Hot upper mantle beneath the Tristan da Cunha Hotspot, from probabilistic Rayleigh-wave inversion and petrological modeling


Contact
Wilfried.Jokat [ at ] awi.de

Abstract

Understanding the enigmatic intraplate volcanism in the Tristan da Cunha region requires knowledge of the tem- perature of the lithosphere and asthenosphere beneath it. We measured phase-velocity curves of Rayleigh waves using cross-correlation of teleseismic seismograms from an array of ocean-bottom seismometers around Tristan, constrained a region-average, shear-velocity structure, and inferred the temperature of the lithosphere and asthenosphere beneath the hotspot. The ocean-bottom dataset presented some challenges, which required data-processing and measurement approaches different from those tuned for land-based arrays of stations. Having derived a robust, phase-velocity curve for the Tristan area, we inverted it for a shear-wave velocity profile using a probabilistic (Markov chain Monte Carlo) approach. The model shows a pronounced low-velocity anomaly from 70 to at least 120 km depth. VS in the low velocity zone is 4.1–4.2 km/s, not as low as reported for Hawaii (~4.0 km/s), which probably indicates a less pronounced thermal anomaly and, possibly, less partial melting. Petrological modeling shows that the seismic and bathymetry data is consistent with a moderately warm mantle (mantle potential temperature of 1420–1440ºC, an excess of about 85–105ºC compared to the global average) and a melt fraction smaller than 1%. Both purely seismic inversions and petrological modeling indicate a lithospheric thickness of 65–70 km, consistent with recent estimates from receiver functions. The presence of warmer-than-average asthenosphere beneath Tristan is consistent with a hot upwelling (plume) from the deep mantle. However, the excess temperature we determine is smaller than that reported for some other major hotspots, in particular Hawaii.



Item Type
Conference (Poster)
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
European Geosciences Union General Assembly 2018, 08 Apr 2018 - 13 Apr 2018, Vienna, Austria.
Eprint ID
46600
Cite as
Bonadio, R. , Geissler, W. , Lebedev, S. , Fullea, J. , Ravenna, M. , Celli, N. , Jokat, W. , Jegen, M. , Sens-Schönfelder, C. and Baba, K. (2018): Hot upper mantle beneath the Tristan da Cunha Hotspot, from probabilistic Rayleigh-wave inversion and petrological modeling , European Geosciences Union General Assembly 2018, Vienna, Austria, 8 April 2018 - 13 April 2018 .


Share

Research Platforms
N/A

Campaigns


Actions
Edit Item Edit Item