1. Liquid Immiscibility in the Join NaAlSi3O8-CaCO3 to 2
Liquid Immiscibility in the Join NaAlSi3O8-CaCO3 to 2.5 GPa and the Origin of Calciocarbonatite Magmas W.J. Lee and P.J. Wyllie Presented by RD Bartman

2. What is a Carbonatite? Alkaline Intrusive/extrusive igneous rocks
>20% volume carbonates
Dykes, sills, breccia, plugs, veins
Continental rift related settings
Proterozoic/Phanerozoic
Carbonate lava flows – unstable
Ol Doinyo Lengai – erupt, lowest T lava

3. How does it form? Magmatic or Metasomatic origin
Fractional crystallization
REE

4. Experiments & Samples

5. Isobaric phase fields intersected by the join albite-calcite at 2.5GPa

6. Silicate-Carbonate liquid miscibility gaps projected onto the CO2-saturated, Hamilton projection. The tie line, C‘, connects coexisting silicate-rich liquid and carbonate-rich liquid. Results are seen at A, B and C. The size of the miscibilty gap increases with pressure. Liquid miscibily = calcite liquidus divides into Lc and Ls.

7. Petrogenesis
Petrology allows development by fractional crystallization
SiO2 and Carbonate magma
Liquid immiscibility of a silica magma
Partial melting
Metasomatism

8. Other carbonatite occurences
Brazil
Italy
Telemark, Norway
Gardar Province, SW Greenland
Ol Doinyo Lengai, Tanzania
Barberton Greenstone Belt
Loolekop, Phalaborwa
Salpeterkop Complex, Sutherland
Bulhoek Complex, NW province

9. 2 Questions to be debated - liquidus paths to calciocarbonatite magmas
Conclusion
2 Questions to be debated - liquidus paths to calciocarbonatite magmas
Do calciocarbonatite magmas, which are extremely CaCO3 enriched, exist?
If so, how are they derived from the parent rocks or parent magmas?
2 Theories

10. References The Paper Wikipedia
Turner and Verhoogen; Igneous and Metamorphic Petrology, 2nd Edition; Mcgraw Hill Book Company Inc.; pp
Carmicheal, Turner, Verhoogen; Igneous and Metamorphic Petrology; Mcgraw Hill Book Company; pp
Bell, Kjarsgaard, Simonetti; Carbonatites into the 21st Century; Journal of Petrology; pp
J. Gittins, and R. E. Harmer; Dawson's Oldoinyo Lengai calciocarbonatite; a magmatic sovite or an extremely altered natrocarbonatite?; South African Journal of Geology. 1999; pp