Metallic Mineral Deposits

Question 1

What is the Concentration factor

Answer 1

The amount by which the metal is concentrated to make an ore deposit

Concentration factor = Concentration if metal in ore/Average crustal abundance

Question 2

What are the three types of ore deposits

Answer 2

Ores formed by hydrothermal processes
Ores formed by igneous processes within the Earth
Ores formed by sedimentary processes at the earths surface

Question 3

What are hydrothermal ore deposits

Answer 3

Three key requirements to from hydrothermal fluid is source of heat - source of water - Source of metals

Question 4

Placer ore deposits

Answer 4

Require - Pre-existing mineral veins exposed at the earths surface
Dense, physically and chemically resistant ore minerals
Erosion and transport processes that sort and separate the ore minerals from the gangue minerals
Suitable sites of deposition where the ore minerals will be concentrated

Question 5

Sites of placer deposits

Answer 5

Meander bends - Deposits found on the inside
Plunge pools - Dense placer minerals become trapped in the plunge pool
Upstream of projections - Projections from the river bed will trap dense placer minerals on the upstream side
Downstream of confluences - Where a fast flowing tributary joins a slower flowing river in the current velocity drops, placer minerals are deposited there
On beaches - Denser placer minerals left behind by a weaker backwash

Question 6

Advantages and disadvantages of placer mining

Answer 6

Recent deposits are loose unconsolidated sands that are easily accessible and cheap to mine, ores are already separated from gangue minerals so less waste

Scars on the landscape, noise and dust, water pollution

Question 7

Secondary enrichment

Answer 7

Occurs when metals are leached from surface rocks and precipitated just below the water table

Question 8

Secondary enrichment above the water table

Answer 8

Rain falls and infiltrates the exposed coper deposit, in the zone of oxidation above the water, chemical reactions change insoluble copper sulphides into soluble copper sulfates, these are carried down and a leached zone is left covered by an insoluble iron oxide capping called a gossan

Question 9

Secondary enrichment above the below the water table

Answer 9

The conditions are now reducing, chemical reactions change soluble coper sulphides into insoluble

Question 10

Environmental problems of metallic mineral processing

Answer 10

Disposing of tailings - these are toxic
In situ or heap leaching - leaching solutions are often acidic
Smelting - Major source of atmosphere pollution