1.  Predict the possible reactions from the compositions of the phases in a system.  Unary system: C=1. All phases have same composition  A “point”. Only phase transition is possible  Binary system: C=2. Phases are on a line. 3. Chemography AB 1 23 X

2.  Example: Al2O3-H2O system  Possible phases  Corundum Al2O3 (c)  Diaspoer AlOOH (d)  Gibbsite Al(OH)3 (g)  Water H2O (w) Al2O3H2O c wd g

3.  When F=1, P + 1 = 2 + 2 =3.  Thus, the following univariant reactions and assemblages are possible  d=c+g  d=c+w  g=d+w  g=c+w

4.  Ternary System: C=3, Phases are on a triangle A C B 2 1 3 4 5

5.  When F=1, P=3-1+2=4. Two possible univariant reactions;  Phase elimination reaction: 4=1+2+3  Join-crossing reaction: 1+2=3+4 A C B A C B 4 2 1 3 1 3 4 2

6.  Example: SiO2-CaO-MgO-(H2O-CO2) system  Possible phases  Quartz SiO2 (Qz)  Calcite CaCO3 (Cc)  Dolomite CaMg(CO3)2 (Dm)  Tremolite Ca2Mg5Si8O22(OH)2 (Tr)  Diopside CaMgSi2O6 (Dp)  Forsterite Mg2SiO4 (Fo)  Chondrodite Mg5Si2O8(OH)2 (Cd)  Wollastonite CaSiO3 (Ws)  Magnesite (MgCO3) (Mg) With constant fugacities of H2O and CO2

7. CaO(C)MgO(M) SiO2(S) Cc Dm Mg Ws Qz Dp Tr Fo Cd

8. Metamorphic mineral reactions as a function of T Qz+Dm  Tr+CcQz+Tr+Cc  DpOriginal assemblageCc+Tr  Di+Dm Tr+Dm  Di+FoDi+Dm  Cc+Fo