The Athabasca Basin Ore-Systems Project: Project Update ... · near-infrared (NIR, 780 to 1300 nm), and short-wave infrared (SWIR, 1300 to 2500 nm) regions. Spectral resolution ranges

Saskatchewan Geological Survey 1 Summary of Investigations 2013, Volume 2

The Athabasca Basin Ore-Systems Project: Project Update and Preliminary Findings From the Southwest Athabasca Basin

Sean A. Bosman, Paul Ramaekers 1, Eli Wiens 2, Jessica Poncsak 3, and Graham McKellar 2

Bosman, S.A., Ramaekers, P., Wiens, E., Poncsak, J., and McKellar, G. (2013): The Athabasca Basin ore-systems project: project update and preliminary findings from the southwest Athabasca Basin; in Summary of Investigations 2013, Volume 2, Saskatchewan Geological Survey, Sask. Ministry of the Economy, Misc. Rep. 2013-4.2, Paper A-3, 10p.

Abstract The objective for the Athabasca Basin ore-systems project is to create a geologically significant three-dimensional (3-D) model of the Athabasca Basin. The geological framework will act as a display area for various datasets, both new and old, that can be interpreted in the 3-D environment. The most significant components for advancement of the Athabasca Basin 3-D model include: 1) data collection necessary to construct a best-fit geologic model for the Athabasca Basin, 2) regional compilation of geoscience information, and 3) generation of new data.

During its third year, the program has included the collection of: 1) several supplementary geochemical datasets, 2) additional spectral data, and 3) drillcore data, including sandstone and basement logs from the Wheeler River and McGowan Lake areas and archived drillcores in Regina. Geochemical data were collected from drillcore samples of the Athabasca Group in order to build on previous datasets and now includes a total of 837 outcrop analyses and 656 drillcore analyses. Collection of spectral data, utilizing a portable spectroradiometer, continued in the summer of 2013. A total of 29 drillcores have now been analysed with downhole sample spacing between 0.75 and 1.5 m; the raw spectra are now available online.

Drillcore logging and stratigraphic interpretation continues to aid in refinements to the Athabasca Basin framework geology designed to be used in the 3-D modelling. Work continued in the area south of the Carswell impact structure on the west side of the basin. Nearly all the units there are uniformly sandy. Marker beds are rare or lacking and some of the units pinch out near the Clearwater Domain making correlations difficult. These granites seem to have been a watershed during the initial stages of Read Formation deposition separating (parts of?) the Jackfish basin in the west from the rest of the Athabasca Basin. Work is continuing on the relationship between the eolian-dominated unit (Smart Formation), west of the Clearwater Domain, and the fluvial-dominated units (Read and Manitou Falls formations) which were initially deposited on, east of the Clearwater Domain. Present work seems to indicate that the Smart and Read formations may be partial lateral equivalents of one another east of the Clearwater Domain.

Keywords: Athabasca Basin, uranium ore systems, Athabasca Group, lithostratigraphy, Read Formation, Smart Formation, Manitou Falls Formation, digital core logging, 3-D modelling, infrared spectroradiometer, geochemistry, Clearwater Domain, eolian deposits.

1. Introduction The Saskatchewan Geological Survey’s Athabasca Basin ore-systems project is a publicly funded geoscience initiative that builds on past Athabasca Basin projects including EXploration and TECHnology Initiative IV (EXTECH IV) (Jefferson and Delaney, 2007), Saskatchewan Geological Survey (SGS) lithostratigraphic work (Bosman and Schwab, 2009), and basement mapping peripheral to the basin (Card, 2009). In general, ore-systems projects are designed to study both the regional and local processes involved in the genesis of ore deposits in a particular environment, rather than using the traditional ore-deposit model approach which focuses on the host rocks. The goal of the Athabasca Basin ore-systems project is a better understanding of processes that have made the Athabasca region a prolific source of uranium since the 1950s.

1 MF Resources, 832 Parkwood Dr. S.E., Calgary, AB T2J 3W7. 2 Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2. 3 Department of Geology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2.


The Athabasca Basin ore-systems project is a multi-faceted initiative that involves both regional compilation and new geoscience data available in the 3-D environment 4. The project has several components, the most significant ones being: 1) field studies to further our understanding of the Athabasca Group and the underlying basement, 2) regional compilation of available geoscience information, and 3) generation of new data and their integration with existing data in order to better understand the ore-forming processes (Bosman et al., 2011, 2012).

During the past research year, data of several types were collected and produced from a variety of areas in the Athabasca Basin region. This paper describes how the new data were collected, their current availability and, if available, where they can be obtained. It also provides a preliminary interpretation of lithostratigraphic relations in the southwest part of the basin, specifically the relationship between the Smart and Read formations (Figure 1).

2. Data Collection in 2013

a) Geochemical Data

In April of 2013, an additional 141 geochemical results from Athabasca Group drillcore samples stored at the Subsurface Geological Laboratory (SGL) in Regina were released (Bosman and Card, 2013a – Data File 32). Similar to previous data files (Data Files 29, 30, and 31), the samples in this report were processed at the Saskatchewan Research Council in Saskatoon, Saskatchewan. They were analysed with the Sandstone Exploration Package (ICPMS 1), which incorporates three separate analytical techniques: inductively coupled plasma mass spectroscopy (ICP–MS) partial digestion for trace elements; ICP–MS total digestion for trace elements; and ICP–Optical Emission Spectrometry (ICP–OES) total digestion for major and minor elements. Drillcores were sampled systematically at ~20 m spacing, and the analyses included blind repeats, lab standards and lab repeats. Additional sampling of drillcores containing Athabasca Group rocks for geochemical analysis was completed in the summer of 2013, following the methods described above with 129 new analytical results released in November 2013 (Bosman and Card, 2013b – Data File 33). These two releases build on a previous geochemical dataset that includes analyses published by Card et al. (2011), Card and Bosman (2012), and Bosman and Card (2012) for a combined total of 837 outcrop and 656 drillcore analyses. An industry drillcore dataset (Saskatchewan Ministry of Energy and Resources, 2010), which helped initiate the SGS geochemical compilation, uses similar sampling techniques and methods to those indicated above, and will soon be amended to include an additional 58 samples for a total of 1,013 drillcore analyses. A multivariate analysis of the outcrop lithogeochemical data was presented at the 2012 GAC/MAC annual meeting in St. John’s, Newfoundland (Ramaekers et al., 2012). Future planned additions to the Athabasca Basin geochemical dataset will include further systematic sampling of drillcores.

b) Spectral Data

Collecting spectral data is another component of the Athabasca Basin ore-systems study, which is conducted in order to assist with mapping regional diagenetic trends, similar to the studies completed by Earle and Sopuck (1989). To date, 29 drillcores have been analysed using a FieldSpec® Pro FR portable spectroradiometer (Analytical Spectral Devices, Inc.). This instrument measures spectral radiance in the visible (VIS, 350 to 780 nm), near-infrared (NIR, 780 to 1300 nm), and short-wave infrared (SWIR, 1300 to 2500 nm) regions. Spectral resolution ranges from about 3 nm, in the visible and near-infrared regions, to 10 nm in the SWIR region (Percival et al., in press). Sample spacing of 75 cm was used initially, but was increased to 1.5 m to improve productivity and to be more in line with industry collection techniques. Non-systematic analyses were also conducted on features such as fractures, mudstone/siltstone beds, colour variations, clay intraclasts, and any other interesting characteristics of the core.

Processing of the spectral data was done with ‘The Spectral Geologist Pro’ (TSG™) software, distributed by AusSpec International. Eleven of the 29 drillcores have been interpreted based on the short-wave infrared spectra. The raw spectra from these drillcores will be available in Data File 34, which will be released soon.

c) Core Logging

Core logging is a critical component to this study as it establishes the basic framework geology. Nineteen new multiparameter sandstone logs and five selected basement logs were completed on drillholes at the SGL and an additional 14 basement logs and nine sandstone logs were completed from drillholes in the Wheeler River and

4 The phrase “the 3-D environment” encompasses all aspects of 3-D modelling including 2.5-D, 3-D, and 4-D space: 2.5-D space is where 2-D objects are displayed in the third dimension; true 3-D space contains objects that are volumes, and 4-D space attempts to bring a temporal component to the modelling. The software used by SGS for 3-D modelling is Mira Geoscience’s ParadigmTM GOCAD® Mining Suite (GOCAD).

Saskatchewan G

eological Survey 3

Summ

ary of Investigations 2013, Volum

e 2

Figure 1 – Map of the major lithostratigraphic units of the Athabasca Group with the location of selected drillholes containing multiparameter drill logs (red and blue circles). Formation codes are, in order of ascending stratigraphic position: CB = crystalline basement, FP = Fair Point, RY = Reilly (outlier – southeast of basin), RD = Read, S = Smart, MF = Manitou Falls (members: MFb = Bird, MFr = Raibl, MFw = Warnes, MFc = Collins, MFd = Dunlop), LZ = Lazenby Lake, W = Wolverine Point, LL = Locker Lake, O = Otherside, D = Douglas, C = Carswell, S/M = undifferentiated Smart and/or Manitou Falls formations, and F-O = undivided Fair Point to Otherside formations in the Carswell Structure. Black line connecting drillholes (blue circles) represents location of cross section in Figure 2. Clearwater Domain is outlined in brown. Red line represents the Beatty River Fault. Blue lines represent selected roads. Green squares show location of selected uranium mines (past and present). The Athabasca Basin map has been placed on a total-field magnetic intensity map of the basement (from Buckle et al., 2011).

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McGowan Lake areas. Discussions regarding the basement geology in the McGowan Lake and Wheeler River areas are provided by Card (this volume). Each drillhole containing Athabasca Group sedimentary rocks was logged using a systematic multiparameter logging method that measures features used to determine lithostratigraphic units of the Athabasca Basin. A detailed discussion regarding this logging methodology can be found in Bosman and Korness (2007).

3. Lithostratigraphic Interpretations In 2013, lithostratigraphic investigations were focussed mainly in the southwest portion of the Athabasca Basin (Figure 1) for a number of reasons, including: 1) this area contains fewer multiparameter drill logs than elsewhere in the basin, 2) there are several drillcores from this area stored at SGL that are available for logging, 3) further information from this part of the basin may elucidate the stratigraphic relationship between the Read and Smart formations, and 4) this area is in the vicinity of the Patterson Lake South discovery, which has seen a significant amount of disposition staking in the past year. Several of the drillcores in this area also contain Phanerozoic rocks that unconformably overlie the Athabasca Group. Preliminary investigations on these Phanerozoic rocks show that both Cretaceous and Devonian strata are present. Drillcores containing Phanerozoic strata that were logged this summer include: HAR-01, -02, -04, and -05 and S-008 and -009. The reader is referred to the “DDH_core collection_regina_athabasca” layer in the Geological Atlas of Saskatchewan (Slimmon, 2013) for details regarding these drillholes.

The characteristics of the Read and Smart formations are briefly described below (a more detailed description can be obtained in Table 4 of Ramaekers et al. (2007)). The Read Formation is a heterogeneous succession of quartz pebble/cobble conglomerates (although polymictic material is not uncommon), red silty mudstones, and quartz arenites. The succession generally fines upwards and can have multiple fining-upward cycles. Deposition of the Read Formation took place in a braided fluvial to sheet-flood environment. Near the Clearwater Domain (Figure 1) and further west it may contain some eolian facies. The Smart Formation generally comprises a homogeneous, fine- to coarse-grained, quartz arenite with limited mudstones, sparse isolated pebbles, and minor conglomeratic horizons near the base. As with the Read Formation, the Smart Formation fines upwards and may contain multiple fining-upward cycles. The Smart Formation consists of interbedded fluvial (largely basal) and prominent eolian deposits in the upper parts. The latter are very well sorted (better than the fluvial facies), fine to medium grained and largely horizontally bedded.

EXTECH IV researchers indicated that additional work was needed to resolve several issues regarding the Read and Smart formations (Ramaekers et al., 2007). These unresolved issues included: their regional extents; whether the Read and Smart formations are lateral equivalents or stratigraphically below/above the other; and whether in areas such as the eastern edge of the study area, lithofacies similar to the Read Formation have been mapped as Smart Formation.

At the time of writing, drillhole logs are being correlated to better understand the stratigraphic relationship between the Read and Smart formations (Figure 2). Although incomplete, preliminary work in the focus area suggests: 1) the Read Formation overlies the Smart Formation west of the Beatty River fault (Figure 1); 2) the Smart Formation is absent, at least locally, between the Beatty River fault and above the Clearwater Domain; 3) fine-grained lithofacies similar to the Smart Formation, with sporadic conglomerates, are present in the basal Read Formation units east of the Beatty River fault; 4) there is a topographic high between the Beatty River fault and just east of the Clearwater Domain; and 5) lithostratigraphic units of the Manitou Falls and Read formations thin considerably westward towards drillhole HK-12 and some may even pinch out.

The Clearwater Domain is characterized by a 20 to 30 km wide, north- to north-northeast–trending, positive magnetic anomaly, which crosscuts the regional aeromagnetic fabric south of the basin (Figure 1) (Saskatchewan Geological Survey, 2003). The Clearwater Domain is poorly exposed south of the Athabasca Basin margin, but does contain highly deformed felsic gneiss, which is intruded by 1.84 Ga granites (Stern et al., 2003). Prior to deposition of the Athabasca Group, the brittle Beatty River fault had an earlier, ductile history. Based on interpretation of aeromagnetic data, this early ductile component of displacement had a dextral sense of shear (Card et al., 2007). The later brittle reactivation created uplift on the southeast side of the fault, creating a trough on the northwest side (Ramaekers et al., 2007).

Based on the stratigraphy and some structural evidence, it seems likely that the granitoid rocks within the Clearwater Domain and Beatty River fault acted as topographic highs that initially impeded westward accreting deposition of the Read and Manitou Falls formations into the Jackfish basin (Figure 2).

The Rio Grande Basin of the south-central United States and northern Mexico may be a possible modern analogue to the depositional environment in which the Smart and Read formations were deposited. This modern basin


Figure 2 – East-west cross section of multiparamater drill logs with preliminary interpretation of Athabasca Group stratigraphic relationships. Location of cross section and drillholes (blue circles) shown in Figure 1. Sub-Athabasca Basin unconformity is present at the bottom of multiparameter sandstone data except where indicated. Formations in ascending order: B = Basement, FP = Fair Point, S = Smart, RD = Read, MF = Manitou Falls (members: MFb* = Bird, MFd = Dunlop (sub-members: MFd-w = Warnes, MFd-h = Hodge, MFd-lc = Lower Clampitt, MFd-uc = Upper Clampitt)); and LZ = Lazenby Lake. Datum was selected as the base of the MFd-h because it is easily recognisable in the multiparameter sandstone logs on the west side of the Athabasca Basin. MFb* is a similar lithostratigraphic unit to MFb; however, it does not contain the required amount of conglomerate. UTMs in NAD83, zone 13.

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Shea Creek Amok Ltd.

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June 21 - July 3, 2013

Alsask South Marline Oil Corporation

Regina July 5, 2013

Eli Wiens

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Regina July 18, 2013

Jessica Poncsak

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July 5-6, 2007

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June 3-10, 2013

Scurry Lake Scurry-Rainbow Oil Limited

Regina July 5, 2013

Eli, Jessica, Graham

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Wide Lake July 3, 2008

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Regina June 14, 2012

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355 212381E 6454788N

413 239019E 6458441N

456 220260E 6435977N

560 232056E 6429523N

526 265206E 6414132N

545 286738E 6417198N

530 294397E 6402018N

570 348572E 6391084N

376804E 6373466N

482 395988E 6378647N

417347E 6394302N

Jackfish Basin

Cree Basin


Figure 3 – A) Photograph of Sangre de Cristo Mountains, Medano Creek, and the Great Sand Dunes in close proximity to each other. Medano Creek delivers fresh, coarse, detrital material from the mountains to the valley floor and reworks eolian deposits of the Great Sand Dunes; Rio Grande Rift, southern Colorado, U.S.A. (modified from St. John, 2007a). B) Photograph of small scours and isolated pebbles (red arrows) in fluvially modified eolian sand, Medano Creek, southern side of Great Sand Dunes, Rio Grande Rift, southern Colorado, U.S.A. (modified from St. John, 2007b).

contains multiple lithofacies including bedrock, eolian deposits (both U-shaped and transverse dune ridges), and fluvial deposits, all located in close proximity (Figure 3A). The eolian deposits can themselves be variable depending on proximity to the source. Distal eolian deposits generally are characterized by well sorted, well rounded, very fine to medium-grained sediment, whereas deposits proximal to mountain fronts contain angular, bimodally sorted, fine- to granule-sized material. The composition of fluvial deposits can also be variable and is directly related to their sources. Therefore, fluvial deposits coming off the mountains contain coarse, angular material, whereas sediments deposited in a more distal setting from the mountain fronts are finer grained. In the Rio Grande Rift example, in which the river system erodes the dunes, the fluvial deposits contain a mixture of bedrock detritus and reworked eolian material (Figure 3B). The dunes themselves are fluvial sediments reworked by the wind. This type of sediment facies variability undoubtedly would have characterized the depositional setting of the Athabasca Group deposits around the Clearwater Domain.

In the Athabasca Basin, the lithology of the Read Formation changes towards the west, generally becoming finer grained as the fluvial systems become more distal from the main source rocks (Trans-Hudson Orogen) in the east.

However, in the west it is difficult to distinguish the Read Formation from the Smart Formation because grain size and sorting are similar. Locally, the Read Formation exhibits textural changes. These include occasional pebble beds that suggest a more proximal source (i.e., the topographically high Clearwater Domain), which may have sporadically contributed material. Alternatively, deposition from proximal source rocks could have been relatively continuous, but the sediment supply may have been minor due to the lower topographic relief of the Clearwater Domain relative to the mountains of the Trans-Hudson Orogen. Just as the deposits of the Read and Smart formations in the vicinity of the Clearwater Domain were dominated by a distal sediment supply, the dominant sediment supply for the deposits adjacent to the Sangre de Cristo Mountains in the Rio Grande Basin largely comes from a more distal source (i.e., the San Juan Mountains; Figure 4).

Figure 5 is an annotated aerial photograph of the Great Sand Dunes in the Rio Grande Rift illustrating the deposits of the area as well as the inferred Athabasca Basin analogues. At the time of initial deposition of the Read Formation, the Clearwater Domain and perhaps the Beatty River fault created a watershed that separated the Cree basin from the Jackfish basin (Figure 2). In the Cree basin, the fluvially dominated Read Formation was deposited unconformably on the Paleoproterozoic to Archean

A

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Dunes

Bedrock


Figure 5 – Annotated photograph of a National Parks Service poster in Great Sand Dunes National Park showing the sedimentary facies in the Rio Grande Rift basin (left and centre of image). Inferred analogues in the Athabasca Basin at the time of initial Read Formation sedimentation have been labelled on right side of image. The Sangre de Cristo Mountains form a watershed which currently separates two depositional basins similar to the Cree and Jackfish sub-basins in the Athabasca Basin. Probably a much less impressive watershed than the Sangre de Cristo Mountains, the Clearwater Domain and Beatty River fault initially prevented sediment from the Cree basin in the east to be transported into the Jackfish basin in the west. Abbreviation: Fm, Formation.

Figure 4 – Photograph of annotated poster of the Rio Grande Basin showing the dominant source for the Great Sand Dunes being the more distal source terrain in the west with lesser amounts of detritus coming from the proximal source in the east (from St. John, 2007c).

crystalline basement rocks and onlapped granitoid rocks on the eastern edge of the Clearwater Domain. In the Jackfish basin, the eolian-dominated Smart Formation was deposited unconformably on earlier Athabasca Group deposits of the Fair Point Formation. Rocks of the Clearwater Domain formed a much lower ridge than the comparative modern-day Sangre de Cristo Mountains (the watershed), so continued deposition eventually covered the topographic highs, facilitating Read Formation sedimentation in the west (Figure 2). Some of the questions that remain to be answered include: 1) whether the Smart Formation may have also been deposited locally on the eastern side of the Clearwater Domain; 2) what was the height of the topographic high at the time of deposition, and 3) whether the Smart and Read formations have a more intimate stratigraphic relationship (possibly interfingering with one another).

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Figure 6 – Arial photograph of modern eolian facies (transverse dunes) near the west edge of the Athabasca Basin (see Figure 1 for approximate location). Height of individual dunes is approximately 10 m, which is similar to those in the Rio Grande Basin. The part of the dune field shown is approximately 2.5 km long, 0.8 km wide, and is centred on UTM 137606 m E, 6474757 m N (NAD83, zone 13).

Individual transverse dunes in the Rio Grande Basin are approximately 10 m tall and if they had been formed in an arid environment, preserved, lithified, and subsequently exposed, they would look like the large-scale crossbeds preserved in places such as Arches National Park in Utah, U.S.A. The Rio Grande dunes, however, are forming in a wetter environment so the transverse dune ridges have lower preservation potential, and the eolian deposits most likely preserved would be the horizontally bedded sands deposited at the base of migrating small dunes. Large-scale, eolian crossbedding is rarely present in the Athabasca Basin, but horizontally bedded and low-angle crossbedded eolian deposits were recorded in a number of formations; therefore, the deposits in the Athabasca Basin are also interpreted to be deposited in a wetter environment.

Modern-day eolian ridged dunes, similar to those in the Rio Grande Rift basin, are also developing at the edge of a delta environment on top of the Athabasca Basin near its western edge (Figures 1 and 6). The sand in these modern dunes is reworked Fair Point Formation, plus new fluvial material transported by the Athabasca River, in small part from the eroding Clearwater Domain. The prevailing winds from the west are moving the dunes into the basin towards the Clearwater Domain. This situation, including the large delta, is analogous to the west side of the Rio Grande Basin, where the Rio Grande River enters the basin and forms a big delta. The sand is then moved to the east side via U-shaped dunes and rivers, and then piled up to form the big dunes that partially climb up the eastern slopes of the Sangre de Cristo mountains (Figures 3A, 4, and 5).

4. Summary The primary goal of the Athabasca Basin ore-systems project is to present regional geoscience data, traditionally seen in two-dimensional viewing, in the 3-D environment. Once a 3-D model for the geology of the Athabasca Basin is generated, new and historic data can be displayed in 3-D to facilitate their interpretation. Through a combination of office- and field-based data collection, compilation of pre-existing information, and the use of new interpretation techniques, the geology and history of the Athabasca Basin is presented in a manner never before seen. This will provide a better understanding of the processes that led to the formation of economic uranium deposits in the Athabasca Basin and its underlying basement.

The SGS has undertaken several new tasks aimed at accomplishing this goal. We have generated, and made available to the public, new data, specifically geochemical and spectral datasets, that will allow us to better interpret the diagenetic and hydrothermal fluid history of the Athabasca Basin. The collection and preservation of drillcores (including, lithological, stratigraphic and structural), geochemical, and spectral data from critical parts of the

Athabasca Basin are helping to revise the geological framework on which all the other datasets are displayed. Specifically, determination of the stratigraphic relationship between the Smart and Read formations will help in establishing a more robust geological framework for 3-D modelling on the west side of the Athabasca Basin. Knowledge that the Clearwater Domain initially acted as a watershed separating the Read Formation from the Smart Formation will aid in mapping these units deeper into the basin. Recognizing the Clearwater Domain as a positive topographic feature during initial deposition of the Read Formation provides a modelling constraint for the sub-Athabasca unconformity in this area. This type of scenario can also be explored for in other areas of the basin.

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Athabasca River

Richardson River


5. Acknowledgements The authors are grateful to Jeanne Percival of the Geological Survey of Canada for allowing us to use her Analytical Spectral Device. The authors are also appreciative of the support from the staff at the SGL in arranging examination tables for our drillcore and sample needs. Ken Ashton and Jocelyn Fetter are thanked for their insightful discussions and comments during the reviewing process of this paper.

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The Athabasca Basin Ore-Systems Project: Project Update ... · near-infrared (NIR, 780 to 1300 nm), and short-wave infrared (SWIR, 1300 to 2500 nm) regions. Spectral resolution ranges