INIS-mf~11510 Mines and Mineral Division

Ontario Geological Survey Open File Report 5634

Uranium Occurrences of the Thunder Bay-Nipigon- Marathon Area

1987

Ministry of Northern Development and Mines Ontario / :•

©Queen's Printer for Ontario 1987 Printed in Ontario, Canada

ONTARIO GEOLOGICAL SURVEY Open File Report 5634

Uranium Occurrences of the Thunder Bay-Niplgon-Marathon Area

by J.F. Scott 1987

Parts of this publication may be quoted if credit is given. It is recommended that reference to this publication be made in the following form:

Scott, J. F. 1987: Uranium Occurrences of the Thunder Bny-Nipigon-Marathon Area; Ontario Geological Survey, Open File Report 5634, 158p., 11 figures, 12 tables, 13 photos. 11 maps in text, and 1 map in back pocket.

Ministry of Northern Development and Mines Ontario Ontario Geological Survey

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Ministry of Northern Development and Mines Box bOOU 4 35 James Street South Thunder Bay

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V.G. Milne, Director Ontario Geological Survey FOREWORD

Uranium exploration in the Thunder Bay - Nipigon area reached its peak in the late 1970's and early 1980's, when numerous known occurrences were re-evaluated and Just as many new occurrences were found. The exploration models or concepts used at this time were based on the Athabasca or unconformity-related model, because the rock types and mineral deposits associated v.ith metasedimentary rocks of the Sibley Group in the Thunder Bay - Nipigon area paralleled the Athabasca area in time, rock types and mineral deposit types.

This report summarizes and compares the geology of the northern Saskatchewan and Thunder Bay - Nipigon areas, and describes the uranium occurrences in the latter area, including those known prior to, and those found at, the turn of the decade. New areas of search in the Thunder Bay - Nipigon area are suggested, based on a modification of the Athabasca model.

V.G. Milne

Director, Ontario Geological Survey ABSTRACT

During the 1981, 1982 and 1983 field seasons an inventory of all known uranium occurrences in the North Central Region was undertaken. Three major categories of uranium occurrences were identified: uranium associated with the rocks of the Quetico Subprovince; uranium associated with the Proterozoic/ Archean unconformity; and uranium associated with alkalic and carbonatite rocks of Late Precambrian age.

Occurrences associated with the Quetico Belt are in white, albite-quartz-muscovite pegmatites. Occurrences associated with the Proterozoic/Archean unconformity are usually of high grade (up to 12% l^Og), nearly always hematized and are related to fault or shear zones proximal to the unconformity. Although of high grade,"many of-the unconformity related occurrences are very narrow (<1 m). Alkalic and carbonatite rocks of Late Precambrian age are an important source of uranium but possible metallurgical problems might downgrade their potential.

The Quetico Subprovince is anomalously high in background uranium, and therefore contains important source rocks for uranium. Areas that have the highest potential for uranium deposits in the North Central Region should meet the following criteria:

1. Be located relatively close to source areas. 2. Have abundant structural and/or chemical traps to enable the uranium to be deposited. These traps could be a) fault zones; b) lithology pinchouts at basin margins; vll/vfii c) graphitic zones; d) concentrations of organically derived matter such as hydrocarbons, algal mats, etc.

3. Presence of a suitable plumbing system to convey the.'

pregnant solutions to the deposition sites. 4. Deposition of cover rocks to protect the deposits from erosion and at the same time provide processes of uranium enrichment.

5. Rocks have to be of an age when uranium was actively being transported in solution.

Two areas in the North Central Region that meet these requirements are the Nipigon Basin area, and the areas underlain by the Gunflint and Rove Formations. All the high grade vein-type uranium deposits related to the unconformity are found within the Nipigon Basin. TABLE OF CONTENTS Foreword V. Abstract V/'i List of Figures *"' List of Tables Xv/ List of Maps Xv/ii List of Photographs ^fy Acknowledgements Location Map Introduction Geology of the Nipigon Basin l Early Precambrian Middle Precambrian Late Precambrian Tectonic Framework Sibley Group Depositional History General Geology of the Athabasca Region 9 Comparison of the Nipigon and Athabasca Basins <> Regolith Development in the Nipigon Basin '7 The Proterozoic/Archean Unconformity Uranium Exploration History 37 Uranium Deposit Types 41 Genesis of Uranium Deposits - Nipigon Basin L(Q Exploration Guidelines • ^ Property Descriptions fe>3 Greenwich Lake Area - Christianson Occurrence 69 Innes Lake-Goodmorning Lakes Area 63 Enterprise Mine % Dorion Amethyst Mine |0^ Black Sturgeon Lake-Split Rapids Dam Occurrence (°7 Jessie Lake Area - Purdom Township "7 Prairie Lake Carbonatite Complex &~ McKellar Creek Diatreme I3( Deadhorse Creek Diatreme I3U- Port Coldwell Alkalic Complex "fl Miscellaneous Pegmatite Occurrences *•*• Lake Helen Occurrence 142. Howard Lake Occurrence (NTS 52B14/SW) I«f3 Beavercross Lake Occurrence (42E ) . H3 Tessier-Williamson Occurrence (52A15/NE) /V3 Tennant Lake Occurrence (42L11/NE) IM^ Conwest Occurrence tq^ Herrick Showing ^ Chimo Gold Mines Limited i^~ Sandy-Stone Lake Exploration and Development Company /«& References /J7 LIST OF FIGURES Figure 1 Proterozoic Stratigraphy of the Thunder Bay'Area 3 Figure 2 Composite Stratigraphic Column - Sibley Group Figure 3 Uranium Exploration History Figure 4 The Uranium Cycle and Asthenopheric, Hydrospheric, Atmospheric and Biospheric 52 Evolution Figure 5 Prospecting for paleosurface related uranium deposits Figure 6 Exploration methods used in the Nipigon Basin Figure 7 Conceptual relationships between uranium 82 deposit types in the Greenwich Lake area Figure 8 Alteration vs distance from the breccia zone 9o Goodmorning Lakes Fault Figure 9 Schematic section through the Goodmorning Lakes Fault Zone Figure 10 Geological crossection along CNR at the (Of Enterprise Mine, North View Figure 11 Autoradiograph of radioactive veins from Split Rapids Dam Occurrence LIST OF TABLES Table 1 Comparison of Uranium Deposit Characteristic 12- from Northern Saskatchewan and Nipigon Basin Table 2 Athabasca Basin vs Nipigon Basin 13 Table 3 Weathered Basement Rock, Asarco Drill Hole WR-1 22 Table 4 Weathered Basement Rock, Asarco Drill Hole WR-2 23 Table 5 Exploration History, Greenwich Lake Area 7^ Table 6 Uranium Analyses, Greenwich Lake Area 7£> Table 7 Analyses of Grab Samples from the Goodmorning Lakes Fault Breccia i5 Table 8 Analyses from Enterprise Mine 102. Table 9 Analyses from Split Rapids Dam Occurrence, lit Black Sturgeon Lake Table 10 Average spectrometer readings for Lithological __ Units, McKellar Diatreme l^ Table 11 Deadhorse Creek Diatreme Analysis |S4 Table 12 Selected Spectrometer Readings - High Grade 138 Showing at West Deadhorse Creek Subcomplex

xv/XV i LIST OF MAPS Map 1 Regional Geology and Uranium Occurrence Location - Nipigon Basin Area bade poctaat Map 2 Helikian Paleogeography 19 Map 3 Iron Occurrences- Black Sturgeon Lake Area (Coleman, 1909) 27 Map 4 Relationships of faults and lineaments to mineralization in an area approximately 30 km (oO around Greenwich Lake Map 5 Geology of the Christianson Occurrence, Greenwich "JO Lake Map 6 Uranium Occurrences - Greenwich Lake Area 8O Map 7 Geology of the Goodmorning Lakes Fault Breccia 85 Map 8 Western Dorion Township £& Map 9 Geology of the borion Amethyst Mine (OS" Map 10 Geology of the Split Rapids Dam Occurrence, Black Sturgeon Lake Area l^i Map 11 Uranium Occurrences in the Jessie Lake Area, II8 Purdom Township Map 12 Geology of the Jessie Lake Occurrence, East (2.0 Bay, Jessie Lake

XVII LIST OF PHOTOGRAPHS Photograph 1 CNR Pass Lake Quarry Photograph 2 a. Sibley Group - Archean unconformity near Gurney on Highway 17 east of Nipigon b. Close-up of weathered granitic basement. Note carbonate and quartz veining of the exfoliated granitic block boundaries Photograph 3 Sibley Group (Pass Lake Formation) overlying Archean quartz-monzonite at the Enterprise Mine, Lot C, McTavish Township Photograph 4 a. Handsample English Bay Porphyry West Shore, Lake Nipigon at English Bay. Note sub-circular hematite/chlorite rings b. Thinsection: Disaggregated and rafted feldspar and rock fragments in a hematitic and chloritic ground mass is indicative of weathering. Field of view approximately 2 mm Photograph 5 Reduction (non-oxidation) spots - Rossport Formation - sibley Group near Gurney, 28 Highway 17 west of Nipigon Photograph 6 Mudball Tuff Unit, Gunflint Formation, cut parallel to bedding. Note anthraxolite veining

Photograph 7 Pyrite breccia, Christianson Occurrence, Greenwich Lake 77 Photograph 8 Radioactive hematitic float, Greenwich Lake Area. Float assayed 2.4% U3O8. 77 Photograph 9 Quartz-hematite breccia, Goodmorning Lakes Fault Zone, SWs of W%, Lot 9, Cone. XI, 87 Dorion Township Photograph 10 Radioactive, myrmekitic reddish-brown pegmatite - Split Rapids Dam Occurrence 112.

Photograph 11 Colloform pitchblende at photograph center. Circle diameter approximately 12 mm

Photograph 12 a. Jessie Lake Occurrence b. Handsample from Jessie Lake Occurrence 122. Photograph 13 Radiating fracture patterns around radioactive minerals, Deadhorse Creek West Sub-complex Acknowledgements The author wishes to acknowledge the efforts of Dr. M. E. Cherry and Mr. J. A. Robertson for editing the final manuscript and A. R. Oowton for the excellent job of typing. Discussions both in the field and in the office were held with Dr. V. Ruzicka (Geological Survey of Canada), Dr. H. Quarch (Saarberg- Interplan), Y. Gariepy (Uranerz Exploration and Mining Corporation Limited). J. K. Mason and B. R. Schnieders provided stimulating discussions on the subject. Thanks also go to K. G. Fenwick for initiating the project and supporting it to completion. g-L-J-.-gl^.-gy--- _ >-**^g=

Location Map

XXII URANIUM OCCURRENCES OP TEE THUNDER BAY-NIPIGON-MARATHON AREA ONTARIO MINISTRY OF NORTHERN DEVELOPMENT IJSD MINES NORTH CENTRAL REGION

by

JOHN P. SCOTT*

•Geologist North Central Region Ontario Ministry of Northern Development and Mines Thunder Bay, Ontario

Manuscript approved for publication by A.C. Colvine, Section Chief, Mineral Deposits Section, Ontario Geological Survey, Toronto. This report is published by permission of V.G. Milne, Director, Ontario Geological Survey. XXI if 1 Introduction The purpose of this report is to describe, the known uranium occurrences in the North Central Region with particular emphasis on those in the Nipigon Basin (Map 1). The Thunder Bay-Nipigon area geology wiil be compared to that of the Athabasca Basin in Northern Saskatchewan as they are similar in age, lithologies and uranium occurrences. Important differences will also be noted.

A genetic model for uranium deposits in the study area will be proposed and used to recommend areas for future uranium exploration.

The study area is located in the North Central Region of the Ontario Ministry of Natural Resources and is centred in the Nipigon-Lake Nipigon area (Map 1). Ideas, concepts and data presented in this report are current to 1984. Unless noted, all analyses are by the Ontario Geological Survey Geoscience Laboratory, Toronto.

General Geology of the Nipigon Basin The geology of the Nipigon Basin has been described by Cheadle (1981), Coates (1972), Hawley (1929), Franklin (1970, 1978), Franklin and Mitchell (1977), Franklin et al (1982), Mcllwaine (1971, 1972), Mcllwaine and Tihor (1975 a, b), Tanton (1931), Wilson (1910), Tihor (1973), and Card et al (1972).

The following description of the regional geology of the Nipigon Basin has been summarized from this literature. Early Precambrian (Archean) The Early Precambrian rocks that underlie the Nipigon Basin are part of the Superior Province as defined by Stockwell (1962). The southern part of the basin is underlain by the metavolcanic and associated rocks of the Shebandowan- Wawa portion of the Abitibi Belt. The middle sector is underlain by the Quetico Belt, an eastrnortheasterly-trending, large, anticlinal or domal structure, containing deformed, highly metamorphosed metasedimentary rocks on the limbs of a central core of trondhjemite, migmatite and pegmatite. The metasedimentary components are highly folded (Kehlenbeck 1976) and consist of arenaceous to argillaceous rocks with turbidite-type structures. Albitic pegmatite bodies and massive, lensoid quartz monzonite sills occur throughout the belt. The Wabigobn Metavolcanic Belt underlies the Nipigon Basin north of the Quetico Belt. The English River Belt underlies the northern edge of the Nipigon Basin in the study area.

Middle Precambrian (Aphebian) In the Nipigon Basin all rocks younger than Early Precambrian are in the Southern Province of the Canadian Shield (Stockwell 1962) and form the Nipigon Plate and the Port Arthur Homocline. The Gunflint and Rove Formations overlie the Early Precambrian basement in southern sections of the Nipigon Basin. The Gunflint Formation consists of taconite, algal stromatolites, chert-carbonate and argillite. Although several isotopic age studies of the Gunflint Formation have been carried out, none has satisfactorily established the time of deposition. Studies by Hurley et al. (1962), Faure and Kovach (1969), Misra and Faure (1970), Hanson and Malhotra (1971) and Franklin (197G) suggest a minimum age of 2,000 my. PROTEROZOIC STRATIGRAPHY OF THE THUNDER BAY-NIPIGON AREA

GROUP AND FORMATION LITHOLOGIES MINERAL COMMODITY A6ES

OSLER GROUP Tholiiitic basalls,minor rhyollle and stdimenlary rocks,botal elastic unit Cu, Ag, agat* 955-HO my (Van ScJumi* « c\ (I960) >

LOGAN DIABASE, GABBRO.PERIDOTITE Cu.Ni.Pl.Pd 1150-1250 my (Van Schmu. «l 01(1960)1

SIBLEY GROUP \ Kama Hill Formation Clay and K-feldspar rich mudslone, abundant reduction spheres, mudcracks, salfcam ripple mark*

Pb.Zn, bonle. omtthyii, U 1339 my Rossport Formation Dolomite, arenaceous dolomite, chert, stromatolites (Franklin et.al (1982))

Pass Lakt Formotion Quartz artnite, basal conglomerate

AN1MIKIE GROUP Ftisic igneous activity, Lake Nipigon area 1536 my (Sulcliffi. OGS. pirmnal communccolion (1962))

Rov* Formohon Black pyritic •hole, argilliu.quartzitic grtywockt Ag.Zn.Pb, tioril. 1700 my (Fronklm(IS78b)l

Gunflmt Formation Minor botolt.tuff; conglomiratt, algal chert, siliceous taconttt, ferruginous and ft, Ag,U, omethytt -2000 my dolomitic chert-carbonatic, thai* (Floran and Papike (19751)

ARCHEAN Au,Ag,Cu,Zn,Nl,F«, ttc and ffligmatiUt

Figure 1. Proterozoic Stratigraphy of the Thunder Bay-Nipigon Area. The Rove Formation consists of greywacke and black shale (Morey 1969), and overlies the Gunflint Formation with a slight unconformity (Moorhouse 1960). Loth formations are relatively undeformed and unmetamorphosed and generally dip toward Lake Superior at shallow angles. The Gunflint Formation was deposited in a paralic basin, whereas the Rove Formation was deposited in an anaerobic basin (Franklin 1970).

Late Precambrian (Helikian) The Late Precambrian Sibley Group and Osier Group rocks lie unconformably on Early Precambrian rocks and, in some instances, on Middle Precambrian rocks (Photograph 1) throughout much of the Nipigon Basin. Numerous Late Precambrian intrusive rocks occur throughout the succession and include Logan sills, gabbroic intrusions such as the Crystal Lake gabbro in Pardee Township and alkalic/carbonatite complexes such as the Port Coldwell Complex and the Prairie Lake Complex, located to the east of the Nipigon Basin.

The Sibley Group has been dated at 1339 ± 31 my (Franklin et al.1982); the Osier Group is 1150-1220 my old and forms the lower part of the Keweenawan Supergroup (Franklin 1978). The Sibley Group has been subdivided into the Pass Lake Formation, Rossport Formation and the Kama Hill Formation (Franklin et al. 1980). A composite stratigraphic section of the Sibley Group is shown in Figure 2. The Sibley Group was deposited in an elgonate, northerly to northwesterly-trending basin that generally is defined by the Nipigon Plate. Photograpn 1. CNR Pass LaKe Quarry: Pass Lake Formation overlying Rove Formation. Near the unconformity, the normally blackisn Rove Formation has been oxidized to a greenish- hued argillite. The thin conglomerate lens at the unconformity is oxidized.

Arrows mark fault trace. Columnar jointed sheet o( diabase overlies flblay Group at lasta 1111. •OK ihoni unit* of Slblay Group overlain by Oalar Group volcanic racks.

4t a of rad to purpla ahala and ailtatona containing abundant raduction aphar«a> aud crackat aalt casts, rippla Barks, aeddinq apparant in thin aaction or alabbad surfaces. Deposited in a pariodically dry Mid tlatt lack of abundant tidal features lndicata a lacuatrina or vary weakly tidal aud flat. Periodic ahaat flooding, poaaibly accompanied by flood-induced submergence account (or aost of the sedimentary atructuraa. Paw atroaatolitic bada occur in basal portion! of thia formation, Lower bada hava up to lot raduction apharaa.

Boundary between kossport Poraation and Kaaa Bill Formation - tranaitional and Barked by tha diaappaaranea of carbon*tr and a color chang* frcm red to purpla, incraaaa in fina claatic iiatarial.

37 a aaaaiva rad dolomite and aranacaoua dolomite. Contain* white ion** that eoapriae 20% of the rock and fora irregular fl«aa-like pattarna. No diatinctiva aranita bada. Op to 5% reduction apheraa.

2 a central acabar coapoaad of alternating laainae ot black chert, gray chart, buff calcita. Laainae tre 0.5-1 ca thick. Resemble elongate or flattened stromatolite mound* or algal mats. At Kama Bill black anthraxolitic carbonate emit a foetid, sulphurous odor •hen acratched, probably reflecting an organic origin, northern aectora of the baain thia unit contain* stromatolites 'Conopnyton cf. C.gaiganicu.," .Jofaann, 19*9).

9t a of veil bedderi red doloaite and arenaceous dolomite intercalated with buff to white arenitc beds. Tan colored reduction spots are common in the red units. Several styles of soft sediment deformation present. Graded beds are generally absent. Often cut by breccia zones up to 40 m in width, zones composed of eha. -ic dolomite breccia, cut by aandatonc dikes and sills up to 1 a wide. Blocks ot Pass Lake Poraation, Rossport Formation, and sometimes Rama Bill formation incorporated in the breccia. Sec Franklin ct at (19801 for complete description!:.

, 1 m red conglomerate riisconformably on arcnite of Pass Idte Formation 7 a of thickly bedded bulf ar'Oite with 5t white chert groins.

1 a dolo*itic sandstone. 10 m buff arcnite: locally displays a patchy red coloration.

1 m thick member composed of thin bedded red dolomite and dolomitic -arenite. 13 m thick sequence of buff arcnite.

'1 a thick bed of red, dolomuUc arenitc.

.Buff arenitc displaying an upward thinning of bedding from 1 • near base- to 1-2 cm at the top. Total thickness of this sequence is 20 a.

IS m of lcnsoid conglomerate basal to Pass Ldke Formation, clast • litholoqics doainatcd by granitoids and Gunflint Formation cherts and tacomtc set in a brick red sandy matrix.

Uanemcnt conmsts o( Karly Precambrian granitoids and Hiddlv . Precambrian Rove Formation. The Rove Formation is oxidized for below the contact with thr Pass idkv Purmation. Calcareous concretions abundant.

Figure 2 Composite Stratigraphic Column Sibley Group The Osier Group is exposed on Black Bay Peninsula and St. Ignace and adjacent islands in northwestern Lake Superior and consists of subaerial thoeliitic basalts, minor rhyolitic rocks and intercalated, locally derived, sedimentary rocks (Mcllwaine and Wallace 1976, Giguere 1975, Wallace 1972).

TECTONIC FRAMEWORK Wallace (1981), Card et al. (1972), and Craddock (1972) among others have discussed the Keweenawan system as a paleorift similar to the present-day rift systems of Iceland and East Africa. The concept was first put forward by King and Zietz (1971)-and White (1966), who noticed similarities between the en echelon linear segments of the Keweenawan belt and the present-day spreading rift systems with offsets along transform faults. Geoscientists such as Hinze et al. (1971), Hinze and Merrit (1969), Craddock et al. (1963), Coons et al. (1967), Bayley and Muehlberger (1968), and others generated the necessary geological and geophysical studies that were collectively able to trace the Keweenawan system from the Lake Superior area into Kansas, 1,200 km to the southwest.

Burke and Dewey (1973) proposed that the segments of Keweenawan rocks that extend southwesterly from Duluth, Minnesota, and southeasterly through Sault Ste. Marie, Ontario, are rift arms of a plume-generated triple junction in which the north arm had failed to develop. This "rrr" triple junction was believed to have been centred in northeastern Lake Superior, and the Kapuskasing structure is the failed arm. Burke and Dewey (1973) postulate that the failed arm of the Keweenawan triple junction reactivated a pre-existing zone of weakness, hence explaining the two ages of carbonatite and alkaiic intrusions along the Kapuskasing structure. .'

Burke and Dewey (1973) also suggest that these plume-generated "rrr" junctions occur in bends of continental margins. Franklin et al. (1980) suggested a variation of the scenario by proposing that a failed arm could be located at the fault-bounded trough that strikes north-northwest from Nipigon, Ontario. This "rrr" junction would occur at the site where the mid-continent gravity high has a sudden strike change. This graben served as a channel for the northward transgressive seas in which the Sibley Group sedimenr.s were deposited. The production of the Logan sills in the Nipigon and Thunder Bay area has also been linked to the formation of this failed arm (Sutcliffe 1981).

SIBLEY GROUP DEPOSITIONAL HISTORY (adapted from Franklin et al. 1980). The Sibley Group was deposited in a north-south fault block or failed arm. The basin was initially deepest in the south and developed rapidly with conglomerate fans forming near the basin margins. This initial period of rapid deposition was followed by the slower deposition of the Pass Lake Formation sandstones. The basin transgressed northward toward the end of the period of the deposition of the Pass Lake Formation and extended as far north as southwestern Lake Nipigon during the deposition of the lower member of the Rossport Formation. The middle stage of Rossport deposition was marked by rapid regression, accompanied by increased clastic deposition and stromatolite growth north of Mpigon and the precipitation of chert to the south. Transgression followed and the basin eventually extended as far north as the Armstrong area, north of Lake Nipigon. The depth of the basin was relatively constant and it slowly filled with clay-rich dolomite. The transition to the Kama Hill Formation marks a change from predominantly subaqueous to predominantly subaerial deposition in a mud flat type of environment (Franklin et al. 1980).

Sutcliffe and Greenwood (1982) report the existence of Middle Precambrian, felsic, subvolcanic and volcanic rocks within the Nipigon Plate. These rocks include debris flow and ash flow deposits. A quartz-feldspar porphyry, located at English Bay on Lake Nipigon's west shore- is considered to represent the centre of felsic volcanism. • This porphyritic granitic stock has been dated by U-Pb method at 1536 ± 4 my (R. H. Sutcliffe, Geologist, Ontario Geological Survey, persona' communication, 1982).

GENERAL GEOLOGY OF THE ATHABASCA REGION The regional geology of Northern Saskatchewan has been described by many workers. The reader is referred to Alcock (1936), Beck (1969), Fahrig (1961), Hoeve and Sibbald (1978), Lewry and Sibbald (1978), Money et al. (1970), Ramaekers (1981), Ramaekers and Dunn (1977), Ramaekers and Hartling (1978), Sibbard et al. (1976), Stockwell (1962), Tapaninen lo

(1976), Tremblay (1972, 1978, 1982, 1983), Tyrrell (1896) and Dahlkamp and Adams (1981).

The following summary is taken from Dahlkamp and Adams (1981): "The Athabasca region is part of the Churchill structural province of the Canadian Shield as defined by Stockwell (1962). It comprises Archean basement of predominantly granitic rocks and some greenstone belts. They were affected by the Kenoran orogeny at about 2,500 million years. (Wanless et al, 1966). The Archean basement forms northeast-southwest elongated troughs which are filled with Aphebian (middle to upper Lower Proterozoic, older than 1,800 million years) sediments and volcanics. The Hudsonian orogeny (about 1,700 to 1,800 million years) metamorphosed and folded all these rocks creating northeast to southwest- trending mobile belts. Such belts contain the Tazin metasediments of the Beaverlodge district to the west, the Wollaston Fold Belt along the eastern margin of the Athabasca Basin, and the Virgin River Fold Belt in between.

During the waning stages of the Hudsonian orogeny, in the region north of Lake Athabasca, the Martin Formation, composed of continental sediments (conglomerates, arkoses, siltstones, etc.) and intercalated volcanics (basaltic and andesitic lavas, gabbroic sills; age: 1630 ± 1800 million years; Wanless et al, (1966), was deposited immediately on the Hudsonian crystalline basement apparently without the intervening development of a weathering (regolith) horizon. The Martin sediments were slightly folded by Late Hudsonian movements producing fold axes that strike northeast to southwest, approximately parallel to those of the subjacent metasediments. Diabase dikes (1,490 million years; Wanless et al, 1566) cut the Martin Formation. Based on geologic position and age dates for the volcanics, the Martin Formation must have been deposited between 1490 and 1740 million years. To the south of Lake Athabasca, a longer period of weathering produced a deep chemical alteration of the metasediments forming a saprolite (referred to as a regolith in Canada). Subsequently, the Athabasca Formation was deposited over the older rocks and the regolith. The Athabasca Formation is comprised of continental sandstones with some conglomerates and argillaceous intercalations. Diabase dikes dated at l>230 million years (Burwash et al, 1982) cut the sediments. The age of the Athabasca Formation is given as 1,350 ± 50 million years by Ramaekers and Dunn (1977). Near Cluff Lake, the Athabasca Formation is overlain, by siltstone of the Douglas Formation and' dolomites of the Carswe.ll Formation. According to Tapaninen (1976), the Athabasca depositional basin is divided into southwest- trending zones by horst and graben structures. The controversial Carswell circular structure is located in the west-central part of the basin. Within the structure, which has a diameter of about 40 km, crystalline basement is found lying overturned on Athabasca sandstone. The origin of the structure is still uncertain, but one theory considers it to be the result of a meteroric impact. The age of the event is dated at 470 million years. Finally, glacial deposits of variable thickness cover wide areas of Northern Saskatchewan and create a major obstacle to exploration."

COMPARISON OF THE NIPIGON AND ATHABASCA BASIN When this study was initiated in 1981, it was thought that a comparison should be made to document the similarities and the differences between the Nipigon Basin and the Athabasca Basin, which contains major uranium deposits. Franklin (1978) described some uranium mineralization in the Nipigon Basin and listed parameters that characterized the uranium potential of the area.

Table 1 compares the uranium occurrences of Northern Saskatchewan with those of the Thunder Bay-Nipigon area. The similarities are striking. Table 2 illustrates regional geological comparisons and notes some important differences - namely in size and configuration of the Middle Precambrian TABLE 1. ATHABASCA BASIN - NIPIGON BASIN COMPARISONS

Northern Saskatchewan

Beaverlodge-Type (Tremblay, 1972, 1978)

1. Not stratigraphically confined to Martin unconformity.

2. Related to major faults or wide mylonite zones and to zones of closely spaced fractures superimposed on mylonite zones.

3. Mineralization is along fractures and disseminated in wall-ricks.

4. Related to a specific lithologic succession at a definite stratigraphic level in Tazin rocks.

5. Related to areas intensely granitized and widely retrograded to greenschist facies.

6. Associated with areas intensely altered with red hematite, dark green chlorite and white carbonate; some silicification, rare argillization.

7. Mechanical ietritus along unconformity is thin near ore and distribution is erratic.

8. Large horizontal and vertical extent of ore zones.

9. Pitchblende, minor secondary uranium minerals, rare brannerite.

10. General simply mineralogy, locally complex.

11. Cu, V, Se and Ti: in variable amounts and of erratic distributions; crude zoning locally.

12. Age of mineralization: 1780 +, 20 m.y, 1140 +_ 50 m.y. and several remobilization periods.

13. Temperature of formation: 440 C to 80 C.

14. Age of host rocks: mainly Archean; locally Aphebian and Helikian. 13

TABLE 1. ATHABASCA BASIN - NIPIGON BASIN COMPARISONS (coot)

Northern Saskatchewan

Unconformity-Type (Trenblay, 1978)

1. Stratigraphically confined to Athabasca unconformity.

2. Related to faults in both basement and Athabasca sandstones; faults are old with late movements.

3. Mineralization is along faults and disseminated in wall-rocks it is entirely either in basement or in Athabasca sandstone; locally it is in both.

4. Not restricted stratigraphically but associated in basement with graphite, calcsilicate and amphibole-bearing rocks.

5. Not related to granitization.

6. Associated with clay-white altered regolithic areas in basement and with late green chloritic and sericitic areas in basement and sand- stone.

7. Maximum development of regolith at unconformity; widespread chemical alteration.

8. Large horizontal but 1rttle vertical extent of ore zones.

9. Pitchblende, coffinite and locally abundant secondary uranium minerals; sooty.

10. Simple and complex mineralogy.

11. Cu, Ni, Se, As, Au, Ag and/or Te; in variable amounts and of erratic distribution; crude zoning locally.

12. Age o£ mineralization: 1200 m.y., with remobilization periods.

13. Temperature of formation: 260 C to 60 C.

14. Age of host rocks: mainly Aphebian and Helikian, locally Archean. TABLE 1. ATHABASCA BASIN - NIPIGON BASIN COMPARISONS (Cor\t)

Nipigon Basin ' ' (Fenwick & Scott, 1977) (Franklin, 1978)

1. Presence of ore-grade uranium mineralization in some Pb-Zn veins; close spatial relationship of these veins to Sibley Group/Archean unconformity.

2. Extensive well developed rift-fault system. Uranium associated with faults that have acted as loci for mineral trapment.

3. Non-pegmatitic uranium mineralization associated with faults breccia zones in Rossport Formation (Dorion Amethyst Mine).

4. Uranium enriched source rocks - Quetico Belt Metasediments & Granitoids.

5. Suggestions of locally developed regolith at unconformity between Sibley Group and Archean rocks; Nblfpup Lake drilling; zone at Dorion Amethyst Mine; altered feldspars at Enterprise Mine basement rocks. Highway 17 near Gurney; deeply weathered mafic intrusives in Black Sturyeon Area; metasediments near Split Rapids Dam area; deeply, weathered granitoids near Frazer Lake.

6. Hematization prevalent at most localities of uranium occurrences.

7. Pitchblende, coffinite and secondary uranium minerals widespread at showings.

8. No mineralogical studies of uranium mineralization in the Basin done yet.

9. Age: non-pegmatitic occurrence thought to be Proterozoic. No specific age dates. 1.08 _+ 25 by (Ruzicka, 1984).

10. Host Rocks: Archean pegmatites; Middle & Late Precambrian sediments. High concentrations localized in some fault systems.

11. Temperature of formation - 110°C.

12. Other deposit types associated with: Late Precambrian diatremes, Prairie Lake Carbonatite; Port Coldwell Complex, Hemlo Area.

13. Deposit types: 1. Archean pegmatites of Quetico Belt. 2. Veins associated with faults cutting Sibley Group. 3. Pb-Zn veins associated with Sibley Group/ Archean unconformity. 4. Fault systems near unconformity in Quartz monzonite intrusives. 5. Diatrames, alkalic intrusives, carbonatites. 6. Mudball Tuff unit, Gunflint Formation. TABLE 2. Differences - Athabasca Area And Sibley Basin Athabasca Basin Parameter Nipigon Basin 37,800 mi^ Basin Area of 16,000 mi^ - area of margins plus the highest U Quetico Belt-Sibley Group Wollaston Domain/ potential overlap Athabasca Basin overlap Severely deformed, Middle - nearly flat-lying, folded with basement Precambrian unmetamorphosed - consists granitoids during Rocks of: Hudsonian orogeny 1. Gunflint Formation consists of: - taconite, argillite, pelitic and graphitic chert-carbonates, metasediments stromatolites, tuffs, algal mats 2. Rove Formation - shale, greywacke

Athabasca Formation Late 1. Sibley Group - sandstone Precambrian - sandstone Rocks - carbonate - chert - stromatolites - mudstones 2. Logan diabase sheets 3. Osier Group - subaerial basalts - rhyolites - interflow sediments Diabase dikes 1230 my Age Osier .Group 1100 my Athabasca Sandstone Diabase Sheets 1100-1250 my 1350 + 50 my Sibley Group 1339 my Middle Precambrian Rove Formation 1700 my Rocks 1800 my + Gunflint Formation 2000 my Martin Fm 1630 ± 180 my Tazin pre-1940 my Athabasca Sandstone Thickness Osier Group 2700 m 1500 m Sibley Group 235 + m Rove Formation 975 m Gunflint Fm 165 + m SW to EW troughs Basin Shape NE Variable: Age of Uranium Black Sturgeon 1.08 ± 25 by 1200 my )with Mineralization 1780+20 )remobili- 1140150 )zation lithologies. In the Athabasca area, Middle Precambrian rocks older than 1800 my consist of sediments and volcanic rocks that filled pre-existing basement topographic lows and then were infolded with the Archean rocks and metamorphosed during the Hudsonian Orogeny (1700 my - 1800 my). This metamorphosed package of rocks was subjected to a period of weathering, producing a regolith that was in turn covered by the Athabasca Formation in the area south of Lake Athabasca.

In the Thunder Bay-Nipigon area, Lower Proterozoic rocks (Gunflint and Rove Formations) were deposited on an already weathered Archean surface. The Sibley Group was deposited with slight disconformity on the Rove Formation. At Pass Lake, the black shale of the Rove Formation has been oxidized up to 5 m below the contact (Franklin et al. 1980).

Apart from regional faulting, no major orogenic event, such as the Hudsonian Orogeny in northern Saskatchewan, has affected the Proterozoic rocks in the Thunder Bay-Nipigon area. They are still essentially unmetamorphosed and generally flat-lying, exhibiting shallow (<5-10°) dips to the south.

The implications are obvious: a major step in the uranium enrichment process that took place in the Athabasca Basin, the release of uranium from Lower Proterozoic source rocks coupled with the formation of the meta-pelites and graphitic rocks during metamorphism, did not occur in the Nipigon Basin. This is the major difference between the two areas and will put constraints on finding an Athabasca-class uranium deposit in the Nipigon Basin. n

REGOLITH DEVELOPMENT • In this report the term "regolith" will be restricted to mean a buried weathered surface or soil horizon of the geological past. It may or may not be exhumed.

Macdonald (1980) studied the mineralogy and geochemistry of the regolith in the Athabasca Basin and stated that the chemical and mineralogical characteristics of the Athabasca regolith closely resemble the recent lateritic profiles in the tropical and subtropical climates of today.

The presence of a regolith is an important criteria in the deposition of uranium in the Athabasca area as well as in Australia (Dahlkamp and Adams (1981), MacOonald (1980), Ojakangas (1978), Tremblay (1983)). Almost every major uranium deposit in the Athabasca Basin is best developed in the regolithic zone situated at the base of the Athabasca Formation. The development of a regolith liberated uranium from host rocks. This weathered zone then acted as a conduit to move the uranium to its deposition sites at structural- chemical traps. The presence of a regolith appears to be a major prerequisite for the development of uranium deposits of this type.

The following description of the regolith in the Key Lake area of Saskatchewan is taken from de Carle (1981).

During the weathering process there is a gradational change in mineralogy and rock textures that decreases with depth. Regolithic profiles are characterized by chloritization of the ferromagnesium minerals, sericitization and/or illitization of the K-feldspars and the saussuritization of plagioclase. A mineralogical zonation is present in the regolith in the Athabasca region and it is distinguished by kaolinite plus hematite in the upper sections, with illite plus chlorite in the deeper sectors. These zones may or may not be present as their formation depends on variables such as grain size, faulting and bedrock topography.

The contact between these zones within the regolith, as well as the contact between the regolith and the unweathered rock, is gradational. Chemical changes associated with the paleoweathering include a relative increase in AI2O3, H2O, Pe203» TiO2, and P2O5 and the depletion of CaO, MgO and K2O; S1O2, MnO and Na20 are relatively immobile. These regolith changes are indicative of development under semi-tropical and semi-arid conditions.

Map 3 shows the Helikian paleogeography and the location of the Sibley Group with respect to other Late Precambrian basins, including the Athabasca. This location is consistent with the depositional environment in which the Sibley Group was deposited. The depositional history of the Sibley Group has been described by Franklin et al. (1980).

The presence of evaporite minerals such as halite and gypsum in the Sibley Group is evidence of deposition in a hot, arid, lagoonal environment compatible with the Helikian paleogeography. Regolith development in the Athabasca area was initiated at 1633 + 30 (Fahrig et al. 1978) or o 30

30

Htllklan Latitude* AthtMtct formtUom

Mow Quartilta

15 Slblay droop Pre*«nt North Polt

0

•aylan tmt CMke ntTSi ModHlad from FtlH|g ^^ J-w, nNt| Hamaakara mt DWM I1»T»)

Map 2. Helikian Paleogeography 1710 ± 20 (Voultsidis et al. 1980) million years ago, based on Rb/Sr and K/Ar geochronology. The two dating methods used could give different ages for unite formed at the same time, and does not necessarily imply two ages of regolithic development.

Altered and weathered basement is present beneath the Sibley Group and probably is more extensive than initially interpreted. Gill (1924) and Moorhouse (1960) are of the opinion that a paleosol was developed on the pre-Sibley Group rocks, but, because of the transgressive nature of the basin, any existing regolith may have been removed, or at least reworked, by the advancing beach line. The regolith would be preserved in areas of rapid infilling, such as valleys and downfaulted blocks.

In 1980, Asarco Exploration of Canada Company Limited drilled two diamond drill holes near Wolfpup Lake (52A 15/NE) in the Black Sturgeon River area, approximately 80 km northeast of Thunder Bay. Both holes were drilled through Sibley Group rocks into basement and in each case, the granitic gneisses and migmatites at the bottom of the. holes are severely altered. Weathered basement detritus was first logged in hole WR-1 at 517 feet. At the unconformity, even though the Sibley Group sandstone appears reasonably fresh, the Archean basement shows features of severe weathering. The alteration is hematitic; most fractures and seams are coated with or contain hematitic mud. Feldspars are totally hematitized and the rock is very friable.

In 1980, the Asarco drill core was sampled and analysed by W. B. Coker, then with the Geological Survey of Canada. In the present study, these analyses of samples of basement rock immediately below the unconformity were compared with those of the last rock encountered in the hole. In hole WR-1, the samples were 47 feet apart; in hole WR-2, the samples were 30 feet apart.

In hole WR-1, the altered rock shows a relative decrease in SiC>2, AI2O3, Na20, K2O, BaO, Sr and Zr, while Fe203, MgO, CaO, H2O, TiO2» ^2^5 an<^ MnOf show a relative increase. Trace elements also exhibit a shift in concentration. Lead, mercury and sulfate show a relative decrease; zinc, copper, nickel, cobalt, vanadium and fluorine show a relative increase.

In hole WR-2, there is a relative decrease in SiO2, CaO, , MnO, coupled with a relative increase in AI2O3, , MgO, K2O, H2O, TiO2, P2°5' Ba0 and Zr- Differences in the trends between WR-1 and WR-2 probably reflect initial rock composition differences. This data is from only two sample pairs and much more sampling is required to establish meaningful trends that could be used for mineral exploration purposes.

The Sibley Group-Archean unconformity is exposed in two rockcuts on Highway 17 approximately 34 km east of Nipigon in the Gurney area. Here sandstone and mudstone of the Rossport Formation of the Si.bley Group lie unconformably on altered Archean granitic rocks. The alteration is characterized by a green and red blotchy appearance of the granite. Feldspars are altered by hematite and the TABLE 3. Weathered Basement Rocks Asarco Drilling - Black Sturgeon Area

Asarco Hole WR-1

Weathered Rock Least Weathered Sample 802077 I* Sample 802083 SiO2 63.61 - 0.48 63.92

A12O3 15.55 - 9.33 17.15

Fe203 5.21 +215.2 1.71 MgO 3.89 +463.8 0.69 CaO 0.28 + 12.0 0.25 Na20 0.34 - 81.4 1.83

K20 7.80 + 40.9 13.19

H20 2.39 +319.3 0.57

C02 N/A N/A

TiO2 0.55 +223.5 0.17

P20s 0.13 + 8.3 0.12 MnO 0.05 +150.0 0.02 BaO 0.19 - 42.4 0.33 Sr 0.001 - 94.1 0.017 2r 0.017 - 55.3 0.038

100.00 100.00 TABLE 4. Weathered Basement Rocks Asarco"5rilling - Black Sturgeon Area Asarco Hole WR-2 Weathered Rock Least Weathered Sample 802170 %a Sample 802175

SiO2 57.85 - 11.98 65.72

A12O3 16 .10 + 12.12 14.36

Fe203 8,.11 + 29.97 6.24 MgO 4..30 + 58.67 2.71 CaO 0..50 - 75.12 2.01

Na20 0..28 - 92.39 3.68

K20 8..71 +187.46 3.03

H20 3.,li +125.36 1.38

C02 N// N/A N/A

TiO2 0.62 + 3.33 0.60

P205 0.13 + 8.33 0.12 MnO 0.06 - 14.29 0.07 BaO 0.19 +280.00 0.05 Sr 0 Zr 0.03 99.99 mafic constituents are chloritized. The rock exhibits a blocky, exfoliation texture with carbonate and quartz veining developed between exfoliation blocks (Photograph 2).

In the Leckie Lake area (52H 2/SW) and in the south half of Hele Township (48°57', 88°27'), mafic to ultramafic intrusive rocks are deeply weathered. The soil profile exposed at these localities is more than 2 in thick. The weathering is a lateritic type and one can trace features such as carbonate and asbestiform veinlets from solid rock through the soil profile. The soil is enriched in nickel and cobalt. Samples of soil had 27 ppm Cu, 1,070 ppm Ni and 142 ppm Co, whereas the rock had 21 ppm Cu, 12 ppm Ni and 5 ppm Co. A regional Cu, Ni, Co anomaly exists over the site (Geological Survey of Canada Open Pile Report 746).

The unconformity is also well exposed at the Enterprise Mine, located in Lot C, McTavish Township (Photograph 3). Here sandstones of the Sibley Group overlie Archean quartz monzonite. The unconformity is exposed in the CNR railway cut near the north end of the exposure. The quartz monzonite exhibits feldspar alteration for at least 2 m beneath the unconformity (Campling 1973, Franklin 1978, and Franklin et al. 1980). The quartz monzonite has abnormally high radioactivity associated with it; samples of vein material taken from the Enterprise Mine yielded up to 1.2 lbs U30g/ton. The unconformity is also exposed at the Dorion Amethyst Mine property, as well as at the nearby Ontario Gem Company property. Photograph 2. (a) Sibley Group - Archean Unconformity at Gurney, Highway #17, east of Nipigon.

(b) Close-up photograph of weathered granitic basement. NOTE; Carbonate and quartz veining around the exfoliated granitic rocks. The Dorion Amethyst Mine is situated 2.5 km north-northeast of the Enterprise Mine and the Ontario Gem Company property is 3.4 km northeast of the Enterprise Mine. The reader is referred to the descriptions of these properties found elsewhere in this report for more geological information.

The Prairie Lake Complex (see description p. 125, this report) also exhibits a profound soil profile indicative of deep weathering, but rocks of this type tend to weather faster than others. At 22.5 km north of Highway 17 on the Deadhorse Crsek Road, an intensely kaolinized granitic rock is highly radioactive with levels exceeding 5 times background. This location appears to resemble regolithic development but the highly altered rock may represent alkalic metasomatism associated with the Prairie Lake Complex. Three samples were taken by the author and analyses by the Geoscience Laboratory gave the following results: Uranium Thorium Zirconium Beryllium Sample (U) (Th) (Zr) (Be) Niobium No. (ppm) (ppm) (ppm) (ppm) (Nb) F-150-79 37 40 2500 10 700 F-151-79 24 30 500 5 600 P-152-79 14 130 300 4 1000

Hematitic alteration and occurrences have been reported in the Black Sturgeon area by Coleman (1909) (Map 3, and in the McTavish Township area by Tanton (1931). The Black Sturgeon occurrences are associated with the Black Sturgeon Fault System and consist of massive to crystalline hematite present as specularite and as the red earthy variety. Hematite cements intensely weathered and brecciated Archean metavolcanic and granitic rocks, BLACK STURGEON LAKE LEGEND IRON DISTRICT TOCrr/£ Drift \ |

SOUC 1 HlLt'l liCU \Und,Mf i—j J Hon. F. m frttn Schitt | 2. ) TOACCOWAHY REPORT tr A PCOLEliAN IN THE I aw REPORT OF THE BVftE4U0F MINES I9O9

«Ke Br.)iH«f fcyJS .

Map 3 Iron Occurrences in the Black Sturgeon Lake Area Pnotograph j. Sibley Group (Pass Lake Formation) overlying Archean quartz-monzonite. Enterprise Mine, Lot C, McTavish Township. guart2 and chalcedony. Granitoid rocks exhibit intense sericitization of feldspars. Analysis of a sample of this hematite gave the following result: U: 800 ppm; Ni: 100 ppm; Co: 64 ppm; Au: 0.01 oz/ton; Ag: 0.10 oz/ton.

In the English Bay area on Lake Nipigon's west shore, an extensive system of hematitized fractures occurs at the contact between the English Bay porphyry and the overlying quartz sandstone and conglomerate of Late Precambrian age. The fracture system occurs in two modes. The most striking mode in plan view is a series of circular to elliptical closed loops ranging up to several metres across. Within the fracture sets, the loops are more or less concentric, with the smallest loop, near the centre, of the fracture set only a few centimetres across. The outcrop area contains an aggregate of such loops. The second mode of occurrence is a series of subparallel fractures crosscutting t*e outcrop. These are spaced several ten's of centimetres apart and are hematitized.

The rock is porphyritic, with large blocky feldspar crystals up to 7 mm long and euhedral quartz eyes up to 5 mm across set in a matrix composed of fine grained hematite and a greenish, felt-like material, probably a chloritic clay. In thin section the rock appears to be disaggregated, with feldspar crystals having feathered edges. The feldspar crystal edges are enveloped in a hematitic clay (Photograph 4) with rafted mineral fragments. The rock is composed of plagioclase, quartz, zircon, fluorite, amphibole and Photograph 4. English Bay Porphyry, west shore of Lake Nipigon, at English Bay.

A. Handsample Note; Sub-circular hematite/chlorite rings B. Thin section

Disaggregated and rafted feldspar and rock fragments in a nematitic and chloritic ground mass is indicative of weathering. Field of view approximately 2 mm. 3/

of plagioclase, quartz* zircon, fluorite, amphibole and alteration products of clay and hematite. The rock represents a re-lithified, weathered feldspar-quartz porphyry.

THE PROTEROZOIC/ARCHEAN UNCONFORMITY

The Proterozoic/Archean unconformity is exposed in numerous localities and in every case the underlying basement rocks show weathered features. Notable exposures are at the

Highway 588 bridge over the Whitefish River southwest of

Nolalu, a roadcut located between County Fair Plaza and

North Mclntyre on Highway 102, at Kakabeka Falls, and on the north shore of Lake Superior southwest of Schreiber.

Harcourt (1938) describes one such locality near Schreiber:

"Animikie sediments occur only in a few small outcrops along the shore of Lake Superior west of Schreiber. In these outcrops the sediments consist of a basal conglomerate, resting upon the weathered surface of Keewatin lavas and Algoman syenite. Above the conglomerate there is a thin layer of jasper and black chert overlain by black slates. The sediments dip 5° to 10°S.

Between the Keewatin pillow lavas and the conglomerate proper there is a thickness of some 3 to 6 feet of shaly material, which is not bedded. This material represents disintegrated pillow lava and soil developed on this surface. In cliff sections the various stages in the development of this soil may be observed. In the first stage, the margins of the pillows have been attacked by surface distintegration leaving the interior of the pillow still unaffected. As the alteration extends inward, what remains of the solid pillow resembles a boulder in glacial clay. In the final stage the pillow is completely disintegrated to a more or less homogeneous shaly material. On top of this soil rests the basal conglomerate composed of heterogeneous pebbles from 32.

1 to 2 inches in diameter. One of the best localities to see these relations is on the lake shore half a mile east of the small island south of Horn. This fossil soil is eroded more rapidly by wave action than the conglomerate, thus leaving the latter almost loose as though it had been pushed or had slid into its present position. Just east of the mouth of the creek flowing from Ronge Lake there is a shore outcrop of this fossil soil from which the conglomerate has been removed. The outcrop may be seen in the photograph as a point running out into the lake. Several dikes cross the outcrop. They are from 2 to 3 feet wide and exhibit a curious concentric weathering, illustrated in the photograph above. Traced beyond the old erosion surface into the Keewatin lava flows these dikes appear to be quite homogeneous. Nothing that the writer could interpret as evidence of organic remains was discovered. The use of the term "soil" is, therefore, questionable; regolith would apply better. In the iron formation on the shore by the island referred to above, features are filled with anthraxolite and quartz. Tantonl has reported this occurrence and another farther to the west and attributed its origin to bituminous shales in the Animikie sediments." Gill (1926) describes a re-worked regolith between the Gunflint Formation and granitic country rock in the North Lake Area, 100 km southwest of Thunder Bay, as follows: "Remnants; of the basal conglomerate up to 2 feet thick were observed. The thickest of these occupy what were evidently depressions in the floor of the Animikie sea. Pebbles vary in diameter from a fraction of an inch to 8 inches. By far the greatest number are milky 33

quartzr in some cases with associated orthoclase. The others — with the exception of a few of chert, the origin of which is doubtful — are partly rounded fragments of the rocks composing the surface upon which the conglomerate .' was deposited. The rock types represented are granite, syenite, diorite, hornblendite, . andesite, and chert. The pebbles are set in a matrix of finer rock fragments and quartz particles with more chloritic material, probably developed from the ferromagnesian minerals of the underlying rocks, and a few mica flakes. This obviously sedimentary accumulation grades downward, through material with the same general appearance as the chloritic cement of the conglomerate with only a few quartz particles distributed through it, to unaltered granite, in such a way that it is in many cases impossible to be sure just where the sediment ends and the granite commences.

The pebbles show typical water-worn forms, but rounding is usually very imperfect. There has been little or no sorting, for individual outcrops show all gradations from large pebbles to the very finest particles, without any marked stratification. From the poorly-sorted nature of the material, the lack of rounding of the pebbles, and the fact that they have all been derived from the rocks immediately below the conglomerate, it is clear that no great- transportation intervened between erosion and deposition. Again, from the great preponderance of the resistant quartz pebbles, the abundance of finer materials of granite decomposition in the cement, and the observed gradation from the conglomerate matrix to altered granite, it is concluded that this sediment has resulted from reworking of a residual soil on the pre-Animikie land surface, by the advancing Animikie sea." While still a subject for further study, certain units in the Steep Rock Lake area near Atikokan clearly resemble regolith. The "buckshot" at Steep Rock Lake zones contain numerous pisolite and/or goethite with minor amounts of maghemite, in a matrix of kaolinite, gibbsite, chalcedony, quartz, geothite and hematite (Shklanka 1972). The buckshot zones consist of ferruginous lateritic material.

An erosional unconformity between the Steep Rock Group rocks and the underlying basement rocks has been postulated by many authors. Pye (1968) states: "The "Paint Rock" is a soft, earthy, crudely banded material made up largely of iron oxides, quartz and chert, clays, and subordinate manganese-bearing minerals. It is believed to be an ancient residual soil formed by the deep weathering of the underlying limestone. It lies adjacent to the orebodies, forming their footwall." The hematite-quartz breccias in the Goodmorning Lakes Fault area (Yule 1979) and those reported by Coleman (1909) and Scott (this report) in the Black Sturgeon Lake area are similar to the quartz-hematite breccias at Rum Jungle and South Alligator River Districts of Australia (Ojakangas 1978). The Australian breccias are considered to be a Proterozoic regolith, and are associated with uranium mineralization. This is also the case for the Goodmorning Lakes Fault breccia and the hematite-quartz breccias of the Black Sturgeon Fault area.

Parham (1970) has reported up to 61 m of a "weathered residuum" that has developed on the upper surface of the Precambrian in the southern Red River valley area of eastern North Dakota and western Minnesota. The regolith is best preserved where it is 35

immediately overlain by Cretaceous rocks. Feldspars and micas are altered to kaolin group minerals and the end-product of weathering is generally a white to greenish kaolinitic clay containing Suspended angular quartz grains. Indications are that there was a pre-Cretaceous kaolinitic weathering episode on the southwest portion of the Canadian Shield. Climatic differences between the Red River Valley of Minnesota and the Thunder Bay-Nipigon area would not have been too different as they are only about 500 km apart.

Hayatsu et al. (1983), using a chemical method in analyzing anthraxolite from the Ontario Hydro Spillway near Kakabeka Palls, came to the conclusion that there were two fractions of hydrocarbons in the anthraxolite and that they were derived from sediments of two vastly different ages. The older portion was derived from organic remains during the deposition of the Gunflint Formation; the younger fraction is Cretaceous, or Jurassic, in age (65-100 my). Therefore, the area around Thunder Bay was once covered by Cretaceous or Jurassic marine sediments.

Purucker (1983) identified a Cretaceous magnetic component in hematite from the Gunflint Formation near Loon Lake and states the ore-forming process was Cretaceous in age. The hematite and magnetite were derived from the oxidation of iron carbonate and iron silicate minerals and are thought to be coincident with the development of an Al- and Fe-rich regolith that covers much of northern and western Minnesota. 36

Thus, weathering and alteration of a regolithic type are present in the Nipigon Basin, although their extent and nature have not been determined to date. Because of the transgressive nature of the Sibley Basin, this regolith may have been removed or reworked. If this is the case, the regolith should be preserved in areas such as valleys, down-faulted blocks, and where Sibley Group deposition has occurred rapidly. There have been three notable episodes of weathering in the Nipigon Basin: (1) a late Archean episode that took place prior to the deposition of the Animikie Group and is manifested by weathered Archean granitoids and volcanic rocks that underlie the Animikie and Sibley Group rocks; (2) a pre-Middle Proterozoic episode that took place prior to the deposition of the Sibley Group and is evident in the weathered English Bay porphyry (1536.7 + 10/-2.3 Ma, R. H. Sutcliffe, Geologist, Ontario Geological Survey, personal communication, 1982) that is overlain by Sibley Group conglomerate and sandstone as well as the oxidized portions of the Rove Formation as exposed at Pass Lake; and (3) the formation of a 2 m thick lateritic soil profile southeast of Leckie Lake on Late Precambrian diabase, gabbros and peridotites that intrude Sibley Group sedimentary rocks. This episode is clearly post-Late Precambrian; it may even be Cretaceous, although that concept remains to be proven. 37

URANIUM EXPLORATION HISTORY . Prom 1947 unfa the present, there were four distinct periods of uranium exploration activity in the Thunder Bay area, as graphically illustrated in Figure 3.

The first documentation that rranium was associated with the Sibley Group rocks came in 1947 when T. L. Tanton discovered radioactive "nodules" in Sibley Group mudstones near Nipigon (Tanton 1948). Although an exact location for these nodules is not given, the feature described is similar to the white "reduction spheres" mentioned by Franklin et al. (1980). These spheres occur in the upper portion of the Rossport Formation and throughout the Kama Hill Formation ( Photograph 5) and are common in the Nipigon-Black Sturgeon area.

In 1949, T. Christianson discovered a radioactive pyrite-marcasite vein in a fault on the west side of Greenwich Lake (NTS 52A 15/SW). This showing is known as the Christianson Showing and has been the focal point of uranium exploration in the Greenwich Lake area.

The second early discovery of uranium mineralization was by T. Gustafson in the Port Munro area, just northwest of Marathon. Gustafson staked a columbium-bearing syenite dike that intrudes the Port C Idwell Alkalic Complex. Photograph 5. Reduction Spots. The second flurry of uranium exploration activity in the

North Central Region was a spinoft of the large

staking rush that took place in the Elliot Lake area in

the 1950's. During this period, Messrs. Tessier and Williamson

staked a pegmatite in Hele Township (52A 15/NE) and claims

were staked in Sibley Provincial Park by Stancan Uranium

Mines. The Greenwich Lake area was quite active, with

Pan Canadian Development Company conducting a major exploration

project centred on the Christianson Showing. Additional

work in the Greenwich Lake area was conducted by M. E.

Holt interests, which drilled a series of radioactive veins

in lineaments. Drilling results were favourable, with .

values ranging up to 0.80 percent U3O8 over 1.01 metre

widths (Resident Geologist's Files, Ontario Ministry of

Northern Development and Mines, Thunder Bay, Ontario).

Interest in uranium waned again until the late 1960's,

when there was a flurry of activity in Northwestern Ontario.

Again, the Greenwich Lake area was the centre of activity

v in the Nit .igon Basin. In addition, the Prairie Lake Complex was prospected for uranium by Newmont Mining Corporation

of Canada. To this date, the Prairie Lake Complex contains

the only uranium deposit with a drilled off tonnage in the region (200,000 tons at 1.8 lbs per ton U3O8 to 270 feet in the B-Zone, Northern Miner, March 5, 1979). s sill\ s s SI s i sisi!iilisss : 2 2 is i: t ft % ; s s

T L Tanton £ t T Chfistianson £ T Gustaison % • 1 easier-Williamson • Pan Canadian Development Sibloy Provincial Park • ME Holt • Falcontmdge Nickel Mines • • C. Morton • Univex • Celoiti • Consolidated Monarch • BP Minerals • • • Rio Tmio • • Asarco • • • • Shell • • Norcen o • Greenwich Lake Explorations • • Uranerz • • • • Saarberg Inlerplan • • • Eldorado Nuclear Gult Minerals • • Newmoni Mining Corp • • 9 New Insco • • •

Figure J. Uranium exploration activity by year and company, Nipigon Basin, 1947-1983 By far the largest impetus to uranium exploration activity in the region was the discovery of large unconformity-related uranium deposits in northern Saskatchewan and Australia in the middle to late 1970's. This fact is dramatically illustrated in Figure 3. Due to the similarities in the geology of the Athabasca area and the Nipigon Basin, exploration reached an all time high, with more than 14 mining companies and many more individuals searching for uranium in the Nipigon Basin during the middle to late 1970's.

In 1982, Saarberg Interplan Canada Limited was the only exploration company actively searching for uranium in the area. Up until July 1985, Uranerz Exploration and Mining Limited had claims in good standing in the Black Sturgeon Lake area (52H 7/SW). URANIUM DEPOSIT TYPES In the North Central Region uranium mineralization occurs in a variety of environments that can be characterized as follows: I. Uranium mineralization associated with Quetico Belt leucocratic pegmatites and quartz monzonite intrusions. II. Uranium mineralization associated with veins and faults at or near the Archean-Proterozoic unconformity. III. Uranium mineralization associated with diatremes, carbonatite, carbonates and alkalic complexes of Middle to Late Precambrian age. IV. Minor uranium occurrences associated with the Gunflint Formation "mudball tuff" and "radioactive nodules" in the Sibley Group (Tanton 1948).

Each of the above will be described in general terms and then detailed property descriptions will be presented for the major occurrences.

URANIUM ASSOCIATED WITH QUETICO BELT LEUCOCRATIC PEGMATITES AND QUARTZ MONZONITE INTRUSIONS Uraniferous, albite-rich pegmatites occur as lenses and dike-like forms in the Greenwich Lake area (52A 15/SW), the Innes Lake area (52A 15/SE), in Hele Township east of the Black Sturgeon River (52A 16/NW), on the west shore of Lake Helen north of the mouth of the Nipigon River (52H 1/SW), in the southern portion of Trottier Township (52B 14/SE), near and north of Manitouwadge (42F4), near Melchett Lake north of Nakina (42L 11/NE), east of Black Sturgeon Lake (52H 7/SW), and south of Pinlayson 43

Lake (42E11/SE) on the Kenogamisis River. Most of the occurrences of this type are in the Quetico Gneiss Belt.

All of the occurrences exhibit the following general characteristics. The pegmatites are usually white and consist of albite, biotite, quartz, minor muscovite and accessory apatite. An autoradiograph from a sample of the Greenwich Lake pegmatite from Trench 75-B-l indicates that the radioactivity is closely associated with biotite. The radioactive mineral has been identified as uraninite (Franklin 1978a). A secondary yellow uranium mineral(s) (uranophane?) is common to many of these pegmatites and usually occurs on fracture and weathered surfaces. Blair (1977) has demonstrated that the uraniferous pegmatites at Greenwich Lake are conformable with the easterly trend of the metasedimentary rocks. The pegmatite boundaries are usually well defineu and regular. Some sections of the pegmatites contain xenoiiths of the host rock as well as tonalite gneiss (Franklin 1978a).

No doubt there are more radioactive pegmatites within the Quetico Belt that have yet to be discovered. While concentrations of uranium within the known pegmatites are non-economic at present, they are perhaps one of the principal source rocks for uranium associated with veins and faults at or near the Proterozoic/Archean unconformity. URANIUM ASSOCIATED WITH VEINS AND/OR FAULTS AT OR NEAR THE PROTEROZOIC/ARCHEAN UNCONFORMITY Occurrences in this category exhibit a large range of characteristics. They are all associated with faults and fracture systems proximal to the unconformity. Sibley Group rock fragments have been identified in the Christianson Showing breccia at Greenwich Lake (Fenwick and Scott 1977, Franklin 1978a), implying that the unconformity, although now eroded away, was present not too far above the current erosion surface.

Uraniferous veins of this type are found at Greenwich Lake (1), Goodmorning Lakes Fault Zone (2), Dorion Amethyst Mine (3), Jessie Lake Area (4), Enterprise,Mine (5), the Black Sturgeon Lake Area (6), in the Frazer Lake Area (7), and at the Little Bear Amethyst Mine near Kabamichigama Lake (8). The numbers refer to locations on Map 1.

At Greenwich Lake, the uraniferous veins occupy a set of northerly to northwesterly-trending fractures. The best documented of these is the Christianson Showing, located on Greenwich Lake Exploration Limited*s property (Blair 1977, Fenwick and Scott 1977, Franklin 1978a). A detailed description is found in the section on Greenwich Lake found elsewhere in this report.

Hematite is almost always associated with occurrences of this type and is a good indication of possible radioactivity. Alteration associated with the Goodmorning Lake Fault Zone occurrence has been described by Yule (1979), and consists 45

of 3 types: dark green chloritization, red hematization

and pale green sericitization. Rocks exposed in the Goodmorning

Lake Fault zone may be a regolith. The detailed geology of the

property is described in the section on property descriptions.

Other properties that exhibit hematite alteration associated with a radioactive occurrence are the showings at Jessie

Lake and Greenwich Lake. A cursory examination of some of the hematite showings described by Coleman (1909) indicated that zones of radioactivity are present and should be investigated.

The occurrences of this type most closely resemble the

Athabasca unconformity type and have the best potential for uranium.

URANIUM ASSOCIATED WITH DIATREMES, CARBONATITES AND ALKALIC COMPLEXES

Deposits associated with these rock types are found near the Port Coldwell Alkalic Complex located at Marathon.

Uranium mineralization was discovered at Prairie Lake by

Jim Gareau while prospecting for Newmont Exploration Limited in 1968. The geology of the Prairie Lake carbonatite and area has been described by Watkinson (1969) and Meillon (1969).

Sage (1983) mapped the Prairie Lake carbonatite for the

Ontario Geological Survey. Closs and Sado (1982) conducted orientation overburden geochemistry and Quaternary geology studies in the Prairie Lake area.

Uranium mineralization was discovered in 1978 by Gulf Minerals in diatreme rocks approximately 3.2 km north of Highway

17 along the Deadhorse Creek Forest Access Road. Highway 17 crosses Deadhorse Creek approximately 6.5 km west of the Little Pic River. The area was mapped by Keil (1978) for Gulf Minerals and by Sage (1982) for the Ontario Geological Survey and is also described by Mitchell and Platt (1977).

URANIUM ASSOCIATED WITH MIDDLE PRECAMBRIAN GUNFLINT FORMATION MUDBALL TUFF AND SIBLEY GROUP "NODULES" Darnley et al. (1970) report anomalous uranium to thorium and uranium to potassium ratios in the vicinity of Thunder Bay. Careful examination of thei.r map reveals that the anomaly actually plots in the vicinity of Kakabeka Falls.

Cursory examination of various rock units with a McPhar TV-1 gamma ray spectrometer revealed that the "mudball" tuff of the Gunflint Formation is moderately radioactive. The mudball tuff unit is exposed at the Kakabeka Falls Provincial Park in the Kaministikwia River bed under the Highway 17-11 bridge. It also crops out on the Ontario Hydro property just south of the Kakabeka Falls Provincial Park boundary. A grab sample collected by the author returned an assay of 0.004% U3O8. The rock unit is an accretionary lapilli tuff and consists of flattened lapilli, probably deposited as a mudball rain during volcanism. Gill (1926) reports that the lapilli tuff crops out in the North Lake area and is in the order of 45 cm thick. A compilation of stratigraphic sections from various parts of the Gunflint Formation seems to indicate a general thickening of the lapilli tuff member toward the southeast. Gunflint Formation flow rocks have been described from the Whitefish Lake "^ A" *^ '*

Photograpn 6. Mudball Tuff, Kakabeka Falls, cut parallel to bedding. Note the anthraxolite veining. area (Gill 1926, Tanton 1931, Goodwin 1960). Photograph 6 illustrates the mudball tuff. Tanton (1948) reported that "nodules" in the Sibley Group are radioactive and contain uranium. Work by Ellesworth (1934) on anthraxolite collected .' by T. Ii. Tanton in the Gunflint Formation revealed that the anthraxolite was radioactive. Kwiatkowski (1975) analysed anthraxolite from the Kakabeka Falls area, also in Gunflint Formation, but found no radioactive minerals.

GENESIS OF URANIUM OCCURRENCES IN THE NIPIGON BASIN Uranium deposits associated with diatreme breccias, carbonatites and alkalic intrusions in the North Central Region are generally magmatic in origin. They are contained in the rocks of the Oeadhorse Creek and McKellar Creek diatremes, Prairie Lake Complex and in late syenitic dikes crosscutting the Port Coldwell Alkalic Complex. These occurrences are situated east of the Nipigon Basin and have not been considered in the following model.

Because of the similarities between the Athabasca Basin and the Nipigon Basin in terms of geology and uranium occurrences, any proposed model for the Nipigon Basin would have to incorporate many features of the Athabasca model with modifications to accommodate local criteria. This model must rely on work by Dahlkamp and Adams (1981), McMillan (1978), Barnes and Ruzicka (1972), Ruzicka (1977), Howe (1978), Langford (1978) and Tremblay (1978, 1983) as well as other authors who have made contributions to the classification and understanding of uranium deposits, especially those deposits of northern Saskatchewan and Australia. Dahlkamp and Adams (1981) provide a general framework for the formation of uranium deposits related to the Proterozoic/ Archean unconformity: "(1) During late Early Proterozoic time, uranium and other metals became concentrated in pelitic-psammitic, in part calcareous, sediments often adjacent to organic- rich horizons. Possible pre-metamorphic relocalization led to the formation of deposits such as occur in Gabon. (2) The Hudsonian (in Canada), and time-equivalent orogenies elsewhere, metamorphosed the sediments to the amphibolite and locally to granulite metamorphic facies. (a) In areas of closed systems, i.e., generally remote from intrusions, metasomatism, and anatexis, the uranium became crystallized, but remained more or less in situ, forming strata-bound deposits of generally subeconomic or marginal size (e.g., Kitts, and the protores of the Wollaston Belt). (b) In regions of open systems, i.e., regions affected by granitic and perhaps major mafic intrusions, or by anatexis and metasomatism, the uranium was locally mobilized by metamorphic- hydrogenic processes and reconcentrated in structures within the uraniferous strata (e.g., Beaverlodge, Alligator Rivers district). (3) In some regions, the deposits mentioned under (2) became covered by continental sediments (e.g., by the Martin, Kazan, Kombolgie or other Formations) without undergoing a period of strong weathering and regolith formation. The cover sediments are assumed to have acted as a protection against erosion. The presence of magnesium and boron-metasomatism, at least in the Alligator Rivers district, in both crystalline basement and the overlying sandstones, suggests that diagenetic fluids could have affected any mineralization that might have been present at this unconformity. At Range One, for example, such alteration may have recrystallized and further concentrated the uranium in the near-surface portions of the deposits. (4) In regions where the metasedimentary basement rocks, in the absence of cover rocks, were exposed to a subtropical climate, intense weathering produced a deep regolith. Uranium and other metals must have been liberated and were possibly concentrated in low areas related to structure-controlled valleys, and in lakes or swamps. Organic matter, probably algal, may have accumulated within some of these sites and may have contributed to the accumulation of the uranium and other metals. It is, however, not certain whether these processes operated or, if they did, whether they formed viable orebodies or merely preconcentrations of uranium. So

Where uraniferous volcanics (Pitz, Christopher Island Formation in Northwest Territories; Edith River Formation, Northern Territory) overlay the metasedimentary basement, they experienced the intense leaching of paleo- weathering while protecting the underlying basement. Locally, small uranium accumulations were formed, but large deposits are lacking, perhaps due to a limited amount of uranium (e.g., Baker Lake region, South Alligator River).

fj) Subsequent to the period of chemical weathering, the exposed and weathered basement was covered by continental, arenaceous sediments (e.g., Athabasca, Thelon Formations). The sediments accumulated to thicknesses of several thousand meters. Diagenetic- hydrogenic processes active along the unconformity may have concentrated urcnium and nickel and formed the associated chlorite, kaolinite, and other gangue minerals. If earlier uranium concentrations had formed at the unconformity, they may have been redistributed or upgraded at this time.

(6) Subsequent processes contributed little to improving or upgrading the deposits. Rather, through faulting, fracturing, and ground water movement, they produced local recrystallization (sooty pitchblende, coffinite), redistribution (particularly up into the overlying sandstone), or, in the worst case, destruction of the orebodies."

More than 3.0 billion years ago, the elements-uranium, thorium and potassium were not abundant in the Na-rich sialic rocks, greenstones and associated metasedimentary rocks that formed the earth's crust. These elements were first extracted from the upper mantle during a major granitization and migmatization period between 2.7 to 3.0 billion years ago (Moreau 1974). This is generally considered as the start of the uranium cycle in the earth's crust, with the felsic igneous rocks the first host. From there, uranium was dispersed mechanically and later chemically throughout geological time and was concentrated under specific conditions, in a well defined timeframe, in sedimentary rocks SI

(Meneghel 1980). This time-bound characteristic of uranium deposits is well documented by Robertson et al. (1978), Meneghel (1980), Roscoe (1973), and McMillan (1977). Figure 4 illustrates the interrelationships between the uranium cycle and the asthenospheric, hydrospheric, and biospheric evolution. The table depicts profound changes in the earth's evolution. These changes were the transition from soda-rich to potassic-rich magmatic rocks, the development of life, the changing atmosphere, hydrosphere and biosphere conditions with the appearance of oxygen. The critical change was the evolution of the environment from an oxygen-depleted to oxygen-rich.

The oldest paleontological evidence that oxygen was beginning to accumulate in a previously anoxic hydrosphere and thereby escape into the atmosphere comes from the Early Proterozoic Gunflint Formation of approximately 2 billion years ago (Cloud 1983). The evidence of the evolution of the early atmosphere is preserved in the Gunflint Formation microfossils and has been extensively documented by numerous authors.

The following topics have to be considered in developing a model for the uranium occurrences in the North Central Region: 1. Uranium source area 2. Means of releasing available uranium 3. Transportation of uranium 4. Deposition of uranium in structural and/or chemical traps 5. Preservation of the deposits UTHOtPHENC HVDROSPHERIC ATMOSPHERIC MOSPHENC URAMUM ECONOMIC RESERVES AOE URAMUM CYCLE EVIXUTIOH EVOLUTION EVOLUTION EVOLUTION Incraaakig raaarnaa

' Sanddona lypa d»PMHs Ma|MCoal (wmnttont i«ra>toMI radiation Urankm cotMani o> circUaaVv

Sub-acono

Vam-typa dapoaHa CharrtcaHy dittolvad uranlurn la Irantpotlad in MatwIgnaoua S, totuttofi and dapotHad In radudng anvdonmams craalad by organic manar In paMc aadimanti acMty l\ In lha ahaK tona HrMrad J Aiga^Mooma Amkn aatfmanta Saawalaf baeama Oiygan aacapaa from Uranium In daiilM more and mm •na hyitroaphara lo oiyganalad and lha naar aurlaca air daarad ol dkuolvad Iron and othar Conglomarala-tyoa dapotils maiariah CO j daciaailng

Uranium u machamctfy Iranspoflad and Ma|« Ihaimal !! ayngenaltcaKy concamralad as dalnlus avam ll j Ill if

Saawalai praumabl) 1 PhMoayMnallc raihar acid Xlh organMrna Wgh CO 2 contain

ii

From Managnal II9B0I Adapted Irom wnrk by Cloud (1972.19761. Garrals el al H97II. and Mweau 119741 Figure 4. The Uranium Cycle and Asthenopheric, Hydrospheric, Atmospheric and Biospheric Evolution Source Area The most probably source area for uranium deposits associated with veins and faults that are proximal to the Proterozoic/ Archean unconformity is the granitoid and associated meta- sedimentary rocks of the Quetico Gneiss Belt. The Geological Survey of Canada Open File Reports 745 (1980) and 746 (1980) depict the regional lake bottom geochemistry of an area from Fort Frances to Sault Ste. Marie at a scale of 1:2,000,000. The Quetico Gneiss Belt's signature is one of anomalously high uranium background levels and, in fact, shows up as a 490 km long by 80 km wide regional uranium anomaly, that contains numerous hot spots near to or in excess of 100 ppm uranium in lake sediments.

The northern portion of the Nipigon Basin is underlain by metavolcanic and associated rocks of the Wabigoon Belt. Metamorphism is of much lower grade in both the Shebandowan- Wawa Belt and the Wabigoon Belt than in the Quetico Belt. The far northern sector of the Nipigon Basin is underlain by rocks of the English River Gneiss Belt. Although not much is known about the English River Belt rocks, at least with respect to uranium, Satterly (1955) and Breaks (1982) report on uranium occurrences north of Kenora in the granitoid and migmatitic rocks of the English River Belt. Two types of uranium mineralization were recognized by Breaks (1982). The first type is a metasedimentary migmatite association and the second type is associated with a potassic granitoid suite of rocks that include coarse grained to pegmatitic quartz monzonites and granites. This type of association has also been documented in similar

rocks in the Quetico Gneiss Belt in the Greenwich Lake area

by Blair (1977), Penwick and Scott (1977), Franklin (1978)

and Carter (1981).

The relation between the uranium source rocks in the Quetico

Gneiss Belt and the uranium deposit in the Greenwich Lake

area is illustrated in Figure 5.

Several members of the Gunflint Formation, most notably the mudball

tuff unit at Kakabeka Falls, -iould be a good source bed for

uranium.

Weathering of a pre-existing terrain mechanically released

uranium into a sedimentary package of roc'fji that was metamorphosed

to become the migmatites and gneisses of the Quetico Belt.

Partial melting of these rocks concentrated uranium in

pegmatites and similar granitoids. Prior to the deposition

of the Sibley Group there was a period of weathering, making

more uranium available in weathered rock products.

Means of Releasing Uranium and Transport

Uranium is released into the cycle from source rock areas by either mechanical or chemical means. This is accomplished by intense weathering of source areas coupled with mechanical transport and later, as the atmosphere became oxygen-rich, by chemical transport. The mechanical disaggregation of a source rock results in transportation of the radioactive minerals by moving water, with deposition in suitable areas ss

of a drainage regime. Mechanical transport took place

in an oxygen-depleted environment during the Lower

Proterozoic, and as the atmosphere became more aerobic

chemical transport of uranium in solution prevailed,

depending on the pressure-temperature conditions operative

at the time.

Deposition in Structural and Chemical Traps

The regolith on the Archean surface was reworked by the advancing beach line of the Sibley Basin. Sibley Group rocks were deposited in the block faults that resulted from the

Keweenawan rifting. I-ntrusion of diabase in the form of dikes and sills, coupled with high hydraulic gradients present in the block-faulted sub-basin valleys resulted in flow of ground water that carried dissolved uranium to structural and/or chemical traps where it was deposited as pitchblende.

Sulfur isotope studies by Franklin (1981) indicate that the metals precipitated from a low temperature solution, as a result of mixing of dilute, metalliferous brine with stratigraphically-trapped, organically-generated H2S.

Subsequent erosion of the overlying Sibley Group rocks exposed the occurrences in portions of the basin.

This concept is similar to the one outlined by Franklin (1970), and described in more detail by Franklin and Mitchell (J977) and Franklin (1981), for the unconformity-related lead-zinc-barite veins in the McTavish Township to Nipigon area. Metal was leached from Archean and Proterozoic basement rocks in a warm, equatorial, oxidizing environment and was transported as chloride-iron complexes. The metals were precipitated 56 from the pregnant brines as a result of a reaction with reduced sulfur that was probably derived from decayed organic matter. This reaction took place at the Sibley sandstone pinchouts with Archean basement rocks. Hawley (1929) and Tanton (1931) give good descriptive accounts of the lead-zinc-barite veins of the region.

The presence of an unconformity-type plumbing system is without dispute. Some of the Pb-Zn veins of the area also contain uranium. Since the vein metals reflect local bedrock sources, the problem is in locating similar vein systems in or proximal to the major uranium source rocks - the granitoids of the Quetico Belt.

A lead isotope study (Russell and Farquhar,1960) of several lead-zinc-barite occurrences in the McTavish Township area indicates that the galena had large infusions.of radiogenic lead prior to being deposited. Russell and Farquhar (1960) state: "This lead has approximately the isotopic ratios of a lead separated from the source material at a time about 1,000-1,100 million years ago...the radiogenic component in the anomalous leads has been extracted on a local scale from rocks and minerals in which the uranium and thorium are distributed in a heterogeneous fashion because of their different chemical properties." A plot of 208pb/204Pb vs 206Pb/204pb for the Thunder

Bay region samples (Russell and Farquhar 1960) generates a straight line with a slope of 0.37; the lead isotopes were beiag generated in this ratio 1,700 million years ago by a mixture of 1.4 g of thorium per gram of uranium. This value is less than half the value commonly accepted as the crustal average, and therefore suggests the possibility that the local rocks were enriched in uranium in preference to thorium.

Preservation of the Deposit

Continued sedimentation of Sibley Group rocks would have preserved the deposits. Conceivably, other similar deposits would still be buried. se

Summary - Nipigon Basin Model

(1) Granitoid and sedimentary rocks were metamorphosed to form the Quetico Eelt of rocks. Uranium was mobilized

and concentrated in leucocratic pegmatitic dikes. A period

of erosion and weathering mechanically released uranium.

It was at this time that the earth's atmosphere was evolving

from an oxygen-depleted state to one that was enriched in

oxygen. Uranium was increasingly transported chemically

in aqueous solution as more and more oxygen was available.

(2) In the southwestern sector of the basin, Gunflint Formation

volcanism was enriched in uranium (mudball tuff) and could

be a source for uranium. Uranium was precipitated in areas of algal stromatolite concentrations. Present day exposures of algal stromatolites abound near the Archean-Proterozoic unconformity in the Whitefish Lake area (Goodwin 1960).

Deposits that could be related to the Gunflint Formation would be preserved by the deposition of the Rove Formation.

(3) Uranium liberated under conditions described in (1) was deposited in structural and chemical traps related to the

Sibley Group Pass Lake Formation pinchouts similar to and contemporaneous with the Pb-Zn-barite.

(4) These deposits were subsequently covered by Rossport

Formation and younger rocks.

(5) Diagenetic alterations and tectonic adjurtments may have reconcentra :ed the uranium. 59

EXPLORATION GUIDELINES Map 4 illustrates the relationship of faults and lineaments to various types of mineralization in an area of approximately 30 km radius around Greenwich Lake.

Locations of vein deposits containing uranium, lead-zinc and molybdenite are shown on Map 4. In addition to lead and zinc, these occurrences may also contain copper, amethyst, barite, calcite and sometimes gold (a sulfide-rich section of the Thunder Bay Amethyst Mine breccia assayed 0.30 ounces gold per ton and Tanton (1331) reported 0.33 oz/ton gold from the Enterprise Mine,

The large fault zone south of Greenwich Lake represents the eastern strike extension of the Quetico Fault Zone. Major faults and/or lineaments are easily recognized; however, minor features such as the Christianson Fault can easily be overlooked. A detailed structural structural .analysis is warranted to unravel the tectonic history of the Greenwich Lake area and to determine what parameters make certain fault zones conducive to uranium deposition.

Diligent prospecting along the Goodmorning Lakes Fault Zone, especially in the vicinity of the intersection of the pegmatite trend and the fault zone is warranted. Although Yule (1979) reported a lack of sulfides and/or graphite in the fault zone, his observations are restricted to a relatively small area (150 m x 80 m). The presence of reducing agents such as graphite and/or sulfides would greatly improve the MINERAL OCCURRENCES AND LINEAMENTS GREENWICH LAKE AREA (52AI5)

Map 4. Faults, lineaments and mineralization in Greenwich Lake Area chances of uranium precipitating out of solution in the

fault zone. Graphite or sulfides could be detected using

electromagnetic techniques. Deposits of lead and zinc

sulfides do occur in the area at the Ogema Mine and near

Cavern Lake. These deposits occur in fault zones at, or

near, the Sibley Group/Archean unconformity in a manner

described by Franklin (1970) and Franklin and Mitchell (1977)

In the Greenwich Lake area, approximately 25 km to the west,

sulfide-filled fault zones contain good uranium values.

The Goodmorning Lakes Fault has a strike length of about

4,600 m, of which less than 10% has been explored in detail.

Yule (1979) has inferred that the uranium mineralization pre-dates the Pb-Zn-barite systems. While this might b-z true of his investigation, it is not the case elsewhere. The

Enterprise Mine in Lot C, McTavish Township, contains both

Pb-Zn-barite-Cu and uranium (Fenwick and Scott 1977).

Uranium has precipitated locally in the vicinity of sulfide minerals. The Dorion Amethyst Mine contains chalcopyrite, amethyst, calcite and uranium minerals. If there were a continual supply of uranium from the Quetico Belt rocks, then conceivably more occurrences like the Enterprise Mine might be discovered.

Sphalerite, galena, and chalcopyrite have been reported to occur in some of the Greenwich Lake uranium-bearing veins (Resident Geologist's Files, Ontario Ministry of

Northern Development and Mines, Thunder Bay, Ontario). Vein systems associated with the Sibley Group as described by Franklin (1970) and Franklin and Mitchell (1977) that are proximal to uranium source rocks (pegmatites, granitic rocks, migmatites) should be investigated for uranium. Tantoo (1929, 1921, 1931) describes many of these. One such vein near the Goodmorning Fault breccia occurs just north of Concession XII of Dorion Township. The uraniferous pegmatites at Innes Lake lie approximately 3 km to the southeast. Mcllwaine and Tihor (1972) indicate another lead-zinc occurrence north-northeast of Innes Lake that should be checked for radioactivity.

The Ogema Mine, 3 km south of the main trench area on the Goodmorning Lake Fault, should also be investigated for possible uranium mineralization.

Another mineralized system that should be investigated is a Mo-rich system that strikes westward from a small N-S elongate lake that is situated approximately 0.8 km south of Furcate Lake (52A15/SW). Molybdenite occurs in quartz veins, pegmatites and in schists (Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario).

The search for ore of this type should be conducted where exhumed, 1,700-2,000 million year old peneplains can be identified in proximity to younger cover rocks. Good target areas can be delineated where the younger cover rocks overlie 63

the Quetico Gneiss and the English River Gneiss Belts in the Nipigon Basin.

In assessing the potential for uranium in the Sibley Basin in light of an Athabasca-type model, careful study of available geological maps will delineate areas of best potential. If a deposit is spatially related to a paleosurface, then the Sibley Basin can be broken into areas of high to low potential. This scheme has been illustrated by Robertson et al. (1978), and is reproduced here as Figure 5.

The Pass Lake Formation and, to a lesser degree, the other formations of the Sibley Group are good aquifers. The plumbing system that has been responsible for the various Pb-Zn-Ba deposits might be still operative today. Tanton (1931) and Fraser and Reardon (1980) describe saline springs, and the Ontario Ministry of Natural Resources North Central Region Fish and Wildlife staff have documented numerous "mineral licks". Analyses of some of the water and soil from these springs can be found in Fraser and Reardon (1980). Other analyses are available at the Resident Geologist's Office, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario.

Use of these springs for mineral -t oration purposes is an untested idea that may have merit as a component of a regional geochemical survey. The emanations from the springs contain salts that are representative of rock strata through which the ground water has circulated. To date, there are three general concentrations of known saline springs. A large GOOD PROSPECTING NO HOPE

,Coovei r Rock

PALEOSURFACE I 30 - 150 m L

Paleosurface related deposit

From Robertson et. al. (1978) Figure 5. Prospecting for paleosurface-related uranium deposits. number are located on the islands offshore from Rossport, approximately midway between Schreiber and Nipigon. A second large concentration of these springs is located near the south shore of Lake Nipigon near Black Sturgeon Lake and on the islands in Lake Nipigon. The third major concentration is situated south of Thunder Bay in the Pardee-Crooks Townships area.

The area underlain by Gunflint Formation southwest of the City of Thunder Bay should be explored for uranium.

The presence of a regolith (Gill 1926, Harcourt 1938, Campling 1971);the presence of uraniferous source rocks (Darnley et al. 1970, Fenwick and Scott 1977); the presence of regional block faulting and an active plumbing system (Franklin 1970); and possible urani.um deposition areas in the form of carboniferous units (anthraxolite, algal and stromatolitic beds probably emitting H2S) all tend to enhance the uranium potential of the Gunflint Formation. The Gunflint Formation was deposited at a time when large quantities of uranium would have been chemically transported in an increasingly oxygen-rich environment Areas most favourable for search would be the basal units of the Gunflint Formation that contain large areas of algal and stromatolite development. Goodwin (1960) delineates these areas in the Whitefish Lake area.

In a review of the techniques applied in the search for uranium, one notices that very few companies have made effective use of electromagnetic methods. Figure 7 clearly URANIUM EXPLORATION METHODS, NIPIGON BASIN

GEOCHEMICAt Lake aedlment Stream aedlment Stream water Soil Rock Till GEOPHYSICS AIRBORNE Radlometrlc Magnetic EM GROUND Radlometrlc • © Magnetic EM Radon gaa IP Borehole GEOLOGY ORILLING TRENCHING * SAMPLING

0. CO X ; co Ul z X Ul o (9 ly -1' (0 CD r- a • Ul s _l Ul r j tc • tc < X • I * o2 B < 1 z 1 C :- o t- 111 » k 8 z:•5*! J (0 5 ! to z

BER G >- OWE S IE R * ! a WILL I ? !: ' « B <0 (if S i 1 S:l • ;it 5 g::«| oc O J z CO t Q tA ^ 7 a K • ] I • * "C Ul ec to 4 C (0 uSO a a •. • * o O z IE * • o i

Figure 6. Uranium Exploration Methods, Nipigon Basin illustrates this fact. Based on submitted assessment work

on file at the Regional Geology Office at Thunder Bay,

there appears to be paucity of programs that used electromagnetic

methc5s to evaluate or search for conductors that may be

uranium deposition sites. If one is to use the Athabasca

model in the Sibley Basin in search for comparable deposits,

then extensive use of electromagnetic techniques and possibly

other deep-penetrating geophysical techniques is mandatory.

Most of the field work consists of radiometric prospecting

and geological surveys. A distinction is made between radiometric

prospecting and a formal radiometric survey in that the former

consists of traverses through the bush with a scintillometer

and the latter, the use of a scintillometer on a grid.

Use of deep-penetrating, geophysics has been successful in

the Athabasca Basin in defining target areas, but has not

been applied extensively in the Sibley Basin. Standing

(1983) discussed deep-penetrating geophysics as applied to

the Athabasca Basin. The deeper one attempts to penetrate,

the broader the geophysical target has to be in order to detect it. The concept of finding a conductor and drilling it has to be abandoned in favour of outlining favourable geological conditions with geophysics.

Deep drilling is expensive and every datum that can be obtained from the hole should be obtained. Thus, down-hole geophysics should be an integral part of the exploration program. Resistivity, gamma-gamma and neutron logs should be run in order to obtain the electrical parameters, densities and porosities that will be required to assist in the interpretation of electromagnetic and gravity surveys, and to correlate data with geochemical and rock alteration studies. Standing (1983) proposes the following exploration sequence for deep areas using the Athabasca area as an example: 1. Compute gradient from high sensitivity magnetic survey. 2. Combine magnetic and any available gravity data to interpret areas of pelitic basement. 3. VLF surveys and photogeological studies to identify post- Athabasca faulting. 4. Magnetotelluric and/or time domain electromagnetic surveys to define areas of conductive basement rocks. 5. Shallow drilling for geochemical and rock alteration studies and physical property measurements. 6. Reconnaissance deep drilling for geological information, geochemical studies and down-hole geophysics. 7. Deep drilling of targets.

The above exploration sequence is based on the assumption that the uranium deposit is situated at the unconformity, where graphitic pelitic rocks and faulting co-exist. The sequence could be modified as the geological picture unfolds. Techniques used in the Athabasca Basin and described by Cameron et al. (1983) could also be applied to the search for uranium deposits on the Nipigon Easin. PROPERTY DESCRIPTIONS

The following are descriptions of the major uranium properties

in the North Central Region. Because different types of

occurrences may be present on each property, to list them

on the basis of type would introduce needless repetitions

of property descriptions. Therefore, the descriptions are

grouped by property or area.

Greenwich Lake Area Location:

Greenwich Lake is located approximately 56 km northeast of

the City of Thunder Bay. Access is by float- or ski-equipped

aircraft chartered at Thunder Bay or Hurkett. In winter months,

an overland route exists that approaches Greenwich Lake from

the north. Great Lakes Forest Products is currently developing

a road that will skirt the southern part of the lake.

Ownership:

Since the 1950's, numerous mining companies and individuals

have held ground in the Greenwich Lake area. Currently,

Greenwich Lake Explorations Limited have claims in good

standing, covering the original discovery near the west-

central portion of Greenwich Lake.

Previous Work:

Since the discovery of the main showing by Tom Christianson

in 1949, the Greenwich Lake area has been the focus of uranium exploration in the Nipigon Basin. MW IIW itw 11*

no mra Mn.oiwnoH. MPOMT WOVOWW W.M

Map 5. Geology of the Christianson Occurrence, Greenwich Lake. 7/ A summary of the exploration activity is shown on Table 4. Carter (1979) mapped the Greenwich Lake area for the Ontario Geological Survey. Numerous company assessment work reports are available for the Greenwich Lake area'.

Regional Geology The geology of the Greenwich Lake area has been described in detail by Blair (1977), Fenwick and Scott (1977), and Carter (1979) and summarized by Franklin (1978). The following has been adapted from these references. The Greenwich Lake area is underlain by rocks of the Quetico Gneiss Belt, and consists of arenaceous to argillaceous metasedimentary rocks, sills and lensoid stocks of quartz monzonite, and albititic pegmatite dikes. Late Precambrian diabase dikes intrude this rock assemblage.

Medium grained, quartz-bioti^e-plagioclase gneisses, biotite schists and pegmatitic, white-weathering granitoids are the oldest rock units in the Greenwich Lake area and represent migmatized sedimentary rocks that have undergone regional metamorphism of almandine-amphibolite rank (Carter 1979). The widths of the melanosome and leucosome units range from 3 cm to 0.6 m; larger leucosome units are up to 6 m wide and the concordant pegmatitic units are lens-like in shape and are up to 120 m long by 30 m wide. The gneisses are black to dark grey in color and have a strong laminar appearance. The rocks are highly folded in areas; ptygmatic structures are common- Non-migmatized metasedimentary rocks crop out near the south end of the lake and exhibit graded bedding, small scale crossbedding and clast rip-up features, all indicating a north-facing sequence. Metamorphic grade increases northward from greenschist to almandine-amphibolite rank (Carter 1979). The gneissic rocks are intruded by tonalite and quartz monzonite. Tonalite is the dominant granitic and pegmatitic phase within the migmatites. It is equigranular, and composed of sodic plagioclase, quartz, biotite and muscovite. It can occur as thin bands within the biotite schists or as pegmatite dikes several metres in width. The tonalite is strongly sheared and usually parallels the regional gneissosity. Xenolithic blocks of country rock in various stages of assimilation occur in the tonalite.

The quartz monzonite intrudes all rock types except the diabase dikes. The quartz monzonite intrusions are elongate and have steeply dipping contacts. The rock is massive, coarse to medium grained, and is composed of K-feldspar, quartz, biotite and muscovite. Contact phases of whitish granodiorite may border the intrusion. Pegmatitic phases do occur and their contacts are sharp and parallel the regional genissosity. Xenolithic blocks of biotite gneiss do not show rotation or any degree of assimilation by the quartz monzonite. The quartz monzonite bodies vary in width from 60 m to in excess of 2,500 m. The quartz monzonite is cut by numerous north-trending fractures. "73

TABLE 5.

EXPLORATION HISTORY, GREENWICH LAKE AREA COMPANY or YEAR INDIVIDUAL PROPERTY WORK DONE 1949 Tom Christianson Greenwich L. Original discovery of Exploration radioactive rocks in area 1955- 1956 Pan Canadian •I Trenching, sampling, 16 Dev. Co. Ltd. diamond drill holes - 402 m

1958 Checklin & n Trenching, Geological, Othmer mapping

1958 M. E. Holt Diamond drilling: Property Hole 4: 0.5% U308/l m; 0.42% U308/.49 m; 0.12% U3O8 over 0.24 m; Hole 8: 0.80% U308/1.01 m

1969 O]a Ltd. Morton Air radiometric - Property 1969 Univex Expl. n 4 diamond drill holes - & Dev. Corp. poor results 0.8 lbs/T Ltd. (E)

1975 Copper Lake Celotti Prospecting, radiometric, Expl. Ltd. Uranium trench + drilled

1975 Consol. Monarch Christianson 6 diamond drill holes, MW Resources Showing 406 m. Best: 0.06% Ltd. U3O8/O.43 m, 0.07% U308/0.46 m

1976- Rio Tinto Christianson Trenching, geological 1977 (Riocanex) mapping, radiometric survey, 3 diamond drill holes - 506 m. RA float located. 33 lbs/T 1978 Greenwich Lake Christianson 20 diamond drill holes Expl.

1979 Norcen Norcen Geological, AFMAG, Radongas + geochem. The diabase dikes follow north-trending linears and form gullies that are steep-walled, flat-bottomed and have generally uniform widths. The diabase is less resistant to erosion than the rocks it intrudes and, therefore, weathers out. The dikes can be up to 10 m wide. They are considered to be Late Precambrian in age and cut all other rock units in the area. The geology of the Christianson Showing is shown on Map 5.

Three types of pegmatites have been recognized by Franklin (1978) in the Greenwich Lake area. These are quartz-feldspar mobilizate veins and dikes, pink microcline-bearing dikes, and white albite-muscovite-biotite-quartz bodies. The pink microcline-bearing dikes may be comagmatic with the quartz monzonite intrusions and cut all other rock types except t .e diabase dikes.

Economic Geology Uranium mineralization occurs in two principal modes in the Greenwich Lake area. Syngenetic occurrences of uranium are associated with quartz monzonite stocks, and the quartz- feldspar mobilizate veins and dikes and albite pegmatites. Epigenetic deposits are characterized Ky pyrite-pitchblende veins.

The albite pegmatites have been described as "tonalite" by Blair (1977). These pegmatites occur as semicontinuous dikes and lenses within the contact zone between the biotite schists and the quartz monzonite. In the north contact -7S

zone all radioactive pegmatites occur within 60 m of the

quartz monzonite contact. The dikes consist of 70-80%

albite, 10-20% quartz, 1-10% biotite, 1-5% muscovite and

0.1-0.5% apatite (Franklin 1978). The dikes are sheared

and well foliated. The foliation is conformable to the

trends of the enclosing migmatitic gneisses. The tonalite

ranges in width from 1.5 m to 10 m, with 4.5 m to 6 m being

average. Uranium is present as uraninite, in close association

with biotite. Radioactive pegmatites in the Greenwich

Lake area contain apatite and zircon as accessory minerals.

Uranophane and other secondary uranium minerals occur as films and coating on fractures and joint planes.

Uranium mineralization within the pegmatites is erratic; the best analysis obtained from a selected grab sample was 0.12% U3O8. While the radioactivity associated with the pegmatite zone is generally quite high, the uranium content appears to be negligible. Core analysis by Rio

Tinto yielded a high value of 1.4 lbs U3O3 per ton across

5 feet (Blair 1977). Most other sections assayed below

0.4 lbs U3O8 per ton. While uranium is present in the pegmatites, it is not present in a sufficient quantity to constitute ore grade at this time. If ore is to be found in the Greenwich Lake area, then the pyrite-pitchblende vein type of occurrence will probably provide it.

The pyrite-marcasite-pitchblende veins of the Greenwich

Lake area occupy north-trending fracture sets: The Ch 'istianson TABLE 6. ANALYSIS - GREENWICH LAKE

Sample Number Uranium Thorium Copper Lead F-87-78 290 ppm 20 ppm Qtz. monz. F-10-79 800 ppm F-11-79 2500 ppm F-44-77 2.48% 30 ppm Greenwich L. Float F-48-76 0.12% 0.02% 0.04% 0.31% Pegmatite F-49-76 0.02% <0.005% Pegmatite F-50-76 0.03% <0.005% Fault BX (Swamp) 82-JS-O-lO 4100 ppm 50 ppm 268 ppm Univex/ vein + pitchblende 82-JS-U-ll 1.1% 40 ppm 2230 ppm Christianson Showing, Hanging wall vein breccia 82-JS-U-12 110 ppm 10 79 ppm Swamp trench Photograph 7. Pyrite breccia, Christianson Occurrence, Greenwich Lake.

Photograph 8. Radioactive hematitic float, Greenwich Lake Area. Float assayed 2.4% U3O8. 78*

fault trends NNW and the Univex Showings, located approximately 1,200 m to the NNW of the Christianson Showing, are associated with a NNE lineament. These faults may represent a conjugate set. The largest vein found to date is the Christianson Showing. Drilling by Pan Canadian Development Company Limited has outlined two "ore shoots": one is 5.9 feet by 150 feet, averaging 0.15% U3O9; and the other, 5.0 feet by 150 feet, averaging 0.29% U3O8. Extension to depth was not tested (Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario). The breccia zone that contains the vein is up to 3 m wide. The displacement along the fault is in the order of 3 5 m (Blair 1977).

The vein is up to 1 m wide and is composed of fine grained quartz, pyrite, and marcasite together with brecciated host rock and Sibley Group fragments. Alteration of the wallrocks consists of disseminated pyrite and. quartz and permeates approximately 1 m from the vein (Franklin 1978a). Vein contacts are slickensided, indicating movement along • the fault zone.

At the original Christianson Showing, an approximately 0.5 m width of pyrite is exposed for 10 m in a small ravine. While the pyrite is radioactive, the highest readings on the McPhar TV-1 gamma ray-spectrometer were obtained from a breccia zone in the hanging wall of the vein. The breccia is pale buff in color and fragment sizes do not exceed 2 cm across. 7?

A sample of the breccia collected by the author in 1982 assayed 1.1% U3O9, (Geoscience Laboratories, Ontario Ministry of Northern Development and Mines, Toronto, Ontario).

The breccia fragments are predominantly quartz monzonite, and to a lesser degree, Sibley Group rocks, enclosed within a pyrite matrix. Pyrite rims the fragments and exhibits a zoning in grain size, with the coarsest grains in voids and cavities of the breccia (Photograph 7).

Pan Canadian Development Company Limited located a block of highly radioactive float, which is probably the same one described by Blair (1977): "A float, which assayed 33 lb/ton 1)303, was found by MW Resources in a valley forming a diabass linear, approximately 400 feet southwest of the Christianson Showing; this location sat 6+00W, 9+00S on Rio's grid. The float is subrounded, approximately one foot in diameter, quite heavy and composed of brown colored hematized breccia fragments. The boulder is identical in character to hematized breccia found along the Christianson fault; the fault is a likely source of the boulder but extensive drilling completed along the structure has not indicated similarly mineralized sections." Red alteration was described in the Pan Canadian Development Company Limited's drill logs but mineralization similar to the float was not. The float is composed of hematized rock fragments set in an earthy hematized matrix. The rock contains vugs, filled with calcite and a black mineral. An autoradiograph indicates intense radioactivity is associated with the black mineral (pitchblende). In their assessment work report, Pan N

LEGEND 1

U Uranium py pyrite cp chalcopyrite sp sphalerite gn galena i

Map 6. Uranium Occurrences - Greenwich Lake Area (Carter, 1979) $7

Canadian Development Company state that much prospecting in the vicinity of the area in which the float was found "gave no clue whatsoever as to its origin".

Many authors have consistently stated that the veinrtype uranium occurrences are located in north-northwest-trending structures; however, the series of uranium showings formerly held by Univex is in northeast-trending lineaments. This lineament may form a conjugate set with the Christianson Fault.

Other minor uranium occurrences have been described in the Greenwich Lake area by exploration company personnel and these descriptions are available in the Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario. Carter (1979) gives a location map for the uranium occurrences, which is reproduced as Map 6 in this report.

Figure 3 illustrates a possible sequence of events that has led to the uranium occurrences at Greenwich Lake. A possible key to the rich epigenetic deposits would be location of the Sibley Group algal mats that would have been a good source of H2S gas required to precipitate the uranium from solution. CONCEPTUAL FORMATION OF URANIUM DEPOSITS GREENWICH LAKE AREA

Tho guetico ftolt motaiodimontary pockaqo WAS »igwtizod and Momomto stocki• Uranium in tho ntotascdinenti was ruwobiluod into coarso-qraincd dlbi to paqvat i tos . A period at weatherinq and paneplanation followed. A palosol was dovolopud.

II Oopovition of the Middle Proca»br and Late Prccaabnan rocks in J uranium ««rl«(iin«iit tran»qrc««ive basin aodificd, roworkedj or removed the palesot. Palosot was locally preserved in

liydrduLLC

One poHBible chvBical trjp would bo Lhe Jlqal Mats ol the Guntlint

chert hydro^uarbun-rich ncdial unit ol the Hossport Porn«itton ISit)lcy Group).

\\,

ttrosion ol Stbtoy Croup racks from portions ol the baat

Greenwich I-ikc Arra. Type A: UraniuM concentrations in miqa^tized sodtwonta "quartz-sweat" i>t:qmati tus. TyfM* ttt tjraniuin in albttic pt^^Mio t Ltos luraninite * ^ipa (pitchblende • pyrito • hcMititel.

Figure 7 S3 INNES LAKE-GOODMORNING LAKES AREA

Location & Access: The area is located in northwestern Dorion Township, approximately 55 km northeast of the City of Thunder Bay. Access is by an all-weather gravel road that intersects Highway 11/17 approximately 65 km east of Thunder Bay. The showing is located 4 km south of Innes Lake (52A15/SE) and 4 km west of Ouimet Canyon.

Ownership: The principal showing is situated on former claim TB457188, located in the SW*j of the W% of Lot 9, Concession XI in Dorion Township. John Ternowesky of Thunder Bay was the last recorded owner; claim TB457188 reverted to the Crown on May 10, 1983.

Mineralization: Mineralization consists of uraninite in pegmatites and uraniferous fluorapatite in the fault zone (Yule 1979).

Geology The geology of the Dorion-McTavish Townships area hes been described by T. L. Tanton (1931), J. E. Hawley (1929), W. H. Mcllwaine (1972, 1973), L. A. Tihor (1973), and G. R. Yule (1979). Company assessment work on various properties is on file with the Resident Geologist's Office in Thunder Bay, Ontario.

Two main types of uranium mineralization occur in the area. Syngenetic deposits of uranium occur in fresh, relatively unaltered pegmatite dikes, and epigenstic deposits occur in brecciated, hydrothermally altered rocks associated with the Goodmorning Lakes Fault Zone (Yule 1979).

In the Innes Lake-Goodmorning Lakes area, the Quetico Belt migmatitic rocks contain uranium-bearing pegmatites. These occur just SW of Innes Lake in the area of Lot 13, Concession XI, Oorion Township. The pegmatite dikes are irregular in shape, elongated in an east-west direction, and more or less parallel to the regional strike of the migmatites. The dikes tend to pinch and swell along their strike direction. Some pegmatite pods are up to 200 m long and perhaps up to 120 m wide. Actual contacts are usually well defined. Gneissic xenoliths of country rocks in various stages of assimilation are often seen within the pegmatites.

The pegmatites are medium to coarse grained and white to greyish white in color. Mineralogy of the dikes appears to be simple: feldspar (albite), quartz, biotite i apatite + accessories such as zircon. Secondary uranophane is often seen on fracture surfaces. Highest radiation as detected with a McPhar TV-1 gamma ray spectrometer is invariably associated with the more mafic sections of the pegmatites. Approximately thirty trenches were blasted in the pegmatite zones in 1968, and grab samples ranged up to 0.18% uranium (John Ternowesky, prospector, Thunder Bay, personal communication, 1981). One sample collected by the author analysed 160 ppm uranium and 800 ppm thorium (Analysis by Geoscience Laboratories, Ontario Geological Survey, Toronto, Ontario). (*': LEGEND **••-• It'

, sflncinc MZCCM Trai tomnnUkrOoad

) K>% - ^~ SYMBOLS ALTIM> MMZOWfK

I (. -"ll OUTCROP AREA 4I.TXW* tstntihtati tUAnrt «) bW l*n fMx [ //I GEOLOGCAL CONTACTS r«9H «UMTZ MCHZONIT* TRENCH

Map 7. Geology of the Goodmorning Lakes Radioactive Breccia Zone XIII IX VIII Pb.Zn

WESTERN DORION TOWNSHIP 0 0-5 1 15 2 miles SCALE 1.31,680

Map 8. Mineral Occurrences, Western Dorion Township Photogrpah 9. Quartz-hematite breccia, Goodmorning Lakes Fault Zone, Dorion Township. Radioactive pegmatites of this type occur elsewhere in the region at Greenwich Lake, Lake Helen, Trottier Township, in the Longlac area and at Tennant Lake, north of Nakina.

The epigenetic deposits in the Innes Lake area are associated with the Goodmorning Lakes Fault Zone. The main trenches are located on claim TB457188; additional trenches are located southeast of a small lake in NE^ of the EH of Lot 10, Concession Xll, Dorion Township. Map 7 depicts the geology of the fault area , and Figure 9 illustrates a possible relationship between the elements of the Goodmorning Lakes occurrence. This property was mapped in detail by Yule (1979). The following, unless otherwise noted, is taken from his study: "The outcrop where the trenches are located has been stripped of overburden for an area measuring 150 m x 80 m. A large breccia zone marks the location of the Goodmorning Lakes Fault zone within the stripped area. The breccia zone is 40 m wide in the southeastern section of the outcrop and narrows to approximately 20 m in the northwest section of the exposure. Hydrothermally altered quartz monzonite envelopes the breccia zone. There is a gradational decrease in the intensity and type of alteration as one progresses outwards from the breccia zone. All mappable units exhibit some degree of quartz veining but the core of the breccia unit is characterized by a highly silicified zone".

Six map units have been defined: Unit Lithology 6 Quartz Stockwork - having greater than 50% milky quartz as veins or as a massive vein. 5 Sericitic Quartz Breccia - light green sericitic altered fragments with a matrix of milky quartz. 4 Hematitic Quartz Breccia a) less than 50% quartz fragments in a hematitic matrix. b) greater than 50% quartz fragments in a hematitic matrix. Hematized Quartz Monzonite a) lightly sericitized (less than 50%) feldspars b) heavily sericitized (greater than 50%) feldspars

Sericitic Quartz Monzonite a) lightly sericitized (<50%) feldspars b) heavily sericitized (>50%) feldspars

Unaltered quartz monzonite

All the map units are altered to some degree; the degree

of alteration is graphically illustrated in Figure S.

The alteration of the quartz monzonite host rock is pervasive

and three alteration types are distinguishable: 1. dark

green chloritization; 2. red hematization; and 3. pale green

sericitization.

Minor chloritization of biotite is common to the area, but the dark green* chloritized, quartz monzonite is only found within the unit 3 alteration halo and is attributed to fluid alteration associated with the fault zone. With increased chloritization, ferric iron increases at the expense of ferrous iron (Munrad 1974), while total iron remains constant.

Plagioclase feldspars are clouded by iron oxide; hematite occurs as trapped grains in cleavage planes of mica and red coloration becomes dominanc. Tourmaline occurs as light blue fracture fillings and was introduced at the same time as the hematization event.

The light green sericitization zone is situated in the middle of the breccia, where it has overprinted the hematized quartz monzonite. Mineralogy of this zone is similar to the altered quartz monzonite but all primary rock textures have been destroyed. Hematite is absent. ALTERATION VS DISTANCE FROM BRECCIA MMROtCO'lC CSTIMATCS

l •» •i»IH« n — —.^— Svnclllutlcii *f ftl4%f*rt

— —. — H«ai*titlt«tU* «f *•!«•«•'•

ITl IOI 't *o so *o ir IT 10 enriaec * V 5

ALTERATION VS DISTANCE FR OM BRECCIA KTHOLOGIC CSTIMATKt

100

1 f 1

I

1 r J / V '

' I C

y ; • X 30- —— ....-••• \ ! •

•• - - *

• —•"••' •- —-•'•* O |

14* IS 171 IW r* 40 »0 40 27 17 10 It* D'lTlUCI 1*1 rouct 1379}

Figure 8 Alteration vs. Distance from the breccia zone Goodmorning Lakes Fault Zone From petrographic studies, Yule (1979) has indicated a diffuse hydrothermal alteration zone to be present as an envelope surrounding the breccia zone. Within 50 m of the breccia, biotite is strongly chloritized; within 170 m plagioclase is sericitized. K-feldspar does not appear to be sericitized.

Mineralization A detailed ground radiometric survey conducted on a 5 m grid using a McPhar TV-1 differential gamma ray spectrometer delineated zones of radioactivity caused by uranium within and along the contact of the hematitic quartz breccia. Analysis of grab samples revealed that the mineralization is rather erratic.

Autoradiographs of slabbed hematite-quartz breccia clearly illustrate that anomalous radioactivity is concentrated in late fractures containing remobilized, fine grained, hematitic material. Because of the exceedingly fine grained nature of the mineralized areas, optical indentification of the radioactive mineral was not possible. X-ray diffractometer scans, before and after heating, failed to identify the uranium-bearing materials.

Metamictization of uranium mineralogy probably was complete. X-ray scans indicated the presence of fluorapatite, illite and quartz (Yule, 1979). Anomalous P2Q5 values are associated with the mineralized samples. X-ray fluorescence peak height analysis for both mineralized and unmineralized samples was conducted by Yule (1979) to estimate relative proportions of uranium, phosphorous, and calcium in the samples. Unmineralized samples contain traces of uranium, but the uranium is not associated with apatite. An association with clay minerals is more probable. In mineralized samples, there exists a high correlation between concentrations of uranium and phosphorous that suggests that the uranium occurs in association with apatite or an unidentified uranium phosphate mineral.

Yule (1979) gives the following summary: "A detailed evaluation of the Goodmorning Lakes radioactive fault breccia has resulted in several conclusions: 1) The Goodmorning Lakes Fault, characteristic of early Keweenawan fault and fracture systems, represents the major structural control of uranium mineralization. 2) All mineralization within the Goodmorning Lakes breccia pre-dates the late Keweenawan N60°E tensional fracture set. 3) Uranium deposition of Innes Lake appears to pre-date local lead-zinc-barite veins. 4) Hydrothermal solutions moved through the fault system, and caused wallrock alteration which includes chloritization, hematization, sericitization and silicification. 5) Hydrothermal alteration and accompanying tourmalinization are early stage events in history of the vein system. 6) Silica gangue mineralization includes as three phases of silica cementation; a milky, a cherty, and a crystalline quartz phase accompanied by several phases of brecciation. The resultant deposit is a complex stockwork. 93

7) Passive fracture-filling is indicated by characteristic textures such as comb-structures and miarolitic vugs. 8) Radiometrio surveys indicate that the radio- activity is due to uranium. 9) Uranium mineralization occurs in late fractures within the hematitic quartz breccia. 10) Anomalous concentrations of P2O5 are found associated with uranium as a fluorapatite mineral species. 11) Uranium is most probably fixed as uranium fluorapatite', replacing a calcium lattice site in calcium fluorapatite. 12) Analysis of total iron content of the hematitic quartz breccia and relatively unaltered quartz monzonite wallrock indicate no change in concentration, consequently only the oxidation state of the iron changed during hydrothermal alteration. 13) Quartz monzonite is a good source of leachable uranium. But analysis of wallrock of the Innes Lake breccia do not support a theory of lateral derivation for the metals. 14) Phosphate for the apatite was not derived by wallrock depletion as indicated by wallrock geochemistry. An alternate source of large concentrations of P2°^> is required and may be the same one which also supplied apatitic uraniferous pegmatites found nearby. 15) The ease with which uranium fluorapatite releases uranium in the presence of humic acid activity tend to suggest that surficial leaching and supergene enrichment of mineralization at depth is a viable possibility for the Innes Lake occurrence." Qvartt-Hamatlt* lanaa L«k« tiaeela • a«matlt«a

•Iteration

lner»aalnt ohlorltliatlcn «f klatlta ** Oaarti-HanatlU •raccla lnoraaaln« earloiiliatlen el Blaaloalaaa Ineraaalm ••rleltltallen et K-laM«»ar Incraaalnt liamatlllxatlon ol taldasara Altarttlan mtaitalty

•HUllloalUn 2anat

5 KM

Figure 9. Schematic section of the Goodmorning Lakes Fault Zone. TABLET•• Analysis of Grab Samples from Hematite Brecc:\ Goodmorninq Lakes Fault Zone Sample U3<>8 ThO2 Resident Geologist's Number ppm ppm Pile Number 1 79 2 633 3 114 4 57 5 7.5 6 65 7 0.57%(c) 0.003% F-33-78 8 0.034%(c) 0.004% P-34-78 9 0.13%(e) P-63-77 10 75 50 P-57-77 11 95 10 F-56-77 Samples 1-4, analysis by Geological Survey of Canada, Ottawa, Samples 5-11, analysis by Ontario Geological Survey, Toronto. Analysis 1-6, published in Yule (1979). (c) chemical analysis; (e) equivalent radioactivity. ENTERPRISE MINE

Location & Access; The Enterprise Mine is located in Lot C, McTavish Township, and can be reached by following a bush road that intersects Highway 11-17 approximately 2.5 km east of Pearl, Ontario. The old mine site is located about 0.4 km east of the intersection of this road and the CNR tracks. The reader is referred to Ontario Geological Survey Map P721 for detail location.

Ownership: The mine site has been staked by William Forsgren of Murillo, Ontario.

Mineralization; Galena, chalcopyrite, pyrite, azurite, malachite, gold, silver, coffinite, calcite, quartz and amethystine quartz, and barite occur in the vein system.

Exploration and Development History: Tanton (1931) gives a brief history of the Enterprise Mine: "The abandoned workings of Enterprise Mine are on Mining Lot C, McTavish Township, on the north side of the Canadian National Railway about 2k miles southwest of Ancliff Station (see Map 214A). A well-mineralized vein was discovered on this property in 1865 by Mr. Peter McKellar. Dr. E. J. Chapman of Toronto in 1868 reported the presence of appreciable quantities of gold and silver associated with the galena and chalcopyrite in parts of the vein. Between 1870 and 1876 two shafts were sunk. No. 1 was sunk to a depth of 180 feet; levels were run easterly 76 feet and westerly 66 feet at a depth of 60 feet; a stope was made in the west drift, and a winze was sunk 14 feet in the east drift about 50 feet from the shaft. A large sump was constructed on the northern wall of the shaft at the 60-foot level to catch surface waters. A crosscut was made from the bottom of the shaft going IS feet south. Shaft No. 2 was sunk 60 feet at a point about 300 feet west of No. 1.

The total recorded production from the mine was a single shipment made to Swansea, Wales, in 1875. The ore packed in barrels was drawn by ox team over a tram to the loading dock on Black Bay about 5 miles east of the mine. The returns were as follows:

142 tons 39.5 percent lead 15 tons 33 percent lead 10 tons 14 percent lead

No returns were made nor credit given for any gold, silver, or copper in the shipment.

In 1874, Dr. E. J. Chapman reported that a large average sample of the well-mineralized part of the vein near surface gave the following result upon analysis:

Lead 41.84 percent Copper 5.40 percent Silver 3.2 ounces per ton Gold 0.33 ounces per ton

He stated that the gold in the ore was contained in the chalcopyrite.

Mining operations ceased in 1876 and a few years later all the buildings and surface works were destroyed by fire. The ownership of the property changed hands, and the new owners dewatered and sampled the workings in 1884. No ore was produced.

In 1926, the property was acquired by Mr. J. A. Jacobs, who sold it to the Power and Mines Corporation Limited, of which he was then president. Under the management of J. H. Johnston, new buildings were constructed and shaft No. 1 was dewatered. The examination having been completed the operation was suspended in 1927.

Mining Lot C is partly underlain by nearly flat- lying sediments of the Sibley series up to more than 40 feet thick, resting on an undulating basement of pink granite. Various members of the sedimentary series, namely, conglomerate, sandstone, finely laminated chert and limestone, and red tuff, successively overlap each other and come in contact with the granite which rises as a hill in the northern part of the lot. A diabase dyke 4 feet wide occupies a fault, striking south 83° east, through the sediments and granite; the dyke is exposed at No. 2 shaft and in the railway cut about 100 feet south of shaft No. 1. Faulting occurred after the diabase intrusion. The cavities and fissures formed during the faulting are cemented with vein material. Several mineralized veins are known to occur on Mining Lot C; the largest and best mineralized is that which has been mined. This vein has an average width of 4 feet with numerous branches ramifying through a shatter zone for 3 feet on either side. Its length as traced underground is 150 feet. Other veins, which may have some connection with it, have been found beyond drift-covered area in this vicinity. It is reported that in shaft No. 1, 180 feet deep, the vein pinched out or became very narrow at more than one place and that at the bottom of the shaft it was from 5 to 7 feet wide. The strike of the vein varies between north 65° east and north 70° east; the dip is 75° south in the upper part of shaft No. 1, but more nearly vertical at depth.

The vein consists of calcite and white quartz with local concentrations of intimately associated, fine-grained galena and chalcopyrite, and a later filling of amethyst and pink barite. Gold and silver values were found upon assay. Rich concentrations of metallic minerals were found as discontinuous lodes within the vein at various places throughout the workings. The largest concentration found was that which outcropped at shaft No. 1. With the exception of a small tonnage of rich lead-copper ore near the surface of the vein and on the dump, the greater part of the known richly mineralized material was removed during the early mining operations.

The other veins exposed on Mining Lot C are less than a foot in width and though of the same character as that at the mine, are either sparsely mineralized or so narrow where well mineralized, that they could not be profitably mined. A further search for lateral extensions of the principal vein along the main fault would be warranted."

Geology;

Franklin (1970, 1978), Franklin and Mitchell (1977), and

Mcllwaine (1971b) have interpreted the geology of the

Enterprise Mine. Franklin (1970) gives the following description:

"The Enterprise vein was traced underground for 150 feet (Tanton 1931), and has an average width of four feet. The Canadian National Railway line from Nipigon to Port Arthur cuts through the vein system, exposing an excellent' cross-section of wallrocks for a length of 500 feet. The vein system, where intersected, consists of several calcite and quartz stringers, ranging up to five inches wide, spread over a width of 40 feet.

Approximately 4Q feet of Sibley Group sediments onlap into a hill of Archean granite.

The basal Sibley, at its contact with Archean rocks contain a few well rounded granite boulders, in a well indurated, buff to white sandstone matrix. This contact is overlain by up to 25 feet of sandstone. The sandstone thins rapidly as it onlaps the Archean. It is overlain by interbedded sandstone and mudstone, typical of the upper part of the sandstone unit or lower part of the mudstone unit. Red mudstone onlaps further onto the granite hill than the underlying coarser clastic unit, indicating greater transgression with time. Chert-carbonate alteration of the Sibley rocks similar to that at the Droion mine is also evident at the Enterprise Mine."

Figure 10 illustrates a geological cross-section along the

Canadian National Railway tracks at the Enterprise Mine, and Photo- grapn 3 illustrates the unconformity at the Enterprise Mine.

Radioactivity at the Enterprise Mine was first documented by

Fenwick and Scott (1977). Although no specific location is given, Ruzicka (1976) reported values up to 540 ppm ur- anium in Sibley Group rocks southwest of Nipigon. Grab samples collected by the author were analysed (Table 7) for uranium, thorium, lead, zinc, copper, gold and silver.

Uranium analyses ranged from 0.02% to 0.06% U3O8. loo

Traces of nickel and cobalt were also present; high lead

content interfered with the thorium determination. All

analyses were done by the Geoscience Laboratories,

Ontario Geological Survey, Toronto.

Campling (1973) describes a thin (0.8 cm) zone of weathering

at the contact between the quartz monzonite and the Pass Lake

Formation. Thin section work has determined that feldspars

in the quartz monzonite near the unconformity have been

sericitized and altered for at least 2 m below the unconformity.

Three mineralized samples were sent to the Geoscience Laboratories,

Ontario Geological Survey, Toronto, Ontario, for investigation.

Their report is as follows: "The radioactive minerals in these samples are secondary in nature. The greatest concentrations of radioactive material rims or is otherwise spatially associated with the sulphide minerals, pyrite, galena, chalcopyrite and their secondary weathering products, principally limonite and anglesite.

X-ray powder patterns run on material extracted from these areas and from superpanned heavy concentrates from each sample have not been adequate for the identification of the radioactive minerals.

A reddish-orange glassy mineral frequently associated with hot spots on the auto-radiograph has been identified by x-ray powder camera as anglesite (PbSC>4). The association, unusual colour, and variation in the relative intensity of some x-ray lines of anglesite from accepted intensity patterns, suggests the possibility of substitution of a radioactive element in this phase.

Our investigations of these samples indicate that the radioactive mineralization was by means of radioactive element bearing solutions percolating through the rock during oxidation (weathering), deposition occurring in the reducing environment immediately adjacent to the sulphides." 50 100 (Overburden ]| Sandstone

Diabase Transition zone

Mudstone Quartz monzonlte ft** rnnkta «•?•!

Figure 10. Cross-section along CNR tracks. Enterprise Mine, McTavish Township. TABLE 8

Enterprise Mine Analysis:

Sample U308 Cu Zn Pb Au Ag Number (%) ill ILL (oz/Ton) (oz/Ton) 1 0.03 5.64 22.5 2 0.04 6.16 22.6 N/A N/A 3 0.04 5.68 27.9 N/A N/A 4 • 0.06 3.20 13.8 N/A N/A 5 0.026 0.90 38 7.4 Trace 0.10 ppm 6 0.043 0.224 64 4.0 Trace 0.28 ppm

N/A » not assayed. *Analysis by Ontario Geological Survey, Geoscience Laboratory, Toronto. 103

DORION AMETHYST MINE

Location & Access; The Dorion Amethyst Mine is located in the SE^ of Lot 3, Concession I of McTavish Township. Access is by means of a gravel road that intersects Highway 11-17 approximately 8 km east of Pearl. The mine site is shown on Geological Compilation Map 2232 of the Ontario Geological Survey as a copper-amethyst showing located 5 km northeast of Pearl, Ontario. On OGS Preliminary Geological Map P721, it is designated as property No. 24.

Ownership: The property is currently owned by Mr. Ted Williamson of Thunder Bay, Ontario.

Mineralization: Min-exAls of economic importance that occur on the propertv are chalcopyrite, malachite, azurite, pyrite,•calcite and amethyst, plus an unidentified uranium mineral.

Exploration and Development History: The property was originally staked as a copper prospect. Roy Barker drilled 13 diamond drill holes in 1967 to evaluate the copper mineralization. When Barker dropped the option, the property reverted to Williamson who then promoted the property as an amethyst mine. The vein has produced some exceptional amethyst crystals. Barker's drill core is no longer available for study, and to date no development work, other than some stripping and blasting to expose the amethyst vein, has been done. I Of

Geology: The geology of McTavish Township has been described by Tanton (1931), Hawley (1929), and Mcllwaine {1971a, 1971b, 1972).

At the Dorion Amethyst Mine (Map 9), Sibley Group mudstone and sandstones of the Rossport Formation lie unconformably on Archean quartz monzonite.

Barker's drilling outlined a "breccia" zone near the unconformity. Ten of the thirteen drill holes drilled by Barker in 1967 were drilled into the quartz monzonite. The unconformity has been described in the logs as a "hybrid granitic breccia with leached xenoliths with stringers and seams of sulfides and chlorite". This zone crops out just north of the calcite-amethyst vein on the property, and consists of highly altered fragments of granitic rock imbedded in a matrix of clay and sand. This "breccia zone" represents a pre-Sibley weathered surface. The unit contains finely disseminated pyrite and is stained by a rusty gossan.

Immediately overlying this weathered horizon are brecciated mudstones of the Rossport Formation. At the Dorion Amethyst Mine, this unit is charged with chalcopyrite and an unidentified radioactive mineral. Analysis has indicated up to 160 ppm uranium and over 8 percent copper.

The mudstone unit is fine grained, tan to dark reddish brown in color, and massive. Bleaching has occurred along numerous fractures throughout the outcrop. 105

•am

t MM* «• •• MM

Map 9. Geology of the Dorion Amethyst Mine, McTavish Township. A spring has its source at the unconformity and emanates from the vein system as well as from a diamond drill hole. This spring reinforces the concept of an active plumbing system. Minor galena and sphalerite were noted in the vein system at the Dorion Amethyst Mine.

The calcite-amethyst vein terminates in the mudstone unit. Within the mudstone, and on strike with the calcite-amethyst vein, there are numerous calcite-filled fractures. The calcite vein is not exposed immediately west of the stripped area. Further west and on strike with the main vein, a similar calcite-amethyst vein is exposed in a cliff on the west side of the trail (Map 9). This may be an extension of the main vein.

An examination of the property with a McPhar TV-1 gamma ray spectrometer in 1978 indicated that the copper-rich zone was radioactive. Highest readings were obtained from the chalcopyrite-impregnated, brecciated Rossport Formation. One grab sample yielded 160 ppm uranium and 8.16% copper. 107

BLACK STURGEON LAKE-SPLIT RAPIDS DAM OCCURRENCE

Location & Access; The property is situated northeast of Black Sturgeon Lake (NTS 52H7/SW), 8.5 km along a gravel road that heads north from the old Split Rapids dam site at the outlet of Black Sturgeon Lake.

Ownership: The property is currently owned by Uranerz Exploration and Mining Corporation Limited.

Economic Mineralization: Fracture zones with very high radioactivity occur on the property (Sutcliffe 1981; Scott 1982). Pitchblende, pyrite, malachite, chalcopyrite and uranopilite occur in the veins. Silver was present in one sample. Brannerite occurs in pegmatites adjacent to the showings (V. Ruzicka, Geologist, Geological Survey of Canada, personal communication, 1983).

History; The occurrence was initially discovered by R. H. Sutcliffe in the course of field work for the Ontario geological Survey in the summer of 1981. The showing was subsequently described by the author in the Resident Geologist's Annual Report for 1981 (Mcllwaine et al. 1982). The property was then acquired by Uranerz Exploration and Mining Corporation Limited, which stripped an area measuring 110 m x 40 m and did geological, magnetometer and radiometric surveys on the property. Two trenches were blasted at the main showing area. Values of up to 12% l^Og were obtained I OS

by Uranerz Exploration and Mining Company Limited (Y. Gariepy, Geologist, Uranerz Exploration and Mining Company Limited, personal communication, 1983). A suite of samples was sent to V. Ruzicka pf the Geological Survey of Canada in November, 1982.

Geology; The area was mapped by M. E. Coates in 1967 on a reconnaissance basis in the course of work for the Ontario Department of Mines. The iron formation was noted, as were the pink myrmekitic pegmatite dikes; however, no mention was made of radioactive fracture sets cutting the iron formation.

The stripping (Map 10, ) has exposed a conformable sequence of metagreywacke, meta-iron formation and amphibolite that has been intruded by pink, coarse grained, myrmekitic, radioactive pegmatite dikes. The sequence strikes 065° and dips 65°S. A small dioritic plug occurs in the central portion of the exposure. The sequence is faulted and fractured; radioactive shears form conjugate sets that cross-cut the exposure. Within the shears, the highest radioactivity, as determined with a McPhar gamma ray TV-1-spectrometer, is restricted to areas where the fracture systems cross the iron formation. True widths of the metagreywacke and amphibolite could not be determined; the iron formation has an exposed width of 8 m and a true width of approximately 7.3 m.

The iron formation is characterized by recrystallized magnetite, amphibole, large reddish-brown garnets and traces of pyrite. ROAD TO SPLIT RAPIDS DAM,

BLACK STURGEON LAKE. 8.5 km 1pm 2pm 3pm 4pm 5Qm 6Qm 7pm 80m 9pm 100m 110m

suit oreccla Approximate (non-radioactive) of

sand and water

LEGEND

* I V I '»*• •"» ••"#• I * I ••••• ••• • •> "•»»! ••!«.,.,. SCALE P $ 1.0 15 2.0 / * •IIANOMOMTIt aftawa* METERS

PaaHi •kaat u»u* ••If wACRfi ft*****, at»r aa*l«hi ftiMk t i«aa IMn I UMMIta*

MOM PONHATKWi •ala«*«ak«a»«{ a«afa» • aa«M • all* i o l«a: • 1 aaalal •••alkala. attaM aain«a* >aciar*B*0 in" 1000 Jttf'NWOLlTl: aialavaltaala t*«b 100 •aa*l •a i

Map 10. Geology of the Split Rapids Dam Occurrence. f/U

The garnets occur as individual crystals up to 4 cm

across as well as aggregates of smaller crystals. The rock

unit is laminated, black to dark green in color and would

make a good marker horizon.

The metagreywacke is fine grained, massive, and buff to

cream in color. The unit contains wispy inclusions or

segregations of mafic minerals. The wacke might be partly volcanic in origin.

The amphibolite is dark green, coarse grained, and massive.

Amphibole crystals range up to 2 to 3 cm in length and constitute approximately 75% of the rock unit. The remaining

25% is made up of feldspar and quartz.

The highest radioactivity is confined to fault and fracture zones, the widest of which is 40 cm across. In most cases the radioactivity, as detected by the McPhar TV-1 gamma ray- spectrometer, was off-scale or nearly off-scale at most localities.

The fracture zones consist of felted masses of hematite, magnetite, a greenish colored rock flour, calcite, pitchblende and uranopilite (identification by Geoscience Laboratories,

Ontario Geological Survey, Toronto, Ontario). Analysis of several samples yielded results shown on Table 9.

Trenching by Uranerz Exploration and Mining Limited has revealed that the veins persist to at least a depth of 2 m, and, although still of high grade, remain narrow. •AMPLI An U TU NI CM Zn PU Numm ot/t os/t PPM PPM PPM ppm PPM PPM .Main •1JSU1* Tr 4700 Tr 10 ao •0 47 • 2 • 70 PU Main C1JSU14 Tr Tr 1000 10 sa iê 14 •7 170 Pit •tJtUi» 1 M Tr 10 •a •«0-1 Tr 10 «4 ft 1«1 10 •haan* • IJSlH* 0.» ai Tr Tr ••0 10 •• «• •«•-a 20 •4 7« Haaaal •tJ*W17 1 M •*••• Tr Tr ia 10 •4 a« • 4 »• 10 •Nana* IIJIU1I Tr Tr 110 «to N/D •no-* N/D N/D N/D N/D •a« •2JSU1» Tr Tr 4t00 10 24 74 • • • • • 8O Qra» •RD-0 Main •ajsuao Tr Tr •.•% • 0 • 2S • 4 20 • 7 • 2OO Pit Main •2J«U21 Tr Tr alto • — 70 2t • 9 *•• 11 Pit

•2JSU22 Tr t.to 440 10 20 10 a. io* *• 200 Pit

Table 9 Sugary of analysis of samples from the Split Rapids Dam Occurrence Photograph lu. Split Rapid Dam Occurrence; radioactive reddish- brown pegmatite. Figure ll. Autoradiograph of Black Sturgeon Split Rapids Dam Occurrence. Radioactivity is confined to the cross-cutting vein system. The pegmatites are very coarse grained, and pink in color.

The feldspars exhibit striking myrmekitic and graphic textures ,

Photograph 10.The northeastern exposure is radioactive and

is criss-crossed by small (<2mm) veinlets of hematite.

Veinlets strike 240° and trend beyond the pegmatite-greywacke

contacts. ¥. Gariepy (Geologist, Uranerz Exploration and

Mining Company Limited, personal communication, 1982) suggests

that the pegmatites are the source of the uranium.

The host rocks and the source rocks are probably Archean

in age. The age of the uranium mineralization in the fracture

systems was determined to be 1090 i 25 Ma (V. Ruzicka,

Geologist, Geological Survey of Canada, personal

communication, 1983). The fracture systems form a conjugate

set and are subparallel to the Black Sturgeon Fault System,

which is Late Precambrian in age. The presence of uranopilite

(identification by the Geoscience Laboratories, Ontario

Geological Survey, Toronto, Ontario) and its usual association

with gypsum (Dana 1951) imply that the mineralization might be

associated with the Sibley Group, which does contain gypsum.

On the other hand, the iron formation has a small sulfide

component and the sulfur necessary for the formation of the

uranopilite might originate from the iron formation.

A thin section was made of the fault breccia from Fit 1 at the Split Rapids Dam Occurrence in order to determine the nature of the light pink to reddish colored, fault breccia fragments. In thin section the fragments consist of aggregates of epidote, calcite and hematite, plus magnetite. //&

A well-developed reaction rim of amphibole separates the

fragments from the rock matrix.

The fragments exhibit a faint zonation of calcite and epidote.

As one traverses inward from the reaction rim through to the core and then back to the opposite rim, one progressively encounters epidote-calcite-epidote. No rock corresponding to the fragment lithology was found on the property. It is conceivable that these calc-silicates might represent carbonate rocks from the Sibley

Group that have been altered by metamorphism and incorporated in the fault system.

The matrix consists of a felted mass of amphibole, feldspar, disseminated magnetite and pitchblende. In plane light, the amphibole is light green, and larger crystals are pleochroic from dark green to light greenish-yellow. The amphibole occurs in small clusters of radiating fibrous crystal masses and probably is anthophyllite.

Magnetite occurs as interlocking superfluous blades, as disseminated grains throughout the rock, and as concentrations paralleling the amphibole reaction rims. Hematite occurs as discrete intergrain masses and as calcite grain coatings.

The radioactive mineral is pitchblende and it occurs in a subcircular or colloform form in gangue silicates (Photograph ID. The autoradiograph clearly shows that the uranium mineralization is confined to the fracture systems and is not contained within the iron formation (Figure 22).

Photograph j.1. Colloform pitchblende at photo centre circle diameter approximately 12 mm. in

JESSIE LAKE AREA

Location & Access:

•'The Jessie Lake occurrences are located in Purdom Township,

(NTS 52H1/NW), approximately 25 km north of Nipigon.

The main occurrence is situated on the southeast Bay of

Jessie Lake (Map 11) and is accessible most easily by

boat from the public landing point located 3.25 km north

of the Cameron Falls Dam. An Ontario Hydro tractor road

connects the various water control dams on the eastern bay

of Jessie Lake. The northern dam site is just over 0.4 km

south of the main showing.

The main showing is located on claim TB458330, but similar,

smaller veins occur on claims TB458405 and TB458328.

Ownership:

In 1977, the claims were held by Falconbridge. Nickel Mines

Limited. In 1983, there were no recorded mining claims on the occurrences.

Economic Mineralization:

Uranium mineralization is associated with a hematized fault zone. Minor galena, sphalerite, barite, fluorite and amethyst are also present.

History:

Portions of Jessie Lake are situated in an unmapped wedge that lies between the mapping of Pye (1965) and Coates (1972). JESSIE LAKE AREA PUROOM TOWNSHIP Seal* 1 : 50,000

N

Map 11. Uranium Occurrences in the Jessie Lake Area. The most recent geological work is that of Falconbridge Nickel

Mines Limited. The property was discovered and acquired by

Falconbridge in 1976, during field prospecting, using a

TV-1A gamma ray spectrometer. In January 1977, a 60 line-mile grid was laid out over the area; 53 line-miles on the lake

and 7 line-miles on the adjacent shore. The Falconbridge

Nickel Mines Limited program consisted of lake bottom geochemistry,

airborne radiometrics, EM-16 and Sharpe MF-1 magnetometer surveys.

Falconbridge Nickel Mines1 conclusions are as follows:

1. Other than a few isolated highs, Otter Bay is the only

geochemically anomalous portion of Jessie Lake.

2. The lineament extending south from Otter Bay. is geochemically

anomalous in uranium.

3. Geophysics failed to define any major structure underlying

Jessie Lake (this may be due to a thick layer of clay on

the lake bottom).

Geology:

The Jessie Lake area is underlain by Early Precambrian granitic rocks and migmatites that have been intruded by Late Precambrian diabase dikes and sills. Jessie Lake lies in a graben associated with Late Precambrian tectonic activity.

The geology of the principal showing (Number 1, Map 12) consists of a hematized fault or shear zone that cuts Archean granitic and migmatitic rocks. The "vein" strikes 110° and has a vertical dip. It has a maximum exposed width of 0.76 m and is traceable for a strike length of 224 m. The eastern extension trends into swampy terrain. The uranium mineralization Ulo

UMMIMI MCM HBtim HUI

rt:*«,*«t «pm T*: MOO TS:M

Map 1^. Geology of tne Jessie Lake Occurrence, Purdom Township. /a/

is situated in a shear zone and the shear zone is enclosed

in a hematite alteration envelope that extends up to 0.70 m

on either side of the radioactive zone.

Approximately 120 m from the lake and directly on strike with

the vein system, a xenolith resembling Gunflint Formation

taconite is incorporated within the zone. In hand sample,

the rock consists of small, closely packed, ovoid spheres that are about 2 mm in diameter. The rock is an earthy red color, reminiscent of taconitic ores. Hematite occurs throughout the rock as minute grains in the spaces between the spheroids. Although alteration within the shear zone has obliterated the internal structural of the spheroids, some concentricity has been preserved in a few grains, indicating that they may have been ooliths.

Fresh host rock at grid location 2+00E on the baseline is a pinkish granitic rock containing quartz, pink- feldspar and biotite. Biotite defines a weak foliation to the rock. The altered rock adjacent to the vein system has undergone intense chloritization, epidotization and hematization. Hematization is most intense immediately adjacent to the vein and progressively diminishes away from the vein. Fluorite and sphalerite are minor constituents of the vein system.

The zone tends to pinch and swell and in places exhibits an anastomosing texture. Minute hematite veinlets cut the host rocks and strike parallel to the main shear. Pnotograph 12. Jessie Lake Occurrence Outcrop

Handsample Samples for uranium analysis were taken from locations

indicated on the geological map (Map 12): values ranged up to 420

ppm uranium.

The hematite alteration in the shear zone is clearly demonstrated

in Photograph 12.

Description of Showing 2 - Other Veins in Jessie Lake:

The showing on claim TB458405 is situated just off the

east side of Highway 585, approximately 7.2 km north of

the Cameron Falls Dam site. The zone (2) is completely

hematized, is approximately 0.9 m wide and traceable along

strike for 90 m. The zone strikes 028° and dips vertically.

The rocks within the zone are mylonitized, contain abundant

red, earthy hematite and specularite, and are weakly radioactive.

Smaller or subsidiary veinlets can be found along the shoreline

directly opposite the public landing at Jessie Lake. These are

designated (3) and (4) on Map 11. The 8 cm barite-fluorite vein directly across from the public landing is weakly

radioactive. Approximately 320 m south along the shoreline there is a zone of deep weathering. Two subparallel shear sets occupy this zone. The shears are 46 cm and 25 cm wide, strike

125° and appear to be vertical. The granitic host rocks are weakly foliated, the foliation being defined by the alignment of biotite flakes. In the vicinity of the shear, the foliation bends toward the shear. In the northernmost shear zone, vugs and cavities are lined with small black quartz crystals.

Granitic rocks within the shear have been totally destroyed.

The hematitic mud micro-breccia in the southern shear is weakly radioactive as determined with a McPhar TV-1

15,000 cpm; T2: 500 cpm; T2: 80 cpm). The extreme weathered

nature of the shear made sampling difficult. Host rocks in

the vicinity of these shear, zones are granitic lit-par-lit

injections in Quetico Belt meta-sedimentary rocks.

Other Occurrences in the Purdom Township-Frazer Lake Area;

Uranerz Exploration and Mining Company Limited have located

several minor occurrences in the vicinity of the intersection

of the Purdom Township-Mclvor Township boundary with the

road to Frazer Lake.

All of the occurrences are associated with migmatitic and/or

hematized granitic rocks and are located near Malborne Lake.

The Malborne Lake showing (Number 5 on Map 12) consists of

a narrow (1 cm), high-grade, mineralized fracture that

contains pitchblende (?), plus secondary yellow uranium minerals,

probably uranophane. The showing is located on the northeast

shore of Malborne Lake about 125 m from the public landing

site. No samples were taken for analysis.

Other showings are associated with hematized fractures and seams in weathered granitic rocks. In addition, Uranerz

Exploration and Mining Company Limited has identified two radioactive boulder fields (Regional Geology Asssessment

Files, Thunder Bay, Ontario): one is located approximately

700 m north of Malborne Lake and the other is approximately

500 m west of Malborne Lake. Based on glacial striations, the prevailing ice direction in the area was from the NNE. PRAIRIE LAKE CARBONATITE COMPLEX

Location and Access;

The Prairie Lake Carbonatite Complex is situated on the north

shore of Prairie Lake, approximately 40 km northeast of Terrace

Bay and 4 0 km northwest of Marathon.

Access is by means of an all-weather gravel road that intersects

Highway 17 at Deadhorse Creek in Walsh Township. The Deadhorse

Creek forest access road crosses the western portion of the

complex at approximately the 32 km mark.

Economic Mineralization:

The Complex contains deposits of uranium, niobium, phosphate and

wollastonite. Drilling has outlined a uranium deposit containing

200,000 tons at 0.09% U3O3 and 0.25% Cb20s to 84 m (The

Northern Miner, May 3, 1979).

Exploration History:

During the summer of 1968, Newmont Mining Corporation of Canada

Limited was prospecting the area between the Killala Lake

Complex and the Port Coldwell Alkalic Complex for copper- nickel when Jim Gareau, prospector, came across several highly radioactive zones. A grid was established on the property and magnetometer and scintillometer surveys were conducted.

Preliminary results indicated that the Complex was zoned and that the outer ring was more radioactive and magnetic than the core. In 1969, detailed drilling and trenching delineated three lenses of mineralization: Jim's Showing, 14 North Hygrade, and the 900 North line 32A Showing.

Between 1968 and 1970, Newmont Mining Corporation of Canada completed an exploration program on the property that consisted of: 1. Linecutting on two grids? the first, a 400 foot grid over most of the complex, and the second, a 200 foot grid over the SW portion of the complex. 2. Radiometric and magnetometer surveys on both grids. 3. Geological mapping. 4. An orientation geochemical survey. 5. One thousand three hundred and seventy-five feet of trenching and channel sampling. 6. Fifteen Winkie holes for 1,742 feet (Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario).

In 1975-76, International Minerals and Chemicals Corporation acquired most of the Prairie Lake Complex and initiated an exploration program for phosphate minerals. Select sampling delineated up to 12% P2^5» ^ut drilling did not locate sufficient quantities for profitable extraction (Erdosh, 1976).

Also in 1975, New Insco Mines acquired several claims covering the uranium zones delineated by Newmont. An option agreement with I.M.C. (April 1976) gave New Insco exploratory rights on I.M.C. claims covering the complex. I.M.C. retained rights to any phosphates plus 10% of net profits after recovery of capital costs from any uranium or niobium ore discovered on I.M.C. portion of the complex. /sn New Insco proceeded with an exploration program that had the

following objectives (Sakrison 1977):

1. To determine if Jim's Showing was in fact truly delimited

on strike.

2. To locate additional concentrations of betafite.

3. To prepare an extensive diamond drilling program, and

conducts metallurgical sampling in 1977.

In 1975, Sage (1983) mapped the complex for the Ontario Geological

Survey; Sado and Closs (1982) conducted geochemical studies on the complex, also for the Ontario Geological Survey, as part of a province-wide assessment of alkalic and carbonatite complexes.

General Geology;

The Prairie Lake Carbonatite Complex was mapped for Newmont

Mining Corporation of Canada Limited in 1969 by D. H. Watkinson of Carleton University. The geology of the complex is shown on OGS Map H070 by Sage et al. (1976). The following is from Sage (1983 ) :

"The Prairie Lake Carbonatitic-Alkalic Rock Complex forms a circular topographic high west of Prairie Lake. The complex consists of a complexly inter- fingered sequence of arcuate to curvilinear bands of carbonate rock and pyroxene-nepheline rocks of the melteigite-urtite series collectively referred to as ijolite. The melteigite-urtite series are gradational into each other and thus the rocks are classed in a group as ijolites and are the intermediate member to the series and, by far, the dominant rock found in the core of Prairie Lake carbonatite. The carbonatite rocks are more abundant towards the periphery of the intrusion, and the ijolitic rocks towards the core. The carbonatite rocks are predominantly composed of calcite but minor amounts of dolomite are locally present. The age relations between the calcitic and dolomitic phases are uncertain. The calcite carbonatite rocks are medium-grained and contain minor quantities of fine-grained accessory magnetite, pyrite-pyrrhotite, amphibole and biotite- phlogopite. Locally the calcite is coarse-grained and visually appears to be nearly pure, probably having formed during a later pegmatitic phase of development. In some areas of the complex, a rusty weathering, ferruginous calcite locally appears to be younger than the non-ferruginous contacts with the non-ferruginous carbonate. The ferruginous calcite is generally medium- to coarse-grained and, in the field, is characterized by the presence of a limonitic coating on the weathered surface. This ferruginous carbonate may be ankeritic to ferruginous dolomite in composition. Trace amounts of dolomite are not uncommon within the sovites and ijolitic rocks . At "Jim's Showing" dolomite is the dominated carbonate phase in the mineralized zone and contains xenolithic fragments of other rocks found within the complex. The ijolitic rocks comprise most of the Prairie Lake complex and visually can be roughly divided into three phases. Contact relations between the various phases were not observed in the field. Along the margins of the complex, one phase consists of fine-grained ijolitic rock composed predominantly of biotite-phlogopite, calcite, magnetite and minor nepheline (Map Unit 2c). This phase is intimately associated with the carbonate rocks. The carbonate and ijolitic phases display both gradational and cross-cutting relationships. Where cross-cutting relations exist, the carbonate phase is always the younger. In the north a» i northwest corner of the intrusion, a second phase consists of a number of small exposures of medium- to coarse-grained ijolitic rocks containing abundant interstitial wollastonite. Wollastonite is also abundant in nepheline-rich, coarse-grained pegmatitic segregations found within finer-grained phases. The pegmatitic segregations may contain up to 50 per cent wollastonite and are composed almost exclusively of nepheline plus wollastonite. Black garnet, biotite, and calcite are common accessory minerals in this ijolitic group. In the south to southeast corner of the complex, exposures of generally medium- to coarse-grained ijolite with minor or no wollastonite compose the third ijolitic phase (Map Unit 3b). Pegmatitic phases- are common and locally coarse-grained pegmatites of nearly pure nepheline (urtite) can be found. Black garnet, biotite, and calcite are common accessory minerals. The relationship between the wollastonite-poor and wollastonite-rich ijolitic rocks is unknown due to the lack of critical outcrop exposure, but they may be gradational into each other. The complex displays a strong circular magnetic anomaly on ODM-GSC aeromagnetic map 2148G. The Prairie Lake complex lies within the Wawa Subprovince of the Superior Province (Ayres e»t al. 1970) and has been dated as being 1033 + 59 my old by the Rb-Sr isochron method (Bell and Blenkinsop, I960)."

Mineralization:

Uranium mineralization in the carbonatite coirplex is associated

with pyrochlore and betafite. Analysis of pyrochlore from Jim's

Showing by D. H. Watkinson yielded an average for five samples

of 13.63% TiO2, 25.50% U308, and 27.30% Nb205 from the pyrochlore-rich pyroxenite. Five analyses of pyrochlore from

the carbonatite component yielded an average of 4.82%

15.55% U3O8/ and 21.12% Nb205. Other samples yielded values as high as 65.52%

The property was dropped because of the apparent small size of the deposit, the uncertainty of the niobium market, and the foreseeable metallurgical problems associated with the extraction of uranium from pyrochlore.

In 1976, International Minerals and Chemical Corporation (Canada)

Limited conducted a mapping and sampling program coupled with a shallow drilling program, using reverse circulation equipment with double-wall drill rods. Three holes were drilled to test the overburden for possible residual deposits of apatite and to test the bedrock.

Results of the program were discouraging, as the carbonatite complex proved to be low in apatite, ranging between 4-6%

(Erdosh 1976). Nuinsco. Limited re-evaluated the complex /3o

in 1983-1984 as a source of wollastonite for ceramic purposes.

A 5,000 foot drill program is contemplated. Drilling in

1977 indicated a large, open pittable deposit of up to 25% wollastonite (The Northern Miner, November 3, 1983, p. 16). 131

DIATREMES

A group of five diatreme breccias occur along the north shore

of Lake Superior between Schreiber and the west margin

of the Port Coldwell Alkalic Complex. These are the Gold

Range, the Slate Island Group (17), the Neys diatreme on the

west shore of Coldwell Peninsula, the McKellar Creek diatreme

and the Deadhorse Creek group (4). Sage (1982) has described

their general geology and the mineralization associated with

them.

Of these diatremes, only the ones at McKellar Creek and the

Deadhorse Creek were found to be radioactive. The reader

is referred to Sage (1982) for descriptions of th?> diatremes.

The McKellar Creek Diatreme;

The McKellar Creek Diatreme can be reached by following a

trail that intersects Highway 17 just west of the highway

bridge over McKellar Creek in Walsh Township. . The diatreme

is approximately 300 m north of the highway and is exposed

at the eastern edge of a recently logged area.

Geology:

The outcrop pattern of the diatreme suggests a north-south axis of 240 m and a maximum width of 60 m (Sage 1982).

The breccia intrudes fine grained Archean metasediments.

Walker (1967) mapped the area for the Ontario Department of Mines and interpreted the diatreme to be "Animikie

Conglomerate"; however, the presence of Sibley Group, Pass

Lake Formation clasts precludes that identification. The TABLE 10. Average Spectrometer Readings for Lithological Units McKellar Creek Diatreme (from Sage 1982). Rock Type Number of Readings Average Value (cpm) Metasediment 67 3,901 T2 229 T3 70 Breccia Regolith 15 15,900 T2 1,119 T3 261 Breccia Outcrop 9 16,333 T2 778 191 T3 Diabase 2 2,800 T2 135 T3 35 2 x 3 m Sibley Clast 1 3,000 150 T3 100 Lamprophyre 1 2,500 T2 200 100 T3 Readings were taken with a gamma ray McPhar TV-1-spectrometer where - Ti is total count T2 is count due to U + Th T3 is count due to Th 133

The breccia fragments are composed of rounded to angular

clasts of pink and white quartzite, metasediments and

granitoids. Clasts generally do not exceed 0.3 m in maximum

dimensions. One clast, however, is approximately 2 m x 3 m

in size (Sage 1982).

Economic Geology:

The contact between the diatreme and the country rocks can

be mapped with a scintillometer. The breccia is radioactive,

although the intensity appears variable. Sage (1982) provides

a table depicting averaged spectrometer readings for lithological

units at the McKellar Creek diatreme. This table is reproduced

in this report as Table 10.

These figures represent unstripped data taken with a gamma ray

McPhar TV-1-spectrometer.

The diatreme was staked by L. Kaye in 1977. No record of any exploration work is on file. ISH

OEAOHORSE CREEK DIATREME

Location and Access:

The Deadhorse Creek diatreme group is located approximately

3.2 km north on the Deadhorse Creek forest access road, which

intersects Highway 17 just east of the intersection of

Deadhorse Creek and Highway 17 in Walsh Township.

The diatreme has maximum dimensions of 1,600 m by 400 m and

is elongated in a north-northeast direction (Sage 1982). The

property was staked by Gulf Minerals Canada Limited in 1977.

The claims are located from between 2.4 km and 3.2 km north

of Highway 17 on the Deadhorse Creek road.

Geology;

Gulf Minerals has identified five breccia stocks on the

property; the largest one is approximately 730 m in diameter,

the smallest is 60 m long and 30 m wide.

Locally derived clasts, probably reflecting the nature of

the intruded rocks, are abundant throughout the diatreme.

No exotic, mantle or deep-seated origin clasts, were identified

by Sage (1982). Clasts range from subangular to angular

and tend to increase in size toward the contacts of the

diatreme.

Sage (1982) was able to subdivide the diatreme on the basis of the amount of brecciation and has formulated two basic units: non-brecciated to moderately brecciated and moderately J3G

to strongly breccxated. Oiatreme contacts with the host

rock vary from gradational to very sharp.

Sage (1982) was also able to delineate the diatreme components

into a "red breccia", "carbonate-rich breccia", and "scapolite

replacement breccia".

The "red breccia" is characterized by abundant bright red angular clasts. Typically the rims are more altered than the cores and most exhibit subconchoidal fracturing. The red coloration is due to the introduction of iron and their hardness to silicification (Sage 1982). The red breccias give a strong response to the K-channel of the gamma ray spectrometers, suggesting a potassium enrichment. Disseminated sulfides are common within the matrix. The breccia appears to be clast-supported.

In the "carbonate-rich" breccias, red clasts weather in positive relief above a fine matrix of carbonate and biotite.

The breccia is matrix-supported and relatively radioactive

(Sage 1982).

Scapolite replacement breccias are best exposed on a small hill on the east side of the Deadhorse Creek forest access road at 3.2 km. The breccia weathers dark grey and often the weathered surface is highly irregular due to differential weathering of the rock constituents. Scapolite can be seen in outcrop as white, radiating, prismatic crystals up to several 136

TABLE 11. DEADHORSE CREEK ANALYSES

ELEMENT SAMPLE NO. JS-U-82-1 JS-U-82-2

59 .3% 67.4%

A12O3 6 .30 9.25

Fe2O3 4 .37 3.17 MgO 1.57 1.65 4 .59 .14 3,.37 .07 K2O 0,.63 1.66

TiO2 0,.71 0.27

P205 0..20 0.09 MnO 0..26 0.19

C02 2..79 0.25 s 0.,04 0.17 LO + 7..1 3.5

Beryllium 0.,94% 0.2% Strontium 470 ppm 410 ppm Vanadium 2,180 ppm 560 ppm Yttrium 900 ppm 535 ppm Zirconium 5-15% 5-15% Barium 930 ppm 6,120 ppm Zinc 88 ppm Chromium 1,450 ppm Cobalt 10 ppm Copper 181 ppm Uranium 1,900 ppm 59 ppm Thorium 10 ppm Rubidium 90 ppm Gold 0.02 oz/T

TOTAL (88.4) (93.4) Analysis by Geoscience Laboratories, Ontario Geological Survey, Toronto, Ontario ASSAYS DEADHORSE CREEK DIATREME TABLE 11 Con'd...

Sample Au Ag U Th Cu Co Ni Pb Be Zr Zn Cr No. (oz/T) (oz/T) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) JS-U-3 <0.01 <0.10 13 150 125 10 20 700 N/D N/D JS-U-4A <0.01 <0.10 1600 2900 179 14 18 480 9 l

N/D = not determined /3e

TABLE 12. SELECTED SPECTROMETER READINGS AT HIGH GRADE SHOWING AT WEST DEADHORSE SUBCOMPLEX (see Table 9, Chart B, for Assays of Select Samples).

LOCATION READINGS REMARKS DH127 Tl 20,000 Sheared rock T2 1,100 T3 350 DH128 Tl off scale Sheared rock T2 30,000 trace of U staining T3 11,000 DH129 Tl 5,500 Granitic aplite T2 320 immediately north T3 55 of high grade showing DH130 Tl off scale Sheared rock T2 10,000 T3 2,300 DH131 Tl off scale Sheared, brecciated T2 3,300 and silicified T3 1,100 DH132 Tl off scale Red, silicified T2 10,0.00 hematized breccia T3 3,300 DH133 Tl 5,500 Metasediments enclosing T2 300 shear zone.. Unsheared T3 55 unmineralized DH134 Tl 20,000 Red, silicified T2 1,500 hematitized breccia T3 260 DH135 Tl 5,000 Metasediments enclosing T2 350 shear zone. Unsheared T3 60 unmineralized NOTES All readings in counts per minute Tl= Th + U + K T2= Th + U T3 = Th _ [from Sage (1982H Photograph 13.

Radiating fracture patterns around radioactive minerals, Deadhorse Creek West Subcomplex. millimeters in length. The reader is referred to Sage (1982)

for more details.

Economic Geology;

The Deadhorse Creek diatreme was discovered in 1977 and staked

by Gulf Minerals (Canada) Limited. The zone of highest

radioactivity was the West Structure. Gulf completed a program

of trenching and diamond drilling in 1978. Very high readings,

in excess of 10 times background, were obtained from the trenches.

Like Sage (1982), this author had difficulties in determining

the mineralogy of the highly radioactive zones at the West

Deadhorse Creek Showing. A cursory electron microprobe

examination of polished thin sections by G. C. Patterson,

Resident Geologist, Ontario Ministry of Northern Development

and Mines, Thunder Bay, tentatively identified a black

to reddish, very fine grained mineral as a calcium-thorium-

uranium-iron silicate. Positive identification was not possible due to the fine grained nature of the mineral.

Another radioactive mineral was examined with the electron microprobe; it was clear with a slight brownish hue. Results of the probe examination seemed to indicate the mineral eudialyte, but again positive identification was not possible due to the poor condition of the sample. This mineral is partially metamict and exhibits an intense radial fracture pattern. Photograph 13 illustrates this mineral in thin section.

High radioactivity of the Deadhorse Creek West Subcomplex is evident from Table 12. PORT COLDWELL ALKALIC COMPLEX

The Port Coldwell Alkalic Complex is host to several syenitic

dikes that contain high concentrations of radioactive elements.

These showings are along the Canadian Pacific Railway tracks

near Port Munro. The occurrences were discovered in 1949 by

T. Gustafson. Pye (1954), Fenwick and Scott (1977), and Lang

(1952) describe the showing's geology. Pye (1954) gives the

following account:

"The columbium deposits are columbium-bearing syenite dikes cutting basic intrusives intimately associated with the laurvikite and red syenites. These dikes are found in numerous localities. They are generally fine- grained, five feet or less in average width, and are radioactive in that they give readings of 2 to 3 times background on the geigercounter. In general, such radioactivity indicates the presence of small amounts of columbium, and assays giving up to 1% combined U3O8 and Cb20s have been reported from numerous occurrences by several prospectors who have staked ground in the area. The best showing was staked by Tor Gustafson in 1949, and work on this occcurrence led to the rush this year. The showing occurs on claims TB49939 and 52039 along the railway just west of Port Munro. It is a syenite dike, from 5 to 20 feet in width, in a fine-grained basic intrusive, and has been traced 1,500 feet in an eastwest direction. The dip varies from 85.°N to vertical. The dike rock is pink and fine-grained, and contains numerous irregular cracks which are filled by a coarse-grained green pyroxene, and where this pyroxene is most abundant the best grade material has been found. This radioactivity is such as to give readings anywhere from 30 to 60 times background throughout the length of the dike. Assays of grab samples indicate up to 1.35% ^205, 0.08% U3O8, 3.00% ThO2# and 12% cerium."

Analyses of two grab samples collected by the Resident Geologist's

office staff in 1977 and reported in Fenwick and Scott (1977) were as follows: 0.42 and 1.0 pounds U3O8; 0.92 and 1.27%

Cb205; and 0.45 and 0.5% Ce, respectively. The first sample also assayed 0.45% zinc. Miscellaneous Pegmatite Occurrences

Lake Helen Occurrence:

The property is situated on Lake Helen, approximately 6.5

km north of Nipigon. The property straddles the narrow

portion of the lake 2.5 km north of the mouth of the Nipigon

River.

Quetico Belt migmatites and gneisses underlie the property.

White, albite-rich pegmatite dikes up to 30 m wide intrude granitic gneisses and sedimentary migmatites. Some of these pegmatites have a yellow to yellow-green stain typical of uraniferous albite pegmatites of the area.

Work on this property by Aggressive Mining Limited in 1967 consisted of trenching and sampling of the occurrence.

Values of up to 0.135% U3O8 were reported by Archibald (1967).

A visit by the author in 1^82 confirmed the existence of a

2mx2mx26m trench located in a rectangular, stripped area on the lake's west shore. This area is distinguishable from Highway 11 on the lake's east shore.

A plot of counts per minute due to uranium, thorium, and total counts indicates that the uranium is associated with the pegmatite phases rather than the biotite schists and meta- sedimentary portions of the migmatites.

No samples were submitted for analysis. 143

Howard Lake Occurrence:

Pirie (1978) describes yellow staining on feldspar crystals

and fracture surfaces in a muscovite graphic granite sheet

located at the south end of Howard Lake (NTS 52B 14/SW)

in Trottier Township. No analytical work was done on the

property although "geiger counter" readings as high as one

hundred times background were recorded. In 1975, W. D.

(Bill) Morehouse, a Thunder Bay prospector, held claims

TB406178 and TB406179 that covered the showing area.

Beavercross Lake Occurrence:

Coates (1968) reports a radioactive pegmatite at the south

end of Beavercross Lake (NTS 42F5/NE). A t^Os-equivalent radioactivity assay gave a result of 0.02%. High radioactivity appears to be confined to the dark grey, quartz-rich portions of the pegmatite.

Tessier-Williamson Occurrence:

Coates (1972) reports radioactive pegmatite in Hele Township

(NTS 52A 15/NE). He dismissed the occurrence as due to thorium or radon gas. The author revisited the occurrence and found biotite-quartz-feldspar gneisses, intruded lit-par-lit by granitic pegmatites. However, the occurrence Coates was attempting to locate was the Tessier-Williamson Occurrence located

0.8 km to the east. Pye (1955) describes this occurrence as follows: "The deposits consist of a number of radioactive granitic dikes in granite gneisses. The main dike strikes eastwest and dips 40°N- It is highly radioactive, is stained yellowish and ranges from 2 to 8 feet in horizontal thickness. Bordering the dike on the two sides are radioactive altered zones up to 25 feet in horizontal width.

The radioactive dikes are on claim TB67087-89 and TB67096."

A grab sample obtained by Pye (1955) assayed 0.096%

U3°8* A 9rab sample collected by this author in 1982

assayed 680 ppm uranium, 20 ppm thorium.

Tennant Lake Occurrence;

Bond and Foster (1981), while mapping in the Melchett Lake

area for the Ontario Geological Survey, mapped a uraniferous

pegmatite south of the main body of Tennant Lake (NTS 42L 11/NE)

The pegmatite is located on Map P2392, and in the marginal notes

is described as follows:

"Uranophane staining was observed on one outcrop in the homogeneous diatexite south of Tennant Lake. The association of uranium mineralization to the diatexite stage of migmatization has been previously reviewed (Breaks, Bond and Stone, 1978). Samples with uranophane staining submitted for • analysis to the Geoscience Laboratory (Ontario Geological Survey) returned 320-490 ppm U or about 0.03% U3O8."

Barium is also associated with this occurrence.

Conwest Occurrence:

Conwest Exploration Company Limited investigated a radioactive pegmatite in the Manitouwadge area in 1954. The dike is located in the central portion of claim TB49752, just east of

Garnet Lake.

The occurrence consists of reddish pegmatite dikes that intrude massive grey granitic rocks. One of these pegmatites MS

was found to contain a radioactive zone that was 25 cm wide

and 12 m long. The radioactivity was confined to a fracture

zone within the dike. The fracture is 1.3 cm wide and 12 m

long. Within this fracture zone crystals of uraninite were

tentatively identified by L. K. Lytle, Project Geologist for

Conwest Exploration Company (Resident Geologist's Files, Ontario

Ministry of Northern Development and Mines, Thunder Bay, Ontario).

Heirick Showing:

This occurrence is located approximately 1.8 km south of Highway

17 at a point where the creek flowing into Moose Lake '42C12/NW)

crosses the highway in Bombay Township. The showing is situated

in the Sault Ste. Marie Mining Division. It has been described by

Page (1949) and consists of radioactive fractures cutting

guartzites and mafic volcanics that have been intruded by

feldspar porphyries. A regional fault occurs at the contact

between the quartzites and the volcanics. Host rocks are

intensely oxidized and disintegrated. No uranium assays were

reported, but geiger counter readings of up to 25 times background

occur over the showing area. Uranium staining is present.

This is the showing reported by Lang (1952).

Chimo Gold Mines Occurrence;

This occurrence is located approximately at Latitude 49°32'

Longitude 87°02' south of Salsberg Township in the Geraldton area. The area is underlain by Quetico Belt rocks and consists

of relatively flat-lying, white, pegmatite sills and meta-

sedimentary migmatites. Three diamond drill holes for a

total of 545 feet were drilled in 1968 by Chimo Gold Mines

Limited to evaluate the radioactive occurrence. Analyses

indicated up to 0.016% U3O3 (Resident Geologist's Piles, Ontario

Ministry of Northern Development & Mines, Thunder Bay, Ontario).

Sandy Stone Lake Explorations and Development Company

Charon Lake Group is located six miles south of the east

end of Pagwachuan Lake and approximately six miles ENE

of Caramat. The Kassagimini Lake Group is located just

south of Kassagimini Lake approximately six miles east of

Pagwachuan Lake.

The area is underlain by Quetico Belt rocks and consist of white pegmatites and metasedimentary migmatites. Up to 0.87% U3O8 is reported to occur associated with the yellow- stained pegmatites. Five diamond drill holes for an aggregate of 1,081.5 feet were drilled on the properties in 1958, (Resident Geologist's Files, Ontario Ministry of Northern Development & Mines, Thunder Bay, Ontario). References

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Fraser, D. and Reardon, E. 1980: Attraction of wild ungulates to mineral-rich springs in central Canada. Holarctic Ecology Vol. 3, p. 36-40.

Giguere, J. F. 1975: Geology of St. Ignace Island and Adjacent Islands, District of Thunder Bay; Ontario Division of Mines, Geological Report 118, 35 p., Map 2285.

Gill, J. E. 1926: Gunflint Iron-bearing Formation, Ontario. Geological Survey of Canada Summary Report 27C, p. 28c-88c.

Goodwin, A. M. 1960: Gunflint Iron Formation of the Whitefish Lake Area. Ontario Department of Mines Annual Report, Vol. LXIX, Part 7, p. 41-67.

Goldich, S. S. 1938: A Study in Rock Weathering, Journal of Geology, Vol. XLV1 Jan-Dec. 1938, p. 17-58.

Hanson, G. N. and Malhotra, 1971: K-Ar ages of Mafic Dikes and Evidence for Low Grade Metamorphism in Northeastern Minnesota: Geological Society of America Bulletin, Vol. 82, p. 1107-1114.

Harcourt, G. A. 1938: The southwestern part of the Schreiber Area, Ontario Department of Mines Annual Report, Vol. XLV11, Part IX, 1938, p. 1-28.

Hawley, J. E. 1929: Lead and Zinc Deposits, Dorion and McTavish Townships, Thunder Bay District. Ontario Department of Mines, 38th Annual Report, Part VI, p. 59-8 5. 151

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Kwiatkowski, Dennis 1975: Geology and Geochemistry of the Kakabeka Falls Anthraxolite. Unpublished H.S.Bc. Thesis, Lakehead University, Thunder Bay, Ontario, 103 p.

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1975: Geology of McTavish Township (South Half). District of Thunder Bay, Ontario Division of Mines, Preliminary Geological Series, Map P990, scale 1 inch to h mile.

W. H., Fenwick, K. G., Scott, J. F., Mason, J. K., Schnieders, B. R., Kristjansson, F. J., Speed, A. A. and Bourdages, H. M. 1982: 1981 Report of the Thunder Bay Resident Geologist, in Annual Report of the Regional and Resident Geologists, edited by C. R. Kustra, Ontario Geological Survey Miscellaneous Faper 101, 184 p.

Mcllwaine, W. H. and Tihor, L. A. 1975a: Dorion-Wolf Lake Area (West Part), District of Thunder Bay? Ontario Division of Mines, Preliminary Geology Series Map P994, scale 1 inch to h mile, 1:15,840. 1975b: Dorion-Wolf Lake Area (East Part), District of Thunder Bay; Ontario Division of Mines, Preliminary Geology Series Map P995, scale 1 inch to h mile, 1:15,840.

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1978: Genetic Aspects and Classification of Important Canadian Uranium Deposits, in Short Course in Uranium Deposits: Their Mineralogy and Origin; Mineralogical Association of Canada Short Course Handbook, edited by M. M. Kimberly, Vol. 3, University of Toronto Press.

Meillon, J. J. 1969: Assessment Work Report, Newmont Mining Corp. of Canada Ltd., Prairie Lake Area. Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario.

Meneghel, L. 1980: A Model of the Processes Forming Sedimentary Hosted Uranium Deposits, Economic Geology, V. 76, #3, p. 727-732.

Misra, A. and Faure, G. 1970: Restudy of the Age of the Gunflint Formation of Ontario, Canada: Geological Society of America Abstracts for 1970, V. 2, p. 398.

Mitchell, R. H. and Platt, R. 1977: Field Guide to Aspects of the Geology of the Coldwell Alkaline Complex, 23rd Annual Meeting, Institute on Lake Superior, Marathon, 1977.

Money, P. L., Baer, A. J., Scott, B. P., and Wallis, R. H. 1970: The Wollaston Lake Belt, Saskatchewan, Manitoba, Northwest Territories; in Basins and Geosynclines of the Canadian Shield: edited by A. J. Baer, Geological Survey of Canada Paper 70-40, p. 171-200.

Morehouse, W. W. 1960: Gunflint Iron Range in the Vicinity of Port Arthur; Ontario Department of Mines, Vol. LXlX, Part 7, p. 1-40.

Moreau, M. 1974: Part II: Vein Type Uranium in Formation of Uranium Ore Deposits: Vienna, International Atomic Energy Agency, p. 715-719.

Morey, G. B. 1969: The Geology of the Middle Precambrian Rove Formation in Northeastern Minnesota, Minnesota Geol. Surv. Special Publication Series SP-7, University of Minnesota, 62 p.

Munrad, E. 1974: Hydrothermal Alteration of Granite Rocks and its Possible Bearing on the Genesis of Mineral Deposits in the Southern Black Forest, Germany. Econonic Geology, Vol. 69, No. 4, p. 532-844.

Ojakangas, R. W. 1978: Criteria for Alligator River Type Uranium Deposits in the United States. Abstract Proceedings of the 24th Annual Meeting Institute on Ike Svjerior Geology Milwaukee, Wisconsin. Page, Trevor 1949: Herrick Showing. Information Release, Lake Superior Mining Corporation Limited. Resident Geologist's Piles, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario.

Pirie, J. 1978: Geology of the Crooked Pine Lake Area, District of Rainy River; Ontario Geological Survey Report 179, 73 p. Accompanied by Map 2405, scale 1:31,680.

Purucker, M. 1983: Time of Formation of Soft Iron Ore on the Gunflint and Mesabi Ranges (Ontario, Canada, and Minnesota, U.S.A.). Economic Geology, Vol. 78, 1983, pp. 502-506.

Pye, E. G. 1954: Property Visit Report, Port Munro Area. Resident Geologist's Piles, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario.

1958: Property Visit Report, Tessier-Williamson Uranium Occurrence. Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thunder Bay, Ontario.

1965: Georgia Lake Area. Ontario Department of Mines Geological Report No. 31, 113 p. Accompanied by Map 2056, scale 1 inch to 1 mile.

1968: Geology and Scenery: Rainy Lake and East to Lake Superior, Ontario Department of Mines Geological Guidebook, No. 1, 118 p.

Raemaekers, P. P. 1979: Stratigraphy, Sedimentology, and Structural Geology of the Middle Proterozoic Basins in the Athabasca Area, Saskatchewan, Canada, and their Bearing on Uranium Mineralization, International Uranium Symposium on the Pine Creek Geosyncline, Sydney, Australia, 1979, extended abstracts, p. 163-164.

1981: Hudsonian and Helikian Basins of the Athabasca Region, Northern Saskatchewan: _in_ Proterozoic Basins of Canada, edited by F. H. A. Campbell. Geological Survey of Canada Paper 81-10, p. 219-233.

Raemaekers, P. P. and Dunn, C. E. 1977: Geology and Geochemistry of the Eastern Margin of the Athabasca Basin. Geological Society of Saskatchewan Special Publication 3, p. 287-322.

Raemaekers, P. P. and Hartling, A. A. 1978: Structural Geology and Intrusive Events of the Athabasca Basin and their Bearing on Uranium Mineralization, in Uranium Exploration Techniques, Geological Society of Saskatchewan, Special Publication 4, edited by G. R. Parslow, p. 221-234. Robertson/ D. S., Tilsley, J. E., Hogg, G. M. 1978: The Time Bound Character of Uranium Deposits: Economic Geology, V. 73, p. 1409-1419.

Roscoe, S. M. 1973: The Huronian Supergroup, a Paleoaphebian Succession Showing Evidence of Atmospheric Evolution: Geological Assoc. of Canada Special Paper 12, p. 31-47.

Ruzicka, V. 1977: Conceptual Models of Uranium Deposits and Areas Favorable for Uranium Mineralization in Canada Report of Activities, Part A; Geological Survey of Canada, Paper 77-1A, p. 17-25.

Sage, R. P. 1982: Mineralization in Diatreme Structures North of Lake Superior, Ontario Geological Survey, Study 27, 7 9 p,

1983: Geology of the Prairie Lake Carbonatite Complex, Ontario Geological Survey Open File Report 5412, 133 p., 3 photos, 6 tables, 8 figures.

Sage, R. P., Bathe, D. , Wright, W., Chamois, P., and Shewbridge, K. 1976: Prairie Lake Carbonatite, District of Thunder Bay; Ontario Division of Mines Preliminary Map P1070, Geological Series, scale 1:2,400 or 1 inch to 2,000 feet. Geology 1975.

Sakrison, H. C. 1977: Prairie Lake Complex. Resident Geologist's Files, Ontario Ministry of Northern Development and Mines, Thund.er Bay, Ontario.

Satterly, J. 1955: Radioactive Mineral Occurrences in the Vicinity of Hawk and Richard Lakes; Ontario Department of Mines, Geological Circular 1, 6 p.

Scott, J. F. 1982: Uranium: In 1981 Report of the Thunder Bay Resident Geologist in Mcllwaine, W. H., Fenwick, K. G., Scott, J. K., Mason, J. K., Schnieders, B. R., Kristjansson, R. K., Speed, A. A., and Bourdages, H. M. Annual Report of Regional and Resident Geologist's 1981. Ontario Geological Survey Miscellaneous Paper 101, edited by C. R. Kustra, p. 53-54.

Shklanka, R. 1972: Geology of the Steep Rock Lake Area, District of Rainy River. Ontario Department of Mines and Northern Affairs, Geological Report 93, 114 p., 1 map, 2 charts.

Sibbald, T. I. I., Munday, R. J. C., and Lewery, J. F. 1976:" The Geological Setting of Uranium Mineralization in Northern Saskatchewan; in Uranium in Saskatchewan Special Publication 3 edited by C. E. Dunn, p. 51-98.

Standing, Keith 1983: Deeply Penetrating Geophysical Techniques Applied to the Athabasca Basin, 85th Annual General Meeting of CIM, Winnipeg, Manitoba. Stockwell, C. H. 1962: Structural Provinces, Orogenies, and Time Classification of Rocks of the Canadian Precambrian Shield jLn_ Isotopic Ages, Report 2 of Age Determinations: Geological Survey of Canada, Paper 61-17, p. 108-118.

Sutcliffe, R. H. 1981: Geology of the Wabigoon-Quetico Subprovince Boundary in the Lake Nipigon Area, District of Thunder Bay in Summary of Field Work 1981 edited by Wood, J., White, 0. L. , Barlow, R. B., Colvine, A. C, Ontario Geological Survey MP 100, p. 26-29.

1982: Precambrian Geology of the Wabigoon-Quetico Subprovince Boundary, Black Sturgeon Lake Sheet, Thunder Bay District, Ontario Geological Survey Map P.2531, Geological Series? Preliminary Map, scale 1:50,000.

Sutcliffe, R. H., and Greenwood, R. C. 1982: Geology of the Lake Nipigon Area, p. 19-23 _in Summary of Field Work 1982 by the Ontario Geological Survey, edited by Wood, J., White, 0. L., Barlow, R. B., and Colvine, A. C, Ontario Geological Survey MP 106, 235 p.

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1948: Radioactive Nodules in Sediments of Sibley Series, Nipigon, Ontario. Transactions of the- Royal Society Canada, 3rd Series, Vol. XL11, See IV.

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1978b: Geological Setting of the Beaverlodge type of vein- uranium deposits and its comparison to that of the unconformity tyr.v» In Uranium Deposits: Their Mineralogy and Origin; edited by Kimberly, M. M., Toronto, University of Toronto Press, p. 431-456.

1982: Geology of the uranium deposits related to the sub- Athabasca unconformity, Saskatchewan; Geological Survey of Canada Paper 81-20, 56 p.

1983: Some Chemical Aspects of tha Regolithic and Hydrothermal Alterations Associated with the Uranium Mineralization in the Athabasca Basin, Saskatchewan, jLn_ Current Research, Part A, GSC Paper 83-1A, p. 1-14.

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1972: Keweenawan Flood Basalts and Continental Rifting; Geological Society of America, Abstracts with Programs, V. 4, No. 7, p. 732-734. Wilson, A. W. G. 1910: Geology of the Nipigon Basin, Canada Department of Mines, Geological Survey Branch, Memoir 1, 152 p.

Yule, G. R. 1979: Investigations of the Goodmorning Lake Radioactive Fault Breccia: Innes Lake Area, Oorion Township, Northwestern Ontario. H.B.Sc. Thesis, Lakehead University, Thunder Bay, Ontario, 93 p. SECTION 1

URANIUM ASSOCIATED WITH FAULTS AND THE PROTEROZOIC/ARCHEAN UNCONFORMITY 1 Greenwich Lake Area 2>TOodmorning Lakes Fault Area 3 Enterprise Mine. 4Dorion Amethyst Mine 5 Jessie Lake Occurrences 6 Black Sturgeon Lake Area 7 Frazer-Malborne Lake Area 8 Little Bear Amethyst Quarry URANIUM ASSOCIATED WITH ALKALIC COMPLEXES.CARBONATITES, AND DIATREMES 9 Port Coldwell Alkalic Complex "lODeadhorse Creek Diatremes 11 Prairie Lake Carbonatite URANIUM ASSOCIATED WITH QUETICO BELT PEGMATITES AND OTHER PEGMATITIC ROCKS 12 Howard Lake Occurrence 13 Black Sturgeon Lake Area 14Greenwich Lake Area 15 Innes Lake Area SECTION 2 SECTION 3

A,, s E C T 1 0 N 4 1

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SI !•*•

- LBOBND

n CENOZOie QUATERNARY • •» M PIEISTOCCNL AND Recent Santf. innl, city

MCSOZOIC* CMTACEOUS > LOWER CRETACEOUS f City, s»nd. lignite, lirecliv. ktotmihc II Quart! sand. \ PALEOZOIC* Jl MIMIMIPPIAN LOWER MISSISSIPPIAN

n Shale. iand,tone •. Wlt«M« \ '•" ' \ 1 DEVOMIAN UPPER DEVONIAN

\ 1) Vac* itialt.

\ " s. MIDDLE DEVONIAN •J A l> H Limeiionc. dolomite, shife. gypsum

-.* » LOWER DEVONIAN ''^ , I "-- Sandstone, atkovt. conglomerate Mil 11 stone, shale, limestone , J N SILUWAN \ UPPER SILURIAN \~ " limestone, dolomite, stltstone. shale. ** mudstone, sandstone, gypsum, salt 1V N MIDDLE SILURIAN "1 11 II Dolomite, limestone w Ci"" • —iS" LOWER SILURIAN A ( u Sandstone, shale, dolomite H R o c *§!

OftOOVICIAN n ( UPPER OROOVICIAN

I.II* , II Shale, limestone, dolomite, sandstone

1 MIDDLE ORDOVICIAN

*• * > n Limestone, shale. c •" 0" LOWER ORDOVICIAN

j • It Dolomite, sandstone \

CAMWMAN UPPER CAMBRIAN

\ ? II Conghmatalt. sandstone, shale.

s " S LOWER ANO MIODIE CAMBRIAN - - __^ • " , Sandstone, conglomerate, shale

^>- -^^^ PRECAMBRIAN MIOOUC TO UATC PNECAMBRIAN CAMONATITf -ALKALIC COMMJEXES* 1 1 Cirbonaim. rmahttint and Malx sye- 1 ~~ u ' nHai. tanUt tint asxcialxl mafrc and , uHrarmficnxlit. T"' ( LATf MAFIC I6MC0US MOCXl"

/ f. ..*—* . ! Ht.fbt. T 11 li ] arfgranoohyre i lATf niK ICNfOUS ROCKt* |ttf i .y 1 ! G/«nttfforift. ttondhiemitt, quttti >• i maonnHt.panrte.ir'n'tt.ovartipoi. 1 **W. fttntUH, apKH. minor umlho- «** Mr. tathta antiun and migmatitts. 15 Innes Lake Area SECTION 6 16 Hele Township(Tessier-Williamson Occurrence) 17 Lake Helen 18 Jessie Lake Area 19Chimo Gold Mines Occurrence 20Tennant Lake Occurrence 21 Longlac Occurrence 22 Sandy Stone Lake Exploration (Charon Lake Group) 23 Sandy Stone Lake Exploration (Kassagimini Lake Group) 24 Beavercross Lake Occurrence 25Conwest Occurrence 26 Herrick Showing #OTHER TYPES 27Gunflint Formation "Mudbail Tuff Unit

M

ONTARIO DEPARTMENT OF MINES AND NORTHERN AFFAIRS HONOURABLE ALLAN F. LAWRENCE. Minister D. P. Douglass. Deputy Minister |. E.Thomson. DirectorCeologkal Branch

Map 2199 ONTARIO GEOLOGICAL MAP West Central Sheet

Scale 1:1,013.760 or 1 Inch to 16 Miles

Ml BBBBBSaaJ1 M » » » _-> m wimi»- SECTION 7

MOT— Compilation by L O. Arm, $. B. Lum&trt, V. 6. mint.'tnd D. Mr. Rototon, Onfv/o Ofrtmtnl a M//wt md Hottnirn Afftks. 1970. International and Inferprovmaai boundary. Gtoloer compllHt from publish*! tnd unpubHstml map* and npottt oftha Ontario Oapartmant of Mints ana Nottharn Attain and lit Gaobokal Sum, of District ana County boundary. Canada. unevUiihad data on lilt with tna Ontario Oapartmant of Mktatand Northarn Affairs, inttrprata- tion of aaromagnatic maps and othtf tourcas. ] Township boundary, ban or meridian I lint; sunraytd. furthtr information on tht otology tnd mining ratu- Ittions may ot oottinm from tht Ontario Oapartmant of Mint and Northtrn Affairs, ftrlitmtnl Buildings, I Township boundary; unsurveyed. Toronto. SECTION 8 LAKE

SUPERIOR

irtv

*>•..

C G»f««»«» r SECTION 9 <• I mannnm.tranm.irtntu.tvmtaer- 1 ehyry.poemetm.epilt.minorenorlho- ult, derived intitm and mtgmatites. OntNVKU PROVINCE Ml DOLE TO LATE PRECAMBRIAN IAM.V MAFIC AND UlTftAMANC ISNfOUt NOCKf Onrite, gabbro, peridotite, pyrotanitt. anorthotitt, and derived metamorphic locks.

MCTAMOIMEN'ri*' CARBONATE METASEDIMENTS

Marble, calcsilkate rocks, skun.

CLASTIC METASEOIMENTS Conglomerate, greywackt. orthoouartr- lie, arkost, siHstone. Che/I, minor iron formtlion and metovotcentcs METAVOLCANICS' MAFIC TO FELSIC METAVOLCANICS

.. I fkMS.tutt.tMKCta. minor iron formation J and mttastrtimtnts.

VUPERIOR AMD •OUTHCNN PROVINCES LATE PRECAMBRIAN KEWHNAWAN SEDIMENTARY AND VOLCANIC ROCKS' 1 Conglomerate, grtymacke.arkotexarto > n*anxks.lult,basattandrhyoimtKi*s. 1 nuarll porphyry.

MIDOLf PRECAMBRIAN ANIMIKIE*

\ I Grtywacke, shale, argittile. iron forma- ' ) Ikm.Umnlont.luU.tiasaH.

HLMOMAN COBALT GROUP'

] Conglomerate, grtywacke. oflhoQoarU- ' I ite, liltttone. arglllite.

ELLIOT LAKE, HOUGH LAKE AND OUIRKE LAKE GROUPS* Congkxrmatt, graywackt, arttost, or. thoDuartiltt. argillite limestone, dolo- mHt .batatt. rhyolitc

EARLY PRECAMBRIAN EAW.V FELMC ICWOUS AND OMPHK KOCKS* Granodiorm. ttipOKiamitt. qoato dlorfle. quartt manzonite, granite, syenite, quirti and Mw porpttyrin, pagma- Utt, apMe. undltfartntinad migmaUtt; M( ptrtommaterr mrgmttitk metasadi- ments and minor metavotcenics. KAPUWCAMNC MIANULITE COMPUX

Granutit* facias mataaadiments, meia- • rokanks and granite.

IAKIY MAFIC ANO ULTRAMAHC IWMOUS NOCKS'" ,

Dkxite. gatbro, noritt. pyronnite, peri • dotHx. dunitt. atrptnt(nlte.

Jn»nfH HitOV METAMOMKNTC" ' Conglomerate, greywacke. arkose. I I orthoouartlite, aroillUe, slate, marble, chart. Iron formation, minor volcanics and raleHd migmatites. • WOO1 MCTAVOLCAMCs' FELSIC TO INTERMEDIATE METAVOICANICS1' 1 Khyolitt. rhyodacitt and decile (flows. > tuffs, end breccias), chert, iron forma- I tion, minor mataaadimants and intru- sive rocks, and retiiad migmatites.

MAFIC METAVOLCANICS* ; 1 Stsart, andante (flows. Mis and brec- ' citt). chert, iron formation, minor meta- 1 aadtmants and intrusive rocks, and re- mad rmtmaims.

m A lew small intrutive bodies of this am have- baen identified by radiometric age dating methods. * May be in part post-Pracambrian. * Agtntraliteddistributionotdiebaiediktsisshown. C Gng«*»u» r * formerly classified as AHoman andlor Leuranlian. * formerly classified as Grenvilkt andlor Heatings Series. ' Hocks in theae groups are subdivided Mhoiogicaiiy and the order does not necessarily imply age re- lationship within or among groups. * Includas Osier and Sibley Groups. * Includes Gunflrnt and *w formations, and the SECTION 10 formations of trie Whitewater Group. The White- water Group formations in tht.Sudbury area may bacl*rthaanate. I Includes Gowaanda, lorrain, Gordon Lake, $ar mnr farmtUont. * Thaat three groups coHactirerr wen formerly dtuifiadas truct Grout. Include* inthntfuts It the Mtinendt McKim. Hamsay Lake, ftiors. mtsitaatl. true*. £a»anbla. Strpent. Kuans formaharti. Some of Inetxk units Dktntlhe north than at lama Huron may be af Mrchmn a§a. 3268 ISSN 0826-9580 ISBN 0-7729-2201-2