Phase Diagrams

Question 1

mission of phase diagrams^

Answer 1

Modelling the melting and crystallisation behaviour of structurally and chemically disimilar minerals

Question 2

Eutetic Systems

Answer 2

congruent melting, melt directly to a liquid of the same compositio

Question 3

Peritectic system:

Answer 3

incongruent melting

Question 4

binary phase diagrams

Answer 4

2 behaviours

Question 5

Eutetic minimum temo point

Answer 5

system is solid

Question 6

bimodal graph close to one side

Answer 6

the first crystal will be that mineral plus water

Question 7

pure end member composition

Answer 7

first solid to form has the pure end-member compostition ( in this case diopside)

Question 8

Event temperature

Answer 8

first temp where one of a bimodal structure forms

Question 9

Eutectic Temperature

Answer 9

when 2 minerals crystalize together until all liquid is consumed
final solid has the eutectic composition

Question 10

Ophitic

Answer 10

texture is large crystals with coarse crystals inbetween, everything coarse crystalline but fabric is coarse cristallization ( esp present in gabbros)

Question 11

disequilibrium crystallisation

Answer 11

results in layering

Question 12

Incompatible

Answer 12

cannot coexist ex. quartz and nephaline would form albite instead

Question 13

Incongruent Melting Phase

Answer 13

system with two endmember phases plus a third phase with an intermediate composition which does not melt into its own composition
ex. leucite, orthoclase, quartz

Question 14

Exsolution

Answer 14

show sub-solidus behaviour, as solid continues to cool ion exchange still occurs and single feldpar umixes to form two feldspars

Question 15

Solvus

Answer 15

only effects minerals in solid state ( metals, alloys), unmixing, requires system to be at that tabel temp for a long time to form textures

Question 16

Exsolution texture

Answer 16

happens in perthite when two feldspars melt together but stay unmixed
´lamellae’ of one felspar with another
shows single feldspar has unmixed to cause a feldspar with 2 textures in it
unmixed texture

Question 17

Ternary Systems

Answer 17

3D model, valley aslow point

Question 18

Gibbs Phase Rule

Answer 18

describe the behaviours of chemical systems in terms of the physical parameters

Question 19

Two component systems demonstrate : complete mixing

Answer 19

solid solution behviouer

Question 20

Two component systems demonstrate : immiscibility

Answer 20

eutectic behaviour

Question 21

Two component systems demonstrate : peritectic

Answer 21

reactions between end members

Question 22

Habit

Answer 22

crystal shape

Question 23

euhedral

Answer 23

perfectly shaped crystal

forms in unrestricted space (often liquid)