Phase Petrology 2 & 3

Question 1

What happens in equlibrium crystallisazion?

Answer 1

The bulk composition of the liquid ends with the same proportion as the total solid composition

Question 2

What does BC, LC and TSC mean?

Answer 2

BC = Bulk Composition
LC= Liquid Composition
TSC= Total solid composition

Question 3

What does ISC mean?

Answer 3

Instantaneous solid composition

This is when fractionalized crystallization happens and a solid composition is formed, minerals are removed from the melt

Question 4

Rules of crystallization

Answer 4

1) LC always moves radially away from ISC
2) TSC always moves towards the ISC
3) LC-BC-TSC are always colinear
4) Lever rule

Question 5

Cotectic

Answer 5

“Co-crystallization” of two phases from the liquid (Univariant)

Question 6

Ternary eutectics

Answer 6

“Co-crystallization” of three phases from the liquid (Invariant)

Question 7

Gibbs Phase Rule

Answer 7

F=C+2-φ
F: Degrees of freedom
C: Components
φ: Equilibrium phases at a given O and T

Question 8

Degrees of freedom

Answer 8

The number of system properties must be fixed to know all system (Phase) properties at eq.

Question 9

What are the different degrees of freedom called?

Answer 9

F=2 : Divariant
F=1 : Univariant
F=0 : Invariant

Question 10

Freezing point depression

Answer 10

T (Mixture) decreases with the addition of a new component to the liquid