Thermodynamic analysis of stability of secondary minerals in altered carbonatites of the Oldoinyo Lengai volcano, Northern Tanzania

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1 Scopus citations

Abstract

Carbonatites from the Oldoinyo Lengai volcano, northern Tanzania, are unstable under normal atmospheric conditions. During carbonatite interaction with water the major minerals gregoryite Na 2 (CO 3 ), nyerereite Na 2 Ca(CO 3 )2 and sylvite KCl are dissolved and replaced by secondary low-temperature minerals thermonatrite Na 2 (CO 3 )·H 2 O, trona Na3(CO 3 )(HCO 3 )·2H 2 O, nahcolite Na(HCO 3 ), pirssonite Na 2 Ca(CO 3 )2 ·2H 2 O, calcite Ca(CO 3 ) and shortite Na 2 Ca 2 (CO 3 )3. Thermodynamic calculations show that the formation of secondary minerals within Oldoinyo Lengai carbonatites are controlled by pH of pore solution, H 2 O and CO 2 fugacity and the ratio of Ca and Na activities in the system Na 2 O-CaO-CO 2 -H 2 O.

Original languageEnglish
Pages (from-to)1-13
Number of pages13
JournalZapiski Rossiiskogo Mineralogicheskogo Obshchestva
Volume145
Issue number3
StatePublished - 1 Jan 2016

Scopus subject areas

  • Geochemistry and Petrology
  • Geology
  • Economic Geology
  • Materials Chemistry

Keywords

  • Calcite
  • Carbonatites
  • Gregoryite
  • Low-temperature alteration
  • Nyerereite
  • Oldoinyo Lengai volcano
  • Pirssonite

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