Aluminium drives hydrogen incorporation in pyrolitic lower mantle: Constraints from a combined FTIR-ERDA-nanoSIMS analysis
Abstract
Hydrogen is present as hydroxyl (OH) defects in the crystal lattices of the nominally anhydrous minerals (NAMs) composing the Earth’s mantle. The NAMs comprising the lower mantle: bridgmanite, ferropericlase, and davemaoite are the three most abundant minerals on Earth, and thus their combined hydrogen solubility exerts a first-order control on the planetary H2O capacity and overall H2O cycle. In this study, we equilibrated the three principal NAMs with hydrous melt at the adiabatic geotherm and pressure corresponding to the shallow lower mantle. The H2O content of the coexisting NAMs is quantified by nanoSIMS using matrix-matched standards characterized by Fourier Transform Infrared (FTIR) spectroscopy combined with Elastic Recoil Detection Analysis (ERDA). Our results show that bridgmanite, ferropericlase, and davemaoite incorporate ∼0.030, ∼0.16, and ∼0.18 wt% H2O, respectively. Our data further suggests that hydrogen is primarily incorporated via Al3+-H+ insertion at the Si4+ (octahedral) site in perovskite-type structures and at the metal (octahedral) site in ferropericlase. Finally, we refine a maximum H2O content of 0.058 (0.009) wt% H2O in a pyrolitic-shallow lower mantle, which is equivalent to ∼1.26 (0.19) ocean masses when extrapolated to a chemically homogeneous lower mantle.
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BibTeX
@article{khan2026aluminium,
title = {{Aluminium drives hydrogen incorporation in pyrolitic lower mantle: Constraints from a combined FTIR-ERDA-nanoSIMS analysis}},
author = {Siddharth Khan and Nathalie Bolfan-Casanova and Maximilien Verdier-Paoletti and Hélène Bureau and Hicham Khodja and Ana Pradas del Real and Denis Andrault},
journal = {Geochimica et Cosmochimica Acta},
year = {2026},
month = oct,
doi = {10.1016/j.gca.2026.08.011},
url = {https://hal.science/hal-05837530v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Aluminium drives hydrogen incorporation in pyrolitic lower mantle: Constraints from a combined FTIR-ERDA-nanoSIMS analysis
AU - Siddharth Khan
AU - Nathalie Bolfan-Casanova
AU - Maximilien Verdier-Paoletti
AU - Hélène Bureau
AU - Hicham Khodja
AU - Ana Pradas del Real
AU - Denis Andrault
PY - 2026
DA - 2026/10/26
JO - Geochimica et Cosmochimica Acta
DO - 10.1016/j.gca.2026.08.011
UR - https://hal.science/hal-05837530v1
AB - Hydrogen is present as hydroxyl (OH) defects in the crystal lattices of the nominally anhydrous minerals (NAMs) composing the Earth’s mantle. The NAMs comprising the lower mantle: bridgmanite, ferropericlase, and davemaoite are the three most abundant minerals on Earth, and thus their combined hydrogen solubility exerts a first-order control on the planetary H2O capacity and overall H2O cycle. In this study, we equilibrated the three principal NAMs with hydrous melt at the adiabatic geotherm and pressure corresponding to the shallow lower mantle. The H2O content of the coexisting NAMs is quantified by nanoSIMS using matrix-matched standards characterized by Fourier Transform Infrared (FTIR) spectroscopy combined with Elastic Recoil Detection Analysis (ERDA). Our results show that bridgmanite, ferropericlase, and davemaoite incorporate ∼0.030, ∼0.16, and ∼0.18 wt% H2O, respectively. Our data further suggests that hydrogen is primarily incorporated via Al3+-H+ insertion at the Si4+ (octahedral) site in perovskite-type structures and at the metal (octahedral) site in ferropericlase. Finally, we refine a maximum H2O content of 0.058 (0.009) wt% H2O in a pyrolitic-shallow lower mantle, which is equivalent to ∼1.26 (0.19) ocean masses when extrapolated to a chemically homogeneous lower mantle.
SN - 0016-7037
SN - 1872-9533
ER -