Energy and Mineral Resources
23
Energy and Mineral Resources begins with a discussion of renewable and nonrenewable resources. Coal, oil,
and natural gas are examined in some detail followed by environmental effects of burning fossil fuels, oil
sands and shales, and alternate energy sources. The relationship of mineral resources to igneous rocks,
metamorphic rocks, and weathering are presented. The chapter closes with a brief look at nonmetallic mineral
resources, including building materials and industrial minerals.
Learning Objectives
After reading, studying, and discussing the chapter, students should be able to:
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Distinguish between renewable and nonrenewable natural resources.
Briefly discuss the various types of energy resources, including coal, oil, and natural gas.
List and explain some of the environmental effects of burning fossil fuels.
Discuss the potential of tar sands and oil shale as possible energy resources in the future.
Briefly discuss the potential benefits and drawbacks to various alternate energy sources, including
nuclear, solar, wind, hydroelectric, geothermal, and tidal energy.
Explain the difference between mineral resources, mineral reserves, and mineral deposits.
Briefly discuss the origin of mineral resources related to igneous processes.
Explain the origin of mineral deposits unrelated to igneous processes, including metamorphic
processes, weathering, and placer deposits.
Discuss nonmetallic mineral resources, both building materials and industrial minerals.
Chapter Outline___________________________________________________________________
I.
Renewable and nonrenewable resources
A. Renewable resources
1. Can be replenished over relatively
short time spans
2. Examples
a. Plants
b. Animals for food
c. Trees for lumber
B. Nonrenewable resources
1. Significant deposits take millions
of years to form
2. Examples
a. Fuels (coal, oil, natural gas)
b. Metals (iron, copper, uranium,
gold)
C. Some resources, such as
groundwater, can go in either
category depending on how they are
used
II.
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Energy resources
A. Coal
1. Formed mostly from plant
material
2. Along with oil and natural gas,
coal is commonly called a fossil
fuel
3. The major fuel used in power
plants to generate electricity
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4. Problems with coal use
a. Environmental damage from
mining
b. Air pollution
B. Oil and natural gas
1. Oil and natural gas, consisting of
various hydrocarbon compounds,
are found in similar environments
2. Derived from the remains of
marine plants and animals
3. Formation is complex and not
completely understood
4. A geologic environment that
allows for economically
significant amounts of oil and gas
to accumulate underground is
termed an oil trap
a. Two basic conditions for an oil
trap
1. Porous, permeable reservoir
rock
2. Impermeable cap rock, such
as shale
b. Common oil and natural gas
traps include
1. Anticlinal traps
2. Fault traps
3. Stratigraphic traps
c. When the cap rock is
punctured by drilling, the oil
and natural gas, which are
under pressure, migrate from
the pore spaces of the reservoir
rock to the drill hole
C. Environmental effects of burning
fossil fuels
1. Urban air pollution
a. Air pollutants are airborne
particles and gases that occur
in concentrations that endanger
the heath of organisms and
disrupt the orderly functioning
of the environment
b. Two types of pollutants
1. Primary pollutants –
emitted directly from
identifiable sources
2. Secondary pollutants –
formed when chemical
reactions take place among
primary pollutants
2. Carbon dioxide and global
warming
a. Burning fossil fuels produces
carbon dioxide – one of the
gases responsible for warming
the lower atmosphere
b. Greenhouse effect – the
atmosphere is transparent to
incoming short wavelength
solar radiation. However, the
outgoing long-wave radiation
emitted by Earth is absorbed in
the lower atmosphere, keeping
the air near the ground warmer
c. It appears that global
temperatures have increased
(global warming) due to a
rising level of atmospheric
carbon dioxide
d. Possible consequences of
global warming include
1. A probable rise in sea level
2. Shifts in the paths of large
scale cyclonic storms
3. Stronger tropical storms
4. Increases in the frequency
and intensity of heat waves
and droughts
D. Oil sands and oil shale
1. Oil sands
a. Mixtures of clay and sand
combined with water and
bitumen (a viscous tar)
b. Several substantial deposits
around the world
c. Obtaining oil from tar sands
has significant environmental
drawbacks
1. Substantial land disturbance
Energy and Mineral Resources
2. Requires large quantities of
water
3. Produces contaminated
water and sediment
2. Oil shale
a. Contains enormous amounts of
untapped oil
b. Currently, because of world
markets and with current
technologies, not worth mining
E. Alternate energy sources
1. Nearly 90 percent of the world’s
energy needs are derived from
nonrenewable fossil fuels
2. Possible alternate energy sources
a. Nuclear energy
1. Energy from nuclear fission
2. Primary fuel is Uranium235
3. Obstacles to development
a. Cost to build nuclear
facilities
b. Possibility of serious
accidents
b. Solar energy – the direct use of
the Sun’s rays
1. Passive solar collectors –
e.g., south-facing windows
2. Active solar collectors –
e.g., roof-mounted devices
that collect heat or rooftop
photovoltaic systems
c. Wind energy – an almost free,
nonpolluting source of energy
that has been used for centuries
d. Hydroelectric power
1. Power generated by falling
water
2. Limited by the availability
of appropriate sites
3. Recently, pumped water
storage systems have come
into use
e. Geothermal energy
1. Tapping natural
underground reservoirs of
steam and hot water
f.
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2. Favorable geologic factors
include
a. A potent source of heat
b. Large and porous
reservoirs with channels
connected to the heat
source
c. A cap of low
permeability rocks
Tidal power
1. Harnessed by constructing
a dam across the mouth of
a bay or an estuary having
a large tidal range
2. Not feasible along most of
the world’s coasts
III. Mineral Resources
A. The endowment of useful minerals
ultimately available commercially
1. Mineral resources include
a. Reserves – already identified
deposits from which minerals
can be extracted profitably
b. As well as known deposits that
are not economically or
technologically recoverable
2. Ore – refers to useful metallic
minerals that can be mined at a
profit and in common usage to
some nonmetallic minerals such
as fluorite and sulfur
3. To be considered of value, an
element must be concentrated
above the level of its average
crustal abundance
B. Mineral resources and igneous
processes
1. Some of the most important
accumulations of metals are
produced by igneous processes
that concentrate the desirable
materials
2. Processes include
a. Magmatic segregation
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1. Heavy minerals that
crystallize early tend to
settle to the lower portion
of the magma chamber
2. In the late stages of cooling
granitic magmas, the
residual melt may become
enriched in rare elements
and heavy metals
b. Diamonds
1. Originate at great depths
2. Once crystals form, they
are carried upward toward
the surface
3. Crystals are disseminated in
ultramafic rock called
kimberlite
c. Hydrothermal solutions
1. Among the best known and
important ore deposits
a. Gold deposits of the
Homestake mine in
South Dakota
b. Lead, zinc, and silver
ores near Coeur
d’Alene, Idaho
2. Majority originate from hot,
metal rich fluids that are
remnants of late-stage
magmatic processes
3. Move along fractures,
cools, and precipitates the
metallic ions to produce
vein deposits
4. Disseminated deposits,
rather than being
concentrated in narrow
veins, are distributed
throughout an entire rock
mass
C. Mineral resources and metamorphic
rocks
1. Many of the most important
metamorphic ore deposits are
produced by contact
metamorphism
a. Sphalerite (zinc)
b. Galena (lead)
c. Chalcopyrite (copper)
2. Regional metamorphism can also
generate useful deposits
a. Talc
b. Graphite
D. Weathering and ore deposits
1. Secondary enrichment –
concentrating metals into
economically valuable
concentrations
a. By downward-percolating
water removing undesirable
materials
b. By carrying desirable elements
to lower zones and
concentrating them
2. Bauxite
a. Principal ore of aluminum
b. Forms in rainy tropical
climates from chemical
weathering and the removal of
undesirable elements by
leaching
3. Other deposits, such as many
copper and silver deposits, result
when weathering concentrates
metals that are deposited through
a low-grade primary ore
E. Placer deposits
1. Placers – deposits formed when
heavy metals are mechanically
concentrated by currents
2. Involve heavy and durable
minerals
3. Examples include
a. Gold
b. Platinum
c. Diamonds
F. Nonmetallic mineral resources
1. Use of the word “mineral” is very
broad
2. Two common groups
a. Building materials
Energy and Mineral Resources
1.
2.
3.
Natural aggregate (crushed
stone, sand, and gravel)
Gypsum (plaster and
wallboard)
Clay (tile, bricks, and
cement)
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b. Industrial minerals
1. Fertilizers
2. Sulfur
3. Salt
Answers to the Review Questions
1. The difference between renewable and nonrenewable resources is really a function of the time scale
involved. On a geological time scale, one could argue that even metallic mineral deposits are renewable
because they are currently forming at many locations on the ocean floor. The typical economist’s or
corporate executive’s time scale may be a few years to a few decades. In recent years, environmental
concerns have forced resource planners to consider time scales of hundreds and even thousands of years.
The idea is simply that a renewable resource, like hydroelectric power from a dam, will be there year after
year (as long as the rains come and the reservoir does not break or fill with sediments). Nonrenewable
resources such as petroleum, copper, coal, and groundwater (in dry land areas) were formed in the
geologic past and are not presently being replenished at even a tiny fraction of the rate at which they are
being used. Nonrenewable resources can be extracted for a finite length of time after which the resource is
exhausted or operating costs are too high to justify continuing production.
2. At the beginning of the 19th century, the world population had barely reached one billion; the population
has grown rapidly over the past 200 years, reaching two billion in 1930 and four billion in 1975. It could
easily reach seven billion during the first decade of the 21st century. In the near future, such a rapid
growth rate will result in lower living standards for most people because of increasingly harsh
environmental pressures on terrestrial and marine habitats, and intensified competition for living space
and natural resources.
3. More than 70 percent of domestically produced coal is burned in electrical power-generating plants in the
United States and abroad. Coal is an important U.S. export commodity. It fueled the industrial revolution
and was the dominant home-heating and railroad fuel until the late 1940s. The “dawn” of the petroleum
age early in this century portended an end to coal’s reign as the fossil fuel of choice, but rising electricity
consumption, huge domestic reserves, and problems with nuclear power have assured that coal will retain
a substantial role in domestic energy production in the foreseeable future.
Coals are generally ranked as lignite (brown coal), bituminous (soft coal), and anthracite (hard coal), with
lignite having the lowest carbon content and anthracite having the highest. Lignites provide the lowest
number of heat calories per unit weight. Bituminous coals rich in hot-burning, hydrocarbon compounds
may generate more heat energy than some anthracites of higher carbon contents.
Coal-fired electrical generation plants can use any rank of coal; steady, reliable supplies and low fuel
transportation costs are essential. Transporting fuel to the plant site is far more expensive, on an energy
unit per mile basis, than “sending” electricity to distant consumers over high voltage transmission lines.
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Thus most new coal-fired plants are sited at or relatively close to mines and utilize low-cost, fuel
transportation technologies (pipeline slurries, unit trains, etc.).
4. Oil traps are confined porous and permeable zones, usually in sedimentary rocks, that trap and retain the
constituents of crude oil in open pores, cracks, and cavities. All traps have porosity (open space) and
impermeable cover rocks that prevent the petroleum from leaking upward.
5. The pore spaces in oil sands and sandstones are saturated with highly viscous crude oil (bitumen).
Compared with high quality “light, sweet” crude, bitumen is more expensive to refine and produces lower
percentages of high value products such as gasoline and heating oil. Surface mining and waste disposal
present many serious environmental problems. At best, bitumen comprises only about 20 percent by
volume of the in situ oil sands. The huge tonnages mined to feed a large refinery result in large volumes
of processed sand and other wastes. Surface mining and waste disposal facilities disrupt the landscape and
destroy habitat, and toxic substances may seriously threaten aquatic communities, birds, other organisms,
and air quality.
6. Domestic oil shale reserves are mainly in northeastern Utah, southwestern Wyoming, and northwestern
Colorado. The oil shale accumulated as fine-grained, mostly chemical sediments in ancient lakes that
covered the area during Eocene time. Shale oil is very expensive to produce; presently it cannot compete
cost wise with other fuels such as petroleum and coal, and large-scale mining and shale oil production
would generate severe regional environmental impacts. For example, readily leached chemical
constituents in the massive tonnages of processed waste would seriously threaten water quality in the
Colorado River.
7. The main fuel for most nuclear power plants is uranium enriched in the fissionable isotope U-235; this
isotope comprises only 0.7 percent of natural uranium. Fissionable, manmade plutonium can also be used
as reactor fuel. Both materials are produced in government-owned facilities, many of which were
formerly associated with production of weapons-grade, enriched uranium and plutonium.
8. In its early day, nuclear energy was greatly oversold to the public as the wave of the future. Virtually all
costs associated with research, development, and U-235 enrichment were borne by the government and
the U.S. taxpayer. Reactor manufacturers and utility companies widely touted the low cost of nuclear
electricity and the unlimited supply of uranium for fission reactors and next generation of breeder
reactors. Environmental problems and accident risk, so prominent today, were quietly overlooked.
Incidents such as the Three Mile Island (Pennsylvania) accident and the Chernobyl (Ukraine) disaster
heightened public fears and concerns over nuclear plant safety and ignited a spirited public debate over
the future of nuclear electricity in the United States. Blanket assurances from government officials and
company executives no longer soothed a worried, cynical public.
Two major problems have effectively stopped growth of fission-generated electricity in the United States.
Capital costs of new generating facilities have escalated rapidly and the major issue of radioactive waste
disposal has yet to be satisfactorily addressed.
Historically, capital costs for new, electric power-generating plants were recouped after the plant was
operating. Utility rate payers are not happy with the prospect of bankrolling escalating construction costs
of very expensive, new plants long before any electricity is produced. New plants sited in dangerous areas
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(earthquake prone, for example) faced huge cost overruns to comply with safety requirements; others
built in heavily populated areas were completed but never operated because nearby areas could not be
evacuated quickly enough should a serious accident ever threaten the plant. Massive public borrowing
and overspending on new nuclear plants, based on overly optimistic projections of future electricity
usage, led to the largest municipal bond default in history by the state of Washington.
Safe storage and disposal of spent reactor fuel and other radioactive wastes is a very complex and difficult
technological problem and has become a volatile, highly contentious, public policy issue as well. The
waste remains dangerous for such long time spans that simple, out-of-sight, out-of-mind, disposal
concepts are inappropriate and dangerous; long term, isolated storage and constant monitoring are better
options.
Nuclear energy does have an advantage over conventional fossil fuels in that it does not emit carbon
dioxide – the greenhouse gas that contributes significantly to global warming. By contrast, the generation
of electricity from fossil fuels produces large quantities of carbon dioxide.
9. Sunlight falling on photovoltaic cells generates electricity directly. Cell efficiencies have been slowly
rising in recent years and costs have declined steadily. However, per kilowatt costs are still higher than
for conventional power plants, thus photovoltaic cells are used mainly in small, low demand devices such
as handheld calculators, or in remote locations where electricity from power grids is not readily available.
At larger-scale, solar generating facilities, the Sun’s rays are collected and focused to heat and vaporize
water or some low boiling point fluid. The heated vapor is then passed through turbines, generating
electricity in the same manner as in a conventional power plant.
10. All reservoirs eventually fill with sediment. A small dam across a steep-walled mountain canyon may fill
in a decade or two. Very large reservoirs such as Lake Powell (behind the Glen Canyon dam on the
Colorado River) may last for 300 years or more. By the time that half the original reservoir volume is
filled with sediment, much of the dam’s hydroelectric generation capacity has already been lost, and
turbid, sediment-laden water is more likely to reach intake penstocks, resulting in excessive wear on
turbines and increased maintenance costs. Thus a dam’s useful lifetime is over long before the pool
completely fills with sediment. In addition, a dam may deteriorate badly or pose a serious safety hazard
for other reasons long before its useful lifetime for power generation is over.
11. Generating electricity from tidal changes would be reliable, predictable, and relatively non-polluting.
However, coastal areas with consistently large daily tidal variations are sparse; in areas with lower tidal
ranges, the output of electricity per unit volume of flowing water would be very low because of the small
elevation difference between the reservoir and exit pools. Even in favorable areas, large volume reservoir
pools would be needed, raising construction costs and increasing adverse environmental effects. High
upfront capital costs and adverse environmental impacts mean that electricity from tides will probably
never contribute substantially to the world’s energy production.
12. Both terms refer to potential value that might be derived in the future from a nonrenewable resource such
as a copper deposit or petroleum accumulation. Reserve refers to the volume or tonnage of material that
can be extracted profitably in the near future (next few years or decades) based on the current value of the
product (today’s price of copper or petroleum) and the current or projected costs of producing the
product.
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Resource is a more general term that describes concentrations or accumulations of valuable materials,
such as copper or petroleum, which for various reasons (economic, environmental, political, etc.) are not
being exploited but which could be utilized at some time in the future.
13. This could readily happen if the price of the metal were to rise, production costs were to drop, or new
tonnages of higher grade material were discovered in the deposit; thus the desired product could then be
produced at a profit. Changes in environmental and political factors could also effect a change from
mineral deposit to ore deposit. Ore deposit has the same meaning as reserve, and mineral deposit has the
same meaning as resource (Review Question 14).
14. Hydrothermal solutions associated with igneous intrusions can deposit metals (copper, lead, zinc, silver,
etc.) as sulfide minerals in veins (long, open fractures); as small, disseminated grains; and as clusters of
grains in small cracks.
Hydrothermal springs issuing from the ocean floor can produce mounds and pinnacles of metal-rich
sulfides around the spring vent. When buried by lava flows or sedimentary layers, these deposits form
part of a stratigraphic section that represents an ocean floor environment. Because metal sulfide minerals
dominate these deposits, they are called massive sulfides.
15. Cooling igneous intrusions provide heat to drive extensive hydrothermal circulation through the intrusive
rock and surrounding wall rocks. These hydrothermal solutions dissolve metals and transport them to
depositional sites in fissures and open cracks, in other channels for fluid movement, and in fractured, or
chemically reactive, wall rocks. Hydrothermally deposited, magnetite-rich, iron ores and veins containing
copper, lead, zinc, and silver minerals can form in the contact metamorphic zone around a pluton.
16. The primary aluminum ore is bauxite, a complex mixture of various aluminum oxides and hydroxides.
Bauxite is a lateritic soil formed by intense, chemical weathering under moist, tropical conditions.
Bauxite accumulates where the parental bedrock material is rich in aluminum and low in iron; the intense,
chemical leaching removes silica and leaves only the highly insoluble, aluminum and iron oxides behind
in the surficial weathered zone.
17. Most copper deposits contain pyrite (FeS2) and copper sulfides or copper-iron sulfides as primary
minerals. Exposed to weathering, sulfide minerals decompose quickly. Iron oxides are insoluble and
remain behind in the outcrop; the copper dissolves in the strongly acidic water (a solution of sulfuric acid)
generated by the decomposing pyrite and is carried downward to be precipitated as copper sulfides below
the zone of oxidation. Thus strong limonitic or hematitic (iron oxide) staining at the surface may indicate
secondary enrichment of an underlying, primary deposit at depth.
18. Relatively higher density, chemically resistant minerals such as native gold, diamonds, rutile, and
cassiterite (tin oxide) are mined from placers. Placer deposits are mainly sand and gravel deposited in
swiftly flowing streams or along beaches with strong wave action and current activity. The dense mineral
grains are concentrated (left behind) as the smaller grains of the less dense minerals are carried elsewhere.
19. Nonmetallic resources, such as building materials and fertilizers, are consumed in all parts of the world at
far higher rates than are metallic resources. Sand and gravel, including crushed stone, are utilized in much
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larger amounts on a per capita basis than is iron, the most widely used metal. Increased use of glasses,
plastics, ceramics, and new, high-tech materials will undoubtedly limit future demand for most metals.
20. The two groups are industrial minerals (defined according to their major uses), and materials used in
construction and building. The latter group is most widely distributed and includes sand and gravel,
limestone (used to make Portland cement and agricultural lime), gypsum (used in plaster and wallboard),
and building stone; industrial minerals include quartz (glass manufacture), sulfur (for making sulfuric
acid), phosphate rock (fertilizer manufacture), rutile (used to manufacture white paint pigment), and hard
minerals (diamond, corundum, garnet) used to manufacture abrasives. Resources such as petroleum and
coal are considered as a separate fuels (energy) group.
Lecture outline, art-only, and animation PowerPoint presentations for each chapter of Earth,
9e are available on the Instructor’s Resource Center CD (0131566911).
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