Geochemical Systematics of High Arctic Large Igneous Province Continental Tholeiites from Canada—Evidence for Progressive Crustal Contamination in the Plumbing System

Abstract Cretaceous High Arctic large igneous province (HALIP) sub-alkaline magmatic rocks in Canada are mostly evolved (MgO 2–7 wt%), sparsely plagioclase + clinopyroxene ± olivine-phyric tholeiitic basalts. There were two main HALIP continental flood basalt (CFB) eruption episodes: 135–120 Ma (Isachsen Fm.) and 105–90 (Strand Fiord Fm.), both associated with cogenetic doleritic sills dykes. Building on a modern database, 16 tholeiite types defined grouped into genetic series using Ce vs Sm/YbNMORB distributions. Comparison model melting curves implies that higher-Sm/Yb record low-degree of garnet-bearing mantle sources. More voluminous intermediate- low-Sm/Yb separated from the at shallower levels after further extensive spinel-peridotite field. Within given Sm/Yb range, increases incompatible elements such as coupled progressive clockwise rotation normalized trace element profiles. Trace modeling this cannot be due to closed-system fractional crystallization but requires ubiquitous incorporation component resembling crust. The fractionation models imply basalts (?7 wt% MgO) initially crystallized olivine gabbro assemblages, lower-MgO successively crystallizing ilmenite-gabbro assemblages. In contrast, fractionated more ilmenite, is still required explain developing negative Sr–Eu anomalies. Back-fractionation require about 40 % addition bring most primitive equilibrium Fo89 mantle. Inverse fractionation–assimilation shrinks CFB signature, making decontaminated parental melts similar enriched mid-ocean ridge basalt. increase contamination signature within each differentiation not consistent involving derivation source previously by subduction. Strong interaction Sverdrup Basin sedimentary may cause localized over-enrichment K–Rb–Th–U, strong Ba enrichment absence concomitant K–Rb–Th–U enrichment. could reflect either Ba-rich lithospheric strongly manifested coeval alkaline suites, or syn- post-emplacement fluid-mediated transfer host rocks.