The Lithosphere

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The Lithosphere
Mineral Resources Reserves and
resources Environmental impacts of mineral
exploitation The Rock Cycle
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Mineral Resources
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Geological origins

• Rocks are made of minerals e.g.

Granite
Sandstone
Shale
We obtain important metals e.g. iron, lead and
copper from ores rocks that contain sufficient
metal that it is economically worthwhile
extracting and processing them Minerals are not
spread equally throughout the crust Geological
processes concentrate minerals and metals in
particular locations
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Geological processes
Concentration method Example
Granite batholiths form when magma forces its way upwards through the surrounding rocks and then cools 5-30 km below the surface. Hot (hydrothermal) fluids from the magma penetrate fissures in the country rock and different mineral precipitate out at different temperatures Copper, zinc, lead
When basic when magma cools, the heaviest minerals sink fastest and form bands in the subsequent rocks Nickel Iron Titanium
Weathering removes soluble minerals, leaving insoluble minerals behind Bauxite
Minerals are transported by running water. As water velocity slows, the heaviest minerals e.g. gold sink and become concentrated. Lighter minerals are transported further. Minerals concentrated in this way are known as placer deposits Lead Gold
Water evaporates from saline brines, leaving salt deposits to precipitate out evaporites Salt
Accumulations of dead remains of organisms become compacted over millions of years Coal and limestone
Metamorphic activity. Igneous and sedimentary rocks are subjected to great heat and pressure and their minerals realign Limestone is converted into marble Shales are converted into slate
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Where are the minerals found?

• At the margins of tectonic plates e.g.
• Constructive plate margins sulfides
• Destructive plate margins copper
•  

N. America Plate
Eurasian Plate
Pacific Plate
Arabian
Indian
Nazca Plate
Australian Plate
S. America Plate
Africa Plate
Antarctic Plate
Hotspots
Porphyry copper deposits
Subduction zone
Within plates evaporites and placer deposits
Insert image of copper deposits Change label to
subduction zone at destructive plate margin Diag
from http//geoinfo.amu.edu.pl/wpk/pe/a/harbbook/c
_xi/chap11.html
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Reserves and resources
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Reserves and resources

• Minerals non-renewable resources
• Mineral availability determined by
• Location
• Chemical form
• Purity
• Availability of suitable technologies
• Resource
• Naturally-occurring substances that are known or
  are thought to
• exist in concentrations that make extraction
  commercially
• possible either now or in the future.
•  
• Reserve
• The quantity of a resource that can be extracted
  profitably under
• existing conditions. The mineral e.g. copper must
  be at a
• concentration higher than the cut-off grade. The
  reserve is a
• subset of the resource

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Reserves and resources
Click Here
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To exploit or not exploit?
Factor Considerations
Mining costs Depth of deposit Concentrated or disseminated?
Processing costs How much waste rock will there be? How much overburden needs removing?
Chemical form How much crushing will be needed? Will electrolysis be required?
Purity Greater purity lower processing costs
Land costs Derelict land may be cheaper than prime agricultural land
Conflict Is the area in a National Park? Are there wildlife designations on the land?
Transport costs Of both the ore and the waste rock
Cut-off grade The lowest percentage or mineral in a rock that is worth exploiting. This is influenced by market demand for the mineral
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Advantages and disadvantages of underground mining
Advantages Disadvantages
No dust pollution from the mining activity itself Expensive construction costs
Reduced noise pollution Subsidence / collapse
Visual pollution reduced as only wheel house is built on surface Flooding of chambers would need pumping and lowering of the water table
Little land take or loss of habitats When metals / coal is exposed during mining trapped gases can escape there is potential for explosion and the mine needs ventilation
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Quick Quiz
Which deposit is likely to be the most expensive
to extract?
A
B
C
The correct answer is C
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Extraction

• There are 3 main methods of extracting these
  minerals
• 1. opencast mining or quarrying e.g. gravel
• 2. underground mining e.g. limestone in Dorset,
  coal in S. Wales
• 3. washing out a weak mineral using hoses e.g.
  china clay

CHINA CLAY EXTRACTION
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Opencast mining or Quarrying
Firstly, the overburden is removed and stored
around the site these bunds (heaps) absorb noise
Secondly, the economic mineral is extracted using
bulldozers
Sand and gravel extraction, Colchester Quarry
Quarrying or open cast mining is defined
as? rock or stone exposed at the surface which
is simply dug or blasted out
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China clay extraction

• As China Clay is very soft and loose it can be
  washed out with hoses

China clay is washed out with hoses
China clay is dug out and sold
Clay settles to base of tailings ponds
Clear water is released to rivers
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Superquarries

• What is a Superquarry?
• A large scale quarry 6 Scottish superquarries
  can represent 45 inland quarries or 450 sand and
  gravel pits!
• The quarried material is taken away by ship
• What is the advantage of a superquarry compared
  to several smaller quarries?
• Only one large area affected instead of 10 areas
• Improves the economy of rural areas
• Operate in remote locations so has little
  disturbance to people

Distribution of Superquarries
Discuss the distribution
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Advantages and disadvantages of open cast mining

• ADVANTAGES

• DISADVANTAGES

Loss of land (land take) which could be used for
other purposes e.g. agricultural land lost
Cheaper building and construction costs (compared
to underground mining)
Loss of habitats and potentially rare species lost
Less dangerous operations as any gases (e.g.
methane) within the deposit can escape and not
build up to explosive levels
Quarries can be used for landfill there is a
urgent need for more landfill space
Visual and noise pollution to nearby residents
Explosions cause vibrations and dust pollution is
high
Creation of new habitats after mining e.g.
construction of a nature reserve or reservoir
Loss of public rights of way e.g. footpaths
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Underground mining

• This can also be called deep shaft or adit mining

Shaft in Cornwall
Horizontal tunnels or adits branch off the main
shaft
ORE
A main shaft is sunk
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Advantages and disadvantages of underground mining

• ADVANTAGES

• DISADVANTAGES

Expensive construction costs
No dust pollution from the mining activity itself
Subsidence / collapse
Reduced noise pollution
Flooding of chambers would need pumping and
lowering of the water table
Visual pollution reduced as only wheel house is
built on surface
When metals / coal is exposed during mining
trapped gases can escape there is potential for
explosion and the mine needs ventilation
Little landtake or loss of habitats
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Environmental Impacts
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Environmental impacts

• All extraction methods create environmental
  impacts. Most are negative but there are positive
  impacts that occur AFTER extraction has ceased.
• The first major impact is?
• 1. Loss of land (landtake)

The tailings ponds of Wheal Jane mine in
Cornwall. These take up a large area of land that
could potentially be used for other uses, such as
agriculture.
A tailings pond an area where the waste clay
minerals are washed into this allows them to
settle
Wheal Jane Mine
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Environmental impacts

• 2. Scarring of the landscape (an eyesore)

Large spoil heaps of waste material
Unvegetated slopes due to acidity and heavy metal
content
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Environmental impacts

• 3. Loss of habitats
• 4. Reduction in species diversity and potential
  loss of rare species

Agricultural land is cleared for the open cast
mine
Hedgerows and woodlands lost
Barren, acidic soil supports little life
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Environmental impacts

• 5. Drop in water table to prevent quarry flooding

Colchester Quarry in Essex is 1m below the water
table and needs to be pumped
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Environmental impacts

• 6. Subsidence or collapse of underground mine
  tunnels

Land around the shaft has begun to sink
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Environmental impacts

• 7. Explosions from blasting can cause cracks to
  appear in buildings
• 8. Noise pollution from vehicles and machinery

Mechanical joints
Engine
Friction between wheel shafts
Can you identify the sources of noise?
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Environmental impacts

• 9. Vehicle emissions e.g. CO2, SOx
• 10. Traffic congestion as quarried / mined
  material is transported on public roads

Vehicles used to extract the loose sand and
gravel. All of these burn fossil fuels (diesel)
and therefore release CO2, NOx and SOx gases and
particles
Colchester sand and gravel quarry, Essex
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Environmental impacts

• 11. Dust pollution from workings
• 12. Dust can be washed into water courses and
  increase turbidity

Dust stirred up by workings
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Environmental impacts

• 13. Metals can be dissolved and carried into
  rivers and estuaries

This is much more common in metal mining but
could potentially occur if there were metals held
within the limestone or granite
Dissolved iron within Restronget Creek, Cornwall
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Positive environmental impacts

• 14. New habitats, and new recreation and tourism
  activities can be created through reclamation

Reed beds planted and ponds created
The Eden Project, St Austell has been built
within a reclaimed China Clay pit
New RSPB reserve at Hayle, Cornwall built on
reclaimed contaminated mining land. New habitats
have been created to attract migratory waterfowl.
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Reducing the impacts
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The future of mineral supplies

• Minerals are non-renewable resources. There is a
  finite supply.
• CASE STUDY COPPER

Reserves the amount of copper that has been
discovered and is profitable to exploit given
current conditions e.g. copper price, state of
technology   Resources Reserves the copper
in known deposits that are uneconomic to exploit
undiscovered deposits
The US geological survey (2006) estimates world
copper reserves 470 x 106 tonnes world copper
reserve base at 940 x 106 tonnes world copper
resources (which includes reserves ) at 3.7 x 109
tonnes resource base (includes reserves and
resources) 1.5 x 1015 tonnes
Over time, copper moves from resource to
reserves, then to the stock of copper in use,
and finally from the stock of copper in use to
waste sites.
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The future of mineral supplies
How do reserves increase? 1. Exploration finds
new economic deposits 2. Improved technology make
previously known but uneconomic resources
profitable to exploit.
Year Copper Reserves (mt) Mine production (mt) Ratio of reserves to mine production
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 91 146 154 195 280 408 350 340 326 348 340 470 2.38 2.90 3.94 4.66 5.90 6.74 7.20 7.99 9.20 10.00 13.20 14.90 38 50 39 42 47 61 49 43 35 35 26 32
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The future of mineral supplies

• Both reserves and mine production have expanded
  rapidly
• It is usually cheaper to wait for improved
  technology than to try to find new reserves
• World copper mine production increased from 0.3kg
  per person to 2.2 kg per person over the 20th
  century - a 7 fold increase.
• But, there is a finite amount of all minerals and
  we need to make sure we maintain supplies of
  minerals for as long as possible

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Strategies for extending the time period of
exploitation
Strategy Explanation
Remote sensing Satellites or aircraft can measure reflectivity of ground surface or the thermal emissivity of rocks which enables precise identification of minerals. This cuts the area of land on which geochemical surveys are needed
Geochemical methods Chemical tests identify which areas contain above-average concentrations of a mineral
Improved extraction and /processing Improved technology has enabled exploitation of previously inaccessible deposits and economic processing of very low grade ores
Recycling Always cheaper than finding, extracting and processing virgin ore
Resource substitution The US Army have started using ceramic components, able to withstand high temperatures and resistant to corrosion, instead of increasingly expensive chromium and cobalt