WATER, MELTING, AND THE DEEP EARTH H₂O CYCLE

2006/01/31 by M. M. Hirschmann, Marc M. Hirschmann · 4 citations
Earth and Planetary Sciences · #Geological and Geochemical Analysis #High-pressure geophysics and materials #earthquake and tectonic studies

paper · doi:10.1146/annurev.earth.34.031405.125211

openalex publication_date 2006/01/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31

Abstract

Hydrous melting driven by changes in H 2 O storage capacity may occur in a variety of settings in the mantle, including in oceanic basalt sources and in deeper regions above and below the transition zone. The 50–200 ppm H 2 O in the upper mantle likely derives from a blend of sources that may include residues of hydrous partial melting, either in the deep mantle and/or beneath arcs or oceanic islands. Relative to the large storage capacity in the transition zone, low storage capacities above and below may lead to hydrous melting for material upwelling through 410 km or downwelling through 670 km. The apparently very low storage capacity of the lower mantle (<20 ppm H 2 O) may force melting even if downwelling rocks have normal upper mantle H 2 O (50–200 ppm) concentrations. Very low storage capacity in the lower mantle, if verified experimentally, presents a challenge to the view that the H 2 O-rich sources of oceanic island basalts reside in the lower mantle.

Citations

• The composition of the Earth
• Water in the oceanic upper mantle: implications for rheology, melt extraction and the evolution of the lithosphere
• Major and trace element composition of the depleted MORB mantle (DMM)

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• Thin H₂-dominated Atmospheres as Signposts of Magmatic Outgassing on Tidally-Heated Terrestrial Exoplanets
• The structure and elasticity of hydrogrossular under high pressure: Implications for the origin of the low-velocity zone in the mantle
• Seismic evidence of liquid water at the base of Mars’ upper crust
• Imaging the transition from flat to normal subduction: variations in the structure of the Nazca slab and upper mantle under southern Peru and northwestern Bolivia

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• On the Efficacy of Ocean Formation with a Primordial Hydrogen Atmosphere
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• Mantle Differentiation, Mixing and Interior-Exterior Exchange