Metamorphic rocks on the basis of mineral identification

2. Geo Chemistry
Introduction to Geo Chemistry of
Metamorphic Rock

3. Presented by
Muhammad Ishfaq Khosa
Roll no. 220
Session 2013-2017
University of Azad Jammu & Kashmir
Muzaffarbad

5. Metamorphic Rock
• Metamorphic Rocks are formed from
Sedimentary, Igneous and Metamorphic
rocks through metamorphism processes
deep under the Earth Crust
• It formed due to Temperature, Pressure
and chemical Processes.

6. Types of Metamorphism
• There are two types of
metamorphism
1)Contact Metamorphism
2)Regional Metamorphism

7. 1. Contact Metamorphism
• Contact metamorphism is a type of metamorphism
where rock minerals and texture are changed,
mainly by heat.
• The Confining Pressure is relatively low
• It is less than 10 km
• The zone is 1-100 m wide
• Non Foliated Rocks are formed due to Contact
metamorphism

8. Contact Metamorphism
• It is formed when magma pushed the
existing rocks
• Changes the structure and mineral
composition of the surrounding rocks

9. Contact metamorphism
Folding Minerals

10. 2. Regional Metamorphism
• Regional metamorphism is a type of
metamorphism where rock minerals and
texture are changed by heat and pressure
over a wide area.
• It takes place at depth greater than 5 km
• Foliated Metamorphic Rocks are formed
due to Regional Metamorphism.

12. Classification of rocks
• Rocks can be classified in two different
types based on the texture
i. Foliated rocks
ii.Non foliated rocks

13. Non Foliated Metamorphic Rocks
• These Rocks are formed due to Contact
Metamorphism
• Metamorphic Rocks does not foliation.
• Examples of Metamorphic Rocks are
• Marble, Quartzite and Hornfels etc.

14. Foliated Metamorphic Rocks
• These Rocks are formed due to Regional
Metamorphism.
• Foliated Metamorphic Rocks are visible
layers or bands are formed due to
perpendicular Pressures.
• Examples are Slate, Phyllite, Schist,
Gneiss etc.

16. Non Foliated Rocks
• Marble
• Quartzite
• Hornfels

17. Marble
• Marble is the coarse grained rock
composed of interlocking calcite crystals
forms when limestone recrystallizes during
metamorphism if the parent rock is the
dolomite the recrystal rock is the dolomitic
marble
• Marble is however highly susceptible to
chemical weathering

18. Chemistry of Marble
• Metamorphic rock containing more than
50% vol. of calcite and/or dolomite and/or
aragonite.
• Pure marble contains more than 95%
vol.of these carbonate minerals, whereas
the remainder are classified as impure
marble.

19. Marble
Hunza marble
Low grade marble

20. Quartzite
• Is produce when grains of quartz in
sandstone are welded tighter while the
rock is subjected to high temperature. This
makes it as difficult to break along grain
boundaries as through the grains.
Therefore quartzite, being as hard as
single quartz crystals is difficult to break

21. Quartzite
Chita Bata quartzite Quartzite

22. Hornfels
• Hornfels is a very fine-grained non foliated,
metamorphic rock whose parent rock is either shale
or basalt.
• If it forms from shale only microscopically visible
micas form from the shale’s clay minerals.
• If Hornfels form from basalt, amphibole, rather than
mica , is the predominant fine-grained mineral
produces.

23. Foliated Rocks
• Slate
• Phyllite
• Schist
• Gneiss

24. Slate
• Slate is a very fine grained rock that break easy
along the flat, parallel planes.
• Some slate forms from the volcanic ash, parent
rock is shale
• The individual grains are too small to be seen by
the unaided eye (<0.1 mm) and in which the
schistosity is developed on the grain scale.
• Slate is usually of very low metamorphic grade
and rich in phyllosilicates

25. Slate
Hazara Slate Kilk Slate

26. Phyllite
• Metamorphic rock, in which the individual
grains are large enough to be seen by the
unaided eye (>0.1mm)
• characterized by a lustreous sheen and a
well developed schistosity resulting from
the parallel arrangement of phyllosilicates.
• Phyllite is usually of low metamorphic
grade

27. Phyllite

28. Schist
• A schist is characterized by megascopically visible.
• Parallel oriented minerals
• Platy or elongated minerals that crystalize from the
parent rock are clearly visible to the naked eye
• Two, of several, schist that form from shale that are
the mica schist and garnet mica schist
• Mica schist and garnet mica schist are formed from
the same parent rock

29. Schist
• If the parent rock is basalt, the schist are
the Amphibole schist
• If the ferromagnesian mineral that form
during the metamorphism of the basalt is
formed amphibole
• If the predominant mineral is chlorite,
green micaceous mineral is chlorite schist

31. Schist
Talc schist Garnet schist

32. Schist
Chlorite Schist Amphibolite Schist

33. Schist
Graphite Schist Starolite Schist

34. Gneiss
• Gneiss is a rock consisting of light and
dark minerals layers or lenses.
• Due to temperature and pressure changed
in the rock then mineral have separated in
to the layers
• Platy or elongated minerals(mica or
amphibole) in dark layers
• Coarse feldspar and quartz are light
colored layers

35. Gneiss
gneiss Maylonite Gneiss

36. Amphibolite
• Amphibolite is metamorphic rock mainly (to
more than 50% vol.) consisting of green, brown,
or black amphibole and plagioclase.
• The modal content of pyroxene is larger than
30% vol. and larger than the percentage of any
one of the other mafic minerals. Plagioclase is a
major mineral (>5%vol.).

37. Other common minerals in amphibolite are quartz, chlorite,
epidote, zoisite, biotite, garnet, titanite, scapolite, and
calcite.
Their presence should be indicated by prefixing them, e.g.,
garnet bearing clinopyroxene amphibolite, where garnet is
a minor and clinopyroxene a major constituent.
Only in the case of the special type of amphibole or
plagioclase being present, these constituents should be
prefixed as well (e.g., bytownite amphibolite

38. Amphibolite
Kamila Amphibolite Epidote

39. Eclogite
• Eclogite is Plagioclase free metamorphic
rock composed of more than 75%
omphacite and garnet, both of which are
present as major minerals