Geological Setting of the 'Santoy Lake' Gold Camp (Part of
NTS 63M-11 and -12) 1
G.D. Delaney and S.A. Cutler2
Delaney, G.D. and Cutler, S.A. (1992): Geological setting of the 'Santoy Lake' gold camp (part of NTS 63M-11 and -12); in Summary of Investigations 1992, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 92-4.
Forest fires during the summer of 1989 resulted in extensive clean outcrop in the area south of Carruthers Lake
on the west central side of NTS map sheet 63M-11. Subsequent prospecting in this formerly, poorly exposed
area lead to the discovery of several significant gold
showings in the vicinity of the small hook-shaped lake informally named 'Santoy Lake', located approximately
8 km east of the Seabee gold mine (Delaney, 1992).
The high economic potential of the area, coupled with
the superb exposure, afforded an excellent opportunity
for a detailed investigation of the gold mineralization
and its geological context. Consequently during the summer o f 1992, an area of approximately 1O km 2 was the
subject of a multidisciplinary investigation.
The preliminary results of these investigations are
reported in three papers in this volume. In addition to
this paper, which describes the geological setting of the
area, there are those by Durocher et al., describing the
gold mineralization and by Williams et al., describing a
newly discovered swarm of beryl pegmatites. Aspects of
these studies will be the subject of theses by Cutler at
the University of Leicester and Durocher at the University of Saskatoon. Cutler's dissertation will examine the
structural context of the gold mineralization and
Durocher's thesis will focus on the P-T-t history of the
area.
ment Files of Saskatchewan Energy and Mines (Bennett, 1990a, b, 1991, 1992).
2. Regional Geological Setting
The Glennie Domain is one of a number of distinct twodimensional lithostructural domains (Lewry and Sibbald,
1977; Saskatchewan Geological Survey, 1987) that form
the internal part, the Reindeer Zone, of the Lower
Proterozoic Trans-Hudson Orogen in Saskatchewan and
Manitoba (Hoffman, 1990; Lewry and Collerson, 1990).
The Reindeer Zone consists mostly of a northeast-trending collage of juvenile Proterozoic crust including island
arc assemblages. The Glennie Domain contains complexly deformed, elongate, generally narrow arcuate
belts of supracrustal rocks that include volcanogenic,
arkosic, and pelitic/ psammopelitic assemblages. Lower
Proterozoic and locally tectonically interleaved Archean
granitoid rocks make up the major part of the domain.
As with much of the rest of the Trans-Hudson Orogen,
the Glennie Domain has, according to Lewry et al.
(1 990), been subjected to four major episodes of deformation. The south was metamorphosed to upper
greenschist or lower amphibolite facies grade. In the
north of the domain the grade reached middle to upper
amphibolite and rarely granulite facies (Rees, 1982;
Lewry et al., 1978).
1. Previous Work
In 1955, Budding and Kirkland (1956) mapped the
western three-quarters of NTS sheet 63M-11 at a scale
of 1:63,360. Lewry (1977) mapped NTS sheet 63M-12
also at a scale of 1:63,360. The study area was included
in 1:20 000 scale mapping by Delaney during the summers of 1986 and 1967 (Delaney, 1986, 1987) and
aspects of the geology are discussed in a subsequent
report on gold mineralization in the Glennie Domain
(Delaney, 1992). The map-area is contained in a preliminary 1:250 000 compilation of the Pelican Narrows and
Amisk Lake sheets (Macdonald, 1981 ). An extensive
reconnaissance lake sediment geochemical survey by
the Geological Survey of Canada in 1974 (Hornbrook et
al., 1975, 1977, 1985) included the Santoy Lake area. In
addition to these government reports, information on
the map area is also contained in the Mineral Assess-
3. Local Geology
a) Summary
The Santoy Lake area lies in the Pine Lake Greenstone
Belt (Lewry, 1977; Delaney, 1986, 1987, 1992), which includes variably deformed, metamorphosed, migmatized,
and granitized volcanic, volcaniclastic, sedimentary and
intrusive rocks.
In the Santoy Lake area, supracrustal rocks have been
subdivided into two assemblages (Figure 1):
Assemblage 'A' comprises mafic to intermediate volcanic, volcaniclastic, and subvolcanic intrusive rocks as
well as minor siliciclastic sedimentary rocks most of
which have been metamorphosed to varieties of am-
(1) Saskatcnewan Project A 12a is funded in 1992·93 under the C anada-Saskatchewan Par1nership Agreement on Mineral Development 1990·
1995.
(2) Oepartm ent of Geol ogy, Univer sity of Leicester, Leiceste r, U.K.. LE1 7RH.
30
....... --·-·--·- -· ......
Summary of Investigations 1992
··-·---- -- -
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
G[OLOGICAL
SK[TCH MAP
SANTOY LAK[ AR[A
x
x
x
x
Ca rru thers
Lake
x
10 3"30 '
0
0.5
1.0
2 .0
1. 5
KM
LEGEND
INTRUSIONS
PINE LAKE VOLCANICS
n
Gron it e /Gron o d ior ite
D
Gron itoid c omp lex
f
Hornb lend ite
•
Assemblage B
•
Chl or it e sch is l
~
~
Con g lo rn erot e
Pe lit ic sed im ent
Assembla g e A
[]ill
Ho r nb len dic sed im ent
Dio ri te
EJ
Feis ic vo lc o ni clost ic
:.. j
Lop illi tu ff
j
------------· .
I nte rm ed iote
volc cr1 ·c :;
e nd vo lc on ic lo~;fr::~;
Mof ic and
intermed iate
- · ·····~------ ·- -- - - - - - - - - - -
Figure 1 - Simplified geological sketch map of the Santoy Lake area. CL.A= Carruthers Lake Antiform, CLS =Carruthers Lake Synform, HSZ=High-strain zone.
phibolite and mesocratic to melanocratic biotitehornblende-plagioclase gneiss. Layers and lenses of
epidote are common locally.
Saskatchewan Geological SuNey
Assemblage 'B' is a metamorphosed, altered, and
variably deformed assemblage of volcaniclastic and
sedimentary rocks. A number of major units have been
distinguished: conglomerate, felsic volcaniclastics,
31
hornblendic volcaniclastics and sediments, pelitic sediments, lapilli tuffs, and chlorite-actinolite schists. In the
west, conglomerate occurs at the contact with the mafic
and intermediate volcanic assemblage. Lapilli tuffs are
abundant in the east.
Leucocratic granitoid complexes, veins, and lenses invaded the supracrustal assemblage prior to deformation. Following the first deformation leucocratic
granite/granodiorite, now forming the core of the Carruthers Lake Antiform, intruded the supracrustal rocks.
Pegmatite dykes, which include a garnet-beryl-tourmaline suite, intruded the granite and adjacent
supracrustal rocks.
The Santoy Lake area has been affected by at least
three episodes of deformation. These are correlated
with the D2 to 04 events distinguished by Lewry et al.
(1990) in their synthesis of the structural evolution of the
internal part of the Trans-Hudson Orogen in Saskatchewan:
02 is associated with the dominant foliation which is
axial planar to tight to isoclinally folded felsite veinlets
and original compositional layering. Narrow continuous
high-strain zones are also attributed to 02 deformation.
D3 is manifest in major moderately plunging open to
tight large scale folds, such as the south-southeastplunging Carruthers Lake Antiform and the north-plunging Carruthers Lake Synform (Figure 1). Axes of smallscale folds and crenulations as well as mineral lineations
and elongation lineations are coaxial with the major
structures. Locally, small scale 02 folds have been
refolded by the 03 structures producing type 2 and
type 3 interference structures. High-strain zones, such
as the major north-northwest-trending zone through Santoy Lake, are developed along the limbs of the major
03 structures. Steep east-trending and conjugate fractures crosscut D3 folds.
Evidence of the 04 event is preserved only locally as
type 1 interference folds.
The Santoy Lake area was subjected to an early
episode of amphibolite facies metamorphism coeval
with 02 deformation. A second episode of amphibolite
facies metamorphism occurred during, and subsequent
to, 03 deformation.
Several significant gold showings occur in 0 2 high-strain
zones in volcanics of Assemblage A near the contact
with Assemblage B. Some of the gold showings are
hosted in felsic granitoids in the high-strain zones. Sulphides and gold occur in fractures and along contacts
of quartz veins as well as in adjacent sheared and altered rock.
More than forty beryl- and tourmaline-bearing pegmatites occur in supracrustal rocks east and south of
the granitic intrusion in the core of the Carruthers Lake
Antiform (CLA). Some of these may have potential for
gem quality beryl.
32
4. Description of Units
a) Assemblage A
Assemblage A consists of variably metamorphosed
mafic and intermediate volcanic, subvolcanic intrusive,
volcaniclastic, and minor sedimentary rocks. The rocks
will be described for the main part of the map area and
for the southwest part.
Main Area
Amphibolite
Dark grey, fine- to medium-grained homeoblastic amphibolite derived from mafic volcanic flows underlies
most of the area north, west, and east of Santoy Lake
and along the west side and in the interior of the Carruthers Lake Syntorm (CLS, Figure 1). This unit varies
from massive to weakly foliated, and commonly contains millimetre- to centimetre-size blebs of fine-grained
plagioclase that compose from 5 to 25 percent of the
rock. A rare phase is characterized by 25 to 40 percent
medium- to coarse-grained equant plagioclase
phenocrysts in a fine-grained mesocratic matrix of
hornblende and plagioclase.
The amphibolite is cut by irregular veins and apophyses
of light grey-weathering, mesocratic, plagioclase-blastic
gneiss characterized by millimetre- to centimetre-size
clots of plagioclase in a matrix of fine-grained
plagioclase and minor quartz containing clots of finegrained hornblende and minor disseminated magnetite.
Contacts with the amphibolite vary from sharp to diffuse.
Mesocratic Biotite-Hornblende-PJagioc/ase Gneiss
A thick sequence of dark grey, fine- to medium-grained,
mesocratic biotite-hornblende-plagioclase gneiss,
derived primarily from intermediate volcanic flows, underlies the east side of Santoy Lake and parts of the Carruthers Lake Synform. Although generally texturally and
compositionally uniform on the outcrop-scale, there are
local textural and compositional variations in the gneiss.
These include: plagioclase, plagioclase and hornblende,
and hornblende porphyroblastic layers, rare conformable lenses of medium- to coarse-grained mesocratic
diorite, narrow amphibolite dykes, lenses and clots of
epidote, layers of abundant garnet, and intervals of compositionally layered wacke or lapilli tuff.
Mesocratic Hornblende Porphyroblastic HornblendePlagioc/ase Gneiss
The southeast side of the Carruthers Lake Antiform is underlain by a large body of greenish grey- to steel greyweathering, mesocratic, hornblende porphyroblastic
hornblende-plagioclase gneiss characterized by mediumgrained, commonly elongate porphyroblasts of
hornblende and medium-grained, sericitized
phenocrysts of plagioclase in a fine-grained matrix of
quartz, biotite, hornblende, plagioclase, and minor
sphene. Scattered throughout this unit are patchy, buffweathering, 'bleached-looking' areas where the
Summary of Investigations 1992
hornblende porphyroblasts have been replaced by
biotite. Lenses of epidote are locally abundant. This
rock is interpreted to be derived from a diorite or intermediate subvolcanic intrusion.
Biotite-Plagioclase Schist
Intensely weathered, rusty biotite-plagioclase schist containing diffuse hornblende-rich lenses and lenses of
leucocratic, medium-grained, garnetiferous hornblendeplagioclase gneiss, is intercalated with the biotitehornblende-p1agioclase gneiss and amphibolite in the
Carruthers Lake Synform.
Southwestern Area
In the southwest, Assemblage A is composed of mafic
to intermediate volcanics, volcanic breccias, volcaniclastics, and subvolcanic intrusives. In contrast to the rest of
the Santoy Lake area, primary structures are preserved
throughout much of this succession. The main units are
described below:
the south the hornblende clots make up as much as 15
to 20 percent of the rock. In thin section this unit displays randomly-oriented, medium-grained ptagioclase
phenocrysts with corroded edges. The matrix is a very
fine-grained mosaic of plagioclase and minor quartz containing clots of fine-grained hornblende, some of which
is poikilobtastic.
Near the centre of the subvotcanic sill is a 250 m tong
by 30 m wide tens of pillowed intermediate volcanic
rock. Pillows, which are flattened parallel to foliation, are
up to 1.5 m long and 0.5 m wide. Although there are
well developed selvages on the pillows, amygdales are
absent. Interiors of the pillows contain scattered mediumgrained phenocrysts of plagioclase in a fine-grained,
mesocraHc hornblende-ptagioclase matrix. A thin section of this rock shows homeoblastic, fine-grained
plagioclase and about 30 percent hornblende as disseminations and clots. Rare isolated subhedra of
plagioclase up to 0.8 mm in diameter and granular clots
of fine-grained leucoxene are also present.
b) Assemblage B
Mafic Volcanic Braccia
Mafic volcanic breccia is characterized by an intact
framework of generally equant, grey- to dark greyweathering fragments that range in diameter from a few
centimetres to a few tens of centimetres. Fragments are
composed of fine-grained hornblende and plagioclase.
Plagioclase porphyroblasts occur in both fragments and
matrix. Massive mafic flows are intercalated with the fragmental unit, which is cut by narrow hornblende porphyroblastic dykes and felsite veinlets.
Andesitic Tuff Breccia
This unit is characterized by very fine-grained, light greyto buff-weathering, wispy-terminated, tabular fragments
aligned parallel to foliation, which forms an intact to disrupted framework in a matrix of fine-grained biotite,
hornblende, and plagioclase. Intercalated in the breccia
are rare, and locally amygdaloidal, intermediate flows,
and narrow layers of bedded, fine-grained sediment or
tuff. Medium- to coarse-grained porphyroblasts of
plagioclase are common throughout this sequence.
Hornblende P/agioclase Tuff
Fine-grained, dark grey- to dark greenish grey-weathering, compositionally layered hornblende-plagioclase tuff
is the main unit in Assemblage A in the southwest. Intercalated in the tuff are layers of the tuft breccia. Fine- to
medium-grained plagioclase porphyrobtasts are common throughout this tuffaceous sequence and locally
epidote-rich layers and lenses are abundant.
Intermediate Subvolcanic Sill
A thick, homogeneous, massive to foliated, grey- to
greenish grey-weathering, intermediate subvolcanic sill
occurs in the andesitic tuff breccia and hornblendeplagioclase tuff. This sill contains 10 to 15 percent millimetre-size clots of fine-grained hornblende in a finegrained leucocratic hornblende-plagioclase matrix. In
Saskatchewan Geological SuNey
Assemblage B consists primarily of metamorphosed, altered, and variably deformed votcaniclastics and
sedimentary rocks.
Conglomerate
In the west, a conglomerate-dominated facies occurs at
the contact of Assemblage A (Figure 1). In the southwest, the conglomerate (which thickens to the westnorthwest) is from about 3 to 70 m wide. The layer has
been traced continuously for about ten km to the west.
About six km east of the map-area, between Pine and
Porky lakes, the conglomerate is intercalated with a
thick sequence of falsie volcanic and fragmental rocks,
feldspar porphyry flows, arenites, and pelites (Lewry,
1977; Delaney, 1986, 1987). Zircons from one of the felsic volcanic flows have yielded a U-Pb age of 1838
±2 Ma (McNicoll et al., in press). South of Porky Lake,
this assemblage unconformabty overlies the Laonil Lake
Intrusive Complex (Delaney, 1986) from which a quartz
diorite phase has been dated at 1889 ±8.7 Ma (Chiarenzelli, 1989). The southeastern extent of the conglomerate is unknown.
In the southwest, the conglomerate displays a generally
intact framework of heterolithic pebble- to boulder-size
fragments in a fine-grained matrix of biotite, quartz, and
feldspar that locally contains clots of fine- to mediumgrained hornblende. Scattered throughout the matrix are
irregular lenses and veins of quartz and clots of epidote.
Clasts, which are variably flattened and stretched parallel to foliation, and locally folded, include leucocratic
granitoids, feldspar porphyritic felsic volcanics, and
wacke. Hornblende schist is intercalated locally in the
conglomerate.
Along the east side of Santoy Lake, the conglomerate
which occurs at the contact with mesocratic biotitehornblende-plagioclase gneiss of Assemblage A, has
been progressively strained. Northwestwards to north of
Santoy Lake it becomes indistinguishable from rocks of
33
the high-strain zone separating the amphibolite from the
biotite-hornblende-plagioclase gneiss (Figure 1).
Southeast of Santoy Lake, the conglomerate ls folded
around the nose of the Carruthers Lake Antiform.
At the southeast end of Santoy Lake two other units are
intercalated with the conglomerate. The most abundant
is a massive, grey-weathering, fine-grained unit composed of up to 25 percent hornblende in conformable
clots usually a few grains thick. Locally within this rock
are millimetre-size clots of hornblende mantled by finegrained, white feldspar, and clots of quartz and
hornblende mantled by epidote. Quartz veins mantled
by epidote or epidote and hornblende are locally abundant. Rare garnet porphyroblasts occur locally. A thin
section of this rock reveals a very fine-grained,
homeoblastic mosaic of plagioclase and quartz with subordinate fine-grained biotite and isolated to clotted,
slightly coarser, anhedral hornblende.
Also intercalated in the conglomerate at the southeast
end of Santoy Lake are layers and lenses of garnet porphyroblastic biotitic schist.
fine-grained, mesocratic hornblende-plagioclase gneiss
that varies from homogeneous to more typically compositionally layered and locally contains plagioclase porphyroblasts. Minor hornblendite and biotite schist are intercalated in the gneiss. Locally there are abundant foliation-parallel milky quartz veins which are typically
mantled by hornblende and epidote.
South of the southeast arm of Santoy Lake, the
hornblende content decreases and the main rock type
is a fine-grained, brownish grey- to grey-weathering,
biotite-hornblende-plagioclase gneiss typically with millimetre-thick conformable clots of hornblende. Locally
the gneiss contains blotchy olive- to greenish greyweathering epidote patches. Also intercalated with the
gneiss are layers and lenses of buff- to buff light greyweathering biotitic quartz-feldspar psammite containing
minor disseminated magnetite and rare porphyroblasts
of garnet.
Along the south shore of Santoy Lake, the conglomerate contains lenses and layers of wacke, some of
which are compositionally layered.
South of the southwest arm of Santoy Lake rocks of this
belt comprise generally strongly foliated and locally
crenulated, grey- to buff grey-weathering, fine-grained
pelitic and conglomeratic metawacke containing variable
amounts of hornblende as disseminations, clots, and
layers. Locally the rock is compositionally layered. Extremely flattened and stretched, pebble-size clasts are
preserved with vague ghost-like outlines. Blades of fineto medium-grained actinolite are preserved on foliation
surfaces. Locally within this wacke assemblage there are
epidotic laminations and lenses mantled by a halo of
hornblende.
Fe/sic Volcaniclastic Rock
Pelitic Sediment
A southeast-trending belt of buff light grey- to mottled
pinkish buff-weathering felsic volcaniclastic rocks occurs
at the southeast end of Santoy Lake and in an extensive
body in the southeast. Blebby clots of fine-grained pink
feldspar occur throughout this unit. In places these clots
contain cores of quartz and/or hornblende, as well as
porphyroblasts of garnet. Scattered medium- to coarsegrained porphyroblasts of garnet also occur elsewhere
in the rock. In thin section this rock is seen to consist of
a fine-grained mosaic of quartz and plagioclase containing 10 to 15 percent biotite, minor magnetite, and rare
hornblende and anhedral poikiloblastic garnets. Lenses
and veinlets composed of fine-grained quartz,
plagioclase, calcite, hornblende, and biotite are mantled
by sericite.
A lenticular-shaped body of strongly foliated and crenulated, grey- to brownish grey-weathering biotitic schist
occurs amongst the hornblendic sediments south of
Santoy Lake. Locally tile schist is compositionally
layered and it contains some arenaceous layers; some
parts contain stretched and tightly folded pebble-size
clasts. Occurring throughout the schist are tightly to
isoclinally folded felsite and quartz veinlets that have
been refolded parallel to a prominent crenulation
cleavage to form type 3 interference structures.
On the southwest side of the nose of the Carruthers Antiform, the conglomerate and intercalated pelite beds
contain clots of apparently undeformed, medium- to
coarse-grained andalusite and fibrolitic sillimanite.
In the felsic volcaniclastic unit, near the southeast corner
of the map area, there is a band of felsic volcanic fragmental material characterized by strongly rodded, very
fine-grained quartzofeldspathic fragments up to 2 cm in
diameter, which forms a disrupted framework in a finegrained quartzofeldspathic matrix similar to the main felsic volcaniclastic unit.
Quartzofeldspathic Sediment
On the north side of the biotitic schist is a lenticular
body of buff light grey-weathering, fine-grained,
laminated quartzofeldspathic sediment that contains
minor biotite, disseminated magnetite, and rare fine- to
medium-grained porphyroblasts of garnet.
Lapilli Tuff and Wacke
Homblendic Sediments and Vo!caniclastics
A thick succession of lapilli tuft and wacke occurs between the Carruthers Lake Antiform and the Carruthers
Lake Synform. Narrow intervals of lapilli tuft occur elsewhere in the supracrustal succession.
An extensive and variable belt of hornblendic sediments
and volcanic!astics occurs in the southwest adjacent to
the conglomerate. In the southeast, rocks in this unit
generally comprise well foliated and locally crenulated,
Lapilli tuft along the east side of the Carruthers Antiform
is a grey- to dark grey-weathering, strongly foliated,
mesocratic, fine- to medium-grained rock characterized
by a disrupted framework of wispy terminated lapil!i. In-
34
Summary of Investigations 1992
tercalated with the tuft is a grey- to brownish greyweathering, mesocratic wacke and a more
homogeneous looking grey- to dark-grey weathering
mesocratic hornblende-plagioclase gneiss.
East of the nose of the Carruthers Lake Antiform this
subdivision consists of interbedded wacke, lapilli tuft,
hornblende porphyroblastic lapilli tuft, and hornblendic
lapilli tuft. The wacke is a grey- to brownish greyweathering, thinly bedded and laminated rock. Vague
grading was observed in some of the beds. Intercalated
within the wacke are several thick beds of lapilli tuff characterized by tabular, wispy terminated fragments forming a disrupted framework in a fine-grained mesocratic
matrix of hornblende and plagioclase. Less common
are medium to thick beds of grey-weathering, graded
lapilli tuff containing medium to coarse porphyroblasts
of hornblende near the coarse base. Another minor component is hornblendic lapilli tuft, an emerald greenweathering rock characterized by light grey-weathering,
fine-grained felsic lapilli in a matrix of fine- to mediumgrained hornblende containing scattered coarse-grained
porphyroblasts of hornblende.
Actinolite-Chlorite Schist
Emerald green magnetite-sericite-actinolite-chlorite
schist occurs in the east central and eastern part of the
map area, most commonly in the lapilli tuft and wacke
unit. The schist is strongly foliated and commonly displays conjugate crenulation cleavages. At some
localities the schist is layered and in one outcrop multiple folding of the layering has created type 3 interference folds. More commonly, however, the schist is a
homogeneous unit locally containing coarse-grained,
light greenish grey porphyroblasts. Thin section examination revealed that both foliation and crenulation
are flattened around the original porphyroblasts, which
contain dustings of magnetite. Subsequent growth of
amphibole has replaced much of the porphyroblasts, as
well as overgrowing both foliation and crenulation. Posttectonic amphibole also overgrows the crenulation
cleavage defined by chlorite.
c) Intrusive Rocks
Hornblendite
A 1.5 km long lenticular body of dark green-weathering
hornblendite, that is as much as 70 m wide, occurs
along the east side of the map area. This massive to
weakly foliated unit features medium- to coarse-grained
hornblende forming an intact framework. Near the contacts there _are patchy areas of fine-grained plagioclase
1n the matrix and locally abundant epidote veinlets.
Felsite
Sills of buff to pinkish buff, leucocratic, fine- to mediumgrained felsite are common throughout amphibolite of
Assemblage A. Individual sills are up to several hundred
metres long and range in thickness from tens of centimetres to tens of metres.
Saskatchewan Geological SuNey
Leucocratic and Mesocratic Granitoid
Irregular bodies of leucocratic and less commonly
mesocratic granitoid occur in supracrustal rocks in the
Carruthers Lake Antiform and in the west limb of the Carruthers Lake Synform. The granitoid in the core of the
Carruthers Lake Synform is buff to light grey weathering,
leucocratic, and contains fine- to medium-grained porphyroblasts of garnet in a fine- to medium-grained
granoblastic mosaic of plagioclase with minor biotite
and hornblende. Wispy terminated hornblende-rich lenses with medium- to coarse-grained porphyroblasts of
garnet are common. There is a gradational contact between the granitoid and supracrustal rocks to the north
defined by a gradual decrease in the size and abundance of veins and lenses of granitoid. Where
plagioclase-rich lenses are abundant, they appear as
fragments in the hornblende plagioclase gneiss and amphibolite. Porphyroblasts of garnet are common in both
the gneiss and granitoid patches.
A narrow 2 km long granitoid complex consisting of a
variety of leucocratic and mesocratic granitoid phases
as well as variably assimilated supracrustal rocks lies in
the west limb of the Carruthers Lake Synform.
Leucocratic granitoid lenses occur adjacent to the complex.
Irregular bodies of leucocratic granitoids also occur in
hornblende-plagioclase gneiss in the Carruthers Lake
Antiform. These are typically fine to medium grained,
pinkish buff weathering, and contain less than 15 per·
cent hornblende as well as a few percent magnetite and
minor garnet. Locally, at the contact of the granitoid, in
the hornblende-plagioclase gneiss, there is a zone a few
metres wide containing abundant wispy terminated lenses of epidote rimmed by plagioclase.
Granite/Granodiorite
In the core of the Carruthers Lake Antiform is a composite granodiorite-granite body that intruded
hornblende-plagioclase gneiss of Assemblage A. This intrusion consists of two phases:
1) A buff-weathering, medium-grained granodiorite composed of as much as 40 percent quartz and 2 to
3 percent fine-grained biotite in centimetre-long
linear clots.
2) The main phase, a salmon to pinkish buff-weather-
ing, medium-grained granite containing a few percent disseminated magnetite. Apophyses of granite
cut the granodiorite. Foliation and lineation are common to both phases.
Pegmatite
Irregularly-shaped and variably sized simple pegmatites
composed of garnet, muscovite, biotite, plagioclase,
quartz, and microcline intrude the granite/granodiorite
in the core of the Carruthers Lake Antiform and the immediately adjacent supracrustal rocks.
35
Similar, and probably related, pegmatites containing
beryl and tourmaline intrude supracrustal rocks south
and east of the granitic core of the antiform. More than
40 of these rare element pegmatites have been identified. They exhibit a broad range in size and morphology from tabular to lenticular-shaped bodies as much
as 150 m long and 12 m wide to irregular narrow veins.
The narrow veins are generally more beryliferous and
also tend to be more common away from the granitic
core of the antiform. Although usually massive, a few of
the beryl pegmatite veins have been deformed into
small scale folds coaxial to the Carruthers Lake Antiform.
5. Structure
For the purposes of structural analysis the Santoy Lake
area has been subdivided into eight structural domains I
to VIII (Figure 2).
Three episodes of deformation have been recognized.
These are correlated with the 01 to 03 events of Lewry
(1977) in the adjacent Glennie Lake map-area and the
02 to 04 events distinguished by Lewry et al. {1990) for
the broader region. The latter terminology was adopted
in this report. Evidence of the 01 of Lewry et al. (op cit)
was not recognized.
The 02 event is identified with the formation of the
prominent moderate to strong foliation visible
throughout much of the area. This foliation is axial
planar to small-scale tight to isoclinally folded felsite and
quartz veinlets and original compositional layering.
Some of these folds, which are most common in
domains I and VII, are intrafolial. Narrow continuous
high-strain zones defined by a marked increase in inten-
sity of foliation and a horizontal to subhorizontal stretching lineation have also been attributed to the D2 deformation. The only example of what is probably a largescale D2 structure, albeit modified by subsequent deformations, is the tight antiform in domain VII. 02 foliation
and the axes of small-scale 02 folds are axial planar to
this structure (Figure 3a).
03 is identified with folding of the 02 foliation into
moderately-plunging, major open to tight large-scale
north-northwest-, north-, and south-southeast-trending
folds. Examples of these structures include the southsoutheast-plunging Carruthers Lake Antiform (domain I;
Figure 3b) and the west limb of the north-plunging Carruthers Synform (domain JI; Figure 3d). Axes of smallscale folds and crenulations, as well as mineral and elongation lineations, are coaxial with these major structures
(Figures 3c and 3e). The foliation and mineral lineation
in the post 02 granite/granodiorite in the core of the Carruthers Lake Antiform is also attributed to D2 deformation. Locally small scale D2 folds have been refolded by
the 03 structures producing type 2 and type 3 interference structures (Ramsay, 1967). High-strain zones,
such as the major north-northwest trending ones, in
domain VI and at the boundary between domains I, Ill
and IV and domain JI are developed along the limbs of
the major 03 structures. Some of these are reactivated
02 structures. Elsewhere, such as at the Zone 2 gold
showing in domain VIII, 02 high-strain zones are folded.
The 03 fold in domain VIII is apparently deflected by the
Eyahpaise Lake Pluton, the northern contact of which is
just southwest of the study area (Budding and Kirkland,
1956; Lewry, 1977; Delaney, 1986, 1987).
The 03 folds are crosscut by steep to vertically dipping,
east-trending extension joints. Conjugate fractures,
which are symmetrically oriented to
the 03 fold axes, are also common
(Figure 3f). The late joints and fractures are mantled by alteration
STRUCTURAL DOMAIN S
haloes.
SANTOY LAKE" AREA
- - - --.::!
,):,------ (_
(,,/" (
\
I,
/,, ~'
J
:..ryt
.,.
,::·
L___ l
-----
10 :L W'
' 0
____L__l
0.'.:
1.J
i'
/ O kP.
The regional 04 event is identified
with closed flexural or flattenedfolds characterized by upright to
steeply inclined northeasterly strik·
ing axial surfaces (Lewry et al.,
1990). Evidence of 04 is preserved
only locally and most commonly as
small scale type 1 interference
folds in domains Ill, JV, and V and
rare folding of the 03 lineation in
domain I. The basin structure of
domain Ill is a large scale 04 structure. In this structure the plunge of
small-scale folds and mineral lineations changes from north-northwest
on the south side of the basin to
south-southeast on the north
(Figures 3g and 3h).
u
""
Figure 2 - Structural domains, Santoy Lake area.
36
Summary of Investigations 1992
Figure 3 b
Figure 3o
N
(
/~
(
o z -rol~5
• S-rold~
t I neo1 1 on A2 1mut I I
Mcon L,ricot ,on Plunqc
Mean
o MI neru I L I ne-a t Inn~
A Stre t i:;h i ng L 1ner,1 1o n
• Crenu lat ,on .~x , ~
Heon L1neot ,on l\z , muth
Meon L rneo t , on PI unge
a
155 2
25 g
Srna l I Sca l e rolds
Mean L ,neut, on ,'1z, rnu th
Meun L, r,eat,ori P .' ung~
2 "l
3'l 'I
158 7
33 5
Figure 3 - Selected stereonet plots from the Santoy Lake area. All nets were produced by the program 'Stereo ' from Rockware Inc.
Contour intervals were determined by a density calculation routine included with the program.
3a - Contoured poles to foliations in Domain VII; contour intervals are: 0.6 , 3.6, 6.5, 9.S, 12.4, 15.4, and 18.3 percent; 169 poles
are contoured.
3b - Contoured poles to foliations and trend and plunge of small scale folds in Domain I. Contour intervals are: 0.3, 3.4, 6.6, 9.7,
12.8, 15.9, and 19.0 percent. The axes of 81 folds are plotted; 300 poles are contoured.
3c - Trend and plunge of 175 mineral iineations, stretching lineations and axes of crenulations in Domain I.
3d - Contoured poles to foliations and trend and plunge of small scale folds in Domain II. Contour intervals are: 0.4, 3.4, 6.4, 9.4,
12.4, 15.4, and 18.4 percent. The axes of 72 folds are plotted; 233 poles are contoured.
Saskatchewan Geological Survey
37
F,gur e 3e
Figur e 3f
N
N
i\
\
~~o
o M,nero l L1nea1 ,ans
Mean L1neat 1an Az imu th
Mean L ir,eo1 , on PI unge
'l l
'l3 'I
Figur e 3 g
N
r
f
.,a
0
0 0 °
c
o S Fo lds
• ?· Fo lds
a Minero/ L1 neo t 1ons
Figure 3 - continued
3e - Trend and plunge of 142 mineral lineations in Domain II.
3f- Contoured poles to late joints and fractures throughout Santoy Lake area. Contour intervals are: 0.3, 2.9, 5.4, 8.0, 10.6, 13.1,
and 15. 7 percent; 344 poles are contoured.
3g - Contoured poles to foliations and trend and plunge of small scale folds in Domain Ill. Contour intervals are: 3.5, 6.9, 10.3,
13. 8, 17.2, 20. 7, and 24. 1 percent. The axes of 27 folds are plotted; 29 poles are contoured.
3h • Trend and plunge of 23 mineral lineations in Domain Ill.
6. Metamorphism
A detailed documentation of the metamorphic history of
the area will form a component of the thesis investigations by Durocher at the University of Saskatchewan.
Only a few preliminary observations are given here.
38
An early phase of metamorphic mineral growth is associated with the D2 event. This is defined by mineral
growths in the supracrustal and early granitoid rocks
parallel to the prominent D2 foliation and rare D2 lineation. In the basic to intermediate metavolcanic rocks
these mineral growths include biotite, hornblende, and
plagioclase. In the pelitic and psammopelitic rocks gar-
Summary of Investigations 1992
net, biotite, muscovite, hornblende and quartz are variably aligned to D2 fabrics. D2 foliation in the actinolitechlorite schist, is crenulated by Da fabrics. Preliminary
thin section examination reveals that, although
granoblastic to mimetic fabrics are common, some
original D2 fabrics prevail.
Syn- to post-03 amphibolite facies metamorphism has
also affected the Santoy Lake area. Products of this include mineral growth coaxial with major 03 folds and
the growth of undeformed porphyroblasts, such as the
undeformed garnet porphyroblasts throughout the Santoy Lake area, the undeformed, coarse-grained porphyroblasts of andalusite and sillimanite in the conglomerate, and the post 03 growth of undeformed amphibole in the actinolite-chlorite schist.
b) Beryl Pegmatites
At least forty pegmatites composed of microcline,
plagioclase, quartz, muscovite, garnet, beryl, and rare
tourmaline occur in supracrustal rocks east and south of
the granitic intrusion in the core of the Carruthers Lake
Antiform (Figure 1). Beryl-bearing pegmatites vary broadly in morphology and size from tabular- to lenticularshaped bodies up to 150 m long and as much as 12 m
wide, striking subparallel to the limbs of the Da Carruthers Lake Antiform and Synform, to thin irregular
veins that pinch and swell in thickness, and locally bifurcate. Although concentrations of rare elements are
probably subeconomic, there is some potential for gem
quality beryl.
8. Acknowledgments
7. Economic Geology
In addition to several significant gold showings, the Santoy Lake area also contains a suite of rare element pegmatites. A detailed description of the gold showings is
contained in the paper by Durocher et al. (this volume)
and the rare-element pegmatites are described in
another paper by Williams et al. (this volume). The following summarizes these two mineral associations:
a) Gold
The gold showings are associated with deformed barren
quartz veins in D2 shear zones in mafic or intermediate
volcanics of Assemblage A within 400 m of the contact
with Assemblage B. In some high-strain zones
mineralization is hosted in leucocratic granitoids. Some
of the mineralized high-strain zones are as much as
600 m long and 10 m wide.
Pyrite, chalcopyrite, bornite, arsenopyrite and gold are
commonly found along vein contacts, as minute disseminations in microfractures cutting the quartz veins, as
well as in, and adjacent to, sheared host rocks. Diopside, biotite, chlorite, sericite, and phlogopite occur as alteration products in the mineralized shear zones.
Epidote, hornblende, and plagioclase are common alteration minerals in the less deformed country rock.
Bulk channel samples from some of the showings have
returned significant grades. An example is the 8.2 m
wide channel sample from a folded part of Gold Zone 2
which yielded 19.2 g/t (0.56 oz/ton) Au , and the 3.4 m
wide sample from Gold Zone 6 that contains 31.2 g/t
(0.91 oz/ton) Au (Claude Resources and Manchester
Resources News Release, October 30, 1991 ). In addition to trenching, Gold Zone 2 has been tested by 4
diamond drill holes and Gold Zone 6 by 3 diamond drill
holes. The best intersections included a 2 m interval of
142.9 g/t (4.2 oz/ton) Au in Zone 2 and a 1 m interval
of 20 g/t (0.6 oz/ton) Au in Zone 6 (Claude Resources
and Manchester Resources News Release, May 4,
1992). A great deal of additional work is required to fully
evaluate the potential of the gold zones.
The authors would like to express appreciation to Lane
Dorsch, Andrew Wallace, Mike Webster, and Don Williams for their help during fieldwork.
9. References
Bennett, R.W. (1990a): Assessment Work Catalogue, Reindeer
River Area, Saskatchewan; Sask. Energy Mines, Misc.
Rep. 90-5, 283p.
-~---....-- (1990b): Assessment Work Catalogue, La Range
Alea, Saskatchewan; Sask. Energy Mines, Misc. Rep. 907, 380p.
_ _ _ _ {1991): Assessment Work Catalogue, Saskatchewan; Sask. Energy Mines, Misc. Rep. 91-6, 96p.
_____ (1992): Assessment Work Catalogue, Saskatchewan; Sask. Energy Mines, Misc. Rep. 92-6, 97p.
Budding, A.J. and Kirkland, S.J.T. (1956): The geology of the
Reindeer River area; Sask. Dep. Miner. Resour., Rep. 22,
42p (reprinted 1987).
Chiarenzelli, J.R. (1989): The Nistowiak and Guncoat Gneisses: Implications for the tectonics of the Glennie and
La Range domains, northern Saskatchewan, Canada;
Ph.D. Thesis, Univ. Kansas, 229p.
Delaney, G.D. (1986): Bedrock geological mapping Laonil
Lake area (part of NTS 63M-11 and -12); in Summary of Investigations 1986, Saskatchewan Geological Survey;
Sask. Energy Mines, Misc. Rep. 86-4, p32-40.
_ _ _ _ (1987): Bedrock geological mapping CarrulhersUskik Lakes area (part of NTS 63M-11 and -12); in Summary of Investigations 1987, Saskatchewan Geological
Survey, Sask. Energy Mines, Misc. Rep. 87-4, p8-17.
_ _ _ _ (1992): Gold in the Glennie Domain; Sask. Energy Mines, Misc. Rep. 92-5, 71p.
Hoffman, P.F. (1990): Subdivision of the Churchill Province
and extent of the Trans-Hudson Orogen; in Lewry, J.F.
and Stauffer, M.R., (eds.), The Early Proterozoic TransHudson Orogen of North America, Geol. Assoc. Can.,
Spec. Pap. 37, p15-39.
Hornbrook, E.H.W., Garrett, R.G., Lynch, J.J., and Beck, L.S.
(1975): Regional lake sediment reconnaissance data, eas1central Saskatchewan; Geol. Surv. Can., Open File 266,
108p.
Saskatchewan Geological Survey
39
_ _ _ _ (1977): Regional Jake sediment reconnaissance
data, east-central Saskatchewan; Geol. Surv. Can., Open
File 488.
Hornbrook, E.H.W., Lynch, J.J .. Friske, P.W.B., Lund, N.D.,
and Schmitt, H.R. (1985): Regional lake sediment reconnaissance data, east-central Saskatchewan; Geol. Surv.
Can., Open File 1129, 145p (8 maps).
Lewry, J., Thomas, D.J., Macdonald, R., and Chiarenzelli, J.
(1990): Structural relations in accreted terranes of the
Trans-Hudson Orogen, Saskatchewan: Telescoping in a
collisional regime?; in Lewry, J.F. and Stauffer, M.R.
(eds.), The Early Proterozoic Trans-Hudson Orogen of
North America, Geol. Assoc. Can., Spec. Pap. 37, p75-94.
Lewry, J.F. (1977): The geology of the Glennie Lake area;
Sask. Oep. Miner. Resour., Rep. 143, 59p.
Macdonald, R. (1981): Compilation bedrock geology: Pelican
Narrows and Amisk Lake areas; 1:250 000 scale prelim.
map with Summary of Investigations 1981, Saskatchewan
Geological Survey, Sask. Miner. Resour., Misc. Rep. 81-4.
Lewry, J.F. and Collerson K.D. (1990): The Trans-Hudson
Orogen: Extent, subdivision, and problems; in Lewry, J.F.
and Stauffer, M.A. (eds.), The Early Proterozoic Trans-Hudson Orogen of North America, Geol. Assoc. Can., Spec.
Pap. 37, p1-14.
McNicoll, V.J., Delaney, G.D., Parrish, R.R., and Heaman, L.H.
(in press): U-Pb sphene and zircon ages from the Glennie
Domain, Trans-Hudson Orogen, Saskatchewan; in
Radiogenic Age and Isotopic Studies: Report 6, Geol.
Surv. Can., Paper 92-2.
Lewry, J.F. and Sibbald, T.I.L (1977): Variation in lithology and
tectonometamorphic relationships in the Precambrian
basement of northern Saskatchewan; Can. J. Earth Sci.,
v14, p1453-1467.
Ramsay, J.G. (1967): Folding and Fracturing of Rocks; McGraw-Hill, Inc., 568p.
Lewry, J.F., Sibbald, T.1.1., and Rees, C.J. (1978): Metamorphic patterns and their relation to tectonism and
plutonism in the Churchill Province; in Fraser, J.A. and
Heywood, W.W. (eds.). Metamorphism in the Canadian
Shield, Geol. Surv. Can., Pap. 78-10, p139-153.
40
Rees, C.J. (1982): Metamorphism in the Canadian Shield of
northern Saskatchewan; Sask. Miner. Resour., Open Flle
Rep. 82-2, 136p.
Saskatchewan Geological Survey (1987): Saskatchewan's
mineral industry: Past and present; CIM Bull., Annu. Rev.,
v21, p67-114.
Summary of Investigations 1992