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Mantle source and melting processes beneath Iceland’s Flank and Rift Zones: Forward Modelling of Heterogeneous Mantle Melting
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  • Emma Christina Waters,
  • Oliver Shorttle,
  • Sæmundur Ari Halldórsson,
  • Katsura Kobayashi,
  • David Neave,
  • Ray Burgess,
  • Margaret E Hartley
Emma Christina Waters
University of Glasgow

Corresponding Author:[email protected]

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Oliver Shorttle
University of Cambridge
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Sæmundur Ari Halldórsson
University of Iceland
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Katsura Kobayashi
ISEI, Okayama University
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David Neave
University of Manchester
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Ray Burgess
University of Manchester
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Margaret E Hartley
University of Manchester
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The Icelandic mantle contains a range of lithologies associated with the depleted upper mantle, a mantle plume, and recycled oceanic lithosphere but the precise nature of depleted and enriched components in the mantle and their relative contributions to melt production remain poorly constrained. In this study, we collect new olivine- and plagioclase-hosted melt inclusion data and compile this with existing literature data to investigate the relative contributions from different mantle lithologies to basaltic magmas erupted in Icelandic flank zones and neovolcanic zones by modelling the melting of a heterogeneous mantle and subsequent mixing of derived melts. We find that observed melt inclusion compositions from off-axis flank zones are best explained as homogenized mixtures of pyroxenite- and lherzolite-derived melts produced at depths around 80-93 km, by which point lherzolite has only experienced a low degree of melting whereas the pyroxenite lithology has melted extensively. These melts represent the onset of channelization in the mantle and are transported rapidly to the surface without input from shallower melts. Melt compositions from the on-axis neovolcanic zones and off-axis Öræfajökull, are produced by mixing this deep melt component with higher degree lherzolite melts produced at shallower depths, between 57-93 km. Proportions of shallow lherzolite-derived melts and deep homogenized melt vary, but the lowest contribution from the deep homogenized melt is seen in the Northern Volcanic Zone. Ourresults support a model whereby deep melts mix until melt channelization starts in the mantle, after which binary mixing between the homogenized deep melt and shallower fractional melts occurs.