Metamorphic Rocks - lec" 7" - Geology for 1th year | Zagazig university. Outlines: _ • Definition. • Features of metamorphism. • Agents / factors of metamorphism. • Types of metamorphism. • Textures of metamorphic Rocks.

1. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 1
Geology
Metamorphic Rocks
____________________
Outlines: _
 Definition.
 Features of metamorphism.
 Agents / factors of metamorphism.
 Types of metamorphism.
 Textures of metamorphic Rocks.
‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
 Definition:
Metamorphism – “a Greek word – Meta = Change,
Morph = Form.So, Metamorphism Means Change in
the Form. “
-= ‫يصبح‬ ‫معناها‬ ‫وبذلك‬ ، ‫شكل‬ : ‫مورف‬ ، ‫تغيير‬ ‫تعنى‬ : ‫ميتا‬
. ‫الشكل‬ ‫فى‬ ‫التغيير‬

2. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 2
Metamorphism : it’s recrystallization of pre-existing
rock under the effect of temperature , pressure or
chemically active fluids .
-‫الحرارة‬ ‫تأثير‬ ‫تحت‬ ‫سابقا‬ ‫موجود‬ ‫صخر‬ ‫من‬ ‫صخر‬ ‫تكوين‬ ‫إعادة‬
. ‫الكيميائيه‬ ‫العوامل‬ ‫او‬ ‫والضغط‬
_____________________
 Features of Metamorphism
1 – Metamorphism take place in the solid state
before melting.
2 – It can be considered to be iso-chemical except
for addition or removal of volatiles “ like water “
Or
It may cause extensive or strong change in
chemistry , So it’s called “ metasomatism “.

3. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 3
-‫؟‬ ‫دا‬ ‫الكالم‬ ‫ايه‬ ‫يعنى‬
. ‫التحول‬ ‫خصائص‬ ‫او‬ ‫مالمح‬
1-‫فى‬ ‫يحدث‬ ‫ال‬ " . ‫االنصهار‬ ‫قبل‬ ‫الصلبه‬ ‫الحاله‬ ‫فى‬ ‫يحدث‬
" ‫االنصهار‬
2–‫ايزو‬ " ‫هو‬ ‫لذلك‬ ‫الكيميائيه‬ ‫العناصر‬ ‫تغييرفى‬ ‫او‬ ‫تبادل‬ ‫يحدث‬ ‫ال‬
" ‫كيميائى‬–. ‫الماء‬ ‫مثل‬ ‫المتطايرة‬ ‫المواد‬ ‫بعض‬ ‫اضافة‬ ‫باستثناء‬
‫بفعل‬ ‫للصخر‬ ‫الكيميائي‬ ‫التركيب‬ ‫فى‬ ‫شديد‬ ‫تبادل‬ ‫حدث‬ ‫إذا‬ ‫آخر‬ ‫بمعنى‬
" ‫وليس‬ " ‫ميتاسوماتيزم‬ " ‫النوع‬ ‫هذا‬ ‫يسمى‬ ، ‫الكيميائيه‬ ‫العوامل‬
" ‫ميتامورفيزم‬
Metasomatism:
change in the composition of a rock as a result of the
introduction or removal of chemical constituents.

4. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 4
 Agents of Metamorphism .
1- Temperature.
2- Pressure.
3- Chemically active fluid.
_______________________
1- Temperature.
= Sources :-
a)Rising of magma bodies.
b)Geothermal Gradient.
c) Heat flow of mantle.
d)Rapid uplifting and erosion.
e)Radioactive Decay.
-: ‫الحراره‬ ‫مصدر‬
a).‫الصهارة‬ ‫المادة‬ ‫صعود‬
b)‫بمعدل‬ ، ‫الحرارة‬ ‫زادت‬ ‫العمق‬ ‫زاد‬ ‫كلما‬ : ‫الحرارى‬ ‫التدرج‬
30‫درجه‬. ‫متر‬ ‫كيلو‬ ‫لكل‬ . ‫س‬
c). ‫الوشاح‬ ‫من‬ ‫المتدفقة‬ ‫الحرارة‬

5. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 5
d). ‫التآكل‬ ‫و‬ ‫السريعه‬ ‫الرفع‬ ‫عمليات‬
e).‫االشعاعى‬ " ‫االضمحالل‬ ‫او‬ ‫االنحالل‬ " ‫التحلل‬
: ‫الحظ‬
- Limits of temperatures
 lower limit (150±50 °C)
 higher limit (beginning of melting, 650-1100
°C)
‫ــــــــــــــــــــــــــــــــــــــــــ‬
2- Pressure : is define as force/unit area.
=Source :
a)Geogabric gradient : increase the pressure by
increasing depth “ 1k.bar / 3 Km “
b)Lithostatic Pressure : this pressure is uniform
in all directions by equal stresses acting on a
rock . – it doesn’t cause deformation.
c) Plate tectonic movement.

6. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 6
_________________
3- Fluids :
a)Spaces,pores and cracks are filled with
fluids.
b)Fluids make metamorphism more easily.
c) Fluids increase the rate if chemical reaction.
___________________________________________
 Types of metamorphism:
They are related to agents of metamorphism which
are dominated, Predominant.
a)Dynamic Metamorphism = Cataclastic.
b)Thermal / Contact Metamorphism.
c) Regional Metamorphism.

7. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 7
Dynamic Metamorphism = Cataclastic.
- Pressure is the predominant agent.
- Produced from directive stress, occurs along the
fault zones or fault planes.
- This type cause crashing and granulation.
- EX : Mylonite.
Thermal / Contact Metamorphism.
Temperature is the main agent
Form as concentric zones (aureole) around hot
Igneous intrusive body . EX. Quartzite, Marble.
 Textures of rocks that affected by contact
metamorphism known by:
- Overgrowth in crystals.
- Has no preferred orientation.

8. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 8
Regional Metamorphism.
Takes place in a very large area, related to high
temperature and pressure.
- Low grade of metamorphism. EX: slate .
- Medium: ex. Schist , Phyllite.
- High : ex. Gneiss,Migmatite.
____________________________________________
Textures of Metamorphic rocks :
1- Foliated
Rock has preferred orientation. due to effect of
pressure.
2- Non Foliated
Called Mosaic,Granoplastic or polygonal.

9. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 9
Foliated Metamorphic Rocks
• Slate
Dull, microscopic grains (could not seen by 10 x
lense), strong slaty cleavage, silky appearnce,
mudstone protolith
• Phyllite
Shiny, strongly micaceous with microscopic
grains (could seen by 10 x lense), strong
schistosity, cleavage, can be mafic or felsic, any
rock-type protolith.
Non-foliated Metamorphic rocks
Quartzite
• Metamorphosed sandstone
• Coarser and harder than the original
sandstones

10. Geology_______________________________________________________Metamorphic Rocks
Ahmed Al-kawaliny_ Senior Geologist at Zag Univ.
Head of SOBS ZAG Team.
Page | 10
• Harder than marble
• Will not release CO2 in the presence of acid
Marble
• Metamorphosed limestone “ calcite”
• Harder and coarser than the original
limestone
• Contains calcium carbonate
• Will release CO2 in the presence of acid
• Softer than quartzite