Unit 3 Topic 1 - Non-renewable Resources Flashcards
What is step one in hydrothermal mineral generation?
- Hydrothermal fluids are generated. These are enriched with various dissolved minerals and metals due to their interaction with rocks and minerals as they circulate in the crust.
How are magmatic (igneous) minerals formed?
Typically found where crustal plates have converged, the friction between the plates causes the water saturated crust to melt 15-30km below the surface.
As it melts it forms large magma chambers which cool and crystallise, allowing dense metal oxide minerals and some sulfide minerals to sink to the bottom where they form layers
What are alluvial deposits?
Some rocks containing gold veins are exposed to the surface and eroded over time.
The eroded gold is washed down creeks to form alluvial (placer) deposits.
Since gold is typically heavier than most sediments in the creek, it can be trapped in the bed of the river.
How is coal formed? (Asking the real tough questions here)
When abundant plant material is covered by sediments and faster than it can decay.
The weight of the layering sediments compacts the organic layers, increasing temp and pressure. This causes water, carbon dioxide and methane to be produced and escape, making the material more carbon enriched.
Over time, the material progresses through different stages/types of coal as heat and pressure increases
What is step two in hydrothermal mineral generation?
- Fluids migrate through fractures and pore spaces due to pressure gradients, temperature gradients and rock permeability. As fluids circulate they can dissolve minerals from the host rocks.
What is step three in hydrothermal mineral generation?
- Mineral precipitation: Hydrothermal fluids may reach a point where dissolved minerals become supersaturated and precipitate forming solid minerals.
What is step four in hydrothermal mineral generation?
- Ore mineral deposition: During precipitation, certain minerals with economic value can accumulate to form ore deposits.
What are the stages/types of coal
- Anthracite: Contains 86-97% carbon and generally has the highest heating value of all coal types.
- Bituminous: Contains 45-86% carbon
- Subbituminous: Contains 35-45% carbon
- Lignite: Contains 25-35% carbon
also peat, its the lowest carbon content its basically just rotting plant matter buried in the mud
How is petroleum (Crude oil and Natural Gas) formed?
When marine plants and animals die and fall to the sea floor, where they are buried by layers of silt, sand and rock.
Heat and pressure then turns these remains into crude oil or petroleum.
What are anticline traps
Rock layers that were originally horizontal are folded upwards into an arch.
Since hydrocarbons are lighter than water, they rise to the top until they reach an impermeable layer.
What Non-Metallic resources are there
Mineral sands - Ilmenite, rutile and zircon
Evaporites - Dissolved chemicals such as salt is carried down to lakes where intense heat evaporates the water, leaving the chemicals behind.
What are some remote sensing techniques and why are they used?
Satellite imagery
Conventional and infra-red aerial photography
airborne geophysical surveys
They are cheaper in general and allows larger areas to be surveyed quickly in comparison to ground surveys.
What is geochemical halo and how is it used to find deposits?
When a mineral deposit forms, it contains higher than normal concentrations of metals and other elements. These are found in gradually decreasing concentrations surrounding the deposits. This halo formed around the deposit can be found through various chemical samplings allowing geologists to pinpoint possible deposits.
What metal halo is formed around gold deposits?
Arsenic
What main geophysical techniques are there for finding minerals?
Magnetic: Detects various iron ores, titanium ores and nickel ores based on the magnetic field strength changes above the rocks.
Gravity: Detects mostly petroleum. Dense (or less dense) masses modify the gravitational field.
Electric: Detects base metals and iron. AC voltages are applied to the ground to detect a current.
Seismic: Detects mostly petroleum with ore bodies surrounding it. Soundwaves are reflected between rock layers and faults in the ground.
What is strip mining and when is it used?
Overburden is removed and the mineral such as bauxite is removed by excavators. Used when minerals are near the surface.
What is open pit mining and when is it used?
Involves removing the overburden and creating pit benches which spiral the pit enabling large vehicles to travel deeper.
It is used when mineral resources are around 200 metres from the surface.
What is dredging?
The underwater excavation of placer deposits. Uses small dredges to suction up mined material from the bottom of a water body.
This material is fed into a hopper (minecraft) that feeds the separation plant on the dredge where it is sived and sluiced numerous times.
What is Stoping and Room and Pillar
Stoping is the opening of large underground rooms or stopes by excavating ore. Practiced when the surrounding rock is strong enough to permit drilling, blasting and removal without caving.
Room and pillar mining involves pillars of ore being left standing to support the rock.
What is underground mining?
A horizontal shaft called a drive is sent into the ore body where ore is extracted.
Underground mines also need a ventilation shaft where air enters the decline and exits the vent shaft.
Similar to minecraft strip mining overall (Not to be confused with irl strip mining).
What is beneficiation?
A separation technique used to separate the mineral from the gangue.
Large rocks are broken into small lumps while ball mills crush these small lumps into fine particles.
The minerals are sent to a refinery where the metals are removed and the gangue is transported to the tailings dump.
What is froth floatation?
Crushed grains of ore are mixed with detergent-like chemicals that form a froth when agitated.
The ore sticks to the bubbles and rises to the surface where it can be removed while the gangue sinks and collected in a tailings dam.
Used almost universally in the base metal industry and some coal separation.
How is copper generally extracted/separated?
Copper electrolysis, where blister copper in the anode is deposited in the solution while the pure copper is deposited on the cathode.
Impurities such as gold and silver fall to the bottom.
After many days the cathode is removed from the tank and pure copper is stripped off.
What is sluicing?
The use of gravity and density to separate gold from debris.
The collection of debris is fed into the top of the sluice box, where it travels through water and gets trapped in different catchments. Since gold is quite dense it will get caught earlier.
What methods are used for coal separation?
Dense media separation (Sink float): Where the crushed coal and waste rock is added to a high density fluid. The coal floats while the waste rock sinks.
Dense media cyclones: Where the same as above occurs but the liquid is forced into a cyclone. The denser waste rock moves to the outside and slides to the bottom while the coal moves to the centre and leaves through the top.
Froth floatation: Where the coal sticks to bubbles formed by a detergent and rises to the surface.
Explain fracking
Used to extract petroleum from hard shale rock deep below the surface. Cracks both in and below the surface are opened and widened by injecting water, chemicals and sand.
A water tube extracts the petroleum and natural gas and pumps it to the surface.
What environmental factors are monitored to minimise impacts?
Air quality
Water quality (pH, turbidity, dissolved oxygen)
Soil quality (pH, erosion, soil structure)
Noise pollution
