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TitleVolcanology and geochemistry of HALIP flood basalts, Axel Heiberg Island, Nunavut
AuthorWilliamson, M C; Saumur, B M; Evenchick, C A; Little, K J; Cousens, B L
Source 2017.
Alt SeriesNatural Resources Canada, Contribution Series 20170002
MeetingGeological Association of Canada-Mineralogical Association of Canada, Annual Meeting,14-18 May, 2017, Kingston, Ontario, Canada; Kingston; CA; May 14-18, 2017
Mediapaper; on-line; digital
RelatedThis publication is related to Williamson, M -C; Jackson, S E; Yang, Z; Venance, K; Hunt, P; (2018). Magma recharge and mixing processes in continental flood basalt reservoirs: evidence from melt inclusions in basalts from the High Arctic Large Igneous Province, Axel Heiberg Island, Nunavut, Geological Survey of Canada, Open File 8377
File formatpdf
NTS560B; 69H
AreaAxel Heiberg Island; Bunde Fiord; Strand Fiord; Plateau Lake
Subjectsgeneral geology; geochemistry; basalts; volcanism; lava flows; Sverdrup Basin; HALIP flood basalts
ProgramWestern Arctic, High Arctic LIP, GEM2: Geo-mapping for Energy and Minerals
LinksOnline - En ligne
AbstractGeochemical studies of continental flood basalts are often hindered by a lack of stratigraphic control in areas where sheet flows were emplaced over geologically short time intervals. The advantage of studying flood basalts in a basin setting is that the time-sequence of eruptions is well-defined, thus providing a robust stratigraphic framework for lithogeochemical studies.

Fieldwork in the Sverdrup Basin was carried out in 2015 and 2016 as part of the GEM 2-High Arctic Large Igneous Province (HALIP) research activity. A particular emphasis was placed on the stratigraphy, physical volcanology and geochemistry of flood basalts in the Strand Fiord Formation. Detailed investigations were carried out at two locations on western Axel Heiberg Island: along the south shore of Bunde Fiord, and near Plateau Lake, to the north of Strand Fiord.

Previous studies demonstrated that the ~ 95 Ma Strand Fiord Formation consists of sheet flows of uniformly basaltic composition displaying aa and pahoehoe textures. Fieldwork near Plateau Lake suggests a total thickness of 980 m at this locality. The 3-D exposure of ~500 m of section alongside a retreating glacier makes this an excellent opportunity to study the evolution of a flood basalt province. Invasive flows near the base of the succession consist of a chaotic mélange of basaltic lava and blocks of sandstone. These flows are overlain by a bed of shale containing volcanic bombs and discontinuous lenses of fine-grained sandstone that locally contain fiamme. Thick lava flows are characterized by grey, unoxidized flow tops and show structures such as basalt colonnades and entablatures. In contrast, volcanic successions near Bunde Fiord consist of lava flows separated by well-defined oxidized flow tops. A single bed of crystal tuff occurs near the base of the succession. The flows are uniformly of aa type, and lack the complex intraflow structures observed at Plateau Lake and in the type area at Strand Fiord.

Flood basalts in the Strand Fiord Formation should form a coherent petrogenetic series if individual sections were once part of a single basaltic plateau. A comparative geochemical study of lava flows in both areas suggests that most eruptions tapped steady-state magmas rising from a shallow reservoir. At Bunde Fiord, the mineralogy and geochemistry of lava flows show compelling evidence for episodic magma recharge and mixing processes consistent with periods of quiescence between eruptions. We propose a model for the emplacement of HALIP flood basalts that integrates field observations with the results of petrochemical studies.
Summary(Plain Language Summary, not published)
This publication describes the results of bedrock mapping and sampling activities carried out in 2015 under the GEM 2 HALIP Activity. The authors present the first detailed study of the eruptive style in Strand Fiord Formation exposed near Plateau Lake, western Axel Heiberg Island. Results also include major and trace element data for basaltic lava flows sampled within the ~ 1 km thick volcanic succession. The authors interpret the compositional trends in flood basalts of the Strand Fiord Formation in the context of other HALIP project results. The study carries important implications for the economic potential of the HALIP magmatic system in this region of Nunavut.