Geochemistry and tectonic setting of the Yelverton Formation, Ellesmere Island, Canada: A record of Ediacaran-Cambrian extension along the northern margin of Laurentia

Neoproterozoic to early Paleozoic strata exposed along the northeastern margin of North America consists of thick sedimentary and volcanic succession, recording a prolonged history of rifting and development of passive margin. The exact onset of passive margin sedimentation is still debated and constrained to either Neoproterozoic or early Cambrian times, with uncertain links to ca. 720 Ma Franklinian LIP magmatism and basin development in Siberia. The history of extension along the margin is potentially recorded in volcanic and sedimentary rocks belonging to Yelverton Formation exposed on northern Ellesmere Island, Canada. However, age and tectonic setting of this formation are poorly understood and constrained to Neoproterozoic or early Cambrian, interpreted as an island arc or rift-related succession. Here, we present new stable and radiogenic isotope geochemistry from carbonate rocks underlying the volcanics, as well as major and trace element geochemistry from intrusive and extrusive mafic rocks to elucidate the origin of the Yelverton Formation. The δ¹³C_carb values obtained from the carbonates vary between measured sections from ca. -1‰ to +8‰ with an average ⁸⁷Sr/⁸⁶Sr value of 0.7076 (n = 6), suggesting an Ediacaran age. These strata are cut by mafic dikes and overlain by basaltic flows with pillow structures. The least altered samples produce flat to slightly positive slopes on trace-element variation diagrams normalized to NMORB and plot within the oceanic floor basalt field of the Ti/V discrimination diagram, mostly within the mid-oceanic ridge tholeiite field with four data points in the alkaline basalt field. The depositional setting and igneous geochemistry suggest hypabyssal volcanism, in a deep-water environment, related to rifting along the continental margin of Laurentia. The transition from rifting to continent margin sedimentation most likely occurred in Ediacaran or earliest Cambrian times in northeast Laurentia. The extent of rifting during emplacement of Franklin LIP and potential separation of Siberia and northern Laurentia are still under question. Current and future work focus on obtaining more precise radiometric age constraints for volcanic and volcaniclastic units discussed above to inform some of these uncertainties.