75-17 Comparing Geochemistry of Olivine Between Fagradalsfjall and Sundhnúkur Basalts

Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

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Recent volcanic episodes in the Reykjanes Peninsula of Iceland began in 2021 in Fagradalsfjall and are continuing today in Sundhnúkur. The two neighboring eruptions are similar in style (effusive lava flows). Observing basalt lava hand samples from both eruptions show the presence of magnesium-rich and iron-rich olivines in very close proximity. Preliminary differences in whole rock chemistry analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) show a higher average iron content from Sundhnúkur basalt and a higher average magnesium content in samples from Fagradalsfjall. Fagradalsfjall basalts have relatively larger olivine crystals than those from Sundhnúkur. Under a petrographic microscope, samples from Sundhnúkur basalt show large clusters of olivine, pyroxene, and plagioclase crystals. Olivine is the first mineral to form from cooling basaltic lava. The chemical and textural differences between olivine crystals in the lava from these volcanoes may indicate the location of the magma source and cooling history. Using data from Powder X-ray Diffraction (PXRD), ICP-OES, and textural analysis under a petrographic microscope, we can observe the differences between the olivine crystals in the same sample as well as differences in samples from Sundhnúkur and Fagradalsfjall. This poster will present data from hand samples, ICP-OES, and PXRD showing the differences between the basalt from the two volcanoes, along with an analysis of the olivine present in both.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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