The 1.9 Ga Kilohigok paleosol and Burnside River Formation, western : stratigraphy and gamma-ray spectrometry

A. Ielpi1,2, R.H. Rainbird2, J.W. Greenman3 and C.G. Creason4

1Canada-Nunavut Geoscience Office, , Nunavut; with Laurentian University as of January 1, 2016, aielpi@ laurentian.ca 2Natural Resources , Geological Survey of Canada, Ottawa, Ontario 3Department of Earth Sciences, Carleton University, Ottawa, Ontario 4College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

This work was part of the second phase of the Geo-mapping for Energy and Minerals (GEM) Program in the Elu Basin area and surround- ings. It is being co-led by the Canada-Nunavut Geoscience Office (CNGO) and the Geological Survey of Canada (GSC). The study area comprises National Topographic System map areas 77A, 77B, 76O, 76N. The objective of this work is to improve the sedimentological framework within the Elu Basin and surrounding area, and to explore its economic potential.

Ielpi, A., Rainbird, R.H., Greenman, J.W. and Creason, C.G.2015: The 1.9 Ga Kilohigok paleosol and Burnside River Formation, western Nunavut: stratigraphy and gamma-ray spectrometry; in Summary of Activities 2015, Canada-Nunavut Geoscience Office, p. 1–10.

Abstract Elu Inlet and Tariyunnuaq (Melville Sound) are located in the of Nunavut (Canada), and are underlain by a succession of Paleo- to Mesoproterozoic sedimentary rocks known as the Elu and Kilohigok basins. This paper focuses on the stratigraphy and gamma-ray spectrometry of the northeastern margin of the Kilohigok Basin, which is exposed along the southern shore, and inland, of Tariyunnuaq. At this location, the Kilohigok Basin is represented by the ca. 1.9 Ga Burnside River Formation, a sandstone-dominated fluvial unit that overlies granitoid and greenstone-belt rocks of the Archean Slave Province. The nonconformable contact between the Slave Province basement rocks and the Kilohigok Basin is character- ized by a distinctive paleosol horizon (the ‘Kilohigok paleosol’). Stratigraphic and gamma-ray spectrometry data were col- lected at several sites across the contact, along an ~80 km transect.

The Kilohigok paleosol is developed at the expense of either granitoid basement or greenstone-belt rocks. Well-developed paleosaprolites derived from the granitoid protoliths demonstrate potential for unconformity-related uranium mineraliza- tion, whereas poorly developed alteration profiles derived from greenstone-belt rocks are overall less prospective. The overlying Burnside River Formation is composed mainly of laterally continuous sandstone sheets, as well as preserved large foreset bars, channel bodies and eolian dunes. Although radioactivity measurements from the Burnside River Forma- tion yielded uranium levels consistent with background values, local coarse-grained bodies contained within paleovalleys cut into basement rocks host nominally higher uranium concentrations. Similarly, above-background levels of radioactivity were recorded at higher stratigraphic levels, notably in proximity to intrabasin-fill surfaces of the unconformity.

Résumé Une succession de roches sédimentaires d’âge paléoprotérozoïque et mésoprotérozoïque, connue sous le nom de bassin d’Elu et bassin de Kilohigok, repose sous le passage d’Elu et la collectivité de Tariyunnuaq (détroit de Melville), tous deux situés dans la région de Kitikmeot au Nunavut, au Canada. Le présent rapport met l’accent sur les travaux de stratigraphie et de spectrométrie gamma réalisés en bordure de la marge nord-est du bassin de Kilohigok, lequel se trouve exposé aussi bien le long du littoral sud de Tariyunnuaq que dans l’arrière-pays. À cet endroit, les roches qui constituent le basin Kilohigok font partie de la formation de Burnside River, âgée de 1,9 Ga; il s’agit d’une unité d’origine fluviale, principalement constituée de grès, qui recouvre des roches granitoïdes et des roches de ceintures de roches vertes d’âge archéen appartenant à la Province des Esclaves. À l’endroit où les roches du bassin de Kilohigok reposent en discordance sur les roches de socle de la Province des Esclaves, un horizon de paléosol distinctif s’est formé (« paléosol de Kilohigok »). Des données stratigraphiques et de spectrométrie gamma ont été recueillies à quelques endroits le long d’un transect d’environ 80 km correspondant à la zone de contact.

This publication is also available, free of charge, as colour digital files in Adobe Acrobat® PDF format from the Canada-Nunavut Geoscience Office website: http://cngo.ca/summary-of-activities/2015/.

Summary of Activities 2015 1 La formation du paléosol de Kilohigok a impliqué à la fois les roches de socle granitoïdes et les roches de ceintures de roches vertes. Des paléosaprolites bien formés provenant des protolites granitoïdes semblent présenter des signes de minéralisation en uranium liée à la discordance, alors que les profils d’altération peu développés qui caractérisent les ceintures de roches vertes s’avèrent moins prometteurs de façon générale. La formation de Burnside River susjacente est principalement composée d’épaisses unités de grès de grande continuité latérale, ainsi que de barres sableuses de front de delta, d’amas de chenaux et de dunes éoliennes conservés. Bien que des mesures de la radioactivité provenant de la forma- tion de Burnside River aient révélé des niveaux de radioactivité conformes aux valeurs de fond, des amas locaux à granulométrie grossière qui se trouvent au fond des paléovallées entaillées dans la roche de socle affichent des taux de con- centration plus élévés d’uranium. Des taux de radioactivité supérieurs aux valeurs de fond ont également été enregistrés à des niveaux stratigraphiques plus élevés, et plus particulièrement à proximité d’aires de remplissage de bassin associées à la discordance.

Introduction Gamma-ray spectrometry data, reported at targeted stations during the 2014 and 2015 field seasons, are contained in The Kilohigok and Elu basins in the Kitikmeot Region of Ielpi et al. (2015)5. Nunavut, containing Paleo- to Mesoproterozoic sedimen- tary rocks (Figure 1), are relatively underexplored compared Geological setting to other Precambrian sedimentary basins in Canada. Dur- The Kilohigok and Elu basins underlie the southeastern rim ing the summers of 2014 and 2015, the Elu Basin Geo- of the younger Amundsen Basin of Arctic Canada (Young, science Project, which was co-led by the Canada-Nunavut 1981), recording a time span of roughly 300 m.y. (ca. 1.97– Geoscience Office and the Geological Survey of Canada, 1.63 Ga; Bowring and Grotzinger, 1992; Heaman et al., had the objective of collecting original geological informa- 1992). However, despite their similar stratigraphy, the tion on the stratigraphy, sedimentology and economic po- Kilohigok and Elu basins likely formed under different tential of the Elu Basin and the northeastern margin of the geodynamic settings. The Kilohigok Basin is a 250 km long adjacent Kilohigok Basin (Ielpi and Rainbird, 2015a). The by 200 km wide domain of sedimentary rocks that are study area encompasses Elu Inlet, Tariyunnuaq (Melville widely exposed on the western shore, and inland, of Kilu- Sound) and northeastern Kiluhiqtuq (), and is hiqtuq (Figure 1). The basin extends northeastward, where centred roughly on latitude 68°15’N, longitude 107°15’W. other prominent exposures occur at the boundary between This area was the focus of exploratory geological mapping Kiluhiqtuq and Tariyunnuaq (Figure 1), the study area of in the late 1970s and early 1980s (Campbell, 1978, 1979; this research. In this area, the northeastern margin of the Campbell and Cecile, 1979, 1981); with the exception of a Kilohigok Basin is unconformably overlain by deposits of Ph.D. thesis by McCormick (1992), it has received little at- the younger 100 km long by 30 km wide Elu Basin (Ielpi tention since then. Many of the Proterozoic basins on the and Rainbird, 2015a). have demonstrated economic viability for uranium, lead-zinc and other metals (Jefferson et al., 2007). The geodynamic history of the Kilohigok and Elu basins The scope of the Elu Basin Geoscience Project therefore in- has been a subject of debate. Based on stratigraphic similar- cludes provision of assessments on the economic potential ities and structural affinities with the nearby Wopmay of the sedimentary basins hosted in the Kitikmeot Region Orogen, Hoffman (1973) proposed an aulacogen (i.e., of Nunavut. aborted-rift basin) model for the development of the Kilo- higok Basin. However, owing to a lack of growth faulting In the study area, two Proterozoic clastic units, the Burn- and magmatism, this hypothesis was refined by Campbell side River and Ellice formations, occur in depositional con- and Cecile (1981), who promoted a model of an intracrat- tact with Archean basement rocks (Figure 1) and represent onic trough related to a hypothetical aulacogen that devel- the main targets for unconformity-related uranium mineral- oped to the north. Yet, ensuing work of Grotzinger and Gall ization. The Ellice Formation was investigated during the (1986) and McCormick and Grotzinger (1992) refuted the 2014 field season in terms of stratigraphy, sedimentology intracratonic-trough model, as a greater amount of field ev- and gamma-ray spectrometry (Ielpi and Rainbird, idence pointed to stratigraphic development and basin evo- 2015a, b). Focusing on the older Burnside River Forma- lution consistent with a foreland basin concomitant with the tion, a similar approach was followed during the 2015 field Thelon orogeny (Figure 1; Tirrul, 1985; Tirrul and Grotzin- season. The Burnside River Formation and the underlying alteration profile developed on basement rocks (‘Kilohigok 5 paleosol’) demonstrate prospectivity for uranium in places, CNGO Geoscience Data Series GDS2015-007, containing the data or other information sources used to compile this paper, is and thus provide the specific target for the stratigraphic and available online to download free of charge at http://cngo.ca/ gamma-ray spectrometry analyses presented here. summary-of-activities/2015.

2 Canada-Nunavut Geoscience Office Figure 1: Geological framework of the northeastern margin of the Kilohigok Basin and overlying rocks of the Elu Basin. Modified, in part, from Campbell (1979), Campbell and Cecile (1979) and Ielpi and Rainbird (2015a). Geochronology from Bowring and Grotzinger (1992) and Heaman et al. (1992).

ger, 1990). Similarly, the Elu Basin was first interpreted as relate to minor, postdepositional, extensional to strike-slip the product of rift tectonics (Campbell, 1979), a conjecture displacement. revised in favour of an intracratonic-sag model related to Stratigraphic framework thermal insulation (Rainbird et al., 2014). The structural setting of the study area is characterized by gentle folding The basement rocks within the study area are part of the related to the Gordon Bay Arch (Figure 1; McCormick and Archean Slave Province, which consists mainly of both Grotzinger, 1992), a regional-scale tectonic feature that weakly deformed granitoid rocks and heavily deformed probably formed and migrated toward the foreland in re- belts of mafic (meta)volcanic and (meta)sedimentary rocks sponse to crustal loading (i.e., thrust stacking) at the front (Figure 1), the latter composing the north-trending Hope of the Thelon Orogen. Fault structures are subordinate and Bay greenstone belt (Sherlock et al., 2012). The Slave

Summary of Activities 2015 3 Province is nonconformably covered by Proterozoic de- early July 2015, covering parts of the NTS areas 76O, 76N, posits that show little deformation, lack evidence of meta- 77Aand 77B. Observations on the bulk composition and al- morphism and are arranged in three unconformity-bounded teration state of paleoweathered basement rocks (Figures sequences with supraregional traceability (Rainbird and 2, 3) were gathered in the field using hand lenses. Estimates Davis, 2007). The Burnside River Formation (Sequence I) on gross mineral abundance were performed using compar- is up to 3.5 km thick and consists of crossbedded fluvial ative tables. Observations on the stratigraphic development sandstone and minor conglomerate. Along the nonconfor- and depositional architecture of the Burnside River Forma- mity with the Slave Province, the Burnside River Forma- tion (Figure 4) were collected on continuous stepped-cliff tion overlies the Kilohigok paleosol. The Tinney Cove For- exposures, in places up to 3 km along strike and 500 m mation (Sequence II) is a coarse-clastic talus deposit less thick. The sedimentology of the Burnside River Formation than 50 m thick. It was developed at the expense of the was assessed along the same exposures, including Burnside River Formation and occurs along cliff exposures paleoflow measurements (n = 1540) from crossbeds. The at Kuururjuaq Point (Figure 1). The fluvial-eolian to reconstruction of large-scale depositional architecture was nearshore-marine Ellice and Parry Bay formations (Se- aided by high-resolution satellite imagery, which included quence III) comprise a ≤2 km thick succession of clastic RapidEyeTM and PléiadesTM imagery with 5.0 m and 0.5 m and carbonate rocks that is widely exposed in Elu Inlet and of ground resolution, respectively. northern Tariyunnuaq (Ielpi and Rainbird, 2015a). These The radiation of basement rocks and overlying deposits strata are intersected by diabase dykes and sills related to (Figure 5) was assessed using a Radiation Solutions Inc. the Franklin igneous event (Heaman et al., 1992) and, in RS-125 hand-held spectrometer. The database of spectral places, covered by clastic rocks of probable Paleozoic age signatures includes readings of radioactive dose rate (ex- (O’Neill, 1924; Thorsteinsson and Tozer, 1962). pressed in nanosieverts/hour or nSv/h) and extrapolated Methods abundances of potassium (%), uranium (ppm) and thorium (ppm). Vertical lithological and spectrometry profiles were Helicopter-supported mapping and ground traversing were measured throughout the Kilohigok paleosol at several lo- performed out of the Doris North mining camp of TMAC cations, in conjunction with bulk-rock sampling for future Resources Inc. and a remote field camp during late June to analysis.

Figure 2: Representative rock types of the Archean Slave Province and derived alteration profile, outcropping mostly in the southwestern part of the study area (Figure 1; lens cap is ~5 cm across): a) fresh unaltered syenogranite intersected by quartz veins; b) lower saprolite su- perimposed on (a), showing reddening related to enrichment in hematite; c) upper saprolite superimposed on (b), showing intense illitization that resulted in loss of K-feldspar and plagioclase, and sericite crystallization; d) gabbro intrusions, although subordinate, occur- ring in isolated outcrops and locally collected for carving stone.

4 Canada-Nunavut Geoscience Office Figure 3: Representative rock types of the Archean Hope Bay greenstone belt and derived alteration profile, outcropping in the northeast- ern part of the study area (Figure 1): a) hydrothermally altered, tholeiitic and iron-rich basalt; lens cape (circled) is ~5 cm across; b) greenschist-grade metamorphic rocks derived from pelitic protolith; hammer is ~20 cm long; c) hematitic, fine-grained sandstone and siltstone of turbiditic origin; field book is 18 cm tall; d) deeply weathered profile superimposed on (a); field book is 18 cm tall.

Field results An overlying ‘upper saprolite’ zone shows extensive tex- tural breakdown and is dissected by centimetre-spaced Granitoid paleosol joints oriented vertically with respect to the contact above. The features of paleosol horizons developed on granitic The upper saprolite is a pale yellow-green colour due to ex- rocks of the Archean Slave Province were assessed at 10 tensive sericitization (Figure 2c). This phase contains re- sites along an ~40 km transect (Figure 1). At these sites, the duced amounts of plagioclase and K-feldspar as a result of horizons can be subdivided in three zones, based on texture illitization (Rainbird et al., 1990; Fedo et al., 1997), and its and bulk petrology. A lowermost horizon consists of rela- mineralogy is dominated by quartz and sericite, with tively unaltered syenogranite (K-feldspar>quartz>plagio- selvages of clay minerals along joints. A horizontally bed- clase>muscovite), commonly intersected by decimetre- ded to massive pavement of pebbly sandstone sharply over- scale quartz veins (Figure 2a), with gneissic fabric devel- lies the upper saprolite, which transitions upward over a oped in local shear zones. Subordinate gabbro occurs as few tens of decimetres into an iron-oxide–rich, crossbed- decimetre to metre-scale xenoliths, or decametre-scale in- ded quartzarenite. In places, the nonconformity between trusions (Figure 2d), the latter locally collected as carving basement rocks and the Burnside River Formation displays stone (Beauregard, 2014). up to 3 m of erosional relief over a distance of 20 m along strike (Figure 4c). Closer to the contact with the Burnside River Formation, Greenstone paleosol the unaltered granite transitions to a ‘lower saprolite’zone, ranging in thickness from 2 to 8 m. The lower saprolite dis- The features of paleosol horizons developed on the plays moderate fracturing (although no systematic jointing Archean Hope Bay greenstone belt were assessed at three is observed) and is strongly reddened (Figure 2b). The red- locations along a 20 km transect. At these sites, the dening is related to hematization and sericitization (i.e., Burnside River Formation overlies both mafic volcanic and breakdown of iron and magnesium oxides and reprecipi- related highly deformed sedimentary rocks (Figure 3a) that tation of iron on clay minerals derived from plagioclase are locally metamorphosed to greenschist facies (Figure weathering; cf. Gall, 1994). Accordingly, the bulk mineral- 3b, c). Good exposures are located in the headland to the ogy of the lower saprolite is characterized by quartz, K- northeast of Hope Bay (Figure 1), where a tectonic assem- feldspar, muscovite, hematite and sericite. blage of fractured gabbro and massive, tholeiitic and iron-

Summary of Activities 2015 5 rich basalt (clinopyroxene>plagioclase>hematite>olivine) Physical breakdown occurred in isolated, cobble-sized an- is overlain by, and lateral to, a succession of steeply dip- gular fragments that show a lesser degree of mineralogical ping, folded, Archean metasedimentary rocks. Mafic vol- alteration, and tight folding in the Archean sedimentary canic products attain a dark green colour related to hydro- rocks likely favoured the jointing and mechanical break- thermal alteration along the Hope Bay greenstone belt down. As a result, the uppermost portion of the paleosol de- (Sherlock et al., 2012). The Archean sedimentary rocks are veloped on Archean sedimentary rocks consists of a gran- fine-grained wacke and mudstone. The paleosol horizon is ule- to sand-grained, angular regolith that lacks a significant developed on both basalt and folded sedimentary rocks, change in mineralogy with respect to the underlying and is generally less than 1 m thick. Within this horizon, protolith. The paleosol is sharply overlain by lensoid bod- deeply fractured and weathered basalt is enriched in sericite ies of rounded-pebble conglomerate locally derived from and chlorite (cf. Rye and Holland, 2000), and hematite is rocks of the Hope Bay greenstone belt (Figure 4b). This progressively diminished toward the top (Figure 3d). conglomerate is crossbedded and preserved within ero-

Figure 4: Stratigraphy and field aspect of the Burnside River Formation. The stratigraphic column, is in part, modified from McCormick (1992). Representative paleoflow data collected at different stratigraphic horizons throughout the northeastern Kilohigok Basin are re- ported in rose diagrams with linear scale, average vector and 95% confidence arc. Abbreviations: ms, medium-grained sand; cs, coarse- grained sand; gr, granules; pb, pebbles. Photographs: a) coarse-grained, trough-crossbedded sandstone organized in metre-thick units bounded by erosional contacts; field book is 18 cm tall; b) pebble conglomerate derived from the Hope Bay greenstone belt and contained within paleovalleys incised into basement rocks; lens cap (circled), is ~5 cm across; c) nonconformity between granite-derived saprolite of the Archean Slave Province (SP Gr) and basal crossbedded sandstone of the Burnside River Formation (BR Fm); field book is 18 cm tall.

6 Canada-Nunavut Geoscience Office sional depressions cut on basement rocks, which represent posits and consist of scoop-shaped lithosomes that are 500– paleovalleys (Ielpi and Rainbird, 2015a) up to 8 m deep and 1200 m wide and up to 12 m thick (width:thickness ratios ~30 m wide. The conglomerate fines upward abruptly into ranging from 80 to 100). Second-order surfaces within the coarse-grained to pebbly, crossbedded sandstone over less channel bodies cut each other, and point to accretion con- than a metre. sistent with paleoflow indicators. The orientation of these surfaces suggests mildly dispersed, northward sediment Burnside River Formation paleotransport (Figure 4), a vector roughly perpendicular In the study area, the most complete succession of Burnside to that of adjacent sandstone sheets. Eolian dunes form ap- River Formation occurs along Buchan Bay (Figure 1), proximately 5% of the deposits and consist of up to 30 m where a thickness of ~1 km is exposed. The formation is thick sets of steeply inclined cross-strata (>25°) that are lat- dominated by coarse-grained, iron-oxide–rich arkose, with erally continuous for more than 600 m along strike. minor conglomerate and fines. In outcrop, the sedimentary Second-order surfaces indicate a highly focused, unimodal motif exhibits a repetitive character, with strata between accretion toward the west-southwest. 0.5 and 2 m thick and bounded by laterally continuous (>100 m), low relief (<50 cm), planar erosional surfaces. The assemblage of fluvial-eolian architectural elements is The erosional surfaces are floored by pebble pavements de- consistent with a sheet flow–dominated alluvial plain rived mainly from granitoid rocks and rarely from green- transected locally by mature trunk channels capable of gen- stone-belt rocks. Locally, the pavements are composed of erating large downstream-accretionary bars. These chan- flattened, well-rounded pebbles with frosted surfaces, nels had paleoflow inconsistent with that of adjoining sand overlain by a similarly frosted, medium-grained quartz- sheets, thereby suggesting that the Burnside River Forma- arenite. tion could have been generated by multiple, interacting al- luvial systems with basin-centripetal drainage (Ielpi, Strata display trough crossbedding and minor planar 2013). Episodes of eolian reworking of the sediments into crossbedding (Figure 4a), the latter with well-developed dune fields and small draa (Mountney, 2006) point to con- soft-sediment deformation and flow-induced shear struc- temporaneous fluvial shutdown or sand winnowing along tures. Minor planar intervals of fine-grained maroon sand- interfluves. stone and siltstone are ripple crosslaminated. Overall, these features are consistent with poorly confined alluvial sys- Gamma-ray spectrometry tems characterized by sustained perennial flow, an assump- tion based on the lateral continuity of the strata and the pre- The radioactive properties of basement rocks and sedimen- dominance of crossbedding over planar stratification tary rocks were investigated in terms of total dose rates, and (Ielpi, 2012; Rygel et al., 2015). Episodes of wind rework- abundance of potassium, uranium and thorium. Above- ing are evidenced by eolian gravel lags and sheets (frosted background dose rates were recorded in places along the pebbles and quartzarenite; Mountney, 2006). Kilohigok paleosol (~250–450 nSv/h), whereas both base- ment rocks and sedimentary rocks at different stratigraphic The large-scale depositional architecture of the Burnside levels yielded only background levels of radiation River Formation is characterized by four elements: fluvial (<200 nSv/h). Thirteen sites along the Kilohigok paleosol sand sheets, large foreset bars, channel bodies and eolian show that the alteration profiles on granitoid rocks have dunes. Sandstone sheets represent roughly 70% of the de- higher prospectivity for uranium than those developed on posits and consist of tabular stacks of strata up to 500 m greenstone-belt rocks (Figure 1). thick that show little or no change in thickness for up to 5 km along strike. Satellite images show that individual The highest values of radioactivity were recorded along the strata within the sandstone sheets attain width:thickness ra- Buchan Hills, close to the Gordon Bay Arch, where the tios as high as 3000, a feature consistent with sheet-braided nonconformity between the Slave Province granite and fluvial systems (Fuller, 1985). Paleoflow indicators col- Burnside River Formation is folded in a large northwest- lected on sandstone sheets point to unimodal, focused trending syncline (Figure 1). At these locations, dose rates drainage toward the west-northwest (Figure 4). Large of up to 461.8 nSv/h were recorded, corresponding to peak foreset bars account for ~20% of the deposits, and consist concentrations of uranium and thorium of up to 29.7 and of sets of gently inclined (<10°) strata up to 20 m thick that 54.6 ppm, respectively (stations 15-5 and 15-29). A spec- pinch out in less than 50 m downstream. Second-order sur- trometer profile through the well-developed, granitoid-de- faces (sensu Rainbird, 1992) point to accretion consistent rived Kilohigok paleosol (type A in Figure 5; station 15-7) with unimodal, northwestward paleoflow (Figure 4). Over- demonstrates a strong, direct correlation between dose rate all, these features are consistent with large midchannel bars and uranium abundance, yet weaker correlations between dominated by downstream accretion and generated within dose rate and thorium-potassium abundance. Also, it ap- deep, open-water channels at high-flood stage (Ielpi and pears that the uranium mineralization is concentrated along Ghinassi, 2015). Channel bodies represent ~5% of the de- the lower saprolite and in the gravelly pavement flooring

Summary of Activities 2015 7 Figure 5: Representative gamma-ray spectrometry profiles of the Kilohigok paleosol. Horizons developed on granitoid rocks (type A) have well-developed saprolite and demonstrate potential for unconformity-related uranium mineralization. Horizons developed on mafic volca- nic rocks and associated (meta)sedimentary rocks (type B) have poorly developed saprolite, and lesser concentrations of uranium are found only within basal conglomerate bodies. the nonconformity between the Slave Province granite and Burnside River Formation reveals a strong positive correla- Burnside River Formation (Figure 5). By comparison, tion between dose rate and abundance of uranium and granitoid exposures located a few hundred metres away potassium, whereas no apparent correlation exists with the from the Kilohigok paleosol (station 15-8) yielded peak abundance of thorium (Figure 5). By comparison, mafic dose rates of 205.4 nSv/h, corresponding to peak concen- volcanic products exposed ~50 m below the Kilohigok trations of uranium and thorium of 6.9 and 32.9 ppm, re- paleosol (station 14-6) yielded a peak dose rate of 55.6 nSv/ spectively. Exposures of Burnside River Formation at a h, corresponding to peak concentrations of uranium and stratigraphic level ~100 m above the Kilohigok paleosol thorium of 1.8 and 10.7 ppm, respectively. The unconform- (station 15-2) yielded peak dose rates of 116.1 nSv/h, able contact between the Burnside River and Tinney Cove corresponding to peak concentrations of uranium and formations (~50 m above the Kilohigok paleosol at thorium of 5.2 and 18 ppm, respectively. Kuurujuaq Point; Figure 1; station 14-1) yielded a peak dose rate of 111 nSv/h, corresponding to peak concentra- tions of uranium and thorium of 5.9 and 24 ppm, respect- Lower levels of radioactivity were recorded in the headland ively. east of Hope Bay, where the Kilohigok paleosol is poorly developed over the Hope Bay greenstone belt (type B in Discussion and conclusions Figure 5; stations 14-8, 15-11 and 15-12) and where the nonconformity with the overlying Burnside River Forma- During the second year of field activities, the Elu Basin tion is folded in a gentle syncline (Figure 1). There, a peak Geoscience Project focused on the stratigraphy and dose rate of 115.9 nSv/h was recorded, corresponding to gamma-ray spectrometry of the 1.9 Ga Burnside River For- peak concentrations of uranium and thorium of 7.2 and mation exposed in Tariyunnuaq (Melville Sound), and its 22.7 ppm, respectively. A spectrometer profile through the underlying paleosol developed on granitoid and green- paleosol and overlying pebble conglomerate of the basal stone-belt rocks of the Archean Slave Province. The field

8 Canada-Nunavut Geoscience Office investigations confirm a stratigraphic subdivision into Acknowledgments three unconformity-bounded stratigraphic sequences for both the Elu Basin and the northeastern margin of the un- The authors thank TMAC Resources Inc. for providing an derlying Kilohigok Basin. Field-based gamma-ray spec- operational base at their Doris North camp, and particularly trometry analyses demonstrate a cost- and time-effective for the assistance of A. Buchan, M. McCreadie, N. de method for prospecting for radionuclide mineralization, es- Ruyter and S. Hudson. F. Jones and Z. Dippo from Great pecially when focused along nonconformable surfaces be- Slave Helicopters are warmly thanked for safe piloting. tween crystalline and sedimentary rocks and, to a lesser de- K. Vickers and M. McLean from Discovery Mining Ser- gree, along intrabasin-fill surfaces of unconformity. vices, G.Parsons from the Polar Continental Shelf Program at Resolute and P. Philstone from Air Tindi are thanked for Preliminary investigations on the sedimentology and valuable expediting services and logistical support. R. Ber- depositional architecture of the Burnside River Formation man is warmly acknowledged for his insightful reviews. depict a sandstone-dominated fluvial system characterized by deposition on wide, unconfined plains subject to sheet The Canadian Northern Economic Development Agency’s flooding. Locally, preservation of large downstream- (CanNor) Strategic Investments in Northern Economic De- accretionary bars, large channel bodies and eolian dunes velopment (SINED) and the Geo-mapping for Energy and point to major fluvial trunks transecting the alluvial plain, Minerals (GEM) programs provided financial support for and sided by ephemeral eolian dunes, a possible expression this work. The senior author is supported by a research of interfluves (cf. Ielpi and Rainbird, 2015b). The overall grant from the Natural Sciences and Engineering Research northwestward paleodrainage coincides with previous Council of Canada (NSERC). studies on the Burnside River Formation exposed in Natural Resources Canada, Earth Sciences Sector contri- Kiluhiqtuq (Bathurst Inlet; Campbell and Cecile, 1979, bution 20150337 1981; McCormick and Grotzinger, 1992), suggesting sedi- ment production and routing from the Thelon Tectonic Zone. Local paleoflow dispersion may have responded to References the active growth of folds related to the uplift of the Gordon Beauregard, M. 2014: Results from the 2010–2014 carving stone Bay Arch, as suggested by McCormick and Grotzinger deposit evaluation program; presentation at 2014 Nunavut (1992). Overall, these features support a depositional setting Mining Symposium, April 7–10, Iqaluit, Nunavut. consistent with a synorogenic, fluvial-dominated foreland Bowring, S.A. and Grotzinger, J.P. 1992: Implications of new basin. chronostratigraphy for tectonic evolution of Wopmay Orogen, northwest Canadian Shield; American Journal of Science, v. 292, p. 1–20. Economic considerations Campbell, F.H.A. 1978: Geology of the Helikian rocks of the Bathurst Inlet area, Coronation Gulf, Northwest Territories; Unconformity-related deposits are widely considered to be in Current Research, Part A, Geological Survey of Canada, the primary form of uranium mineralization in many Pre- Paper 78-1A, p. 97–106. cambrian basins within the Canadian Shield, the most Campbell, F.H.A. 1979: Stratigraphy and sedimentation in the prominent being the high-grade deposits of the Athabasca Helikian Elu Basin and Hiukitak Platform, Bathurst Inlet– Basin (Jefferson et al., 2007). As envisaged by Gall (1994), Melville Sound, Northwest Territories; Geological Survey similar styles of mineralization could characterize the basal of Canada, Paper 79-8, 19 p. unconformity of economically underexplored basins such Campbell, F.H.A. and Cecile, M.P. 1979: The northeastern margin as the Elu and Kilohigok. Investigations on the alteration of the Aphebian Kilohigok Basin, Melville Sound, Victoria profile underlying the 1.6 Ga Ellice Formation in the Elu Island, District of Franklin; in Current Research, Part A, Geological Survey of Canada, Paper 79-1A, p. 91–94. Basin demonstrated only background levels of radioactiv- Campbell, F.H.A. and Cecile, M.P. 1981: Evolution of the Early ity (Ielpi and Rainbird, 2015a). By comparison, field mea- Proterozoic Kilohigok Basin, Bathurst Inlet–Victoria Is- surements from the 1.9 Ga Kilohigok paleosol yielded land, Northwest Territories; in Proterozoic Basins of Can- above-background concentrations of uranium (up to ada, F.H.A. Campbell (ed.), Geological Survey of Canada, 30 ppm), especially when it developed on granitoid rocks Paper 81-10, p. 103–131. of the Archean Slave Province and in proximity to large- Fedo, C.M., Young, G.M., Nesbitt, H.W. and Hanchar, J.M. 1997: scale folds. In contrast, those portions of the Kilohigok Potassic and sodic metasomatism in the Southern Province paleosol derived from rocks of the Hope Bay greenstone of the Canadian Shield: evidence from the Paleoproterozoic Serpent Formation, Huronian Supergroup, Canada; Precam- belt demonstrated lesser prospectivity. Given these prelim- brian Research, v. 84, p. 17–36. inary observations, it is suggested that future exploration Fuller, A.O. 1985: A contribution to the conceptual modeling of focus on the lower portions of granitoid-derived alteration pre-Devonian fluvial systems; Transactions of the Geologi- profiles, as well as the conglomeratic bodies directly cal Society of South Africa, v. 88, p. 189–194. overlying stratigraphic surfaces of nonconformity or Gall, Q. 1994: The Proterozoic Thelon paleosol, Northwest Terri- unconformity. tories, Canada; Precambrian Research, v. 68, p. 115–137.

Summary of Activities 2015 9 Grotzinger, J.P. and Gall, Q. 1986: Preliminary investigations of mation (1.9 Ga), Kilohigok Basin, N.W.T., Canada; Basin early Proterozoic Western River and Burnside River forma- Research, v. 4, p. 253–278. tions: evidence for foredeep origin of Kilohigok Basin, Mountney, N.P. 2006: Eolian facies models; in Facies Models Re- N.W.T., Canada; in Current Research, Part A, Geological visited, H.W.Posamentier and R.G.Walker (ed.), Society for Survey of Canada, Paper 86-1A, p. 95–106. Sedimentary Geology (SEPM), Special Publication 84, Heaman, L.M., LeCheminant, A.N. and Rainbird, R.H. 1992: Na- p. 23–88. ture and timing of Franklin igneous events, Canada: impli- O’Neill, J.J. 1924: Geology of the Arctic coast of Canada, west of cations for a Neoproterozoic mantle plume and the break-up Kent Peninsula; in Report of the Canadian Arctic Expedition of Laurentia; Earth and Planetary Science Letters, v. 109, 1913–18, v. 11, Geology and Geography, Part A, 107 p. p. 117–131. Rainbird, R.H. 1992: Anatomy of a large-scale braid-plain Hoffman, P.F. 1973: Evolution of an early Proterozoic continental quartzarenite from the Neoproterozoic Shaler Group, Victo- margin: the Coronation geosyncline and associated aulaco- ria Island, Northwest Territories, Canada; Canadian Journal gens of the northwestern Canadian Shield; Royal Society of of Earth Sciences, v. 29, p. 2537–2550. London, Philosophical Transactions A, v. 237, p. 547–581. Rainbird, R.H. and Davis, W.J. 2007: U-Pb detrital zircon geo- Ielpi, A. 2012: Anatomy of major coal successions: facies analysis chronology and provenance of the late Paleoproterozoic and sequence architecture of a brown coal-bearing valley fill Dubawnt Supergroup: linking sedimentation with tectonic to lacustrine tract (Upper Valdarno Basin, northern reworking of the western Churchill Province, Canada; Geo- Apennines, Italy); Sedimentary Geology, v. 265–266, logical Society of America Bulletin, v. 119, p. 314–328. p. 163–181. Rainbird, R.H., Ielpi, A., Long, D.G.F. and Donaldson, J.A. 2014: Ielpi, A., 2013: Frequency-reliant correlative patterns of asym- Similarities and paleogeography of late Paleoproterozoic metric lacustrine-paralic sequences: a genetic approach to terrestrial sandstone deposits on the Canadian Shield: prod- the late Miocene Bithynia Marlstones of the southeastern uct of Hudsonian orogenesis; Geological Society of Amer- Volterra Basin, Italy; Journal of Sedimentary Research, ica, Abstract with Programs, v. 46, p. 89. v. 83, p. 377–394. Rainbird R.H., Nesbitt H.W. and Donaldson, J.A. 1990: Formation Ielpi, A. and Ghinassi, M. 2015: Planview style and palaeodrain- and diagenesis of a sub-Huronian saprolith: comparison age of Torridonian channel belts: Applecross Formation, with a modern weathering profile; The Journal of Geology, Stoer Peninsula, Scotland; Sedimentary Geology, v. 325, v. 98, p. 801–822. p. 1–16. Rye, R. and Holland, H.D. 2000: Geology and geochemistry of Ielpi, A. and Rainbird, R.H. 2015a: Geological framework of the paleosols developed on the Hekpoort Basalt, Pretoria 1.9–1.6 Ga Elu Basin, western Nunavut: representative Group, South Africa; American Journal of Science, v. 300, sedimentology, gamma-ray spectrometry and lithogeo- p. 85–141. chemistry; in Summary of Activities 2014, Canada-Nunavut Geoscience Office, p. 89–96. Rygel, M.C., Lally, C., Gibling, M.R., Ielpi, A., Calder, J.H. and Bashforth, A.R. 2015: Sedimentology and stratigraphy of Ielpi, A. and Rainbird, R.H. 2015b: Architecture and morphody- the type section of the Pennsylvanian Boss Point Formation, namics of a 1.6 Ga fluvial sandstone: Ellice Formation of Joggins Fossil Cliffs, Nova Scotia, Canada; Atlantic Geol- Elu Basin, Arctic Canada; Sedimentology, v. 62, p. 1950– ogy, v. 51, p. 1–43. 1977. doi:10.1111/sed.12211 Ielpi, A., Rainbird, R.H., Greenman, J.W. and Creason, C.G.2015: Sherlock, R.L., Shannon, A., Hebel, M., Lindsay, D., Madsen, J., Data table accompanying “The 1.9 Ga Kilohigok paleosol Sandeman, H., Hrabi, B., Mortensen, J.K., Tosdal, R.M. and and Burnside River Formation, western Nunavut: stratigra- Friedman, R. 2012: Volcanic stratigraphy, geochronology, phy and gamma-ray spectrometry”; Canada-Nunavut and gold deposits of the Archean Hope Bay greenstone belt, Geoscience Office, Geoscience Data Series GDS2015-007, Nunavut Canada; Economic Geology, v. 107, p. 991–1042. Microsoft® Excel® file. Thorsteinsson, R. and Tozer, E.T. 1962: Banks, Victoria and Jefferson, C.W., Thomas, D.J., Gandhi, S.S., Ramaekers, P., Stefansson Islands, Arctic Archipelago; Geological Survey Delaney, G., Brisbin, D., Cutts, C., Portella, P. and Olson, of Canada, Memoir 330, 85 p. R.A. 2007: Unconformity-associated uranium deposits of Tirrul, R. 1985: Nappes in the Kilohigok Basin, and their relation the Athabasca Basin, Saskatchewan and Alberta; in to the Thelon tectonic zone, District of Mackenzie; in Cur- EXTECH IV: Geology and Uranium EXploration TECH- rent Research, Part A, Geological Survey of Canada, Paper nology of the Proterozoic Athabasca Basin, Saskatchewan 85-1A, p. 407–420. and Alberta, C.W. Jefferson and G.D. Delaney (ed.), Geo- Tirrul, R. and Grotzinger, J.P. 1990: Early Proterozoic collisional logical Survey of Canada, Bulletin 588, p. 23–67. orogeny along the northern Thelon tectonic zone, Northwest McCormick, D.S. 1992: Evolution of an early Proterozoic Territories, Canada: evidence from the foreland; Tectonics, alluvially-dominated foreland basin, Burnside Formation, v. 9, p. 1015–1036. Kilohigok Basin, N.W.T., Canada; Ph.D. thesis, Massachu- Young, G.M. 1981: The Amundsen embayment, Northwest Terri- setts Institute of Technology, Cambridge, Massachusetts, tories: relevance to the upper Proterozoic evolution of North 547 p. America; in Proterozoic Basins of Canada, F.H.A. Campbell McCormick, D.S. and Grotzinger, J.P.1992: Evolution and signifi- (ed.), Geological Survey of Canada, Paper 81-10, p. 203– cance of an overfilled alluvial foreland basin: Burnside For- 211.

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