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TitleA 2169 Ma U-Pb baddeleyite age for the Otish Gabbro, Quebec: implications for correlation of Proterozoic magmatic events and sedimentary sequences in the eastern Superior Province
AuthorHamilton, M A; Buchan, K L
SourceCanadian Journal of Earth Sciences vol. 53, no. 2, 2016 p. 119-128, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20140350
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
NTS22L/09; 22L/10; 22L/11; 22L/12; 22L/13; 22L/14; 22L/15; 22L/16; 22M; 23D/01; 23D/02; 23D/03; 23D/04; 23D/05; 23D/06; 23D/07; 23D/08; 32I/09; 32I/10; 32I/15; 32I/16; 32P/01; 32P/02; 32P/07; 32P/08; 32P/09; 32P/10; 32P/15; 32P/16; 33A/01; 33A/02; 33A/07; 33A/08
AreaSuperior Province
Lat/Long WENS -73.0000 -70.0000 52.5000 51.5000
Subjectsgeophysics; sedimentology; geochronology; mineralogy; gabbros; sills; sedimentary rocks; basins; potassium argon dates; potassium argon dating; lead uranium ratios; uranium lead dates; uranium lead dating; dykes; uranium deposits; mineralization, secondary; paleomagnetism; magnetization
Illustrationslocation maps; geological sketch maps; tables; geological time charts
ProgramTargeted Geoscience Initiative (TGI-4) Uranium Ore Systems
Released2015 12 01
AbstractOtish Gabbro sills intrude sedimentary rocks in the Otish Basin of the southeastern Superior Province. Here, deposition of Otish Supergroup sediments had previously been thought to be older than K-Ar and Sm-Nd ages of ca. 1750-1710 Ma for Otish Gabbro sills, and younger than ca. 2515-2500 Ma U-Pb ages of underlying Mistassini dykes. However, a much older U-Pb baddeleyite age of 2169.0 ± 1.4 Ma is presented here for an Otish sill, indicating that they are coeval with, and likely genetically related to, the giant 2172-2167 Ma Biscotasing dyke swarm to the southwest and (or) the Cramolet sills and Payne River dykes to the north. The new date also indicates that the age of the Otish Supergroup falls between ca. 2515 Ma and ca. 2169 Ma, only a little different from the ca. 2450-2217 Ma bracket for the Huronian Supergroup of the Southern Province, and is consistent with both supergroups spanning the oxy-atmo inversion. The Otish Supergroup could also be coeval with the Sakami Formation to the north, but is likely older than the Richmond Gulf Group on the east coast of Hudson Bay. Early paleomagnetic study of Otish sills yielded a remanence \'0220° from that expected for Biscotasing-aged intrusions. This may indicate that too few distinct sills were studied to average out paleosecular variation, that demagnetization techniques failed to fully remove unstable magnetization components, or that the remanence is a stable secondary overprint, perhaps acquired during a fluid event related to uranium mineralization at ca. 1720 Ma.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This study focuses on clarifying the age relationship between sedimentary sequences in central Canada, especially those that host uranium mineralization, such as the Otish basin of Quebec and Huronian basin of Ontario. Previously, it was thought that the Otish and Huronian basins were of distinctly different ages, but this study demonstrates that the Otish basin sedimentary rocks must be older than 2.17 billion years, much older than previously estimated, and that the Otish and Huronian basins may be roughly equivalent in age.

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