Lecture ONE
Introduction
Introduction
The composition of the Earth:
-Lithosphere (5-70 km, solid and
rocky, 5 km thick under the oceans
and up to 70 km thick under the
continents). It composes of:
- sedimentary cover (10 km)
-Sial (granitic in composition)
-Sima (basaltic in composition)
-Mantle Asthenosphere (250 km
thick, molten rocks, 780 °C)
-Mantle Mesosphere (2550 km thick,
Si, O, Fe, Mg)
-Outer core (2200 km thick, Thick
liquid, Fe, Ni)
-Inner Core (1228 km thick, Solid,
Fe and Ni)
Rock cycle
Rocks
Rocks are defined as a component of the Earth’s crust, composed of one
or more minerals with geologic extension
Rocks are classified into:
- Primary
- Igneous rocks
- Secondary
- Sedimentary rocks
- Metamorphic rocks
-The metamorphic rocks are secondary rocks formed from preexisting igneous, sedimentary, and/or prior metamorphic rocks, which are
subjected to physicochemical conditions (P, T, and chemical active fluids)
higher than that at the earth’s surface. The yielded metamorphic rocks differ
than the original ones in mineralogy, structure (textures), and/or chemical
composition. Note: Metamorphism should be occur in solid state.
-Due to higher P-T conditions, metamorphic rocks undergo partial melting
and a hybrid rock between igneous and metamorphic, know as
migmatites, could form.
Continental drift
Plate boundaries
Plate boundaries
Plate Motions
Types of the Plate motion
Plate boundaries includes:
i- Divergent plate boundaries ():
- Formation of the Red Sea and Atlantic Ocean
Ii- Convergent plate boundaries ()
-Oceanic-continental convergence (Oceanic Nazka – S
American plate)
- Oceanic-oceanic convergence (Pacific plate – Philippine
plate)
-Continental-continental convergence (Indian plateEurasian plate)
iii- Transform or shear plate boundaries:
- The San Andreas fault zone, and Gulf of Aqaba fault
i- Divergent plate boundaries
i- Divergent plate boundaries, Cont.
i- Divergent plate boundaries, Cont.
ii- Convergent plate boundaries
ii- Convergent plate boundaries, Cont.
a) oceanic-oceanic subduction
ii- Convergent plate boundaries, Cont.
b) Oceanic-continental subduction
ii- Convergent plate boundaries, Cont.
c) Continental - continental collision
iii- Transform or shear plate boundaries
iii- Transform or shear plate boundaries, Cont.
Why we study metamorphic rocks?
Goals of study metamorphic petrology includes:
- Academic goals: to deduce the following
-
Protolith (original rock) composition
-
Grade and conditions of metamorphism
-
Tectonic setting under which the metamorphism have done
- Applied goals: Metamorphic rocks like other rock types hosted
mineral resources e.g:
- Graphite, Talc, Magnesite, Asbestos, Corundum, vermiculites,
garnets, etc.
- They used also as ornamental stones as Slates, Marbles,
gneisses, metaconglomerates, greenstones and others