Minerals and mining Flashcards
Where do active margins occur?
Where two plates slide towards each other forming either a subduction zone or a continental collision
What are deep marine trenches typically associated with?
Subduction zones
Why is volcanism linked to subduction zones?
Because of the friction and heat from the subducting slab
List the 8 processes in the rock cycle
Weathering produces sediment Sediment transport Sediment deposition Burial and lithification Heat and pressure More heating and melting Cooling and crystalization Uplift and mountain building
Explain the weathering produces sediment stage
Exposure to the elements and mass wasting degrades rock to sediment
Explain the sediment transport process?
This is done by wind, water and waves for example
Explain the sediment deposition process
In floodplains, lakes, alluvial fans, beacjes and the oceans. Also chemical precipitation and accumulation of dead plant and animal material
Explain the burial and lithication proccess
Increased pressure and cemntation transforms sediment to rock
Explain the heat and pressure stage
When the depth of burial exceeds 10km and temperatures are over 300 C minerals in the rock recrystalize to more stable forms (without melting)
Explain the more heat and melting process
From partial melting of the upper mantle, partial melting at the top of a subducting plate, rising convection currents in the mantle or mantle plumes. Heat melts the rocks to form magma
Explain the cooling and crystalisation process
If magma cools slowly deep within the Earth it forms plutonic rock.
If magma comes to the surface and cools rapidly it forms volcanic rock
Explain the uplift and mountain building process
Deformation of crust (lengthening and shortening) caused by movement of plates exposes rocks at the surface of the earth
How are sedimentary rocks made?
From burial and lithification
How are metamorphic rocks made?
From heat and pressure
How are igneous rocks made?
From more heat which causes them to melt and then recrystalise
Where can chalks and cherts be found?
On the deep ocean floor
Where can muds be found?
On the continental rise
Where can sands and muds be found?
On the continental shelf and slope
Where can peats and muds be found?
Peat in swamps
Mud on floodplains
Where can sands be found?
In river channels
Where can gravels be found?
In fans and channels
What are mineral locations often related to?
Active tectonic zones and tectonic zones that were active in the past
What has economical importance?
The trade of minerals
Explain what has happened in terms of mineral rushes?
There used to be a gold rush and other mineral rushes in the past.
There are still mineral rushes today but in different ways
Define mineral
Naturally occurring, inorganic substances that possess a definite chemical composition and characteristic atomic structure
What sort of structure do most minerals have?
A crystalline structure
Define rocks
Minerals are combined into rocks so they are an assemblage of minerals in the solid state
What are the three types of rock?
Metamorphic
Sedimentary
Igneous
What types of rock only contain one mineral?
Limestone and quartzite
What is granite a mixture of?
Mica, feldspar and quartz crystals
What is a mineral?
An element or inorganic compound that occurs naturally in the earth’s crust as a solid with a regular internal crystalline structure
Name 3 minerals that only contain one element
Gold
Silver
Diamond
How many minerals are there?
Over 2000
What is salt?
A mineral made of sodium chloride
What is quartzite?
Silicon dioxide
How can the reserve size be calculated?
Using maths
What used to be thought about reserves?
They were thought to be huge
What issues are there with open cast mining?
Environmental issues
What has changed since mining began?
There have been changes in the way we mine, we used to send people down
Where does open cast mining take place?
Below the water table
what is an issue with open cast mining?
Groundwater can become toxic
What happens to some areas after mining?
They are re-landscaped
What are the 4 ways in which mineral resources can be categorized?
Identified
Undiscovered
Reserves
Other
What is meant by identified?
Known location, quantity and quality or existence based on direct evidence and measurements
What is meant by undiscovered?
Potential supplies that are assumed to exist
What is meant by reserves?
Identifies resources that can be extracted profitably
What is meant by other?
Undiscovered or unidentified resources not classified as reserves
What needs to be considered before mineral extraction?
Costs
Safety factors
Levels of environmental harm
What is surface mining?
Shallow deposits are removed
What is subsurface mining?
Deep deposits are removed
What are 3 issues with subsurface mining?
Leaves some resource behind
More dangerous
Expensive
What is an advantage of subsurface mining?
It impacts less terrain
What happens in open cast mining?
Holes are dug and ores, sand, gravel and stone are removed
How does area strip mining take place?
Earth movers strip away overburden, and giant shovels remove mineral deposit.
What are spoil banks?
Highly erodible hills of rubble
What type of mining creates spoil banks?
Area strip mining
Contour strip mining
Where does area strip mining usually take place?
Usually on hilly or mountainous terrain
What is left behind if the land is not restored in area strip mining?
A wall of dirt is left in front of a highly erodible bank called a high-wall
What is contour strip mining?
This cuts terraces around the side of a hill, also leaves a high wall
What are 6 environmental impacts of mining?
Acid mine drainage Erosion and sedimentation Cyanide and other toxic releases Dust emissions Habitat modification Surface and groundwater contamination
How is metal extracted from its metal ores?
Metal ores are smelted or treated with potentially toxic chemicals to extract the desired metal
What is subsidence?
A phenomenon where the surface collapses directly above a subsurface mine
What are spoils?
The unwanted rock and other waste left over after mining either on the surface or subsurface
What are tailings?
These are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore
What has happened as a result of mining in the US?
More than 500 mountain tops have been removed to extract coal and the resulting spoils have buried more than 1100km of streams
What is an issue with sub-surface mining in tropical areas?
It destroys and degrades vital biodiversity when forests are cleared and rivers are polluted with mining wastes
Which toxic waste material can cause poisoning and irreversible brain damage in children?
Lead dust
How does acid mine drainage occur?
Rainwater seeps through a mine or a spoils pile carries sulfuric acid to nearby streams and groundwater
What percentage of watersheds have been polluted by mining in the USA?
40% of western watersheds in the USA
What proportion of all US emissions of toxic chemicals into the atmosphere does mining account for?
50%
Where does much of the degradation come from?
Leaking storage ponds that were built to hold toxic sludge that is produced from mining and processing of metal ores
What steps are involved in mining production?
Mining - exploration, extraction
Processing- transportation, purification, manufacturing
Use- transportation or transmission to individual user, eventual use and discarding
The energy used to carry out these actions also has environmental impacts
Explain ideas relating to depletion
Depletion curves for a renewable resource use three sets of assumptions
How can the environmental impact of mining be minimised?
Scientists and engineers are developing new types of materials as substitutes for many metals
Recycling valuable and scarce metals saves money and has a lower environmental impact than mining and extracting them from their ores
What does the future of a resource depend upon?
Its affordable supply and how rapidly the supply is used
What can a rising price do for a scarce mineral?
It can increase supplies and encourage more efficient use
What costs should be included in the price to make the use of non-renewable minerals
Include the harmful costs of mining and processing minerals in the prices of items
How can the government reduce the environmental impact of mining?
Reduce mining subsidies
How can manufacturing processes improve the environmental impact of mining?
Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste
What are 6 minerals that could be extracted from the oceans?
Iron Sodium chloride Manganese on the deep ocean floor Diamond Magnesium Bromine
What does hydraulic fracking often involve?
The injection of more than a million gallons of water, chemicals, sand and high pressure down the well
Why is pressurised fluid inserted into fracking wells?
It causes the formation to crack, allowing natural gas or oil to flow up the well
What is meant by water acquisition?
Large volumes of water are transported for the fracturing process
What is meant by chemical mixing?
Equipment mixes water, chemicals, and sand at the well site
What is meant by well injection?
The hydraulic fracturing fluid is pumped into the well at high injection rates
What is meant by flowback and produced water?
Recovered water is stored on-site open pits or storage banks
What is meant by waste water treatment and waste disposal?
The wastewater is then transported for treatment and/or disposal
How can drinking water get fracked?
Toxic chemicals from fracking seep into the bedrock and seep up into drinking aquifers which then enters water drinking systems
