Transcript Geology and Mining

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
The Earth has 15 major tectonic
plates
Movement of these plates influences climate and evolution
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 Animation
Transport
Erosion
Deposition
Shale, Sandstone,
Limestone
Rock
Cycle
Weathering
Igneous Rock
Granite, Pumice,
Basalt
Sedimentary Rock
Heat,
Pressure
Heat,
Metamorphic Rock
Pressure
Slate, Quartzite,
Marble
Magma
(Molten Rock)
Fig. 16-9 p. 339
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
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
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
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
Nonrenewable
Mineral
Resource
Depletion
Curves
Source: Miller, G. Tyler, Living In The
Environment. (2000) Wadsworth
Publishing. New York.
Steps in Obtaining Mineral Commodities
1. Prospecting: finding places where ores occur
2. Mine exploration and development: learn whether ore
can be extracted economically
3. Mining: extract ore from ground
4. Beneficiation: separate ore minerals from other mined
rock
5. Smelting and refining: extract pure commodity from
the ore mineral
6. Transportation: carry commodity to market
7. Marketing and Sales: Find buyers and sell the
commodity
Environmental Impacts of Nonrenewable Mineral
Resources
Surface mining
Subsurface mining
Overburden
Room and pillar
Spoil
Longwall
Open-pit
Dredging
Strip mining
Refer to Figs. 15-4 and
15-5, p. 341 and 342
Environmental Effects of Mining Mineral
Resources
Disruption of land surface
Subsidence
Erosion of solid mining waste
Acid mine drainage
Air pollution
Storage and leakage of liquid mining
waste
Environmental 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
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 1977
Mine lands must be restored to
pre-mining conditions
Taxes on mining companies to
restore pre-1977 sites
Limited 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)