Economic Geology Flashcards
Porosity
Vol. of pore space/ vol. of rock * 100
Permeability
Ability to transmit fluids (distance/time)
Factors affecting porosity
Degree if sorting Diagenesis Grain shape Faults Packing
Factors affecting permeability
Porosity
Temp
Hydrostatic pressure
Effect of mass of overlying water column, increasing with depth (length of column is hydrostatic head)
Hydraulic gradient
Difference in hydrostatic pressure between 2 points / distance between
Water table
Surface separating saturated and unsaturated rocks
Aquifer
Body of porous and permeable rock capable of storing and yielding water
Aquiclude
Impermeable rocks excluding water
Recharge zone
Area of aquifer open to the atmosphere allowing replenishment of water
Aquiterol
Slows water down
Confined aquifer
Aquifer between 2 layers of impermeable rock
Live aquifer
Currently being replenished
Fossil aquifer
No longer replenished
Artesian basin
Large synclinical confined aquifer under hydrostatic pressure
Artesian well/borehole
Holds water under hydrostatic pressure which rises up to the well as a piziometeric surface on release
Piziometeric surface
Level to which water rises (above ground level)
Concentration factor
Number of times they have been concentrated by
Concentration of metal in ore/ ACA
Grade
Concentration of valuable mineral in ore
Cut off grade
Economically viable concentration
ACA*CF
Gangue minerals
Low value waster mineral
Properties of placer minerals
Dense
Hard
Chemically resistant
Where are placer desposits
Meander bends Plunge pool Upstream projection Downstream confluence Beaches
Pros of placer mining
Cheap
No gangue
Less environmental impact
