The main topics of this chapter can be summarized as follows:
|Geological resources are critical to our way of life. The proportions of metals in mineral deposits are typically several thousand times higher than those in average rocks, and special processes are required to make that happen. Some deposits form through processes within a magma chamber, others during volcanism or adjacent to a magma body, and some are related to sedimentary processes.
|8.2 Mining and Ore Processing
|Mining typically involves the excavation of very large holes at surface, or labyrinth of shafts, levels and declines underground, or both. This results in the production of waste rock that is typically piled up at surface. In most cases ores are processed at the mine site, creating other solid and liquid wastes that need to be contained. All of these waste products have the potential to lead to acid drainage and metal contamination.
|8.3 Industrial Minerals
|Non-metallic materials are very important to infrastructure and agriculture. Some of the major industrial minerals include sand and gravel, limestone for cement and agriculture, salt for a range of applications, potash fertilizer and decorative stone.
|8.4 Fossil Fuels
|The main fossil fuels are coal, oil and gas. Coal forms on land in wet environments where organic matter can remain submerged and isolated from oxygen for millennia before it is buried by more sediments. The depth of that burial will influence the grade of coal produced. Oil and gas originate from organisms living in marine environments, and again fairly rapid burial is required to preserve the organic matter on the sea floor. At moderate burial depth (2 to 4 km) oil will be produced, and at greater depth gas will be produced. Both oil and gas migrate towards surface, and can be trapped beneath impermeable rock layers in structural features, such as anticlines or faults. Some non-conventional fossil fuel resources include oil sands, shale gas and coalbed methane.
|8.5 The Implications of Resource Extraction for the Climate and Earth Systems
|The production and use of fossil fuels has massive climate implications and significant other Earth-system implications. The production and refining of metals and other Earth resources also contributes to climate change and significantly affects Earth systems.
Answers for the review questions can be found in Appendix 1.
- List some of the Earth’s resources that are needed to make a lithium ion battery?
- Explain why nickel deposits are associated only with mafic magma, not intermediate or felsic magma?
- What is the composition of the black smoke in a black smoker, and how does that relate to a volcanogenic massive sulphide deposit?
- How might an epigenetic gold deposit be related to a porphyry deposit?
- Oxidation and reduction processes are important to both banded iron formation deposits and to unconformity-type uranium deposits. Explain the role in each case.
- What is the role of the sun in the processing of lithium-bearing brines from salt lakes?
- What mineral is typically responsible for acid rock drainage around mine sites, and why is this mineral so common in this setting?
- Explain why glaciofluvial gravel is more suitable as a source for aggregate than till.
- The raw material for making cement is lime (CaO) and this typically produced by heating limestone (mostly CaCO3) to about 1000˚ C. Why is this an environmental issue?
- Name some important industrial minerals that are formed in an evaporite setting.
- If organic matter accumulates at an average rate of 1 mm per year and if 10 m of organic matter is required to make 1 m of coal, how long must a swampy environment remain stable and wet in order to form a 1.5 m coal seam?
- What are the ideal characteristics of petroleum source rocks and petroleum reservoir rocks?
- How deep must the source rocks be buried to produce oil?
- Why is shale gas an unconventional reserve, and how is it recovered? What are some of the environmental issues associated with that process?
- Why is it important that we stop developing new fossil-fuel resources, and reduce our collective and personal uses of fossil fuels to zero over the next few decades?