Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling
- Author(s)
- Matthew G. Jackson, Janne Blichert-Toft, Sæmundur A. Halldórsson, Andrea Mundl-Petermeier, Michael Bizimis, Mark D. Kurz, Allison A. Price, Sunna Harðardóttir, Lori N. Willhite, Kresten Breddam, Thorsten W. Becker, Rebecca A. Fischer
- Abstract
Rare high-He-3/He-4 signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth's interior. Only high-He-3/He-4 OIB exhibit anomalous W-182-an isotopic signature inherited during the earliest history of Earth- supporting an ancient origin of high He-3/He-4. However, it is not understood why some OIB host anomalous W-182 while others do not. We provide geochemical data for the highest-He-3/He-4 lavas from Iceland (up to 42.9 times atmospheric) with anomalous W-182 and examine how Sr-Nd-Hf-Pb isotopic variations-useful for tracing subducted, recycled crust-relate to high He-3/He-4 and anomalous W-182. These data, together with data on global OIB, show that the highest-He-3/He-4 and the largest-magnitude W-182 anomalies are found only in geochemically depleted mantle domains-with high Nd-143/Nd-144 and low Pb-206/Pb-204-lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycled materials have low He-3/He-4 and lack anomalous W-182. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth's mantle. We show that high-He-3/He-4 mantle domains with anomalous W-182 have low W and He-4 concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low He-3/He-4 and normal (not anomalous) W-182 characteristic of subducted crust. Thus, high He-3/He-4 and anomalous W-182 are preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high He-3/He-4 and anomalous W-182 in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth's interior.
- Organisation(s)
- Department of Lithospheric Research
- External organisation(s)
- University of Iceland, University of California, Santa Barbara, University of Maryland, College Park, Danish Health and Medicines Authority, University of Texas, Austin, Harvard University, École normale supérieure de Lyon (ENS Lyon), Institute for Electronics, Microelectronics, and Nanotechnology (CNRS UMR 8520), University of South Carolina, Columbia, Woods Hole Oceanographic Institution
- Journal
- Proceedings of the National Academy of Sciences of the United States of America (PNAS)
- Volume
- 117
- Pages
- 30993–31001
- No. of pages
- 9
- ISSN
- 0027-8424
- DOI
- https://doi.org/10.1073/pnas.2009663117
- Publication date
- 2020
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105105 Geochemistry
- Keywords
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/72f89d98-f1bf-4297-9561-aed399bef517