Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings

TitleMapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings
Publication TypeJournal Article
Year of Publication2017
AuthorsAgius M.R, Rychert C.A, Harmon N., Laske G.
JournalEarth and Planetary Science Letters
Volume474
Pagination226-236
Date Published2017/09
Type of ArticleArticle
ISBN Number0012-821X
Accession NumberWOS:000409150600025
Keywords660 km discontinuity; constraints; discontinuities; hawaii; mantle; mantle plume; modified spinel; network pilot experiment; ocean; phase-changes; receiver functions; seismic evidence; Seismology; swell-evidence; system mg2sio4-fe2sio4; transition zone; volcanism
Abstract

Hawaii is the archetypal example of hotspot volcanism. Classic plume theory suggests a vertical plume ascent from the core-mantle boundary to the surface. However, recently it has been suggested that the plume path may be more complex. Determining the exact trajectory of the Hawaiian plume seismic anomaly in the mantle has proven challenging. We determine P-to-S (Ps) receiver functions to illuminate the 410- and 660-km depth mantle discontinuities beneath the Hawaiian Islands using waveforms recorded on land and ocean-bottom seismometers, applying new corrections for tilt and coherence to the ocean bottom data. Our 3-D depth-migrated maps provide enhanced lateral resolution of the mantle transition zone discontinuities. The 410 discontinuity is characterised by a deepened area beneath central Hawaii, surrounded by an elevated shoulder. At the 660 discontinuity, shallow topography is located to the north and far south of the islands, and a deep topographic anomaly is located far west and east. The transition zone thickness varies laterally by 13 km depth: thin beneath north-central Hawaii and thick farther away in a horseshoe-like feature. We infer that at 660-km depth a broad or possibly a double region of upwelling converges into a single plume beneath central Hawaii at 410-km depth. As the plume rises farther, uppermost mantle melting and flow results in the downwelling of cold material, down to at least 410 km surrounding the plume stem. This result in the context of others supports complex plume dynamics including a possible non-vertical plume path and adjacent mantle downwellings. (C) 2017 The Author(s). Published by Elsevier B.V.

DOI10.1016/j.epsl.2017.06.033
Short TitleEarth Planet. Sci. Lett.
Student Publication: 
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