| Title | New constraints on the age, geochemistry, and environmental impact of High Arctic Large Igneous Province magmatism: tracing the extension of the Alpha Ridge onto Ellesmere Island, Canada |
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| Author | Naber, T V; Grasby, S E ; Cuthbertson, J P; Rayner, N; Tegner, C |
| Source | Geological Society of America Bulletin 2020 p. 1-17, https://doi.org/10.1130/B35792.1  Open Access |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200346 |
| Publisher | Geological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; xlsx (Microsoft® Excel®) |
| Province | Nunavut |
| NTS | 340F/07; 340F/08; 340F/09; 340F/10 |
| Area | Hansen Point; Ellesmere Island; Canadian Arctic Archipelago; Petersen Bay; Arctic Ocean |
| Lat/Long WENS | -83.0000 -81.0000 82.6667 82.3333 |
| Subjects | geochronology; geochemistry; mineralogy; tectonics; Nature and Environment; Science and Technology; continental margins; tectonic history; magmatism; emplacement; crystallization; bulk samples;
geochemical analyses; trace element geochemistry; major element geochemistry; mineralogical analyses; petrography; radiometric dating; uranium lead dating; geophysical interpretations; magnetic interpretations; magnetic anomalies; bedrock geology;
lithology; igneous rocks; tholeiites; dolerites; volcanic rocks; basalts; rhyolites; andesites; dacites; intrusive rocks; syenites; intrusions; dykes; correlations; nomenclature; type sections; High Arctic Large Igneous Province (HALIP); Alpha Ridge;
Strand Fiord Formation; Audhild Bay Alkaline Suite; Hansen Point Tholeiitic Suite; Hansen Point Volcanic Complex; Ocean Anoxic Event 2; Pearya Terrain; Franklin Basin; Sverdrup Basin; Phanerozoic; Mesozoic; Cretaceous |
| Illustrations | location maps; geoscientific sketch maps; stratigraphic cross-sections; stratigraphic columns; stratigraphic correlations; photographs; plots; tables; photomicrographs; Concordia diagrams |
| Program | GEM2: Geo-mapping for Energy and Minerals Western Arctic, Pearya Terrane, North Ellesmere |
| Released | 2020 12 16 |
| Abstract | The High Arctic Large Igneous Province (HALIP) represents extensive Cretaceous magmatism throughout the circum-Arctic borderlands and within the Arctic Ocean (e.g., the Alpha-Mendeleev Ridge). Recent
aeromagnetic data shows anomalies that extend from the Alpha Ridge onto the northern coast of Ellesmere Island, Nunavut, Canada. To test this linkage we present new bulk rock major and trace element geochemistry, and mineral compositions for
clinopyroxene, plagioclase, and olivine of basaltic dykes and sheets and rhyolitic lavas for the stratotype section at Hansen Point, which coincides geographically with the magnetic anomaly at northern Ellesmere Island. New U-Pb chronology is also
presented.
The basaltic and basaltic-andesite dykes and sheets at Hansen Point are all evolved with 5.5-2.5 wt% MgO, 48.3-57.0 wt% SiO2, and have light rare-earth element enriched patterns. They classify as tholeiites and in Th/Yb vs. Nb/Yb space
they define a trend extending from the mantle array toward upper continental crust. This trend, also including a rhyolite lava, can be modeled successfully by assimilation and fractional crystallization. The U-Pb data for a dacite sample, that is cut
by basaltic dykes at Hansen Point, yields a crystallization age of 95.5 ± 1.0 Ma, and also shows crustal inheritance. The chronology and the geochemistry of the Hansen Point samples are correlative with the basaltic lavas, sills, and dykes of the
Strand Fiord Formation on Axel Heiberg Island, Nunavut, Canada. In contrast, a new U-Pb age for an alkaline syenite at Audhild Bay is significantly younger at 79.5 ± 0.5 Ma, and correlative to alkaline basalts and rhyolites from other locations of
northern Ellesmere Island (Audhild Bay, Philips Inlet, and Yelverton Bay West; 83-73 Ma). We propose these volcanic occurrences be referred to collectively as the Audhild Bay alkaline suite (ABAS). In this revised nomenclature, the rocks of Hansen
Point stratotype and other tholeiitic rocks are ascribed to the Hansen Point tholeiitic suite (HPTS) that was emplaced at 97-93 Ma. We suggest this subdivision into suites replace the collective term Hansen Point volcanic complex.
The few dredge
samples of alkali basalt available from the top of the Alpha Ridge are akin to ABAS in terms of geochemistry. Our revised dates also suggest that the HPTS and Strand Fiord Formation volcanic rocks may be the hypothesized subaerial large igneous
province eruption that drove the Cretaceous Ocean Anoxic Event 2. |
| Summary | (Plain Language Summary, not published)
The paper presents new data and interpretations on the geochemistry and age of Cretaceous volcanic rocks exposed on Hansen Point, Ellesmere Island,
Nunavut, in Canada's High Arctic. The geochemistry and age of these volcanic rocks are compared with other parts of the High Arctic Large Igneous Province including the Alpha Ridge. This information contributes to research needed to define
territorial boundaries into international waters. |
| GEOSCAN ID | 327034 |
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