2. *
*Metamorphism – A transformation
*Those rocks which undergone various chemical and physical
changes
*They are formed from the parent material protolith
*The protolith may be igneous , sedimentary , metamorphic
*The minerals forming metamorphic rocks due to
metamorphism is called as index minerals
3. *
*Classification based on location of action by agents
*Contact metamorphism – due to magma
*Regional metamorphism –Due to heat and pressure
*Most of the crust rocks are metamorphic
*The metamorphic rocks also form important ores
*It is the evolution of rock to suit the new environment
4.
5. *
*The actions of chemically active fluids, heat, pressure
make the protolith to become destabilize and
converted to metamorphic rocks.
*Each element has own temperature to destabilize.
*Using this property we can find the age of rocks
*During the formation the igneous and sedimentary
rocks get changed in composition, structure etc
*If it occurs due to heat it is called as thermal
metamorphism
*If it is occurring due to both heat and pressure it is
dynamo thermal metamorphism
6. *
*Heat is dominant factor.
*It increase with increase in depth and also the
intruding of magma in the crystal layer of rocks
*A contact metamorphosis
*The gas emissions also reacts with rock and
changes the property
*There is addition of magmatic material
7. *In this case both the heat and the pressure acts.
*Recrystallization of minerals occurs
*Schist and gneiss
*Here whole rock get metamorphosed – a regional
metamorphosis
*Granite to gneiss and on further to schist
*The first conversion due to thermal metamorphism and
second due to dynamo-thermal metamorphism
9. *
*It is the rocks (parallel structures) contain micas and ferro
magnesian minerals
*It has four types
Foliated
Coarse
grained
-schists
Medium
grained
Very
fine
grained
Coarse
grained-
Gneiss
10. *Coarse grained- gneiss –they are formed from
granite and contains quartz, mica, feldspars,
amphiboles
*Coarse grained –schist - they are granite ,basalt
Having mica and silicates
*Medium grained phyllite- from shale –micaceous –
transition of schist to slate
*Very fine grained- shale – micaceous with quartz-
slate
15. *
*They are massive structures with quartz and
feldspars
*Fine grained peat , coal –anthracite ,
Amphibolite
*They won’t create foliation even under
pressure due to large sized particles
16. *
*Formed from eqidimensional grains
*Quartzite from sandstone –medium to coarse
*Marble from dolomite and calcite –fine grained
