Hunting for the Tristan mantle plume – An upper mantle tomography around the volcanic island of Tristan da Cunha

Abstract Southern Africa is characterised by unusually elevated topography and abnormal heat flow. This can be explained by thermal perturbation of the mantle, but the origin of this is unclear. Geophysics has not detected a thermal anomaly in the upper mantle and there is no geochemical evidence of an asthenosphere mantle contribution to the Cenozoic volcanic record of the region. Here we show that natural CO2 seeps along the Ntlakwe-Bongwan fault within KwaZulu-Natal, South Africa, have C-He isotope systematics that support an origin from degassing mantle melts. Neon isotopes indicate that the melts originate from a deep mantle source that is similar to the mantle plume beneath Réunion, rather than the convecting upper mantle or sub-continental lithosphere. This confirms the existence of the Quathlamba mantle plume and importantly provides the first evidence in support of upwelling deep mantle beneath Southern Africa, helping to explain the regions elevation and abnormal heat flow.

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Long-Lived Mantle Plume and Polyphase Evolution of Palaeoproterozoic PGE Intrusions in the Fennoscandian Shield

Minerals ◽

10.3390/min9010059 ◽

2019 ◽

Vol 9 (1) ◽

pp. 59 ◽

Cited By ~ 10

Author(s):

Tamara Bayanova ◽

Aleksey Korchagin ◽

Alexander Mitrofanov ◽

Pavel Serov ◽

Nadezhda Ekimova ◽

...

Keyword(s):

Mantle Plume ◽

Mantle Source ◽

Upper Mantle ◽

Large Scale ◽

Fennoscandian Shield ◽

Olivine Gabbro ◽

Final Phase ◽

Mafic Intrusions ◽

Enriched Mantle ◽

Mantle Reservoir

The NE Fennoscandian Shield comprises the Northern Belt in Finland and the Southern Belt in Karelia. They host mafic-ultramafic layered Cu-Ni-Cr and Pt-Pd-bearing intrusions. Precise U-Pb and Sm-Nd analyses indicate the 130-Ma evolution of these intrusions, with major events at 2.53, 2.50, 2.45, and 2.40 Ga. Barren phases were dated at 2.53 Ga for orthopyroxenites and olivine gabbro in the Fedorovo-Pansky massif. PGE-bearing phases of gabbronorites (Pechenga, Fedorovo-Pansky, Monchetundra massifs) and norites (Monchepluton) are 2.50 Ga old. Anorthosites of Mt. Generalskaya (Pechenga), the Fedorovo-Pansky, and Monchetundra massifs occurred at 2.45 Ga. This event produced layered PGE-bearing intrusions in Finland (Penikat, Kemi, Koitelainen) and mafic intrusions in Karelia. The Imandra lopolith dikes occurred at the final phase (2.40 Ga). Slightly negative εNd and ISr values (0.703–0.704) suggest that intrusions originated from an enriched mantle reservoir. Low 3He/4He ratios in accessory minerals (ilmenite and magnetite) indicate an upper mantle source. Large-scale correlations link the Fennoscandian Shield with the Superior and Wyoming cratons.

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Source bias in epicenter determinations

Bulletin of the Seismological Society of America ◽

10.1785/bssa0580061791 ◽

1968 ◽

Vol 58 (6) ◽

pp. 1791-1796

Author(s):

Eugene Herrin ◽

James Taggart

Keyword(s):

Upper Mantle ◽

Significant Source ◽

Volcanic Island ◽

Constant Delay ◽

Origin Time ◽

Station Corrections ◽

The Pacific ◽

Tectonically Active ◽

Using Data ◽

Consistent Error

ABSTRACT Epicenter determinations using data from stations at distances greater than 20° from the source make use of standard travel times based on a spherically symmetrical Earth. Lateral inhomogeneities in the upper mantle result in relative delays with respect to the standard times. Delays associated with the end of the up-traveling ray can be handled through the use of station corrections. A constant delay beneath the source can not be easily corrected, but it will result only in errors in origin time. However, if the delay arising beneath the source changes with azimuth, a consistent error, here called source bias, will be present in the estimate of the epicenter. Studies of explosions within continental masses have revealed no significant source bias; however, events on two linear, volcanic island chains in the Pacific (Rat Islands-Aleutians and Hawaii) show significant source bias. Errors arising from this effect may be as large as 12 degree and are most likely to occur with events near tectonically active island chains.

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Intra-plate volcanism

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1978.0034 ◽

1978 ◽

Vol 288 (1355) ◽

pp. 561-579 ◽

Cited By ~ 56

Keyword(s):

United States ◽

Mantle Plume ◽

Thermal Convection ◽

Upper Mantle ◽

Alternative Hypothesis ◽

Significant Fraction ◽

Western United States ◽

Mantle Plumes ◽

Plate Margin

A significant fraction of the volcanism on the Earth’s surface cannot be associated with plate margin processes. The mantle plume hypothesis is one explanation for this volcanism. Convective plumes beneath rigid plates could be the result of turbulent thermal convection within the upper mantle. Although the hypothesis of nearly fixed mantle plumes is reasonably successful in explaining the direction and velocity of migration of intra-plate volcanism, there are a number of difficulties. It is particularly difficult to explain continued volcanism over extended linear distances. An alternative hypothesis for intra-plate volcanism is that magmas flow to the surface through lithospheric fractures. In this case intra-plate volcanism would be associated with tensional tectonics. Intra-plate volcanism and seismicity in Africa and the western United States are discussed in terms of these hypotheses.

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Characteristics of Upper Mantle Activity in the South China Sea Region and the Indochina Mantle Plume

Acta Geologica Sinica - English Edition ◽

10.1111/j.1755-6724.1999.tb00856.x ◽

1999 ◽

Vol 73 (4) ◽

pp. 464-476 ◽

Cited By ~ 3

Author(s):

WU Nengyou ◽

ZENG Weijun ◽

LI Zhenwu ◽

CHEN Yizhong ◽

WEN Xiwen ◽

...

Keyword(s):

South China Sea ◽

Mantle Plume ◽

South China ◽

Upper Mantle ◽

The South China Sea ◽

The South ◽

China Sea

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Integrated geophysical-petrological modelling of the Eifel region

10.5194/egusphere-egu2020-2305 ◽

2020 ◽

Author(s):

Agnes Wansing ◽

Jörg Ebbing ◽

Eva Bredow

Keyword(s):

Mantle Plume ◽

Upper Mantle ◽

West Germany ◽

Small Scale ◽

Low Velocity ◽

Crust And Upper Mantle ◽

Quaternary Volcanism ◽

Velocity Anomaly ◽

Type Composition ◽

Eifel Region

We present an integrated geophysical-petrological model of the Eifel region. The Eifel is a volcanic active region in West Germany that exhibits Tertiary as well as Quaternary volcanism. One suggestion for the source of this volcanism is a small-scale upper mantle plume.The 3D model includes the crust and upper mantle and was generated by combined modelling of topography and the gravity field with constraints from seismology and geochemistry. In the best-fit model, the subcontinental lithospheric mantle is associated with a Phanerozoic-type composition, resulting in a depth of 80 km for the lithosphere-asthenosphere boundary (LAB) beneath the Eifel and in comparison 110 - 130 km beneath the Paris basin. A Proterozoic-type composition in contrast results in a LAB depth of 120 km in the Eifel. While the model fits the geophysical observables and features a thin lithosphere, it does not lead to a plume-like structure and does not feature a seismic low-velocity anomaly.The measured low-velocity anomaly can be reproduced by introducing (1) an even thinner lithosphere or (2) a plume-like body above the thermal LAB with a composition based on data from Eifel xenoliths, which have a mainly basanitic composition. This additional structure results in a thermal anomaly and has an effect on the isostatic elevation of c. 360 m, but it does not result in a significant signal in the gravity anomalies. Further modelling showed how crustal intrusions could additionally mask the gravitational effect from such a small-scale upper mantle plume.The model does not conclusively explain the source of the Eifel volcanism, but the models and the calculation of synthetic dispersion curves help to assess the possibility to resolve a small-scale upper mantle plume with joint inversion in future analysis.

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Petrological and geochemical variations along the Mid-Atlantic Ridge between 46°S and 32°S: influence of the Tristan da Cunha mantle plume

Deep Sea Research Part B Oceanographic Literature Review ◽

10.1016/0198-0254(85)93890-7 ◽

1985 ◽

Vol 32 (12) ◽

pp. 1031

Keyword(s):

Mantle Plume ◽

Tristan Da Cunha ◽

Geochemical Variations ◽

Mid Atlantic Ridge

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Seismic evidence for a thermochemical mantle plume underplating the lithosphere of the Ontong Java Plateau

Communications Earth & Environment ◽

10.1038/s43247-021-00169-9 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Takehi Isse ◽

Daisuke Suetsugu ◽

Akira Ishikawa ◽

Hajime Shiobara ◽

Hiroko Sugioka ◽

...

Keyword(s):

Mantle Plume ◽

Upper Mantle ◽

Seismic Data ◽

Three Dimensional ◽

Ontong Java Plateau ◽

Volcanic Event ◽

Upper Mantle Structure ◽

Residual Material ◽

Passive Seismic ◽

The Western Pacific

AbstractThe Ontong Java Plateau in the western Pacific Ocean is the world’s largest oceanic plateau. It was formed 122 million years ago by a massive volcanic event that significantly affected Earth’s environment. The cause of the magmatic event remains controversial because the upper mantle structure beneath the plateau is poorly known. Here we use passive seismic data obtained through seafloor observations, alongside existing seismic data, to determine the three-dimensional radially anisotropic shear wave velocity to depths of up to 300 km. We find that the lithosphere–asthenosphere boundary is approximately 40 km deeper beneath the centre of the Ontong Java Plateau than beneath the surrounding seafloor. Based on our results and petrological and rheological constraints, we propose that the lithosphere–asthenosphere boundary has deepened as a result of underplating of dehydrated residual material beneath the pre-existing lithosphere during formation of the Ontong Java Plateau by a thermochemical mantle plume.

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