Mineral thought to be abundant in the Earth's mantle
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Wadsleyite
Crystal
General
Category
Sorosilicate
Formula (repeating unit)
Mg2SiO4
IMA symbol
Wds[1]
Strunz classification
9.BE.02
Crystal system
Orthorhombic (Horiuchi and Sawamoto, 1981)
Crystal class
Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group
Imma
Unit cell
a = 5.7 Å, b = 11.71 Å c = 8.24 Å; Z = 8
Identification
Color
Dark green
Crystal habit
Microcrystalline aggregates
Diaphaneity
Transparent
Specific gravity
3.84 calculated
Optical properties
Biaxial
Refractive index
n = 1.76
References
[2][3][4][5]
Wadsleyite is an orthorhombic mineral with the formula β-(Mg,Fe)2SiO4. It was first found in nature in the Peace River meteorite from Alberta, Canada. It is formed by a phase transformation from olivine (α-(Mg,Fe)2SiO4) under increasing pressure and eventually transforms into spinel-structured ringwoodite (γ-(Mg,Fe)2SiO4) as pressure increases further. The structure can take up a limited amount of other bivalent cations instead of magnesium, but contrary to the α and γ structures, a β structure with the sum formula Fe2SiO4 is not thermodynamically stable. Its cell parameters are approximately a = 5.7 Å, b = 11.71 Å and c = 8.24 Å.
Wadsleyite is found to be stable in the upper part of the Transition Zone of the Earth's mantle between 410–520 kilometres (250–320 mi) in depth. Because of oxygen atoms not bound to silicon in the Si2O7 groups of wadsleyite, it leaves some oxygen atoms insufficiently bonded. Thus, these oxygens are hydrated easily, allowing for high concentrations of hydrogen atoms in the mineral. Hydrous wadsleyite is considered a potential site for water storage in the Earth's mantle due to the low electrostatic potential of the under bonded oxygen atoms. Although wadsleyite does not contain H in its chemical formula, it may contain more than 3 percent by weight H2O, and may coexist with a hydrous melt at transition zone pressure-temperature conditions. The solubility of water and the density of wadsleyite depend on the temperature and pressure in the Earth. Even though their maximum water storage capabilities might be reduced to about 0.5–1 wt% along the normal geotherm,[6] the transition zone which holds up to 60 vol% wadsleyite could still be a major water reservoir in the Earth's interior. Furthermore, the transformation resulting in wadsleyite is thought to occur also in the shock event when a meteorite impacts the Earth or another planet at very high velocity.
Wadsleyite was first identified by Ringwood and Major in 1966 and was confirmed to be a stable phase by Akimoto and Sato in 1968.[7] The phase was originally known as β-Mg2SiO4 or "beta-phase". Wadsleyite was named for mineralogist Arthur David Wadsley (1918–1969).
^Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (2022) [2001]. "Wadsleyite". Handbook of Mineralogy(PDF). Chantilly, VA: Mineralogical Society of America. Retrieved 5 July 2022.
^The IMA Mineral List
^Ohtani, Eiji; Litasov, Konstantin; Hosoya, Tomofumi; Kubo, Tomoaki; Kondo, Tadashi (2004). "Water transport into the deep mantle and formation of a hydrous transition zone". Physics of the Earth and Planetary Interiors. 143–144: 255–269. Bibcode:2004PEPI..143..255O. doi:10.1016/j.pepi.2003.09.015. ISSN 0031-9201.
^Akimoto, Syun-iti; Sato, Yosiko (1968). "High-pressure transformation in Co2SiO4 olivine and some geophysical implications". Physics of the Earth and Planetary Interiors. 1 (7): 498–504. Bibcode:1968PEPI....1..498A. doi:10.1016/0031-9201(68)90018-6. ISSN 0031-9201.
Wadsleyite is an orthorhombic mineral with the formula β-(Mg,Fe)2SiO4. It was first found in nature in the Peace River meteorite from Alberta, Canada....
exothermic phase transition to the sorosilicate, wadsleyite and, at about 520 km (320 mi) depth, wadsleyite transforms exothermically into ringwoodite, which...
inferred to be present in large quantities in the Earth's mantle. Olivine, wadsleyite, and ringwoodite are polymorphs found in the upper mantle of the earth...
Mantle Transition Zone is mainly composed of 60 vol% olivine-polymorphs (wadsleyite, ringwoodite) and ~40 vol% majoritic garnet. The top and bottom boundary...
of gas around a forming star. Two polymorphs of forsterite are known: wadsleyite (also orthorhombic) and ringwoodite (isometric, cubic crystal system)...
e., contrary to forsterite there is no intermediate form analogous to wadsleyite; under the conditions prevailing in the upper mantle of the Earth, the...
predicted by the single transition from α- to β- Mg2SiO4 (olivine to wadsleyite). From the Clapeyron slope this discontinuity is expected to be shallower...
phases at the transition zone between Earth's upper and lower mantle, wadsleyite and ringwoodite, could potentially incorporate up to a few weight percent...
below that depth, olivine is converted to the higher-pressure mineral wadsleyite. Oceanic plates consist of up to about 100 km of peridotite covered by...
acceleration. For example, olivine transforms into its denser polymorphs, wadsleyite and ringwoodite, at depths of approximately 410 km and 660 km respectively...
phases (e.g. coesite, akimotoite, majorite, ringwoodite, stishovite, wadsleyite). Water bearing minerals, and samples of liquid water (e.g., Zag, Monahans)...
transition zone, it undergoes a phase transition to wadsleyite, and at about 520 km depth, wadsleyite transforms into ringwoodite, which has the spinel...
crystal is formed by repeating 'Z' times the chemical formula). Examples: wadsleyite (Mg2SiO4) a sorosilicate and high pressure polymorph of forsterite and...
anisotropic material at depth beneath a station. In the transition zone, wadsleyite and/or ringwoodite could be aligned in LPO. Below the transition zone...
(2013). "Water in the Earth's mantle: a solid-state NMR study of hydrous wadsleyite". Chemical Science. 4 (4): 1523. doi:10.1039/c3sc21892a. hdl:1885/77486...
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