Phase Diagrams Continued

1. Anorthite n Liquid 2000 o p Two Liquids 1800 1713 T oC 1695 Liquid + Forsterite M Cristobalite + Liquid 1600 1557 1543 T c Enstatite + Cristobalite Forsterite 1470 + Enstatite Enstatite + Tridymite 1400 20 60 SiO2 80 40 Forsterite Mg2SiO4 MgSiO2 Wt.% X2 Phase Diagrams Continued

2. Updates/questions • Next week Review and Midterm • Topics: phase diagrams • 2 component systems: • Peritectic • 3 component systems

3. Solid Solution with Eutectic:Ab-Or (the alkali feldspars) Figure 6-16. T-X phase diagram of the system albite-orthoclase at 0.2 GPa H2O pressure. After Bowen and Tuttle (1950). J. Geology.

5. Effect of PH O on Ab-Or 2 Figure 6-17. The Albite-K-feldspar system at various H2O pressures. (a) and (b) after Bowen and Tuttle (1950), J. Geol, (c) after Morse (1970) J. Petrol.

6. Liquid 2000 a Two Liquids 1800 1713 T oC 1695 Liquid + b Forsterite Cristobalite + Liquid 1600 1557 e 1543 Enstatite + Cristobalite Forsterite 1470 + Enstatite Enstatite + Tridymite 1400 20 60 SiO2 80 40 Mg2SiO4 MgSiO2 Wt.% X2 Forsterite Enstatite Binary Peritectic Systems Figure 6-12. Isobaric T-X phase diagram of the system Fo-Silica at 0.1 MPa. After Bowen and Anderson (1914) and Grieg (1927). Amer. J. Sci.

7. i m k 1557 d c Fo En The Peritectic 1: X between Fo-En Bulk X

9. x i k y m 1543 1557 d Cr c bulk X Fo En The Peritectic 2: X between En-Cr

10. i 1543 1557 d Cr c bulk X Fo En • Incongruent Melting of Enstatite

14. Ternary Systems

15. C = 3: Ternary Systems:Example 1: Ternary EutecticDi - An - Fo Anorthite M T Forsterite Diopside

16. Crystallization Relationships

17. a Liquid An Fo + Liq Di + Liq Di + Fo Pure Fo forms Just as in binary f = ? F = ?

19. Ternary lever w/ 3 phases • Imagine triangular plane X - Di - Fo balanced on bulk a Liq x a Di m Fo Liq/total solids = a-m/Liq-a total Di/Fo = m-Fo/Di-m

20. Pressure Effects