Petrology and lithogeochemistry of Paleozoic alkalic magmatism in the Selwyn Basin, Yukon, Canada

Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil...

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Bibliographic Details
Published in:Canadian Journal of Earth Sciences
Main Authors: Scanlan, Emma J., Leybourne, Matthew I., Layton-Matthews, Daniel, Van Wagoner, Nancy, Paradis, Suzanne, Piercey, Steve, Crowley, James L.
Other Authors: Natural Resources Canada, Society of Economic Geologists Foundation, Arthur B. McDonald Canadian Astroparticle Physics Research Institute
Format: Article in Journal/Newspaper
Language:English
Published: Canadian Science Publishing 2024
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Online Access:http://dx.doi.org/10.1139/cjes-2023-0081
https://cdnsciencepub.com/doi/full-xml/10.1139/cjes-2023-0081
https://cdnsciencepub.com/doi/pdf/10.1139/cjes-2023-0081
Description
Summary:Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil District, Keno Hill, and the Misty Creek Embayment). Volcanic rocks from the Anvil District and the Misty Creek Embayment are dominated by alkalic basalts with light rare earth element (LREE)-enriched geochemical signatures, whereas metavolcanic and dike samples from Keno Hill comprise subalkaline basalts with enriched mid-ocean ridge basalt (E-MORB) signatures. The Early Ordovician Menzie Creek volcanic rocks of the Anvil District display trace element geochemical signatures intermediate between ocean island basalt (OIB) and E-MORB, whereas the Middle–Late Ordovician volcanic rocks from the Misty Creek Embayment have OIB signatures. Differences in the trace element geochemistry of the sample suites are attributed to the degree of partial melting. The Menzie Creek volcanic rocks formed from large volume melts of enriched mantle that diluted incompatible element signatures in the Early Ordovician. Late Ordovician magmatism produced the Misty Creek Embayment samples, where restricted melt volumes of an enriched mantle source resulted in the most enriched samples geochemically. The Keno Hill samples represent the shallowest melting of the analysed samples and may have resulted from melting of heterogenous subcontinental lithospheric mantle. Magmatic zircons from a Keno Hill metavolcanic sample analysed by chemical abrasion thermal ionization mass spectrometry resulted in a primary deposition age of c. 296 ± 0.36 Ma (Early Permian), during a period with little magmatism in the Selwyn Basin and representing a previously unknown unit in the area.