Late Ediacaran–early Cambrian rifting along the northern margin of Laurentia: constraints from the Yelverton Formation of Ellesmere Island, Canada.

Neoproterozoic to early Paleozoic strata exposed along the northeastern margin of North America (Franklinian Basin) record a prolonged history of rifting and passive margin development. An episode of Ediacaran–Cambrian extension is potentially recorded in volcanic and sedimentary rocks of the Yelverton Formation, exposed on northern Ellesmere Island, Nunavut, Canada. Here, we present new whole-rock trace element and isotope geochemistry and hornblende ⁴⁰Ar/³⁹Ar geochronology from intrusive and extrusive rocks of the Yelverton Formation, along with isotope geochemistry from carbonate rocks underlying the volcanics and detrital zircon U–Pb and Lu–Hf isotopic data from the Yelverton Formation and overlying Grant Land Formation. The carbonate strata yielded an average ⁸⁷Sr/⁸⁶Sr value of 0.7076 (n = 6), constraining the overlying volcanics to the late Ediacaran–early Cambrian (ca. 570–530 Ma). Flows and dikes/sills show three distinct compositions: (1) a depleted, low La/Yb_PM and Th/Nb group, (2) an enriched, higher La/Yb_PM and low Th/Nb group, and (3) a low to moderate La/Yb_PM and high Th/Nb group. One of the high Th/Nb intrusions produced saddle-shaped ⁴⁰Ar/³⁹Ar hornblende spectra with ca. 482 ± 7 Ma age minima and Silurian–Devonian inverse isochron ages, highlighting a hitherto unknown suite of younger intrusions and volcanic rocks. The trace element geochemistry and ¹⁴³Nd/¹⁴⁴Nd_(t) ratios of enriched and depleted volcanic rocks of the indisputable Yelverton Formation are consistent with decompression melting during rifting along a continental margin. We suggest that late Ediacaran–early Cambrian rifting recorded in the Yelverton Formation resulted in the separation of peri-Laurentian terranes, such as the North Slope subterrane and eventual development of the passive margin of northern Laurentia. [ABSTRACT FROM AUTHOR]