Earth Materials and Natural Resources Flashcards
Define Open Cast Mine
Takes place from quarries of ‘open pits’ at the surface. Overburden is removed
Define Deep Mine
Mining deep within the earth. Drill vertically down with the overburden in place
What are the three types of deep mine?
Longwall, Pillar and stall, Bell pit
What are four geological hazards associated with coal extraction?
Mass movements, Gases, Subsidence, Acid Mine Drainage (AMD)
What are six environmental issues associated with coal extraction?
Change in water table and water quality, Noise, Loss of habitat, Visual impact, Air quality, Transportation of material out of the mine/quarry
What are five factors affecting the accuracy of estimation in the size of the coal deposit?
Bed geometries, Folds, Erosional features, Faulting, Previous mining
Define Source Rock
Sediment that contained the plankton - where the hydrocarbon is made/comes from
Define Reservoir Rock
Permeable and porous rock which the hydrocarbons collect in e.g. sandstone
Define Cap Rock
Impermeable rock on top of reservoir rock which stops upwards migration of oil and gas
Define Trap
Geological structure which stops the oil from migrating
Define Oil Window
The right conditions for the organism to break down into petroleum
Why is Darcy’s Law useful to oil and gas extraction?
It calculates the flow rate of the hydrocarbons in the reservoir rock
What are the four types of hydrocarbon trap?
Anticline, Fault, Salt dome, Stratigraphic
What are two potential problems associated with fracking?
Linked to low magnitude earthquakes, Ground water pollution
What are four surveys used to prospect for hydrocarbons and coal?
Seismic methods, Magnetic methods, Gravity methods, Fossil identification
What are the two types of microfossil?
Calcareous (foraminifera and coccolithophores) and palynomorphs (pollen, dinoflagellates and spores)
Define Average Crustal Abundance
The amount of metal in ‘average’ continental crust
Define Concentration Factor
The amount by which the metal is concentrated to make an ore deposit
Concentration Factor =
Concentration of metal in ore/Average crustal abundance
Define Grade
The concentration of valuable mineral within an ore
Define Cut-Off Grade
The grade below which it is uneconomical to mine
Define Ore Deposit
An accumulation of metal that may be economic to mine
Define Ore Reserve
The rock containing valuable metal which is economic to mine
Define Metallic Ore
Rock containing metallic ores which is economic to mine e.g. galena
Define Native Metal
Pure metal - hasn’t been bound with anything else e.g. gold
Define Gangue Metal
A low-value waste mineral
Define Mineral Vein
A layer/sheet of material that contains minerals
Define Syngenetic
Deposits formed at the same time as the country rock
Define Epigenetic
Deposit formed after the country rock
Define Total Reserves
Can be worked at a profit
Define Conditional Resources
There but not profitable at present
Define Hypothetical Resources
Undiscovered or discovered but not assessed
What are five factors which can change whether a resource becomes profitable/unprofitable?
Increase in demand or price increases globally, Decrease in mining cost due to technological advances, Positive political will for the extraction of the resource, Environmental restrictions, Alternate energy resource of product
Define Magmatic Segregation
Separation of ore minerals by fractional crystallisation and related processes during magmatic differentiation
What deposits are formed by magmatic segregation?
Chromite and platinum
Define Volcanic Exhalative
The emission of hydrothermal solutions at the surface, usually under marine conditions and generally producing stratiform orebodies
What deposits are formed by massive sulphide deposits (VMS)?
Copper and zinc
Define Magmatic Crystallisation
Precipitation of ore minerals as major or minor constituents of igneous rocks in the form of disseminated grains or segregations
What is formed by magmatic segregation?
Pegmatites
Define Hydrothermal Veins
Deposition from hot aqueous solutions
What are the two sources of the fluids for hydrothermal veins?
Magmatic waters and Meteoric ground water
What deposits are formed by hydrothermal veins?
Tin, Tungsten, Copper, Lead, Iron
Define Secondary Enrichment
Leaching of valuable elements from the upper parts of mineral deposits and their precipitation at depth to produce higher concentrations
What deposits are formed by secondary enrichment?
Porphyry deposits e.g. copper
Define Mechanical Accumulation
Concentration of heavy, durable minerals into placer deposits (surface deposits formed by weathering, erosion, transportation and deposition)
What are five main requirements for placer deposits?
Pre-existing mineral veins at the surface, Dense and resistant ore minerals, Erosion and transportation, Suitable sites of deposition, Chemically unreactive ore minerals
What deposits are formed by mechanical accumulation?
Placer deposits e.g. gold
Define Residual Processes
Leaching from rocks of soluble elements leaving concentrations of insoluble elements in the remaining material
What deposits is formed by residual processes?
Residual deposits e.g. bauxite
Define Bauxite
A mixture of hydrated aluminium oxides and hydroxides
What are three conditions needed to form bauxite?
A hot and humid tropical environment causing intense chemical weathering, Aluminium rich and iron poor rock e.g. granite or limestone, Groundwater between pH4 and pH10
Define Sedimentary Precipitates
Precipitation of particular elements in suitable environments, with or without the intervention of biological organisms
What deposits are formed by sedimentary precipitates?
Precipitated deposits e.g. iron or gypsum
What are seven geophysical and geochemical techniques to prospect for metallic ore deposits?
Magnetic methods, Gravity methods, Electrical methods, Electromagnetic methods, Geochemical surveys, Remote sensing, Drilling
How is china clay formed?
Hydrolysis of orthoclase feldspar in quartz to make clay minerals (kaolin)
Define Quarrying
At or near the surface used for sandstone, limestone, chalk and aggregates
Define Open Cast Mining
Initial removal of shallow surface layers (overburden) followed by extraction of the mineral such as coal and bauxite
Define Mining Underground
Removal of minerals from below the surface such as coal, rock salt, iron sulphides, gold
Define Dredging
Removal of material from sea, lakes or rivers to extract minerals such as sand and gravel, tin and gold
