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ONTARIO DEPARTMENT OF MINES AND NORTHERN AFFAIRS

A REVIEW OF RECENTLY ACQUIRED GEOLOGICAL DATA, BLIND RIVER-ELLIOT LAKE AREA

By

James A. Robertson

A paper to be presented at the Geological Association of Canada 1971 Annual Meeting at Laurentian University, Sudbury, Ontario, May 1971.

MISCELLANEOUS PAPER 45

May, 1971 This book may not be reproduced, in whole or in part, without the permission of the Ontario Department of Mines and Northern Affairs.

Publications of the Ontario Department of Mines and Northern Affairs and price list

are obtainable through the

Publications Office, Ontario Department of Mines and Northern Affairs, Parliament Buildings, Toronto, Ontario.

Orders for publications should be accompanied by cheque, or money order, payable to Treasurer of Ontario. Stamps are not acceptable. CONTENTS page

Abstract ...... iv Introduction ...... l Recently Completed or Current ODMNA Mapping Programs ...... 2 Flack Lake-Rawhide Lake Area ...... 3 Archean ...... 3 Proterozoic ...... 5 Huronian ...... 5 Stratigraphy ...... 5 Structure ...... 9 Post-Huronian ...... 10 Cutler-Massey Area ...... 11 McMahon-Morin Townships ...... 12 Other Provincial, or Federal, or Joint Activities ...... 13 Exploration ...... 15 Miscellaneous Studies ...... 17 Coneluding Remarks ...... 19 Acknowledgments ...... 19 Selected References ...... 20

TABLES 1. Table of Formations for the Blind River-Elliot Lake Area ...... 4 2. Summary of Huronian Stratigraphy in the Blind River-Elliot Lake Area ...... 7

FIGURES 1. Location of Blind River-Elliot Lake area ...... vi 2. Key to recent geological maps, North Shore of Lake Huron ...... 30 3. Generalized geological map of the Blind River-Elliot Lake area ..... 31 4. Location of recent drill holes, Elliot Lake area ...... 32 5. Geology of the Flack Lake-Rawhide Lake area ...... 33 6. Lateral variation of the Huronian Supergroup, Elliot Lake area ..... 34 7. Schematic cross-section of Elliot Lake area, units keyed to Table of Formations ...... 35

- 111 - ABSTRACT Recent work in the Blind River-Elliot Lake area falls into the following categories: 1) recently completed or current Ontario Department of Mines and Northern Affairs mapping programs; 2) other Provincial, Federal, or joint activities; 3) the work undertaken by exploration or mining companies; and 4) other studies. Recent mapping has been primarily in the Flack Lake area, the Massey area, and to the north of Bruce Mines. Studies in these areas include detailed mapping of the Lorrain, Gordon Lake, and Bar River Formations, the distribution of thorium and aluminous minerals in the Lorrain Formation, the possibility of organic remains in these units, and the structural and economic geology of the Massey and Flack Lake areas. Structure in the Flack Lake area is more complex than previously recognized. The mapping north of Bruce Mines has led to the delineation of several Huronian stratigraphic units not previously recognized within the map-area and to a better understanding of the strati graphic correlation and history of the area. Huronian volcanic rocks have been mapped at several localities and also have been recognized in drill core. These volcanic rocks may have implications in the exploration for uranium and copper. Some volcanic rocks, previously mapped as Archean, are now regarded as Huronian. Stratigraphic reference sections have been measured in the Elliot Lake area and field notes are filed with Ontario Department of Mines and Northern Affairs. Considerable amounts of core, either as selected samples or, for a few areas, complete cores, have been stored and under certain conditions this material is available for study. Revised compilation maps based on corrected or new data, and using the nomenclature of the Federal-Provincial Committee on Huronian Stratigraphy, have been prepared. Another study of interest has been an attempt to relate tectonic features observable at surface to in situ stresses in the mine workings. Recent intensive exploration has resulted in little addition to published ore reserves but much stratigraphic and structural data has been released. Roscoe©s subdivision of the Matinenda Formation into three (possibly four) sedimentary units in the Quirke Syncline is valid and the distribution of these and of volcanic rocks is better known. Refinement of nomenclature for the ©Elliot Lake Group 1 may be required. Various geophysical approaches to U-Th exploration are discussed briefly. Academic research has been concentrated on those rocks of possible glacial origin; published papers largely support that origin. These studies have included geochemistry, sedimentation, and fabric analyses, though the latter have been challenged because of the tectonic environment. Other studies have emphasized the aluminous minerals in certain members of the Lorrain Formation and the broader implications of correlations in the Lake Superior-Lake Huron region. Although much new or improved data has become available, much remains to be done. The Huronian volcanic rocks are worthy of detailed study both

- iv - from the economic and the academic standpoints and several Huronian forma tions are of prime theoretical interest, e.g., the Espanola and Gordon Lake Formations. The number of persons who have visited the Elliot Lake area and made use of the excellent, readily accessible, exposures for teaching and(or) research projects has been growing steadily. As long as this does not result in deterioration of the outcrops this is to be encouraged. A reference list including mainly recent papers and abstracts is provided.

- v - Figure l - Location of Blind River- Elliot Lake area

- VI - A REVIEW OF RECENTLY ACQUIRED

GEOLOGICAL DATA, BLIND RIVER-ELLIOT LAKE AREA1

By James A. Robertson^

INTRODUCTION

This paper reviews the geological and geophysical data from the Elliot Lake area (Figure l, location map) mainly obtained or published since 1969. A list of references is provided. In 1968 and 1969 a number of reports and review papers were published (Robertson 1968, 1969a; Roscoe 1969; Robertson, Frarey, and Card 1969; Robertson, Card, and Frarey 1969). Robertson (1968) described the geology of Townships 149 and 150, the heart of the Elliot Lake camp. Roscoe (1969) described the regional geology and the results of field studies, undertaken by the Geological Survey of Canada in 1954-1958, and subsequent laboratory studies. Robertson (1969a) reviewed the knowledge and the then current activities in the Elliot Lake area as part of a CIM Symposium on uranium geology and exploration. Robertson et^ aU (Robertson, Card, and Frarey 1968; 1969; Robertson, Frarey, and Card 1969) reviewed the history of Huronian stratigraphic nomenclature, and using data from the Elliot Lake area and environs recommended a revised stratigraphic nomenclature (Table 1) that is now used by the Geological Survey of Canada, the Ontario Department of Mines and Northern Affairs, and by many exploration geologists. The 1969 CIM Symposium was held because of the resurgence in exploration for uranium. This exploration was at its peak in 1968 and 1969 but declined in late 1969 and 1970 (Williams 1970) due to: (1) tight money; (2) a lack of major new discoveries; (3) political uncertainties about foreign investment in the uranium industries and the opening of the United States market to Canadian producers; and (4) the slowing down of nuclear power station construction and consequent lack of firm contracts for uranium. In the Elliot Lake camp this exploration included surface mapping and geophysical surveys but largely took the form of large-scale drilling programs with many holes reaching depths of between 3,000 and 4,000 feet (and several between 5,000 and 6,000 feet) in areas not previously explored (see Figure 4). Some drilling took place on the fringes of known orebodies and should be classed as development drilling.

Released by permission of the Chief Geologist, Ontario Department of Mines and Northern Affairs. 2 Geologist, Ontario Department of Mines and Northern Affairs, Toronto. - 2 -

The exploration drilling was concentrated in the following areas (see Figure 4): the Quirke Syncline including the previously undrilled western part; around the nose of the Chiblow Anticline and the Parkinson Dome; in the Huronian rocks north of the Flack Lake Fault and in the North Channel of Lake Huron from Bruce Mines eastwards to the mouth of the Spanish River. Deep drilling was sparsely scattered west of the Little White River to the vicinity of Haughton Township (west of report area). Farther west, exploration was concentrated in a northwesterly trending zone marking the outcrop of the Thessalon and Duncan Volcanics and the underlying Livingstone Creek Formation (Frarey 1967; Roscoe 1969), which is probably equivalent to part of the Matinenda Formation. This activity resulted in a wealth of stratigraphic and structural data, a considerable part of which has been filed for assessment credit or otherwise made public. Of particular interest has been the geological data obtained from the North Channel of Lake Huron where the only previous data was from sparsely scattered islands. During these years, 1968-1969, the Ontario Department of Mines and Northern Affairs continued its mapping programs. Robertson and others (1969c; Robertson and Johnson 1969; Robertson 1970c; Robertson and Johnson 1970) mapped the Flack Lake-Mount Lake area adjacent to the area mapped by Wood (1968 et seq.) and in 1970, Chandler (1970a,b,c) mapped McMahon and Morin Townships. The results from earlier mapping in the vicinity of Pronto Mine (Robertson 1970a) and between Spragge and Massey were made available to the public, the latter as Open File Reports in the Toronto, Sudbury, and Sault Ste. Marie offices (Robertson 1969b; 1970b). Both industry and the universities are reminded that much geological data is available in these Open File Reports and that information on Departmental activities is published each year in a ©Summary of Field Work 1 . The present paper consists of 5 sections: 1. Recently completed or current Ontario Department of Mines and Northern Affairs mapping programs; 2. Other provincial, or federal, or joint activities; 3. Exploration; 4. Miscellaneous studies; and 5. A list of references and(or) recent publications of interest. It should be noted that there is much overlap in work and interest between the different agencies or individuals. However, there has been a satisfactory level of co-operation and exchange of information and ideas.

1. RECENTLY COMPLETED OR CURRENT ODMNA MAPPING PROGRAMS Within the area under discussion there are four such programs: 1) the studies of Wood in the Rawhide Lake area (Wood 1968 et seq.); 2) the studies of Robertson in the Flack Lake area (Robertson 1969c; Robertson and Johnson - 3 -

1969; Robertson 1970c; Robertson and Johnson 1970); 3) the studies of the Pronto-Spragge-Cutler-Massey areas (Robertson 1970a; 1969b; 1970b); and 4) Chandler©s work in McMahon and Morin Townships (Chandler 1970a,b,c). Programs l and 2 are discussed as one area in this report.

FLACK LAKE-RAWHIDE LAKE AREA This area (Figure 5) lies to the north of the area mapped by Collins (1925), but reconnaissance surveys were carried out by Emmens (1927) and Harding (1939). Subsequently the area was visited by Roscoe (1957; Roscoe and Steacy 1958; Roscoe 1969). Roscoe©s data (most of which was available before publication) and miscellaneous data accumulated from the first uranium exploration boom, were incorporated in the Sault Ste. Marie-Elliot Lake Compilation Map (Giblin and Leahy 1967). The area is crossed by the Flack Lake Fault system (see Figures 3 and 5) and the rocks fit into 4 classes: 1) the Archean basement; 2) the Huronian sedimentary (including minor volcanic) rocks; 3) the post-Huronian mafic intrusive rocks; and 4) the Pleistocene and Recent unconsolidated sediments. (Units 3 and 4 are not shown on Figure 3 and Unit 4 is not shown on Figure 5).

Archean The Archean rocks consist of granitic rocks enclosing blocks of schists and gneisses; originally greywackes and chloritic, biotitic, and amphibolitic mafic rocks representing mafic igneous, pyroclastic, and volcanic rocks. These ancient rocks have been folded about northwest-trending axes and a northwest trend characterizes both bedding and foliation. A larger body of volcanic and sedimentary rocks, including sulphide-bearing iron formation, is exposed in the country between Ten Mile Lake and the Flack Lake Fault (see Figure 3). In this area, particularly close to the Flack Lake Fault, an east strike is developed and pillow lavas provide structure markers. The granitic rocks are variable and fit into two broad groupings: (a) granodiorite, quartz monzonite, granite, grey-pink to red in colour, massive equigranular, porphyritic, or gneissic in texture, generally sodic, non- radioactive and with abundant remnants of the earlier rocks; and (b) massive equigranular porphyritic, red, slightly radioactive quartz monzonite without included material (further subdivision has been made by Wood 1968 et seq.). Granites of the first grouping outcrop to the north of Mount Lake (Robertson 1970c; Robertson and Johnson 1970) and Rawhide Lake (Wood 1968 et seq.). Granites of the second type occur to the north of Ten Mile Lake~TRobertson 1969c) and are part of the body previously mapped north and northwest of Quirke Lake (Robertson 1963; 1961; 1968). These granitic rocks were further examined by Bottrill (1971) in conjunction with gamma-ray spectrometry research, The latter revealed U-, Th-, and K-contents of 0.6 ppm, 4.1 ppm, and 1.9 percent; these results are little different from the normal content of granitic rocks. The Archean basement rocks are cut by numerous northwest-trending diabase dikes. These are fine-grained and as only rarely do diabase dikes - 4 -

Table l TABLE OF FORMATIONS FOR THE BLIND RIVER-ELLIOT LAKE AREA AGE UNIT CODE DOMINANT (Million LITHOLOGY Years) PHANEROZOIC CENOZOIC PLEISTOCENE AND RECENT Sand, gravel, till Unconformity PALEOZOIC ORDOVICIAN (20) Limestone PRECAMBRIAN PROTEROZOIC KEWEENAWAN SUPERGROUP SUDBURY DIKES (19) Olivine diabase 1,225 Intrusive Contact MOUNT LAKE DIKE Quartz diabase Intrusive Contact with Nipissing Diabase * HUDSONIAN CROKER ISLAND COMPLEX (18) Gabbro, granite 1,445 CUTLER BATHOLITH (18) Granite 1,750 Intrusive Contact PENOKEAN NIPISSING (17) Quartz diabase, diorite 2,155 Intrusive Contact HURONIAN SUPERGROUP COBALT GROUP BAR RIVER (16) Quartzite GORDON LAKE (15) Siltstone, sandstone LORRAIN (14) Quartzite, conglomerate, arkose GOWGANDA (13) Conglomerate, greywacke, quartzite Unconformity-Disconformity QUIRKE LAKE GROUP SERPENT (12) Quartzite ESPANOLA (11) Limestone, greywacke BRUCE (11) Conglomerate Local Disconformity HOUGH LAKE GROUP MISSISSAGI (10) Quartzite PECORS (9) Argillite RAMSAY LAKE (8) Conglomerate Local Disconformity ELLIOT LAKE GROUP** McKIM (7) Argillite MATINENDA (5) Quartzite, l U-conglomerate Conglomerate Arkose U-conglomerate Unconformity regolith ARCHEAN LATE ARCHEAN INTRUSIVES Diabase 2,500 Intrusive Contact KENORAN (ALGOMAN) [31Granite 2,500* Intrusive Contact EARLY ARCHEAN INTRUSIVES Gabbro Intrusive Contact KEEWATIN (1) Volcanic and sedimentary rocks * Mount Lake Dike may be 1,795 m.y. ** Volcanic rocks are found locally in the Elliot Lake Group (6), each occurrence has been given its own name. Note: Geological ages given are from a variety of sources. - 5 -

cross the Archean-Huronian contact demonstrating a post-Huronian age, it is assumed that many, perhaps the majority, are Late Archean in age (Robertson 1970c; Robertson and Johnson 1970; Wood 1970b).

Proterozoic

Huronian

Stratigraphy: Huronian sedimentary rocks rest unconformably on the Archean basement. Those rocks exposed south of the Flack Lake Fault system are the westward part of the Quirke Syncline (Robertson 1969a,b; 1963). All units from the Matinenda(?) Formation to the lower Lorrain Formation are exposed. Surface mapping and drilling (Robertson 1969c; Robertson and Johnson 1969; ODMNA assessment work files) has revealed the presence of mafic volcanic rocks (Figure 5) at the base of the Huronian sequence in Townships 157 and 163; the writer has named these rocks the Dollyberry Lake Volcanics. The rocks are basaltic in composition, black when fresh, and are generally unmetamorphosed, and may be amygdaloidal or porphyritic or both. In some flows glomeroporphyritic aggregates of plagioclase crystals are characteristic. Interflow material or fine-grained flow tops are commonly sheared, but in some places bedded material, including conglomerate with granite cobbles, can be identified. Chalcopyrite mineralization, either disseminated or as amygdule fillings, is characteristic of these flows. At Dollyberry Lake a few feet of breccia, comprising angular quartz fragments up to 1-1/2 inches across in a grey slightly pyritic quartzose matrix with trace radioactivity (up to 2 times background), lies between the volcanic rocks and a regolith developed over granite. In the Crazy Lake area of central Township 163 (Figure 3) lying below the volcanic rocks are several hundred feet of sub-greywacke and minor polymictic conglomerate with some weakly radioactive quartz-pebble conglomerate with a pyritic chloritic matrix (Matinenda Formation equivalent). The identification of these volcanics and the discovery of volcanic rocks in drill cores at a number of localities in the Quirke Syncline (Figure 3) and identification of volcanic rocks in the Cutler and Massey areas (Robertson 1969b; 1970b; Bottrill 1970; 1971) led Robertson and Bottrill to re-examine a number of surface localities previously mapped as Keewatin volcanics. Figure 3 shows those localities within the Blind River-Elliot Lake area in which Huronian volcanic rocks have been identified at surface. In addition several volcanic units are shown on the cross-section (Figure 7). The volcanic rocks recognized at Crazy Lake, Dollyberry Lake, Ten Mile Lake, and eastwards to the vicinity of the Quirke Mine are the same unit, i.e., the Dollyberry Lake Volcanics of Robertson (1969c). In the Kyle Lake-Quirke Lake area, Bottrill (1971) has recognized, in a few places, felsic units that may be massive or brecciated and in the field are characterized by a light grey-weathering colour, pink body colour, and by a distinct K content of 6.6 percent as recorded on a gamma-ray spectrometer (T. Bottrill 1970, personal communication). - 6 -

The recognition of the extent of predominantly mafic volcanic rocks within the Lower Huronian sequence has been one of the major advances in recent years. Of considerable note is the close relationship of these volcanic rocks to known uranium-bearing strata and oligomictic conglomerate occurrences of the Matinenda Formation. There are slightly radioactive conglomerate occurrences in the Duncan and Thessalon volcanic assemblages, in Morin Township, in the Dollyberry Lake area (see above), in May Township near Massey, and at Agnew Lake where there is a possible association of ore-grade conglomerates and volcanic rocks (Giblin and Leahy 1967; Robertson 1971c; ODMNA assessment work files). At Agnew Lake where regional meta morphism is of higher grade than in the Elliot Lake camp there is a problem in distinguishing metavolcanics from Nipissing metadiabase. F.Q. Barnes (of G.S. Robertson and Associates, Blind River, 1970, personal communication) has recently remapped the Agnew Lake area and has indicated that much, but not all, of the rock previously regarded as volcanic rocks is in reality Nipissing metadiabase. Volcanic rocks in the Ten Mile Lake and Quirke Lake areas may have controlled either chemically or physically the deposition of the ore of the Quirke ore zone and the area between the Nordic and Pecors uraniferous zones is also underlain by a wedge of volcanic rocks (Robertson 1961; 1962, chart) previously mapped as Keewatin(?) but now believed to be Huronian (see Figure 7, cross-section unit 6), The association of mafic volcanic rocks and uraniferous strata has implications concerning the depositional environment of the conglomerate beds and possibly concerning the concentration of uranium within the beds (see also Bottrill 1970; 1971). The lava-flows thus not only contain copper mineralization but also may have a relationship to uranium deposits; a further study is warranted on these grounds. Study also is warranted on academic grounds, because these rocks bridge the gap between the Archean and the younger Proterozoic volcanic assemblages. It is to be hoped that chemical- trend, trace-element-distribution, age-determination, and detailed petrographic studies will be forthcoming. The Ramsay Lake and Pecors Formations are normal in their lithology but are thin: together they occupy less than 100 feet at outcrop. The Mississagi Formation in Townships 157 and 163 is similar to that at Quirke Lake and is characterized by high feldspar and sericite content resulting in a green colour, low to moderate radioactivity, channel crossbedding and graded bedding. Bottrill (1971) has recorded U, Th, and K contents of the Mississagi Formation in the Little White River area as 11.5 ppm, 54.7 ppm, and 4.2 percent respectively. The Espanola and Serpent Formations are poorly exposed and little new information was obtained. None of these formations (i.e. Matinenda to Serpent inclusive) are exposed north of the Flack Lake Fault system. The region of northwards overlap of these units has been faulted out and(or) removed by erosion. In the Dunlop Lake-Lillybet Lake area the Gowganda Formation contains an assemblage of conglomerate, greywacke, quartzite, and siltstone approximately 2,000 feet thick (Robertson 1963; 1969c; Robertson and Johnson 1969). The Gowganda Formation is traditionally believed to have accumulated in a glacial, or at least a cold environment, and this view has been supported- by many recent workers (e.g. Casshyap 1968; 1969; Lindsey 1966; 1969; Ovenshine 1965; 1970; Robertson 1961 et seq; Roscoe 1969; Young 1969b; 1970a; Young and -7-

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Chandler 1968). At Lillybet and Mace Lakes as at Dunlop Lake (Robertson 1963) the uppermost bed is a slightly magnetic laminated siltstone, the outcrop of which correlates with an anomaly on airborne magnetic maps (ODM 1954; 1955; ODM-GSC 1963; 1964). Rocks of the Gowganda Formation are also exposed in fault blocks adjacent to but south of the Flack Lake Fault (Robertson 1969b,c; Eisbacher and Bielenstein 1969) in an area previously believed to contain only Archean rocks (Emmons 1927; Harding 1939; Giblin and Leahy 1967). North of the Flack Lake Fault the thickness of the Gowganda Formation varies with the basement topography from O to 500 feet or more. Drill core data show the formation thickens southwards. The conglomerate beds were laid down in elongate basins controlled by the basement topography. Flash floods passing into turbidity currents were the probable transport mechanism. Away from the basement contact area the presence of greywacke with rafted pebbles and cobbles indicates glacial or near glacial conditions. The lack of a preserved regolith at the Archean surface (Robertson 1970c; Wood 1970a) may indicate oxidizing rather than the reducing conditions that prevailed during the deposition of the Lower Huronian sediments elsewhere in the district (Robertson 1969a; Roscoe 1969; Wood 1970a), or it may indicate that regolithic material was completely eroded prior to deposition of the Gowganda Formation. The contact between the Gowganda Formation and the overlying Lorrain Formation is believed to be conformable. Several units have been mapped within the Lorrain Formation in the following ascending stratigraphic order: 1) pink ferruginous quartzite and minor siltstone; 2) coarse-grained green arkose; 3) pink coarse hematitic arkose with radioactive (thorium:uranium 10:1) quartz-pebble conglomerates (Robertson 1970c; Robertson and Johnson 1970); 4) interbedded pink and buff quartzite and in a few places, greenish quartzite (quartz-chert-jasper pebble bands are characteristic of the upper part of this member); 5) massive white quartzite, with quartz-chert-jasper pebble bands in the lower part. Sericite, kaolinite, pyrophyllite, and diaspore are found in the non-feldspathic beds in members 4 and 5 (Chandler et al. 1969) and indicate the onset of warm rather than frigid conditions (Wood 1970a; Young 1970b). Only members l and 2 are found in the Lillybet-Mace Lakes area (southwest corner of Township 163). Crossbedding is common in the Lorrain Formation in the Flack Lake-Mount Lake- Rawhide Lake area but is variable; southwesterly currents have been interpreted by Hadley (1969) and by the writer (field notes) although the source area was probably to the north. North of Bruce Mines, Hadley (1969) deduced south easterly current directions. These five members can be traced throughout the Flack Lake-Mount Lake-Rawhide Lake area. Their equivalents can also be recognized and traced in the La Cloche Lake-Whitefish Falls area (Card 1971b,c; Chandler 1969) but the individual units are both finer grained and thicker indicating deposition farther from source. They have been strongly folded and foliated and somewhat metamorphosed; the clay minerals are represented by kyanite and andalusite (Church 1967; Chandler 1969; Robertson 1970b). Figure 6 shows the regional variation in thickness of the Huronian Formations. The Lorrain Formation is overlain, apparently conformably, by the Gordon Lake Formation, a 1,000-foot sequence of well-bedded siltstone, argillite, - 9 -

chertstone, and fine- to medium-grained sandstone. Drill hole data (Eisbacher and Bielenstein 1969; Bottrill 1970; Robertson 1969c; 1970c) indicate that there are three members: 1) a lower member comprising reddish sandstone and siltstone with anhydrite and gypsum nodules (and salt casts?); 2) a middle member of dark green siltstone, argillite, and minor sandstone; and 3) an upper member of reddish siltstone, argillite, and chert. The middle member tends to form a scarp in the Flack Lake area that corresponds to a moderate magnetic anomaly (see Keevil Mining Group Limited, drawing No. 3798, JLn^ODMNA assessment work files). Current ripples, micro- crossbedding, slumpage structures, and dessication cracks indicate deposition in very shallow water (Young 1969; Robertson 1969c; Robertson and Johnson 1969; Robertson 1970c; Robertson and Johnson 1970; Wood 1970a,b). The Gordon Lake Formation is overlain by the Bar River Formation, which comprises at least 1,200 to 1,500 feet of massive to well-bedded ortho quartzite, generally crossbedded and ripple marked (Robertson 1969c; Robertson and Johnson 1969; Woodward 1970; Eisbacher and Bielenstein 1969). Mudcracks and dessication features are also found particularly in finer grained sand stones and intercalated siltstone bands. One unit is characterized by thin bedding and ferruginous siltstone and quartzite. The iron has been partly redistributed and small-scale solution depositional fronts adjacent to joints and fractures are common. Some ripple-marked surfaces at this horizon are covered with segmented, tapering, sinuous structures of possible organic origin (Hoffman 1967; Young 1967; Donaldson 1967). Young (1967) and Hoffman (1967) favoured metazoans (worms) as the organism involved but Donaldson (1967) suggested that the structure represents the infilling of dessication cracks in algal mats. In the same area there are many rather similar structures that are undoubtedly dessication features. The dessication features of the Gordon Lake Formation (Young 1969a; Robertson 1969c) are so similar to the most organic-looking structures of the Bar River Formation that the organic nature of the latter remains in doubt. Wood (1970a,b) has recorded oolites in the ferruginous rocks and their presence along with the many primary structures indicates deposition in very shallow water. In the ferruginous rocks Bottrill (1970, personal communication) has observed pyrite and in polished section has identified the major iron mineral as maghemite rather than hematite. The conditions of deposition, sedimentation, climate, and state of atmospheric oxidation represented by the upper Huronian rocks of the Flack Lake area are to be discussed in more detail in another paper being given by Wood (1971) at the Huronian Symposium, at the 1971 Annual Meeting of the Geological Association of Canada, Sudbury.

Structure: In addition to allowing more detailed analysis of stratigraphy and the nature and relationship of radioactive mineralization the recent work has given much previously unsuspected structural data. The Flack Lake Fault first shown by Roscoe (1957) as an arcuate fault is a system of faults (Robertson 1969a,b,c; 1970a,b,c; Robertson and Johnson 1969; 1970; Wood 1968a,b; 1969a,b), the net effect of which has been to achieve north-south shortening, possibly of several miles, and to drop the rocks to the north by at least 4,000, possibly 5,000 feet. The rocks to the north are not a monocline nor have they been shown to be a basin. In the - 10 -

vicinity of Mount Lake they dip south but are interrupted and repeated by reverse or thrust faults. These faults have resulted in the radioactive member of the Lorrain Formation outcropping three times (Robertson 1970c; Robertson and Johnson 1970). Previously these outcrops were regarded as different units (Roscoe 1969). Bedding plane lineations, tension fracture fillings, and joint patterns have been observed by Robertson (Robertson and Johnson 1969; 1970; Robertson 1970c) and studied in more detail by Eisbacher and Bielenstein (1970; Eisbacher 1969). In the vicinity of Flack Lake the strata become gently folded about axes parallel to the Flack Lake Fault system. The intensity of the folding increases southwards, i.e., the amplitude increases and the wavelength decreases. The fold closest to the fault system is a syncline with the south limb overturned, and locally the Gordon Lake Formation is exposed at the surface and lies structurally above the basal Bar River Formation (Robertson 1969c). On Highway 546, the Bruce Limestone Member of the Espanola Formation is exposed adjacent to the Flack Lake Fault and the outcrops show an intriguing pattern of fracture of competent silt bands and flowage of incompetent carbonate bands (Robertson and Johnson 1969).

Post-Huronian The post-Huronian structural and intrusive events in this area are as follows: 1) tilting and faulting; 2) intrusion of the Nipissing Diabase, including the Rawhide Lake-Mount Lake body; 3) further faulting and intrusion of diabase dikes with northwest trend; 4) thrust faulting; 5) intrusion of northeast-striking, strongly differentiated, diabase dikes; and 6) the intrusion of northwest-striking olivine diabase dikes of the Sudbury Swarm. It should be noted that in the eastern Superior Province there are two sets of northeast-trending differentiated quartz diabase dikes; an earlier set, north and northwest of Sudbury, cut by the northwest-trending Onaping faults and the Sudbury dikes and a later set not cut by the northwest faults and which cut the Sudbury dikes (Douglas 1971, Figure IV-30, and p.131-134). The younger set is the Abitibi Swarm of Keweenawan age; the older set, which includes dikes at Mount and Kirkpatrick Lakes (Robertson 1971c), is not dated with certainty and may be related to either the Nipissing Diabase or possibly a 1,750 million-year event. Earlier interpretation (Wood 1968a; Robertson 1970c; Robertson and Johnson 1970) had placed the Mount Lake dike in the Abitibi Swarm. The Rawhide Lake-Mount Lake body (Figure 5) is a thick south-dipping sheet of ©diabase© differentiated from diorite to granophyre and with sharply chilled margins. Southwest of Mount Lake it passes into a near-vertical dike trending southwest to Cobre Lake where it turns sharply southeast and strikes east-southeast to a point some 2 miles east of Cobre Lake where it again becomes a south-dipping differentiated sheet forming the high ground to the north of the Boland River (Robertson 1970c). This body has been dated (Rb-Sr whole rock) at 2,130 t 215 million years (Van Schmus 1965; Hoffman 1967). Granophyric segregations south of Rawhide Lake (Township U, see Wood 1968a), at the eastern end of the dike section east of Cobre Lake, and possibly in the sheet along the Boland River, are characterized by epidote, - 11 -

chalcopyrite, and pitchblende. Quartz-carbonate-specularite-sulphide veins occur at and near Cobre Lake (Robertson 1970c). These lie between the dike and sill parts of the intrusive body and probably were deposited from mineral-charged fluids migrating outward from the cooling magma. Quartzites adjacent to the diabase body are albitized and have a red coloration, and the more argillaceous rocks show spotted aggregates of chlorite and mica with or without carbonate and sulphide minerals. On the north shore of Vasseau Lake such spotting with carbonate and chalcopyrite is well-developed.

At Stag Lake in Township 151 (Wood 1969a) exploration diamond drilling revealed the presence of chalcopyrite disseminated in Lorrain quartzite. It has been suggested that this occurrence and other low-grade occurrences of disseminated chalcopyrite elsewhere in the uppermost Huronian formations are syngenetic deposits (Sutherland 1970, Bottrill 1970, personal communications; R. Kirkham 1971). At Stag Lake the chalcopyrite is not distributed uniformly but is concentrated in dark spots resembling those seen at Vasseau Lake and as there is a large body of Nipissing Diabase in Township 151, just west of the occurrence, the syngenetic origin is not the only possibility; either magmatic or reworked syngenetic origins have also to be considered. The writer is not aware of any special research, such as isotope analyses, carried out to clarify the genesis of copper occurrences within the Cobalt Group. The routine mapping of Nipissing Diabase in the Flack Lake-Elliot Lake areas has revealed much the same petrographic features as described by Card et^ a^. (1970) for the Maple Mountain area. Card et al. noted regional variations in petrology, metamorphism, and mineralization. Card and Pattison (1971) will discuss the Nipissing Diabase further in another paper being given at the Huronian Symposium at the 1971 Annual Meeting of the Geological Association of Canada, Sudbury. Thus recent studies have emphasized mapping, stratigraphy, economic geology, and structure. Petrographic, chemical, mineralogic, and sedimenta tion studies on the rocks north of the Flack Lake Fault system are continuing There is scope for thesis studies and other research projects.

CUTLER-MASSEY AREA There has been little new work in the Massey area in the last 2 years but data referred to in previous review papers has become more generally available. Thus ODM maps and Open File Reports for Cutler (No. 5026) and Massey (No. 5043) areas (Robertson 1969b; 1970b), have been released and Chandler©s study of Harrow Township (Chandler 1969) is on file at the University of Western Ontario. The significance of the Massey-Cutler area for regional correlation was discussed by the author (Robertson 1969b; 1970b) and the mapping is the basis for the conclusions reached by the Federal- Provincial Committee on Huronian Stratigraphy (Robertson, Card, and Frarey 1968; 1969; Robertson, Frarey, and Card 1969). Studies in the vicinity of the Cutler Batholith (Robertson 1969b; 1970a,b; Cannon 1970) have clearly - 12 -

indicated two post-Archean orogenic cycles, the Penokean with a peak at about 2,100 million years and the Hudsonian with a peak at about 1,750 million years (see also Church 1968; Fairbairn et^ a^. 1969) and confirmed the post- Huronian (Hudsonian) age of the granite.

The Cutler Granite is late tectonic. It possibly was formed by trans formation of the metasedimentary rocks at depth, but is intrusive at the level now displayed.

Chandler (1969), Chandler et^ al^. (1969), Church (1967), and Young (1970b) have paid considerable attention to the presence, significance, and metamor phism of aluminous minerals in the Lorrain Formation. These are represented by kyanite (and locally andalusite), partly retrograded to kaolinite.

In the narrow belt of Huronian rocks present north of the Murray Fault, the author (Robertson 1970b) has identified mafic volcanic rocks resting on granitic basement and interbedded with Matinenda-type sedimentary rocks, including minor amounts of radioactive oligomictic conglomerate. At least some of the copper showings in the vicinity of Massey are closely related to these volcanic rocks, which the writer (Robertson 1970b) has termed the Salmay Lake Volcanics. The Salmay Lake Volcanics are probably continuous with the Baldwin Volcanics of the Agnew Lake area (see for example Carrington and Wilton 1969) and mafic volcanic rocks to the south of the Sudbury Irruptive.

Mapping of the gap between Massey and Espanola is underway and should be completed in 1972.

McMAHON-MORIN TOWNSHIPS

The fourth area in which the Ontario Department of Mines and Northern Affairs is currently mapping lies 25 miles north of Bruce Mines (Chandler 1970a,b,c). Chandler has mapped McMahon and Morin Townships and mapping is being continued eastwards, along the northern boundary of the Huronian, to eventually link the mapping by Frarey, of the Geological Survey of Canada, with that at Flack Lake.

The area mapped to date has been described by Chandler (1970a) as follows:

"...The northern and greater part of the area is underlain by granitic rocks of Archean age. Banded gneisses occur in the northern part of the map- area but most of the Archean terrain is underlain by massive granitic rocks, large parts of which are porphyritic." West-northwest foliation is character istic of the earlier Archean rocks. "Huronian sedimentary rocks rest nonconformably upon the dissected and weathered Archean surface. They occur as outliers in northern and eastern Morin Township and occupy large areas of the southern part of both townships. The lower part of the succession, dominantly feldspathic sandstones with subordinate ortho- and paraconglomerates, has been placed by earlier workers in several stratigraphic positions [see Collins 1925; Frarey 1959; Giblin and Leahy 1967]. Recognition of a previously unmapped continuous massive sandy - 13 -

paraconglomerate in the lower sandstones permitted separation of these hitherto undivided rocks into lower and upper sandstone units. The order of stratigraphic succession and field appearance of these sandstones and the enclosed conglomerate permit tentative correlation with the Matinenda, Ramsay Lake, and Mississagi Formations of the Elliot Lake area [Robertson, Frarey, and Card 1969]. These rocks are succeeded by the mixed clastic assemblage of the Gowganda Formation and sandstone of the Lorrain Formation" (see also Frarey 1971). "In southwestern McMahon Township, mafic to intermediate amygdaloidal volcanic rocks have been faulted up against rocks of the Gowganda and Lorrain(?) Formations which lie to their northeast. In Morin Township, small outcrops of mafic volcanic rocks occur intermittently at or near the base of the Matinenda Formation." A quartz-pebble conglomerate several feet thick and sandwiched between two volcanic units contains significant concentrations of uranium (Chandler 1970c). "Large irregular bodies of Nipissing-type quartz diabase are concordant or discordant intrusions within Huronian and Archean rocks. Many small mafic dikes trend west-northwest. Few olivine diabase dikes and one of mica peridotite ... cut the Gowganda Formation. Though pyrophyllite has been observed locally in aluminous sandstones [Chandler et^ aJU 1969] signs of regional metamorphism were not visible in the field.

"...Although the overall dip of Huronian rocks is moderate and toward the south or southwest, the Archean topography has locally influenced the attitude of the strata. A combination of Archean and present topography and the relatively gentle dip has produced an outcrop distribution complicated by outliers and inliers and sinuous boundaries. Faulting has affected the area to a minor extent. West-northwest-striking foliation occurs in the Archean rocks particularly in the north. Some argillaceous rocks of the Gowganda Formation and mafic volcanic rocks are sheared in the southern part of the map-area." Preliminary maps (Chandler 1970b,c) have been published and laboratory and microscope research is underway.

2. OTHER PROVINCIAL, OR FEDERAL, OR JOINT ACTIVITIES

Members of the government surveys also have been collecting drill hole data and samples, compiling maps, etc., and have held many discussions and field trips with personnel from industry and the academic communities. Now that core may be deposited for additional assessment credit, considerable quantities have been submitted from the Elliot Lake camp and are stored by the Resident Geologist in Sault Ste. Marie. Core above the requirements of the Mining Act also has been donated by companies or has been collected by government personnel. It is hoped that several complete cores will be preserved as standard reference sections in conjunction with the Federal-Provincial Committee on Huronian Stratigraphy. Several exploration and mining companies have agreed not to dispose of core without giving government agencies the chance to salvage material of particular scientific interest. One 4,000-foot core - 14 -

drilled in the Flack Lake area has been transported to the Mining Research Station of the Mines Branch, Department of Energy, Mines and Resources, in Elliot Lake. This core comprises the most complete, available, section of the Bar River and Gordon Lake Formations and much of the Lorrain Formation. Attempts have been made to measure these formations as exposed on Highway 639 (Woodward 1970). The surface section on Quirke Lake also has been measured by T. Bottrill, formerly of the Geological Survey of Canada, in 1969, in liaison with the writer. These measured sections are on file in the Toronto and Sault Ste. Marie offices of the Ontario Department of Mines and Northern Affairs. These sections, at Quirke Lake and Highway 639, were designated a composite Principal Reference Section for the Huronian Supergroup (Robertson, Card, and Frarey 1968; 1969; Robertson, Frarey, and Card 1969). Other localized sections were designated reference sections. In general, these other sections are the best exposed in the areas in question but lack of outcrop or structural complications inhibit accurate measurement. Although the measured section is on Quirke Lake, most of the features can be seen on the roads adjacent to Quirke Lake over what the writer terms the ©education© section. In the light of new mapping, corrections to old mapping, new data from companies, and the revised stratigraphic nomenclature of the Federal- Provincial Committee on Huronian Stratigraphy, the regional compilation maps are being revised by Robertson (Elliot Lake quadrant of the Sault Ste. Marie-Elliot Lake sheet, ODMNA Map P.304 revised 1971, Robertson 1971c) and Card (Panache Lake area, ODMNA Maps P.668, P.669, Card 1971b,c). The Geological Survey of Canada and the Mines Branch of the Federal Department of Energy, Mines and Resources have carried out a study relating the regional tectonic features to the orientation of the in situ stresses encountered in mine workings. This study has resulted in examination (Bielenstein and Eisbacher 1969; Eisbacher 1969; 1970; Eisbacher and Bielenstein 1969; 1970) of attitudes of minor quartz veins and orientation of tectonically disturbed clasts in conglomerates throughout the area. Of interest has been the study of clastic intrusions particularly in the Espanola Formation and, to a lesser extent, the Mississagi Formation (Eisbacher 1970; 1971; Robertson 1971a). These conglomerate and siltstone dikes, derived from unconsolidated Bruce Conglomerate, were intruded into ©tension© fractures in partly consolidated rocks during an early stage of the regional folding. The regional study by Bielenstein and Eisbacher (1969) confirmed comparatively recent conclusions that the area was stressed in both the Penokean and Hudsonian tectonic events and that the Flack Lake area should be included in the Penokean fold belt or the Southern Province of the Canadian Shield. The Geological Survey of Canada has continued the development of multi channel spectrometers (Darnley 1970; Killeen and Carmichael 1970). Bottrill (1971) has carried out studies providing ground control for the airborne studies. The resultant data has not yet been fully published (Darnley 1970; 1971; Bottrill 1971). Radon surveys have also been carried out in areas not - 15 -

contaminated from mine tailings (Dyck 1969; Dyck and Pelchat 1969; Smith 1969; Smith and Dyck 1969). Dyck (1969; Dyck and Pelchat 1969) showed that the radon-in-soil surveys outlined radioactive sources more clearly than geiger-counter surveys. At the Quirke Mine he found that radon surveys outlined the ore zone at surface more distinctly than gamma-ray spectrometry. Studies of radon in water in the Elliot Lake area (Smith and Dyck 1969; Smith 1969; Dyck and Pelchat 1969) were hampered because of contamination from tailings ponds. Better results were obtained in the Bancroft area and the method has merit in areas where contamination is not a problem.

3. EXPLORATION Recently there has been a period of intense exploration, particularly in the western part of the area under discussion and in the North Channel of Lake Huron (Figure 4). This has been carried out mainly by large oil or mining companies. There has been an emphasis on geological study and deep drilling. Heavy- duty equipment has been used, proper geometrical control of drilling has been general, improved radiation-detection devices have been widely used and systematic reliable analyses for uranium, thorium, and rare earths have been standard practice. Not all the data obtained has been made public.

The stratigraphic studies have confirmed the presence of volcanic rocks in the sequence (see above) and these are much more widely distributed than previously realized (see Figure 3). Roscoe©s (1969, p.42-44) subdivision of the Matinenda Formation into three members, Ryan, Stinson (which can be further subdivided into a quartzite and a conglomerate unit), and Manfred, has been shown to be useful, at least within the Quirke Syncline. The drilling has delineated the distribution of these members more accurately than was possible when Roscoe published his review. Although these units have been designated as members, there is growing evidence that they are as significant as some units designated as formations elsewhere in the Huronian stratigraphic column. The Elliot Lake Group, as currently defined, contains an unconformity, below which the sequence comprises the Ryan Member of the Matinenda Formation and associated volcanic rocks, and above which the sequence comprises the Stinson and Manfred Members of the Matinenda Formation, the McKim Formation, and associated volcanic rocks. The ore-bearing conglomerate beds of the Quirke zone are in the Manfred Member and those of the Nordic, Pardee, and Pecors zones (Robertson 1967) are in the Ryan Member as currently defined. Drilling and underground operations are of sufficient density that these conglomerate beds and intervening quartzite beds can be traced confidently over wide areas and can be formally named. But a more refined stratigraphic nomenclature may be necessary for these rocks within the Quirke Syncline. The drilling north of the Flack Lake Fault consists of shallow holes in the vicinity of outcrop of the radioactive unit in the Lorrain Formation and a few deeper holes, which either reached basement without entering any Huronian unit underlying the Gowganda Formation or failed to reach basement. The stratigraphic results have been summarized by Eisbacher and Bielenstein (1969) and the indications are that the maximum thickness of Huronian strata present - 16 -

north of the Flack Lake Fault is 5,000 feet and that formations older than the Gowganda are not present. The drilling northwest of Matinenda Lake and west of the Little White River is rather sparse. The data available (ODMNA assessment work files) indicates that the present location of the Little White River coincides with a fault, which was probably active after, rather than during, Lower Huronian sedimentation but possibly is pre-Gowganda in age (T. Bottrill 1970, personal communication). Another important feature is a basement high or shelf running southeast from Haughton Township, known as the Haughton High or Wakomata High. The surface expression of this high can be seen in the nature of the Huronian- Archean contact as shown by Giblin and Leahy (1967) on the regional compilation map. The lower Huronian sequence, including the Thessalon Volcanics and the Livingstone Creek Formation, both with scattered uraniferous pebble bands, occurs to the southwest of this high, and the high itself is only overlain by Gowganda Formation, indicating that earlier it was an area of non-deposition. Another high lies approximately along the zone defined by the Parkinson Dome and the Chiblow Anticline and is clearly expressed in Spragge and Lewis Townships (Robertson 1970a, p.21; 1969b). The Chiblow-Lewis High lies just north of the Pronto ore zone (Robertson 1970a; 1969b). Following the recent drilling and geological exploration in Aberdeen, Kehoe, and Duncan Townships (ODMNA assessment work files) parts of the Sault Ste.Marie and Echo Lake map-areas were revisited by Frarey (1971) who has published a sketch map amending his original interpretation of the stratigraphy of the Echo Lake area, particularly in regard to the recognition and distribution of quartzitic rocks previously assigned to the Serpent Formation. The work of Texas Gulf Sulphur Company and Ecstall Mining Limited on leases in the North Channel of Lake Huron has led to a fuller understanding of the geology along the North Shore of Lake Huron between Bruce Mines and the Mississagi River. Frarey (1971) has confirmed that a conglomeratic sequence of rocks on islands between Larry Island and Pallideau Island should be placed in the Gowganda Formation rather than the Espanola Formation, and that the Serpent Formation is also present on Larry Island. In the vicinity of Blind River and Lauzon Lake work by United Nuclear Mines (Canada) Limited and by Denison Mines Limited has led to a reinterpre- tation of the correlation of argillaceous rocks previously assigned by Robertson (1964; 1970a) to the Middle Mississagi Formation (Pecors Formation of the new nomenclature). In the Lauzon area employees of Denison Mines Limited were able to locate the Ramsay Lake Conglomerate to the southeast of the Lake of the Mountains Fault and establish that the argillaceous rocks exposed along the north shore of Lauzon Lake to Pronto Mine were McKim Formation rather than Pecors as indicated in Robertson©s earlier mapping (see Robertson, Card, and Frarey 1969, chart, for correlation of old and new nomenclature). The Ramsay Lake and Pecors Formation are largely under water (C.E. Blackburn, M.E. Woakes 1967, personal communications). Drill hole data clearly show that in this area the rocks of the McKim Formation are interbedded thick siltstone and quartzite units with little true argillite, whereas the Pecors Formation includes thinly-bedded argillite as the major rock type. The drilling and mapping carried out by United Nuclear Mines (Canada) Limited in the vicinity of Blind River south of the Murray Fault, using the above - 17 -

criteria, has led to revision of the correlation of argillaceous units and adjacent quartzites. This data has been included in the revised compilation map (Robertson 1971c) of the area by kind permission of F.Q. Barnes of G.S. Robertson and Associates of Blind River.

The data released on uranium mineralization discovered during the recent exploration has been meagre and by and large such data concerns extensions of known zones of mineralization. Underground work at Denison Mine has confirmed the presence of ore-grade conglomerate between the Denison and Can-Met Mines and between the Denison and Spanish American Mines. The correlation of individual reefs from one mine to another in the Quirke Lake area is now on a firm basis.

In addition to geological and geophysical surveys, some companies have undertaken petrographic and mineralogic research. As yet this data has not been released in any form.

In view of the similarity between environments explored for oil and gas and the Huronian environment for uranium there has been considerable interest in the seismic experiments carried on by A. Overton (1967; 1969) of the Geological Survey of Canada. Both reflection and refraction techniques have been attempted. The following conclusions were reached: (1) seismic velocities for each formation may be expected to vary laterally as much as they vary from one formation to another; (2) differences in seismic velocity between formations need not maintain a constant relationship in an areal sense but may vary haphazardly; (3) on the average, seismic velocities may vary by only a few hundred feet per second between the formations. The final assessment is therefore that the seismic technique is of no avail in the exploration for uranium in the Huronian environment.

Aeromagnetic maps are available for the greater part of the Huronian area (ODM 1954; 1955; ODM-GSC 1963; 1964); these have permitted delineation of certain intrusions, faults, volcanic rocks, and iron formation or other magnetite-bearing sedimentary rocks. In one area of the Quirke Syncline attempts had been made, using second-derivative maps (Steenland and Brod 1960), to predict depths to greenstone basement. The results were not contradicted by limited drilling (Steenland and Brod 1960).

Lockwood Survey Corporation Limited (Spector 1970) has developed a method of energy-spectrum analysis of aeromagnetic data using a digital computer whereby the short-wave near-surface responses are filtered out and a long-wave residual response due to supposedly deep-seated structures is retained for interpretation. Such an interpretation was made for a selected area within the Huronian environment. The depths to basement predicted are not unreasonable but as yet the interpretation has not been tested by drilling.

4. MISCELLANEOUS STUDIES

In addition to the efforts of the government agencies and of industry there has been much interest in the Huronian Supergroup shown by staff and students from the university community. This activity has taken the form of theses and papers, field trips, field schools, and workshops. - 18 -

Workshops were held in 1970 under the auspices of the Geological Survey of Canada (Baer 1970, especially papers by Frarey and Roscoe 1970, Pettijohn 1970, and discussions following these papers) and the University of Western Ontario, enabling interchange between those working on Precambrian sedimen tation basins and geosynclines. The papers given at the GSC workshop have been published (Baer 1970). In the last few years the number of university groups and other institutional groups having field trips in the Elliot Lake area has grown markedly. Several universities use the area to teach the mapping of sedimen tary and moderately deformed rocks. The nature of the rocks, the excellent exposure, reasonable access, and accommodations make the area ideal for instructional purposes. It is hoped that in their enthusiasm such visitors will not deface critical outcrops and thus detract from the usefulness of the area for teaching purposes. The recently published studies on the area have been on: sedimentology (Casshyap 1968; 1969; Chandler 1969; Hadley 1968; 1969; Lindsey 1966; 1969; Lindsay et^ a^. 1970; Ovenshine 1965; 1970; Wood 1970a,b; Young 1968; 1969b; 1970a); correlation in the vicinity of Lake Superior (Church and Young 1970; Young 1970a,b); and the presence of aluminous minerals in the sandstones and quartzites of the Lorrain Formation (Chandler et^ aK 1969; Chandler 1969; Wood 1970a,b; Young 1970b). However, the major interest has been in the Gowganda Formation and in the polymictic diamictites that occur in the Bruce and Ramsay Lake Formations. Young (1969b) has published data on the geochemistry of the Gowganda Formation, which has been contrasted with meagre data on the other units by Robertson (1970b). Ovenshine (1965; 1970), Lindsey (1969), Young (1970a), and Young and Chandler (1968) have further aggregated and added to the data in support of a glacial environment for not only the Gowganda Formation but for the other diamictic units throughout the Huronian sequence. Supposed tillite fabrics have been studied by Young (1968), Casshyap (1968; 1969), Lindsey (1966; 1969), Ovenshine (1965; 1970), and by Lindsay et^ aU (1970). However studies by Chandler (1969) in the La Cloche area, Bielenstein and Eisbacher (1969) in the Elliot Lake area and regional mapping by Robertson (1968; 1971b) indicate that deduction of current or ice-flow directions from clast orien tation is suspect as the post-depositional deformation is regionally suffi ciently intense to have re-aligned the clasts relative to matrix. Lindsey (1966; 1969) has also studied the Gowganda Formation and has suggested a northern or continental area containing varved rocks and a southern or marine area containing laminated rocks. It was thought, by Lindsey, that the salt of marine waters caused rapid precipitation of colloidal matter and prevented the development of graded bedding in the argillaceous material. The southward change in facies from a conglomeratic massive bedded sequence to a less conglomeratic well-bedded sequence had been previously recognized. The Gowganda Formation thus shows the same pattern of southward thickening and change to deeper water facies as the other Huronian formations. Robertson (1970c; Robertson and Johnson 1970) further noted, even at the northern limit of exposure at Mount Lake, a dominant influence of water and suggested that there the densely packed boulder conglomerates were laid down by flash floods washing material from - 19 -

Archean hills into basins controlled by ancient faults and characterized by quiescent deposition with distal turbidites. The geochemistry of the rocks, the lack of weathering of feldspars and mafic minerals, and the association with thinly laminated rocks containing ©rafted 1 clasts, point to accumulation under frigid conditions, but whether the diamictites are ©tillites 1 , marine or otherwise, or mud-flow deposits derived from till remains an open question. Study of sulphide geochemistry has been dormant since the work of Pienaar, reported in Pienaar (1963) and Roscoe (1969). Sulphur isotope studies are being undertaken by M.L. Jensen, of University of Utah, Salt Lake City, Utah, on material collected by Bottrill. As yet only preliminary data have been obtained and nothing has been published.

CONCLUDING REMARKS Thus in the last few years the continued investigation of government geologists, mining and exploration companies, and university staff and students has yielded much new data, correction or reinterpretation of older data, new ideas, and pointed up some areas worthy of further research. Preparation of revised compilation maps and regional reports are underway, and a comprehensive paper on the Southern Province of the Canadian Shield is being prepared by Card and others as part of the Symposium in Structural Styles of the Canadian Shield being organized by the Geological Association of Canada as a contribution to the 24th International Geological Congress in 1972. Evaluation of much of the new data is still in progress.

ACKNOWLEDGMENTS The writer wishes to acknowledge many rewarding discussions, field trips, and core logging sessions held with colleagues on the Federal and Ontario surveys, with geologists of the mining and exploration companies, with the staff and students, both graduate and undergraduate, of many Canadian and American universities and several overseas universities. In the preparation of this paper much data, advice and helpful criticism was given by T.J. Bottrill, F.W. Chandler, M.J. Frarey, R.J. Rupert, and John Wood. The writer is particularly grateful to Raimonds Balgalvis of the Review and Resources Section, Geological Branch, Ontario Department of Mines and Northern Affairs, for assistance in the preparation of illustrations. - 20 -

SELECTED REFERENCES

Baer, A.J. (Editor) 1970: Symposium on basins and geosynclines of the Canadian Shield; Geol. Surv. Canada, Paper 70-40, 265p. Bielenstein, H.U., and Eisbacher, G.H. 1969: Tectonic interpretation of clastic-strain-recovery measurements at Elliot Lake, Ontario; Mines Branch Research Report R210, Dept. of Energy,Mines and Resources, Ottawa, 64p. Accompanied by 3 charts. Boissonneau, A.N. 1968: Glacial history of northeastern Ontario II, The Timiskaming- Algoma area; Canadian J. Earth Sci., Vol. 5, No.l, p.97-109. Bottrill, T.J. 1970: Geology and genesis of uranium deposits in the Huronian and associated geology, Blind River, Sudbury, and Gowganda areas, Ontario (41 I,J,O,P); p.57-58 In Report of Activities, Part A: April to October, 1969, Geol. Surv. Canada, Paper 70-1, pt.A, 251p. 1971: Uraniferous conglomerates of the Canadian Shield; p.77-83 in Report of Activities, Part A: April to October, 1970, Geol. Surv. Canada, Paper 71-1, pt.A, 259p. Cannon, William F. 1970: Plutonic evolution of the Cutler area, Ontario; Geol. Soc. America, Bull., Vol. 81, No.l, p.81-94. Card, K.D. 1971a: The Sudbury structure, its regional geological setting; paper given at the 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury. 1971b: Panache Lake area (West Part), Districts of Sudbury and Manitoulin; Ontario Dept. Mines and Northern Affairs, Prelim. Map P.668, Geol. Series, scale l inch to l mile. Geological compilation 1971. 1971c: Panache Lake area (East Part), Districts of Sudbury and Manitoulin; Ontario Dept. Mines and Northern Affairs, Prelim. Map P.669, Geol. Series, scale l inch to l mile. Geological compilation 1971. Card, K.D., Mcilwaine, W.H., and Meyn, H.D. 1970: Operation Maple Mountain, Districts of Timiskaming, Nipissing, and Sudbury; Ontario Dept. Mines and Northern Affairs, OFR5050, 275p. Accompanied by P.584 and P.585, scale l inch to l mile. Card, K.D., and Pattison, E. 1971: Nipissing Diabase of the Southern Province; paper given at the Huronian Symposium, 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury, Carrington, J.K., and Wilton, C.K. 1969: Economic geology of Agnew Lake Mines Limited (abstract); paper given at 71st Annual Meeting of Canadian Inst. Mining and Metallurgy, Montreal, 1969, CIM Bull., Vol. 62, No.683, p.215. - 21 -

Gasshyap, S.M. 1968: Huronian stratigraphy and paleocurrent analysis in the Espanola- Willisville area, Sudbury District, Ontario, Canada; J. Sed. Pet., Vol. 38, No.3, p.920-942. 1969: Petrology of the Bruce and Gowganda Formations and its bearing on the evolution of Huronian sedimentation in the Espanola-Willisville area, Ontario, Canada; Palaeogeography, Paleoclimatology, Paleoecology, Vol. 6, p.5-36. 1971: Petrology and sedimentation of Huronian arenites, south of Espanola, Ontario; Canadian J. Earth Sci., Vol. 8, No.l, p.20-49. Chandler, F.W. 1969: Geology of the Huronian rocks, Harrow Township area, Ontario; unpubl. Ph.D. thesis, University of Western Ontario, London, Ontario, 1970a: McMahon and Morin Townships, District of Algoma; p.41-44 in Summary of Field Work, 1970, by the Geological Branch, edited by E.G. Pye, Ontario Dept. Mines and Northern Affairs, MP43, 96p. 1970b: McMahon Township, District of Algoma; Ontario Dept. Mines and Northern Affairs, Prelim. Geol. Map P.620, scale l inch to 1/4 mile. Geology 1970. 1970c: Morin Township, District of Algoma; Ontario Dept. Mines and Northern Affairs, Prelim. Geol. Map P.621, scale l inch to 1/4 mile. Geology 1970. Chandler, F.W., Young, G.M., and Wood, J. 1969: Diaspore in Early Proterozoic quartzite (Lorrain Formation) of Ontario; Canadian J. Earth Sci., Vol. 6, No.2, p.337-340. Church, W.R. 1967: The occurrence of kyanite, andalusite, and kaolinite in Lower Proterozoic (Huronian) rocks of Ontario (abstract); p.14-15 in Technical Programme, Abstracts of Papers, Geol. Assoc. Canada, Kingston 1967, 117p. 1968: The Penokean and Hudsonian Orogenies in the Great Lakes region and the age of the Grenville Front (abstract); p.16-18 in 14th Annual Institute on Lake Superior Geology, Superior, Wisconsin, 6Ip. 1971: Comparative geology of early Proterozoic and early Phanerozoic orogenic belts; paper given at Huronian Symposium, 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury. Church, W.R., and Young, G.M. 1970: Discussion of the Progress Report of the Federal-Provincial Committee on Huronian Stratigraphy; Canadian J. Earth Sci., Vol. 7, No.3, p.912-918. CIM 1969: Abstracts of papers given at the 71st Annual General Meeting in Montreal 1969. CIM Bull., Vol. 62, No.683, p.195-221. - 22 -

Collins, W.H. 1925: North Shore of Lake Huron; Geol. Surv. Canada, Mem. 143, 160p. Accompanied by Maps 1969, 1970, 1971, scale l inch to 2 miles. Darnley, A.G. 1970: Airborne gamma-ray spectrometry; CIM Bull., Vol. 63, No.694, February, p.l45-l54.

1971: Airborne gamma spectrometry surveys in the areas of Elliot Lake, Ontario and Fort Smith, Northwest Territories; p.48-49 in Report of Activities, Part A: April to October, 1970, Geol. Surv. Canada, Paper 71-1, pt.A, 259p. Donaldson, J.A. 1967: Precambrian vermiform structures: A new interpretation; Canadian J. Earth Sci., Vol. 4, No.6, p.1273-1276. Douglas, R.J.W. (Editor) 1971: Geology and economic minerals of Canada; 5th edition, Geol. Surv. Canada, Economic Geology Report No. l, 838p. Accompanied by separate case with 8 maps and 4 charts. Dyck, Willy 1969: Uranium exploration using radon in soils; Canadian Min. J., Vol. 90, No.8, p.45-49. 1970: Uranium exploration using radon in soils (abstract); p.7 in Abstracts of publications in scientific journals by officers of the Geological Survey of Canada, April 1969 to March 1970, Geol. Surv. Canada, Paper 70-4, 42p. Dyck, Willy, and Pelchat, J.C. 1969: Development of radiochemical exploration methods using radon, Ontario and Quebec; p.51-54 ir± Report of Activities, Part A: April to October, 1968, Geol. Surv. Canada, Paper 69-1, pt.A, 263p.

Eisbacher, G.H. 1969: Regional structural study in the Elliot Lake area, Ontario (41 J/7); p.158-161 in Report of Activities, Part A: April to October, 1968, Geol. Surv. Canada, Paper 69-1, pt.A, 263p. 1970: Contemporaneous faulting and clastic intrusions in the Quirke Lake Group, Elliot Lake; Canadian J. Earth Sci., Vol. 7, No.2, pt.l, p.215-225. 1971: Contemporaneous faulting and clastic intrusions in the Quirke Lake Group, Elliot Lake, Ontario: Reply; Canadian J. Earth Sci., Vol. 8, No.2, p.308. Eisbacher, G.H., and Bielenstein, H.U. 1969: The Flack Lake depression, Elliot Lake area, Ontario (41 J/10); p.58-60 in Report of Activities, Part B: November, 1968 to March, 1969, Geol. Surv. Canada, Paper 69-1, pt.B, 80p. - 23 -

1970: Interpretation of elastic-strain-recovery measurements near Elliot Lake, Ontario; Canadian J. Earth Sci., Vol. 7, No.2, pt.2, p.576-578

Emmens, R.C. 1927: Wakomata Lake map-area, Algoma District, Ontario; Geol. Surv. Canada, Summary Rept. 1926, pt.C, p.lC-15C. Fairbairn, H.W., Faure, G., Pinson, Jr., W.H., and Hurley, P.M. 1968: Rb-Sr whole-rock age of the Sudbury lopolith and basin sediments; Canadian J. Earth Sci., Vol. 5, No.3, pt.2, p.707-714.

Fairbairn, H.W., Hurley, P.M., Card, K.D., and Knight, C.J. 1969: Correlation of radiometric ages of Nipissing Diabase and Huronian metasediments with Proterozoic orogenic events in Ontario; Canadian J. Earth Sci., Vol. 6, No.3, p.489-497. Frarey, M.J. 1959: Geology, Echo Lake, District of Algoma, Ontario; Geol. Surv. Canada, Map 23-1959, scale l inch to l mile. 1967: Three new Huronian fonnational names j Geol. Surv. Canada, Paper 67-6, 3p. 1971: Huronian rocks north of Lake Huron; p.128-133 in Report of Activities, Part A: April to October, 1970, Geol. Surv. Canada, Paper 71-1, pt.A, 259p. Frarey, M.J., and Roscoe, S.M. 1970: The Huronian Supergroup north of Lake Huron; p.143-157 in Symposium on basins and geosynclines of the Canadian Shield, edited by A.J,. Baer, Geol. Surv. Canada, Paper 70-40, 265p. Also 3 responses on p.158.

Giblin, P.E., and Leahy, E.J. 1967: Sault Ste. Marie-Elliot Lake, Algoma, Manitoulin, and Sudbury Districts; Ontario Dept. Mines, Geol. Comp. Series Map 2108, scale l inch to 4 miles. Geological compilation 1964-1965.

Hadley, D.G. 1968: Sedimentology of the Huronian Lorrain Formation, Ontario and Quebec, Canada; unpubl. Ph.D. thesis, Johns Hopkins University, Baltimore, Maryland, 301p. 1969: Depositional frame work of the jasper-rbearing conglomerate in the Lorrain Formation, Ontario, Canada (abstract); Geol. Soc. America, Abstracts with Programs for 1969, pt.7, 82nd. Annual Meeting, Atlantic City, New Jersey, p.87-88.

Harding, W.D. 1939: Geology of the Flack Lake area; Ontario Dept. Mines, Vol. 48, pt.11, 12p. (published 1941). Accompanied by Map 48k, scale l inch to l mile. - 24 -

Hoffman, H.J. 1967: Precambrian fossils(?) near Elliot Lake, Ontario; Science, Vol. 156, No.3774, p.500-504. Kirkham, R. 1971: Geological exploration guides for stratiform copper deposits in sedimentary sequences; a paper given at the 39th Annual Convention, Prospectors and Developers Association, Toronto, March 1971.

Killeen, P.G., and Carmichael, C.M. 1970: Gamma-ray spectrometer calibration for field analysis of thorium, uranium and potassium; Canadian J. Earth Sci. , Vol. 7, No.4, p.1093-1098.

Lindsay, John F., Summerson, C.H., and Barrett, P.J. 1970: A long-axis clast fabric comparison of the Squantum "Tillite", Massachusetts and the Gowganda Formation, Ontario; J. Sed. Pet., Vol. 40, No.l, p.475-479.

Lindsey, David A. 1966: Sediment transport in a Precambrian ice age: The Huronian Gowganda Formation; Science, Vol. 154, No.3755, p.1442-1443.

1969: Glacial sedimentology of the Precambrian Gowganda Formation, Ontario, Canada; Geol. Soc. America Bull., Vol. 80, No.9, p.1685-1701.

1971: Glacial marine sediments in the Precambrian Gowganda Formation at Whitefish Falls, Ontario (Canada); Palaeogeography, Paleoclimatology, Paleoecology, Vol. 9, p.7-25. Meyn, H.D. 1971: Proterozoic geology northeast of Sudbury; paper given at Huronian Symposium, 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury.

ODM 1954: Township aeromagnetic and radioactivity maps - Algoma Block, 12 townships; Ontario Dept. Mines, scale l inch to 1,320 feet. Flown and compiled February and March, 1954. 1955: Township aeromagnetic and radioactivity maps - Blind River Block, 16 townships; Ontario Dept. Mines, scale l inch to 1,320 feet. Flown and compiled February and March, 1955.

ODM-GSC 1963: Algoma Sheet, Algoma and Manitoulin Districts, Ontario; Ontario Dept. Mines-Geol. Surv. Canada, Aeromagnetic Map 2240G, scale l inch to l mile. Survey October 1962 to May 1963. 1964: Elliot Lake Sheet, Algoma District, Ontario; Ontario Dept. Mines- Geol. Surv. Canada, Aeromagnetic Map 3237G, scale l inch to l mile. Survey 1954 to 1956, compiled 1963. - 25 -

Ovenshine, A.T. 1965: Sedimentary structures in portions of the Gowganda Formation, North Shore of Lake Huron, Canada; unpubl. Ph.D. thesis, University of California at Los Angeles, California. 1970: Observations of iceberg rafting in Glacier Bay, Alaska, and the identification of ancient ice rafted deposits; Geol. Soc. America Bull., Vol. 81, No.3, p.891-894. Overton, A. 1967: Seismic studies, Elliot Lake Area; p.155-157 ii^ Report of Activities, Part A: May to October, 1966, edited by S.E. Jenness, Geol. Surv. Canada, Paper 67-1, pt.A, 221p. 1969: Seismic data evaluation, Elliot Lake area, Ontario; p.40-41 in Report of Activities, Part B: November, 1968 to March, 1969, Geol. Surv. Canada, Paper 69-1, pt.B, 80p.

Pettijohn, F.J. 1970: The Canadian Shield. A status report, 1970 (and discussion); p.239-255, 262-265 in Symposium on basins and geosynclines of the Canadian Shield, edited by A.J. Baer, Geol. Surv. Canada, Paper 70-40, 265p. Pienaar, P.J. 1963: Stratigraphy, petrology and genesis of the Elliot Group, Blind River, Ontario, including the uraniferous conglomerate; Geol. Surv. Canada, Bull. 83, 143p. Robertson, David S., and Douglas, Richard F. 1970: Sedimentary uranium deposits; CIM Bull., Vol. 63, No.697, May, p.557-566. Robertson, James A. 1961: Geology of Townships 143 and 144; Ontario Dept. Mines, GR4, 65p. Accompanied by Maps 2001 and 2002, scale l inch to 1/4 mile. 1962: Geology of Townships 137 and 138; Ontario Dept. Mines, GR10, 94p. Accompanied by Maps 2003 and 2004, scale l inch to 1/4 mile, and 2 charts. 1963: Geology of Townships 155, 156, 161, 162; Ontario Dept. Mines, GR13, 88p. Accompanied by Maps 2014, 2015, 2026, and 2027, scale l inch to 1/4 mile; and Map 2032, scale l inch to 2 miles. 1964: Geology of Scarfe, Mack, Cobden and Striker Townships; Ontario Dept Mines, GR20, 89p. Accompanied by Map 2028, scale l inch to 1/2 mile; and Map 2032, scale l inch to 2 miles. 1967: Recent geological investigations in the Elliot Lake-Blind River uranium area, Ontario; Ontario Dept. Mines, MP9, 31p. plus 8 figures. - 26 -

1968: Geology of Township 149 and Township 150; Ontario Dept. Mines, GR57, 162p. Accompanied by Maps 2113 and 2114, scale l inch to 1/4 mile, and 5 charts.

1969a: Geology and uranium deposits of the Blind River area, Ontario; CIM, Trans., Vol. 72, p.156-171. Also CIM Bull., Vol. 62, No.686, p.619-634.

1969b: Geology of the Cutler area, District of Algoma; Ontario Dept. Mines, OFR5026, 119p. Accompanied by 5 maps, scale l inch to 1/4 mile,

1969c: Township 157, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.561, scale l inch to 1/4 mile. Geology 1969.

1970a: Geology of the Spragge area; Ontario Dept. Mines, GR76, 109p. Accompanied by Maps 2185 and 2186, scale l inch to 1/2 mile, and Chart A.

1970b: Geology of the Massey area, Districts of Algoma and Sudbury; Ontario Dept. Mines, OFR5043, 2 folders, 150p. Accompanied by 3 maps, scale l inch to 1/4 mile.

1970c: Township 1A, District of Algoma; Ontario Dept. Mines and Northern Affairs, Prelim. Geol. Map P.610, scale l inch to 1/4 mile. Geology 1970.

1970d: Townships 1A and IB, District of Algoma; p.44-50 in Summary of Field Work, 1970, by the Geological Branch, edited by E.G. Pye, Ontario Dept. Mines and Northern Affairs, MP43, 96p.

1971a: Contemporaneous faulting and clastic intrusion in the Quirke Lake Group, Elliot Lake, Ontario: Discussion; Canadian J. Earth Sci., Vol. 8, No.2, p.307-308.

1971b: A long-axis clast fabric comparison of the Squantum ©Tillite© Massachusetts and the Gowganda Formation, Ontario: Discussion of Paper by Lindsay et^ aK , J. Sed. Pet., June, 1971. 1971c: Blind River-Elliot Lake Sheet, Districts of Algoma and Sudbury; Ontario Dept. Mines and Northern Affairs, Prelim. Map P.304, Geol. Comp. Series, scale l inch to 2 miles. Revised 1971.

Robertson, J.A., and Card, K.D. In press: Geology and scenery of the North Shore of Lake Huron; Ontario Dept. Mines and Northern Affairs, Guide Book 4.

Robertson, J.A., Card, K.D., and Frarey, M.J. 1968: The Federal-Provincial Committee on Huronian Stratigraphy Progress Report (abstract); p.33-34 in 14th Annual Institute on Lake Superior Geology, Superior, Wisconsin, 61p.

1969: The Federal-Provincial Committee on Huronian Stratigraphy Progress Report; Ontario Dept. Mines, MP31, 26p. Accompanied by correlation chart. - 27 -

Robertson, J.A., Frarey, M.J., and Card, K.D. 1969: The Federal-Provincial Committee on Huronian Stratigraphy Progress Report; Canadian J. Earth Sci., Vol. 6, No.2, p.335-336.

Robertson, J.A., and Johnson, J.M, 1969: Township 163, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.560, scale l inch to 1/4 mile. Geology 1969. 1970: Township IB, District of Algoma; Ontario Dept. Mines and Northern Affairs, Prelim. Geol. Map P.609, scale l inch to 1/4 mile. Geology 1970. Roscoe, S.M. 1957: Geology of uranium deposits, Quirke Lake-Elliot Lake, Blind River area, Ontario; Geol. Surv. Canada, Prelim. Rept. Paper 56-7. 1969: Huronian rocks and uraniferous conglomerates in the Canadian Shield; Geol. Surv. Canada, Paper 68-40, 205p. Roscoe, S.M., and Frarey, M.J. 1970: Comments on The Canadian Shield. A status report 1970 by F.J. Pettijohn; p.255-262 in Symposium on basins and geosynclines of the Canadian Shield, edited by A.J. Baer, Geol. Surv. Canada, Paper 70-40, 265p. Roscoe, S.M., and Steacy, H.R. 1958: On the geology and radioactive deposits of the Blind River region; Atomic Energy of Canada Ltd., Chalk River, Ontario, Atomic Conf., 15/P/222, 19p., A.E.C.L.-632, September 1958. Smith, A.Y. 1969: Development of geochemical exploration methods for uranium, Bancroft and Elliot Lake, Ontario (31C, 31D, 31E, 31F, 41J); p.56-57 in Report of Activities Part A: April to October, 1968; Geol. Surv. Canada, Paper 69-1, pt.A, 263p. Smith, A.Y., and Dyck, W. 1969: The application of radon methods to geochemical exploration for uranium (abstract); CIM Bull., Vol.62, No.683, p.215. Spector, Allan 1970: Deep uranium exploration with the aid of aeromagnetic maps (abstract); CIM, Bull., Vol. 63, No,695, p.291.

Steenland, Nelson C., and Brod, R.S. 1960: Basement mapping with aeromagnetic data - Blind River Basin; Geophysics, Vol. 25, No.3, p.586-601. Van Schmus, Randall 1965: The geochronology of the Blind River-Bruce Mines area, Ontario, Canada; J. Geol., Vol. 73, No.5, p.755-780. - 28 -

Williams, R.M. 1970: Uranium and thorium; Mineral Review Preprint from Canadian Minerals Yearbook 1969, Mineral Resources Branch, Department of Energy, Mines and Resources, 13p. Wood, J. 1968a: Township U, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.468, scale l inch to 1/4 mile. Geology 1967. 1968b: Township Q, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.474, scale l inch to 1/4 mile. Geology 1967. 1969a: Township 151, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.531, scale l inch to 1/4 mile. Geology 1968. 1969b: Township 145, District of Algoma; Ontario Dept. Mines, Prelim. Geol. Map P.532, scale l inch to 1/4 mile. Geology 1968. 1970a: Evidence for a tropical climate and oxygenic atmosphere in Upper Huronian rocks of the Rawhide Lake-Flack Lake area, Ontario (abstract); p.45-46 in Institute on Lake Superior Geology, 16th Annual Meeting, Thunder Bay, Ontario, lOOp. 1970b: Upper Huronian stratigraphy and sedimentation, Rawhide Lake area, Ontario; unpubl. M.Se. thesis, University of Western Ontario, London, Ontario. 1971: Depositional environment in the Upper Huronian, Flack Lake area, Ontario; paper given at the 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury. Woodward, Nicholas B. 1970: A measured section and description of the Bar River and Gordon Lake Formations along Highway 639, Township 157, Ontario, Canada; unpubl. senior thesis (BA), Cornell University, Ithaca, New York. Young, Grant M. 1967: Possible organic structures in Early Proterozoic (Huronian) rocks of Ontario; Canadian J. Earth Sci., Vol. 4, No.3, p.565-568. 1968: Sedimentary structures in Huronian rocks of Ontario; Palaeogeography, Paleoclimatology, Paleoecology, Vol. 4, p. 125-153. 1969a: Inorganic origin of corrugated vermiform structures in the Huronian Gordon Lake Formation near Flack Lake, Ontario; Canadian J. Earth Sci., Vol. 6, No.4, pt.l, p.795-799. 1969b: Geochemistry of Early Proterozoic tillites and argillites of the Gowganda Formation, Ontario, Canada; Geochim et Cosmochim Acta, Vol. 33, p 483-492. 1970a: An extensive Early Proterozoic glaciation in North America?; Palaeogeography, Paleoclimatology, Paleoecology, Vol. 7, p.85-101. - 29 -

1970b: Widespread occurrence of aluminous minerals in Aphebian Quartzites (abstract); p.47-48 in Institute on Lake Superior Geology, 16th Annual Meeting, Thunder Bay, Ontario, lOOp. 1971: Stratigraphic and sedimentological framework of the Huronian rocks of the Southern Province of the Canadian Shield; paper given at Huronian Symposium, 1971 Annual Meeting of Geol. Assoc. Canada, Sudbury. Young, G.M., and Chandler, F.W. 1968: Possible glacial origin for three Precambrian Huronian conglomerates, North Shore of Lake Michigan (abstract); p.42-43 in 14th Annual Institute on Lake Superior Geology, Superior, Wisconsin, 61p. -30 -

Channel (Lake Huron) - —~- 46

Ontario Department of Mines Ontario Deparfmenf of Mines and Geological Survey of Canada and Northern Affairs Final Maps //////A Northern Affairs Preliminary Maps Preliminary Maps

ODMNA 4756 Figure 2- Key to recent geological maps, North Shore of Lake Huron -31-

Huronian: sedimentary rocks; volcanic rocks. *| Red-phase Algoman granitic rocks Ranger Lal(e *t Granite1^ * ±* J Grey-phase Algoman granitic rocks

Anticline, syncline, with plunge

Archean metavolcanic belts and Post Huronian mafic intrusions not shown.

4 Sf*~V 4- -4^4^4- 4 s-4^,,0' " ™ "-^. 4 4:a(4 444 4^f6y/ 4-^V^V| 5fc? 4 4 4

Croker d\Complex Clappertq ^ l5la"^rWcGregor Soy Anticline ' Figure 3-Generalized geological map of the Blind River- Elliot Lake area -32-

+ + + 44- + + + +I — l l f * * + -f l

Location of drill hole(s). Paleozoic Sedimentary Rocks.

Geological contact. Post-Huronian Granitic Rocks. ——

Fault. Huronian Sedimentary and Volcanic Rocks.

Uranium orebody. Archean Granitic Rocks, ± Volcanic and Sedimentary Rocks

Figure 4 - Location of recent drill holes - Elliot Lake area -33-

x \^ * TP. Q + 4** 4- -f Ji 4- ** 4- 4- 4- 4- 4 4-

PRECAMBRIAN PROTEROZOIC

KEWEENAWAN DIABASE QUIRKE LAKE GROUP AND HOUGH LAKE GROUP

NIPISSING DIABASE

HURONIAN SUPERGROUP

COBALT GROUP ARCHEAN Bar River Formation Granite and greenstone Gordon Lake Formation

Lorrain Formation Geological boundary Thorium marker horizon separating arkose, quartzite Fault Gowganda Formation Syncline with plunge

Figure 5- Geology of the Flack Lake-Rawhide Lake area -34-

La Cloche o 2000 4000 Feet l l l ! l l l ! l

l l l l l l l O 400 800 1200 Metres

GORDON LAKE ^

O 2 4 6 8 10 Miles l l l l l l

LORRAIN Flack Lake JM l BAR RIVER

Aird Island /^ SERPENT Tp. 163 AR l GOWGANDA Ten Mile ESPANOLA Lake 9uirke Lake z- Tp. l B 5-2 AR 2 CM4/ X ^ ~~---. Denvic l/ j' "l f - |SPAN|(Rr ~ - -- ^ - ^ ^ ^ Lake fe Span North D D. H y/ BRUCE ' PA- 24 MISSISSAGI RAMSAY LAKE PECORS~"~

U- Conglomerate* - ^ ^ Jy\A^TINENDA

ARCHEAN

Basement Basement , Basement , 3s "SOUTHER Basement | Basement j Low High LOW Basement High | 2 S HURONIAN Advancing Shore Line ? Advancing Shore Line Quirke Pardee Ore -zone Ore -zone cc "-

ODMNA 4760

Figure 6- Lateral variation of the Huronian Supergroup, Elliot Lake area - 35

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