Environmental AS - The lithosphere (Mineral resources (Resources, reserves…
Environmental AS - The lithosphere
The geological origins of economically important minerals
Resources, reserves and exploitation
Minerals are non-renewable resources.
Economically recoverable resources account for a tiny proportion of the total that exists.
Main limitations on mineral availability are the locations, chemical form and purity of the deposits, and the availability of technologies to exploit them.
Their exploitation is economically important but can cause environmental damage.
- the total amount of a material that could theoretically be exploited.
- the proportion of a resource that can be economically exploited with existing technology.
Factors affecting mine viability:
Mineral deposits are likely to be mined if sufficiently profitable with no prohibitive environmental, political or social problems.
Profitability of mining is simply the difference between the income from selling the processed mineral and the total costs of extracting and processing it.
The only place you can mine minerals is where they are found.
If competing land uses are considered more important or valuable than mining then the deposit may not be exploited.
Deposits below urban areas not usually mined as relocation costs are too high.
Areas with high landscape or wildlife conservation value may also be protected, although not always important in all countries.
Mining costs rise rapidly as depth increases.
The sides cannot be vertical due to collapse risk so the amount of rock removed to reach minerals rises rapidly with depth.
Loose overburdens mean the gradient must be more gentle, increasing costs further.
The rock above the mineral that must be removed.
If too hard, it'll be blasted instead of removed.
Form of the mineral deposit:
Mining costs increase if the mineral is found in thin layers or if it is dispersed in an irregularly shaped deposit.
Both problems increase the size of the mine void to be excavated.
As depth increases, amount of water that flows into the mine also rises.
Pumping costs can be high.
The chemical form of the mineral:
Cost of extraction depends on the other elements combined with the metal.
More energy is needed to break the bonds, the more expensive extraction will be.
Financial cost of metal extraction increases rapidly as ore purity decreases.
A greater quantity of rock must be extracted and more energy is required to chemically separate the metal from its ore.
Cut-off ore grade is the lowest ore purity that can be exploited economically.
Deposits below this are not included in the reserves so, as prices fluctuate, the quantity of mineral in the reserves also changes although the amount of material that exists does not.
Distance to market, the ease of bulk transport and the presence of a suitable existing transport infrastructure all affect transport costs.
Transporting minerals longer distances increases costs, but the unit costs go down if bulk transport by rail or large ship is possible.
If an existing transport system is there, the set-up costs are lower and processing the mineral before it is transported reduces the bulk needed to be moved.
Market demand and sale value of minerals control the economic viability of exploiting particular mineral deposits.
Market price is controlled by demand for the mineral and how much is produced by mines.
Supplies rise and fall relatively slowly as mines are developed, but demand can rise and fall quickly.
This mismatch can cause prices to fluctuate widely.
Exploiting deposits in regions that already have mines is easier due to easy access to the existing infrastructure for transport, energy, equipment supplies and a trained workforce.
The environmental impacts of mineral exploitation
Turbid drainage water
Caused by drainage water pumped out rapidly or stored behind poorly constructed dams.
Can be reduced by containment in lagoons behind well-constructed dams with carefully timed releases.
Water that flows into abandoned mines may overflow into a river carrying dissolved toxic metals and acids.
Loss of species where mineral is to be extracted is unavoidable.
Capturing animals and transplanting plants to move them to unthreatened habitats rarely completely successful. Areas are either unsuitable or already fully populated.
Habitat restoration or creation of new habitats is a requirement for mining planning permission.
Loss of amenity
Caused by poor spoil compaction or undermining sensitive surface land uses by deep mines.
Reduced by compaction of spoil and by leaving support pillars in deep mines.
Land take - land area required is larger than the area of the mine void.
Land needed for associated buildings, access routes, overburden dumping and possibly a buffer zone.
Congestion and road traffic from mine.
Reduced by using routes to avoid urban areas, building separate access routes or using alternative transport methods.
Marine seismic surveys cause loud vibrations and can disturb whales.
Exploration on land can involve land clearance and vegetation loss.
The future of mineral supplies
Better exploratory techniques
Exploitation of low grade ores
Mechanised mining techniques
The nitrogen cycle
Major processes in the nitrogen cycle:
Chemical reduction of nitrogen to ammonia
Plant roots absorb nitrogen
The effects of human activities on the nitrogen cycle:
The Haber process
Use of nitrate fertilisers
Soil disturbance by ploughing
Soil disturbance, changes in moisture content and aeration
Release of NOx into the atmosphere
The phosphorus cycle
The carbon cycle
Major processes in the carbon cycle:
Combustion of wood and fossil fuels
Human impacts on the carbon cycle:
Combustion of fossil fuels
Coal mines and gas and oil processing
Combustion of wood during deforestation
Anaerobic gut bacteria in livestock intestines
Anaerobic bacteria in rice padi fields
Soil disturbance by ploughing
Global climate change
The components of soil
Air in the soil
Dead organic matter
The mineral skeleton of the soil
The effect of soil properties on soil fertility and productivity
Water drainage, infiltration and retention