Effects of Hydrothermal Vents on Chemistry and Mineralogy of 2021 Fagradalsfjall Eruption

Authors: Dean Wink, Gwenyth Heidinger

Mentors: Ozgur Yavuzecetin, Juk Bhattacharyya

Abstract

The Reykjanes peninsula of Iceland is currently undergoing an intense period of volcanic activity that began back in 2021 with the Fagradalsfjall eruption. Recent studies done by Francesco Sauro indicate rare minerals such as wulffite being found in lava tubes created during the 2011 Fagradalsfjall eruption. There are many hydrothermal vents still active on the 2021 Fagradalsfjall lava field. The rocks around the vent are very discolored indicating chemical changes caused by the hot gasses taking place in the basalt. These changes might indicate new or rare minerals being formed around the vents on the surface similar to those within the lava tubes. Our goal is to better understand the effect of the hydrothermal vents on the mineralogy and chemistry of the altered basalt from around the vents. We collected samples of unaltered basalt and those altered to different degrees by hydrothermal reactions from around the vents for detailed analyses.

We are using powder X-Ray Diffraction (pXRD) to analyze the mineralogy of our samples. We have detected labradorite, forsterite, diopside, and bytownite as the four primary minerals in unaltered samples. Preliminary pXRD results from altered samples from around the vents include zeolites and other layered silicates. We analyzed unaltered and altered basalt samples using an Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) device. Preliminary results show increases in S and Si and decreased levels of Ca, Mn, Fe, Al, Mg, Sr, and K between altered and unaltered basalts from around the vents.

Chemical and mineralogical changes in basaltic lava due to hydrothermal reactions can provide important information about conditions of early life formation and can also create new and rare minerals. Therefore it is important to conduct detailed chemical and mineralogical analyses of samples altered by hydrothermal reactions with fresh lava. Overall, this study aims to find any existing relationship between reactions taking place around the hydrothermal vents found on the surface of the lava field, and the lava tubes created during the same eruption. This presentation will cover our analytical methods, data, and implications of our findings.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5, 2024 doi: 10.1130/abs/2024AM-402039