Metamorphic Rocks - lec" 7" - Geology for 1th year | Zagazig university.
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