High Arctic Large Igneous Province Alkaline Rocks in Canada: Evidence for Multiple Mantle Components

• Published in: Journal of Petrology
• Main Authors: Bédard, Jean H, Troll, Valentin R, Deegan, Frances M, Tegner, Christian, Saumur, Benoit M, Evenchick, Carol A, Grasby, Stephen E, Dewing, Keith
• Other Authors: Geological Survey of Canada
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Arctic; Audhild Bay; Canada; Ellesmere Island; Fulmar; Greenland; Hassel; greenlandic; Ocean Island
• Online Access: http://dx.doi.org/10.1093/petrology/egab042; http://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egab042/38575853/egab042.pdf; https://academic.oup.com/petrology/article-pdf/62/9/egab042/42755472/egab042.pdf

Abstract The Cretaceous High Arctic Large Igneous Province (HALIP) in Canada, although dominated by tholeiites (135–90 Ma), contains two main groups of alkaline igneous rocks. The older alkaline rocks (∼96 Ma) scatter around major fault and basement structures. They are represented by the newly defined Fulmar Suite alkaline basalt dykes and sills, and include Hassel Formation volcanic rocks. The younger alkaline group is represented by the Wootton Intrusive Complex (92·2–92·7 Ma), and the Audhild Bay Suite (83–73 Ma), both emplaced near the northern coast of Ellesmere Island. Fulmar Suite rocks resemble EM-type ocean island basalts (OIB) and most show limited crustal contamination. The Fulmar Suite shows increases of P2O5 at near-constant Ba–K–Zr–Ti that are nearly orthogonal to predicted fractionation- or melting-related variations, which we interpret as the result of melting composite mantle sources containing a regionally widespread apatite-bearing enriched component (P1). Low-P2O5 Fulmar Suite variants overlap compositionally with enriched HALIP tholeiites, and fall on common garnet lherzolite trace element melting trajectories, suggesting variable degrees of melting of a geochemically similar source. High-P2O5 Hassel Formation basalts are unusual among Fulmar rocks, because they are strongly contaminated with depleted lower crust; and because they involve a high-P2O5–Ba–Eu mantle component (P2), similar to that seen in alkali basalt dykes from Greenland. The P2 component may have contained Ba–Eu-rich hawthorneite and/or carbonate minerals as well as apatite, and may typify parts of the Greenlandic sub-continental lithospheric mantle (SCLM). Mafic alkaline Audhild Bay Suite (ABS) rocks are volcanic and hypabyssal basanites, alkaline basalts and trachy-andesites, and resemble HIMU ocean island basalts in having high Nb, low Zr/Nb and low 87Sr/86Sri. These mafic alkaline rocks are associated with felsic alkaline lavas and syenitic intrusions, but crustally derived rhyodacites and rhyolites also exist. The ...