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| Titel |
CHEMICAL INTERACTION OF Mg-CARBONATE AND THE EARTH'S LOWER MANTLE MINERALS |
| VerfasserIn |
Anna Spivak, Natalia Solopova, Yuriy Litvin, Leonid Dubrovinsky |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075773
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| Zusammenfassung |
| Diamonds of lower mantle origin are rare but important guests at Earth surface currying
crucial information about deep interiors. Apart minerals expected to be similar in Earth
lower mantle (particularly Mg-Fe-Al silicates and MgO-FeO oxides) ultra-deep
diamonds contain primary inclusions of carbonates indicating that they are presented in
the Earth lower mantle. Carbonates of magnesium, calcium, iron and sodium are
stable at wide pressure-temperature conditions close to the geotherm. We studied
interaction of Mg-carbonates with ferropericlase, perovskite employing laser-heated
diamond anvil cell (DAC) at pressures up to 60 GPa and temperatures over 3000
K.
Melting of Mg-carbonate is determined as congruent under PT-conditions of the lower
mantle. The MgCO3 melts are stable in an expanded high-pressure high-temperature field.
We observed formation of diamond at 18 and 40 GPa as a result of decomposition of MgCO3
melt at temperatures above 3500 K on the high-temperature boundary of the field. Melting
reactions of the MgCO3-(Mg,Fe)O system were studied in the 30-63 GPa range at high
temperatures up to 3600 K. It was found that decomposition boundary of MgCO3-(Mg,Fe)O
melt is close to the pure MgCO3 decomposition one within ± 150 K (accuracy of DAC
experiment). Preliminary data shows that perovskite -(Mg,Fe)(Si,Al)O3reacts with MgCO3 at
PT-conditions of 24GPa/2000K and 60GPa/2500K, that is close to the boundary of
congruent MgCO3 melting. The reaction is accompanied with formation of diamond and
MgO.
The experimental data on melting phase relations MgCO3, MgCO3 - (Mg,Fe)O and
MgCO3-(Mg,Fe)(Si,Al)O3 systems combined with diamond crystallization are applied to the
problem of ultra-deep diamond formation in carbonate-bearing parental media of the Earth’s
lower mantle.
This work was funded by the Ministry of education and science of Russian
Federation, project 8317, 16.740.11.0621, grants RFBR 12-05-33044 and 11-05-000401. |
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