The document discusses metamorphism, which is the transformation of rocks due to changes in chemical and physical conditions. Metamorphic rocks form from the alteration of pre-existing igneous, sedimentary, or other metamorphic rocks (called protoliths) due to heat, pressure, and chemically active fluids. Metamorphism can be divided into contact metamorphism near magma intrusions and regional metamorphism caused by heat and pressure at depth over large areas. The degree and type of metamorphism determines the texture and mineral composition of the resulting rock.

1. -J.Delince
BSA-11-409

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*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

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*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

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*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

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*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

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Metamorphic
rocks
Foliated Non-foliated Granular

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*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

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*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

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*Formed from eqidimensional grains
*Quartzite from sandstone –medium to coarse
*Marble from dolomite and calcite –fine grained

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*A text book of pedology- J.Sehgal
*www.geology.com/rocks/metamorphic
rocks.html

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