Dynamics of a chemically pulsing mantle plume
journal contributionposted 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.
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.
CitationEarth and Planetary Science Letters Volume 537, 1 May 2020, 116182
VersionAM (Accepted Manuscript)
Published inEARTH AND PLANETARY SCIENCE LETTERS
Science & TechnologyPhysical SciencesGeochemistry & GeophysicsPb isotopesmantle plumetemporal and spatial volcanismgeochemistrymagmatic evolutionCanary IslandsTenerifeLEAD ISOTOPES REVEALCANARY-ISLANDSTRACE-ELEMENTSHIELD-STAGEGRAN-CANARIAEXPLOSIVE ERUPTIONSINTERNAL STRUCTUREOCEAN-ISLANDPB ISOTOPERIFT-ZONE