Question No.2:
Where
in the Kingdom we should direct the
exploration activities for the following
types of ore deposits : Rand type , Zambia and
Kupferschifer copper deposits .
Model Answer of Question No. 2:
1-
Knowing the age of the
Arabian shield and the age of Rand type
deposits, the student should know that this type is not present in the kingdom.
2-
The Zaambi copper
deposits could be present in the
Proterozoic basement rocks
e.g. Abla Formation where the rock sequence are similar to
those in the Zambia
deposits.
3-
The sedimentary cover rocks to the east of the shield, particularly the
Permian
Formations.
Question No.3:
Draw
two sections to show the rocks of the ophiolite sequence and the Bushveld intrusion. What are the deposits associated
with them?
Model Answer of Question No. 3:
The
student should drew a section showing the rock types of the ophiolitic sequence
( ultramafic, gabbros, sheeted dykes, pillow lava and pelagic sediments.
Chromite with the ultramafic rocks, VMS with the pillow lava, gold in the
listvenitized ultramafics.
The
student should drew a section showing the different zones of the Bushveld
complex with the rock types. Chromite in the basal zone, Cu – Fe – Ni (Pt) mineralization in the critical zone, magnetite – ilmenite – apatite
( nelsonite ) in the upper zone.
Question No. 4:
What
are the mineralogical changes in a sulphide deposit consisting of galena,
sphalerite, chalcopyrite, pyrite and gold
when exposed to chemical weathering ?
Model Answer of Question No. 4:
Oxidation zone:
Pyrite
→ goethite
Chalcopyrite
→ Goethite + CuSO4
Galena → cerussite
Sphalerite
→ ZnSO4 ( washed out from this zone )
Gold stay in the oxidation zone ( gossan )
Reduction zone :
Chalcopyrite
+ CuSO4 → CuS.
Pyrite
→ Cu2S
Galena → CuS
Question No. 5:
Give reasons:
1. Accumulation of chromite as layers in the
lower part of Bushveld Complex.
2. The wide
distribution of the Alpine type chromite deposits in the Phanerozoic
and its rarity in the Precambrian.
3. The wide
distribution of the sulphide deposits in the southern part of the Sudbury
intrusion.
4. The occurrence of Sn, W, U and Zr in
hydrothermal and pegmatite deposits.
5. The
abundance of silver and argentite in epithermal deposits.
6.
The absence of skarn deposits along the contact of the mafic intrusions.
7.
The high nickel content of dunite.
- The
wide occurrence of oxide minerals in beach placers.
- The restriction of Rand
type deposits to the Lower Proterozoic.
- The lead content does not increase in the
supergene sulphide deposits.
Model Answer of Question No. 5:
1- The presence of ultramafic rocks and gravitational settling.
2- Because of deformation and erosion.
3- The presence of the
metavolcanics and metasediments rich in pyrite.
4- Because they are incompatible elements (large size and high
charge ).
5- Because of the higher content of Ag.
6- Because of its lower content in volatiles.
7- Replacement of Mg by Ni and the low oxygen fugacity.
8- Because of their stability, high density and durability.
9- The atmosphere was reducing.
10- When oxidized, galena
remains as cerussite in the oxidation zone.
Question No. 6:
A. Complete :
1-
Diamonds are most commonly associated with an ultramafic rock
called--------------.
2.
The most productive diamond mines are located in (what country) ----------------
3-
Minerals that contain the same chemical elements but exhibit different
properties are called -----------------.
4-
The age of the Kupferschiefer deposits is -------------------.
5-
The most abundant volcanic rock in volcanic mountains is ---------------.
6-
The Himalaya mountains are the products of
-----------------.
7-
Divergent oceanic plates are exemplified by -----------------.
8-
Tin mineralizations are associated with -------- type of granite.
9-
The most common minerals in placer deposits are-------------, ------------- , ------------, ---------------- , ----------------.
10-
The economic minerals in Mississippi
valley type deposits are ---------------, -------------------, --------------------, ---------------------.
11-
Bauxite is formed by ------------- weathering of rocks rich in ------- such
as-------------------------- .
B. Multiple choice :
1.
The chemical formula of chalcopyrite a)
CuFeS2 b) Cu5FeS4 c) Cu2S.
2.
The tectonic setting of the Andes
mountains a) Island Arcs b) Within plates
c)
ocean – continent subduction.
3.
Kuroko deposits are formed in a) Mid-ocean
ridges b) Island arcs c) oceanic Islands.
4-
The age of the Zambian copper deposits is a) Proterozoic b) Phanerozoic c) Archean.
5-
Chromite deposits are associated with a)
Dunite b) norite c) Anorthosite.
6-
Sulphosalts are common in a) Epithermal
b) Mesothermal c) Hypothermal.
7-
Greisen is a ……………. rock a)
Magmatic b) Metamorphic c) Metasomatic.
8- …………… is an igneous rock a) Eclogite
b) nelsonite c) granulite.
9-
The age of the Arabian shield is a) 1800
m.y. b) 950 m.y.
c) 450 m.y.
10-
The boundary between the Precambrian and Cambrian is a) 320 m.y.
b) 570 m.y.
c) 1100 m.y.
Model Answer of Question No. 6:
Complete:
- kimberlite. 2. South
Africa. 3.Polymorphs. 4. Permian. 5.
Andesite. 6. Collision.
- M.O.R. 8. S type granite. 9. Magnetite, chromite, rutile,
ilmenite, Diamond.
10.
Sphalerite, Galena, Barite, Fluorite. 11.
Chemical, Al, Syenite.
Multiple choice :
1. a)
CuFeS2. 2. c) Ocean – continent subduction. 3. b) Island
arcs. 4. a) Proterozoic. 5. a) Dunite . 6. a) Epithermal. 7. c) Metasomatic. 8.
b) Nelsonite. 9. b) 950 m.y. 10. b)
570 m.y.