Water Influence on Mantle Mineralogy

Water dissolved in nominally anhydrous minerals exerts a profound influence on the physical and chemical behaviour of the Earth’s mantle. Even trace amounts of hydroxyl or molecular hydrogen in olivine, pyroxene and garnet can lower melting temperatures, reduce viscosity and modify electrical conductivity. Water is introduced into the mantle via subducted oceanic lithosphere and recycled crustal materials, and it accumulates in the transition zone where pressure‐induced hydration of wadsleyite and ringwoodite creates a vast deep‐mantle reservoir. Hydration weakens peridotite rheology, facilitating mantle flow and slab rollback, while dehydration at greater depths drives flux melting that generates arc magmatism. In upwelling plumes, water enhances melt production and promotes the eruption of continental flood basalts. The distribution and speciation of hydrogen in mantle phases thus underpin geodynamic processes from plate tectonics to intraplate volcanism and control the long‐term evolution of Earth’s water cycle.

Research from Nature Portfolio

Recent high‐pressure experiments on clinopyroxene from a continental flood basalt province have revealed parental magmas with water contents exceeding 1 wt % and a minimum mantle‐source hydration of over 1200 ppm. These findings confirm that a hydrous mantle plume driven by recycled oceanic slab material can trigger large‐volume eruptions. Complementary studies of deep‐mantle eclogite minerals have identified molecular H₂ coexisting with hydroxyl in nominally anhydrous hosts. The presence of H₂ suggests that previous estimates of hydrogen storage in the mantle were too low and provides a new explanation for observed variations in hydrogen isotope ratios of mantle‐derived magmas.

Water Influence on Mantle Mineralogy publication trend

The graph below shows the total number of articles in water influence on mantle mineralogy across all publications each year (not limited to Nature Index journals).

Technical terms

Nominally anhydrous minerals (NAMs): Silicate minerals that lack structural water but can incorporate trace hydrogen as hydroxyl or molecular H₂.

Continental flood basalts (CFBs): Vast volumes of basaltic lava erupted in a geologically brief interval, often linked to deep‐mantle upwellings.

Hydrous defect: A point defect in a mineral crystal where hydrogen bonds to vacancies or substitutes for cations, enabling water incorporation.

Mantle transition zone (MTZ): The depth interval between 410 and 660 km marked by phase changes in olivine that influence water storage capacity.

Rheology: The study of flow and deformation behaviour of rocks under varying temperature, pressure and compositional conditions.

References

1. Hydrous mantle plume promoted the generation of continental flood basalts in the Tarim large igneous province. Scientific Reports (2024).
2. Molecular hydrogen in minerals as a clue to interpret ∂D variations in the mantle. Nature Communications (2020).
3. Build-up of multiple volatiles in Earth's continental keels: Implications for craton stability. Earth and Planetary Science Letters (2023).
4. Water in the upper mantle and deep crust of eastern China: concentration, distribution and implications. National Science Review (2017).
5. Hydrogen incorporation and retention in metamorphic olivine during subduction: Implications for the deep water cycle. Geology (2018).