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Natural Resources and the Environment > Mining and Ore deposits > Flashcards

Mining and Ore deposits Flashcards

1
Q

What is a Natural Resource? Give a definition and examples.

A

Naturally forming substances that are considered valuable in their relatively unmodified, natural form e.g. Metals, industrial rocks and minerals, energy minerals, gemstones, wood, wind, water and fish.

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2
Q

What are the requirements for a resource to enter cumulative production?

A

With increasing certainty, a resource becomes identified and has demonstrated and measured reserves. With increasing concentration it becomes more economic. If all factors are present.

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3
Q

What is the natural resource concept?

A

The relation of price, value, demand, supply and substitution. These are determined by how easy it is to extract a resource.

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4
Q

What might you do if the price of a resource is too high?

A

Substitute it for a different material, the original material will then go down in demand and then price.

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5
Q

Demand is determined by:

A

A resources usefulness

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6
Q

Supply is determined by:

A

Ease of extraction and distribution. Supply is responsive to demand

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7
Q

Lack of supply can lead to:

A

Substitution

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8
Q

What is an industrial mineral:

A

Any earth material of economic importance, excluding metal ores and fuels. It has value due to its nature/properties/strengths used in its mineral form without extracting any metal. E.g. Building stone, china clay, Barite, Fluorite and ‘industrial’ diamonds.

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9
Q

Give examples of Building stone substitution and why it might occur.

A

If there is no better option from local resources then some must be imported. E.g. Millstone Grit, N.Wales Slate, Larvikite (Syenite from Larvik Norway)

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10
Q

Give examples of local building stone used:

A

Aberdeen: Granite
Sailsbury Cathedral: Chilmark stone (limestone)
Raglan Castle: Sandstone

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11
Q

Name 3 industrial minerals that can be found in this country that aren’t building materials

A
  • Potash
  • Rock Salt
  • China Clay
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12
Q

What is Kaolinite and how is it mined?

A

Feldspar rich clay, (china clay) and its sprayed with high pressure water, held in suspension.

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13
Q

Whats the definition of an Orebody:

A

An accumulation of minerals distinct from its host rock that is rich enough in metal to be worth economic exploitation, i.e. Profitable.

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14
Q

What are gemstones?

A

Artificially polished, faceted and shaped for decorative purposes.

  • They are controlled by marketing, rarity, imperfections
  • Precious stones: Diamonds, Rubies, Emeralds
  • Semi-precious: Topaz, Garnet, Zircon
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15
Q

What is an Energy mineral?

A

In its natural state or after refinement it can be used to generate energy

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16
Q

Define sustainable development:

A

A pattern of resource use that aims to meet human needs while preserving the environment so the the needs can be met in the indefinite future.

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17
Q

Define Mining Legislation:

A

Robust conditions in which the mining company must show environmental awareness ad proactivity.

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18
Q

How much gold has ever been mined?

A

161,000 tons

- barely enough to fill 2 Olympic sized swimming pools

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19
Q

Disadvantages of current large open pit gold mines:

A
  • Large visual impact
  • 1-2g of gold per ton of rock (very wasteful)
  • geography restricted
  • 250t = 1 wedding ring
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20
Q

Disadvantages of artisanal gold mines:

A
  • minor due to local nature of mining but environmental rehab isn’t assessed.
  • more destructive
  • pollution from mercury and cyanide extraction.
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21
Q

Define a metalliferous ore:

A

A rock that can be worked economically for a metal or group of metals that it contains.

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22
Q

What are Native Ores:

A

Ore that contains a metal in its elemental free state.

- Gold, silver, mercury, copper, platinum

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23
Q

What is a troy Oz equivalent to in grams?

A

31g

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24
Q

What are Sulphide Ores:

A

Contain a metal or group of metals in combination of Sulphur

  • Common
  • Iron (pyrite), Lead (Galena), Zinc, Copper, Nickel
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25
Q

What are Oxide Ores:

A

Contain a metal or group of metals in combination of oxygen.

  • Non ferrous to ferrous metals commonly found here and economically important for these metals
  • Iron, Tin, Chromium, Titanium
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26
Q

What are Carbonate + Sulphate Ores:

A

Contains metal/group in combination with oxygen and carbon OR oxygen and sulphur.
- Barium sulphate, Iron carbonate, Copper Carbonate (Malachite)

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27
Q

Advantage and disadvantage of carbonate + sulphate ores:

A
  • Good signal for presence of primary ores.

- Usually form due to weathering/interaction with primary ores (not helpful for extraction of metals)

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28
Q

Name the crustal abundance from Oxygen to Gold

A 
Oxygen : 47
Silicon: 27
Aluminium: 8
Iron: 5
Chromium: 0.01
Copper: 0.005
Gold: 4 parts per billion
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29
Q

What concentration factor is needed to get a normal crustal abundance of Au up to to Ore levels?

A

A concentration factor of 5 for Iron but 250 for gold

- the cut off for a gold deposit is >1ppm

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30
Q

How do hydrothermal ore deposits form?

A

Scavenge, Transport, Concentration and Deposition.
- Hydrothermal water flowing through area of ore deposit will pick up the gold etc and transport it within an economically efficient enough level even if normal extraction (mining) is 1%.

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31
Q

Where do the hot fluids in hydrothermal processes come from?

A
  • Magmas (intrusion)
  • Metamorphism
  • Sea Water
  • Anywhere the geothermal gradient is high enough to heat the water.
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32
Q

What causes precipitation of minerals from hydrothermal fluid?

A
  • Change in temp (cooling)
  • Change in pressure (entering veins and closer to the surface)
  • Compositional change (chemistry)
  • Fluid mixing (brine and magma)
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33
Q

Whats the definition of hydrothermal:

A

to do with hot fluids - usually related to magmatic activity

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34
Q

What happens upon cooling of hydrothermal fluid?

A

They precipitate out ore and gangue minerals

- they typically form veins, dissemminations and stockworks.

35
Q

Describe a Porphry deposit:

A

A large high tonnage, low grade (<1%Cu) deposits associated with plutons of intermediate-acidic porphyritic igneous rock.

36
Q

What are porphyries a major source of?

A

Copper, gold and molybdenum

37
Q

Where does a porphyry typically form

A

In plutons above subduction zones

38
Q

How does a porphyry form?

A

Sudden release of fluids near the surface, with a shattering of the enclosed rocks, forming ‘stockwork’ mineralisation.

39
Q

What is the source of metals and heat to form a porphyry?

A

Magma, most likely if not always an intrusion

40
Q

Explain how mineral veins form:

A

sudden release of volotiles causes rocks to crack and change in pressure so minerals/metals precipitate out to fill the gap.

41
Q

What mineral structures do porphyrys typically produce

A

veins, disseminations and stockworks with chalcopyrites

42
Q

A porphyry is an example of what?

A

A hydrothermal ore deposit

43
Q

What is an Epithermal deposit?

A

A low tonnage but high grade deposit that telescopes up from depth, usually form within 1km of the surface.

44
Q

What temperature do epithermal deposits reach the surface at?

A

100-200 degrees C as hot springs

45
Q

Name typical minerals found in epithermal deposits

A

Gold, Silver, Mercury and Antimony

46
Q

How do Epithermal deposits form?

A

Heat source at depth causes fluid mixing as well as groundwater as source water.

  • metals sourced from magma
  • found in hot spring veins
  • boiling as well as change in pressure, temp, etc can cause precipitation (mixture of processes that cause precipitation)
47
Q

Whats different about the cornish vein deposits?

A

From a granite pluton, the change in temperature radiating outwards causes zoning of different minerals.

48
Q

Metamorphism produces fluids which may carry gold what geological structure aids the golds deposition and what name is given to this deposit

A

Major transcrustal faults (e.g. San Andreas) acts like an outlet for this fluid depositing gold on cooling and decompression forming an Orogenic gold deposit.

49
Q

Advantage of Orogenic gold deposit

A

Largest source of gold

  • quartz
  • pyrite
50
Q

Whats another name for hydrothermal deposits that form at mid ocean ridges?

A

VMS - Volcanogenic Massive Sulphides

51
Q

How do VMS form?

A

During submarine volcanic activity at the sites of black smokers. Crust is at its thinnest and sea water percolation into the crust is heated to about 275-350

52
Q

What are black smokers made from?

A

Mainly sulphides as well as Anhydrite mixed in. Cones become more porous upward.

53
Q

Name the main elements found at black smokers

A

Copper and Zinc. Sometimes Lead, Silver and Gold

54
Q

What is a Placer Deposit?

A

Mineral deposits that have been concentrated by mechanical action, typically fluvial processes

55
Q

Name common placer deposit minerals:

A

Gold, magnetite, ilmenite, chromite and diamonds

56
Q

What was found in Witwatersrand basin in S.Africa?

A

Lithified palaeo placer deposits of conglomerate.

  • 1886 George Harrison found the largest gold deposit on the planet
  • Gold Rush
  • it now contributes to 1/4 of Africa’s GDP
57
Q

What is a Laterite deposit

A

When chemical weathering removes soluble elements from a rock, leaving insoluble residual deposits which may be enriched metals.
- Typically tropical

58
Q

Give an example of a metal typically found in a laterite deposit?

A

Nickel

59
Q

Where is Nickel sourced from?

A

Ultra basic rocks form nickel laterites

60
Q

Describe the sequence of beds that form a laterite deposit:

A
  • Fresh peridotite
  • Altered and partially altered peridotite with garnierite concentration (Transition)
  • Residual laterites
    - Porous laterites (Yellow Limonite)
    - Nodular iron oxides (Red Limonite)
    - Iron oxide cap (Red Limonite)
61
Q

What is Bauxite?

A

A mixyure of 3 hydrates. Its a rock type not an ore mineral from broken down clays forming alumina-gibbsites

62
Q

Name the key identification properties of native copper

A
  • Element
  • Streak = Dark Brown
  • Very Dense = 8.96
  • Pipes and wires
63
Q

Name the key identification properties of Sphalerite

A
  • ZnS
  • Greasy Lustre
  • Rhombic crystal form
  • Jewellery
64
Q

Name the key identification properties of Galena

A
  • PbS
  • Dense = 7.4
  • Making lead acid batteries
65
Q

Name the key identification properties of Chalcopyrite

A
  • CuFeS2
  • Brass/Yellow
  • Amorphous crystal form
  • Magnetic when heated
  • Finding copper
66
Q

Name the key identification properties of Pyrite

A
  • FeS2
  • Gold/Brass
  • Hardness = 6
  • Cubic
  • Used to make sparks with flint
67
Q

Name the key identification properties of Magnetite

A
  • FeO
  • Octohedral crystal form
  • Magnetic
  • Gravity separation
68
Q

Name the key identification properties of Haematite

A
  • Fe2O3
  • Hardness = 6
  • Cherry red streak
  • Reniform crystal form
  • Ballast in ships
69
Q

Name the key identification properties of Malachite

A
  • Cu2CO3(OH)2
  • Teal green
  • Silky lustre
  • massive, botryiodal, stalactitic crystal form
  • Pigment in Jewellery
70
Q

Name the key identification properties of Siderite

A
  • FeCO3
  • White streak
  • Tabular crystal form
  • Steel production
71
Q

Name the key identification properties of Barite

A
  • BaSO4
  • White
  • Pearly lustre
  • Fibrous, Nodular, Massive crystal form
  • Weighting filler in rubber
72
Q

What are magmatic ore deposits?

A

Forming at high temperature that occur during the cooling of magma.

73
Q

Which elements are found in magmatic sulphides?

A

Platinum, palladium, rhodium are most economical but you can find all PGE
- Cu and Ni

74
Q

What are PGE (Platinum Group Elements) used for?

A
  • autocatalysts (e-tech)
  • in jewellery
  • anti cancer drugs
75
Q

Where can you find magmatic sulphides?

A
  • Great dyke (Zimbabwe)
  • Bushveld Complex (S.Africa)
  • Sudbury (Canada) - Ni dominant but PGE are a bi-product.
76
Q

Where does 75% of PGE come from?

A

S.Africa

77
Q

How do magmatic sulphide deposits form?

A
  • Mafic magma (gabbro)
  • Magma reaches S saturation piont and can’t hold anymore sulphur in solution
  • Sulphide liquid in magma is like oil in water forming droplets
  • Saturation is caused by prolonged crystallisation and contamination from crustal S.
  • PGE + Au, Ni, Cu are attracted to sulphide liquid => concentration.
  • S liquid is denser than the magma now so sinks to the bottom to form a cumulative layer (4ppm)
78
Q

What mineral ores is found in the magmatic sulphide deposits?

A
  • pyrrhotite
  • pentlandite
  • chalcopyrite
79
Q

Name some early forming magmatic oxide minerals

A
  • Chromite
  • ilmenite
  • magnetite
80
Q

How do magmatic oxide deposits form?

A

In ultramafic/mafic magma (gabbros and dunites). Magma starts to crystalize high temperature minerals (chromite, ilmenite, magnetite) which sink to form a layer/ ore deposit at the base of the reservoir.

81
Q

Whats is the composition of a magmatic oxide deposit?

A
  • Chromite, Ilmenite and Magnetite. (45% Cr2O3)

- Fe and Ti can also form (18% TiO2)

82
Q

What is a Pegmatite?

A

An igneous rock with very coarse grain/crystal size, crystals >1cm.

83
Q

How do pegmatites form?

A
  • Felsic/acidic magma in the presence of volotiles (CO2, H2O) aids the growth of crystals such as Feldspar, quartz and mica.
  • Incompatible elements concentrate in the magma that remains.
  • The remaining magma crystallises and forms exotic minerals/rare earth minerals in the final stages.
  • E.g. Li, Ur, Th, Zircon, Emeralds.

Natural Resources and the Environment (3 decks)

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