Historic magmatism on the Reykjanes Peninsula,Iceland: a snap-shot of melt generation at a ridge segment |
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Authors: | David W Peate Joel A Baker Sveinn P Jakobsson Tod E Waight Adam J R Kent Nathalie V Grassineau Anna Cecile Skovgaard |
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Institution: | 1.Department of Geoscience,University of Iowa,Iowa City,USA;2.School of Geography, Environmental and Earth Sciences,Victoria University of Wellington,Wellington,New Zealand;3.Icelandic Institute of Natural History,Reykjavik,Iceland;4.Geological Institute,University of Copenhagen,Copenhagen K,Denmark;5.Department of Geosciences,Oregon State University,Corvallis,USA;6.Department of Geology,Royal Holloway University of London,Egham, Surrey,UK;7.Danish Environmental Protection Agency,Copenhagen,Denmark |
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Abstract: | We present new compositional data on a suite of historic lava flows from the Reykjanes Peninsula, Iceland. They were erupted
over a short time period between c. 940 and c. 1340 ad and provide a snap-shot view of melt generation and evolution processes beneath this onshore, 65 km long, ridge segment.
The lavas are tholeiitic basalts (MgO 6.5–9.2 wt%) and sparsely (≪5%) olivine and/or plagioclase phyric (±trace clinopyroxene).
Individual eruptive events show remarkable compositional homogeneity. Despite a limited variation in Sr–Nd isotope compositions,
high-precision double-spike Pb isotope data show tight coherent arrays that, together with correlations with incompatible
trace element ratios, indicate control by binary mixing processes. Poor correlations with elemental abundances require that
this mixing took place prior to extensive fractional crystallisation. Olivines in the historic lavas have light δ18O values (+4.2 to +4.3‰), which is likely to be a feature of the enriched mantle source to Reykjanes Peninsula lavas. High
precision Pb isotope analyses of other post-glacial Reykjanes Peninsula lavas show significant variability in 207Pb/204Pb and 208Pb/204Pb at lower 206Pb/204Pb values than in the historic lavas. This variation demonstrates that at least three compositionally distinct components
within the mantle are required to explain the Pb isotope variations within the Reykjanes Peninsula as a whole.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Iceland Mixing Tholeiitic basalts High-precision Pb isotopes |
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