SGES 1302 INTRODUCTION TO EARTH SYSTEM

Lecture 19: Natural Resources

Natural resources - Renewable resources

       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

      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 non renewable.

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

     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

      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:  Oxides (iron, aluminium, tin, manganese, etc)  Sulphides (copper, lead, zinc, molybdenum, etc); and  Native metals (gold, silver, platinum).

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

  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.   Internal processes      Magmatic processes Pegmatitic processes Hydrothermal Lateral secretion Metamorphic processes Surface processes      Mechanical accumulation Sedimentary precipitates Residual processes 2 ° or supergene enrichment Volcanic exhalative (SEDEX)

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Origin of Mineral Deposits

 Internal processes      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

 Surface processes      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)

   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

      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

     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

      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 (80 93% 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

     Solar Energy – heat & photovoltaic cell Hydroelectric Power Geothermal Energy Wind Energy Biofuels

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