THE HIGH ARCTIC LIP IN CANADA: STRATIGRAPHIC CONTROLS AND GEOCHEMICAL MONITORING ON CRUSTAL INFLUENCES

The Cretaceous geology of Canada’s Arctic islands and formally adjacent regions of Norway and Russia are influenced by widespread mafic magmatism manifesting as a giant radiating dyke swarm, sills, and laterally extensive basalt flows including flood basalts. Together, these and submarine equivalents of the Alpha-Mendeleev Ridge, constitute the High Arctic Large Igneous Province (HALIP). HALIP in Canada is dominated in part by three pulses of tholeiitic magmatism: two occurring at 120-130 Ma that fed basaltic lavas associated with the siliciclastic Isachsen Formation (Paterson and younger Walker Island Members) and a third pulse at ca. 95 – 100 Ma that fed lavas of the Strand Fiord Formation flood basalts and also fed South Fiord intrusions. Alkaline rocks, sometimes treated as part of HALIP, were emplaced beginning 92Ma.

We geochemically compare Isachsen and Strand Fiord (represented by the South Fiord intrusions) magmatic pulses. On AFM and Nb/Y vs. Zr/Ti systematics, Isachsen Formation lavas and South Fiord intrusions (chemically linked to the Strand Fiord Formation lavas) are subalkaline, tholeiitic basalts. Th/La for South Fiord intrusions and some Isachsen Formation lavas range from 0.13 – 0.23 with minimal change in Ba/Th (~40). In contrast, there is a cluster of Isachsen Formation lavas that have high Ba/Th ratios (up to 200). In Ba/Nb vs. εNd_t space, Isachsen Formation basalts display wide Ba/Nb ratios (~15 – 50) whereas the same ratios for South Fiord intrusions tightly cluster between 15-20. South Fiord intrusions have εNd_t values of+1 to +4.5 whereas εNd_t for the Isachsen Formation flows are +2 to +6. Chemical modeling in Ba/Nb vs. εNd_t shows crustal signatures for the intrusions of South Fiord that are linked with Strand Fiord Formation lavas that commonly do not have interbeds of sedimentary rocks between flows. However, the Isachsen Formation Lavas that do have sedimentary interbeds of 10s of m in thickness are less influenced by crustal signatures. We suggest contamination of the Strand Fiord Formation lavas due to interaction with sedimentary rocks of the Sverdrup Basin might be facilitated by higher recurrence intervals that serves to maintain a thermal anomaly between eruptive episodes or that the lavas of the Strand Fiord Formation may have erupted at higher temperatures or a combination thereof.