| Title | Origin of enigmatic beds in Proterozoic sandstone, Athabasca Basin, Saskatchewan, Canada |
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| Author | Percival, J B ;
Bosman, S A; Venance, K E; Hunt, P A; Ramaekers, P; Jefferson, C W |
| Source | Micro et Nano Scientiæ Mare Magnum, XIV International Clay Conference, Book of abstracts, volume 1, Oral sessions; by Associazione Italiana per lo Studio delle Argille; 2009 p. 192 |
| Year | 2009 |
| Alt Series | Earth Sciences Sector, Contribution Series 20080583 |
| Meeting | XIV International Clay Conference; Castellaneta Marina; IT; June 14-20, 2009 |
| Document | book |
| Lang. | English |
| Media | paper |
| Province | Saskatchewan |
| NTS | 64E; 64L; 64M; 74E; 74F; 74G; 74H; 74I; 74J; 74K; 74L; 74M; 74N; 74O; 74P |
| Area | northern Saskatchewan |
| Lat/Long WENS | -112.0000 -102.0000 60.0000 57.0000 |
| Subjects | igneous and metamorphic petrology; sedimentology; sandstones; tuffs; clays; breccias; drillholes; quartzarenites; uranium deposits; Athabasca Group; Athabasca Basin; Manitou Falls Formation;
Proterozoic |
| Program | Secure Canadian Energy Supply |
| Released | 2009 01 01 |
| Abstract | The Athabasca Group in northern Saskatchewan and Alberta fills a 100,000 km2, 1400 m+ thick basin with four sequences of fluvial conglomeratic sandstone with minor shale and carbonate. In 2000-2004 the
basin was the focus of a multi-disciplinary, multi-agency study (EXTECH IV) to improve the framework geology and exploration technologies for unconformity-associated uranium deposits. The Saskatchewan Ministry of Energy and Resources has continued
to revise, redefine and reposition the lithostratigraphic units of the Athabasca Group in building a 3-D basin model. During field activities in 2007 an unusual bed was observed in a drill core near the top of the Manitou Falls Formation of the
Athabasca Group. The medium to dark grey, thinly laminated, friable and clay-rich bed with gradational upper and lower contacts is in strong contrast to the underlying and overlying layers of very fine- to medium-grained competent sandstone and
interbedded siltstone. Preliminary petrographic analysis shows poorly sorted, angular quartz grains with minor to trace mica, zircon fragments, K-feldspar, amphibole, tourmaline, rutile, magnetite, alumino-phosphate minerals and irregularly-shaped
clay-rich, soft-sediment deformed intraclasts set in a fine-grained matrix. The intraclasts enclose angular grains of quartz. The angularity of the quartz grains and the variable grain size suggest a possible explosive (volcanic or impact?) origin.
Thus, this unit may represent a new tuffaceous layer in the Manitou Falls Formation, or an intraformational breccia of unknown origin. Alternatively, or in addition, it may have been hydraulically fractured during far-field tectonism. During the
2008 field season, several beds in another drillhole located about 40 km away, were observed to show similar field characteristics to the 2007 sample. These samples also appear to be stratigraphically correlative despite their distal location. Both
the 2007 and 2008 layers are marked by strong gamma-ray peaks (suspected thorium).
Typically the Upper Manitou Falls Formation (MFd) is a well-rounded medium- to fine-grained quartz arenite with about 1-3% dickite matrix with abundant clay
intraclasts dominated by dickite. The 2007 sample contains illite (+ minor kaolinite/dickite) as the matrix clay with deformed siltstone and mudstone intraclasts. However, this layer does not contain the classic devritified glass shards that typify
tuffaceous sediments. On the other hand, the felted mass of the matrix clay, the presence of primary minerals such as amphibole (hastingsite composition) and K-feldspar (orthoclase), magnetite and an illitic signature (based on SWIR and SEM analysis)
in the matrix provide evidence for an unusual origin. In contrast, the 2008 samples contain rounded quartz grains, pyrite and have a matrix dominated by kaolinite and dickite, closer to the typical MFd composition. This research focuses on
determining the origin of these enigmatic interbeds. |
| GEOSCAN ID | 226266 |
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