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 Ma (Strand Fiord Fm.); both associated with cogenetic doleritic sills and dykes. Building on a large modern database, 16 HALIP tholeiite Types are defined and grouped into genetic Series using Ce <vsi> Sm/YbNMORB distributions. Comparison with model melting curves imply higher-Sm/Yb HALIP basalt Types record low degree melting of garnet-bearing mantle sources. More voluminous intermediate- and low-Sm/Yb HALIP basalt Types separated from the mantle at shallower levels after further extensive melting in the spinel-peridotite field. Within a given Sm/Yb range, increases in incompatible elements like Ce are coupled with progressive clockwise rotation of normalized incompatible trace element profiles. Trace element modeling implies this cannot be due to closed system fractional crystallization but requires progressive and ubiquitous incorporation of a component resembling continental crust. The fractionation models imply low-Sm/Yb HALIP basalts (∼7 wt% MgO) initially crystallized olivine gabbro assemblages, with lower-MgO basalts successively crystallizing gabbro and ilmenite-gabbro assemblages. In contrast, higher-Sm/Yb basalts fractionated more clinopyroxene and ilmenite, but extensive plagioclase fractionation is still required to explain developing negative Sr-Eu anomalies. Backfractionation models require about 40% addition of olivine to bring the most primitive HALIP basalts (∼7% MgO) into equilibrium with Fo<su89b> mantle. Inverse fractionation-assimilation modeling shrinks the CFB signature, making decontaminated model parental melts more similar to E-MORB. The progressive increase of the contamination signature within each HALIP tholeiitic differentiation series is not consistent with models involving derivation of HALIP basalts from a mantle source previously enriched by subduction. Strong interaction of basalt with Sverdrup Basin sedimentary rocks may cause localized over-enrichment in K-Rb-Th-U, but cannot explain strong Ba-enrichment in the absence of concomitant K-Rb-Th-U-enrichment. The localized Ba enrichment could reflect either a Ba-rich lithospheric mantle component that is strongly manifested in the coeval HALIP alkaline suites, or syn- to post-emplacement fluid-mediated transfer from Ba-rich host rocks.