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TitleSeismic imaging of Alpha Ridge and the magmatic overprinting of the adjacent Lomonosov Ridge and Marvin Spur
AuthorFunck, T; Shimeld, J
SourceOnline Program for the 2019 Chapman Conference on Large-scale Volcanism in the Arctic: The Role of the Mantle and Tectonics; 2019 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20190264
PublisherAmerican Geophysical Union
MeetingChapman Conference on Large-scale Volcanism in the Arctic: The Role of the Mantle and Tectonics; Selfoss; IS; October 13-18, 2019
DocumentWeb site
Mediaon-line; digital
File formathtml; pdf
ProvinceNunavut; Northern offshore region
AreaArctic Ocean
Subjectstectonics; marine geology; geophysics; Science and Technology; Nature and Environment; geophysical surveys; seismic surveys, marine; tectonic history; magmatism; intrusions; models; Alpha Ridge; Lomonosov Ridge; Marvin Spur; Fedotov Seamount; Mendeleev Rise; High Arctic Large Igneous Province (HALIP)
ProgramDelineating Canada's Continental Shelf Under UNCLOS
Released2019 10 01
AbstractIn 2016, coincident seismic reflection and refraction data were acquired over the northern flank of Alpha Ridge and the adjacent areas of Lomonosov Ridge. The experiment was part of the Canada-Sweden Polar Expedition which employed the Canadian icebreaker Louis S. St-Laurent and the Swedish icebreaker Oden. Wide-angle reflections and refractions were recorded using sonobuoys and on-ice seismometer stations. A 100-m-long hydrophone streamer was utilized to record the coincident seismic reflection data. The source array consisted of up to four G-guns with a maximum volume of 2000 in3. Results will be presented from two transects across the Lomonosov Ridge, one of which continues onto the Alpha Ridge, and a third transect along the Marvin Spur. Velocity models for the crust were developed by forward modelling of travel times, supplemented by gravity modelling to provide better control on deeper structures, in particular the Moho depth. In addition, the coincident seismic reflection data were used to extract information on the geometry of layer boundaries in the upper part of the models.
The models for the northern flank of Alpha Ridge show up to 2 km of sediments overlying a three-layer crust consisting of: a 2-km-thick top layer with velocities between 4.4 and 4.8 km/s; a 3-km-thick layer of 5.6 km/s; and, a lower crustal layer of 6.8 km/s. The Moho depth is determined by gravity modelling and lies around 17 km but deepens to 22 km beneath the Fedotov Seamount. The velocity structure is similar to other models from the Alpha Ridge and Mendeleev Rise, indicating that the High-Arctic Large Igneous Province (HALIP) volcanism has created a highly homogeneous crust. The crust on Marvin Spur at the Amerasian flank of Lomonosov Ridge differs from igneous crust on Alpha Ridge. Lower crustal velocities are 6.3 km/s and are consistent with interpretations that the spur is a continental sliver. However, like Alpha Ridge, the Marvin Spur is overlain by volcanics, and a high-amplitude wide-angle reflection multiple is modelled as a 6-km-thick high-velocity lower crust, indicating significant HALIP-related magmatic overprinting of the spur. This overprint extends to the southern flank of Lomonosov Ridge where there is a volcanic edifice and also a 60-km-wide zone of elevated lower crustal velocities interpreted as magmatic intrusion.
Summary(Plain Language Summary, not published)
As part of the 2016 Canada-Sweden Polar Expedition, seismic reflection and refraction data were collected over the northern flank of the Alpha and Lomonosov ridges, which are amongst the most prominent features of the Arctic Ocean basin. The new data provide valuable information on the acoustic velocity and, ultimately, the geological nature of the rocks comprising the ridges. This contributes enormously to understanding how the ridges formed and their relationships to the creation of the Arctic Ocean basin.

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