DISCOVERY HISTORY

In the winter of 1988, a new grid was established in the Sue area and surveyed using Max-Min and VLF techniques. A program of 9 drill holes was scheduled on the 2.9km long Max-Min conductor near the end of the winter program.

The aim of the program was to test by a "first pass approach" the conductor over its complete length by drilling single holes spaced at 400m on the Max-Min conductor axis using a combined percussion - coring rig. The exploration strategy was successful as three holes, CS2, CS5, and CS9 scattered from north to south returned anomalous uranium values. Hole CS5 located on line 3+OOS displayed the highest values (12.5m at 0.8% eU3O8) and was the discovery hole of Sue A.

During the summer of 1988, Sue A was drilled off on a 25 x 10m grid and exploration along the trend resumed.

The interpretation of the geophysical results emphasized a strong correlation between a VLF low and the Max-Min data for the position of Sue A on the trend. A similar anomaly was located 400 metres north of Sue A and was drilled in the summer of 1988. Hole CS44 was the discovery hole of the Sue B deposit and returned 16m at 0.2% and 4m at 1.5% U³O⁸ in two mineralized zones, one of which was just below surface. The Sue B deposit was immediately drilled on the same grid pattern as Sue A.

During the winter of 1989, a decision was taken to drill off Sue A and Sue B at a reduced spacing of 10 x 12.5m to avoid the "nugget" effect of localized high-grade pods and to define accurately the geological ore reserves.

Two holes CS34 and CS60 drilled on the southern limit of Sue A at the end of 1988, had identified anomalous uranium values (0.154% over 1.3m) in the basement contrasting with the unconformity mineralization of Sue A and Sue B. The location of these two holes was at the intersection of NE-SW trending VLF structures with the EM conductor.

In the summer of 1989, exploration resumed mainly south of Sue A. Emphasis was put on the holes previously mentioned (CS34 and CS60) and the anomalous basement-uranium zone was traced to the southwest until S209 was intersected. Hole S209 was the discovery hole of the Sue C deposit and returned 18m grading 21% U³O⁸ with the mineralization entirely hosted in the basement.

After the discovery of S209, the drill pattern was changed to match a near north-south structure revealed by a resistivity survey carried out along the Sue trend.

Then following confirmation of a steeply dipping vein attitude of the Sue C mineralization, the exploration methodology changed. A combination of angle holes and vertical holes was used to intersect the mineralization at depth and updip at the unconformity.

To date, Sue C is grading into the Sue CQ deposit, a zone of multiple mineralized lenses, to the south. Both deposits have been drilled using a pattern of 12.5 x 10m (1990 and 1991).

At the beginning of the summer of 1991, Sue C and Sue CQ remain open particularly at depth and numerous other occurrences have been discovered along this productive Sue trend (Sue D).

DEPOSIT GEOLOGY

The Sue deposits lie on the western flank of the Collins Bay dome, approximately 2.5 kilometres east of the McClean Lalce deposits (Fig. 4). A 2.9 kilometre long basement Max-Min conductor coinciding with rock layers enriched in graphite was identified during the winter of 1988 and subsequently drilled. The deposits Sue A, B, C and CQ trend roughly north-south (Ml2°) along steeply east-dipping units of graphitic gneisses (Fig. 5).

All the Sue orebodies devoid of any surface expression were discovered above these conductors and are coincident with their geophysical expression.

£H GRAPHITIC GNEISS FJ23 QUARTZITIC UNIT

£33 GRANITE (ARCHEAN)

£-ï-\ INTERMEDIATE GNEISS

•I URANIUM DEPOSIT

0 500m

HORIZONTAL LOOP (MAX WIN) CONDUCTOR FAULTS

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Fig 5. Geology of the basement in the Sue area.

Locauon of the deposits.

The favourable graphitic gneiss extends south off the Wolly property. To the north it extends for one kilometre beyond Sue B where it is folded sharply to the west and eventually links up with the structure controlling the McClean Lake deposits (Fig. 4). In the Sue area, the graphitic unit is in fault contact to the east with feldspathic gneisses and granitoid/pegmatoid rocks whereas to the west it is gradational with intermediate gneissic units (Fig. 6, 7 and 8). The graphite content varies widely from 1% up to 70% and may occur as bands paralleling the foliation.

Combinations of recurring normal and reverse faulting parallel to the east dipping foliation in the graphitic gneisses produced a basement hump with 8 to 40 metres of relief. Reverse faulting has resulted in stepping the unconformity down to the west. It is on this basement high and its western flank that the Sue deposits occur. Northeasterly and northwesterly striking faults offset and modify the major NS structural controls, thus creating conditions which limit the extent of mineralization along trend.

The Sue trend is characterized by two main parallel graphitic units, 80 to 100m apart (Fig. 5).

The eastern unit hosts the unconformity related deposits Sue A and Sue B, the western unit hosts the basement type Sue C and Sue CQ deposits.

The Sue deposits are located on, above or below the unconformity which lies 65 to 75 metres below surface. The bulk of the mineralization occurs either completely in the overlying sandstones or entirely in the basement. The eastern margin of the deposits is largely controlled by faulting and by the lack of graphitic rocks in the basement. Basement lithologies on the west appear to exert little control over the lateral extent of mineralization.

FELSIC GNEISS

Fig 6. Sue A deposit Geology at the unconformity.

Fig 7. Sue B deposit Geology at the unconformity.

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MAIN HORIZONTAL LOOP (MAX-MIN) CONDUCTOR

FELSIC GNEISS INTERMEDIATE GNEISS PEGMATO1D

GRAPHITIC GNE'SS CLAY

.yV-j QUARTZ RICH UNIT FAULT

0 50 m

Fig 8. Sue C - Sue CQ. Geology at the unconformity.

The deposits are typically hosted in massive earthy-red clay extending above and below the unconformity. Laterally, alteration and mineralization diminish rapidly with the north-south faults providing sharp boundaries.

SUE A DEPOSIT

The Sue A deposit lies between 60 and 75 meters below surface (Fig. 9) and strikes north 12°

east. At a 0.10% U³O⁸ cutoff, the deposit is 176 metres long with a width ranging from 8 to 30 metres and averaging 15 to 20 metres (Fig. 17). Its thickness vanes from 1.5 to 12 metres with an average of 9 metres The mineralization is extensively controlled by faulting, resulting in irregular cross-secnonal shapes. In general, the deposit is flattened with a westerly dip conforming to the downdropping of the unconformity. Mineralization terminates against two sets of faults, northeast and northwest m direction

[" | OVERBURDEN

GRAPHITIC GNEISS

FELSIC GNEISS S PEGMATOIDS MINERALIZATION HELIKIAN UNCONFORMITY FAULTS

Fig 9 Sue A deposit Cross section Line 3+12.5S.

Lithology and contour of mineralization at SOOppm cut-off.

The deposit lies on and immediately above the unconformity in an envelope of massive earthy-red clay (Fig. 13). Argillic alteration extends almost up to the sandstone subcrop along fault zones, leaving only scattered sections of sihcification in the cap rock An average of 9 metres of glacial overburden covers the sandstones

Minor amounts of uranium mineralization extend downward into the basement as narrow roots along faults. Less than 2% of the Sue A deposit lies below the unconformity.

The distribution of uranium is confined to a few high grade (>5%) pods, mostly m the south half of the deposit where some 70% of the total uranium is located Grades exceeding 15% occur.

SUE B DEPOSIT

The Sue B deposit is located approximately 350 metres north of Sue A The mineralized zone is 90 metres long and averages 40 metres in width (Fig 18) but unlike Sue A, the mineralization occurs at two horizons within the sandstone (Fig 10)

The upper horizon contains some 50% of the uranium mineralization It lies at a depth of about 20 metres above the unconformity. Mineralization extends at one point to the subcrop of the

GRAPHITIC GNEISS

ATHABASCA ÜIÜJ SANDSTONES I———| INTERMEDIATE I———I GNEISS

FELSIC GNEISS MINERALIZATION HELIKIAN UNCONFORMITY FAULTS

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Fig 10. Sue B deposit.

Cross section line 1+62.5N.

Lithology and contour of nvmeralviation at SOQppm cut-off.

Athabasca sandstones at a depth of 8 metres below surface. This upper zone is about 50 metres long, 26 metres wide, and 17 metres thick.

The lower zone of mineralization lies on and immediately above the unconformity at depths between 60 and 75 metres. In general The mineralization lies on the western flank of the basement high in the fault steps created by the downdropping of the unconformity. The basement high has up to 20 metres of relief.

The upper and lower zones are connected by chimney-like zones of mineralization. Very little uranium occurs in the basement rocks (less than 1% of the deposit).

The Sue B mineralization is largely fault controlled. The upper zone may be a product of intersecting structures such as conformable and conjugate faults which created a zone of weakness and relatively high permeability. Uranium migrated upward along connecting faults and spread out into the highly fractured sandstone to form the upper deposit. Laterally, mineralization terminates rather abruptly against north-south trending faults. As in Sue A, northeast and northwest striking faults limit the extent of the deposit in the north-south direction.

The uranium mineralization is hosted in massive earthy-red clay, although the upper zone displays remnant silicifications. The sandstone between the upper and lower zones is slightly resilicified (Fig. 14).

The Sue B orebody is a medium grade deposit with very little high-grade mineralization. Grades usually do not exceed 5% U3O8.

MINERALIZATION HELIKIAN

UNCONFORMITY Fig 11. Sue C deposit.

Cross section line 5+OOS.

Lithology and contour of the mineralization at SOOppm cut-off.

SUE C DEPOSIT

The Sue C area lies immediately to the southwest of the Sue A deposit.

The Sue C mineralized structure is a 10 to 15 metre wide NS subvertical structure dipping 70°

to the east (Fig. 11), paralleling the graphitic/feldspathic gneiss Hthological contact 100 metres to the east (Fig. 8).

The mineralization is continuous along trend from line 4+75S to line 8+50S (Fig. 19). The massive high grade ore which characterizes the northern part of the orebody clearly ends at line 7+25S where the subvertical vein ("C" type) coexists with widespread lower grade mineralization ("CQ" type).

The mineralized structure lies completely within the Aphebian pelitic metasediments in close proximity to graphitic gneisses.

From east to west, a typical lithological sequence across the Sue C deposit consists of non-graphitic gneisses intermixed with pegmatoids, non-graphitic gneisses (20 to 40m thick), massive ore and clay, a quartz rich unit and non-graphitic gneisses (Fig. 11).

The mineralization is hosted by reverse anastomosing faults, (the Sue C fault), striking N12° and parallel to the basement lithologies. It is located at the footwall of the graphitic gneiss, in a clay-rich zone as weh1 as in the lower graphitic unit itself. It is typically underlain in sharp contact by a massive quartz rich lens. A second quartz lens was intersected 30m west of the ore.

The average grade is high, 7% U³O⁸ at 0.1% cut-off (Table lu). The mineralization consists of massive pitchblende, pitchblende nodules and veinlets within a white or black clay envelope locally overprinted by intense hematitic-clay alteration. The mineralization contains minor amounts of arsenides.

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At the scale of the deposit, the mineralization is typically exhibiting a vein geometry parallel to the remnant subvertical foliation. On a detailed scale, the high grade pods are distributed as vertically stacked, flat lenses bounded by the graphitic gneisses and the quartz lens (Fig 21) Therefore the main structural control of the mineralization is the concomitant action of steeply dipping faults and flat lying shears

The flat lying shears induce a thickening of the quartz lens at depth, thus controlling the downdip limit of the ore The depth of the mineralization to date ranges from 115m in the north to 150m in the south

The unconformity is typically 75 to 80m below surface and is disrupted by the major reverse faults creating a hump or offsets of up to 42m There is no evidence of the mineralization extending upwards into the overlying sandstones Immediately above the ore, the sandstones are strongly argilhzed (chlormzaüon and bleaching) with variable hematization (Fig 15)

The continuity of the mineralization in the Sue C deposit is perturbed by major NE and NW faults which have slightly displaced the vein over a few metres (Fig 19, 20) The NE trending faults are commonly strongly graphitic and display disseminated mineralization of low grade 0 05 to 0 1% with one layer at 3 3% U³O⁸ The mineralization is discontinuous but may be traced for 120m especially south of Sue A towards Sue C

QUARTZITIC UNIT CLAY MINERALIZATION HELIKIAN UNCONFORMITY FAULTS

Fig 12 Sue CQ deposit Cross section line 7+87 5S Lithology and contour of the mineralization at SOOppm cut-off

SUE CQ DEPOSIT

Although the hthology is consistent along trend, Sue C and Sue CQ ire two distinct deposits The geometry and the grade of the mineralization as well as the structural characteristics are clearly different

The Sue CQ deposits lies south of line 7+12 5S where a major NW-SE fault zone limits the southern extension of the Sue C mineralization

The mineralization is discontinuous and of lower grade (1 69% at 0 1% cut off, Table III) but spread over a large area

The ore is hosted completely within intensely altered graphitic to non graphitic metapehtes (Fig 12)

The overall mineralized volume is divided into multiple moderately dipping lenses for a total width of 40m over a strike length of 125m The ore does not subcrop, with the upper limit at a depth of 120m i e 45 metres below the unconformity and is known to date to a depth of 165 metres (90m below the unconformity)

The bulk of the mineralization consists mainly of pitchblende nodules associated with an ubiquitous red-brown hematmc clay-nch envelope overprinting the pervasive ilhn/ation of the gneisses The massive Sue C-type ore is not observed in the Sue CQ orebody

The structural controls of the mineralization remain similar to those observed m the Sue C deposit Flat lying shears are inducing high-grade pods, vertically stacked in moderately dipping

lenses of 1 to 5m in thickness (Fig 22) However, the NW-SE fault corridor exhibits normal vertical offsets of the unconformity and controls a strong development of the sihcificanon which invades almost completely the southern limit of the Sue CQ deposit

ALTERATION

The Sue deposits have many common alteration characteristics also known m other Athabasca deposits

Most of the alteration pattern descriptions are based on macroscopic core observations Detailed mineralogical and chemical studies on the ore are currently being earned out Preliminary data using X-ray diffraction and electron microprobe are here provided (Sevenn, 1991)

All of the described rocks are altered, due to the fact that drilling to date has been confined to the orebodies

Five main types have been recognized 1

2 3 4 5

retrograde metamorphism during later stage of the Hudsoman event pre-Athabasca paleoweathenng profile

diagenetic alteration of the Athabasca sandstones hydrothermalism

late alteration due to remobilizauon

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RETROGRADE METAMORPHIC ALTERATION

Post Hudsonian retromorphic alteraüon is pervasive as fresh rocks are rare

In the Sue area, the retrograde metamorphism is a subordinate alteration phase in the vicinity of the deposits, and has been overprinted by all following events

The primary mineralogy of the basement rocks is transformed by two main phases of clay minerals, chlonte and ilhte Quartz and graphite are preserved

Cordiente, sillimanite, garnet and bioüte are transformed into mainly FeMg-nch chlonte whereas the feldspars are subject to serialization with the presence of albite and calcite

PRE ATHABASCA PALEOWEATHERING

The paleoweathenng has affected the basement rocks prior to the diagenesis of the Athabasca sandstones It is well developed in the Sue area but awav from the deposits It is represented by a characteristic vertical gradation of colour zones This was described by MacDonald's regohth study (1980) of the Wolly area

At the boundaries of the orebodies, the regolith or saprohte (Wilson, 1986) forms a discontinuons hemaüüc zone overlying pale to dark green metapehtes extending 5 to 40m below the unconformity and within 15 metres of the deposit The oxidized red zone is characterized by the absence of graphite and sulphides, presence of hematite and all metamorphic minerals are clay altered with chlonte, übte and kaohmte on top of the sequence The original texture is often destroyed or completely transposed In the green zones, the graphite and the original structuration of the rocks are preserved and the metamorphic minerals are altered into ilhte, Mg-nch ilhte and Fe-chlonte The thicknesses of these alterations vary considerably according to the parent rocks The prominent white zone as described by MacDonald (1980) is absent in the vicinity of the orebodies

The remnant pre Helilaan weathering alterauons are complicated by the later diagenetic and hydrothermal effects and even by the retrograde metamorphic event in the green zones The paleoweathenng profiles of the Sue deposits are typical and similar to those of other Athabasca orebodies (Halter, 1988, Bruneton, 1986, Ruhrmann, 1986, Wallis et al, 1983)

DIAGENETIC ALTERATION

In the complex history of the Athabasca sandstones deposition, the diagenetic alterations are the most difficult to grasp as they are completely superimposed by late hydrothermal alterations affecting the entire stratigraphie column above the orebodies

A few remnants of diagenetic phases are preserved at distances of 15 to 25m from the mineralization where the sandstones range in colour from salmon pink to purple with

multicolored bands of dark hematitic layers (associated to heavy minerals) alternating with late limoniüc sections

A sihcified cap is preserved in the uppermost portion of the sandstones (down to 25m below the overburden) outside the faulted comdors controlling the orebodies

HYDROTHERMAL Al TFRATION In the Sandstones

The alteration in the sandstones is highly variable and does not form concentric haloes as in the Cigar Lake deposit (Bnmeton, 1986, Fouques et al, 1986) It is more mterfingered and each of the various deposits of the Sue trend has a unique distribution of alteration processes due to their structural setting and mineralization control

In Sue A and Sue B, the alteration extends to surface i e 60 to 70m above the unconformity and is mainly controlled and restricted to the fault comdor limiting the lateral extent of the deposits (Fig 13 and 14)

| | OVERBURDEN I . ' , , , , , | NO ALTERATION

A3 LIMONITIC/

i" BLEACHED ALTERATION E „ ,\ CHLORITIZATION

|g SECONDARY 2s HEMATIZATION

|———| MINERALIZATION __ HELIKIAN

UNCONFORMITY

Fig 13 Sue A deposit Cross section line 3+125S Alterauons and contour of the mineralization at 500ppm cut-off

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Fig 14 Sue B deposit Cross section line 1+625N Alterations and contour of the mineralization at 500ppm cut off

Two alteration processes are noticed beyond the fault zones and are represented by the following Overgrowths of euhedral quartz to milky translucent quartz which are infilling the subvemcal fractures They have been observed more than 50m away from the deposits along strike in the Sue area and can extend over 150m laterally m the McClean area A bleaching event with quartz dissolution and ilhte emplacement in the matrix and m complete leaching of hematite from the purple layers This phenomenon is particularly well developed in the sandstones overlying the Sue C ore In the Sue A and Sue B deposits, the bleaching has been observed 20m away from the mineralization

In the vicinity of the deposits the following zonation has been observed from the surface to the unconformity

Destruction of the sihcified cap, within the fault boundaries, thus creating a collapse of the surface of the sandstones well documented m the Athabasca basin (Walhs et al, 1983)

Bleaching m the fault zone, with incomplete removal of hematite, increase of the illiac matrix and quartz dissolution Hematite remains present in the sedimentary features (bedding planes, cross-beddings and Liesegang rings) although superimposed by several stages of hmonitization along fractures and bedding planes The uranium content vanes from Ippm to 3ppm in the fracture zones Dravite occurs as spherule nch layers as well as overgrowths on green detntal tourmaline (Skupmsky, 1990) These accessory minerals occur as well in the barren zones and have been identified m several other Athabasca

Bleaching m the fault zone, with incomplete removal of hematite, increase of the illiac matrix and quartz dissolution Hematite remains present in the sedimentary features (bedding planes, cross-beddings and Liesegang rings) although superimposed by several stages of hmonitization along fractures and bedding planes The uranium content vanes from Ippm to 3ppm in the fracture zones Dravite occurs as spherule nch layers as well as overgrowths on green detntal tourmaline (Skupmsky, 1990) These accessory minerals occur as well in the barren zones and have been identified m several other Athabasca

Dans le document New Developments in Uranium Exploration, Resources, Production and Demand (Proceedings of a Technical Co-operation meeting, Vienna, 26-29 August 1991) | IAEA (Page 192-200)