Chapter 21: Resources of Minerals and Energy

1
Chapter 21 Resources of Minerals and Energy
2
Introduction Natural Resources And Human
History (1)

• Over one hundred sixty thousand years ago, our
  ancestors probably began to use flint, chert, and
  obsidian to make tools.
• Metals were first used more than 20,000 years
  ago.
• Copper and gold were the earliest metals used.
• By 6000 years ago, our ancestors extracted copper
  by smelting.
• Before another thousand years had passed, they
  had discovered how to smelt lead, tin, zinc,
  silver, and other metals.

3
Introduction Natural Resources And Human History
(2)

• The technique of mixing metals to make alloys
  came next.
• Bronze was composed of copper and tin.
• Pewter was composed of tin, lead, and copper.
• The smelting of iron came much laterabout 3300
  years ago.
• The first people to use oil instead of wood for
  fuel were the Babylonians, about 4500 years ago.
• The first people to mine and use coal were the
  Chinese, about 3100 years ago.

4
Mineral Resources (1)

• Mineral deposits are any volume of rock
  containing an enrichment of one or more minerals.
• Mineral resources have three distinctive
  characteristics
• Occurrences of usable minerals are limited in
  abundance and localized at places within the
  Earths crust.
• The quantity of a given mineral available in any
  one country is rarely known with accuracy.
• Deposits of minerals are depleted by mining and
  eventually exhausted.

5
Figure 21.1
6
Figure 21.2
7
Mineral Resources (2)

• Ore is an aggregate of minerals from which one or
  more minerals can be extracted profitably.
• Ore is an economic term, whereas mineral
  deposit is a geologic term.
• The economic challenges of ore are to find it,
  mine it, and refine it as cheaply as possible.
• The lowest-grade ores ever minedabout 0.5
  percent copperwere worked only at a time of high
  metal prices.

8
Mineral Resources (3)

• In 2002, lowest grade of of mineable copper ore
  is closer to 1 percent.
• Over production of copper around the world,
  combined with economic recession, has resulted in
  the closing of many mines, particularly those
  exploiting the lowest grades of ores.

9
Mineral Resources (4)

• Sphalerite, galena, and chalcopyrite are ore
  minerals from which zinc, lead, and copper
  respectively can be extracted.
• Ore minerals rarely occur alone.
• They are mixed with other nonvaluable minerals,
  collectively termed gangue.
• Gangue may include quartz, feldspar, mica,
  calcite, or dolomite.

10
Origin Of Mineral Deposits (1)

• All ores are mineral deposits because each of
  them is a local enrichment of one or more
  minerals or mineraloids.
• Not all minerals deposits are ores.
• In order for a deposit to form, processes must
  bring about a localized enrichment of one or more
  minerals.

11
Origin Of Mineral Deposits (2)

• Minerals become concentrated in five ways
• 1. Concentration by hot, aqueous solutions
  flowing through fractures and pore spaces in
  crustal rock to form hydrothermal mineral
  deposits.
• 2. Concentration by magmatic processes within a
  body of igneous rock to form magmatic mineral
  deposits.

12
Origin Of Mineral Deposits (3)

• 3. Concentration by precipitation from lake water
  or sea water to form sedimentary mineral
  deposits.
• 4. Concentration by flowing surface water in
  streams or along the shore, to form placers.
• 5. Concentration by weathering processes to form
  residual mineral deposits.

13
Hydrothermal Mineral Deposits (1)

• Some solutions originate when water dissolved in
  magma is released as the magma rises and cools.
• Other solutions are formed from rainwater or
  seawater that circulates deep in the crust.
• Mineral deposits formed from midocean ridge
  volcanism are called volcanogenic massive sulfide
  deposits.

14
Figure 21.3
15
Hydrothermal Mineral Deposits (2)

• The pyroxene-rich rocks of the oceanic crust
  yield solutions charged with copper and zinc.
• As a result, volcanogenic massive sulfide
  deposits are rich in copper and zinc.
• In black smokers, the rising hydrothermal fluid
  appears black due to fine particles of iron
  sulfide and other minerals precipitated from
  solution as the plume is cooled by contact with
  cold seawater.
• The chimney-like structure is composed of pyrite,
  chalcopyrite, and other ore minerals deposited by
  hydrothermal solution.

16
Hydrothermal Mineral Deposits (3)

• When a hydrothermal solution moves slowly upward,
  as with groundwater percolating through an
  aquifer, the solution cools very slowly.
• If dissolved minerals were precipitated from such
  a slow-moving solution, they would be spread over
  a large volume of rock and would not be
  sufficiently concentrated to form an ore.

17
Hydrothermal Mineral Deposits (4)

• When a solution flows rapidly, as in an open
  fracture, or through a mass of shattered rocks,
  or through a layer of porous tephra where flow is
  less restricted, cooling can be sudden and can
  occur over short distances.
• Rapid precipitation and a concentrated mineral
  deposit are the result.
• Veins formed when hydrothermal solutions deposit
  minerals in open fractures.
• Many such veins are found in regions of volcanic
  activity.

18
Figure 21.5
19
Hydrothermal Mineral Deposits (5)

• The famous gold deposits at Cripple Creek,
  Colorado, were formed in fractures associated
  with a small caldera.
• The huge tin and silver deposits in Bolivia are
  in fractures that are localized in and around
  stratovolcanoes.
• Many famous ore bodies are associated with
  intrusive igneous rocks.
• Tin in Cornwall, England,
• Copper at Butte, Montana, Bingham, Utah, and
  Bisbee, Arizona.

20
Figure 21B1
21
Figure 21B2
22
Magmatic Mineral Deposits (1)

• The processes of partial melting and fractional
  crystallization are two ways of separating some
  minerals from other.
• The processes involved are entirely magmatic, and
  so such deposits are referred to as magmatic
  mineral deposits.

23
Magmatic Mineral Deposits (2)

• Pegmatites formed by fractional crystallization
  of granitic magma commonly contain rich
  concentrations of such elements as
• Lithium.
• Beryllium.
• Cesium.
• Niobium.

24
Magmatic Mineral Deposits (3)

• Much of the worlds lithium is mined from
  pegmatites such as those at Kings Mountain,
  North Carolina, and Bikita in Zimbabwe.
• The great Tanco pegmatite in Manitoba, Canada,
  produces much of the worlds cesium, and
  pegmatites in many countries yield beryl, one of
  the main ore minerals of beryllium.

25
Magmatic Mineral Deposits (4)

• Crystal settling, another process of fractional
  crystallization, is especially important in
  low-viscosity basaltic magma.
• One of the first minerals to form is chromite,
  the main ore mineral of chromium.
• The dense chromite crystals settle to the bottom
  of the magma, producing almost pure layers of
  chromite.
• The worlds principal deposits of chromite are in
  the Bushveld igneous complex in South Africa and
  the Great Dike of Zimbabwe.

26
Sedimentary Mineral Deposits

• The term sedimentary mineral deposits is applied
  to any local concentration of minerals formed
  through processes of sedimentation.
• One form of sedimentation is the precipitation of
  substances carried in solution.
• There are three types of sedimentary mineral
  deposits
• Evaporite deposits.
• Iron deposits.
• Stratabound deposits.

27
Evaporite Deposits (1)

• Evaporite deposits are formed by evaporation of
  lake water or seawater.
• The layers of salts precipitate as a consequence
  of evaporation.
• Salts that precipitate from lake water of
  suitable composition include sodium carbonate
  (Na2CO3), sodium sulfate (Na2SO4), and borax
  (Na2B4O7.1OH2O).

28
Evaporite Deposits (2)

• Huge evaporite deposits of sodium carbonate were
  laid down in the Green River basin of Wyoming
  during the Eocene Epoch.
• Oil shales were also deposited in the basin.
• Borax and other boron-containing minerals are
  mined from evaporite lake deposits in Death
  Valley and Searled and Borax Lakes, all in
  California and in Argentina, Bolivia, Turkey,
  and China.

29
Evaporite Deposits (3)

• Much more common and important than lake water
  evaporites are the marine evaporites formed by
  evaporation of seawater.
• The most important salts that precipitate from
  seawater are
• Gypsum (CaSO4.2H2O).
• Halite (NaCl).
• Carnallite (KCl.MgCl2.6H2O).

30
Evaporite Deposits (4)

• Low-grade metamorphism of marine evaporite
  deposits causes another important mineral,
  sylvite (KCl), to form from carnallite.
• Marine evaporite deposits are widespread.
• In North America, for example, strata of marine
  evaporites underlie as much as 30 percent of the
  land area.

31
Evaporite Deposits (5)

• Marine evaporites produce
• Most of the salt that we use.
• The gypsum used for plaster.
• The potassium used in plants fertilizers.

32
Figure 21.6
33
Iron Deposits (1)

• Sedimentary deposits of iron minerals are
  widespread, but the amount of iron in average
  seawater is so small that such deposits cannot
  have formed from seawater that is the same as
  todays seawater.

34
Iron Deposits (2)

• All sedimentary iron deposits are tiny by
  comparison with the class of deposits
  characterized by the Lake Superior-type iron
  deposits.
• These remarkable deposits, mined principally in
  Michigan and Minnesota, were long the mainstay of
  the U.S. steel industry.
• They are declining in importance todaybecause
  imported ore is replacing them.
• They are of early Proterozoic age (about 2
  billion years or older).

35
Iron Deposits (3)

• They are found in sedimentary basins on every
  craton (Labrador, Venezuela, Brazil, Russia,
  India, South Africa, and Australia).
• They appear to be the product of chemical
  precipitation.
• They are interbedded layers of chert and several
  different kinds of iron minerals.
• The cause of precipitation remains uncertain.

36
Iron Deposits (4)

• Many experts suspect these evaporites formed from
  seawater of a different composition than todays
  seawater.
• The grade of the deposits ranges from 15 to 30
  percent Fe by weight.

37
Iron Deposits (5)

• Two additional processes can form iron ore
• First, leaching of silica during weathering can
  lead to secondary enrichment and can produce ores
  containing as much as 66 percent Fe.
• The second way a Lake Superior-type iron can
  become an ore is through metamorphism.
• First, grain sizes increase so that separating
  ore minerals from the gangue becomes easier and
  cheaper.
• Second, new mineral assemblages form, and iron
  silicate and iron carbonate minerals originally
  present can be replaced by magnetite or hematite,
  both of which are desirable ore minerals.

38
Figure 21.7
39
Iron Deposits (5)

• Ore grade is not increase by metamorphism,
• The changes in grain size and mineralogy
  transform the sedimentary rock into an ore.
• Iron ores formed as a result of metamorphism are
  called taconites, and they are now the main kind
  of ore mined in Lake Superior region.

40
Stratabound Deposits (1)

• Some of the worlds most important ores of lead,
  zinc, and copper occur in sedimentary rock
• The ore mineralsgalena, sphalerite,
  chalcopyrite, and pyriteoccur in such regular,
  fine layers that they look like sediments.
• The sulfide mineral layers are enclosed by and
  parallel to the sedimentary strata in which they
  occur.
• For this reason, they are called stratabound
  mineral deposits.

41
Figure 21.8
42
Stratabound Deposits (2)

• Most stratabound deposits are diagenetic in
  origin.
• Stratabound deposits form when a hydrothermal
  solution invades and reacts with a muddy
  sediment.
• The famous copper deposits of Zambia, in central
  Africa, are stratabound deposits.
• The worlds largest and richest lead and zinc
  deposits are also stratabound
• Broken Hill, Australia.
• Mount Isa in Australia.
• Kimberley in British Columbia.

43
Placers (1)

• A mineral with a high specific gravity will
  become concentrated by flowing water.
• Deposits of minerals having high specific
  gravities are placers.
• Most placers are found in stream gravels that are
  geologically young.

44
Figure 21.9
45
Figure 21.10
46
Placers (2)

• The most important minerals concentrated in
  placers are gold, platinum, cassiterite (SnO2),
  and diamond.
• More than half of the gold recovered throughout
  all of human history has come from placers.

47
Placers (3)

• The South African fossil placers are a series of
  gold-bearing conglomerates.
• They were laid down 2.7 billion years ago as
  gravels in the shallow marginal waters of a
  marine basin.
• Associated with the gold are grains of pyrite and
  uranium minerals.
• Nothing like the deposits in the Witwatersrand
  basin has been discovered anywhere else.
• Mining the Witwatersrand basin has reached a
  depth of 3600 m (11,800 ft).
• The deposits are running out of ore.

48
Residual Mineral Deposits (1)

• Chemical weathering leads to mineral
  concentration through the removal of soluble
  materials and the concentration of a less soluble
  residue.
• A common example of a deposit formed through
  residual concentration is bauxite.

49
Residual Mineral Deposits (2)

• Bauxites are
• The source of the worlds aluminum.
• Concentrated in the tropics because that is where
  lateritic weathering occurs.
• Found in present-day temperate conditions, such
  as France, China, Hungary, and Arkansas, where
  the climate was tropical when the bauxites
  formed.
• Not found in glacial regions.
• Glaciers scrape off the soft surface materials.

50
Residual Mineral Deposits (3)

• More than 90 percent of all known bauxite
  deposits formed during the last 60 million years,
• All of the very large bauxite deposits formed
  less than 25 million years ago.

51
Residual Mineral Deposits (4)

• Many of the worlds manganese deposits have been
  formed by secondary enrichment of low-grade
  primary deposits, particularly in tropical
  regions. Secondary enrichment zones are produced
  by deposition of soluble minerals near the
  groundwater table, leached from mineral deposits
  present near the surface.
• One of the largest nickel deposits ever found, in
  New Caledonia, was formed by secondary enrichment.

52
Residual Mineral Deposits (5)

• Secondary enrichment has led to large deposits in
  the arid southwestern United States and desert
  regions of northern Chile of
• Pyrite (FeS2).
• Chalcopyrite (CuFeS2).
• Chalcocite (CuS2).

53
Useful Mineral Substances (1)

• Excluding substances used for energy, there are
  two broad groups of useful minerals
• Metallic minerals, from which metals such as
  iron, copper, and gold can be recovered.
• Nonmetallic minerals, such as salts, gypsum, and
  clay.

54
Useful Mineral Substances (2)

• Geochemically abundant metals include
• Iron.
• Aluminum.
• Manganese.
• Magnesium.
• Titanium.

55
Useful Mineral Substances (3)

• Geochemically scarce metals represent less than
  0.1 percent by weight of the crust.
• They are present exclusively as a result of
  atomic substitution.
• Atoms of the scarce metals (such as nickel,
  cobalt, and copper) can readily substitute for
  more common atoms (such as magnesium and calcium).

56
Useful Mineral Substances (4)

• Most ore minerals of the scarce metals are
  sulfides.
• A few, such as the ore minerals of tin and
  tungsten, are oxides
• Most scarce metal deposits form as hydrothermal
  or magmatic mineral deposits.

57
Energy Resources (1)

• The uses of energy can be grouped into three
  categories
• Transportation.
• Domestic use.
• Industry (meaning all manufacturing and raw
  material processing plus the growing of
  foodstuffs).

58
Figure 21.12
59
Energy Resources (2)

• Most energy used by humans is drawn annually from
  major fuels
• Coal.
• Oil.
• Natural gas.
• Nuclear power.
• Wood and animal dung.

60
Fossil Fuels (1)

• The term fossil fuels refers to the remains of
  plants and animals trapped in sediment that can
  be used for fuel.
• The kind of sediment, the kind of organic matter,
  and the processes that take place as a result of
  burial and diagenesis, determine the kind of
  fossil fuel that forms.

61
Fossil Fuels (2)

• In the ocean, microscopic phytoplankton and
  bacteria are the principal sources of trapped
  organic matter that are transformed (mainly by
  heat) to oil and gas.
• On land, trees, bushes, and grasses contribute
  most of the trapped organic matter, forming coal
  rather than oil or natural gas.

62
Fossil Fuels (3)

• In many marine and lakes shales, burial
  temperatures never reach the levels at which the
  original organic molecules are converted into oil
  and natural gas.
• Instead, an alteration process occurs in which
  wax-like substances containing large molecules
  are formed.
• This material, which remains solid, is called
  kerogen, and it is the substance in so-called oil
  shale.

63
Coal (1)

• Coal is the most abundant fossil fuel.
• It is the raw material for nylon, many other
  plastics, and a multitude of other organic
  chemicals.
• Through coalification, peat is converted to
  lignite, subbituminous coal, and bituminous coal.
• Anthracite is a metamorphic rock.

64
Figure 21.13
65
Coal (2)

• A coal seam is a flat, lens-shaped body having
  the same surface area as the swamp in which it
  originally accumulated.
• Coal seams are found in Utah, Montana, Wyoming,
  and the Dakotas.
• Peat formation has been widespread and more or
  less continuous from the time land plants first
  appeared about 450 million years ago, during the
  Silurian Period.

66
Coal (3)

• The greatest period of coal swamp formation
  occurred during the Carboniferous and Permian
  periods, when Pangaea existed.
• These periods produced the great coal bed of
  Europe and the eastern United States.
• The second great period of coal deposition peaked
  during the Cretaceous period but commenced in the
  early Jurassic and continued until the
  mid-Tertiary.

67
Petroleum Oil and Natural Gas

• The major use of oil really started about 1847,
  when a merchant in Pittsburgh, Pennsylvania,
  started bottling and selling rock oil as a
  lubricant.
• In 1852, a Canadian chemist discovered kerosene,
  a liquid that could be used in lamps.
• In Romania in 1856, workers were producing 2000
  barrels a year.
• In 1859, the first oil well was drilled in
  Titusville Pennsylvania
• Modern use of gas started in the early
  seventeenth century in Europe, where gas made
  from wood and coal was used for illumination.

68
Origin of Petroleum (1)

• Petroleum is a product of the decomposition of
  organic matter trapped in sediment.
• Nearly 60 percent of all the oil and gas
  discovered so far has been found in strata of
  Cenozoic age.
• Petroleum migration is analogous to groundwater
  migration. When oil and gas are squeezed out of
  the shale in which they originated and enter a
  body a sandstone or limestone, they can migrate
  easily.
• Because it is lighter than water, the oil tends
  to glide upward, until it encounters a trap.

69
Figure 21.14
70
Figure 21.15
71
Figure 21.16
72
Tars

• Tar is made of oil that is exceedingly viscous
• The largest known occurrence of tar sand is in
  Alberta, Canada, where the Athabasca Tar Sand
  covers an area of 5000 km2 and reaches a
  thickness of 60 m.
• Similar deposits, almost as large, are known in
  Venezuela and in Russia.

73
Oil Shale

• The worlds largest deposit of rich oil shale is
  in Colorado, Wyoming, and Utah.
• Only oil shale that produces 40 liters of oil per
  ton are worth mining.
• The richest shales in the U.S. are in Colorado
  they produce as much as 240 liters of oil per
  ton.
• Production expenses today make exploitation of
  oil shales in all countries unattractive by
  comparison to oil and gas.

74
Other Sources of Energy (1)

• Biomass energy
• Wood and animal dung.
• Hydroelectric power.
• Nuclear energy.
• Heat energy is produced during controlled
  transformation (fission) of suitable radioactive
  isotopes.
• Three of the radioactive atoms that keep the
  Earth hot by spontaneous decay238U, 235U, and
  232Thcan be mined and used to obtain nuclear
  energy.

75
Other Sources of Energy (2)

• Geothermal power.
• Geothermal power is produced by tapping the
  Earths internal heat flux (Zealand, Italy,
  Iceland and the United States).
• Energy from winds, waves, tides, and sunlight
• Winds and waves are both secondary expressions of
  solar energy.
• Winds have been used as an energy source for
  thousands of years through sails on ships and
  windmills.
• Steady surface winds have only about 10 percent
  of the energy the human race now uses.

76
Other Sources of Energy (3)

• Tides arise from the gravitational forces exerted
  on the Earth by the Moon and the Sun.
• If a dam is put across the mouth of a bay so that
  water can be trapped at high tide, the outward
  flowing water at low tide can drive a turbine.

77
Consumption Rates

• In North America, each person uses approximately
  20 tons of crushed rock, cement, sand and gravel,
  fertilizer, oil, gas, coal, metals, and other
  commodities per year.
• For the world as a whole, the consumption rate is
  about 9 tons per person per year.
• About 54 billion tons of material is dug up and
  used each year.

78
Figure 21.20