Contact metamorphism

1
Contact metamorphism fluids
2

• Can fluid composition change during met?

3
Fluid composition

• It can change composition during metamorphism
• Internally buffered
• Fluids evolved stay in system
• Top reaction, when do you leave the reaction line?

4

• What if an open system?
• Infiltrated by external fluids
• What is fluid composition here?

5
Paths of buffered or open system fluidsalso note
pressure changes
6
Calc-silicates

• Marbles pure carbonate
• Calc-silicates carbonate with silicates
• Skarn calc-silicate formed by metasomatism

7
What are index minerals for calc-silicates?
8
Intrusion
1/2 Km
9
Intrusion
1/2 Km
10
Intrusion
Tremolite Talc
1/2 Km
11
Intrusion
Forsterite Tremolite Talc
1/2 Km
12
Intrusion
PericlaseFo Forsterite Tremolite Talc
1/2 Km
13
Intrusion
PericlaseFo Forsterite Tremolite Talc
1/2 Km
14
Index minerals in calc-silicates

• Talc
• Tremolite
• /- diopside
• Forsterite
• Periclase
• Monticellite

15
Ubehebe contact aureole

• No talc zone, why?

16

• Index minerals for Ubehebe Peak

17

• Tremolite blossoms in silicious dolostone
• Fluid along cracks, not pervasive

18

• More evidence for localize fluid flow
• Periclase zone

19

• What sequence of index minerals if externally
  buffered fluid
• XCO2 0.5
• XCO2 0.05
• XCO2 0.9

20

• What sequence of index minerals if low quartz
  content in protolith?
• Which reactions?
• Protolith dolomite, calcite, some quartz
• XCO2 lt 0.6

21

• In what kind of protolith can you find
  wollastonite?

22
Plutons in NE Utah
23
Alta stock contact aureole
31 Ma
24
Alta Contact Aureole at Albion Basin
Index Minerals
25
(No Transcript)