Temporal evolution of primordial tungsten-182 and 3He/4He signatures in the Iceland mantle plume

• Published in: Chemical Geology
• Main Authors: Mundl-Petermeier, A., Walker, R.J., Jackson, M.G., Blichert-Toft, J., Kurz, M.D., Halldórsson, Sæmundur Ari
• Other Authors: Institute of Earth Sciences (UI), Jarðvísindastofnun (HÍ), School of Engineering and Natural Sciences (UI), Verkfræði- og náttúruvísindasvið (HÍ), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier BV 2019
• Subjects: 3He/4He; Iceland; Mantle plume; Primordial reservoir; μ182W; Möttulstrókur; Jarðmöttull; Basalt; Eldgos; Jarðeðlisfræði; Greenland; North Atlantic; Ocean Island
• Online Access: https://hdl.handle.net/20.500.11815/1613; https://doi.org/10.1016/j.chemgeo.2019.07.026

Publisher's version (útgefin grein). Studies of short-lived radiogenic isotope systems and noble gas isotopic compositions of plume-derived rocks suggest the existence of primordial domains in Earth's present-day mantle. Tungsten-182 anomalies together with high 3He/4He in Phanerozoic rocks from large igneous provinces and ocean island basalts demonstrate the preservation of early-formed (within the first 60 Ma of solar system history) mantle domains tapped by modern mantle plumes. It has proven difficult to link the evidence for primordial domains with geochemical evidence for more recent processes, such as recycling. The Greenland-Iceland plume system, starting with eruptions of the Paleocene North Atlantic Igneous Province, is later manifested in the mid-Miocene to modern volcanic products of Iceland. Here, we report Pb isotopic compositions, μ182W (deviations in 182W/184W of a sample from a laboratory reference standard in parts per million), and 3He/4He, as well as highly siderophile element concentrations and Re-Os isotopic systematics of basaltic samples erupted at different times during the ~60 Ma history of the Greenland-Iceland plume. Paleocene samples from Greenland, representing the early stage of the mantle plume, are characterized by variable 3He/4He ranging from 7 to 48 R/RA (measured 3He/4He normalized to the atmospheric ratio) and an average μ182W of −4.0 ± 3.6 (2SD), within modern upper mantle-like values of 0 ± 4.5. The basalts from Iceland can be divided into two groups based on their Pb isotope compositions. One group, consisting mostly of Miocene basalts, is characterized by 206Pb/204Pb ranging from ~18.4 to 18.5, 3He/4He ranging from 17.8 to 40.2 R/RA, and μ182W values ranging from +1.7 to −9.1 ± 4.5. The other group, consisting mainly of Pleistocene and Holocene basalts, is characterized by higher 206Pb/204Pb, ranging from ~18.7 to 19.2, 3He/4He ranging from 7.9 to 25.7 R/RA, and μ182W values ranging from −0.6 to −11.7 ± 4.5. Collectively, the Greenland-Iceland suite examined requires ...