Metamorphic Reactions
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Transcript of Metamorphic Reactions
Metamorphic Reactions
Phase Transformation Reactions
Solid-Solid Net Transfer Reaction
NaAlSiNaAlSi22OO66 + SiO + SiO22 = NaAlSi = NaAlSi33OO88 JdJd Qtz Qtz AbAb
dG = VdP – SdT
dP = S
dT = V
Clapyron Equation
Dehydration Reaction
KAl3Si3O10(OH)2 + SiO2 = KAlSi3O8 + Al2SiO5 + H2OMs Qtz Kfs Als
Slope of reaction boundary determined by properties of fluid phase
dP = S
dT = V
Most dehydration reaction boundaries subparallel
Decarbonation Reactions
CaCO3 + SiO2 = CaSiO3 + CO2
Parallelism of decarbonation reaction equilibrium boundaries in P-T space
Decarbonation Versus Dehydration Reactions
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
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
Temperature vs Mole Fraction of Fluid Species
T-XH2O Diagram
T-XCO2 DiagramXCO2 + XH2O = 1
G
T
G
T
K
AS
G
T
AK
S
K
SA
T
P3
P2
P1
P3
P2
P1
T
(K)
(A)
(S)
Energy-Temperature Diagrams: the Rules of Schreinemakers
P1
P3
P2
Rules of Schreinemakers
1. Label each reaction with the missing phase2. Arrange reactions such that the label is
stable where the reaction is metastable
Application of Rules of Schreinemakers to2-component system with 4 phasesNote that there is one reaction for each phase in the system
Application of Rules of Schreinemakers to 2-Component System with 5 phases
An Example of a Petrogenetic Grid – the KMASH System for Pelites