< 10 Ma Out‐Of‐Sequence Magmatism in Northwest Wyoming (USA): Yellowstone Hotspot—North American Lithosphere Interactions at the Leading Edge of the Snake River Plain

Hotspots are identified by time‐transgressive, linear chains of volcanoes across the crust. The existence of off‐axis or out‐of‐sequence volcanism, where volcanism does not fit in the age progression along a hotspot track, complicates hotspot identification and hotspot‐lithosphere interaction. The Snake River plain–Yellowstone (SRPY) volcanic province is the archetypal example of a continental hotspot, and south‐southeast of Yellowstone, we document ~8–0.5 Ma magmatism. These off‐axis and out‐of‐sequence SRPY rocks formed in an intraplate setting but geochemically resemble subduction zone magmas, which we attribute to metasomatism of Archean Wyoming craton mantle. Off‐axis volcanism exists where mantle upwelling and associated extension occurs (e.g., oceanic hotspots and continental/oceanic rifts). We suggest that off‐axis SRPY magmatism peripheral to Yellowstone is a continental hotspot analogue and occurs due to migrating thermal uplift, mantle melting, and associated lithosphere extension, which facilitates small volume melt production and eruption and is an under‐assessed hazard.