Melting and subsolidus phase relations in the system K2CO3–MgCO3 at 3 GPa

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Abstract

As part of an investigation of carbonate systems under mantle pressures and temperatures, phase relations in the K2CO3–MgCO3 system have been studied at 3 GPa and 800–1300°C. Subsolidus assemblages comprise the stability fields of K2CO3 + K2Mg(CO3)2 and K2Mg(CO3)2 + MgCO3 with the transition boundary near 50 mol% K2CO3 in the system. The K2CO3–K2Mg(CO3)2 eutectic is located at 840°C and 52 mol% K2CO3. The K2CO3 content in the melt coexisting with potassium carbonate increases to 85 mol% as temperature increases to 1050°C. K2CO3 remains solid up to 1250 and melts at 1300°C. K2Mg(CO3)2 melts incongruently at 890°C to produce magnesite and a liquid containing 51 mol% K2CO3. As temperature increases to 1300°C, the K2CO3 content in the liquid coexisting with magnesite decreases to 27 mol%.

Original languageEnglish
Pages (from-to)422-439
Number of pages18
JournalHigh Pressure Research
Volume38
Issue number4
DOIs
Publication statusPublished - 2 Oct 2018

Keywords

  • carbonatite
  • KCO–MgCO
  • KMg(CO)
  • Raman
  • shallow mantle
  • K2Mg(CO3)(2)
  • HIGH-PRESSURE
  • LITHOSPHERIC MANTLE
  • 6 GPA
  • CRYSTAL-STRUCTURE
  • GARNET LHERZOLITE
  • CARBONATITE METASOMATISM
  • POTASSIUM CARBONATE
  • MODEL LHERZOLITE
  • K2CO3-MgCO3
  • FUSION CURVE
  • FIBROUS DIAMONDS

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