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Energy and resources > L9 - Evaporites > Flashcards

L9 - Evaporites Flashcards

1
Q

What are evaporites?

A

Chemically-precipitated rocks that form at or near the Earth’s surface from saturated brines via solar evaporation or diagenetic processes

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2
Q

What is brine?

A

Water with dissolved salts.

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3
Q

What are the primary sources of ions for evaporite formation?

A
  • Marine influx and circulation
  • Hydrothermal springs and mid-ocean ridge (MOR) circulation
  • Groundwater and deep-seated springs
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4
Q

What are the economic uses of evaporites?

A
  • Lithium: Used in ceramics, glass, aluminum production, batteries, and pharmaceuticals.
  • Potash: Used as fertilizer and in the chemical industry.
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5
Q

What makes lithium significant for batteries?

A

It is the lightest metal, highly reactive, flammable, and used in battery technology.

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6
Q

Where are the largest reserves of lithium and potassium found?

A
  • Lithium: 51% in Chile, 22% in Australia, 13% in Argentina.
  • Potassium: 28% in Canada, 21% in Belarus, 18% in Russia.
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7
Q

Why is potassium irreplaceable as a fertilizer?

A

There are no substitutes for potassium in fertilizer.

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8
Q

What factors influence evaporite precipitation?

A

Climate, brine concentration, hydrology (restriction), brine composition, and biota.

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9
Q

Why are arid climates necessary for evaporite formation?

A

High temperatures and low humidity drive evaporation, leading to brine saturation and mineral precipitation.

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10
Q

How does brine concentration affect evaporite formation?

A

As water evaporates, brine becomes concentrated, leading to precipitation of minerals such as CaSO4 and CaCO3.

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11
Q

What is the role of hydrology in evaporite formation?

A

Restricted water bodies with limited inflow and outflow lead to increased salinity, promoting evaporite precipitation

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12
Q

Where do evaporites typically form?

A
  • Continental playas and sabkhas: Pore water evaporation and shallow brine pools.
  • Saline lakes and salinas: Evaporation of standing water bodies.
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13
Q

What is the Zechstein (Permian) case study?

A

It describes carbonate-evaporite cycles in the paleo North Sea, with thick halite deposits surrounded by carbonates and sulfates due to restricted conditions

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14
Q

What techniques are used in evaporite exploration?

A
  • Regional depositional and climatic history studies
  • Seismic surveys
  • Wireline logging (e.g., gamma-ray, density)
  • Borehole geochemistry
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15
Q

What are the advantages and disadvantages of industrial salars?

A
  • Advantages: Simple process.
  • Disadvantages: High operational costs, large environmental footprint, and extensive water usage.
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16
Q

What are the advantages of subsurface mining of evaporites?

A

Low operational costs and small environmental footprint.

17
Q

What are some uses of evaporites for subsurface storage?

A

Industrial and nuclear waste, munitions, CO2 (CCS), and liquid hydrocarbons for emergency reserves.

18
Q

What are the two main types of lithium deposits?

A
  • Brine deposits: Found in salt flats, involve mining natural/artificial brine pools.
  • Hard rock deposits: Lithium-bearing minerals in igneous rocks like pegmatites.
19
Q

What is the environmental impact of lithium brine mining?

A

Immense water consumption in arid areas and potential leakage of brine into groundwater

20
Q

What is Direct Lithium Extraction (DLE)?

A

A technique to extract lithium chloride, which is purified to produce lithium hydroxide.

21
Q

What minerals are associated with hard rock lithium deposits?

A

Spodumene: LiAlSi2O6
Lithium micas: KLi2Al(Si4O10)(F,OH)2

22
Q

What are the environmental concerns with evaporite mining?

A

High water usage, potential chemical leakage, strip mining, and sinkhole formation.

23
Q

How do evaporites form?

A

Through brine oversaturation caused by solar evaporation or diagenetic processes.

24
Q

What conditions are necessary for evaporite formation?

A

Arid climate, negative water balance, and restricted brine inflow and outflow

25
Q

How does evaporite mineralogy affect its applications?

A

Mineralogical variability determines its economic uses, such as lithium for batteries and potassium for fertilizers.

Energy and resources (11 decks)

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