Abstract
The phase relations in the Na2CO3-(Fe0.87Mn0.06Mg0.07)CO3 system have been studied in Kawai-type multi-anvil experiments using graphite capsules at 6.0 GPa and 900-1400 °C. Subsolidus assemblages comprise the stability fields of Na2CO3 + Na2Fe(CO3)2 and Na2Fe(CO3)2 + siderite with the transition boundary at X(Na2CO3) = 50 mol%. Intermediate Na2Fe(CO3)2 compound has rhombohedral R3 eitelite structure with cell parameters a = 4.9712(16), c = 16.569(4) A˚, V = 354.61(22). The Na2CO3- Na2Fe(CO3)2 eutectic is established at 1000 °C and 66 mol% Na2CO3· Na2Fe(CO3)2 disappears between 1000 and 1100 °C via incongruent melting to siderite and a liquid containing about 55 mol% Na2CO3. Siderite remains a subliquidus phase at 1400 °C at X(Na2CO3) ≤ 30 mol%. The ternary Na2CO3-FeCO3-MgCO3 system can be built up from the corresponding binary systems: two systems with intermediate Na2(Mg, Fe)(CO3)2 phase, which melts congruently at the Mg-rich side and incongruently at the Fe-rich side, and the (Mg, Fe)CO3 system with complete solid solution. The phase relations suggest that the maximum contribution of FeCO3 component into the lowering solidus temperatures of Na-bearing carbonated mantle domains could not exceed several tens of degrees Celsius.
Original language | English |
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Pages (from-to) | 130-137 |
Number of pages | 8 |
Journal | American Mineralogist |
Volume | 100 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2015 Jan 1 |
Keywords
- Carbonatite
- Eitelite
- High-pressure experiment
- Mantle
- Melting
- Natrite
- Phase relations
- Siderite
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology