The stability of anhydrous phase B, Mg14Si5O24, at mantle transition zone conditions

The stability of anhydrous phase B, Mg14Si5O24, at mantle transition zone conditions The stability of anhydrous phase B, Mg14Si5O24, has been determined in the pressure range of 14–21 GPa and the temperature range of 1100–1700 °C with both normal and reversal experiments using multi-anvil apparatus. Our results demonstrate that anhydrous phase B is stable at pressure–temperature conditions corresponding to the shallow depth region of the mantle’s transition zone and it decomposes into periclase and wadsleyite at greater depths. The decomposition boundary of anhydrous phase B into wadsleyite and periclase has a positive phase transition slope and can be expressed by the following equation: P(GPa) = 7.5 + 6.6 × 10−3 T (°C). This result is consistent with a recent result on the decomposition boundary of anhydrous phase B (Kojitani et al., Am Miner 102:2032–2044, 2017). However, our phase boundary deviates significantly from this previous study at temperatures < 1400 °C. Subducting carbonates may be reduced at depths > 250 km, which could contribute ferropericlase (Mg, Fe)O or magnesiowustite (Fe, Mg)O into the deep mantle. Incongruent melting of hydrous peridotite may also produce MgO-rich compounds. Anh-B could form in these conditions due to reactions between Mg-rich oxides and silicates. Anh-B might provide a new interpretation for the origin of diamonds containing ferropericlase–olivine inclusions and chromitites which have been found to have ultrahigh-pressure characteristics. We propose that directly touching ferropericlase–olivine inclusions found in natural diamonds might be the retrogressive products of anhydrous phase B decomposing via the reaction (Mg,Fe)14Si5O24 (Anh-B) = (Mg,Fe)2SiO4 (olivine) + (Mg,Fe)O (periclase). This decomposition may occur during the transportation of the host diamonds from their formation depths of < 500 km in the upper part of the mantle transition zone to the surface. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physics and Chemistry of Minerals Springer Journals

The stability of anhydrous phase B, Mg14Si5O24, at mantle transition zone conditions

9 pages
Read Article

Loading next page...
 
/lp/springer_journal/the-stability-of-anhydrous-phase-b-mg14si5o24-at-mantle-transition-utYmr16nUI
Publisher
Springer Journals
Copyright
Copyright © 2017 by Springer-Verlag GmbH Germany, part of Springer Nature
Subject
Earth Sciences; Mineralogy; Crystallography and Scattering Methods; Geochemistry; Mineral Resources
ISSN
0342-1791
eISSN
1432-2021
D.O.I.
10.1007/s00269-017-0939-5
Publisher site
See Article on Publisher Site

Abstract

The stability of anhydrous phase B, Mg14Si5O24, has been determined in the pressure range of 14–21 GPa and the temperature range of 1100–1700 °C with both normal and reversal experiments using multi-anvil apparatus. Our results demonstrate that anhydrous phase B is stable at pressure–temperature conditions corresponding to the shallow depth region of the mantle’s transition zone and it decomposes into periclase and wadsleyite at greater depths. The decomposition boundary of anhydrous phase B into wadsleyite and periclase has a positive phase transition slope and can be expressed by the following equation: P(GPa) = 7.5 + 6.6 × 10−3 T (°C). This result is consistent with a recent result on the decomposition boundary of anhydrous phase B (Kojitani et al., Am Miner 102:2032–2044, 2017). However, our phase boundary deviates significantly from this previous study at temperatures < 1400 °C. Subducting carbonates may be reduced at depths > 250 km, which could contribute ferropericlase (Mg, Fe)O or magnesiowustite (Fe, Mg)O into the deep mantle. Incongruent melting of hydrous peridotite may also produce MgO-rich compounds. Anh-B could form in these conditions due to reactions between Mg-rich oxides and silicates. Anh-B might provide a new interpretation for the origin of diamonds containing ferropericlase–olivine inclusions and chromitites which have been found to have ultrahigh-pressure characteristics. We propose that directly touching ferropericlase–olivine inclusions found in natural diamonds might be the retrogressive products of anhydrous phase B decomposing via the reaction (Mg,Fe)14Si5O24 (Anh-B) = (Mg,Fe)2SiO4 (olivine) + (Mg,Fe)O (periclase). This decomposition may occur during the transportation of the host diamonds from their formation depths of < 500 km in the upper part of the mantle transition zone to the surface.

Journal

Physics and Chemistry of Minerals – Springer Journals

Published: Dec 27, 2017

References

  • Whole-mantle convection and the transition-zone water filter
    Bercovici, D; Karato, S-i
  • Chromium solubility in anhydrous Phase B
    Bindi, L
  • Experimentally determined postspinel transformation boundary in Mg2SiO4 using MgO as an internal pressure standard and its geophysical implications
    Fei, Y; Orman, JV; Li, J; Westrenen, WV; Sanloup, C; Minarik, W; Hirose, K; Komabayashi, T; Walter, M; Funakoshi, K
  • Crystal chemistry of phase B and an anhydrous analogue: implications for water storage in the upper mantle
    Finger, L
  • Experimental evidence for the existence of iron-rich metal in the Earth’s lower mantle
    Frost, DJ
  • Stability of anhydrous phase B: experimental studies and implications for phase relations in subducting slab and the X discontinuity in the mantle
    Ganguly, J; Frost, DJ
  • Melting of phase D in the lower mantle and implications for recycling and storage of H2O in the deep mantle
    Ghosh, S; Schmidt, MW
  • Mantle recycling: transition zone metamorphism of Tibetan ophiolitic peridotites and its tectonic implications
    Griffin, W
  • Lower mantle diamonds from Rio Soriso (Juina area, Mato Grosso, Brazil)
    Hayman, PC
  • Crystal chemistry of Fe-bearing anhydrous phase B: implications for transition zone mineralogy
    Hazen, RM
  • Melting experiments on chondrite at high pressures: stability of anhydrous Phase B
    Herzberg, C; Gasparik, T
  • Melting experiments on anhydrous peridotite KLB-1: compositions of magmas in the upper mantle and transition zone
    Herzberg, C; Zhang, J
  • High-pressure high-temperature transitions in MgCr2O4 and crystal structures of new Mg2Cr2O5 and post-spinel MgCr2O4 phases with implications for ultrahigh-pressure chromitites in ophiolites
    Ishii, T
  • Incongruent melting of Mg2SiO4 at 20 GPa
    Kato, T; Kumazawa, M
  • Olivine–wadsleyite transition in the system (Mg,Fe)2SiO4
    Katsura, T; Yamada, H; Nishikawa, O; Song, M; Kubo, A; Shinmei, T; Yokoshi, S; Aizawa, Y; Yoshino, T; Walter, MJ; Ito, E
  • Adiabatic temperature profile in the mantle
    Katsura, T; Yoneda, A; Yamazaki, D; Yoshino, T; Ito, E
  • Experimental and thermodynamic investigations on the stability of Mg14Si5O24 anhydrous phase B with relevance to Mg2SiO4 forsterite, wadsleyite, and ringwoodite
    Kojitani, H
  • Melting phase relations in the MgO–MgSiO3 system between 16 and 26GPa: implications for melting in Earth’s deep interior
    Liebske, C; Frost, DJ
  • Phase relations and melt compositions in CMAS–pyrolite–H2O system up to 25 GPa
    Litasov, K; Ohtani, E
  • Phase relations in hydrous MORB at 18–28GPa: implications for heterogeneity of the lower mantle
    Litasov, K; Ohtani, E
  • Melting relations of hydrous pyrolite in CaO–MgO–Al2O3–SiO2–H2O System at the transition zone pressures
    Litasov, K
  • The CaCO3–Fe interaction: kinetic approach for carbonate subduction to the deep Earth’s mantle
    Martirosyan, N
  • Perovskite as a possible sink for ferric iron in the lower mantle
    McCammon, C
  • The composition of liquids coexisting with dense hydrous magnesium silicates at 11–13.5GPa and the endpoints of the solidi in the MgO–SiO2–H2O system
    Melekhova, E
  • Composition of aqueous fluid coexisting with mantle minerals at high pressure and its bearing on the differentiation of the Earth’s mantle
    Mibe, K
  • The phase boundary between α-and β-Mg2SiO4 determined by in situ X-ray observation
    Morishima, H
  • Melting relations of peridotite and the density crossover in planetary mantles
    Ohtani, E
  • Stability of dense hydrous magnesium silicate phases and water storage capacity in the transition zone and lower mantle
    Ohtani, E
  • Thermo-chemical and thermo-physical properties of the high-pressure phase anhydrous B (Mg14Si5O24): an ab-initio all-electron investigation
    Ottonello, G
  • Mantle–slab interaction and redox mechanism of diamond formation
    Palyanov, YN
  • High-pressure reconnaissance investigations in the system Mg2SiO4–MgO–H2O
    Ringwood, A; Major, A
  • Redox freezing and melting in the Earth/’s deep mantle resulting from carbon-iron redox coupling
    Rohrbach, A; Schmidt, MW
  • Metal saturation in the upper mantle
    Rohrbach, A
  • Large gem diamonds from metallic liquid in Earth’s deep mantle
    Smith, EM
  • Kankan diamonds (Guinea) II: lower mantle inclusion parageneses
    Stachel, T
  • High pressure fluids in the system MgO–SiO2–H2O under upper mantle conditions
    Stalder, R
  • In situ determination of the phase boundary between wadsleyite and ringwoodite in Mg2SiO4
    Suzuki, A
  • Origin of podiform chromitite, a new model based on the Luobusa ophiolite, Tibet
    Xiong, F
  • Diamond-and coesite-bearing chromitites from the Luobusa ophiolite
    Yang, J-S
  • Phase transitions of harzburgite and buckled slab under eastern China
    Zhang, Y
  • Experimental constraints on the fate of subducted upper continental crust beyond the “depth of no return”
    Zhang, Y

You’re reading a free preview. Subscribe to read the entire article.

Try 2 weeks free now

DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

or browse the journals available

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off

Sign up
for free
Start 14 day
Free Trial