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

Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings
Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings
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.
0012-821X
226–236
Agius, Matthew
cb168c8d-0926-4c0d-951c-721fb4cf1ebf
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Laske, Gabi
2a174d97-f878-485a-b2af-7d3e5e6f4aaa
Agius, Matthew
cb168c8d-0926-4c0d-951c-721fb4cf1ebf
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Laske, Gabi
2a174d97-f878-485a-b2af-7d3e5e6f4aaa

Agius, Matthew, Rychert, Catherine, Harmon, Nicholas and Laske, Gabi (2017) Mapping the mantle transition zone beneath Hawaii from Ps receiver functions: Evidence for a hot plume and cold mantle downwellings Earth and Planetary Science Letters, 474, 226–236. (doi:10.1016/j.epsl.2017.06.033).

Record type: Article

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.

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e-pub ahead of print date: 17 July 2017
Published date: 15 September 2017
Organisations: Ocean and Earth Science, Geology & Geophysics

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Local EPrints ID: 411828
URI: http://eprints.soton.ac.uk/id/eprint/411828
ISSN: 0012-821X
PURE UUID: b02c2965-36bc-48b9-a8c4-9a8a014488bd

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Date deposited: 27 Jun 2017 16:31
Last modified: 25 Sep 2017 16:31

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Author: Matthew Agius
Author: Nicholas Harmon
Author: Gabi Laske

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