Transcript SGES 1302 INTRODUCTION TO EARTH SYSTEM

SGES 1302
INTRODUCTION
TO EARTH SYSTEM
Lecture 19: Natural Resources
Natural resources - Renewable resources
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The resources that Earth provides are known as natural resources.
Natural resources include Earth’s organisms, nutrients, rocks, and
minerals.
Natural resources might come from the soil, air, water, or deep in
Earth’s crust.
Renewable resources are natural resources that can be replaced by
nature.
Renewable resources include fresh air; fresh surface water in lakes,
rivers, and streams; and most groundwater.
Renewable resources also include all living things and elements that
cycle through Earth’s systems, such as nitrogen, carbon, and
phosphorus.
Resources that exist in an inexhaustible supply, such as solar
energy, are also renewable resources.
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Natural resources – Non-renewable resources
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Non-renewable resources are resources that exists in a fixed amount in
various places in Earth’s crust and can be replaced only by geological,
physical, and chemical processes that take millions of years.
Resources such as fossil fuels, diamonds and other gemstones, and metals
such as gold, copper, and iron are therefore considered to be nonrenewable.
Natural resources are not distributed evenly on Earth.
Billions of people throughout the world use natural resources every day. Not
only are natural resources distributed unevenly on Earth, they are likewise
consumed unevenly.
Although people in the US make up only 6% of the world’s population, they
consume approximately 30% of Earth’s mineral and energy resources each
year.
Energy and resources are required to transport many resources from their
point of origin to the places where they are being consumed.
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Resources from Earth’s Crust
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Land resources – Land provides places for humans and other
organisms to live and interact. Land also provides spaces for the
growth of crops, forests, grasslands, and wilderness areas.
Air – organisms on Earth require oxygen or carbon dioxide to
maintain their life processes.
Water resources – same as air, without water there will not be life on
Earth
Mineral Resources – Metallic and non-metallic minerals are mined
and processed to make all kinds of products for our daily use, for the
industries, agricultural activities, etc.
Energy Resources – The use of energy is indispensable in this
modern age – light our homes, power our cars, sustain our
industries, etc.
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Mineral Resources - Metals
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All products that we use at home, industries, agriculture,
transportation, etc, requires vast supplies of minerals.
Modern societies and development cannot exist without adequate
supply of minerals.
Of over 3000 minerals know to exist, only a few dozens of metallic
and non-metallic minerals are important economically.
The metallic minerals are mainly:
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Oxides (iron, aluminium, tin, manganese, etc)
 Sulphides (copper, lead, zinc, molybdenum, etc); and
 Native metals (gold, silver, platinum).
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These minerals are widely disseminated throughout the Earth’s
crust.
Extraction of these minerals are economically feasible only where
geological processes have enriched them into mineable
concentrations (ore).
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Origin of Mineral Deposits
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Metallic ions are concentrated by geologic processes to form various
types of mineral deposits.
Evans (1987) divides ore genesis into the following main categories
based on physical-chemical processes.
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Internal processes
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Magmatic processes
Pegmatitic processes
Hydrothermal
Lateral secretion
Metamorphic processes
Surface processes
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Mechanical accumulation
Sedimentary precipitates
Residual processes
2° or supergene enrichment
Volcanic exhalative (SEDEX)
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Origin of Mineral Deposits
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Internal processes
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Magmatic processes - formed by direct crystallisation from a magma
(fractional crystallisation & liquation; eg. chromite & nickel)
Pegmatitic processes - crystallisation as dessiminated grains or
segregrations in pegmatites (eg. Lithium-tin-caesium pegmatites)
Hydrothermal - deposition from hot aqeous solutions. Hydrothermal
solution can leach out scarce elements from most rocks and precipate
them elsewhere at higher concentration. (eg. Tin-tungsten-copper veins,
most gold deposits in Peninsular Malaysia).
Lateral secretion - Diffusion of materials from the country rocks into
faults and fractures (eg. Mother Lode, USA).
Metamorphic processes - pyrosomatic (skarn) deposits formed by
replacement of wall rocks adjacent to an intrusion (eg. Mengapur
cupper deposit, Maran, Pahang & tin at Kramat Pulai, Perak)
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Origin of Mineral Deposits
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Surface processes
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Mechanical accumulation - Transported to the environment in which
they were deposited. Concentration of heavy & resistant minerals
(alluvial tin of Peninsular Malaysia, 2/3 of world’s gold deposits)
Sedimentary precipitates - Precipitation of particular elements in
suitable sedimentary environments (eg. banded iron formation,
manganese)
Residual processes - leaching from rocks of soluble elements leaving
concentrations of insoluble elements in the remaining materials (eg.
bauxite & nickel laterite)
2° or supergene enrichment - leaching of valuable elements from the
upper parts of mineral deposits and then precipitation at depth to
produce higher concentrations.
Volcanic exhalative (SEDEX) - exhalation of hydrothermal solutions at
the surface, usually under marine conditions. Most important source of
lead, zinc and barite, a major contributor of silver, copper, gold, bismuth
and tungsten.
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Mineral Resources – Non-Metals (Industrial Minerals)
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Industrial minerals are defined as including any rock, mineral or
other naturally occurring substance of economic value but excluding
metallic ores, mineral fuels and gemstones.
For some industrial minerals the unit value is so low that transport
costs over any appreciable distance can make them non-competitive
and an efficient bulk transport infrastructure is essential;
consequently deposits of these minerals must be exploited close to
a market.
Industrial minerals include aggregates and constructional materials,
clays, limestone and dolomite, gypsum, etc.
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Energy Resources – Fossil Fuels
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We obtain little of our energy from renewal resources. We obtain
most of our energy from fossil fuels, which are non-renewable.
The principal fossil fuels are oil, natural gas and coal.
Oil and gas have passed their peak production in many producing
countries.
At the current rate of extraction, the petroleum reserves will be
exausted in the next century or so.
Petroleum generally formed in marine basins in tropical environment
with abundant microscopic organisms and organic debris.
The organic materials are deposited together with sediments, and
with increasing heat and pressure on burial, the organic materials
are converted to kerogen, then to hydrocarbon.
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Energy Resources – Fossil Fuels
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The rocks in which hydrocarbon form are called source rock,
typically are shales and siltstones rich in organic matter.
After they are formed, the gaseous or liquid hydrocarbons are
expelled from the compacting source rocks.
The hydrocarbons tend to migrate upwards to the adjacent
permeable reservoir rock, eg, well sorted sandstone.
The hydrocarbons continue to migrate upwards until they are
trapped by an impermeable cap rock or reach the surface as oil or
gas seep.
For the development of a viable resource, all the conditions required
to produce, trap and retain hydrocarbon must occur together.
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Energy Resources – Fossil Fuels
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Coal is the most abundant fossil fuel in the world, but its use has
decline in the last few decades.
Coal deposits are likely to occurred mainly in tropical and
subtropical swamps, where abundant plant debris are accumulated
as peat (~50% C).
With burial, the peat is compressed to form lignite, a soft brown coal
with 70% C.
With increase heat and pressure, lustrous black bituminous coal (8093% C) is form, and finally transformed into antracite (>93% C).
With increasing grade from peat to antracite, combustion produces
less smoke and more heat.
Other fossil fuels: Oil shale, oil sand/tar sand, shale gas.
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Renewable Energy Resources
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Solar Energy – heat & photovoltaic cell
Hydroelectric Power
Geothermal Energy
Wind Energy
Biofuels
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