Thickness of the oceanic crust, the lithosphere, and the mantle transition zone in the vicinity of the Tristan da Cunha hot spot estimated from ocean-bottom and ocean-island seismometer receiver functions.

Geissler, Wolfram H., Jokat, Wilfried, Jegen, Marion and Baba, Kiyoshi (2017) Thickness of the oceanic crust, the lithosphere, and the mantle transition zone in the vicinity of the Tristan da Cunha hot spot estimated from ocean-bottom and ocean-island seismometer receiver functions. Open Access Tectonophysics, 716 . pp. 33-51. DOI 10.1016/j.tecto.2016.12.013.

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Supplementary data:

Abstract

Highlights

• Receiver functions from ocean-bottom seismometer stations reveal no significant crustal thickening in the surrounding of the Tristan da Cunha hot spot.
• The mantle transition zone to the NW of Tristan da Cunha is thickened and cool.
• The mantle transition zone is potentially thinned to the south/southwest of Tristan da Cunha.
• A thickness of 60 to 75 km beneath Tristan da Cunha argues for a compositional control on the seismological lithosphere in the South Atlantic.

Abstract

The most prominent hotspot in the South Atlantic is Tristan da Cunha, which is widely considered to be underlain by a mantle plume. But the existence, location and size of this mantle plume have not been established due to the lack of regional geophysical observations. A passive seismic experiment using ocean bottom seismometers aims to investigate the lithosphere and upper mantle structure beneath the hotspot. Using the Ps receiver function method we calculate a thickness of 5 to 8 km for the oceanic crust at 17 ocean-bottom stations deployed around the islands. Within the errors of the method the thickness of the oceanic crust is very close to the global mean. The Tristan hotspot seems to have contributed little additional magmatic material or heat to the melting zone at the mid-oceanic ridge, which could be detected as thickened oceanic crust. Magmatic activity on the archipelago and surrounding seamounts seems to have only effected the crustal thickness locally. Furthermore, we imaged the mantle transition zone discontinuities by analysing receiver functions at the permanent seismological station TRIS and surrounding OBS stations. Our observations provide evidence for a thickened (cold) mantle transition zone west and northwest of the islands, which excludes the presence of a deep-reaching mantle plume. We have some indications of a thinned, hot mantle transition zone south of Tristan da Cunha inferred from sparse and noisy observations, which might indicate the location of a Tristan mantle plume at mid-mantle depths. Sp receiver functions image the base of lithosphere at about 60 to 75 km beneath the islands, which argues for a compositionally controlled seismological lithosphere-asthenosphere boundary beneath the study area.

Document Type: Article
Keywords: Receiver functions; Ocean-bottom seismometer; Oceanic crust; Mantle transition zone; Hot spot; Tristan da Cunha; MSM20/2; MSM24; RV Maria S. Merian
Research affiliation: AWI
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.tecto.2016.12.013
ISSN: 0040-1951
Projects: SPP 1375, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 19 Dec 2016 10:31
Last Modified: 22 Jul 2019 12:18
URI: http://oceanrep.geomar.de/id/eprint/35297

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