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

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Deegan, Frances, Pease, V., Nobre Silva, I. G., Bedard, J. H., Morris, G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Naturresurser och hÃ¥llbar utveckling 2023
• Subjects: HALIP; large igneous province; geochemistry; isotopes; mantle; crustal assimilation; Geology; Geologi; Arctic; Axel Heiberg Island; sverdrup basin
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-516898; https://doi.org/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.