A Sr,Nd, Hf,and Pb isotope perspective on the genesis and long-term evolution of alkaline magmas from Erebus volcano,Antarctica |
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| Authors: | Kenneth WW Sims Janne Blichert-Toft Philip R Kyle Sylvain Pichat Pierre-Jean Gauthier Jurek Blusztajn Peter Kelly Lary Ball Graham Layne |
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| Institution: | 1. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States;2. Ecole Normale Supérieure, CNRS UMR 5570, 46 Allée d''Italie, 69364 Lyon, France;3. Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801-4796, United States;4. Laboratoire Magmas et Volcans-Observatoire de Physique du Globe de Clermont-Ferrand (CNRS, UBP)-5 rue Kessler-63000 Clermont-Ferrand, France;5. Climate Change Research Center, University of New Hampshire, Durham, NH 03824, United States;6. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States;g Memorial University INCO Innovation Centre, IIC 1047 St. John''s, Canada NL A1B 3X5 |
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| Abstract: | We report new Nd, Hf, Sr, and high-precision Pb isotopic data for 44 lava and tephra samples from Erebus volcano. The samples cover the entire compositional range from basanite to phonolite and trachyte, and represent all three phases of the volcanic evolution from 1.3 Ma to the present. Isotopic analyses of 7 samples from Mt. Morning and the Dry Valley Drilling Project (DVDP) are given for comparison. The Erebus volcano samples have radiogenic 206Pb/204Pb, unradiogenic 87Sr/86Sr, and intermediate 143Nd/144Nd and 176Hf/177Hf, and lie along a mixing trajectory between the two end-member mantle components DMM and HIMU. The Erebus time series data show a marked distinction between the early-phase basanites and phonotephrites, whose Nd, Hf, Sr, and Pb isotope compositions are variable (particularly Pb), and the current ‘phase-three’ evolved phonolitic lavas and bombs, whose Nd, Hf, Sr, and Pb isotope compositions are essentially invariant. Magma mixing is inferred to play a fundamental role in establishing the isotopic and compositional uniformity in the evolved phase-three phonolites. In-situ analyses of Pb isotopes in melt inclusions hosted in an anorthoclase crystal from a 1984 Erebus phonolite bomb and in an olivine from a DVDP basanite are uniform and identical to the host lavas within analytical uncertainties. We suggest that, in both cases, the magma was well mixed at the time melt inclusions were incorporated into the different mineral phases. |
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| Keywords: | long-lived radiogenic isotopes Mt Erebus alkaline volcanism mantle sources HIMU mantle source Antarctic Volcanism |
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