Chapter 1: Rocks and Minerals Flashcards
1
Q
What is the Structure of the Earth?
A
- Inner Core - 6370km and 5000C+
- Outer Core - 5100km
- Mantle (molten rock) - 2900km and 1600-2000C
- Crust - 0-100km and 0-45C
The crust reflects the temperature on the surface of the Earth. C=degree
2
Q
Peak Mineral
A
Peak mineral is a concept that provides a date after which there will only be less extraction of a mineral; the date at which most mineral is extracted before going into decline.
phosphorous - current estimated 2030
copper - current estimated 2040
uranium - current estimated - 2030s
3
Q
Explain the formation of Igneous Rocks and describe their properties.
A
- When molten rock from the crust and upper mantle cools, igneous rocks are formed
1. Magma (hot liquid rock) found in the upper mantle is usually under pressure from the rocks above it
2. When it cools it forms solid rock; when magma rises to the surface in the form of lava from volcanoes it cools and forms crystals and minerals
3. Crystals are formed when solutions of minerals cannot absorb any more dissolved minerals. Some of each mineral type precipitates to form the centre of the crystal. The crystal becoems larger til lthe solution disappears (crystals found)
4. If the rock cools quickly small crystals are formed, if it rises from the mantle to the crust without reaching the Earth’s surface large rocks can be formed.
5. No fossil fuels found
6. Hard, used in construction
Ex: Granite, basalt
Molten rock is called magma below surface and lava above surface,
4
Q
Describe the formation of Sedimentary Rocks
A
- Are formed by weathering and erosion
- Weathering of existing rocks, fossilised living material, and dissolved materials out of oslution in water.
- Weathering processes: Water and wind erosion etc
- weathering releases small mineral particles ranging from clay, to silt, to sand to larger particles such as gravel, and boulders.
- particles are transported by streams and rivers and deposited as sediment
- layers and layers of sediment are built up and compacted due to ehat and pressure, eventually form rock
- crystals absent, fossils may be present
Ex: limestone, sandstone, shale
5
Q
Describe the formation of Metamorphic Rocks
A
- Fomred when existing rocks are exerted with heat(above 150C) and pressure (above 1480 atm) which cause chemical and physical changes within the rock without melting the rock.
- Igneous, sedimentary, and metamorphic rocks (because the chemical composition changes) can go through these changes and become metamorphic rocks
- Are harder than sedimentary
- mineral crystals are present
- no fossils are present
EX: Marble, slate
5
Q
List the different ways minerals can be detected. Explain the process and provide any perks/disadvantages if possible.
A
- Prospecting- geologists carefully observe the surface of rocks
-
From the air
* Remote Sensing - through helicopter images/aerial photography an area can be carefully analysed for signs of mineral. This can cover more ground.
* Satellite Images - mineral deposits are weathered and produce mineral oxides that may be detected (by satellites) by their unique radiation pattern. Minral ores can be located through satellite images, comouters process data to see the availablity, geologists visit the area for a check. Large areas mapped quickly and at low cost
* Geochemical Analysis - Field surveys on the ground that are sent ot labs for testing so that chemcials are identified. Sample points can be anywhere ranging from streams to soil, and are decided using the Global Positioning System
* Geophysics - A series of vibrations sent through the earths surface; several sensors are laid at differnet distances from the source of the vibrations. The shock waves created travel into the rock layers and reflect back to the sensors. Shock waves record different patterns dependingo n what mineral is present. Explosives may also be used. Overall harmful for environment in many ways
5
Q
Describe Open pit/open cast/open cut mining.
(Surface Mining)
A
- part of surface mining
- used when deposit located near surface
- carefully dug in sections called benches
- the dug out material is called overburden, is stored nearby and later used for mine restoration
- the walls of benches are kept at an angle to reduce rock falls, angle depends on type of deposit and overburden
- roads are made as digigng progresses
- builing materials such as sand, gravel, and stone are removed from pits called quarries
- why some mines stop being worked - as much deposit as possible has been removed - the amoint of overburden that needs to be removed has increased to a point that the mine is not profitable
5
Q
Describe the process of the rock cycle in simple words.
A
- Weathering and erosion break off the fragments of surface rock
- these mineral particles travel and eventually start forming compact layers in areas. As the layers build up the lower layers are compacted into sedimentary rocks
- Sedimentary and igneous rocks are subjeced to heat and pressure formnig metamorphic rocks
- at higher temps the rocks melt to form magma
- magma cools into igneous rock
- movements in the earth raise rocks to the surface via a process called uplift and repeat
5
Q
Describe Strip Mining
(Surface Mining)
A
- used to mine a seam of material
- firstly, overburden is removed
- large bucket wheel excavators are used to remove the mineral
- used when minerla is extremely close to surface
- usually always has reclamation, open pit miens are sometimes left as such
5
Q
Explain Sub Surface Mining
A
- done when mineral deposits are too deep to be removed by surface mining - is relatively expensive
1. Drift Mining - horizontal tunnels are sug directily into the coal seam in the side of a hill or mountain. Miners and machines enter through an adit (entrance to drift tunnel). Sloping tunnels (angle 45) are dug to reach deeper deposits mining machinery lowered down.
2. Shaft Mining - vertical shafts are dug down - horizontal galleries dug into the mine deposits underground machinery is used to excavate - only valuable minerals doen through this - supply of fresh air and water drainage to be provided
- danger of collapsing tunnels, risk of poisonous gas, explosion and underground fire
6
Q
Environmental Impacts of Mining (Ecological)
A
*loss of vegetation - plants loose space to grow - may cause extinction within plant species
* break in ecological system - species relying on plants loose habitat/are driven away by human presence and machines
* overburden and waste stored aboveground will drive away species
* surface mining causes greatest damage - even if restored/filled with overburden - less biodiversity - lost for many years
6
Q
Environmental Impacts of Mining
(Pollution)
A
- Noise - explosive charge in surface mining - mavhinery whirring - can disturb behavious of animal species - cause hearing problems in people - mining licenses usually set limit on levels of noise nad worknig hours of mine
- Water - water can drain through mine waste= dramatic changes in pop of living organisms in streams and rivers - drinking supplies may be polluted - diseases may spread - chemical reactiosn b/w water and exposed waste - water may becoem acidic and dissolve toxic metal ions - kills organisms - bioaccumulation - biomagnification - death rises in the hierarchy
- Land - plants can’t grow - waste may be dumped over natural water courses
- Air - dust particles everywhere - can go in lungs - cause diseases and asthma especially in children - harmful to human skin - can cause plant death - particles settle on vegetation near mine - will reduce plants ability to absorb light and photosynthesise - will eventually wither
- Visual- visual beauty of land destroyed - landscape damaged - may be temporary as restoration may be done later
- Personal Protective Equipment (PPE) given to miners to protect them - safety clothing - masks
7
Q
Informal Mining
A
- doen without a license
- usually small scale
- illegal
- results in health and environmental problems
- common in developing countries with bad accountability systems
8
Q
What are the factors affecting the viability of the extraction?
A
- First resource evaluation done - how much mineral is there? Second feasability study done - to evaluate financial and technical aspects
*The costs of exploration and extraction - Probable cost of extracting one tonne of ore - depends on type of mining method - depends on value/type of ore
Geology - Quality of ore
- size of the deposit - low grade ores with small deporits are left as reserves - small deposits with high grade ores may be profitable - also depends on planned rate of extraction
Climate - climate conditions of area - it can be too hot to work in - or too cold ot work in - or may have unpredictable rains
Accessibility - transport of ore after extraction - cost of building road or rail - links to processing plants - nearest port for export - start up cost to be considered
- for large tonnages such as iron ore - rail transport is the only practical solution - large ships such as bulk carriers also keep costs low
- electricty, water, transport of workers
- may have to do some processing near mine - seperate from waster mineral - high grade ore=higher value
- Direct Shipping Ores (DSO) - do not need processing
Environmental Impact - Have to get licensed by govt
- Have to pay tax
- Environmental Impact Assessment - has to have plan to do as little damage as possible and resotre land - must have detailed plans to control the damage to environmet
Demand and Supply - have to chekc the demand and supply trends of the ore to see if it will have a high value or not
- high world price= deposits can be mined
- high world supply= deposits have lwoer value
- low world price= low value
- low world supply/high demand= very high value
9
Q
What is the difference between greenfield and brownfield sites?
A
- Greenfield - sites that have enver been mined before - chances of fisning a depisit there are low - hence strike rate is low
- Brownfield - areas that have lareayd been mined - usually have a higher strike rate - even low grade deposits can be profitable in future
