Linking the Spin Transition of Ferric Iron in δ-(Al,Fe)OOH to Water Storage in the Lower Mantle

DOI zum Zitieren der Version auf EPub Bayreuth: https://doi.org/10.15495/EPub_UBT_00009050
URN to cite this document: urn:nbn:de:bvb:703-epub-9050-3

Title data

Buchen, Johannes ; Pardo, Olivia S. ; Dobrosavljevic, Vasilije V. ; Sturhahn, Wolfgang ; Ishii, Takayuki ; Chariton, Stella ; Greenberg, Eran ; Toellner, Thomas S. ; Jackson, Jennifer M.:
Linking the Spin Transition of Ferric Iron in δ-(Al,Fe)OOH to Water Storage in the Lower Mantle.
In: Journal of Geophysical Research: Solid Earth. Vol. 130 (2025) Issue 8 . - e2025JB031715.
ISSN 2169-9356
DOI der Verlagsversion: https://doi.org/10.1029/2025JB031715

	Format: PDF Name: JGR Solid Earth - 2025 - Buchen - Linking the Spin Transition of Ferric Iron in ‐ Al Fe OOH to Water Storage in the Lower.pdf Version: Published Version Available under License Creative Commons BY 4.0: Attribution
	Download (1MB)

Project information

Project title:	Project's official title Project's id Open Access Publizieren No information

Abstract

As the most massive geochemical reservoir, the lower mantle affects the Earth's budget of volatile elements, including hydrogen or H₂O. The properties of minerals in the lower mantle are further affected by changes in the electronic configurations of iron cations, that is, by spin transitions. The feedback between spin transitions and potential storage of H₂O in solid hydrous phases in the lower mantle, however, remains unexplored. By combining high-pressure nuclear resonant inelastic X-ray scattering and high-pressure high-temperature X-ray diffraction experiments, we constrained the thermal equation of state of δ-(Al,Fe)OOH, a member of the phase H solid solution. Based on the derived thermal equation of state of δ-(Al,Fe)OOH and the underlying thermodynamic model, we calculate the excess Gibbs free energy that arises from the spin transition of ferric iron in this compound and evaluate the effect on phase equilibria. The results of our analysis show that the spin transition of ferric iron in phase H may significantly reduce the thermodynamic activity and hence the concentration of H₂O in a coexisting hydrous melt. As a consequence, nominally anhydrous minerals of the lower mantle may become dehydrated in the presence of phase H. Our analysis further suggests that, under certain conditions, the spin transition may expand the thermal stability of Fe³⁺-bearing phase H and create a geochemical link between the storage of H₂O in phase H and ferric iron in the lower mantle.

Further data

Item Type:	Article in a journal
Keywords:	spin transition; phase H; lower mantle; high pressure; equation of state; phonon density of states
DDC Subjects:	500 Science > 550 Earth sciences, geology
Institutions of the University:	Research Institutions > Central research institutes > Bavarian Research Institute of Experimental Geochemistry and Geophysics - BGI Research Institutions Research Institutions > Central research institutes
Language:	English
Originates at UBT:	Yes
URN:	urn:nbn:de:bvb:703-epub-9050-3
Date Deposited:	30 Mar 2026 13:21
Last Modified:	30 Mar 2026 13:22
URI:	https://epub.uni-bayreuth.de/id/eprint/9050

Download Statistics

Download Statistics

Download Statistics

Downloads

Downloads per month over past year