Geological Processes That Created Exploitable Mineral Deposits

Question 1

Igneous processes

Answer 1

Process by which rocks and minerals are created by cooling and hardening of magma or Molton lava known as igneous

Hydrothermal deposition

Question 2

Igneous processes

Hydrothermal deposition

Answer 2

Igneous intrusion = rocks formed from magma that cools, solidifies w/in earth crust.
Intrusions produce pressurised superheated h2o that dissolved surrounding rocks — mineral rich solutions travel along fissures away from igneous batholith cooling as they do.
As they cool dissolved minerals crystallise and come out of solution in order of solubility - leader soluble 1st.
FRACTIONAL CRYSTALLISATION
Once minerals separated and deposited soon after batholith formed later exploitation became possible.
Metal ores deposited by hydrothermal process inc tin, copper, lead, silver, gold and arsenic

Question 3

Metamorphic processes

Answer 3

Igneous processes + tech movement of crustal plates alter existing rocks w
high pressure and temp,
w out melting them —> metamosphic rocks.
Eg limestone —> marble (high pressure + temp)
Eg mudstone —> slate (extreme pressure)

Question 4

Sedimentary processes

Answer 4

Cause minerals to settle + build up produce layers deposited sediment.
This deposition and subsequent cementation at earths surface + w in bodies water creates sedimentary rocks and minerals

Question 5

Sedimentary process

Protozoic marine sediments

Answer 5

Inc. iron ore deposits ie hematite + magnetite.
They formed when dissolved iron compounds oxidised by O released by photosynthesis—> insoluble iron oxide deposits between 2.5 and 1.8 bn yrs ago

Question 6

Sedimentary processes

Alluvial deposits

Answer 6

Materials carried and separated by flowing h2o- velocity h2o and density of the solids.
Gold, diamonds, tin, ore, gravel, sand, clay

Question 7

Sedimentary processes

Evaporites

Answer 7

Bay of ancient sea isolated, h2o evaporates leave crystallised minerals ie halites

Also
Evaporites form inland seas in desert areas as h2o from inflowing river evaporated

Question 8

Sedimentary processes

Secondary enrichment

Answer 8

Many economically important minerals that are soluble/ insoluble depend on conditions, esp availability O.
May be transported in solution, by moving h2o, + then deposited as their oxidation state changes.

Question 9

Sedimentary processes

Biological sediments

Answer 9

Where living organisms form mineral deposits.
These processes often concentrate minerals that can b deposited in sedimentary rock.

Eg limestone and chalk = shells marine
Terrestrial veg = coal
Marine organisms = crude oil and natural gas