geology and mining. plate tectonics shapes the earth plate tectonics = process that underlies...
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Geology and Mining
Plate tectonics shapes the Earth
• Plate tectonics = process that underlies earthquakes and volcanoes and that determines the geography of the Earth’s surface
• Crust = lightweight thin component of Earth’s surface
• Mantle = malleable layer on which the crust floats
• Core = molten heavy center of Earth made mostly of iron
Pangaea: the supercontinent
Pangaea = at least twice in Earth’s history, all landmasses were joined in one supercontinent
Earth’s crust is constantly created and destroyed
• Divergent plate boundaries = magma surging upward to the surface divides plates and pushes them apart, creating new crust as it cools and spreads
• Transform plate boundary = two plates meet, slipping and grinding alongside one another– Friction spawns earthquakes
along slip-strike faults
Tectonic plates can collide• Convergent plate
boundaries = where plates collide
• Subduction = one plate of crust may slide beneath another– Magma erupts through
the surface in volcanoes• Two colliding plates of
continental crust may lift material from both plates– Resulted in the Himalaya
and Appalachian mountains
Boundary Interactive
Boundary Animations
The Earth has 15 major tectonic plates
Movement of these plates influences climate and evolution
Fig. 16-9 p. 339Fig. 16-9 p. 339
Igneous RockGranite, Pumice,
Basalt
Sedimentary RockShale, Sandstone,
Limestone
Metamorphic RockSlate, Quartzite,
Marble
Magma(Molten Rock)
WeatheringWeathering
ErosionErosion
TransportTransportDepositionDeposition
Heat,Pressure
Heat,Pressure
Heat,
Pressure
Heat,
Pressure
Rock Cycle
The rock cycle• Rock cycle = The heating,
melting, cooling, breaking and reassembling of rocks and minerals
• Rocks help determine soil chemistry, which influences ecosystems
• Helps us appreciate the formation and conservation of soils, mineral resources, fossil fuels, and other natural resources
Minerals and Rocks• What is a mineral?
– naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure
• What is rock?– solid, cohesive, aggregate of one or more
minerals– Each rock type has a characteristic mixture
of minerals
Igneous rock• Magma = the molten, liquid
state of rock • Lava = magma released
from the lithosphere • Igneous rock = forms when
magma cools• Intrusive rock = magma
that cools slowly well below Earth’s surface (i.e., granite)
• Extrusive rock = magma ejected from a volcano (i.e., basalt)
Sedimentary rock• Sediments = particles of
rock are blown by wind or washed away by water
• Sedimentary rock = dissolved minerals seep through sediment layers and crystallize and bind sediment particles together
• Lithification = formation of rock through the processes of compaction, binding, and crystallization
Formation of sedimentary rock
• Some rock is formed by chemical means when rocks dissolve and their components crystallize to form new rock
• Limestone and rock salt
• Other rocks are formed when layers of sediment compress and physically bond to one another
• Conglomerate, sandstone, shale
Metamorphic rock• Metamorphic rock = great
heat or pressure on a rock changes its form
• Temperatures is high enough to reshape crystals and change its appearance and physical properties
• Marble = heated and pressurized limestone
• Slate = heated and metamorphosed shale
Mining for Ores
An ore is an economically
exploitable deposit
Economic Geology
• What is an economic geological resource?– A mineral that is heavily used in some
human endeavor (e.g., metal ores) and therefore is an important part of domestic/international commerce.
• What are some mineral resources that are economically important?– metals. examples?– non-metal resources. examples?
Economic Geology
• What makes something into an economic resource?
• Are we running out of mineral resources? How would you find this out? What do you need to know??– Total discovered stocks
– likely (but undiscovered) resources
– speculative resources
Mineral Resources
Non-renewable
Mineral Resource Depletion Curves
Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.
1. Prospecting: finding places where ores occur2. Mine exploration and development: learn whether ore can be extracted economically3. Mining: extract ore from ground4. Beneficiation: separate ore minerals from other mined
rock5. Smelting and refining: extract pure commodity from
the ore mineral6. Transporation: carry commodity to market7. Marketing and Sales: Find buyers and sell the
commodity
Steps in Obtaining Mineral Commodities
Environmental Impacts of Nonrenewable Mineral Resources
Surface miningSurface mining Subsurface miningSubsurface mining
Overburden Overburden
SpoilSpoil
Open-pitOpen-pit
DredgingDredging
Strip miningStrip mining
Room and pillarRoom and pillar
LongwallLongwall
Refer to Figs. 15-4 and 15-5, p. 341 and 342
Refer to Figs. 15-4 and 15-5, p. 341 and 342
Environmental Effects of Mining Mineral Resources
Environmental Effects of Mining Mineral Resources
Disruption of land surfaceDisruption of land surfaceSubsidenceSubsidenceErosion of solid mining wasteErosion of solid mining wasteAcid mine drainageAcid mine drainageAir pollutionAir pollutionStorage and leakage of liquid mining
waste
Storage and leakage of liquid mining waste
Environmental DamageEnvironmental Damage• Gaping holes in ground (old open pit mines). • Particulate air pollution• Piles of mine tailings (non-ore removed from mines). • Accidental draining of rivers and lakes. • Disruption of ground water flow patterns. • Loss of topsoil in strip-mined regions (350 to 2,700 km2 in US
alone). • Contamination from sulfuric acid (H2SO4) produced through
weathering of iron sulfide (FeS2, pyrite) in tailings.
4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4
• Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings.
Environmental Effects of Mining Mineral Resources
Environmental Effects of Mining Mineral Resources
Fig. 16-14 p. 344
Surface Mining
Gangue - Mine Tailings
• Worthless minerals that are associated with the valuable minerals in an ore
• Concentrating and smelting removes as much of this gangue as possible
Closeup Image of Mine Tailings
Acid Mine Drainage
Surface Mining Control and Reclamation Act
Established 1977Established 1977
Mine lands must be restored to pre-mining conditions
Mine lands must be restored to pre-mining conditions
Taxes on mining companies to restore pre-1977 sites
Taxes on mining companies to restore pre-1977 sites
Limited successLimited success
Mine Reclamation• Recontouring land back to its original
topography
• Improve soil quality by adding topsoil / nutrients
• Replanting with native, fast growing, early successional species
• Monitor the site for 5 – 10 years
• More difficult in arid areas b/c difficult to grow vegetation
• Mine Albert, Quebec, before and after reclamation. (Government of Quebec)