Signature of deep mantle melting in South Iceland olivine

• Published in: Contributions to Mineralogy and Petrology
• Main Authors: Nikkola, Paavo, Guðfinnsson, Guðmundur, Bali, Eniko, Rämö, O. Tapani, Fusswinkel, Tobias, Thordarson, Thorvaldur
• Other Authors: Jarðvísindastofnun (HÍ), Institute of Earth Sciences (UI), Faculty of Earth Sciences (UI), Jarðvísindadeild (HÍ), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2019
• Subjects: Iceland; Mantle heterogeneity; Mantle melting; Olivine; Trace elements; Jarðmöttull; Storkuberg; Ari; Berserkjahraun; Maren; Eyjafjallajökull
• Online Access: https://hdl.handle.net/20.500.11815/1755; https://doi.org/10.1007/s00410-019-1580-8

Publisher's version (útgefin grein) We present new high-precision major and trace element data on olivine macrocrysts from various volcano-tectonic settings in Iceland and use these data as a proxy for mantle mode and melting conditions. Within individual sampling sites examined (seven lavas and one tephra) olivine-dominated fractional crystallization, magma mixing and diffusive re-equilibration control observed variability in olivine composition. High-pressure fractional crystallization of clinopyroxene may have lowered Ca and increased Fe/Mn in one olivine population and subsolidus diffusion of Ni and Fe–Mg affected the mantle-derived Ni/Fo ratio in some compositionally zoned olivine macrocrysts. Interestingly, magmas erupted at the southern tip of the Eastern Volcanic Zone (SEVZ), South Iceland, have olivines with elevated Ni and low Mn and Ca contents compared to olivines from elsewhere in Iceland, and some of the SEVZ olivines have relatively low Sc and V and high Cr, Ti, Zn, Cu and Li in comparison to depleted Iceland rift tholeiite. In these olivines, the high Ni and low Mn indicate relatively deep melting (Pfinal > 1.4 GPa, ~ 45 km), Sc, Ti and V are compatible with low-degree melts of lherzolite mantle, and elevated Zn may suggest modal (low-olivine) or geochemical (high Zn) enrichment in the source. The SEVZ olivine macrocrysts probably crystallized from magmas derived from olivine-bearing but relatively deep, enriched and fertile parts of the sub-Icelandic mantle, and indicate swift ascent of magma through the SEVZ lithosphere. Open access funding provided by University of Helsinki including Helsinki University Central Hospital. We thank Matthew Pankhurst and Sæmundur Ari Halldórsson for providing the Eyjafjallajökull 2010 and Berserkjahraun samples, respectively. Maren Kahl is thanked for discussions and Atli Hjartarson for skillfully preparing the samples for microprobe and LA–ICP–MS analyses. Comments from two anonymous reviewers improved the manuscript. This work was funded by the Nordic ...