southern boW1dary).
Domains 1 to 3, which are separated f ran one
another by major shear zones , are made up of
crystalline basenent rocks . The Athabasca
Group unconformably over lies basement in the
southern part o f the area.
Mudjatik Dorrain
Thi s dorrain i s largely underl a i n by pink to
whi te felsi c gnei sses (Unit !\, ~ } of uncertain origin. Subunit ~ , ~ich in gener al
appearance c l osel y r eserrble~ Archean granitic
gneisses of the Wollast on Danain , and Subunit
~ are horrogeneous pink syenograniti c
gneis ses , possibly derived from intrusive
rocks. They differ f r om one another in that
Subunit Mpa gnei sses contain microcline megacrysts up to about 1 an long and arc dark~r
in col our than those of Subuni t ~·
In contrast Subunits ~ and ~\,a carprise
compositiona l ly nore vafied r ocRs ranging f r cxn
dark pi nk syenogranitic to pal e pink or white
granodi oritic and tonalitic gneisses . The
l atter subunit typi cally contains about 30 percent or rrore of pegmat itic segregation material
along with bands , pods and bolrlins of mafic
amphibole gneiss , and is exposed throughout
the domain , especially around the southeastern
ann of Selwyn Lake. Close t o the east- central
edge of the area , the f elsi c gneisses carrronl y
appear to be wax-y and hypersthene bearing
(Uni t
MwFl.
Infol ded metasedirrents are widel y developed .
For the rrost part, they are lithologi cally
similar to the W:>llaston Group and appear to
be of Aphebian age (Krstic , pers. COTITI. , 1981) .
Pelites and semipelit es (Uni t MP) , whi ch are
the dominant rock t ypes, are hi ghly migmatiz.ed
in the east , wher e they characteristi cally
contain garnet, sillimanite , cordier ite and/or
graphi te. Towards the west , their rretarrorphic
grade decreases, and where they crop out c l ose
to the Black Lake Shear Zone, which bounds the
Mudjatik D::rnai n in the west , they occur as
poorly garnetiferous muscovite- biotite schist s .
calc- silicate r ocks and rare inpure marbles
(Unit M } , which form subordinate layers wi thin
the pelltes and semipelites in many pl aces,
genera l ly sh<:M rough , pit ted, weathered
surfaces. Q..Jartzites {Unit~} are locally
pr o l i f ic, especially around Sereda and Hawkins
Lakes and between Higginson and Peterson Lakes.
Also, southeast of Wing Lake, thin discontinuous quartzite lenses occur at the base of
metasedirrents preserved in the core of a major
synform. I n the Sereda and Hawkins Lakes
outcrops , the quartzites are carrronly richly
sillimanitic , and are interconnected along
strike by pink quartzofeldspathic gne i sses ,
probably rreta- arkoses (Unit '."Qp) • Grey,
quartz- rich, quartzofeldspathic gnei s ses
(al so Unit ~ ) form mappable layers in the
southeast , wh'ere they are interbanded wi th
rresotype arrphibole- biotite gnei sses (Unit~}
of probable supracrustal derivation. Close
to the western edge of the danain , wi de ly
developed me l anocratic amphibole schists and
gne i sses (Uni t~) interdi gitat e with peli tic
and semipelitic schists of unit MP . Both rock
types have been injected by granitoid plutons
with corrpositions ranging fran granite to
tonali t e (Unit Mer) . These pl utons have
suffered varying~aegrees of Hudsonian
deformation .
*Pre sently with Saskatchewan Mining Develorxnent Corpor ati on , Saskatoon.
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Early metagabbroi c or metadioritic intrusions
(Unit Ma3) form rare, small l e nsoid masses
within both felsic gneisses and supracrust al
rocks , which are also injected by tournaliniferous muscovite pegmatites and at least \:\\0
generations of ma.fie dykes. The older ,
locally feldspathoblastic dykes are rretarrorphosed but little defo:med. The younger dykes ,
which are virtually unmetanorphosed and undefonred and crop out only between the south
ends of Young Lake and Hawkins Lake, reserrble
the Helikian dykes that cut the Athabasca
Group sedinents south of the map area.
Black Lake-Gaste Lake Shear Zone
Ururetanorphosed polymict red sandstone , and
conglarerate boulders up to 50 cm in diarreter
ar e ccmron as glacial erratics in the v i cinity
of Gauthier Lake and in the Ridgen Lake Pilkey Lake area along the eastern margin of
the map area. These boulders indicate source
beds northeast of the Stony Rapids area which
are probably of fluvi a l origin and similar
to the Martin Formation in the Uranium City
area . The rocks along the ~stem edge of the
Mudjatik Domain , rrostly felsic gneisses of
Subunit '.'1Fd' are increasingl y defonred t.o,..,ards
the northwest. ~artz grains , for example,
becolre rrore and rrore l enti cular in shape , and
the average grain size of a ll rock- fanning
mineral s decreases . The defo:rmation , which is
clearl y axial pl anar to minor fol ds of the
gneissic foliation , occurs in a zone up to
about 8 km wide. The main shear zone ranges
in width fran 100 to 500 m; in the south ,
along the northwest shore of Black Lake , flinty
myl onitic rocks (Unit S) crop out in the proximity of a steep scarp. The shear zone here i s
a high- angle reverse fault which d ownthro;.;s
Athabasca Group sediments to the southeast .
Along strike to the northeast, extensive postshearing anneal ing has apparently taken place,
strongl y r ecrystallizing forrrer mylonitic rocks .
Codge Domain
This darain, which is botmded to the east and
south by the Gaste Lake and Grease River Shear
Zones , rrostly comprises a unit of rrore or l ess
equal arrounts of mafic and fel s i c hornbl endic
gneisses (Unit DQFA). Elsewhere e ither ma.fie
gneisses (Unit D~ , containing up to 60 percent
biotite and amp!n::tiol e, or , less cx:mronly,
quartzofel dspathic gneisses (Unit 001.J are
dan:inant. Granulite facies equi val~ts of
these three units (Dw;JpA' Dr..n,. and ~F) are
connon in many parts , and d1.rfer only in their
w~ dark greeni sh grey appearance , in containing hypersthene , and in being relative l y highl y
magnetic . The origin of the hornblendic rocks
is uncertain. In many exposures , where they
are ccrnpositionally banded on a scale of a few
millimetres t o several metres , they appear to
be volcaniclastic . Elsewhere the mafic rocks
in particular are CO!llX>Sitionally and t exturally
hom:)geneous over extensive regions , and may
represent forrrer intrus i ves .
Seemingly ccnfonnable infolded metasedinentary bands (Unit O,,p 5 ) are locally extensive.
Graphite-garnet- sill :uranite-biotite pelites
and semipelites are dominant , and were reported by Johnston (1960 ) t o contain also srne
kyanite . The presence of this high-pressure
mineral has not , hclv.ever , been ccnfinred .
Muscovite occurs in the metasediments in the
Selwyn Lake (west arm) area. Quartzi tes and
quartzitic psamnites are locally abundant.
Thin l ayers and l enses (ranging in width fran
l ess than 1 m to about 20 m) of brownish green
cal c- silicate rock , now seen as a felted mass
of inter locking trerrolite f ilires , are cormon ,
especially t.cMards the east.
Also in the east , adjacent to the Gaste Lake
Shear Zone, the supracrustal rocks are
structurally underlain by tonalitic to syenogranitic fel sic gneisses (Unit!:\-). The
latter , especially the rrore potassi~rich
varieties , closel y reserrble the felsic
gneis ses (Uni t M"') of the Mu:ljatik Dorrain
farther east. The contact be~en felsic
gneisses (Unit D,;.) and ma.fie gneisses (Unit DA)
is p::x,rl y exposea , but appear s to be sharp.
The f elsic gneisses possibly represent an
unconformable granitoid basem:mt to the
supracrust als.
In the northwest corner of the area granitoid
rocks a l so form a large intrusive mass , the
Eynard Lake Pluton, rrade up of metatonalites ,
rretarronzogranites and metarronzonites (Uni t DG)
containing xenoli ths of the country rock ,
hornbl e ndic gnei sses . I n nost exposures ,
the intrusion shows patches of waxy greenishcol oured charnockitic rock (Unit D,..... ) indicating that the pluton was intense'.l.y metanorphosed . A "scatterchron" produced by Rb/Sr
isotope s t u:li es (Bell and Blenkinsop, 1980)
suggests that the pluton has a probable late
Ardlean age , which irrpl ies that the host
s upracrustals are also Archean.
Several grani toi d intrusions are s ituated
along, o r c l ose to , the western boundary of
the map area . They occur within country rock
that itself a:opri ses at l east 50 percent
massive , crosscutting , weakl y garnetiferous
granite and garnet-tourmaline-muscovite
pegrratite . 'Ihe se late orogenic granitoids
reserrble in canposition the intrusives that
crop out in the "injection zone" cl ose to the
Grease Ri ver-Gaste Lake Shear Zone . Up to
7 km wide , the inject ion zone stretches up
the ~st side of Selwyn Lake . Ma.fie intrusive
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rocks ar e not clearly distinguishable from
those of possibl e extrusi ve ori g in, and all
mafic gneisses have been grouped together as
Unit DA.~ Malanocratic massive ultrarrafic
rocks \Unit °t.JM) fonn ~ S!Mll but mappable
masses in the ~entral part of the CX:dge
D::>main .
Grease River- Gaste Lake Shear Zone
This zone i s characteri zed along nost of its
length by outcrops of fine-grained myl onitic
felsic rocks {Unit S). The unit is subvertical or dips steeply to the nor thwest ,
and varies in total thickness fran O to 1. 5 km.
Myloni tic rocks are l acking in the "Gaste Lake"
segnent of the shear zone northeast of the
junction with the Black Lake Shear zone .
Microscopic examination of the mylonites sh<:Ms
that they have been extensi vely annealed. The
main shear zone is apparently off set en
echel on in the extrene southwest. Volcaniclastic rocks of Units o0P and DQFA' cropping
out i.mrediately to the nO!:'thwest or the shear
zone in the Tantato Lake vicinity, are l ocally
of lower arrphibolite rretanorphic grade and
preserve primary depositi onal layering.
Reoognizable primary layering disappears to
the north due to the rapid increase in rretarrorphic grades.
Tantato Domain
Occupying the regi on between the Grease River
and Black Lake Shear zones, the rocks of this
domain appear to be largely vol caniclastic in
ongID . They are nore felsic than those in the
CX:dge Domain, except in the southwest where
ma.fie hypersthene- bearing gneisses (Unit THA)
are abundant. The ma.f i e gneisses occupy the
core of a synform plunging shallowly southwest.
They are interbanded with, and are structurally
underlain by distinctive , highly f el sic biotitegarnet gneisses (Unit TGPs> that l ocally
contain graphi te . The mam outcrop of maf ic
hypersthene-bearing gneisses (Unit THA),
situated north of Stony Rapids, sharply terminates in the east against the Platt Cr eek Shear
Zone , which i s intensely cataclastic {Unit S)
in the south, and seemingl y d i es out to the
northeast. Northwest of the Platt Creek Shear
Zone , biotite-garnet gneisses (Unit TGPs> in
many places overlie grani tic to granodioriti c
felsi c gneisses (Unit TF) of uncertain or igin.
Elsewhe r e these fe lsic gneisses are surrotmded
by rreta- arkosi c biotite gnei sses {Unit Tp5 )
and/or by pelitic {garnet-) biotite gneisses
(Unit Tp), with which they are ccmronly interbanded .
The rrost widespread rock unit in the Tantato
Domain is the ' Hybrid Gneiss Ccnpl ex ' {Unit THG)
(Coll::ome, 1961) made up of felsic gneisses
{about 60 percent) conplexly interbanded with
amphii:x:>le schists and gneisses {about 35 percent), semipelitic to psanmitic biotite
schists and gneisses (ai:x:>ut 5 percent) , and
rare quartzites and banded iron formation . In
places, especially ta.var ds the west, close t o
the Pl att Creek Shear Zone , the Hybrid Gneiss
Conplex is Wa.X'j and apparent ly hypersthene
bearing. Fine- t o rrediUITHJrained hornbl endic
gneisses ± garnet {Unit TAI , present far the r
to the northwest, are l ocally delicately
layered with felsic bands and are of probabl e
volcaniclastic origin. Felsic rocks with flow
and tuf f features (Unit T0 ) crop out north of
Day Lake. Massive rregacrysti c gr anodi ori te
(Unit T) crops out in a long narraw body
(the F~ Lake Grancxli orit e) close to the Black
Lake Shear Zone and in a subci rcular pluton
(the M::x;illivray Granodiori te) northwest of
the Pl ate Cr eek Shear Zone . TJ1Q Fehr Lake
Granodiorite (alnost 40 km l ong) and its host
r ocks are injected by nafic s ills ( the
Chi pnan Sill Swann, Gill::oy , 1980; Macdonald ,
1980) , carprising ai:x:>ut 10 percent or rrore of
the rock vol urre in a zone which extends for
up to 16 km west of the Bl ack Lake Shear .
Indivi dual sills are up to ai:x:>ut 5 m wide and
consis t of foliated to nassive hornbl endi c
rock. Sorre are parallel to the axial planes
of minor folds and others have been much
i:x:>trlinaged. They appear to have been inject ed
towards the end of the Hudsonian orogeny, as
they are strongly to weakly deforrred and have
been dynamically or statically metanorphosed.
To the northwest of the Chipnan Sill Swarm,
l ong sill-like bodies of medium- to coarsegrained, poor ly foliated to massive rret agabbroic gaznet-hornblende rocks {Uni t TG8 )
also occur .
Tectonics and Metarrorphism, Pre- Athabasca
Group
The tectonotherrcal hist ory of the Stony
Rapids area is conplex. Pos sible chronological relationships b e ~ recognizable periods
of deformation , rretanorphism and intrusion are
given in Tabl e 1. Consi derable difficulty
exists in distinguishing between the effects
of the Kenoran and Htrlsonian orogenies .
Metasedirrents in the Charlei:x:>is r egion yiel d
Pb/Pb and Rb/Sr ages in the range 2390-1750 Ma ,
making them Aphebian in age {Krstic, pers.
carm., 1981), consequentl y all recognizable
deformation events , at l east in the Mudjatik
Dcxlain, are Hudsonian or later. ~st of the
Black Lake Shear zone , Hudsonian and preHudsonian ages (ranging from ai:x:>ut 2450-2000
Ma) have been r eported fran K/Ar measurements
on biotite and have also been implied fran
Rb/Sr isotope studies on whole rock sampl es
from the Eynard Lake Pluton. Thus Hudsonian
- 9 T•ble 1 .
Postulated tectono t herma l h i story of th e Stoo_y Rap ids ore•
----------~~-~-------Deform.a t i on
OHOG[NY
·- -·--··---------Metan10rph l sm
----- - - - - - - - --------·--·--··-··- - - - -··- -·--·--·Late fracturing produc ing N-S trend i ng
~ -"i"
~~~
"'1t.S ter
'""'' <
i ~;;
o4
-- -·- - -·--·-- -Intrusi on
-·-- ·--·--·- - --. - - · Localized emplacement o f sma ll diabase
bodte, at about 1100-1200 Ka
fractures
Late rrovernen t, includ i ng reverse faulting ,
on shear zones. Athabasca Group sediments
offset by Black Lake Shear Zone no,.theast
r-~ ______
...!.. d ~
o f F1r Isl and
__________________________
..
UPL!Fi. [ROSION ANO [){POSIT ION or ATIIASASCA GROUP SEOl H(NTS
Stati c upper greensch i st to lo'"'e r
aJl"C) hibo l e facies ~tamorphi sm
Shea r zones p robably developed 1n late
st ages of 03 event, mainly on 11mbs of
NC-SW folds
Ma fic si ll s of Chipman S i ll Swarm
inj ected. Peqmat1te veins injected on
no,.thwest s Ide of Grease Riv er/ Ga(,, te
Lake Shea r /one dnd i r, Char lf!bo 1s area
NI -SW fold s p robably peneco ntemporaneou s
wit h N- S (OJb) and E- W (0 3a) folding;
l imi ted E·W faulting probably gene ti cally
related to E·W fo ld1ng
,.
KE- SW fold i ng produc ing upright open ma j or
fol ds corr.JOnl y associated wi th ti gh t minor
fo 1ds, in ten sely developed axial plana .fabrl cs and co ·a>t1a1 lineat ion s. tndi s·
tinctly re cogn izable regiona l pat t ern of
mushroom-shaped inter fe rence folds
produced by OJIOz inte r ference
0
Regional nappe fo l ds possibly with NII-SE
hinges fa i ntly distl ngulshable i n all
thre e dornaiM o f the c rystal l 1ne basement
Pe g tona l devolopment of sth is tosity and
gnei ssosity ; genet i ca lly related folds,
1 f any . not now recognizabl e
t\eqacrys t ic gran ite emp1aced
Midd l e to lower all"!)hi bo l 1te facies
met onorphi sm
Ha in metamorphism at ta ining granulite
facfe s in the east, dN:reasing to
iniddl, ~nd l ower ~mph i bolite fac ie s
close to shear zones
Seg rega tion of graoito1d materia 1
parallel to D1 per vas i ve planar fabri c
Earl y foli Hed gr aoito id ma sses
...placed (e.g. Uo it MGT)
Pre01
Not recogn 12ed
- ---·- ------·---------·-------Granul He facies metamorphism
Maf ic to ul tramaf1c fntrus ioris .
• est of Bloc k L•k e Shear Zone
poss i bly of an intrusi ve/ex t rusive
Archean comp 1t x
·-- -·--·---- - - ------ -- -·--- - - - - thenrotectonism in the west appears t o have
onl y partially reset Kenoran plutonic events ,
s uggesting that the granulite fac:ies rretarrorphism here was a Kenoran event .
Athabasca Group
All Athabasca Group sedilrents 1n the area
belong t o the Manitou Falls Formation, a
f l uviatile unit that may be informally divided
into : a basal ' oonglareratic merrber' ( ~ ) ,
a middl e ' sandy braided rrember . ( ~ ) , :ma
an upper 'intraclast - rich ' nember \;{.w d).
Bot.mdari es are gradati ona l and arbi trary. The
f orrration reaches a maximum thickness of about
550 min the southwest corner of the map area .
The Manitou Falls Forrration overlies a baserrent
regolith . This altered w ne is O to 50 m thick
and shcrws a lateritic 1111eathering profile .
Generally a sparse , poorl y sorted, congl orrerati c lag deposit less than 30 an thick i s
present at the oontact and i s locally re,,Qrked
into the l ower 10 m of the Manitou Fall s
Formation. I t is thickest at Newnham Lake ,
whe re it l i es 2 m above pelitic baserrent r ich
in quartz segregations .
The congloneratic rranber ( ~ ) i s generally
present along the oontact but is poorly exposed
except at Middl e Lake and south of Mx>sonees
Lake. Its thickness varies from O to 50 m
and it consists of interbedded sandstones and
c last- support ed irnbricat ed conglorrerates .
Cl asts are less than 16 mn in diarreter. The
oonglomerates thin dis tally and upward into
layers one pebble thick and eventually into
di scontinuous , scattered , fine pebbles along
bedding planes as they grade into the sandy
braided rrember (At..wc) . The congl orrerat es show
mass ive bedding anci crude pl anar crossbedding.
The inter bedded sandstones are l argely trough
and pl anar crossbeddcd with sare ripple
cross lamination .
The Ar,,nc, rrember consists of sandstones sha..ing
abundan~ trough cros sbedding , planar crossbedding i n sets up to 1 . 5 m thick , rippl e
cross-laminat i on , sporadic scattered pebbl es
a l ong bedding planes , and less than 1 percent
of clay intraclast l ayers.
The A....c.a rrember i s similar except that clay
intrac".l.ast layers form rrore than l percent
of the sequence , and i t shONS nore current
r i ppled surf aces and a few oscillation rippl e
marks.
The sandstones are quartz arenites in that
virtually all fra!l'C',.Ork grains are quartz .
Tourmaline , :rutile and/or anatase , and zirOJn
are present, but fonn much l ess than 1 percent
of the r ock . Detrital hematite i s present in
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the cxmglarerates and the lower part of the
sandstones, and is usually associated with
zircon in thi n (1 to 10 nm) pl acers.
faults , as well as causing or reactivating
those trending north .
The daninant interstitial rraterials are illite
and kaolinite (5 to 15 percent) , silica cenent
l argely in the form of syntaxial overgrCMths
(0 to 5 percent), iron oxides , largely authigenic specular hem3.tite (typically 0.5 to 2
percent) , but with sare lirronite and nu.nor
arrounts of siderite occurring mainly i n fractures . Tourmaline and detrital hematite also
show overgrCMths .
Eoonam.c Geology
The paleocurrent patterns suggest that all
sandstones in the Stony Rapids mapsheet area
form one deposystem with a source to the east
and nor theast. The distribution of palecrcurrent directions is unimxlal with low variances at the outcrop and even at the regional
level.
M::>st faults in the Athabasca Group appear as
escarprents. Even along the major faults the
cl osest outcrops generally show little
evidence of disturbance. consequently, much
ll'Ore faulting probably occurred than is
rrappable at the surface . Best exposed are
those in the i ntensely folded and faulted
rocks on southeast Fir Island and along the
Fond du Lac River , upstream of Brink Rapids,
where the sandstones show drag folds wi th dips
of 45°. The major fault zones form anastarrosing systems trending to the northeast. Northtrending faults and fractures also occur and
form praninent lineanents around Brink Lake .
Boulders of unmetanorphosed diabase are
l ocally comron on the Athabasca sandstones in
the map area and suggest the presence of dikes.
Regional post-Hudsonian uplifts resulted in
unroofing of the area to rrore or l ess its
present level , and in the formation of a deep
weathering profile. Further uplifts in the
east, coinci ding rou,Jhl y with the Wollaston
Belt, resulted in the formation of alluvial
fans of which the distal deposits are present
in the eastern part of the Stony Rapids map
area. These f ans graded west i nto an alluvial
plain.
Grain sizes in the Athabasca Group are zoned
parallel to the w:>llaston Fold Belt, suggesting
that the northeast- trending fault zones were
active during the initial events forming the
Athabasca Basi ns, and that these events reactivated Hudsonian shear zones, at least in the
Black Lake area. The age of other deformation
is unknown. Serre of the north-trending faults
rray relate to the early fornation of t.11e bas in.
Subsequent activity may be due to a diabase
dyke intrusive event at around 1100 Ma , which
probably reactivated the northeast- trending
Currently, exploration activity is 110stly
directed towards locating uranifer ous ore , and
i s concentrated aver and along the northern
edge of the Athabasca sediments. No major
deposits have been reported , although showings
have long been known , especially in the vicinity of Middle Lake.
Uranium hcsted by crystalline baserrent has also
attracted considerable c:xxrrnercial i nterest:
a)
Pitchblende occurrences in veins along
fracture zones and shears in hanging wall
paragneisses of the Black Lake Shear Zone
were suf ficiently rich to warr ant an
extensive drilling prograrme and the
driving of two adits by Nisto Mines Ltd.
in the early fifties . The showings were
found to be uneconomic . This conclusion
has been confirned by several subsequent
re- examinations.
b)
Uraniferous pegmati tes from several
localities in the Charlel:x::>is and Pluto
Bay areas have been repeatedl y but unsuccessfully examined and tested for
their economic viabil ity.
Other rretallif erous occurrences exist in
crystalline baserrent rocks. Banded i r on formation crops out in a few places, but is best
developed in the r egion between Black Lake
and Middle Lake . The nost recent evaluations
in this locality , carried out in 1973 as part
of the Federal/Provincial Mineral Evaluation
Progr am, indicate that the waximllll ore
reserves recoverabl e by open- pit mining to a
depth of 150 mare approximately 7 mil lion
rretric tons grading 30 to 40 percent iron .
Moly.l:xieni te is present in the Pluto Bay- Eklund
Lake r egion, apparently stratabound near the
contact between calc-si licat e rocks and
pelitic to semipelitic gneisses . Mineralization i s concentrated into biotite- rich seams
fo.rTIEd around quartz- rich pegmatite segregations. r.blyl:xlenite is al so found in the
Eynard Lake Pluton at the north end of Kimian
Lake, where , as flakes up to 1 cm in diarret.er ,
it forms up to 0.5 percent of intensely
weathered , friable rretarronzonite (Unit DG) in
several exposures .
Sulphide showings are widespread. Several
have been drilled but proved to be essentially
barren. Nurrerous srrall deposits of nickeliferous pyrrhotite-chalcopyrite-pyritearsenopyrite are r e ported fran maf ic "noritic"
rock (Unit THA) in the Tantato Domain.
- 11 -
Reference s
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Clut Lakes area (west half) , Sas katchewan;
Sask . Dept . Min . Res. , Rept . 43.
(1960): 'fue geol ogy of the
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Sask. Dept . Min . Res . , Rept . 58.
( 196 1) : 'fue geol ogy o f the
- - ~As
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_ _ __ (1962) : 'fuc geology of the
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(1964): The geolo,w of the
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- - - - : : - - ( 1979) : Reconnais s ance bedrcx::k
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o f the Charleboi s -Higginson Lake area ,
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- - -~ - (1980): Reconnaissance bedrock
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Jes ., Jept. 44.
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