Download 5 - جامعة بنها

)2011 – 2010( ‫الفصل الدراسي الثاني‬
Basement rocks ‫ صخور قاع‬:‫المادة‬
"‫كيمياء‬-‫ ثالثة علوم "جيولوجيا‬:‫الفرقة‬
‫جامعة بنها‬
‫كلية العلوم‬
‫قسم الجيولوجيا‬
"‫كيمياء‬-‫االجابة النموذجية المتحان مادة القاعية للفرقة الثالثة "جيولوجيا‬
)‫(ورقة امتحانية كاملة‬
2011-6-25 :‫تاريخ االمتحان‬
‫ عبدالعظيم أحمد رشوان‬/.‫ د‬:‫اسم الممتحن‬
‫استاذ الجيولوجيا المساعد بقسم الجيولوجيا – كلية العلوم – جامعة بنها‬
1- a. the magmatism in Egypt during the Phanerozoic include the
following rock group:
1- Basalts.
2- Wadi Natash volcanic
3- Post-granitic dykes
4- Ring complexes.
b. The characters of the Egyptian ring complexes are:
1- They intruded within the Pan-African rocks.
2- They consist mainly of different varieties of granites and syenites,
nephline syenites, gabbros and equivalent volcanic, all arranged in
concentric fashion.
3- They are circular or elliptical in plan, few kilometers diameter.
4- All occurring in the ED south Lat. 25o N, with the exception of
Wadi Dip ring complex in the NED.
5- They include complete ring complex, incomplete or crecent-shape.
6- Their compositions ranging basic, intermediate and acidic
alkaline.
2- The characters of G2 granites are:
1- All are calc-alkaline in nature.
2- They were formed under environment of compression.
3- They are usually formed small plutons.
4- biotite is always dominant over Hornblende, muscovite is
present.
5- Ilmenite is the iron oxide.
6- SiO2 content is more than 65 %, Na2O content is less than 3.2
%.
7- Nb content is from 40 – 50 ppm.
8- The radioactive minerals are high.
9- Low REE.
3- a. A complete ophioltic sections is composed of the following
units:
Top
V- Pelagic sediments
IV- Pillow basalt.
III- Sheeted dykes complex.
II- Cumulate gabbros, massive gabbros.
I- Peridotite.
Bottom.
b. Wadi Gadir ophiolite.
The ophiolitic sequence of Wadi Gadir consists from below to
upwards of:
1234-
The serpentinized peridotites.
The gabbro complex.
The sheeted dykes.
The Pillow basalts
4- The features of the Essexite gabbros are characterized by:
1- These gabbros pertaining to ring complexes.
2- They form small bodies of alkaline gabbros.
3- These rocks show ophitic textures and composed essentially of
plagioclase, titanoaugite, biotite, alkali amphibole and little
orthoclase.
4- The age recorded for these rocks that were formed from Upper
Paleozoic to Upper Cretaceous.
5- The following age succession of units of the Migif-Hafafit with the
youngest on the top:
-
Gneissic tonalite.
Intrusive calc-alkaline metagabbros.
Psammitic gneisses
Biotite shists
Foliated metagabbros.
Ultramafic rocks.