Publication Date:
2020-02-12
Description:
The Yellowstone region of western North America presents an example of extreme mantle heterogeneity. According to our P-wave tomography, it accommodates the most massive pile of subducted ocean floor that accumulated anywhere under North America over the past 60+ million years, down to at least 1600~km depth. Paradoxically, Yellowstone is commonly considered a type locality for the exact opposite, a classical deep mantle plume. A robust low-velocity is indeed imaged in the mid mantle, but reaches no deeper than 1000~km, is surrounded by slab, and underlain by more slab. We present our updated finite-frequency model of North America, which now includes data from all of 2008 and 2009, specifically the recent USArray stations east of Yellowstone. We discuss some consequences of the imaged geometry. If a deep mantle plume is indeed present, its “ordinary” operation would seem to have been choked off for a long time interval (on the order of 60 Myr) by slab that was sinking onto it from above and is now located deeper than the current, slow mid-mantle anomaly. The Columbia River flood basalts around 17~Myr would then represent the revival of deep plume operation, rather than the original plume head. Alternatively, we might reject the classical plume hypothesis for Yellowstone, but this leaves us looking for the powerful heat source of the young flood basalts. The imaged geometry suggests a direct relationship to subduction, e.g. dewatering and melting around the 660-km discontinuity.
Type:
info:eu-repo/semantics/conferenceObject
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