Metallic Mineral Deposits and Geologic Processes

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Transcript Metallic Mineral Deposits and Geologic Processes

Chapter 21
Mineral and Energy
Resources
PowerPoint Presentation
Stan Hatfield . Southwestern Illinois College
Ken Pinzke . Southwestern Illinois College
Charles Henderson . University of Calgary
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Renewable and Nonrenewable
Resources
Mineral resources
• Canada has a rich supply, but no nation is
completely self sufficient
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Canadian Per Capita Consumption of
Selected Mineral Resources
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Renewable and Nonrenewable
Resources
Renewable resources
• Resource can be replenished over relatively
short time spans
• Examples include
– Plants
– Animals for food
– Trees for lumber
– Energy from flowing water, sun, wind
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Renewable and Nonrenewable
Resources
Nonrenewable resources
• Significant deposits take millions of years
to form; from a human perspective there
are fixed quantities
• Examples
– Fuels (coal, oil, natural gas)
– Metals (iron, copper, uranium, gold)
Some resources, such as groundwater,
can be placed in either category
depending on how they are used
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Metallic Mineral Deposits and
Geologic Processes
Mineral deposits may be found in a variety of plate tectonic settings.
Mineral resources include reserves = identified deposits from which minerals can
be extracted profitably now or in the future with technological advances.
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Metallic Mineral Deposits and
Geologic Processes
Mineral resources
• 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 sulphur
• To be considered of value, an element must be
concentrated above the level of its average
crustal abundance
• Most nonmetallic minerals are generally not
called ores, but rather they are called
industrial minerals
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Metallic Mineral Deposits and
Geologic Processes
Location of important metallic resources in Canada.
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Metallic Mineral Deposits and
Geologic Processes
Magmatic Deposits
• Some of the most important accumulations
of metals are associated with magma that
forms igneous rocks
• Certain metals are enriched in certain
magmas and further concentrated during
cooling of the magma
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Metallic Mineral Deposits and
Geologic Processes
Magmatic Deposits: Gravitational
Settling
– heavy minerals that crystallize early, settle
and concentrate on the bottom of the magma
chamber
High-density minerals sink to
the bottom of the magma
chamber.
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Metallic Mineral Deposits and
Geologic Processes
Magmatic Deposits: Immiscibility
– Separation and non-mixing of liquid phases
of a magma (e.g., Sudbury, Ontario and
Voisey’s Bay, Newfoundland and Labrador)
– Nickel deposits of Sudbury and Voisey’s Bay
have similar origins, but different triggering
mechanisms
A sample of nickel-bearing rock from
Sudbury.
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Metallic Mineral Deposits and
Geologic Processes
Magmatic Deposits: Pegmatites
– Melt remaining in last stages of cooling is rich
in volatiles and rare elements
– Such a melt is very fluid and invades cracks
and results in large crystals
Pegmatites, like these dykes from
Ontario, are felsic composition rocks
that are mined for uranium, thorium,
beryllium, lithium, tantalum,
niobium, feldspar, muscovite…
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Metallic Mineral Deposits and
Geologic Processes
Hydrothermal Deposits
• Hydrothermal Deposits associated with
Igneous Activity
– Among the best known and important ore
deposits, generated from hot-water solutions
– Majority originate from hot, metal-rich fluids
that are remnants of late-stage magmatic
processes
– Move along fractures, cool, and precipitate the
metallic ions to produce vein deposits
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Metallic Mineral Deposits and
Geologic Processes
Hydrothermal Deposits
• Hydrothermal Deposits associated with
Igneous Activity
– Can occur as disseminated deposits, which are
distributed throughout the rock body, rather
than concentrated in veins; called porphyry
deposits = (low grade; large volume)
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Metallic Mineral Deposits and
Geologic Processes
Hydrothermal Deposits
• Hydrothermal Deposits associated with
Igneous Activity
– Volcanogenic Massive Sulphide (VMS)
deposits are pod-shaped bodies composed
entirely of interlocking sulphide minerals
– Heated seawater, rich in dissolved metals
gushing from seafloor as black smokers today,
may have produced VMS deposits in ancient
rocks
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Hydrothermal Deposits at Black Smokers
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Pegmatite and Hydrothermal Disseminated
Deposits
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Metallic Mineral Deposits and
Geologic Processes
Sediment-Associated Hydrothermal Deposits
• Sedimentary Exhalative (SEDEX) Deposits
– SEDEX deposits are thin layers of massive
sulphide interbedded with sedimentary rocks (e.g.,
Sullivan Mine, British Columbia)
SEDEX deposits typically
occur in the sediment fills
of rift basins.
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Metallic Mineral Deposits and
Geologic Processes
Sediment-Associated Hydrothermal Deposits
• Sedimentary-Hosted Stratiform Deposits
– Copper-bearing brines moving through coarsegrained sedimentary rock are forced upward
through oxygen-poor, sulphide-rich mud, which
promotes precipitation of minerals
• Mississippi Valley-type Deposits
– Metal-bearing brines migrate toward basin edge
and react with limestone
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Metallic Mineral Deposits and
Geologic Processes
Sedimentary Deposits
• Banded Iron Formations
– Reducing conditions for much of the early
Precambrian resulted in large quantities of ferrous
iron in solution
– At some point, photosynthesizing bacteria
(cyanobacteria) generated sufficient oxygen to
precipitate insoluble iron oxide minerals
– Form very important source of iron-ore on many
continents including in the Lake Superior region
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Metallic Mineral Deposits and
Geologic Processes
Sedimentary Deposits
• Placer deposits – formed when heavy
metals are mechanically concentrated by
currents
• Examples include
– Gold, Platinum, Diamonds
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Klondike Gold Rush: placer miners with
sluice box in 1901 (right) and modern gold
mining on same creek in 2002 (left)
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Metallic Mineral Deposits and
Geologic Processes
Deposits Associated with Metamorphism
• Many of the most important metamorphic
ore deposits are produced by contact
metamorphism
– Sphalerite (zinc)
– Galena (lead)
– Chalcopyrite (copper)
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Skarns are Associated with
Contact Metamorphism
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Metallic Mineral Deposits and
Geologic Processes
Deposits Associated with Weathering
• Secondary enrichment – concentrating
metals into economically valuable
concentrations
• Bauxite
– Principal ore of aluminum
– Forms in rainy tropical climates from
chemical weathering and the removal of
undesirable elements by leaching
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Bauxite – the principal
ore of aluminum
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Metallic Mineral Deposits and
Geologic Processes
Deposits Associated with Weathering
• Other deposits, such as many copper and
silver deposits, result when weathering
concentrates metals that are deposited
through a low-grade primary ore
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Nonmetallic Resources
Nonmetallic mineral resources
• Use of the word “mineral” is very broad
• Two common groups
– Aggregate and Stone
– Natural aggregate (crushed stone, sand,
and gravel; latter two associated with
glacial outwash deposits throughout
Canada)
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Significant Industrial Mineral Deposits in Canada.
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Nonmetallic Resources
Industrial Minerals
• Diamonds
– Most diamonds are found in unique ultramafic
igneous rocks called kimberlites
– Magma generated by partial melting of
asthenosphere below 150 kilometres and then
rises quickly to the surface, picking up
diamonds from solid lithospheric mantle
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Kimberlite Pipes and
Diamonds
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Nonmetallic Resources
Other Industrial Minerals
• Clays
• Carbonate Minerals
• Evaporite Salts (potash very important
resource in Devonian of Saskatchewan)
• Phosphate (Permian Phosphoria
Formation in Idaho, USA)
• Sulphur
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Nonrenewable Energy Resources
Petroleum: Oil and natural gas
• Origin of petroleum lies in the alteration by
heat of organic-matter concentrated in
source rocks
• Organic matter is transformed into a solid
waxy material called kerogen
• At higher temperatures the carbon-carbon
bonds break in a process called cracking,
eventually producing oil and then gas with
progressively increasing temperatures
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Nonrenewable Energy Resources
Petroleum Migration and Traps
• Petroleum migrates into reservoir rocks until
it is stopped by an impermeable cap rock
• A geologic environment that allows for
economically significant amounts of oil and
gas to accumulate underground is termed a
petroleum trap
– Common oil and natural gas traps include
anticlinal traps, fault traps, and stratigraphic
traps
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Common oil traps – anticline, fault, salt
dome, and stratigraphic
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Nonrenewable Energy Resources
Oil and Natural Gas in Canada
• 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
• Western Canada petroleum, especially in Alberta, is
found in Devonian reefs and Mesozoic sandstone units
• Important petroleum deposits are being exploited
offshore of Newfoundland and Nova Scotia
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Petroleum-bearing areas in NA
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Nonrenewable Energy Resources
Coal
• Formed mostly from plant material
• Along with oil and natural gas, coal is
commonly called a fossil fuel
• The major fuel used in power plants to
generate electricity
• Problems with coal use include environmental
damage from mining and air pollution
• Most Western Canada coal is CretaceousTertiary, but coal of Nova Scotia is
Pennsylvanian (Upper Carboniferous)
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Coal Deposits in Canada
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Nonrenewable Energy Resources
Environmental Effects of Fossil Fuel Use
• Urban air pollution
– Air pollutants are airborne particles and gases
that occur in concentrations that endanger the
health of organisms and disrupt the orderly
functioning of the environment
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Nonrenewable Energy Resources
Environmental Effects of Fossil Fuel Use
• Two types of pollutants
– Primary pollutants - emitted directly from
identifiable sources
– Secondary pollutants – formed when chemical
reactions take place among primary pollutants
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Nonrenewable Energy Resources
Environmental Effects of Fossil Fuel Use
• Carbon dioxide and global warming
– Burning fossil fuels produces carbon dioxide
which is one of the gases responsible for
warming the lower atmosphere
– CO2 is not the only gas responsible for global
warming
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Nonrenewable Energy Resources
Environmental Effects of Fossil Fuel Use
• Carbon dioxide and global warming
– Greenhouse effect – the atmosphere is
transparent to incoming short-wavelength
solar radiation. However, the outgoing longwave radiation emitted by Earth is absorbed
in the lower atmosphere, keeping the air near
the ground warmer
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Heating of the Atmosphere
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Nonrenewable Energy Resources
Environmental Effects of Fossil Fuel Use
• Carbon dioxide and global warming
– It appears that global temperatures have
increased (global warming) due to a rising
level of atmospheric carbon dioxide
– Canada’s target under Kyoto Protocol is to
reduce greenhouse gas emissions to 6% below
1990 levels by 2012
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Annual Average Global Temperatures
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Nonrenewable Energy Resources
Unconventional Fossil Fuel Deposits
• Heavy Oil Sands
– Mixtures of sediment, water, and bitumen (a
viscous black tar-like material)
– Several substantial deposits around the world,
including huge reserves in Alberta
– Obtaining oil from tar sands is costly, but will
play a major role as global conventional
petroleum supplies decrease
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Nonrenewable Energy Resources
Unconventional Fossil Fuel Deposits
• Oil shale
– Contains enormous amounts of untapped oil
– Currently, because of world markets and with
current technologies, not yet economic to
extract
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Unconventional Fossil Fuel Resources in
North America
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Nonrenewable Energy Resources
Unconventional Fossil Fuel Deposits
• Methane Hydrates
– Solid substance with methane surrounded by water molecule
cages
– Found in permafrost and continental shelves
– Currently uneconomic and many environmental concerns
Methane hydrate from 850 metre
deep seafloor west of Vancouver
Island, B.C.
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Nonrenewable Energy Resources
Unconventional Fossil Fuel Deposits
• Coal Bed Methane
– Heating of coaly organic matter liberates methane
– Currently uneconomic and groundwater contamination concerns
Nuclear Energy
– Nuclear fission and CANDU Reactors
– Uranium occurrences
– Obstacles to development
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Renewable Fuel Sources
Organic-Based Sources
– Landfill Methane
– Biomass Energy
Hydroelectric Power
– Generated by falling water
– Canada is a world leader in hydroelectricity
production; most energy produced in large dams
– 62% of Canada’s electricity is hydro-generated
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Electricity Generation Sources in Canada
and a Hydroelectric Dam in Quebec
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Renewable Fuel Sources
Alternate energy sources
• Possible alternate energy sources
– Solar Energy
– Wind Energy
– Geothermal Energy
– Tidal Power
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Solar Panels in Edmonton (left) and a Wind
Farm near Pincher Creek, Alberta (right)
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End of
Chapter 21
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