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TitleTill provenance across the terminus of the Dubawnt Lake Ice Stream, central Nunavut
AuthorMcMartin, I
SourceGAC-MAC 2017; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 40, 2017 p. 259
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20160449
PublisherGeological Association of Canada
MeetingGeological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2017; Kingston, ON; CA; May 14-18, 2017
Mediapaper; on-line; digital
File formatpdf
AreaDubawnt Lake Ice Stream
Subjectsglacial deposits; sediment transport; ice flow; geochemical surveys; tills; till samples; mineral deposits; mineral exploration; Thelon Formation
ProgramGEM2: Geo-mapping for Energy and Minerals, Rae Province, Chantrey-Thelon
AbstractThe composition of glacial sediments across the distal portion of the Dubawnt Lake Ice Stream (DLIS), central mainland Nunavut, was examined to assess the potential influence of fast ice flow on sediment transport. Major changes in clast content, texture and geochemical composition are observed in till collected throughout and beyond the ice stream footprint. The most significant changes coincide with an ice front position at the southern segment of the MacAlpine Moraine System which also marks the terminus of the ice stream. The till composition over the DLIS reflects a distal provenance, rich in Dubawnt Thelon Formation sandstone debris, relatively clay-rich, SiO2-rich, and depleted in most trace and major elements. Although the SiO2 content in the matrix (<0.063 mm) gives an indication of long glacial transport of exotic quartz sandstone from the Thelon Basin (up to ~80 km), it does not singularly reflect the Thelon component in the till because of the abundance of quartz-rich rocks in the local crystalline basement of the Thelon tectonic zone (TTZ). Instead, the till matrix clay content, related to the extent of erosion of poorly-indurated and clay-cemented Thelon Formation quartz-rich sandstone and/or sub-Thelon weathered regolith, and the ratio of total versus partial Sr concentrations in till, are better discriminators of basement versus Thelon Basin-sourced debris in the region. Total/partial Sr ratios below ~10 characterize till composition within the DLIS. Beyond the ice stream, till composition reflects more local sediment provenance, derived from the underlying basement rocks, and Sr ratios increase up to 24. Atypical clay contents in till, related to changes in till facies or stratigraphy, rather than changes in provenance, can have a significant influence on till composition and may complicate the interpretation of till geochemistry. This work has important implications for mineral exploration in the Rae geological Province of the Canadian Shield and areas affected by ice streams.
Summary(Plain Language Summary, not published)
This publication provides a discussion on the composition of glacial sediments across former glacial landscapes in central mainland Nunavut and examines the influence of fast ice flow on sediment transport and provenance. The work was completed as part of the surficial geology component of the GEM-2 Rae Project Thelon-Chantrey Activity and has implications for mineral exploration methods in the Rae geological Province of the Canadian Shield.