Fluids in Metamorphic Rocks

Question 1

What does heating of mixed sediments produce in high and low temps?

Answer 1

Heating of mixed sediments releases methane into at low temps or carbon dioxide at higher temps

Question 2

Is there fluid in the rock at low temps?

Answer 2

At low temperatures there is no fluid and a later brittle deformation event needs to occur
As rock cools, no ductile deformation occurs so there is a lack of high T or fluid so textures are preserved

Question 3

What does metamorphism of carbonates release?

Answer 3

CO2 and generates porosity

Question 4

What effect does water and CO2 have on stability of impure (mixed fluids)?

Answer 4

Increases as reactions can occur over a wider range of temps as:
Water allows reaction to occur at much lower temperatures
Carbon dioxide allows dehydration to occur at lower temperatures

Question 5

What is internal buffering?

Answer 5

Buffering within a mineral

As Xco2 increases temp increases until reactant is made or all of the water is expelled

Question 6

What is external buffering?

Answer 6

Buffering controlled by an external source e.g. nearby vein
Driven by temp increase with composition remaining unchanged as CO2 flushed out or a change in fluid composition such as a new fluid coming in

Question 7

What is internal buffering in a fluid?

Answer 7

Substantial changes in fluid composition drive fluids back and forth across the T-X diagrams
Most reaction occur at either Xco2 = 1 or Xh2o = 1
Xco2 - Decarbonation reation - pure CO2
Xh2o - Dehydration reaction - pure water

Question 8

Where do zones of external buffering and internal buffering occur?

Answer 8

zones of external buffering occur near heterogenousrocks

zones of internal buffering occur near homogenous rocks