Metamorphic Rocks

1. What are Metamorphic
Rocks ?
Metamorphic rocks started out as some
other type of rock , but have been
substantially changed from their original
igneous , sedimentary, or earlier
metamorphic form.

2. Metamorphic rocks form when rocks are
subjected to high heat , high pressure , hot
mineral - rich fluids, or more commonly ,
some combination of these factors.
Conditions like these are found deep within
the earth or where tectonic plates
meet .
Process of
Metamorphism :
The process of metamorphism does not melt
the rocks , but instead transforms them into
denser , more compact rock . New minerals
are created either by rearrangement of
mineral component or by

3. reactions with fluids that enter the rocks .
Pressure or temperature can even change
previously metamorphosed rocks into new
types .
Metamorphic rocks are often squished ,
smeared out , and folded.
Despite these uncomfortable conditions ,
metamorphic rocks do not get hot enough to
melt,or they would become igneous rocks!

4. The Rock Cycle

5. Metamorphic rocks make up a large part of
the earth's crust and form 12% of the
earth's land surface.
They are classified by their protolieth, their
chemical and mineral makeup, and their
texture.
They may be formed simply by being deeply
buried beneath the earth's surface , where
they are subject to high temperature and
the great pressure of the rock layers above .
They can also form from tectonic processes
such as continental collisions , which cause
horizontal pressure , friction , and
distortion.
Metamorphic rock can be formed locally
when rock called magma from the earth's
interior .

6. The study of metamorphic rocks ( now
i'urmafion of .llclaniorplm*
Itork
exposed at the earth's surface following
erosion and uplift ) provide information
about the temperatures and pressures that
occur at great depths within the earth's
crust .
Origin
Metamorphic rocks form one of the three great
division of rock types .
They are distinguished from igneous rocks , which

7. form from molten magma , and sedimentary rocks ,
which form from sediments eroded from exiting rock
or precipitated chemically from bodies of water .
Metamorphic rocks are formed when existing rock is
transformed physically or chemically at elevated
temperature , without actually melting to any great
degree .
The importance of heating in the formation of
metamorphic rock was first noted by the pioneering
Scottish naturalist , James Hutton, who is often
described as the father of modern geology .

8. Why we study metamorphic rock?
• Studies of metamorphic rocks provide
insights into the physical and chemical
changes that take place deep within Earth
.
• Knowledge of metamorphic processes
and rocks is valuable , because
metamorphic minerals and rocks have
economic value .
For example , slate and marble are building
materials .
• Metamorphic rocks are some of the
oldest on earth , are widely exposed in the
core areas , known as “ Shields “ of
continents .

9. mtrud«j
magma
Dodv
Agents of metamorphism
These are three main sources of chemically
active fluids :
1- Pore waters of sedimentary rocks
2- Fluids from cooling magma
3- Water from dehydration of water - bearing
minerals like gypsum .

10. Recourses
• An introduction to igneous and
metamorphic petrology
• The tectonic evolution of the
Himalaya and Tibt.