4 Metamorphic Reactions.ppt
- 3. Solid-Solid Net Transfer Reaction NaAlSi2O6 + SiO2 = NaAlSi3O8 Jd Qtz Ab dG = VdP – SdT dP = S dT = V Clapyron Equation
- 4. Dehydration Reaction KAl3Si3O10(OH)2 + SiO2 = KAlSi3O8 + Al2SiO5 + H2O Ms Qtz Kfs Als Slope of reaction boundary determined by properties of fluid phase dP = S dT = V Most dehydration reaction boundaries subparallel
- 5. Decarbonation Reactions CaCO3 + SiO2 = CaSiO3 + CO2 Parallelism of decarbonation reaction equilibrium boundaries in P-T space
- 6. Decarbonation Versus Dehydration Reactions
- 7. Theoretical Loop of Devolatilization Reactions At high enough pressures the fluid phase is so compressed that VProducts < VReactants dP = S dT = V Clapyron equation becomes negative
- 8. Dehydration Reaction: Effect of PH2O < PTotal Ln K = Ln f H2O ( f H2O = PH2O H2O) Le Chatelier’s principle; lowering PH2O stabilizes products at the expense of reactants, displacing equilibrium boundary to lower temperature
- 9. Temperature vs Mole Fraction of Fluid Species T-XH2O Diagram T-XCO2 Diagram XCO2 + XH2O = 1
- 10. G T G T K A S G T A K S K S A T P3 P2 P1 P3 P2 P1 T (K) (A) (S) Energy-Temperature Diagrams: the Rules of Schreinemakers P1 P3 P2
- 11. Rules of Schreinemakers 1. Label each reaction with the missing phase 2. Arrange reactions such that the label is stable where the reaction is metastable
- 12. Application of Rules of Schreinemakers to 2-component system with 4 phases Note that there is one reaction for each phase in the system
- 13. Application of Rules of Schreinemakers to 2-Component System with 5 phases
- 14. An Example of a Petrogenetic Grid – the KMASH System for Pelites