Pegmatite- and leucogranite-Pegmatite- and leucogranite-hosted uranium and thorium hosted uranium and thorium mineralization in northern mineralization in northern

Saskatchewan: Fraser Lakes Saskatchewan: Fraser Lakes Zones A and BZones A and B

Christine Austman, Kevin Ansdell, and Irvine Annesley

Outline

Regional Geological Setting Fraser Lakes Uranium and Thorium Mineralization Fraser Lakes Geological Cross-Sections Granitic Pegmatite Mineralogy, Textures and

Alteration Geochemistry Similarities to other deposits Conclusions Future Work

“The aim of this project is to determine whether these [granitic pegmatites and

leucogranites] represent a distinct target for uranium exploration in Saskatchewan or if the mineralization is related somehow to unconformity-type uranium deposits. “

Location The Fraser

Lakes mineralized zones are located on JNR Resource’s Way Lake Property

Outside of the Athabasca Basin (~25 km from SE edge)

~ 55 km from Key Lake U mine Way Lake

PropertyFraser LakesZones A & B

Key Lake U mine

Regional Geology

The Way Lake Project is within the Eastern Wollaston Domain

The Wollaston Domain consists ofArchean orthogneisses (predominantly granitic gneisses)Paleoproterozoic Wollaston Group metasedimentary

rocksHudsonian granites, amphibolites, leucogranites,

migmatites, and granitic pegmatites The domain was metamorphosed and complexly

deformed during the Trans-Hudson Orogeny (approximately 1.8 Ga)

Regional metamorphic grade is upper amphibolite to lower granulite facies in this part of the Wollaston Domain

Fraser Lakes Geology and Geophysics

Divided into the Zone A and Zone B mineralized zones

Zone A is in a NE-plunging synformal and Zone B is in an antiformal fold nose

5 km section of a complexly folded electromagnetic (EM) conductor (i.e. graphitic pelitic gneisses) is adjacent to Zones A and B

Zone B is cross-cut by several ductile-brittle and brittle structures (black lines) Total field aeromagnetic image and trace of the EM

conductor with location of drill hole collars

Fraser Lakes Radiometrics

Fraser Lakes Zone B shows up as clearly visible radiometric highs (bright orange to red spots) on GSC regional radiometric survey maps of U and Th

Fraser Lakes Topography and Aerial Photograph

The surface expression of the EM conductor adjacent to Fraser Lakes Zone B is a swampy, low-lying area

Zone B mineralization outcrops at surface on the eastern edge of the swamp

Fold nose is visible from the air

Section 1

Section 2

Cross-Section 1: WYL-09-39, -30, and WYL-08-524, -525

Mineralization consists of uranium- and thorium-bearing granitic pegmatites and leucogranites

They intrude the contact between basal Wollaston Group and underlying Archean orthogneisses

Cross-Section 2: WYL-09-41, -42, -49, -49a, and -50

Fault/Shear zone?

The Wollaston Group – Archean contact is highly deformed, locally becoming protomylonitic to mylonitic

Fracture and fault zones can be seen locally in core

Cross-sections show offsets thought to be related to faulting/shearing

Granitic pegmatite mineralogy and textures

Granitic pegmatites with variable amounts of quartz, feldspar, biotite, and other minerals

Overall coarse grained to pegmatitic

Variable size (cm to several m scale)

Commonly zoned (igneous AFC processes)

Multiple generations of granitic pegmatites, with mineralized pegmatites usually older (syn-tectonic) and non-mineralized younger (post-deformation)

Late Hudsonian (limited age data)

Pegmatites – Partial melts at depth and in situ Migmatites associated with the

granitic pegmatites and leucogranites in basal Wollaston Group metasediments

Upper amphibolite to lower granulite facies metamorphism (~18 – 20 km depth)

Formed by igneous processes (partial melting and fractionation)

Mineralogy

Uranium and Thorium Minerals• Zircon (Zrn)• Monazite (Mz)• Allanite (Aln)• Uraninite - Uranothorite - Thorite (Urn)

Highly Variable!

Alteration of granitic pegmatites

Retrograde Alteration•Chlorite (Chl)•Epidote (Ep)•Sericite (Ser) •Hematite (Hem)•Quartz (Qtz)

Hydrothermal Alteration•Fluorite (Fl)•Chlorite (Chl)•Hematite (Hem)•Clay minerals•Sausserite•Carbonate (Cal)•Quartz (Qtz)

Significant AnomaliesUp to 0.453% U3O8 in outcrop grab samplesWYL-09-38

• 0.177 % Cu, 0.056% Ni, 0.044% Zn, and 0.0681% Mo over 6.50 m

WYL-09-39• 0.166% U3O8 and 0.113%

ThO2 over 0.15 mWYL-09-41

• 0.134% U3O8 and 0.077% ThO2 over 1.0 m

WYL-09-50• 0.183% U3O8 and 0.062%

ThO2 over 1.0 m

Fraser Lakes Geochemistry

Similarities to Athabasca U deposits and other U deposits Similar granitic pegmatites are found throughout the

Wollaston Domain, many containing elevated U, Th, REEs and other elements

Radioactive leucogranites and granitic pegmatites are in the basement rocks under several Athabasca Basin unconformity uranium deposits (ex: McArthur River Zone 2, Millenium, Roughrider, and others)

Chlorite, clay, and hematite alteration found in Zone B drill core is similar in appearance to that of basement-hosted unconformity uranium deposits

~ 200 – 250 m of erosion below the Athabasca/ basement unconformity in the area

Similarities to Grenville Province igneous-related uranium deposits

Conclusions

Structurally controlled, basement-hosted U and Th mineralization (+/- REE mineralization)

Hosted by Hudsonian leucogranites and granitic pegmatites that intruded at the contact between Wollaston Group metasediments and Archean orthogneisses

Zone B has significant U-Th-REE mineralization in drill core and outcrop

Granitic pegmatites and leucogranites formed by partial melting

Granitic pegmatites experienced post-crystallization hydrothermal alteration (and remobilization of U and Th?)

Potential exists for basement-hosted unconformity uranium deposits in the Fraser Lakes area

Future Work

Petrography Microprobe work to constrain mineralogy and

mineral chemistry Whole rock geochemical analysis REE and Fl-Cl analysis, and Pb-isotopes for

selected samples U-Pb chemical age dating Determination of local metamorphic conditions Development of a metallogenetic model for

Fraser Lakes Zones A and B

Acknowledgements