6: The lithosphere

Question 1

Define igneous, sedimentary and metamorphic rock

Answer 1

Igneous: Formed through the cooling of magma
Sedimentary: Formed when sediment is compressed under lots of pressure to form rocks like sandstone.
Metamorphic: When rock is changed under significant heat and pressure

Question 2

What is an Ore?

Answer 2

A rock or sediment with a significant percentage of valuable metals/minerals.

Question 3

What are hydro-thermal Veins?

Answer 3

Veins of valuable minerals/metals have been deposited and crystallised out of solution.

Question 4

outline how are hydro thermal deposits made?

Answer 4

1) An intrusion of cooled magma brings sparsely concentrated ores and minerals towards the surface.
2) Rain percolates down towards the intrusion and dissolves the minerals and metals into solution
3) The heat causes the water to expand and force up into the cracks
4) Overtime the minerals and metals crystallise, creating large streaks of valuable mineral deposits

Question 5

What 4 sources are sedimentary deposits made from?

Answer 5

• weathering of rocks
• weathering and oxidation of former minerals/metal deposits
• some may have passed trough an internal biological stage

Question 6

What are Proterozoic marine sediments?

Answer 6

They are vitally important iron ore deposits, which become oxidised when life began to photosynthesise and release fast amounts of oxygen .
This can be seen in some rock cliffs that have been oxidised red half way through.

Question 7

What are alluvial deposits?

Answer 7

Deposits made out of sand, gravel and valuable materials that flow in streams.

Question 8

What are evaporites?

Answer 8

Crystals made by evaporation from an aqueous solution of minerals. Usually created when lakes dry up.

Question 9

What are biological sediments?

Answer 9

sediments made from eroded/ decayed organisms to create materials like chalk (sea shells).

Question 10

What is ore cut off grade?

Answer 10

The minimum grade required for the ore to be economically mined.

Question 11

What are (mining) reserves?

Answer 11

The amount of material that can be exploited using existing technology under current economic conditions.

Question 12

What are (mining) resources?

Answer 12

All the material that could potentially exploited technically and economically now or in the future.

Question 13

What is laskys law?

Answer 13

Shows that as the decrease the ore cut off grade, the amount of material included is increased.

Question 14

What are the names of the different survey techniques?

Answer 14

• gravimetry
• Magnetic methods
• Electrical resistivity
• satellite imagery

Question 15

What is gravimetry?

Answer 15

A technique which measures variations in the earths gravitational field.

These variations are caused by density contrasts in the surface rock and sediment.

Geographical surveys are performed with gravimeters and are always accompanies by high precision topographic surveys.

Question 16

What are magnetic geology survey methods?

Answer 16

Aircrafs/vehicals with recording instuments often travel over the intended area and detect changes to the earths magentic feild. Often used to dect metals such as iron.

Question 17

What is involved in the electrical resistivity survey technique?

Answer 17

Injection of current into the ground to detect the electrical resistance felt, which directly links to the density of the rocks.

Question 18

What is satellite imagery surveying?

Answer 18

When satellites send radiation such as visibile light, Infrared and uv rays to earth, to map the different minerals.

Question 19

What is a mines overburden?

Answer 19

The rock/material above the ore.

Question 20

What factors effect mine viability?

Answer 20

• overburden
• hydrology
• ore purity
• depth
• transport/accessibility
• economical viability

Question 21

What is systematic trial drilling?

Answer 21

A representative sample of rock needs to be taken so that the mining company knows which areas can be commercially exploited, and which areas have highest ore purity.

Question 22

Name 5 environmental impacts of mineral exploitation.

Answer 22

• carbon dioxide emission
• landscape scarring and degradation
• destruction of habitats
• chemical leachate (leaking)
• deforestation

Question 23

When are the two different types of used?

Answer 23

Open-cast mining

• Used when there are relatively large deposits that are quite close to the surface.
• usually cheaper, but creates a lot of waste

Deep shaft mining

• mine deep deposits
• more precise, so can afford to mine smaller deposits

Question 24

What is tailing?

Answer 24

It the waste powder created when ore is processed. In most cases this is toxic and is stored in a tailings pond.

Question 25

What are two potential impacts of sand mining?

Answer 25

• Sand stores water underground in arid regions, meaning if the sand its taken away, then the impermeable bedrock is left and water runs off.
• can cause erosion of beaches and river banks
• if water runs off quickly, lakes can begin to dry up, impacting the local fishing industries.

Question 26

Link one named resource to its geophysical technique

Answer 26

• Magnetism of iron ore/magnetite Magnetometry
• High density of igneous deposits/galena/cassiterite Gravimetry
• High electrical resistance of igneous deposits Resistivity