Lecture 21 // Geological Resources Flashcards
Geologic resources
Mined/extracted non-renewable materials.
– They are consumed faster than they are naturally replenished.
Mineral resources
– Construction minerals (e.g., gravel, dimension stone)
– Agricultural minerals (e.g., potash)
– Industrial minerals (e.g., iron, gold, diamonds)
@gravel pit
Energy resources
– Coal
– Oil & natural gas
– Uranium
@ Hibernia offshore drilling platform, Grand Banks, NS.
Potash
• K-containing salts, such as sylvite (KCl) are used in the making of fertilizer. Canada is the biggest producer, with mining operations in
Saskatchewan.
• During the Devonian (~400 Ma) low-lying areas of Laurentia (N.A. + Greenland) were covered by an epicontinental sea. Salts were deposited within reef- closed, hypersaline lagoons.
Gold
Formed as veins within fractured crustal rock, deep underground.
Gold is mined / collected by either:
• Hard-rock mining - in situ mining of the host rock called ore, and physically separating the gold from the gangue (waste rock).
• Placer-deposit mining – gold pan /sluice
Diamonds
Formed in the uppermost mantle and brought surface ward by deep-seated, pressurized, fissure eruptions.
• The eruption forms a carrot shaped kimberlite pipe that is filled with crystallized magma – which may contain mantle diamonds as xenoliths.
Fossil fuels
Concentrated forms of burnable carbon contained in rock.
• coal, oil, natural gas (methane)
• 85% of Global energy consumption comes from fossil fuels.
Coal
- l forms from the partly decomposed plant material that accumulates in swamps and bogs.
- Over time the compressed and heated organics are converted to coal, through a number of stages.
Coal is used to:
- Generate electricity
- Concrete and paper industries use coal to produce heat
- Use the coke coal to give strength to bridges and buildings
- Create synthetic fuels
Oil and natural gas (methane)
Forms of burnable carbon created by the degradation and transformation of accumulated organic material.
– The difference lies in the type of organic material. Oil and natural gas form from organic shales generated by the accumulation of microscopic plankton remains.
Largest producers of oil & gas: [2015 Stats]
- U.S.
- Russia
- Saudi Arabia
- China
- Canada
Organic shale
The source rock where hydrocarbons are generated at certain burial temperatures.
• The temperature and type of biomass present determines the type of hydrocarbon that forms (oil/methane).
Hydrocarbons
Less dense than the surrounding rock and thus migrate upwards.
• Hydrocarbons either seep out at the Earth’s surface, or more likely they encounter a trap along the way.
Energy Resources: Oil & Natural Gas
• Traps occur beneath impermeable layers (creating a ‘seal’) called cap rocks.
• Hydrocarbons are tapped into within ‘plays’ - the uppermost portions of the porous & permeable reservoir rocks.
– Typical plays include anticlines, domes, and fault bounded traps.
– Accessing oil and gas from porous & permeable reservoir rocks is termed conventional oil & gas.
Unconventional oil & gas: ‘Tight oil & gas’
Unconventional oil & gas has become especially important in the past two decades.
‘Tight oil & gas’ come from impermeable units (cap rocks!).
• These units have poorly connected pore spaces. In order to get the shale oil and shale gas out, artificial permeability is generated through hydraulic fracking.
Unconventional oil & gas: ‘oil sands’ or ‘tar sands
Unconventional oil & gas has become especially important in the past two decades.
Semi-consolidated sandstone layers contain degraded bitumen and are mainly accessed through large open-pit mines.
• The mined rock is brought to an on-site steamer where the bitumen is separated from the clean waste rock (sand).
Bitumen can also be collected from the subsurface requiring significantly more expensive SAG-D (steam-assisted, gravity-driven) technology.
