Upper mantle control on the W isotope record of shallow level plume and intraplate volcanic settings

Jansen, M. W., Tusch, J., Münker, C., Bragagni, A., Avanzinelli, R., Mastroianni, F., Stuart, F. M. and Kurzweil, F. (2022) Upper mantle control on the W isotope record of shallow level plume and intraplate volcanic settings. Earth and Planetary Science Letters, 585, 117507. (doi: 10.1016/j.epsl.2022.117507)

Abstract

Several studies have revealed small heterogeneities in the relative abundance of 182W, the radiogenic nuclide of short-lived 182Hf (t1/2 = ∼9 Ma), in terrestrial rocks. Whereas the majority of Archean rocks display 182W excesses relative to bulk silicate Earth, many young ocean island basalts show small 182W deficits, in particular if they are sourced from deep-rooted mantle plumes. The origin of this anomaly is still ambiguous, proposed models focus on core-mantle interaction or the presence of reservoirs in the lower mantle that have been isolated since the Hadean. In order to evaluate the role of upper mantle reservoirs, we report the first 182W data for intraplate basalts where a deep plume origin is still debated (Ascension Island, Massif Central, Siebengebirge and Eifel) and intraplate volcanic rocks associated with either plume or subduction zone environments (Italian Magmatic Provinces) and compare them to new data for basalts that have a deep mantle plume origin (La Réunion and Baffin Island). The proto-Iceland plume basalts from Baffin Island have uniform and modern mantle-like W of around 0 despite extremely high (3He/4He). In contrast, basalts from both volcanic edifices from La Réunion span a range from modern upper mantle values to deficits as low as W = −8.8 ppm, indicating a heterogeneous source reservoir. The W in all other intraplate volcanic provinces overlap the composition of modern upper mantle to within 3 ppm. The absence of resolvable 182W anomalies in these intraplate basalts, which partially tap the lithospheric mantle, suggests that primordial components are neither present in the central and southern European lithosphere nor in the European asthenospheric reservoir (EAR). The general absence of 182W anomalies in European plume-related basalts can either be explained by a shallow mantle source or by the absence of isotopically anomalous and isolated domains in the deep mantle beneath the northern hemisphere, as also suggested by geophysical evidence.

• Item Type: Articles
• Additional Information: Financial support for this study was provided by the European Research Council (ERC grant no. 669666) to C.M. Frank Wombacher is thanked for his help performing trace element analysis using the ThermoFisher iCap-Q at the University of Cologne.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Stuart, Professor Fin
• Authors: Jansen, M. W., Tusch, J., Münker, C., Bragagni, A., Avanzinelli, R., Mastroianni, F., Stuart, F. M., and Kurzweil, F.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Earth and Planetary Science Letters
• Publisher: Elsevier
• ISSN: 0012-821X
• ISSN (Online): 1385-013X
• Published Online: 20 April 2022
• Copyright Holders: Copyright © 2022 The Author(s)
• First Published: First published in Earth and Planetary Science Letters 585: 117507
• Publisher Policy: Reproduced under a Creative Commons licence