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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
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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
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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.
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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.
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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.
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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.
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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.
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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).
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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
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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.
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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).
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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.
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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