Geophysical analysis of the Alpha-Mendeleev ridge complex: Characterization of the High Arctic Large Igneous Province

详细信息    查看全文

• 作者：G.N. Oakey^a ; ^{Gordon.Oakey@Canada.ca" class="auth_mail" title="E-mail the corresponding author} ; R.W. Saltus^b ; ¹
• 关键词：Alpha Ridge ; Mendeleev Ridge ; High Arctic Large Igneous Province ; Magnetic domain
• 刊名：Tectonophysics
• 出版年：2016
• 出版时间：22 November 2016
• 年：2016
• 卷：691
• 期：part_PA
• 页码：65-84
• 全文大小：7372 K

文摘

The Alpha–Mendeleev ridge complex is a first-order physiographic and geological feature of the Arctic Amerasia Basin. High amplitude “chaotic” magnetic anomalies (the High Arctic Magnetic High Domain or HAMH) are associated with the complex and extend beyond the bathymetric high beneath the sediment cover of the adjacent Canada and Makarov–Podvodnikov basins. Residual marine Bouguer gravity anomalies over the ridge complex have low amplitudes implying that the structure has minimal lateral density variability. A closed pseudogravity (magnetic potential) contour around the ridge complex quantifies the aerial extent of the HAMH at ~ 1.3 × 10⁶ km².

We present 2D gravity/magnetic models for transects across the Alpha Ridge portion of the complex constrained with recently acquired seismic reflection and refraction data. The crustal structure is modeled with a simple three-layer geometry. Large induced and remanent magnetization components were required to fit the observed magnetic anomalies. Density values for the models were based on available seismic refraction P-wave velocities. The 3000 kg/m³ lower crustal layer is interpreted as a composite of the original crustal protolith and deep (ultramafic) plutonic intrusions related to a plume sourced (High Arctic) LIP. The 2900 kg/m³ mid-crustal and 2600 kg/m³ upper-crustal layers are interpreted as the combined effect of sills, dikes, and flows. Volumetric estimates of the volcanic composition include (at least) 6 × 10⁶ km³ for the mid- and upper-crust and between 13 × 10⁶ and 17 × 10⁶ km³ within the lower crust — for a total of ~ 20 × 10⁶ km³.

We compare the magnetic structure, pseudogravity, and volumetric estimates for the HAMH portion of the HALIP with global large igneous province analogs and discuss implications for Arctic tectonics. Our results show that the closest analog to the HAMH/HALIP is the Kerguelen Plateau, which is considered a continental plateau intensively modified by plume-related volcanism.