Deformation and Metamorphism

3. Fluids
Fluids from magma bodies or from groundwater can affect the metamorphic
process to:
i. increase the rate of metamorphic change.
ii.
iii.
4. Time
assist recrystallisation (forming the foliations usually associated with
metamorphic rocks).
cause reactions between the chemicals dissolved in the fluids and the
minerals present, that is chemical metamorphism (= metasomatism)
that increases the likelihood of new minerals forming.
Metamorphic processes are extremely slow. They take many millions of
years.
The table below summarises the factors affecting metamorphic change,
giving the effect/s of each factor.
Factor
Effect/s of this factor
1. Temperature Formation of new minerals.
Recrystallisation.
Change (usually decrease) in water content.
2. Pressure Increase in density.
Formation of platy minerals (i.e. micas).
Foliation - alignment of platy minerals.
Elongation of fossils & pebbles.
3. Fluids Increased rate of metamorphic changes.
Assist recrystallisation.
Cause chemical metamorphism to occur.
4. Time Metamorphic processes require millions of years.
Topics 1.3.3 & 1.3.4 Deformation & Metamorphism Page 10 of 33