Mineral Resources

Learning Objectives
▪ Understand the importance of the different
minerals to the society; and
▪ Understand the different ways on how the
mineral deposits are formed.

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Mineral
Deposits
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Mineral Occurrence
▪ concentration of a mineral that is of scientific
or technical interest.
Mineral Deposit
▪ mineral occurrence of sufficient size and grade
or concentration to enable extraction under the
most favorable conditions.

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Ore Deposit
▪ mineral deposit that has been tested and
known to be economically profitable to mine.

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Aggregate

▪ rock or mineral material used as filler in

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Ore
▪ naturally-occurring material from which a
mineral or minerals of economic value can be
extracted.

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▪ Most rocks of the Earth's crust contain metals and other
elements but at very low concentrations.
▪ For example, the average concentration of Gold in rocks
of the Earth's crust is about 0.005 ppm (parts per million)
which is roughly 5 grams of gold for every 1000 tons of
rock. Although valuable, extracting Gold at this
concentration is not economic (the cost of mining will be
too high for the expected profit). Fortunately, there are
naturally occurring processes (geologic processes) that
can concentrate minerals and elements in rocks of a
particular area.

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Types of Mineral
Resources

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Occurrence of a Mineral
Resource
▪ The geologic processes
involved in the rock
cycle play major role
in the accumulation
and concentration of
valuable elements/
minerals.

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▪ Plate tectonics: the Earth’s crust is
broken into a dozen or more plates of
different sizes that move relative to
one another (lithosphere). These plates
are moving slowly on top of a hot and
more mobile material called the
asthenosphere. The diagram below
shows the different mineral deposits
that usually occur in different tectonic
environments.

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 Mineral resources can be
classified according to the
mechanism responsible for
concentrating the valuable
substance.

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1. Magmatic Ore Deposits
▪ valuable substances are concentrated within an
igneous body through magmatic processes
such as crystal fractionation, partial melting
and crystal settling.
▪ magmatic processes can concentrate the ore
minerals that contain valuable substances after
accumulating elements that were once widely
dispersed and in low concentrations within the
magma.
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Examples:
▪ Crystal settling: as
magma cools down,
heavier minerals tend
to crystallize early and
settle at the lower
portion of the magma
chamber

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Examples:
▪ Fractional crystallization: the residual melt contains high
percentage of water and volatile substances that are favorable for
the formation of pegmatites. Pegmatites are enriched in Lithium,
Gold, Boron, rare elements and some other heavy metals.

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Examples:
▪ Fractional crystallization of granitic magmas
can concentrate rare earth elements (such as
cesium and uranium) and heavy metals. This
can also form pegmatites (large crystals of
quartz, feldspars and muscovite)which may
contain semi-precious gems such as beryl,
topaz, and tourmaline

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2. Hydrothermal Ore Deposits
▪ concentration of valuable substances by hot
aqueous (water-rich) fluids flowing through
fractures and pore spaces in rocks.

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Hydrothermal Solutions - are hot, residual
watery fluids derived during the later stages of
magma crystallization and may contain large
amount of dissolved metals.
▪ These can also originate from the ground
water circulating at depth that is being heated
up by a cooling and solidifying igneous body
or along depths with known geothermal
gradient.

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Examples:
▪ Vein type deposits - A fairly well defined zone of
mineralization, usually inclined and discordant and
typically narrow.
▪ Disseminated deposits - Deposits in which the ore
minerals are distributed as minute masses (very low
concentration) through large volumes of rocks. This
occurrence is common for porphyry copper deposits.

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Examples:
▪ Massive sulfide deposit (at oceanic spreading
centers) - Precipitation of metals as sulfide
minerals such as sphalerite (ZnS) and
chalcopyrite (CuFeS2) occurs when hot fluids
that circulated above magma chambers at
oceanic ridges that may contain sulfur, copper
and zinc come in contact with cold
groundwater or seawater as it migrate towards
the seafloor. 25
Examples:
▪ Stratabound ore deposits (in lake or oceanic
sediment) – This deposit is formed when the
dissolved minerals in a hydrothermal fluid
precipitate in the pore spaces of unconsolidated
sediments on the bottom of a lake or ocean.

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3. Sedimentary Ore Deposits
▪ Some valuable substances are concentrated by
chemical precipitation coming from lakes or
seawater.

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Examples:
▪ Evaporite Deposits: This type of deposit
typically occurs in a closed marine
environment where evaporation is greater than
water inflow.
▪ Iron Formation: These deposits are made up
of repetitive thin layers of iron-rich chert and
several other iron bearing minerals such as
hematite and magnetite.
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 4. Placer Ore Deposits
▪ Deposits formed by the concentration of valuable substances through
gravity separation during sedimentary processes.
▪ Usually aided by flowing surface waters either in streams or along
coastlines.
▪ Usually involves heavy minerals that are resistant to transportation and
weathering.
▪ Common deposits are gold and other heavy minerals such as platinum,
diamonds and tin;
▪ The source rock for a placer deposit may become an important ore body
if located.
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5. Residual Ore Deposits
▪ A type of deposit that results from the
accumulation of valuable materials through
chemical weathering processes.
▪ During the process, the volume of the original rock
is greatly reduced by leaching.
▪ Important factors for the formation of residual
deposit include parent rock composition, climate
(tropical and sub-tropical: must be favorable for
chemical decay) and relief (must not be high to
allow accumulation) 31
Thanks!

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