Age and Geochemistry of High Arctic Large Igneous Province Tholeiitic Magmatism in NW Axel Heiberg Island, Canada

• Published in: Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2023-11, Vol.24 (11), p.n/a
• Main Authors: Deegan, F. M., Pease, V., Nobre Silva, I. G., Bédard, J. H., Morris, G.
• Format: Article
• Language: English
• Subjects: Basalt; Carboniferous; Cretaceous; crustal assimilation; Dikes; Earth crust; Embankments; Environmental impact; Fjords; Floods; Gases; Geochemistry; Greenhouse effect; Greenhouse gases; HALIP; Islands; Isotopes; large igneous province; Lava; Magma; mantle; Ocean circulation; Paleogene; Plagioclase; Sedimentary rocks; Sills; Strontium isotopes; Trace elements; Upwelling
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2023GC011083

The Cretaceous High Arctic Large Igneous Province (HALIP) in Canada involved extrusion of continental flood basalts (CFBs) at 130–120 Ma and 100‐95 Ma and emplacement of an extensive sill and dike network that intersected the Carboniferous to Paleogene Sverdrup Basin. In this paper, we present new 40Ar/39Ar ages, major and trace elements, and Sr‐Nd‐Pb isotope ratios for HALIP lava, dikes, and sills from Bukken Fiord, NW Axel Heiberg Island, Canadian Arctic Islands. Our best constrained 40Ar/39Ar ages yield a weighted average of 124.1 ± 1 (2σ) Ma, coincident with the first pulse of tholeiitic CFB magmatism in the Arctic‐wide HALIP as exemplified by Isachsen Formation flood basalts on Axel Heiberg Island. The Bukken Fiord samples are plagioclase and clinopyroxene‐phyric tholeiitic basalts, are relatively evolved (3.2–6.5 wt% MgO), and share similar major and trace element compositions to typical HALIP tholeiites. Initial 143Nd/144Nd ranges from 0.51260 to 0.51291 and initial 87Sr/86Sr ranges from 0.70362 to 0.70776, while measured 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb range from 18.614 to 19.199, 15.534 to 15.630, and 38.404 to 39.054, respectively. The most primitive sample in this study has Sr‐Nd‐Pb isotope signatures that suggest an enriched plume‐derived mantle source for HALIP tholeiites. Most samples, however, possess relatively radiogenic isotope signatures that can be explained by moderate degrees of assimilation of Sverdrup Basin sedimentary rocks. Magma‐crust interaction in the HALIP plumbing system was likely widespread and may have increased the environmental impact of the HALIP, particularly if crustal carbon was volatilized. Plain Language Summary Throughout the Earth's history, there were episodes when extremely large amounts of magma were generated deep in the Earth. As this magma worked its way to the surface, much of it stalled and solidified in the Earth's crust and some erupted. These vast magmatic regions are known as Large Igneous Provinces (LIPs) and one of the most remote of these is the High Arctic LIP (HALIP). We dated a suite of magmatic rocks from a locality at Bukken Fiord in the Canadian Arctic Islands and analyzed them for their elemental make‐up to unravel their history. We found that Bukken Fiord magmas formed around 124 million years ago from an upwelling thermal anomaly deep in the Earth and that they later interacted with crustal rocks that existed before the magma was formed. These crustal rocks contained volatile ele