Anomalous mantle transition zone beneath the Yellowstone hotspot track

• Published in: Nature geoscience Vol. 11; no. 6; pp. 449 - 453
• Main Author: Zhou, Ying
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2018; Nature Publishing Group
• Subjects: 704/2151/210; 704/2151/508; 704/2151/598; Age; Anomalies; Calderas; Crack propagation; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Fracture zones; Geochemistry; Geology; Geophysics/Geodesy; Hot spots; Hot spots (geology); Imaging techniques; Lower mantle; Mantle; Mantle plumes; Polarity; Rivers; Seismic waves; Slope; Subduction; Subduction (geology); Tearing; Tomography; Topography; Topography (geology); Transition zone; Volcanic activity; Volcanic ash; Volcanism
• DOI: 10.1038/s41561-018-0126-4
• ISSN: 1752-0894

The origin of the Yellowstone and Snake River Plain volcanism has been strongly debated. The mantle plume model successfully explains the age-progressive volcanic track, but a deep plume structure has been absent in seismic imaging. Here I apply diffractional tomography to receiver functions recorded at USArray stations to map high-resolution topography of mantle transition-zone discontinuities. The images reveal a trail of anomalies that closely follow the surface hotspot track and correlate well with a seismic wave-speed gap in the subducting Farallon slab. This observation contradicts the plume model, which requires anomalies in the mid mantle to be confined in a narrow region directly beneath the present-day Yellowstone caldera. I propose an alternative interpretation of the Yellowstone volcanism. About 16 million years ago, a section of young slab that had broken off from a subducted spreading centre in the mantle first penetrated the 660 km discontinuity beneath Oregon and Idaho, and pulled down older stagnant slab. Slab tearing occurred along pre-existing fracture zones and propagated northeastward. This reversed-polarity subduction generated passive upwellings from the lower mantle, which ascended through a water-rich mantle transition zone to produce melting and age-progressive volcanism. The mantle transition zone in the western United States is perturbed along a path that mirrors the line of the Yellowstone hotspot track at the surface, according to analysis of tomographic data.