Magmatic ore deposits are the biggest and most
important mineral source of known mineral, which is
useful for human being. This group of minerals
supplies an enormous human need, such as steel,
copper, platinum, titanium and chromium. They are
directly in relation to magma and its crystallization
stages during upward movement from deeper parts of the
crust to near ground surface.
Mineralisation diversity in this group of ore deposits
originates from composition of mineral-making magmas,
difference in origin and their upward way. In
general, magmatic ore deposits are divided to two
parts; 1.ore deposits relating to mafic and ultramafic
magmas. 2.ore deposits relating to intermediate and
One property is common among all magmatic ore deposits
that is; minerals are formed at the stage of magma
crystallization and usually homogeneously disseminated
in igneous rocks bearing low carat (diamond ore
deposit and porphyry copper). Sometimes, due to
plenty of differences between specific gravity and
molten silicates, minerals fall in molten magma after
crystallization and in lower parts of magma room are
vastly accumulated in form of a clear layer (chromite
Porphyry copper ore deposits
Porphyry copper ore deposits are the most important
among porphyry ore deposits. They include the biggest
copper reserves of the world. All porphyry ore
deposits have one common point that is; the host rock
of all of them is an igneous host rock of mineral
process. Porphyritic texture appears in form of
relatively large crystals (phenocrysts) which are
surrounded by finer grained crystals of groundmass.
This texture indicates that the cooling process of
magma has taken place within two stages. First is the
early slow stage in which crystals becomes cool
slowly, therefore their size is bigger. Second is the
quick phase in which crystals becomes cool quickly,
therefore their size is smaller. This texture is
observed in intrusive massives coming from the deeper
parts to near ground surface. In these intrusive
massives, if magma is full of minerals, such as
copper, molybdenum, uranium, gold, tungsten and tin
due to quick process of cooling, these materials do
not have sufficient time to separate from magma and
crystallize in suitable spaces, such as faults and
In these circumstances, minerals, such as
chalcopyrite, molybdenite, gold, cassiterite, etc.
have disseminated in groundmass. Thus, all intrusive
massives are mineralized with low carat. The carat of
mineral in these ore deposits is seldom more than
5.1%. But one property makes these minerals valuable
that is the enormous volume of mineralization and high
reserves of these minerals. Today, man could obtain
minerals in a carat less than 1% by advancement of
technology. Hence, as time goes by, the strategic
significance of porphyry reserves becomes more and
more. The most important ore deposits are as follows;
*Vein-form copper ore deposit
*Contact metamorphism (skarn) ore deposit of copper
*Sedimentary ore deposit of copper
*Porphyry ore deposit of copper
Because of high reserves and low costs for
exploitation, porphyry copper ore deposits are very
Porphyry copper ore deposits produce most of the
world’s copper. Based on the type of igneous
intrusive rock which is the host of mineralisation,
porphyry copper ore deposits are divided to two parts;
Porphyry copper ore deposits; monzonitic type
In this group of porphyry ore deposits, the host rock
is monzonite to porphyritic granodiorite holding
calcalkaline composition. This intrusive massives are
observable in subduction zones and at the margin of
continents. These hypabyssal intrusive massives are
in form of stock, dyke and seldom batholithes.
In this group, the copper carat is 5 and ore deposit
is 95 to 3000 million ton. The by-product of this ore
deposit is gold and relatively is molybdenum.
Examples of dioritic porphyry copper in the world are
-Pandora copper ore deposit
-Bonsai copper in the Philippines
-Cerro colorado in Panama
Shape and texture of mineral reserve
In general, reserves of porphyry copper ore deposits
have umberella-shape, convex lens, discoidal and
cylinderical shape. Intrusive massive shape,
fractures and local crushed zones impress shape of
mineral massive. Reserve is usually formed in the
upper part or so-called ceiling of intrusive massive.
Sometimes, reserve reaches the surroundings of its
rocks. The texture of massive often has a
disseminated texture, but mineralisation appears in
Kimberlites and diamond reserves
Kimberlite is an ultramafic igneous rock. It is rich
of potassium which comprises pieces of rocks and
minerals of crust and mantle. Kimberlite are mostly
found in continental crusts, particularly in its
stable parts which is called kraton or shield.
Kimberlite-type magmas originate from molten mantle
materials. High level of gas content of carbon
dioxide, fluor and water in kimberlite magmas causes
an explosive condition for these types of magma.
Kimberlite magma explodes during upward movement and
produces explosive volcanic crater on ground surface.
This crater reaches a kimberlite dyke located deep in
ground via a funnel-shape passage called diatherm.
The most important kimberlite minerals are serpentine,
flogopite, termolite, calcite, magnetite, apatite,
olivine, pyroxene, nepheline and diamond. Diamond is
the most important economic mineral exploiting from
kimberlites. But all kimberlites are not a source for
diamonds. Diamond appears in kimberlite groundmass
disseminatedly. But its carat is normally low and
varies between 1 to 60 gr/ton. Laboratory studies and
field observations have indicated that diamond is
crystallized at the temperature of 1100C and pressure
of about 50Kb. These conditions can be only available
the mantle depth. Therefore, diamond is crystallized
in these parts of mantle. Every magma originating
from this part can bring diamond to the ground
surface. The speed of this magma must not be less
than 70km/h. Otherwise, diamonds are dissolved in
molten magma and in form of carbon dioxide gas enters
in gaseous part of magma. Therefore, kimberlites do
not have diamond reserves. Kimberlites age is
cretaceous. The most important kimberlite reserve
located in the South Africa, Russia, the United States
and India. The name of kimberlite comes from Kimberly
region in the South Africa.
