Stratigraphy, gamma-ray spectrometry and uranium prospectivity … · 2020. 4. 30. ·...

Stratigraphy, gamma-ray spectrometry and uranium prospectivity of theKilohigok paleosol, Bear Creek Hills, western Nunavut

A. Ielpi1, S. Michel

2, J.W. Greenman

3and L.E. Lebeau

2

1Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario, [email protected] School of Earth Sciences, Laurentian University, Sudbury, Ontario3Department of Earth Sciences, Carleton University, Ottawa, Ontario

The Kilohigok Basin Geoscience Project is being led by the Canada-Nunavut Geoscience Office in collaboration with the Harquail Schoolof Earth Sciences, Laurentian University. The study area comprises a portion of the Bear Creek Hills, located on the eastern side ofKiluhiqtuq (Bathurst Inlet), Kitikmeot Region of Nunavut (NTS 76J). The objective of the project is to improve the geological knowledgeand to investigate the economic potential of the Kilohigok Basin in western Nunavut.

Ielpi, A., Michel, S., Greenman, J.W. and Lebeau, L.E. 2017: Stratigraphy, gamma-ray spectrometry and uranium prospectivity of theKilohigok paleosol, Bear Creek Hills, western Nunavut; in Summary of Activities 2017, Canada-Nunavut Geoscience Office, p. 37–48.

Abstract

APaleoproterozoic passive margin encompassing fluvial and nearshore-marine deposits (Kimerot Group) is exposed in theBear Creek Hills surrounding Kiluhiqtuq (Bathurst Inlet). The succession comprises the lowermost fill of the Kilohigok Ba-sin, and nonconformably sits atop metasedimentary rocks of the Archean Yellowknife Supergroup—part of the Slave Prov-ince of the Canadian Shield. This summary of activities deals with the stratigraphy, paleogeography and gamma-ray spec-trometry of a ca. 2.0 Ga horizon of paleoweathering found at the contact between the Kimerot Group and the YellowknifeSupergroup, known as the Kilohigok paleosol.

The Kilohigok paleosol comprises a 1.5 m thick, rusty-weathered horizon intersected by quartz veins and derived frommetapelite and meta–iron formation of the Yellowknife Supergroup, and underlies a paleotopography that slopes up to10 m/km along strike. Gamma-ray spectrometer profiles throughout the paleosol reveal anomalous values of radioactivity(up to 867.5 nSv/h), with peak concentrations of uranium exceeding 120 ppm. The Kilohigok paleosol is overlain by fluvialconglomerate and sandstone that bear evidence for intense chemical weathering and sericitization, and point to productionand routing of detritus from the hinterland of the Slave craton at 2.0 Ga. These results complement ongoing studies along theKilohigok paleosol, on a transect of more than 200 km, and suggest that portions of the so-far underexplored Kilohigok Ba-sin may host uranium resources.

Résumé

Une marge passive paléoprotérozoÏque renfermant des dépôts marins littoraux et fluviatiles (groupe de Kimerot) affleuredans la région des monts Bear Creek qui encerclent Kiluhiqtuq (Bathurst Inlet). La succession comprend à sa partieinférieure l’unité de remplissage du bassin Kilohigok et repose en discordance sur les roches métasédimentaires du Super-groupe de Yellowknife d’âge archéen, lequel fait partie de la Province des Esclaves du Bouclier canadien. Le présentrésumé porte sur la stratigraphie, la paléogéographie et l’analyse spectrométrique aux rayons gamma d’un horizon âgé dedeux milliards d’années ayant subi une paléométéorisation, appelé paléosol de Kilohigok, qui a été identifié à l’endroit d’uncontact entre le groupe de Kimerot et le Supergroupe de Yellowknife.

Le paléosol de Kilohigok se compose d’un horizon altéré de couleur rouille d’une épaisseur de 1.5 m que recoupe des veinesde quartz; ce paléosol s’est formé à partir de formations ferrifères métamorphisées et métapélitiques du Supergroupe de Yel-lowknife et repose sous un paléorelief dont la pente atteint jusqu’à 10 m/km parallèlement à la direction. Des profilsspectrométriques aux rayons gamma effectués à divers endroits du paléosol ont donné des teneurs anormales de radio-activité (jusqu’à 867,5 nSv/h), dont une concentration de pointe d’uranium de plus de 120 ppm. Le paléosol de Kilohigokest recouvert de conglomérat et de grès fluviatiles qui témoignent d’épisodes intenses d’altération chimique météorique etde séricitisation tout en indiquant que le matériel détritique aurait été produit et serait provenu de l’arrière-pays du cratondes Esclaves il y a deux milliards d’années. Ces résultats viennent s’ajouter aux études en cours entreprises le long d’un

Summary of Activities 2017 37

This publication is also available, free of charge, as colour digital files in Adobe Acrobat® PDF format from the Canada-NunavutGeoscience Office website: http://cngo.ca/summary-of-activities/2017/.

transect de plus de 200 km du paléosol de Kilohigok et semblent indiquer que certaines sections du bassin de Kilohigokjusqu’à présent peu explorées pourraient receler des ressources en uranium.

Introduction

The Kilohigok Basin, in the Kitikmeot Region of Nunavut(Figure 1), represents one of the major—and yet least eco-nomically explored—Precambrian basins preserved withinthe Canadian Shield (McCormick and Grotzinger, 1992).The Proterozoic sedimentary record of North America con-sists of several basins and inliers found atop crystallinebasement rocks (Young, 1981; Davidson, 2008), and ac-

counts for a complex history of repeated rifting and crustalamalgamation throughout two entire Wilson cycles (Li etal., 2008; Pehrsson et al., 2016). Due to their proximity toexisting infrastructures or navigable seaways, some ofthese basins have been favourably exploited for commodi-ties, including world-class uranium deposits in the Atha-basca Basin, Saskatchewan and Alberta (Jefferson et al.,2007), and lead-zinc-silver deposits in the Selwyn Basin,Yukon (Gordey, 2013). The Kilohigok Basin remains rela-

38 Canada-Nunavut Geoscience Office

Figure 1: Geological sketch of Kilohigok Basin (modified from Campbell and Cecile, 1976, 1979; Campbell 1979; Ielpi et al., 2017). Geo-chronological data from Bowring and Grotzinger (1992) and Heaman et al. (1992).

tively unexplored. In the context of uranium plays, mineral-ization has often been found at or near surfaces of strati-graphic discontinuity between crystalline basement rocksand overlying sedimentary successions (i.e., unconform-ity-type uranium deposits), and specifically along horizonsof paleoweathering (‘paleosols’) associated with suchzones (Rainbird et al., 1990; Gall, 1992, 1994, 1999; Fedoet al., 1997; Murakami et al., 2001).

The Kilohigok Basin lies within the Slave Province of theCanadian Shield (Padgham and Fyson, 1992), and wasmapped at reconnaissance scale by O’Neill (1924) and laterby Wright (1957), Tremblay (1967, 1971) and Fraser andTremblay (1969). A basin-scale stratigraphic outline wasfirst introduced by Campbell and Cecile (1976, 1979,1981), Cecile (1976), Cecile and Campbell (1977, 1978)and Campbell (1978), and a modern structural-strati-graphic framework was established by Tirrul (1985),Grotzinger and Gall (1986), Grotzinger et al. (1987, 1989),Grotzinger and McCormick (1988), Tirrul and Grotzinger(1990), McCormick (1992) and McCormick andGrotzinger (1992, 1993).

The Kilohigok Basin Geoscience Project represents thecontinuation of collaborative work in the region since 2014by the Canada-Nunavut Geoscience Office, LaurentianUniversity and the Geological Survey of Canada (Bermanet al., 2015, 2016; Ielpi and Rainbird, 2015a; Ielpi et al.,2015, 2017; Rainbird and Ielpi, 2015). This summary of ac-tivities presents the results of fieldwork undertaken in theBear Creek Hills (Figure 2), in an area roughly centred on

latitude 66°42’N, longitude 107°27’W. Here, the uncon-formable contact between basement rocks of the SlaveProvince and basal deposits of the Kilohigok Basin is later-ally continuous and well exposed. So far, the paleoweath-ered horizon along the unconformity, referred to as theKilohigok paleosol (Ielpi et al., 2015), has been investi-gated for a distance of ~200 km and represents the main tar-get for uranium mineralization using gamma-ray spectrom-etry. The scope of this contribution is to discuss the area’spotential for uranium prospectivity, and to characterize itsstratigraphy and paleogeographic settings during paleosoldevelopment.

Geological setting

The Kilohigok Basin sits unconformably atop the SlaveProvince, a cratonic block that amalgamated with the rest ofLaurentia during the global orogenic processes recorded at2.1–1.8 Ga (Hoffman, 1988; Zhao et al., 2002; Bleeker,2003). The basin records a time span of ~2.0–1.6 Ga (Bow-ring and Grotzinger, 1992) and, from its southwestern ter-mination at Rockinghorse and Contwoyto lakes to its north-eastern inlier at Hadley Bay (Victoria Island), it covers astratigraphic transect more than 700 km long. The main ba-sin exposures surround Kiluhiqtuq and occupy an area of~800 km2 (Figure 1). The relationships between the Kilo-higok Basin and its basement rocks are mainly autoch-thonous, and younger deposits of the Elu Basin unconform-ably cover the Kilohigok Basin fill in its northeasternportion (Campbell, 1979; Campbell and Cecile, 1979; Ielpiand Rainbird, 2015a, 2015b, 2016). The Kilohigok Basin is


Figure 2: Satellite map of study area (image taken in late spring; see Figure 1 for location in Kilohigok Basin; DigitalGlobe, 2014). Bedrockexposures are evident in grey tones. Pink line marks nonconformity between Archean Yellowknife Supergroup and PaleoproterozoicKimerot Group. Blue line marks stratigraphic boundary between Kimerot and Bear Creek groups. Stratigraphic dip indicators in black pointto direction of stratigraphic younging (strata dipping at 15–35°).

further dissected by the northwest-trending Bathurst Fault(Campbell and Cecile, 1981; Grotzinger and McCormick,1988; Culshaw, 1991), which exhibits ~70 km of sinistraldisplacement.

Different theories have been proposed regarding the crustalmechanisms responsible for the formation of the KilohigokBasin. Hoffman (1973) recognized similarities in stratigra-phy and structure to coeval rocks preserved in the WopmayOrogen along the opposite side of the Slave craton, and hy-pothesized that the Kilohigok Basin represented an abortedrift. Campbell and Cecile (1981) argued that the lack ofgrowth faulting and evidence for magmatism at time of de-position remained at odds with Hoffman’s (1973) model,and proposed an alternative—yet similar from a geody-namic standpoint—scenario where the Kilohigok Basin re-corded the development of an intracratonic trough. In thelatter reconstruction, this intracratonic basin developed inrelation to a hypothetical failed rift farther north (presentco-ordinates). While permissible at the time, this theorycould not fully account for syndepositional growth of struc-tural arches and fold-and-thrust belts later identified withinthe basin (Tirrul, 1985). Meanwhile, it became apparentthat the Thelon Tectonic Zone bordering the Kilohigok Ba-sin to the east represented a major and partly coeval oro-genic front (Thompson and Ashton, 1984; Thompson et al.,1985; Tirrul, 1985; Tirrul and Grotzinger, 1990). Based onrefined structural-stratigraphic work, Grotzinger et al.(1987, 1989), Grotzinger and McCormick (1988),McCormick (1992) and McCormick and Grotzinger (1992,1993) recognized the Kilohigok Basin as a major foredeeprelated to the collision between the Slave and Rae cratonsand development of the Thelon Tectonic Zone at 2.0–1.9 Ga.

It is worth noting that, in the authors’ reconstruction, thelowermost Kilohigok Basin fill did not yield any evidencefor converging tectonism. This basal succession, referredto as the Kimerot Group, comprises the lower clasticKenyon Formation and the upper, mixed clastic-carbonatePeg Formation. The Kimerot Group is interpreted as a pas-sive-margin succession accumulated on the eastern marginof the Slave craton prior to its collision and amalgamationwith the Rae craton (Grotzinger and Gall, 1986; Tirrul andGrotzinger, 1990). This most-recent model remains ac-cepted, with the Kimerot Group regarded as a compellingexample of a Paleoproterozoic passive margin developedalong a rifted Archean craton (Bradley, 2008).

Methods

Field traverses were run out of a floatplane-accessed campin July 2017, and covered an area to the east of Kiluhiqtuqknown as the Bear Creek Hills (part of NTS 76J; Figure 2).Observations of rock type and geological structure werecollected on both basement rocks and overlying deposits of

the Kimerot Group. Detailed investigations were focusedon the bulk composition and alteration state of paleoweath-ered rocks along the Kilohigok paleosol. Estimates on min-eral assemblages were made using hand lenses on freshsamples. Observations on the stratigraphic developmentand depositional architecture of the Kimerot Group werecollected on a west-dipping monocline and were comple-mented by the collection of paleocurrent indicators basedon the direction of frontal accretion of crossbeds.

The naturally occurring radioactive properties of crystal-line basement rocks of the Slave Province and overlyingdeposits of the Kilohigok Basin were assessed using a Ra-diation Solutions Inc. RS-125 hand-held gamma-ray spec-trometer. The database of spectral signatures includes read-ings of total radioactive dose rate (expressed in nanosievertsper hour, or nSv/h) and abundances of uranium (ppm), tho-rium (ppm) and potassium (%). Vertical and horizontal spec-trometry profiles were measured along the Kilohigokpaleosol and in immediately overlying deposits at severallocations. Hand samples were collected for furtherpetrographic and geochemical analysis.

Results

Stratigraphy and field relationships

A 15–35° westward-dipping monocline, extending fromthe Bear Creek Hills (Figure 2) to the Kiluhiqtuq seaboard,has an ~8 km strike length and a stratigraphic thickness of~2.5 km. This monocline represents one of the most com-plete stratigraphic sections exposed in the Kilohigok Basin(McCormick, 1992) and records a significant portion of thebasin’s depositional history. Here, exposures of theKimerot Group are aligned along a 50 km long, north-northwest–south-southeast transect that is associated withpositive relief due to higher resistance to erosion than adja-cent rock types. The present study area is a ridge that ex-poses a continuous section measuring ~150 m thick and2.2 km along strike (Figure 2, 3a).

Basement rocks exposed in the area consist of metapeliteand meta–iron formation (Figure 3b–c). Metapelite con-tains a mineral assemblage of cordierite, andalusite andstaurolite, as well as relicts of Bouma-like graded beddingin decimetre-thick intervals that suggest a turbiditicprotolith (cf. Therriault, 2003). Meta–iron formation is rep-resented by garnet-amphibole quartzite with rusty weather-ing. These metasedimentary rock types are part of the Yel-lowknife Supergroup (cf. Culshaw and van Breemen,1990; Culshaw, 1991), and their regional foliation patternin the study area dips moderately to the northeast.

The surface of stratigraphic nonconformity underlying theKimerot Group displays an attitude consistent with that ofthe overlying monocline and is characterized by up to 20 mof paleotopographic relief over the 2.2 km of observed lat-



Figure 3: Field aspects of the Kilohigok paleosol and Kimerot Group in the Bear Creek Hills: a) panoramic view of study section, withnonconformable bottom and stratigraphic top of Kimerot Group marked with dashed yellow lines; b) metapelite of Yellowknife Supergroupintersected by quartz veins; lens cap for scale (encircled) is 5 cm across; c) detail of metapelite in (b), exhibiting rusty weathering alongKilohigok paleosol; d) Kenyon Formation basal oligomictic pebble conglomerate, exhibiting sericitic alteration; e) cross-stratified gravellysandstone, overlying basal conglomerate; f) quartzarenite (light grey) interbedded with thin dolostone (rusty brown) at transition betweenKenyon and Peg formations; note herringbone cross-stratification and tidal bundles in quartzarenite; g) plan view of domal stromatolites inPeg Formation dolostone (uppermost ‘stromatolite reef’); lens cap for scale (encircled) is 5 cm across.

eral exposure (Figure 3a). Along this surface is the Kilo-higok paleosol, which consists of a horizon, up to 1.5 mthick, characterized by rusty weathering and pervasiveveining (Figure 3b, c). Veins are linear, up to 7 cm wide andfilled with quartz (Figure 3b). An older generation of north-west-striking and shallowly dipping veins with ~0.5–1 mspacing is cut by a second, younger generation of roughlyorthogonal, northeast-striking and steeply dipping veinswith ~3 m spacing. As detailed below, anomalous values ofradioactivity related to uranium mineralization have beenrecorded within 20 cm of the younger veins.

The Kimerot Group can be subdivided into several inter-vals characterized by distinct lithology and sedimentarystructures. Field observations support the subdivision intothe lower, clastic-dominated Kenyon Formation (here~60 m thick) and the upper, mixed clastic-carbonate PegFormation (~90 m thick) proposed by Grotzinger et al.(1987). Given the scope of this summary, only the lower-most deposits found in proximity to the Kilohigok paleosolare detailed. The basal coarse-grained deposit consists of2–3 m of pebbly, clast-supported and crudely planar-strati-fied conglomerate with greenish-grey sandy matrix (Fig-ure 3d). The conglomerate is oligomictic, comprising pre-dominantly quartz (~95%) and sporadic red jasper andmetapelite lithic fragments. The greenish-grey pigmenta-tion of the sandy matrix, observed elsewhere along theKilohigok paleosol (Ielpi et al., 2015, 2017), has been re-lated to the breakdown of iron-magnesium silicates andsubsequent iron reprecipitation on authigenic clay mineralsderived from plagioclase weathering (‘sericitization’;Rainbird et al., 1990; Gall, 1994; Fedo et al., 1997). Thebasal conglomerate changes upward into a coarse-grainedsandstone with floating granules (Figure 3e). The coarse-grained sandstone is organized in 10–20 cm thickcrossbeds. Paleocurrent indicators collected on foresetspoint to southward transport (Figure 4a). Crossbeds are, inplaces, organized into larger scale sediment forms defined

by inclined depositional surfaces (Figure 4b), pointing tothe growth and migration of sediment bars composed ofaccretionary macroforms (cf. Miall, 1994).

The overlying deposits are organized into quartzarenite-dominated intervals with decimetre-scale hummocky cross-stratification and herringbone-stratified sets (Figure 3f).Notably, crosslaminae display, in places, a sharp and rhyth-mic grain-size segregation typical of tidal bundles (Fig-ure 3f; cf. Dalrymple et al., 1991). The quartzarenite gradu-ally fines upward throughout the Kenyon Formation andeventually grades into the Peg Formation, which is charac-terized by a rhythmic alternation of heterolithic greywacke-siltstone with centimetre-scale hummocky cross-stratifica-tion and laminated doloarenite (i.e., a mixed sandstone withdolomitic cement). Domal stromatolites appear in the mid-dle Peg Formation (Figure 3g) and become increasinglycommon upsection. The uppermost Peg Formation is markedby a distinctive ‘stromatolite reef’ (cf. Grotzinger and Gall,1986), which is up to 2 m thick and serves as a regional keybed. The sedimentology and depositional architecture ofthe middle–upper Kenyon and Peg formations will betreated in more detail in a forthcoming contribution.

Gamma-ray spectrometry

The radioactive signatures of both basement rocks and over-lying deposits were assessed along both vertical and hori-zontal sections through the Kilohigok paleosol, and resultsare summarized in Table 1 and Figure 5. Vertical sections 1and 2, measured through the basal Kenyon Formation (Fig-ure 5), yielded background radioactivity values (up to193.3 nSv/h and up to 11.7 ppm uranium). On the otherhand, an exposure of the nonconformity between the Yel-lowknife Supergroup and the Kenyon Formation (Figures 2and 5) yielded anomalously high values of radioactivity (upto 867.5 nSv/h), with uranium concentration as high as121.1 ppm. Radioactivity anomalies along the nonconfor-mity correspond to basement rocks intersected by steeply


Figure 4: Field aspects of the basal fluvial deposits of the Kenyon Formation: a) rose diagram showing southward sediment paleotransport(number of measurements, scale in percentage of outer ring, average vector and 95%-confidence arc are indicated); b) crossbeds (yellow)and inclined surfaces (red) related to growth and migration of fluvial bars (field book for scale is 20 cm long).

dipping quartz veins (Figure 5, section 3). Elevated ura-nium values were found at intervals along the 60 m strike-parallel horizontal section. Radioactivity values diminishsharply downsection through the basement (Figure 5, sec-tion 4), reaching background levels (less than 156.6 nSv/hand less than 11.8 ppm uranium) farther than 1 m strati-graphically beneath the nonconformity. Spectrometricanalyses performed elsewhere in both the YellowknifeSupergroup and the Kimerot Group have not returned anyanomalously high radioactivity.

Vertical profiles 1 and 2 through the basal Kenyon Forma-tion did not show any significant correlation between ura-nium, thorium and potassium (Figure 5). On the other hand,horizontal section 3 along the nonconformity revealed aweak inverse correlation between uranium and potassium,and a weak direct correlation between uranium and thorium(Figure 5).

Discussion and conclusions

The Kilohigok Basin Geoscience Project focused on thestratigraphy, paleogeography and gamma-ray spectrome-try of a paleoweathered horizon developed at the contactbetween Archean metasedimentary rocks of the Yellow-knife Supergroup and Paleoproterozoic deposits of theKimerot Group, in the eastern portion of the Kilohigok Ba-sin, Kitikmeot Region of Nunavut. The ~1.5 m thickpaleoweathering horizon, referred to as the Kilohigokpaleosol, is here developed on oxidized metapelite andmeta–iron formation. The Kilohigok paleosol includesquartz veins that dissect the metapelite and meta–iron for-mation, and is overlain by basal deposits of the KenyonFormation (Kimerot Group), which also shows evidence ofchemical paleoweathering and sericitization (cf. Rainbirdet al., 1990; Gall, 1994; Fedo et al., 1997). Gamma-rayspectrometry revealed uranium concentrations of up to121.1 ppm within the Kilohigok paleosol. In the projectarea, anomalous values of radioactivity are recorded onlyin proximity to the paleosol, highlighting how gamma-rayspectrometry represents a time- and cost-efficient approachwhen prospecting for radionuclide mineralization alongsurfaces of stratigraphic discontinuity.

In order to reconstruct the depositional and paleogeograph-ic setting during Kilohigok paleosol development, field in-vestigations also focused on the sedimentology of theKimerot Group, confirming the subdivision into the lower,clastic Kenyon Formation and the upper, clastic-carbonatePeg Formation. The basal and coarser grained deposits ofthe Kenyon Formation point to accumulation in a proximalfluvial environment (cf. Grotzinger and Gall, 1986), basedon their textural immaturity and abundance of unidirec-tional crossbedding. The lower conglomerate likely repre-sents the product of comparatively high-gradient, gravel-bed trunk rivers or small piedmont fluvial fans, based on the

abundance of clast-supported and planar-bedded gravelsheets (Ielpi et al., 2016). The local paleoflow dispersion isbest reconciled with the fluvial-fan scenario, and relativelysteep paleogradients can be inferred from the paleotopo-


Table 1: Gamma-ray spectrometry along the Kilohigok paleosol inBear Creek Hills (see also Figure 5).

graphic relief observed along the basal paleoweatherednonconformity of the Kilohigok Basin. The overlying peb-bly sandstone indicates deposition in a more distal, deeperand perennial fluvial system that was mature enough todevelop high-relief fluvial bars within its channels (Miall,1994).

Paleoflow indicators suggest production and routing of de-tritus from portions of the Slave craton located to the north(present co-ordinates) of the study area. The transition fromfluvial to wave- and tide-influenced nearshore-marine set-tings is consistent with a transgressed clastic shelf, and in-terpretations by Grotzinger and Gall (1986) and Tirrul andGrotzinger (1990). Accordingly, the shift to mixed fine-grained clastic-carbonate deposits can be reconciled withclastic shutdown in response to shelf drowning (Cattaneoand Steel, 2003). Forthcoming studies in the area will focuson the petrology and bulk-rock geochemistry of theKilohigok paleosol, as well as on refined sedimentologyand depositional architecture of the Kimerot Group.

Economic considerations

The Bear Creek Hills have been investigated in the past forgold mineralization hosted within meta–iron formationunits (Therriault, 2003). Regionally, the Crazy Bear Meta-morphic Complex, exposed to the east of the study area,contains gold concentrations of up to 190 g/t (from assayanalysis; Therriault, 2003), and the present study area hasbeen investigated in the past by, among others, Bear CreekHills Estates Ltd., Cogema Canada Ltd. and Echo MinesLtd. (Grotzinger and Gall, 1986; Therriault, 2003). How-ever, meta–iron formations in the Bear Creek Hills yieldedonly modest gold concentrations (~10 g/t from assay analy-sis; Therriault, 2003).

On the other hand, field-based gamma-ray spectrometryhad not been employed in the search for uranium mineral-ization across the boundary between the YellowknifeSupergroup and the Kimerot Group. This study yieldeduranium concentrations as high as 121.1 ppm, indicating


Figure 5: Schematic geological section through the Kilohigok paleosol in Bear Creek Hills (note vertical exaggeration). Field view of sectionshown in Figure 3a. Gamma-ray spectrometer profiles constructed from data in Table 1. Satellite image from DigitalGlobe (2014).

that there is some potential for the area. Results are, in part,consistent with what is reported at other locations along theKilohigok paleosol (Ielpi et al., 2015), showing that ura-nium mineralization is preferentially found in associationwith bedrock that underwent intense chemical paleoweath-ering and sericitization.

Acknowledgments

The authors are indebted to H. Steenkamp and S. Basso(Canada-Nunavut Geoscience Office) for their invaluablelogistical support for the project, and B. Davies (Geologi-cal Survey of Canada, Ottawa) for stimulating discussions.Q. Gall is thanked for his insightful and constructive re-view. D. Montgomery with Air Tindi provided safe float-plane operations, and K. Vickers and M. McLean with Dis-covery Mining Services are thanked for expediting servicesand logistical support.

The project is supported by the Canadian Northern Eco-nomic Development Agency’s (CanNor) Strategic Invest-ments in Northern Economic Development (SINED) pro-gram. The senior author is also supported by a DiscoveryGrant from the Natural Sciences and Engineering ResearchCouncil of Canada (NSERC).

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