The pyrite-type high-pressure form of FeOOH

  title={The pyrite-type high-pressure form of FeOOH},
  author={Masayuki Nishi and Yasuhiro Kuwayama and Jun Tsuchiya and Taku Tsuchiya},
Water transported into Earth’s interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth’s deep interior, implying that surface water may be transported as far as the core–mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to… 

Deep mantle hydrogen in the pyrite-type FeO2–FeO2H system

Partial Deoxygenation and Dehydration of Ferric Oxyhydroxide in Earth's Subducting Slabs

The thermal stability of hydrous minerals in Earth's deep interior is key to understanding the evolution and physicochemical states of the planet. The recently discovered pyrite‐type (Py) FeO2Hx (x ≤

Superionic iron oxide–hydroxide in Earth’s deep mantle

Water ice becomes a superionic phase under the high pressure and temperature conditions of deep planetary interiors of ice planets such as Neptune and Uranus, which affects interior structures and

Evidence for oxygenation of Fe-Mg oxides at mid-mantle conditions and the rise of deep oxygen

The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure and the emergence of oxygen-excess reservoirs out of primordial or subducted (Mg, Fe)-bearing hydrous materials may revise the view on the deep-mantle redox chemistry.

The role of water in Earth's mantle

Geophysical observations suggest that the transition zone is wet locally and Pyrite FeO2Hx is formed due to a reaction between the core and hydrated slabs could be a candidate for the anomalous regions at the core–mantle boundary.

Mineralogy of the deep lower mantle in the presence of H2O

High pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM), observed surprising mineralogical transformations in the presence of water and identified an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences.

Effect of Fe3+ on Phase Relations in the Lower Mantle: Implications for Redox Melting in Stagnant Slabs

Recent studies have revealed that Earth's deep mantle may have a wider range of oxygen fugacities than previously thought. Such a large heterogeneity might be caused by material subducted into the

Elasticity and Anisotropy of the Pyrite-Type FeO2H-FeO2 System in Earth’s Lowermost Mantle

The pyrite-type FeO2H-FeO2 system has been experimentally confirmed to be stable in Earth’s lowermost mantle but there is limited information about its physical properties at high pressures



Dehydrogenation of goethite in Earth’s deep lower mantle

Observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.

Stability of hydrous silicate at high pressures and water transport to the deep lower mantle

Hydrous magnesium-rich silicates play an important role in transporting water into the deep mantle when oceanic plates subduct as slabs, but were thought to dissociate at pressures of 44 GPa. In situ

FeO2 and FeOOH under deep lower-mantle conditions and Earth's oxygen-hydrogen cycles.

This process provides an alternative interpretation for the origin of seismic and geochemical anomalies in the deep lower mantle, as well as a sporadic O2 source for the Great Oxidation Event over two billion years ago that created the present oxygen-rich atmosphere.

Deep penetration of molten iron into the mantle caused by a morphological instability

It is shown that (Mg,Fe)O in contact with iron-rich liquids leads to a morphological instability, causing blobs of Iron-rich liquid to penetrate the oxide, which should be a common process in Earth’s interior.

Experimental evidence for the existence of iron-rich metal in the Earth's lower mantle

The Fe3+ content of aluminous silicate perovskite, the dominant lower-mantle mineral, is independent of oxygen fugacity and it is argued that the lower mantle contains approximately 1 wt% of a metallic iron-rich alloy.

Low Core-Mantle Boundary Temperature Inferred from the Solidus of Pyrolite

The experimentally determined maximum melting point of 3570 kelvin suggests that some phases typically thought to lose stability in the lowermost mantle, such as MgSiO3-rich post-perovskite, may be more widely distributed than expected.

Crystal structure, equation of state, and elasticity of phase H (MgSiO4H2) at Earth’s lower mantle pressures

The calculated elastic wave velocities and anisotropies indicate that phase H can be a source of significant seismic anisotropy in the lower mantle.