Last minute geology

Last minute geology

1. Rock examples

   • Igneous
     • Intrusive- granite, quartz
     • Extrusive- Pumice, basalt
   • Sedimentary
     • conglomerate
     • sandstone
     • mudstone
   • Metamorphic
     • limestone=marble
     • siltstone=slate

2. Exploration methods

   • The search for the rocks containing the minerals, oil or coal
   • Aerial methods
     • Magnetic surveys
       • Iron, nickel, cobalt change magnetic field
       • Magnetometers- detect change
       • 'magnetic anomaly'
     • Gravity surveys
       • Gravimeters- detect changes in gravitational pull
       • Dense r&m affect pull
     • Electromagnetic surveys
       • detects good electric conductors
       • Magnetic field sent from transmitter(plane)
         • MF makes tiny eddy currents in minerals
           • Eddies make own magnetic field(secondary field)
             • Receiver detects SF
       • copper sulfide, lead sulfide, zinc sulfide, gold, silver
   • On-site methods
     • Seismic survey
       • Shock wave into ground
       • record reflecting sound waves
       • geophones, detect sound waves
       • structure of Earth's crust 35-60km deep
         • help understand how minerals form
       • help predict where minerals are
     • Geochemical surveys
       • Geochemistry
       • samples from surface/drill holes in rock- see amount of mineral
       • core sample- rock removed
       • water above/below indicator of minerals
         • groundwater dissolves minerals
           • detects diamonds, gold, uranium, copper
   • Satellite images
     • make images using light rays we can't see
     • sensors detect radiation- near-infrared, shortwave-infrared, thermal-infrared
     • help see features images with normal light don't show
   • Geological maps
     • show ore bodies from above&side
     • side view- 'cross-section'
     • help us decide how to best mine the ore

3. Mining

   • type of mineral geology of the area cost & mineral value
   • Surface Mining
     • cheapest if near surface
     • open-cut mine/ large pit
     • ore removed by machines with large shovels, giant drills called augers and drag lines
   • Underground mining
     • ore is deep, fairly concentrated, small space/narrow veins
     • Vertical shafts
       • horizontal shaft into ore
         • hoist lifts it to surface
     • Steady slope/decline
       • ore driven out by vehicle
       • 15 degrees
     • inside mountain- adit- horizontal tunnels
   • Dredging
     • minerals heavier than sand
     • dig pit- fill with water= lake
       • boat sucks up sand using hoses
         • separated then sand & water piped back in
   • Leach mining
     • minerals dissolved in fluid injected
     • holes drilled into rock
       • 'leach solution' is pumped into the ore
         • dissolved ore solution pumped to the surface
     • solution which will dissolve the ore= 'leach solution'
   • Petroleum wells
     • Petroleum- liquide & gas- trapped within sedimentary rock layers
     • bore narrow holes into rock
     • Derrick- steel tower to support drilling equipment
     • hole drilled until oil/gas found or give up
     • clay, chemicals, water pumped through drill pipe- keep cool
     • When found
       • drill & pipe removed
       • metal casing (hollow tube lowered into hole and cemented in place
       • System of pipes and valves -'wellhead'- separates into storage tanks
       • pumps, water/steam/gas injected to increase pressure/oil flow
     • Rigs
       • rest on seafloor, float wires attached, boats
       • pumped through pipelines on seafloor to factories
       • floating ships link to well, onboard treatment/storage
       • flammable- disaster risk high