Vattenhaltiga mineral (pyroxen och olivin) från jordens mantel. Foto: Henrik Skogby

Hydrogen in nominally anhydrous minerals

In this project, we are studying hydrogen stability and redox-exchange mechanisms with the aim to increase the understanding of the effects of hydrogen incorporation in nominally anhydrous minerals.

An important question is whether observed concentrations are representative for the original conditions, or if the kinetics of hydrogen exchange reactions is fast enough to allow re-equilibration during ascent processes.

Project overview

Project period: 2012 – 2024

Participating departments from the museum: Department of Geosciences, GEO

The role of nominally anhydrous minerals (olivine, pyroxene, garnet) in the Earth’s upper mantle has received a strong interest, partly because they provide a water storage mechanism at conditions where hydrous minerals are not stable. Relatively high water concentrations in nominally anhydrous minerals, with contents approaching 1000 ppm H2O may also be found in mantle-derived specimens. Profound effects on physical and chemical properties of the mantle, such as viscosity and electric conductivity, have been demonstrated already at low hydrogen concentrations.

Project description

In this project, we are studying hydrogen stability and redox-exchange mechanisms with the aim to increase the understanding of the effects of hydrogen incorporation in nominally anhydrous minerals. An important question is whether observed concentrations are representative for the original conditions, or if the kinetics of hydrogen exchange reactions is fast enough to allow re-equilibration during ascent processes.

In a sub-project, we are also studying water concentrations in phenocrysts from volcanic rocks. The aim is here to determine water contents in the host magma, which strongly affect the intensity of volcanic eruptions. As magma is largely degassed during eruption, it has been difficult to estimate the original magmatic water content. However, as the water components are better preserved in pyroxene crystals contained in the erupted lava, the original water content can be calculated.

Funding

Swedish Research Council

Selected publications

Radu, IB., Skogby, H., Troll, V.R., Deegan, F.M., Geiger, H., Muller, D. and Thordarson, T. (2023): Water in clinopyroxene from the 2021 Geldingadalir eruption of the Fagradalsfjall Fires, SW-Iceland. Bull Volcanol 85, 31 (2023). https://doi.org/10.1007/s00445-023-01641-4 External link.
Jiang, P., Liu, H., Skogby, H., Chen, R. and Yang, X. (2021): Water in omphacite fingerprints the thermal history of eclogites. Geology 2021; 50 (3): 316–320. doi: https://doi.org/10.1130/G49566.1 External link.
Nazzareni, S., Barbarossa, V., Skogby, H., Zanon, V. & Pettrelli, M. (2020): Magma water content of Pico Volcano (Azores Islands, Portugal): a clinopyroxene perspective. Contributions to Mineralogy and Petrology (2020) 175:87. https://doi.org/1007/s00410-020-01728-7 External link.
Weis, F.A., Bellucci, J.J., Skogby, H., Stalder, R., Nemchin, A.A. and Whitehouse, M.J. (2017): Water content in the Martian mantle: a Nakhla perspective. Geochimica Cosmochimica Acta 212, 84-98. https://doi.org/1016/j.gca.2017.05.041 External link.