METAMORPHIC PETROLOGY (PHASE RULE) Flashcards
a means by which petrologists predict equilibrium assemblages of minerals in many systems including ign and met
Phase Rule
Phase Rule Formular
P=C+2-F
What do P, C and F stands for?
P = Phase
C = Components
F = Degrees of Freedom or Variance
A visual means by which mineral stability fields can be displayed
Phase Diagram
If F=2 the system is said to be?
Divariant, there are two factors (Tand P) which can vary independently of one another while the system without changing the phase composition of the system
If F=1 the system is said to be?
Univariant, an indipendaent change in either the T and P requires a chane in the other dependent variable in order to regain equlibrium
In a one component system univariant line indicates:
Boundaries between divariant fields
conditions at which two phases can coexist
condition across which change in equilibrium mineran assemblages occur
If F=0 the system is said to be?
Invariant, only at a certain fixed tem and pressure can all the phases coexist
In Aluminosilicates what is the T and P of the invariant point
T: 510 deg cel P: 3.8Kbar
A invariant point indicates
a point where the three univariant line intersects
a specific temp and pressure conditions at which three stable phases coexist in a one component system
An equlibirium mineral reaction and assemblage diagram
Petrogenetic or Paragenetic Grid
Refers to the conditions under which the rock originated
Petrogenetic
Refers to the formation sequence of an equilibrium set of minerals that formed at different times
Para genetic
Ternary Diagrams in Met rocks can depict
1) Stable Mineral Assemblages that exist under specific T and P conditions
2) How mineral assemblages change in response to changes in temp and pressure
A ternary diagram created by Eskila based on the morelcular amounts of oxides and can be used to depict average compositional differences between the five major compostional groups of met rocks
ACF Ternary Diagram
