Geology of Walters and Leduc Townships; District of Thunder
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Mackasey, W.O. 1976. Geology of Walters and Leduc townships,
District of Thunder Bay; Ontario Division of Mines, Geological
Report 149, 58p.
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Ministry of Natural Resources
Ontario Division of Mines
HONOURABLE LEO BERNIER, Minister of Natural Resources Dr. J . K.
REYNOLDS, Deputy Minister of Natural Resources
G. A. Jewett, Executive Director, Division of Mines E. G. Pve,
Director, Geological Branch
Geology of
1976
and price list
Public Service Centre, Parl iament Buildings, Queen's Park, Toronto
, Ontario
and
T h e Ontario Government Bookstore
880 Bay Street, T o r o n t o , Ontario
Orders for publicat ions should be accompanied by cheque, or money
order, payable to Treasurer of Ontario.
Parts of this publ icat ion may be quoted if credit is g iven to
the Ontario Divis ion of Mines. I t is recommended that reference
to this report b e made in the fol lowing form:
Mackasey, W.O. 1976: Geology of Walters and Leduc Townships ,
District of T h u n d e r Bay; Ontario Div . Mines,
GR149, 58p. Accompanied by Map 2356, scale 1 inch to i/2 mi le
(1:31,680).
ii 1000-300-76-B
Abstract v
Introduction ' Mineral Exploration 1 Present Geological Survey 2
Acknowledgments 2 Means of Access 3 Previous Geological Work 3
Topography *
General Geology * Tab le of Lithologic Units 5
Early Precambrian 6 Metavolcanics and Metasediments 6
Mafic Metavolcanics ® Massive Lava 6 Pil low Lava ? Amygdaloidal
Lava & Volcanic Breccia 10 Pyroclastic Rocks H
Intermediate to Felsic Metavolcanics 11 Pyroclastic Rocks 12
Massive and Porphyritic Lava 13
Metasediments 13 Conglomera te 1 Sandstone, Siltstone, and Argill
ite 17 Iron Formation and Chert 20
Mafic Intrusive Rocks 22 Metagabbro, Diorite and Quartz Diorite 23
Mafic Dikes 24
Felsic Intrusive Rocks 25 Trondhjem ite 25 Feldspar and
Quartz-Feldspar Porphyry Dikes 26
Absolute Age of Early Precambrian Rocks 26 Middle to Late
Precambrian 26
Intrusive Rocks 26 Diabase Dikes 26 Feldspar-Quartz Porphyry
27
Cenozoic 28 Quaternary 28
Pleistocene 28 Structural Geology 30
Regional Structural Setting 30 General Relationships 30
Relationship to the Quet ico Belt 30
Folding 31 Major Structures 31 Minor Structures 32
Foliation 32 Minor Folds 32 Lineations 32
Fault ing 32 Paint Lake Fault 34 Jell icoe Fault 34 Other Faults 36
Age of Faults 36
Economic Geology 36 Gold Deposits 37
Quartz Veins 37
iii
Sulphide Mineralization 37 Relat ionship of Gold Deposits to
Geological Features 38
Sulphide Deposits 39 Relat ionship of Mineralization to Geological
Features 39
Iron Deposits 40 Sand and Gravel 40 Suggestions for Mineral
Exploration 40
Base Metals 40 Gold 41 Iron 42
Descriptions of Properties 42 Airways Occurrence (1) 42 Canorama
Explorations Limited [1961] (2) 44 Coniagas Mines Limited (3) " 44
Dajaty Gold Mines Limited (4) 45 Jorsco Occurrence (10) 46
Kenogamisis Gold Mines Limited [1950] (11) 46 Ledger, F. (5) 47 H.
K. Porter Company (Canada) Limited (6) 47 Solomon's Pillars Mines
Limited (7) 48 Warren Occurrence (8) 49 Wenzoski, J. (9) 50
Selected References 53 Index 57
TABLES
1-Table of Lithologic Uni ts 5 2-Complete rock and trace e lement
analyses of rocks from Walters and Leduc Townsh ips 9 3-Information
on work done on properties in Walters and Leduc Townsh ips 43
F I G U R E
1-Key map showing location of Walters and Leduc Townsh ips
vii
P H O T O G R A P H S
1-Pilotaxitic texture in metabasalt at Expansion Lake 7 2-Altered
interstitial glassy matrix in mane amygdaloidal lava south of Pasha
Lake 8 3-Quartz amygdules in mafic lava at Expansion Lake 10
4-Voicanic breccia on north shore of Kingston Island 11
5-Tuff-breccia north of Paint Lake 13 6-Crystal tuff southwest of
Expansion Lake 14 7-Photomicrograph of trachytic texture 14
8-Polymictic conglomerate east of Pasha Lake 16 9-Pebbly sandstone
in the central sedimentary belt, Beatty Lake 17
10-Detrital fragment of volcanic rock in greywacke 18
11-Interbedded greywacke sandstone, siltstone and argillite typical
of the southern sedimentary
belt 19 12-Photomicrograph of feldspathic greywacke standstone from
the southern sedimentary belt . . 19 13-Greywacke sandstone and
siltstone with thin ferruginous beds 21 1 4 - T h i n bedded chert
associated with mafic metavolcanics of Pasha Lake 22 15-Lamprophyre
from south shore of Paint Lake 24 16-Hybrid rocks a long the
contact of the granitic stock in Walters T o w n s h i p 25
17-Feldspar-quartz porphyry from north shore of Kingston Island
27
iv
18-Flow structure in feldspar-quartz porphyry north of Paint Lake
29 19-Glacial outwash material west of Paint Lake 29 20-Bedding cut
by cleavage east of Hal low Lake 33 21-Refraction of cleavage in
metasediments near Nissiamkikam Lake 33 22-Air photograph of Paint
Lake Fault l ineament 35 23-Deformed conglomerate on south shore of
Paint Lake 36 24-Replacement of cherty iron formation by pyrite and
arsenopyrite 38 25-Oremond headframe, Solomon's Pillars Gold Mines
Limited Property 49 26-Test pit on the Wenzoski property, Walters
Townsh ip 51 27-Arsenopyrite and gold bearing quartz vein on the
Wenzoski property, Walters Townsh ip . . .51
GEOLOGICAL MAP
(back pocket)
Map 2356 (coloured) — Walters and Leduc Townships , District of T h
u n d e r Bay Scale, 1 inch to i/ 2 mi l e (1:31,680).
V
ABSTRACT Walters and Leduc Townships comprise a 72 square mile (192
k m 2 ) area located about 15
miles (24 km) east of Lake Nipigon, and about 135 miles (220 km)
northeast of Thunder Bay. T h e report and Map 235G (back pocket)
out l ine the lithology, structural geology, mineral deposits, and
exploration history of the map-area.
Figure 1 -Key map s h o w i n g location of Walters and Leduc T o w
n s h i p s . Sca le 1 inch to 5 0 m i l e s ( 1 : 3 , 1 6 8 , 0 0
0 ) .
T h e area is underlain principally by Early Precambrian (Archean)
igneous and metamorphosed rocks. T h e oldest rocks are
metavolcanics and metasediments, which are intruded by
trondhjemite, quarlz-diorite, gabbro and related igneous rocks in
the form of stocks, lenses, and dikes. T h e metavolcanics range in
composition from mafic to felsic. T h e mafic metavolcanics are
dominantly massive, but zones of amygdules, pil lows, and breccia
are present. The intermediate to felsic metavolcanics underlie the
northern part of the map-area and consist of tuff-breccia,
thin-bedded tulf and porphyritic flows. Metasediments form three
east-trending belts that are separated by mafic metavolcanics. T h
e northern belt is predominantly conglomerate. T h e central belt
is formed of pebbly sandstone, conglomerate, siltstone and
argillite. T h e southern belt consists of inter- bedded argillite,
siltstone and greywacke sandstone. Middle to Late Precambrian
diabase dikes cut all rocks in the map-area. Pleistocene sand and
gravel deposits cover much of the bedrock.
T h e area forms part of the Wabigoon Belt of the Superior Province
and the Early Precambrian rocks have been tightly folded along
east-west axes. Well preserved primary sedimentary and volcanic
features are used to determine the super-position of strata.
Several prominent post-diabase faults are recognized.
vii
Gold, silver, iron, copper, lead, nickel, sand, and gravel are
present. Gold and associated silver occur in quartz veins and
sulphide deposits. Genetic relationships to igneous intrusion,
volcanism, iron formation and fault ing are considered. Base metal
sulphides occur in quartz veins and shear zones and are believed to
be associated with igneous activity. Some sulphides may be related
to fumerolic deposits. Iron is of sedimentary origin and is present
in thin-bedded deposits of chert, hematite , and magnetite .
Transportation, communications, and energy resources are available
for rapid development of mineral commodities . Exploration for
disseminated sulphide deposits related to granitic intru sions is
recommended for the region in general. Copper mineralization
related to Late Precambrian north-south faults may be present in
the vicinity of the Jell icoe Fault. Geochemical studies using
arsenic as a pathfinder e lement may be useful in gold exploration.
Iron deposits having low magnetite content may be present in the
map-area and may be best detected by gravity methods.
T h e iron deposits have been examined repeatedly since the turn of
the century. T h e first significant discovery of gold in the
region was in 1925 and this commodity has since provided the main
interest in exploration. Exploration for sulphide deposits has
become increasingly active in more recent years. Details of
individual properties and mineral deposits are described.
viii
District of Thunder Bay b y
W . O . M a c k a s e y 1
INTRODUCTION
Walters and Leduc Townships are located east of Lake Nipigon and
form part of the 'Sturgeon River Gold Belt' (Bruce 1936; Laird
1936). The city of Thunder Bay is 135 miles (220 km) to the
southwest via Highway 11. The settlement of Jellicoe, formerly a
railway switching yard town, is located in the southern part of
Leduc Township. M I N E R A L E X P L O R A T I O N
Gold has been one of the main interests in the region since its
discovery near Beardmore in 1925. Iron, and more recently, sulphide
deposits have been under investigation.
Geological mapping, geophysical surveying, trenching, sampling, and
diamond drilling for gold have been carried out in many parts of
the map-area over the past 30 years. In 1936, a pilot shaft on the
former Oremond Gold Mines Limited property was completed to a depth
of 300 feet (100 m). Solomon's Pillars Mines Limited acquired this
property and in 1968, commenced a diamond drill program. The
Sturgeon River gold mine, 2,000 feet (600 m) west of Walters
Township, was in production from 1937 to 1942.
Sulphide occurrences are numerous and some have been tested by
trenching and diamond drilling as well as by geophysical
techniques. In 1962-63, Jorsco Ex plorations Limited completed a
total of 22 diamond drill holes on a gold-silver- copper prospect
north of Blackwater Lake.
iF ie ld geologist, Ontario Division of Mines, Toronto . Manuscript
approved for publication by the Chief Geologist, March
6,1975.
1
PRESENT GEOLOGICAL SURVEY
The present geological survey was undertaken during the 1968 field
season with the purpose of making a detailed examination of the
geology and mineral resources of Walters and Leduc Townships.
Mapping was by pace-and-compass traverses aided by the use of air
photographs. Traverse spacing was approximately one quarter mile
(0.4 km). Shoreline traverses were run on most of the lakes and
rivers in the map-area.
Traverses were tied into recognizeable features such as roads,
streams and lakes. Surveyed lines, including township boundaries
and surveyed claim lines were not useful as in most cases they were
grown over or obliterated by slash from logging operations.
Additional geological data was obtained from air photographs on
scales of 1 inch to 14 mile (1:15,840) and 1 inch to 1 mile
(1:63,360) supplied by the Air Photo Libraries, Ministry of Natural
Resources and Federal Department of Energy, Mines and Resources,
aeromagnetic maps, and reports and maps of various mining
companies.
The geological maps of the area were prepared at a scale of 1 inch
to y4 mile (1:15,840) for publication at a scale of 1 inch to i/2
mile (1:31,680), using base maps issued by the Cartography Section,
Division of Lands from the Forest Resources Inventory, Ministry of
Natural Resources.
Uncoloured preliminary geological maps P.539, and P.540 of the area
on a scale of 1 inch to yA mile (1:15,840), were issued in 1969 by
the Ontario Department of Mines.
ACKNOWLEDGMENTS
The author was assisted in the field by R. A. Morgan, W. T.
Fleming, E. R. Owen, and P. Rae Teal. Mr. Morgan, serving as senior
assistant, mapped about half the area. Messrs. Fleming, Owen, and
Teal ran independent traverses during the later part of the field
season.
The many courtesies extended by Mr. and Mrs. Clayton Doucette of
Collimar Lodge, Jellicoe, were greatly appreciated by the field
party. Mr. L. F. Morrison, Jellicoe and Robert Finnen, Beardmore
supplied information on some of the properties within the
map-area.
2
In 1968, geological and geophysical surveys were conducted by
Federal Wire and Cable Company in Walters Township. The company
held a group of claims north of Paint Lake at the end of the 1968
field season.
Some stripping for iron formation was done in the map-area. Central
Manitoba Mines Limited investigated the iron formation in the
Watson-Doris Lake area. A total of four diamond drill holes were
completed in the Watson Lake area, Irwin Township in 1957.
Several claim groups, including patented and leased claims were
held in the map-area during the 1968 field season.
Mr. Ron Kincaid, Chief Forest Ranger, Ontario Department of Lands
and Forests, MacDiarmid, and his staff, supplied information
concerning the map-area.
MEANS OF ACCESS
Highway No. 11, the northern route of the Trans Canada Highway,
passes through the southern part of the map-area. Secondary Highway
801 crosses diago nally northwest through Walters Township.
Although a few old lumber roads and trails are present, the main
access through most of the map-area is by means of lakes and
rivers.
The Canadian National Railway Line and Trans-Canada natural gas
pipeline parallel Highway 11 in the south part of the map-area. An
airport having a 3,000 foot long compacted gravel runway is located
north of Blackwater Lake in Leduc Township. Float aircraft
facilities are located nearby at Rolland Lake. Charter aircraft
facilities are available.
Accommodation, supplies, and postal services are available within
the map-area and at the nearby towns of Beardmore and
Geraldton.
PREVIOUS GEOLOGICAL WORK
According to Laird (1936, p.63), Robert Bell of the Geological
Survey of Can ada, and his assistant Peter McKellar, undertook the
first recorded geological work in the region in 1869. Laird also
states that other early workers of the Geological Survey of Canada
in the area were W. Mclnnes, 1894; D. B. Dowling, 1898; and W. A.
Parks in 1901. The Ontario Bureau of Mines conducted studies of the
iron deposits in the region in 1906 and 1907 (Coleman 1907; Moore
1907). A. W. G. Wilson in 1908 completed the field work started by
the Federal government, the results of which form Memoir 1, of the
Geological Survey of Canada, published in 1910.
A. G. Burrows examined the geology along the railway line in the
Beardmore- Nezah area in 1916 for the Ontario Bureau of Mines
(Burrows 1917).
The Windigokan Lake area and the railway to the south were mapped
in 1917 by the Geological Survey of Canada (Tanton 1921). G. B.
Langford mapped this area in greater detail in 1927 (Langford
1928).
Volume 45, Part 2, 1936 of the Ontario Department of Mines, by E.
L. Bruce and A. C. Laird, forms a comprehensive report on the
geology and mineral deposits of the area. Other, more recent
workers in the region were Horwood and Pye (1951), Peach (1951) and
Pye (1951). A geological compilation map (Map 2102) of the
Tashota-Geraldton area was published by the Ontario Department of
Mines (Pyeetal. 1966).
In 1967, the author commenced a mapping program of the townships in
the Beardmore-Jellicoe area for the Ontario Department of Mines and
Northern Affairs (Mackasey 1969a, b; 1970b, c; 1971; 1975).
3
The main topographic features within the map-area, with
modification by Pleistocene deposits, can be directly related to
the bedrock geology.
The dominant structural trend is reflected by two relatively
resistant mafic metavolcanic belts that form parallel ridges
trending east-west across the town ships. The valley lying between
the ridges is underlain by metasediments less re sistant to
erosion than the metavolcanics. Glacial deposits of sand and gravel
in this valley have produced a disrupted drainage system resulting
in a high number of irregular shaped sandy bottomed lakes. In some
areas, especially north of Oxaline Lake, the mafic metavolcanic
ridges are rugged, due to the presence of numerous parallel,
narrow, swamp filled depressions.
The terrain underlain by metasediments in the southern part of the
map-area, and by metavolcanics and felsic intrusive rocks to the
north, have a more gentle, rolling relief, with many of the lower
lying areas being covered by swamps.
The map-area is drained by four major lake and river systems, all
of which eventually make their way to Lake Nipigon. The
Namewaminikan (Sturgeon) River flows west through the north part of
Leduc Township and turns north at Paint Lake to take a course
around the granitic stock in Walters and Elmhirst Townships. At one
time the Namewaminikan River probably flowed west through Paint
Lake.
Oxaline Lake drains east and then north into Coral Lake and the
Namewam inikan River. Blackwater River and a tributary,
Nissiamkikam Creek drain the south part of the map-area. Foxear
Creek and the related chain of lakes in the central part of the
townships, drain west to join up with the Namewaminikan River in
Sandra Township.
GENERAL GEOLOGY
Walters and Leduc Townships are underlain by east-trending, folded
and faulted Early Precambrian, Keewatin-type mafic and felsic
metavolcanics and Tim- iskaming-type metasediments.
The metasediments form three belts which trend east across the
map-area. The north belt is dominantly conglomerate; the central
belt comprises blocky sandstone, conglomerate, siltstone, and
argillite; the third and southernmost belt consists of interbedded
argillite, siltstone, and greywacke.
The sedimentary belts are separated by parallel trending belts of
mafic meta volcanics in which the flows are generally massive.
However, bands of deformed pillows, amygdaloidal zones, and breccia
do occur. An exposure of intercalated lava and conglomerate was
observed in north-central Leduc Township.
The intermediate to felsic metavolcanic belt along the northern
boundary of the map-area includes tuff-breccia with interbedded
thin-bedded tuff, chloride lava,
4
Table 3 lists assessment work data on file with the Ontario
Division of Mines as of December 1968.
and massive to laminated flows. Mafic lava is interfingered with
intermediate to felsic lava in the Expansion Lake area.
A felsic stock intrudes the volcanic rocks in northwestern Walters
Township. Diorite and quartz diorite cut sedimentary and volcanic
rocks at Oxaline Lake. Some of the mafic rocks in the area may be
either fine-grained intrusions or coarse grained centres of flows.
North striking diabase dikes of Middle to Late Precam brian age
are present throughout the map-area.
Pleistocene deposits of sand, gravel, and clay; as well as, recent
lake, stream, and swamp deposits, cover parts of the
map-area.
The geological history is summarized in Table 1.
Table 1 T A B L E OF L I T H O L O G I C U N I T S FOR T H E W A L
T E R S - L E D U C AREA
PHANEROZOIC CENOZOIC
QUATERNARY RECENT
Sand, gravel, and clay Unconformity
PRECAMBRIAN MIDDLE T O L A T E P R E C A M B R I A N
MAFIC INTRUSIVE ROCKS Diabase and minor related granophyre
Intrusive Contact Porphyritic diabase
Intrusive Contact EARLY P R E C A M B R I A N
FELSIC INTRUSIVE ROCKS Trondhjemite and related hybrid felsic
rocks, feldspar porphyry, quartz-
feldspar porphyry Intrusive Contact
Intrusive Contact METAVOLCANICS AND METASEDIMENTS
METASEDIMENTS Feldspathic sandstone, greywacke sandstone,
siltstone, argillite, polymictic
conglomerate, chert, iron formation Intercalated in part
INTERMEDIATE TO FELSIC METAVOLCANICS Tuff-breccia, pyroclastic
breccia, tuff and tuffaceous schist, massive and
amygdaloidal lava, feldspar porphyry, quartz-feldspar porphyry
Intercalated in part
MAFIC METAVOLCANICS Massive lava, amygdaloidal lava, pi l low lava,
flow breccia and agglomerate,
tuff and tuffaceous schist
MASSIVE LAVA
Lava, in the form of massive flows, is considered to be the
dominant rock com ponent of the mafic metavolcanic belts in the
area. However, this conclusion is based upon limited bedrock
exposure.
These metamorphosed massive lavas are exposed as smooth
structureless out crops. Plagioclase laths arranged in a
pilotaxitic texture can be observed on some clean, weathered
surfaces.
Some of the massive mafic lava exposures were found to be
relatively coarse grained. Most of these outcrops are in proximity
to rocks displaying primary vol canic features such as amygdules
and pillows and were interpreted as representative of the centres
of flows. It must be conceded, however, that some of these coarser
grained rocks may be narrow fine-grained gabbroic sills. In
particular, areas shown as coarse-grained lavas on Map 2356 (back
pocket) in the vicinity of Blackwater and Blue Lakes, Leduc
Township, lack typical volcanic features and may actually be mafic
intrusions.
Thin section study of the massive rocks revealed that most of the
original min erals have been completely altered to or replaced by
saussurite, chlorite, epidote
6
Mafic Metavolcanics
Mafic metavolcanic rocks dominantly of andesitic and basaltic
composition form two, major, east-trending belts. Smaller bodies of
mafic flows occur in the south eastern corner of Leduc Township,
and some andesitic flows are interbanded with intermediate to
felsic metavolcanic rocks in the Expansion-Paint Lake area.
The metamorphosed lavas vary from dark green to greyish green and
are gen erally fine-grained. Individual flows could not be
delineated but the presence of amygdaloidal and pillowed zones
indicate that the volcanic pile is composite.
Primary features such as pillows and amygdules are moderately
deformed. Tuf- faceous horizons and scoria zones are sheared to a
greater extent. Moss, lichen, and other vegetal material quite
easily conceal these primary features.
The metavolcanics and metasediments in the area have been
regionally meta morphosed to greenschist facies rank. The mafic
metavolcanics contain abundant chlorite and saussuritized
plagioclase, as well as, epidote, quartz, amphibole, py roxene,
calcite, and minor amounts of magnetite and sulphides. The
plagioclase occurs in the form of phenocrysts and tiny laths.
Relict pilotaxitic texture can be observed in some thin
sections.
Thin discontinuous layers of chert, with minor amounts of magnetite
and py- rite, and sulphide iron formation are interbedded with the
mafic metavolcanic flows. The chert and associated rocks are
described in the section dealing with metasediments.
ODM9350
Photo 1-Photomicrograph of pilotaxitic texture in amygdaloidal
metabasalt. Expansion Lake, Leduc Township. Crossed nicols.
and carbonate. In most thin sections original features such as
pilotaxitic and glassy textures and flow structures are preserved
as shown in Photos 1 and 2.
Plagioclase is present as euhedral laths in the range of 0.1 to 0.5
mm long with some up to 1 mm long. In most samples the crystals are
completely saussuritized but some plagioclase laths with distinct
albite twinning are present in many of the thin sections examined.
Using the Michel-Levy method these twinned grains were determined
to be albite. One thin section was found to contain
oligoclase.
Amphibole, probably after pyroxene, forms 1 to 4 mm grains that
enclose saus suritized feldspar laths in the order of 0.5 mm long.
Magnetite, leucoxene, pyrite and apatite are common accessory
minerals.
PILLOW LAVA
Mafic pillow lavas are common throughout the map-area and indicate
that much of the mafic volcanic succession was deposited under
sub-aqueous conditions.
The pillows generally range in size from 2 to 3 feet (0.6 to 1 m),
but some, longer than 4 feet (1.3 m) were observed. Most pillows
are closely packed and show slight to moderate deformation having
their longest axis parallel to the plane of foliation. Selvages are
dark green and aphanitic, and generally 2 to 4 cm thick. Amygdules
are usually present.
7
O D M 9 3 5 !
Photo 2-Photomicrograph ot altered interstitial glassy matrix in
mafic amygdaloidal lava. Highway 8 0 1 , south of Pasha Lake.
Walters Township. Laths are altered plagioclase. Crossed
nicols.
Pillows suitable for structural top determinations are rare due to
deformation, and to the absence of well defined cusps on the
pillows. Pillows found by the field party in the region south of
Paint Lake were not suitable for top determination. Bruce (1936, p
. l l ) in describing his observations south of Paint Lake, states
that top determinations shown on the map (45A) may not be
reliable.
The results of a chemical analyses (analysis by the Mineral
Research Branch) of a metamorphosed mafic pillow lava from a small
peninsula in the southeastern corner of Expansion Lake is listed in
Table 2. Using the classification of Irvine and Baragar (1971) this
rock is a tholeiitic basalt. The pillows at this locality are
lobate with long axis three to four times greater than the short
axis, and are without cusps. As secondary deformation to produce
significant stretching was not apparent in this exposure, it is
possible that these structures may be buds or small tubes as
sociated with a pahoehoe flow.
Pillows were found by Bruce (1936, p. 16) in the mafic volcanics
south of Jellicoe.
AMYGDALOIDAL LAVA
Amygdules are invariably present throughout the mafic lava
succession in both pillowed sections and in massive flows. Although
amygdaloidal zones probably cor respond to the tops of flows, no
evidence was found to confirm this.
8
I COMPLETE ROCK A N D T R A C E E L E M E N T ANALYSES OF ROCKS F R
O M Table 2 W A L T E R S A N D L E D U C T O W N S H I P S .
l
1 2 3 4
MAJOR C O M P O N E N T S I N P E R C E N T
S i O , 5 4 . 6 5 5 . 0 6 3 . 0 8 2 . 0
A 1 , 0 , 1 5 . 3 1 7 . 4 1 6 . 6 9 . 4 0 Fe*0» 3 . 5 3 2 . 3 8 2 .
0 0 0 . 6 6
FeO 4 . 8 5 5 . 4 7 4 . 0 6 0 . 4 5 M g O 5 . 0 3 3 . 4 8 2 . 2 8 0
. 1 4 C a O 8 . 0 8 4 . 3 5 3 . 4 6 1 .58 N a 2 0 3 . 6 7 1 .67 3 .
2 9 2 . 3 0 K 2 0 0 . 5 1 2 . 7 0 1 .93 3 . 2 9 H , 0 + 1.72 3 . 2
4 2 . 4 5 0 . 2 8 H 2 0 - 0 . 2 1 0 . 2 4 0 . 1 2 0 . 0 5 C 0 2 0 .
2 6 1 .10 1 .80 0 . 2 4 TiOt 0 . 7 5 0 . 6 5 0 . 4 5 0 . 1 0 PlOs 0
. 1 7 0 . 3 0 0 . 1 2 0 . 0 2 S 0 . 0 6 0 . 0 1 0 . 0 2 0 . 1 0 M n
O 0 . 1 5 0 . 1 3 0 . 1 7 0 . 0 1
T O T A L 9 8 . 9 9 8 . 1 1 0 1 . 8 1 0 0 . 6
Specific Grav i ty 2 . 9 4 2 . 7 4 2 . 7 3 2 . 6 4
T R A C E E L E M E N T S I N PPM
A g < 1 < 1 < 1 — A s — — — B a 150 500 330 800 C o 25 20
9 < 5 Cr 300 40 40 15 C u 60 20 20 20 G a 30 40 30 5 Li 20 20 —
— N i 100 50 25 20 P b < 1 0 < 1 0 < 1 0 10 Sb 6 6 8 Sc 60
< 2 0 20 — Sr 200 200 200 50 V 250 150 100 < 1 0 Y 30 — — 30
Zn 70 100 120 20 Zr 150 150 150 200
Sample 1. Sample M-68-11-223, mafic pillow lava, peninsula in
southeastern corner of Expans ion Lake, Leduc Township .
2. Sample M-68-11-61, tuff-breccia or agglomerate, H i g h w a y
801,1}4 mi le south of the Elmhirst-Walters Townsh ips boundary,
Walters Townsh ip .
3 . Sample M-68-11-215, feldspar porphyry flow, H i g h w a y 801,
}4 m » e south of the Elmhirst-Walters Townsh ips boundary, Walters
Townsh ip .
4 . Sample M-70-3-321, chert associated wi th mafic flows, H i g h
w a y 801, J^mile north of Pasha Lake, Walters Township .
^ e , M o , and Sn were looked for but no t detected . A s and Sb
were not looked for in sample 4.
Walters and Leduc Townships
ODM9352
Photo 3-Photomicrograph of quartz amygdules in mafic lava,
Expansion Lake, Leduc Town ship. Crossed nicols.
Most of the amygdules are only slightly deformed and the original
well rounded spheroidal shape easy to recognize as can be seen in
Photo 3. The diameter of the amygdules is generally between 0.5 to
1 cm, however a zone of augen shaped quartz amygdules about 3 cm
long was found in sheared mafic lava along the south shore of the
small unnamed lake between Beatty and Leduc Lakes.
Quartz, carbonate and chlorite are the most abundant mineral
fillings in the amygdules and occur both separately or as composite
assemblages. Jasper is present in amygdules in an exposure of mafic
lava on Highway 801 near Hallow Lake, Walters Township. Well
developed banded agate structure is visible in thin section.
VOLCANIC BRECCIA
A series of prominent outcrops of volcanic breccia occur along the
north shore of Kingston Island, Expansion Lake and the adjacent
peninsula to the west in Leduc Township.
This breccia as shown in Photo 4 consists of an extremely poorly
sorted agglom eration of chips, angular blocks and subrounded
lobate fragments of partially sco- riaceous mafic lava. The
exposures are characterized by a well pronounced differ ential
weathering of the finer matrix.
Some of the lobate forms are not unlike pillows in general
appearance. The lack of sorting, heterogeneous mixing of angular
and subrounded material, corn-
10
ODM9353
Photo 4—Volcanic breccia on north shore of Kingston Island.
Expansion Lake. Leduc Township.
hiued with the apparent uniformity in lithological composition of
the (lasts suggests that this breccia may represent part of an Aa
flow.
A small exposure of flow breccia was found north of the small lake
lying north of Pasha Lake, Walters Township.
PYROCLASTIC ROCKS
Pyroclastic rocks of mafic composition are rare in the map-area and
form only isolated occurrences. A few thin beds of fine-grained
tuff were found north of Ox aline Creek, Leduc Township.
Agglomerate composed of irregular shaped mafic volcanic bombs
suspended in chlorite schist occurs with mafic lava on a small
island at the turn in the Namewaminikan River, Walters
Township.
Intermediate to Felsic Metavolcanics
Intermediate to felsic volcanics are present north of the Paint
Lake Fault and are a continuation of the belt underlying the
adjoining townships to the west (Mackasey 1975).
11
PYROCLASTIC ROCKS
Pyroclastic rocks are distributed throughout the entire
intermediate to felsic metavolcanic succession. Although not as
well exposed as in the townships to the west (Mackasey 1975)
diagnostic features such as bedding and clastic texture could be
found.
Bombs and lapilli in the tuff-breccia generally range from 6 to 25
cm in maxi mum dimension. Most bombs are elongate or "cigar"
shaped and aligned parallel to regional foliation. Photo 5 shows an
exposure of typical tuff-breccia. The feathery nature of the clasts
is believed to be a primary plastic flow feature rather than being
of structural deformation origin.
A sample of fragmental rock that is either tuff-breccia or
agglomerate was chemically analysed by the Mineral Research Branch
and results are shown in Table 2. A silica content of 55.0 percent
is generally considered too low for rocks of intermediate to felsic
composition. This sample was collected from an area close to some
small mafic lenses and may have been contaminated by these
intrusions.
Tuff and crystal tuff forms thin bedded units that are intercalated
with tuff- breccia. Scattered lapilli fragments and bombs occur
from place to place within the tuffs.
Thin section study of bedded tuff near the rapids on the
Namewaminikan River in the northeastern corner of Leduc Township
revealed that the rock has been completely recrystallized to a very
fine grained mixture of saussurite, chlorite, and sericite along
with tiny grains of epidote and quartz. Tightly folded, thin bedded
tuff intercalated with two-foot (0.6 m) thick crystal tuff beds in
the northern part of the Namewaminikan River, Walters Township, was
found to contain broken pla gioclase laths and rounded
inclusion-rich quartz phenocrysts suspended in a ran domly
oriented quartzofeldspathic microcrystalline groundmass.
Crystal tuff beds enclosing 2 to 5 cm (34 to 2 inches) thick cherty
tuff lenses up to 20 cm (8 inches) long, were observed in Walters
Township on the north shore of the channel flowing from Expansion
Lake. The crystal tuff (see Photo 6) is com posed of up to 40
percent albite phenocrysts, ranging from less than 0.15 up to 2 mm
in greatest dimension, which are suspended in a cryptocrystalline
matrix. Minor amounts of epidote, chlorite, carbonate, and apatite
are also present in the groundmass.
12
The rocks are predominantly tuffaceous in marked contrast to the
mafic flows south of the Paint Lake Fault. Tuff-breccia, crystal
tuff, tuff and porphyritic flows are the most important rock types.
Amygdaloidal flows were found along Highway 801 and on the north
turn of the Namewaminikan River, Walters Township. Schistose rocks
associated with deformed tuff-breccia in this belt are believed to
have originally been of tuffaceous origin.
The metavolcanic rocks range in colour from shades of light green
to greyish green on fresh surface. Weathered surfaces are
characteristically rough and have a bleached or faded green
colour.
A transition from mafic flows and agglomerates through to
intermediate to felsic pyroclastic and flow rocks occurs across
strike in the region between Paint and Expansion Lakes.
ODM9354
Photo 5-Tuff-breccia at road cut on Highway 801 north of Paint
Lake, Waiters Township. Note feathery edges of large suspended
bombs. Face of outcrop lies sub-parallel to plane of
foliation.
Bedding about 0.5 mm thick, is apparent in the lenses of cherty
tuff which is composed of feldspar and quartz chips in the 0.01 to
0.02 mm range along with chlorite and cryptocrystalline
quartzofeldspathic material (Photo 6). Based on the presence of
bedding, broken crystals, poor sorting and open framework, this
crystal tuff has been classed as an ash fall product.
MASSIVE A N D PORPHYRITIC LAVA
Massive and porphyritic lavas are present throughout the
intermediate to felsic volcanic succession. Most of these lavas are
structureless in outcrop and it is possible that some exposures may
be fine-grained intrusions rather than flows. Some also may be of
tuffaceous origin with primary features destroyed by shearing. The
more massive to porphyritic rocks are brittle, being well fractured
rather than sheared.
These massive flows generally consist of variable amounts of quartz
and plagioclase phenocrysts suspended in a microcrystalline
groundmass that commonly displays a trachytic texture as shown in
Photo 7. The matrix is dominantly pla gioclase with lesser amounts
of quartz and little or no mafics. Sericite, epidote, and carbonate
are the most common alteration products.
13
ODM9355
Photo 6-Photomicrograph of crystal tuff from the north shore of the
channel flowing from Expansion Lake, Walters Township. Crossed
nicols.
Feldspar porphyry found near Highway 801 in the northwestern corner
of Walters Township is made up of approximately 30 percent altered
plagioclase phenocrysts up to 2 mm long with the remainder of the
rock being a groundmass of microcrystalline quartzofeldspathic
material along with sericite, epidote, chlorite and carbonate. A
chemical analysis, by the Mineral Research Branch, Ministry of
Natural Resources, of the feldspar porphyry is listed in Table
2.
An amygdaloidal intermediate lava which outcrops near the north
bend in the Namewaminikan River, is comprised of 10 percent albite
and a minor amount of quartz phenocrysts 0.3 to 1.5 mm in maximum
dimension. The groundmass is made up of plagioclase microlites
about 0.05 mm long, exhibiting a sub-trachytic texture that wraps
around carbonate amygdules.
METASEDIMENTS
The metasediments comprise three broad east-west striking belts
separated by metavolcanic rocks. The northernmost belt extends from
the south shore of Paint Lake eastward across the map-area to the
vicinity of Coral Lake and consists domi- nantly of polymictic
conglomerate with minor amounts of sandstone. The central belt is
made up of variable amounts of intercalated polymictic
conglomerate, sand stone, siltstone and argillite; while the
southernmost belt is predominantly a monotonous assemblage of
greywacke sandstone, siltstone and argillite with minor iron
formation.
These sediments are believed by the writer to have been related to
the same depositional basin and to have formed a laterally
continuous succession before folding (see Structural Geology). The
conglomeratic rocks of the northern belt were probably deposited
close to their erosional source, and the finer grained, thick
southern belt succession of greywackes deposited further out in a
basin to the south.
Conglomerate was found interbedded with mafic lava in Leduc
Township between Leduc Lake and the Namewaminikan River.
It should be noted that these sediments represent the type area for
Tanton's 'Windigokan Series' (Tanton 1921). This classification is
however no longer in use. Pye (1968b, p. 12) has found sediments of
similar character along the projected strike on the west side of
Lake Nipigon.
Conglomerate
The best exposures of conglomerate are located along the south
shore of Paint Lake, south of Bush Lake, south of Coral Lake, and
in the Leduc Lake area.
The conglomerate in the map-area is dominantly polymictic in
character (Photo 8) being composed of pebbles and boulders of
granitic and volcanic material along with clasts of argillite,
quartz, and jasper. The conglomerate is poorly sorted and the
clasts generally show a high degree of rounding and close packing.
The matrix is feldspathic sandstone ranging from medium to
coarse-grained. Inter calated one to two foot (0.3 to 0.6 m) thick
feldspathic sandstone layers are common in conglomerates of the
central sedimentary belt.
15
ODM9357
Photo 8-Typical exposure of polymictic conglomerate. Highway 801
just east of Pasha Lake. Walters Township.
Shearing and deformation related to the Paint Lake Fault have
stretched the boulders and pebbles of the northern belt so that in
some localities the rock takes on a gneissic appearance. The
interbedded sandstone layers in this area are generally altered to
quartz-sericite schists.
In a study of conglomerates in the Beardmore region, Callander
(1970, p.50) concludes that the majority of the clasts are volcanic
in origin with granitoid material making up as much as 35 percent
of the remainder. One notable feature about clast composition is
the apparent absence of material of metamorphic origin. Most of the
conglomerate is composed of supracrustal material that is probably
of local origin.
Jasper pebbles, although comprising only a very low percentage of
the clasts, were found to be helpful in the recognition of deformed
conglomerate. The jasper fragments stand out quite noticeably and
show up the clastic nature of the sheared rocks.
On the south shore of Oxaline Lake, Leduc Township, conglomerate is
inter bedded with lean iron formation, as was found further west
along strike in Irwin Township (Mackasey 1975, p.20 and Photo 11)
and Summers Township (Mackasey 1970c).
A thin band of mafic lava believed to be 25 to 50 feet (7.5 to 15
m) thick, occurs within conglomerate near a small lake about of a
mile (1.2 km) north of the west arm of Leduc Lake. The lava is in
direct contact with the conglomerate. This rela tionship appears
to be the result of interstratification rather than the result of
intrusion or faulting, but no evidence of chilling was noted. The
contact was ob served at only one location.
16
ODM9358
Photo 9-Feldspathic sandstone with pebbly bed in the central
metasedimentary belt. Beatty Lake, Leduc Township. Note blocky
nature of outcrop.
A small lens of conglomerate, composed of well rounded pebbles of
volcanic composition, occurs within the mafic lavas near a pond
that drains into the north side of Leduc Lake. This has been shown
as a narrow band of conglomerate on the map, however it is
frequently difficult to determine the epiclastic or pyroclastic
origin of this volcanoclastic material and it is possible that the
clastic material shown on the map at the west end of the lens is of
pyroclastic origin.
Sandstone, Siltstone, and Argillite
Sandstone, siltstone, and argillite constitute more than half the
bulk of the metasediments of the central belt and almost the entire
succession in the southern belt, and may be classed as two
groups.
The first group consists of medium- to coarse-grained feldspathic
sandstones, and related finer grained rocks associated with the
conglomerates, and are confined mainly to the central and northern
sedimentary belts. The second group is more akin to a greywacke or
turbidite succession and is the dominant rock in the southern
belt.
The feldspathic sandstone is characteristically massive, medium
grey, fairly resistant to erosion, and forms large smooth blocky
jointed outcrops and outcrop ridges. This sandstone occurs with
conglomerate and has thin pebbly layers through out as shown in
Photo 9. Small-scale crossbedding was observed at Beatty
Lake.
17
OOM935?
Photo 1 0 Photomicrograph of sandstone with lithic clasts of
detrital volcanic material. Crossed nicols.
Tiny angular chips of jasper can commonly be recognized in hand
specimen. In thin section the sandstone is seen to consist of
angular to subrounded, moderately sorted, medium to coarse sand
size clasts. The main constituents are quartz, plagioclase, and
lithic fragments of detrital volcanic material and chert (Photo
10). Matrix does not exceed 15 percent and is mainly a fine-grained
mixture of quartz, sericite, carbonate and unidentified clay-sized
alteration minerals. Using Pettijohn's classification (1957) these
rocks fall on the boundary between arkosic and lithic
sandstone.
A narrow unit of thin bedded, medium to dark grey, very fine
sandstone, silt stone and argillite associated with the
feldspathic sandstone occurs along the south ern margin of the
central belt and serves as a marker horizon between the central
sedimentary belt and the volcanics to the south. In some outcrops
of this unit a distinctive lineation pattern is formed by the trace
of bedding along cleavage planes.
The second type of sediment consists of grey, thin bedded,
greywacke sandstone interlayered with laminated to thin bedded
silt, slate and argillite as shown in Photo 11. Graded bedding is a
dominant feature and channeling, rafted argillite chips, and flame
structures are visible on some clean outcrop surfaces.
These sediments are generally well exposed in the southern belt,
especially in road cuts along Highway 11 and 801. The latter
exposures provide a good cross- section of this belt.
In thin sections the greywacke sandstone is seen to be poorly
sorted with angular to subrounded fragments (Photo 12) ranging from
0.05 to 0.6 mm in diameter. The
18
O0M93A0
ODM9361
19
Walters and Leduc Townships
Iron Formation and Chert
Iron formation and related ferruginous rocks in the area were
studied by A. P. Coleman and E. S. Moore in 1906 and 1907 (Moore
1907; Coleman 1908). Detailed descriptions are given in their
reports.
The iron formation mapped in Walters and Leduc Township occurs
along or near the north margin of the southern sedimentary belt.
These ferruginous sed iments are leaner grade portions of an iron
formation horizon that can be traced in outcrop and magnetically
(ODM GSC 1965 a, b) for the entire length of the Beard- more-Gerald
ton belt and westward across Lake Nipigon.
Within the map-area the iron formation is composed of thin beds of
argillite, siltstone, chert, jasper, and various amounts of
fine-grained laminated magnetite and hematite. Drag-type (possibly
penecontemporaneous) folds are present in some outcrops. An iron
formation succession up to 100 feet (30 m) thick occurs north of
Doris Lake but generally most exposures are 10 feet (3 m) thick or
less. The iron formation unit in the vicinity of Highway 801 (Photo
13) is relatively lean and is more properly termed ferruginous
argillite. A decrease in magnetic intensity, as shown on ODM-GSC
Map 7102G, for the area west of Nissiamkikam Lake coincides with
the apparent decrease in iron content of the iron formation.
Low grade hematitic iron formation float along the southwestern arm
of Beatty Lake is probably of local origin. Hematitic iron
formation similar to the occurrence further west in the central
metasedimentary belt in Irwin Township (Mackasey 1975, pi9,20) may
be present beneath Beatty Lake and the surrounding drift cov ered
area.
The thin discontinuous lenses of medium to light grey chert
intercalated with the mafic metavolcanics within the map-area are
commonly less than 3 feet (1 m) thick and usually extend no more
than 10 feet (3 m) along strike. Additional chert lenses sometimes
can be found along strike a few tens of feet away. Similarly other
parallel lenses can be found short distances across strike.
Some of these chert lenses are thin bedded but others are massive.
A reddish tinged light grey massive jasperitic chert lens located
north of Pasha Lake on the west side of Highway 801 is composed of
an equigranular microcrystalline mosaic of over 80 percent anhedral
quartz grains averaging 0.04 millimetres long by 0.02 mm wide.
Approximately 10 percent epidote and minor amounts of sericite,
apatite, and magnetite and possible feldspar were identified in
thin section. X-ray
20
rock is composed mainly of quartz and plagioclase feldspar sand
grains in almost equal proportions with 15 to 20 percent matrix.
Lithic sand-size fragments are common. Using Pettijohn's
classification (1957) these sandstones should be grouped as
feldspathic greywackes.
Iron stained carbonate, probably siderite, is a common alteration
replacement mineral. Variable amounts of chlorite and sericite are
also present. Many of the feldspar sand grains display excellent
albite twinning.
The interfingering relationship exhibited by the conglomerate,
feldspathic sand stone and greywacke in the central belt is
interpreted to be the result of depositional facies changes. That
is, the boundaries shown on the map represent primary sed- imenary
units rather than that formed by subsequent faulting and
folding.
ODM9342
Photo 13 Greywacke sandstone and siltstone with thin ferruginous
beds (dark). Highway 8 0 1 , Walters Township.
analysis indicates that both plagioclase and potash feldspar are
present. A chemical analysis (Mineral Research Branch, Ministry of
Natural Resources) of this rock is shown in Table 2.
Thin bedded grey chert from the same locality but exposed on the
east side of Highway 801 consists of cryptocrystalline quartz,
chlorite, and sericite. Bedding is marked by layers of differing
grain size along with iron rich laminations consisting of pyrite
cubes ranging from less than 0.05 mm to 0.2 mm in diameter (Photo
14). This horizon is separated into two segments having slightly
differing strike and may represent "rafted" portions of a chert
layer that has been caught up in a lava flow.
A number of interpretations of origin for these rocks have been
suggested by various observers, ranging from sedimentary chert,
tuff, to altered rhyolite flows or intrusions. The presence of
bedding and lack of chilling would appear to rule out an intrusive
or flow origin. Mafic lava along the north contact of the massive
chert bed on the west side of Highway 801 appears to be chilled and
suggests tops to the north. This agrees with direction of tops
determined from nearby pillow structures.
The mafic lavas in this outcrop area are rich in epidote relative
to similar rocks in the area and contain minor amounts of
chalcopyrite and malachite. It is possible that the chert, epidote
alteration and possibly also the copper mineralization are the
result of fumarolic activity.
In studying the chemical composition (see Table 2) of the chert
from the west side of Highway 801, a plot of the relation between S
i 0 2 and S i 0 2 / A l 2 0 3 ratio falls close to the curve
depicting the radiolarian chert trend of Cressman (1962, Fig. 2,
p.T9).
21
ODM9363
Photo 14 -Pho tomic rograph of thin bedded chert exposed in road
cut on Highway 801 north of Pasha Lake. Plane polarized
light.
This comparison could be cited as evidence that radiolaria lived
during Early Precambrian time and that the chert described herein
was formed by accumulation of their skeletal remains. However, a
review of the literature by the author found that virtually no work
has been done on the genesis of Early Precambrian cherts. More
research on cherts of all ages must be done before any meaningful
interpreta tion can be made on the origin of this particular
unit.
MAFIC INTRUSIVE ROCKS
The mafic intrusive rocks form relatively small, east trending,
lens shaped bodies in the metavolcanic and metasedimentary rocks.
As mentioned under the descrip tion of the metavolcanics, some may
be either fine-grained mafic sills or coarse grained centres of
flows.
No exposures were found illustrating the relationships between the
felsic and mafic intrusives. Therefore, the relative ages of these
two rock units are unknown. North of Paint Lake a series of mafic
lenses lie sub-parallel to the trondhjemite body contact as shown
on Map 2356 (back pocket), suggesting a possible common intrusive
history in that they may be related mafic differentiates associated
with the granitic intrusives.
On a regional scale the mafic intrusive lenses exhibit a roughly
linear distribu tion pattern extending from the southeast corner
of Leduc Township northwest
22
across the map-area and into Pifher Township (Mackasey 1971). If
this spatial dis tribution is real, the intrusion of the mafic
rocks may have been related to some deep seated fracture
system.
Metagabbro, Diorite, and Quartz Diorite
The mafic intrusive lenses north of Paint Lake are comprised mainly
of dark greyish coarse-grained, metagabbroic rock. Rough weathered
surfaces caused by resistance to weathering of the mafic minerals
are characteristic of the exposures in this area.
In thin section these rocks were found to be completely altered and
composed of approximately 30 percent ragged edged equant 2 to 4 mm
amphibole grains that appear to be pseudomorphosed after pyroxene.
They contain poikilitcally enclosed saussuritized plagioclase laths
averaging 0.3 mm in length. Plagioclase laths, which comprise up to
60 percent of the rock, are completely saussuritized and range up
to 1.0 mm in length. Albite twinning is rarely preserved. Various
subsidiary amounts of chlorite, epidote, carbonate, and leucoxene,
and minor quartz were observed.
The mafic body at Ida Lake, Walters Township, although poorly
exposed, is outlined by a southward deflection of the aeromagnetic
high associated with the mafic volcanics to the north (ODM-GSC Map
2135G). The rock is completely altered and contains a high amount
of carbonate.
Thin sections from this body were found to contain from 50 to 75
percent car bonate with lesser amounts of altered plagioclase and
chlorite. The chlorite was found to replace plagioclase laths as
well as unidentified equant grains, up to 2 mm in diameter, that
possibly were originally pyroxene.
The small metagabbro lens in the west arm of Beatty Lake may be an
eastward extension of the Ida Lake body. At Beatty Lake the rock
has a relict sub-ophitic texture containing up to 60 percent
partially saussuritized plagioclase laths approx imately 0.5 mm
long. Chloritized amphibole grains up to 1.0 mm long and car
bonate, magnetite, and up to 10 percent interstitial quartz are
also present.
The rocks in the vicinity of Oxaline Lake are dominantly dioritic
in composi tion. In outcrop they are found to be of medium-grained
salt and pepper texture. Bruce (1936, p.21-23) described these
rocks and found difficulty in distinguishing some from the adjacent
volcanics to the north.
Intrusive relationships of -the dioritic rocks with the
metasediments are illus trated in outcrops at the west end of
Oxaline Lake. Contacts north of the lake have been drawn on the
basis of grain size and absence of primary volcanic features.
A sample of diorite from Oxaline Lake was found to contain up to 70
percent plagioclase laths partially altered to sericite that
average 1.0 mm long. Pyroxene, forming interstitial grains with
minor replacement patches of chlorite, makes up the remainder of
the rock. Aproximately 2 percent leucoxene having characteristic
herringbone structure, and trace amounts of quartz are also
present.
Quartz diorite, which is the most abundant rock type in the Oxaline
Lake area, contains 10 to 15 percent interstitial quartz grains in
the order of 0.3 mm in diam eter. The plagioclase is almost
completely saussuritized. Both amphibole and py roxene are
present. Relict myrmekitic texture was observed in one thin
section. Up to 20 percent chlorite and 15 percent carbonate, along
with minor epidote, form the main alteration products.
23
ODMM64
Photo 15-Photomicrograph of lamprophyre from south shore of Paint
Lake. Note twinned amphibole phenocryst. Crossed nicols.
In southeastern Leduc Township the mafic intrusions are classed as
gabbros and are medium-grained greenish grey rocks. Intrusive
relationships are not clear and some of these rocks may be
recrystallized mafic flows. Biotite is visible in the grey wacke
sandstone near the contact with the mafic lens near the
southeastern corner of Leduc Township and suggests the latter is
intrusive.
Ragged edged pleochroic amphibole crystals in the order of 1.0 mm
long make up to 50 percent of the rock and are accompanied by
almost completely saussuritized plagioclase laths 0.3 to 0.6 mm
long. Ten to 15 percent carbonate is present along with
finergrained chlorite-quartz-amphibole bands.
Mafic Dikes
An exposure of medium greyish green hornblende porphyry was found
on a pen insula on the south side of Paint Lake. This rock
contains approximately 30 percent lath shaped pleochroic green
amphibole phenocrysts as shown in Photo 15. The groundmass is made
up of andesine laths having well preserved albite twinning with
carbonate and sericite being the main feldspar alteration minerals.
Minor amounts of magnetite, apatite, and pyroxene were also
observed. Some subangular fragments of undetermined composition and
several centimetres in diameter are present and may represent large
altered phenocrysts. This intrusion is classed as a lamprophyre.
Contacts with the host rocks were not exposed.
2 4
ODM9345
Photo 16 -Typical exposure of hybrid rocks at the contact of the
trondhjemite body in the northwestern corner of Walters Township.
The dark, fine-grained masses are meta- volcanic xenoliths.
FELSIC INTRUSIVE ROCKS
Trondhjemite
A stock of light pinkish grey, medium-grained altered trondhjemite
intrudes the metavolcanic rocks in the northwestern part of Walters
Township. This body, which is part of the southern contact zone of
the granitic intrusive in Elmhirst Township, is enclosed by a
narrow irregular band of hybrid rocks generally tens of feet
wide.
Exposures of the portion of the stock underlying Walters Township
are fairly consistent in composition. In thin section this rock was
found to be highly altered and composed dominantly of saussuritized
plagioclase. Albite twinning is preserved in some plagioclase
laths, especially on the outer rims which are oligoclase in com
position. Twenty to thirty percent quartz is present as
inclusion-rich grains in the 2 mm size range. Green pleochroic
biotite and hornblende make up 10 percent of the rock. Other
accessory minerals include magnetite, apatite, and possible xeno-
time. Crystalline epidote, sericite, and chlorite, as well as,
saussurite make up the alteration minerals.
The contact zone consists of hybrid intrusive rocks of dioritic
composition in truded as dikes and tongues into the volcanic rocks
as shown in Photo 16. Magnetite
25
Walters and Leduc Townships
Feldspar and Quartz-Feldspar Dikes
Feldspar and quartz-feldspar porphyry dikes occur throughout the
map-area. They are seldom greater than 3 feet (Ira) wide and
usually can be traced for only a few tens of feet along strike.
These dikes are generally light greyish pink, with var iable
amounts of 2 to 4 millimetre feldspar and quartz phenocrysts
enclosed in a fine-grained sericitic quartzofeldspathic groundmass.
They are considered to be genetically associated with the larger
felsic intrusions in the region.
ABSOLUTE AGE OF EARLY PRECAMBRIAN ROCKS
In the map-area the assignment of an Early Precambrian (Archean)
age to the metasedimentary, metavolcanic, and intrusive rocks other
than the diabase dikes is based upon their being pre-diabase, and
on radiometric dating.
A potassium-argon date of 2,555 million years, (Wanless 1970), was
determined on biotite from a sample of metasediment in the Gerald
ton area. Rocks in Walters and Leduc Townships are probably
equivalent to those of the sample locality and are therefore older
than 2,555 m.y., i.e. are Early Precambrian in age. No isotopic age
determinations are available for the Early Precambrian intrusives
in the map- area.
Middle to Late Precambrian
INTRUSIVE ROCKS
Diabase Dikes
North-striking, dark grey, equigranular diabase dikes from a foot
to 100 feet (0.3 to 30 m) wide and up to a mile (1.6 km) long are
abundant in the region. Be cause of spacing and north-south
orientation of most traverses, diabase dikes could easily have been
missed and are possibly more numerous than shown on Map 2356 (back
pocket). These dikes have been found to cut virtually all the rock
types in the area.
Potassium-argon determinations by Wanless (1970) shows diabase
dikes in the region, to be of at least two ages. Two specimens
analysed by the whole rock method gave ages of 1545 to 1569 million
years. Biotite from a third dike gave an age of 1125 million years.
The dikes are therefore of Middle to Late Precambrian age. The
younger dikes are probably related to the Keweenawan age diabase
intrusions in the Nipigon area that have been studied by Palmer
(1970).
26
is more abundant in the contact rocks along the southeastern margin
of the stock and is believed to be responsible for much of the
coinciding magnetic anomaly shown on ODM-GSC Map 7102G.
ODM9364
Photo 17 Photomicrograph of feldspar-quartz porphyry from north
shore of Kingston Island, Expansion Lake. Crossed nicols.
A sample collected from a 100 foot (30 m) wide dike on the south
shore of Paint Lake, Walters Township, displays a sub-diabasic
texture in thin section and is composed of approximately 60 percent
slightly altered labradorite laths that aver age 2.0 mm long. Up
to 35 percent clinopyroxene is present as interstitial material and
is slightly embayed by the plagioclase. Minor magnetite and a few
micrographic intergrowths, probably composed of quartz and
feldspar, were observed. The labra dorite in a dike near an
arsenopyrite-gold occurrence south of Nora Lake, Walters Township,
is almost completely sericitized.
A narrow porphyritic diabase dike containing feldspar phenocrysts
similar to that described in Irwin Township (Mackasey 1975, p.25
and Photo 16), was found near the west end of Blue Lake, Leduc
Township. Cylindrical jointing is present in diabase in the south
side of Highway 11 near the east boundary of Leduc Town
ship.
Feldspar-Quartz Porphyry
A zone of light pink, brittle, feldspar-quartz porphyry forming
irregular shaped, randomly spaced lenses less than one foot (30 cm)
long, occur on Kingston Island along the south shore of Expansion
Lake. The adjacent metavolcanic host rocks are brittle and appear
to have been silicified.
In thin section (Photo 17) the rock is found to contain
approximately 15 percent
27
Cenozoic
QUATERNARY
Pleistocene
Walters and Leduc Townships are covered by moderate to thin
deposits of ground moraine of silty to sandy till, outwash deposits
of sand and gravel, and in the vicinity of Jellicoe, valley train
deposits (Zoltai 1965). Glacial scouring has pro duced many smooth
outcrop surfaces. Striations having a general southwesterly trend
may be found on some of the cleaner bedrock exposures.
The most extensive glacial deposits occur in the Beatty-Pasha Lakes
region in the central part of the map-area. Here sand and fine
gravel make up much of the material in the vicinity around the
lakes. Gravel is, however, predominant in pits and embankments and
may be more abundant than noted. West-trending eskers are present
in this area and their eroded remnants form boulder beaches along
the shorelines of present lakes. Zoltai (1965) shows spillways
trending west through Hallow and Doris Lakes and west from Paint
Lake into Foxear Creek in Irwin Township. Gravel pits in the
spillway deposits at the west end of Paint Lake appear to be of
mixed glacial outwash and fluvial origin (G. J. Burwasser, ODM,
1971, personal communication). Photo 19 shows a sequence of four
units that were formed alternately in high and medium energy
depositional environments, as illustrated by the poorly sorted
coarse-grained strata displaying foreset beds.
Highway 11 follows the valley train deposits and west trending
spillway system (Zoltai 1965) along the southern part of the
map-area.
28
euhedral oligoclase phenocrysts that range from 0.15 to 4.0 mm
long. Zoning was noted in some plagioclase phenocrysts. Both
rounded and euhedral quartz crystals, some with embayments form 5
percent of the rock and vary in size from 0.3 to 3.0 mm. Other
phenocrysts noted were amphibole and green pleochroic biotite. Cal-
cite, pyrite and apatite are also present. The matrix, which forms
about 60 percent of the rock, is a cryptocrystalline
quartzofeldspathic groundmass with a sprinkling of hematite dust
clusters less than 0.01 mm in diameter.
An eight inch wide sill-like porphyry intrusion of similar
composition was found north of Paint Lake in Walters Township. Flow
structure is well developed in this occurrence as shown in Photo
18.
These rocks have been tentatively assigned a Keweenawan age on the
basis of lack of significant alteration or deformation and may
possibly by granophyric equiv alents of the diabase
intrusions.
ODAW367
ODM9368
Photo 19-Glacial outwash material in gravel pit near the west end
of Paint Lake, Walters Township.
29
GENERAL RELATIONSHIPS
The metavolcanic and metasedimentary rocks in the map-area lie
within the Early Precambrian, Superior Province of the Canadian
Shield, and occur along the boundary between two major
east-trending, lithological and structural units of the Superior
Province. These are the Wabigoon Belt (Stockwell 1970, p.45) which
is composed predominantly of metavolcanic and granitic rocks, and a
metasedimentary- granitic complex to the south termed the Quetico
Belt (or Subprovince) (Stockwell 1964). These subdivisions are
outlined in Diagram A of the Geological Map of Ontario folio (Ayres
et al. 1970).
The rocks along the north boundary of the Quetico Subprovince form
a fold belt that can be traced from the Little Long Lac area
(Geraldton, Ontario) west to Lake Nipigon. Pye (1968 b, p.32) has
shown that this belt extends to the Lac des lies area west of Lake
Nipigon.
Rocks within the Wabigoon Belt in this region have been isoclinally
folded about east-west axes. Horwood and Pye (1951) and Pye (1951)
have outlined the iso clinal style of folding in the Geraldton
area on the basis of surface and subsurface mapping and geophysical
data.
Several prominent east-trending faults have been recognized. The
Paint Lake Fault is a major structural discontinuity in the
Sturgeon River area and marks a change in lithology and in
structural trend. Formations south of the fault are tightly folded
and have a well defined east trend, whereas north of the fault the
rocks trend northeast and southwest forming a broad fold several
miles wide as shown on ODM Map 2102 (Pye et al. 1966). A late
north-northeast fault of regional scale, cuts across the eastern
part of the map-area.
RELATIONSHIP TO THE QUETICO BELT
The term Beardmore-Geraldton belt (Ayres 1969; Mackasey 1970a) has
been used in reference to the rocks within the Little Long Lac and
Sturgeon River Gold belts, and is grouped as part of the Wabigoon
belt. Based on similarities in lithology and structural trend an
intrinsic relationship appears to exist between the Quetico and
Wabigoon Belts in the Beardmore-Geraldton Area.
The Quetico Belt (or Subprovince) consists of metamorphosed
sediments, mig- matites, and massive and gneissic granitic rocks.
East trending linear structures characterize this belt in contrast
to curvilinear structures in adjacent granitic ter rain. East of
Lake Nipigon the northern limit of the belt coincides with the
northern termination of Couchiching-type metasediments (McGlynn
1970, p.66).
Mapping by Peach (1951) and Mackasey (1970 a, b, c) and compilation
work by
30
Ayres (1969) indicate that metasediments within the
Beardmore-Geraldton belt are similar to the Couchiching-type
metasediments in the Quetico Belt and probably were deposited in
the same sedimentary basin. Ayres (1969) has defined this as the
Quetico sedimentary basin and states that the metavolcanics in the
Beardmore- Geraldton belt were part of a north flanking ancient
island arc that supplied detritus for the greywacke sequence in the
basin.
Folding
MAJOR STRUCTURES
Evidence of major isoclinal folding, similar to that observed near
Geraldton is uncommon in Walters and Leduc Townships. Tight folding
has, however, been recognized west of the map-area in the vicinity
of the Leitch Mine (Ferguson 1967; Mackasey 1970 b, c).
An east-trending anticline and syncline although not shown on Map
2356 (back pocket) are thought to be present in the southern half
of the map-area. To the north, a third parallel fold, probably a
syncline is bounded to the north by the Paint Lake Fault.
Pye et al. (1966) show on Map 2102 a mafic metavolcanic unit
situated between two synclinal metasedimentary units which strike
west from Geraldton. This mafic metavolcanic unit can be traced
through the map-area in the vicinity of Hallow and Oxaline Lakes.
Within the map-area this volcanic unit is narrow and direct
evidence of folding is lacking. Pillow structures supporting the
presence of an anti cline are, however, present to the west in
Irwin and Eva Townships (Mackasey 1970b, 1975). Graded bedding,
cross bedding, and bedding-cleavage relationships within the
metasediments north and south of the metavolcanic unit, as shown on
Map 2356 (back pocket), further support an anticlinal fold
interpretation. Traced to the east, this structure forms the
Geraldton anticline as mapped by Pye (1951) in Errington
Township.
Top determinations based on graded bedding in rocks of the southern
sediment ary belt suggests that this belt is an overturned
southern limb of a syncline. The lenticular metavolcanic belt at
Jellicoe is considered by the author to be an infolded remnant of
overlying metavolcanics. The metavolcanic rocks in southeastern
Leduc Township form part of an underlying metavolcanic succession
(Peach 1951).
Rocks of the central sedimentary belt form the north limb of the
anticline near Hallow and Oxaline Lakes. These rocks apparently
underly the metavolcanics south of Paint Lake. A top determination
made on pillow lava north of Pasha Lake by Ayres (personal
communication, 1972) supports this model.
Structural evidence is lacking, but it is suggested by the author
that the mafic metavolcanic rocks south of Paint Lake form a tight
syncline overlying the conglom erates of the northern and central
sedimentary belts.
Interpretation of the fold structure south of the Paint Lake Fault
is made diffi cult by the apparent overall change in thickness and
lithology of the metasediments of the three belts. These changes,
in part, may be due to lateral fades change and/or the removal of
some of the original succession by faulting.
31
Foliation
All the metasediments and metavolcanics in the map-area exhibit an
easterly trending penetrative foliation which parallels the
regional structural units.
Cleavage is well developed in the metasediments and in some
locations cuts across bedding, as is well illustrated in the slates
and fine-grained arenites of the central and southern belts (Photo
20). Tuffaceous rocks within the volcanic units also have well
developed schistosity.
The massive flows and pillow lava units have been resistant to
deformation. However, the pillows in some flows have been stretched
out several feet parallel to foliation. Clasts in conglomerates and
pyroclastic rocks in many exposures are elon gated parallel to
schistosity.
An example of refraction of cleavage was found within the greywacke
sand stones north of the shaft near Nissiamkikam Lake (Photo 21).
Here cleavage par allels the thin fine-grained beds and then
curves upward into the coarser-grained layers.
Minor Folds
Only a few minor folds were observed in the map-area. Tight
drag-type folds a few inches across are present in some schistose
rocks in the vicinity of the Paint Lake Fault. Small scale folding
was also observed in tuffs along the Namewaminikan River near the
north boundary of Walters Township.
Folds having amplitudes in the order of one foot (30 cm) were found
in the iron formation unit along the north shore of Doris and
Nissiamkikam Lakes. These folds may, however, be due to soft
sediment slumping rather than being of secondary deformational
origin.
Lineations
The most common types of lineation observed in the map-area were
those formed by the trace of bedding along cleavage planes of the
fine-grained sediment ary rocks. Other lineations shown on Map
2356 (back pocket) are due to crenula- tions, some of which appear
to have been formed by a second phase of deformation.
Faulting
Most of the faults in the map-area have a marked topographic
expression in the form of narrow linear troughs and valleys which
can be readily detected on air photographs. Many of these troughs
and valleys separate lithologic units, and are occupied by lakes,
ponds, streams and swamps.
32
ODM9349
OOM9370
Photo 21-Refraction of cleavage in metasediments north of the shaft
on the Solomon's Pillars Mines Limited property. Bedding runs from
left to right in the photo. Cleav age curves up to 9 0 degrees to
bedding.
33
JELLICOE FAULT
The Jellicoe Fault cuts north-northeast through Leduc Township
extending from Blackwater Lake to the northeastern corner of the
Township. Within the map-area, left-handed strike-slip displacement
ranging from i/2 to 1 mile (0.8 to 1.6 km) is evident by the
displacement of formations. The variation in displacement may be
due to rotation in the plane of the fault. Bedding in the vicinity
of the fault along the south shore of Oxaline Lake is disrupted and
the western part of the mafic lens south of Jellicoe appears to
have been terminated by the fault.
This fault is believed to be part of a major break related to the
Glacier Creek Fault, as mapped by Pye (1965) some 25 miles to the
south, in the vicinity of Barbara Lake. Inspection of an air
photomosaic of the region reveals that the linear associ ated with
the Jellicoe Fault coincides with the Glacier Creek Fault linear.
In the Barbara Lake area the break is marked by a long narrow
magnetic anomaly that lies on strike with the Jellicoe Fault
(ODM-GSC 1965).
The Glacier Creek Fault has been traced southward to Nipigon Bay,
Lake Superior by Pye (1968). By including the Jellicoe Fault this
break attains a mini mum length in the order of 70 miles (110
km).
34
PAINT LAKE FAULT
This fault, or fault zone, first named the Devil's Walk-Paint Lake
Fault by Tyson (1945a), has been traced from Lake Nipigon (Mackasey
1975, p.32 to 34) through the map-area to the east boundary of
Leduc Township. Its continuation through the townships to the east
has not been studied by the author.
The fault forms a continuous lineament, including Paint Lake (Photo
22), that extends across the map-area. The rocks adjacent to this
lineament are extensively deformed. Mafic metavolcanics have been
converted to chlorite schist, and clasts in the conglomerate along
the south shore of Paint Lake are squeezed into thin elongate discs
that in some exposures have a gneissic appearance (Photo 23). Small
exposures of crenulated rocks were found in some locations in the
area of the fault notably on a small island midway along the south
shore of Paint Lake. Features such as slickensides and fault gouge
have not been found.
Evidence for at least two periods of movement, the last of which
displays an apparent right-handed strike-slip displacement of i/2
mile (0.8 km), has been found in the townships to the west
(Mackasey 1975, p.34).
The Paint Lake Fault is considered by the author to be a major
break that marks both an abrupt change in lithology and structural
trend in the map-area. South of the fault Timiskaming-type clastic
sediments are abundant, whereas to the north there are none. Mafic
amygdaloidal and pillow lavas are common south of the fault, but
intermediate to felsic tuffaceous volcanics form the predominant
rock types to the north.
The regional structure as portrayed on the Tashota-Geraldton
geological com pilation map (Pye et al. 1968a) show that the rocks
north of the fault do not follow the general east-west trend, but
swing around to the northwest to form a broad open fold several
miles in magnitude.
Photo 2 2 -A i r photograph of Paint Lake Fault lineament im the
vicinity of Paint Lake. Walters Township.
35
OOM9372
Photo 23-Deformed conglomerate on south shore of Paint Lake.
Walters Township.
OTHER FAULTS
Several other faults, mainly with east-west trends, are present in
the map-area. The linear coinciding with the Watson Lake Fault
(Mackasey 1975) continues across the southern part of Walters
Township.
Many unnamed faults coincide with prominent topographic
depressions. Some of the depressions may be related to joint
systems rather than to faulting. Some lin eaments shown on Map
2356 (back pocket) may be faults.
AGE OF FAULTS
The Paint Lake, Watson Lake and related faults cut diabase dikes
and sheets in the townships to the west (Mackasey 1975, p.34).
Their last movement is thus interpreted to be of post-Keweenawan
age. Some faults, especially the Paint Lake Fault system, were
probably active prior to Keweenawan time (p-34).
The relative age of the Jellicoe Fault is not clear, but its
apparent displacement by an east-west fault at Oxaline Lake
suggests that it is the older. Pye (1965) finds that the Glacier
Creek Fault cuts diabase in Georgia Lake area. This woidd suggest
that post-Keweenawan movement has occurred on the Jellicoe
Fault.
ECONOMIC GEOLOGY
Gold, silver, iron, copper, lead, nickel, and sand and gravel occur
within Walters and Leduc Townships. The Sturgeon River Gold mine,
2,000 feet (600 m) west of
36
Walters Township, was in production from 1937 to 1942. Sand and
gravel has been used in the construction of roads within the
map-area.
Significant amounts of gold were first discovered in the region in
1925 and this has since provided the main interest in exploration.
Iron formation in the area has been examined repeatedly since the
turn of the century. Exploration for base metals has occurred on a
sporadic basis.
The following review of mineral deposits serves as a summary.
Descriptions of individual occurrences and properties are given
under a separate heading.
Gold Deposits
Gold deposits in the map-area have two recognized modes of
occurrence; in quartz veins and stringers, and in sulphide
deposits. Within the region, for example to the west in Irwin
Township (Mackasey 1975, p.35, 36) a third mode of gold oc
currence has been recognized, viz. in zones considered by the
author to possibly be auriferous carbonate facies iron formation.
Variable amounts of silver accom pany the gold mineralization
present in the map-area.
QUARTZ VEINS
Gold-bearing quartz veins are present in every rock type in the
map-area with the exception of the Middle to Late Precambrian
diabase intrusions. Auriferous quartz veins, such as at the
Wenzoski property or the Sturgeon River Gold mine in Irwin
Township, range from thin stringers up to veins several inches
thick and follow fracture systems in the host rocks. Gold occurs
mainly in the free state, but is very finely dispersed. Gold
tellurides and electrum have been identified in the Sturgeon River
Gold mine (Bruce 1936, p.34 and 42). Many of the gold-bearing
quartz veins exhibit a ribbon structure due to the presence of
parallel sericite and chlorite coated fracture planes. A high
percentage of arsenopyrite is associated with the gold-quartz veins
at the Wenzoski property.
Conventional prospecting, by means of stripping, trenching, and
diamond drill ing, was the main method that has been used in past
gold exploration programs.
SULPHIDE MINERALIZATION
Gold is associated with pyrite-arsenopyrite veins that replace
cherty iron forma tion (Photo 24) at the Solomon's Pillars Mines
Limited property near Nissiamkikam Lake. Gold was also found to
occur with pyrite and chalcopyrite in a narrow shear zone on a
small island in Beatty Lake. Elsewhere in the region, Horwood and
Pye (1951, p.35) describe the occurrences of gold in pyrite and
arsenopyrite in lenses, tongues and irregular masses in fractured
and sheared iron formation at the Mac- Leod-Cockshutt and Hard Rock
mines.
37
OOM9373
Photo 24—Polished specimen showing replacement of bedded cherty
iron formation by pyrite and arsenopyrite. Solomon's Pil lars
Mines Limited property.
RELATIONSHIP OF GOLD DEPOSITS
TO GEOLOGICAL FEATURES
A number of general statements can be made with regard to the
relationship of gold mineralization to geological features in the
region but many questions remain to be answered, e.g. the proximity
of the Sturgeon River Gold mine to the trondh jemitic stock in
Walters Township suggests that a genetic relationship between the
gold and the stock should be considered. Laird (1936, p.41) noted
that many of the gold occurrences in the Sturgeon River area are
situated in the intermediate to fel sic tuffaceous volcanic rocks.
Elsewhere in the region some gold deposits occur in tightly folded
sedimentary rocks, in many cases, near iron formation.
Tyson (1945a) has compared the spatial relationship of gold
deposits to major faults, such as the Paint Lake Fault. He points
out that, in other gold camps, major faults have been postulated to
have served as channelways for gold-bearing hydro- thermal
solutions.
It is probable that more than one mode of origin is responsible for
the formation
38
of gold deposits. If the case for syngenetic auriferous carbonate
facies iron formation can be substantiated for the deposits in
Irwin Township to the west of the map- area, then the presence of
fossil placer gold deposits, derived locally from the erosion of
the iron formation, may have to be considered.
Sulphide Deposits
Minor amounts of pyrite, pyrrhotite, chalcopyrite, sphalerite, and
galena occur together or alone in both quartz veins and shear zones
within the map-area. Chal copyrite also occurs in altered
metavolcanics north of Pasha Lake and in carbonate filled fractures
in metavolcanics near Jellicoe. The nickel-bearing sulphide float
shown on the preliminary geological map of Walters Township
(Mackasey 1969a) is no longer considered by the author to be
authentic.
RELATIONSHIP OF MINERALIZATION
TO GEOLOGICAL FEATURES
Occurrences of sulphide mineralization have been found within
metavolcanics near the western contact of the felsic stock in
Walters Township. A minor amount of chalcopyrite was found as a
joint filling within the stock in this area.
The close spatial relationship suggests that some sulphide
mineralization may be related directly to igneous intrusive
activity. The presence of a porphyry-copper type disseminated
chalcopyrite-molybdenite deposit in a granodiorite lens in Dor
othea Township (Mackasey 1975) further indicates that sulphide
mineralization accompanied the intrusion of some granitic rocks
within the region.
Some sulphide mineralization may be related to fumerolic activity.
North of Pasha Lake, Walters Township, minor amounts of
chalcopyrite and malachite occur within a zone of epidotized mafic
lava that is accompanied by interbedded discon tinuous thin cherty
layers that are believed to be of fumerolic origin as discussed in
the section on "Iron Formation and Chert".
Some of the sulphides found in the mafic metavolcanics are very
finely dissem inated, such as north of Doris Lake, and may be
related to primary accessory min erals of the flows. In other
locations, such as with the pyrite occurrence south of Bush Lake,
the mineralization is related to shear zones in the mafic
metavolcanics.
Aside from the sulphide replacement zones in iron formation,
mineralization in metasediments is sparse. A trace of galena was
found in a trench near the south end of Highway 801 and appears to
be related to north-south fractures in grey wacke sandstone and
siltstone. The minor amount of pyrite and chalcopyrite and related
gold in standstone at Beatty Lake occurs within a narrow
east-trending shear.
The copper occurrences near Blackwater Bay in southeastern Leduc
Township are in proximity to the Jellicoe Fault and may be related
to the breccia-type sul phide deposits in the Glacier Creek Fault
of the Barbara Lake area (Pye 1965; Kustra 1969).
39
Sand and Gravel
Thick deposits of sand and gravel occur in the Pasha-Beatty Lakes
area and at the west end of Paint Lake. Some of this material has
been used in the construction of Highway 801 and service roads for
logging operations. The Ontario Department of Highways maintained
gravel reserves in the southern part of Leduc Township.
Suggestions for Mineral Exploration
The region discussed in this report is serviced by railway,
highway, hydro-electric power, natural gas, and a microwave
communications system. Any commodities of economic value thus could
be rapidly developed.
The following comments should be taken into consideration when
planning mineral exploration programs in Walters and Leduc
Townships.
BASE METALS
The intermediate to felsic metavolcanic unit located to the west of
the map-area (Mackasey 1975) contains several sulphide occurrences,
some being of the dissem inated type. This unit continues east
through the map-area and warrants attention.
40
Iron Deposits
Exploration for iron deposits in the region has been sporadic since
the early 1900s. The only recognized deposits within the map-area
belong to the narrow for mation that strikes eastward from Doris
Lake through to Oxaline Lake. This unit generally has a low overall
iron content due to the high proportion of interbedded clastic
sedimentary material and does not appear to have attracted much
explora tion activity.
Selected grab samples collected by the field party and analyzed by
the Mineral Research Branch, Ontario Division of Mines, contained
33.3 percent Fe for mag netite iron formation near the west end of
Doris Lake, and 52.2 percent Fe for a hematite-magnetite sample
from near the landing on the south shore of Oxaline Lake.
A small aeromagnetic anomaly occurs near the east end of Oxaline
Lake (ODM - GSC 1965a) and most likely represents a continuation of
the iron formation unit described above. Much of the underlying
area is swamp covered and the occurrences of iron formation shown
on ODM Map 45A were not located by the field party.
A description of the iron formation within the map-area is given in
the section of the report dealing with metasedimentary rocks.
The area of intercalated mafic flows and intermediate to felsic
tuffaceous rocks near Expansion Lake may be favourable for
volcanogenic deposits associated with change in volcanic
activity.
The cherty horizons and related sulphide mineralization within the
adjacent mafic metavolcanic rocks may be of fumerolic origin. Rocks
of this type have been located north of Pasha and Oxaline Lakes.
Detailed mapping may show that these form well defined interflow
horizons. Further studies of these deposits should be undertaken in
an attempt to discover if an exploration model exists.
Some of the sulphide showings within the region, such as the
disseminated copper-molybdenite deposit in Dorothe