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Dynamics of a chemically pulsing mantle plume

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journal contribution
posted on 05.05.2020, 10:48 by Rex N Taylor, Pablo Davila-Harris, Michael J Branney, EM Ruth Farley, Thomas M Gernon, Martin R Palmer
Upwelling plumes from the deep mantle have an impact on the Earth's surface for tens to hundreds of millions of years. During the lifetime of a mantle plume, periodic fluctuations in its composition and temperature have the potential to generate changes in the nature and volume of surface volcanism. We constrain the spatial and temporal scale of compositional changes in a plume using high-resolution Pb isotopes, which identify chemical pulses emerging from the Canary Islands hotspot over the last ∼15 million years (Myr). Surface volcanism spanning ∼ 400 km along the island chain changes composition systematically and synchronously, representing a replenishment of the plume head by a distinct mantle flavour on timescales of 3-5 Myr. These low-frequency compositional changes are also recorded by individual volcanoes, and comprise a sequence of closely-spaced isotopic trajectories. Each trajectory is maintained for ∼1 Myr and is preceded and followed by ∼0.3 Myr transitions to magmas with distinct isotope ratios. Relatively sharp transitions between periods of sustained isotopic stability require discrete yet coherent heterogeneities rising at speeds of ∼100-200 km Myr−1 and extending for ∼150 km vertically in the conduit. The long-term synchronous changes require larger scale isotopic domains extending ∼600 km vertically through in the plume stem. These observations demonstrate that plumes can chemically “pulse” over short and long-timescales reflecting the characteristics and recycling history of the deep mantle.

Funding

Thanks to support from Natural Environment Research Council Spitfire grant NE/L00253/1 and Geological Society E. Mathews grants to RNT/EMRF. Andy Milton, Agnes Michalik, Ruth Davey, Lewis Bailey, Kim Dunn and Josh Brown are thanked for laboratory assistance.

History

Citation

Earth and Planetary Science Letters Volume 537, 1 May 2020, 116182

Version

AM (Accepted Manuscript)

Published in

EARTH AND PLANETARY SCIENCE LETTERS

Volume

537

Pagination

116182 (14)

Publisher

ELSEVIER

issn

0012-821X

eissn

1385-013X

Acceptance date

24/02/2020

Copyright date

2020

Available date

09/03/2020

Publisher version

https://www.sciencedirect.com/science/article/pii/S0012821X20301254

Language

English