Unit 5: Mineral and Oil Resources. Economic Minerals. a mineral deposit is a volume of rock enriched with one or more minerals

Transcription

1 Unit 5: Mineral and Oil Resources Economic Minerals a mineral deposit is a volume of rock enriched with one or more minerals minerals in this sense refers to more to a useful material then to the technical definition some minerals can be used just as they are found in the ground, with little or no processing gemstones sand gravel halite (salt) most minerals must be processed before they are used these minerals often exist in mineral compounds and must be extracted iron aluminum mineral deposits may or may not be economically viable Schefferville Iron Ore Mine (booming) Bell Island Iron Ore Mine (non operational) this is determined by extraction costs manpower costs energy costs mineral concentration depth below surface demand / interest market value in general, the higher the concentration of the mineral, the more economical it is the term "ore" refers to a mineral deposit from which one or more valuable substances can be extracted economically 1

2 1) Metallic Mineral Resources Mineral Resources metals recovered by smelting or other chemical processes Mineral Element Use Bauxite Aluminum (Al) pop cans, aircraft parts Calcopyrite Copper (Cu) water pipes, wires Hematite / Magnetite Iron (Fe) steel, nails Galena Lead (Pb) weights Pentlandite Nickel (Ni) money 2) Non Metallic Mineral Resources minerals used for their own properties Mineral Halite Calcite Gypsum Quartz Graphite Diamond Use salt cement gyproc / plaster glass pencil lead / lubricants jewelry / cutting tools Mineral Occurrence in NL Mining Prospects Newfoundland Mining Prospects Labrador 2

3 3

4 4

5 Types of Mineral Deposits 1) Magmatic (from magma) two types layered minerals settle as they begin to cool based on their density for example, chromite will often crystallize and settle in layers at the bottom of magma chambers disseminated (pegmatites) as minerals cool they may group into crystals that grow larger during re melting and re cooling periods these semi solid crystals can be forced into cracks in formed rocks before completely hardening rare minerals such as amblygonite are often concentrated this way 2) Vein Deposits (hydrothermal) hydrothermal fluids (basically hot water) rise to the surface through any available openings (faults, cracks, fissures,etc) these fluids carry with them many dissolved minerals as the fluid cools, the minerals come out of solution which fills the gaps quartz veins are common in Newfoundland 5

6 3) Placer Deposits minerals are carried through water and settle based on the current of the water 4) Secondary Enrichment minerals already formed and located at or near the surface leaching occurs removing minerals or "useless" material from top layers the end result may result in a higher concentration either at or below the surface 5) Metamorphism contact metamorphism occurs around magma deposits as the surrounding rocks are metamorphosed they can be injected with minerals from the magma this injected rock is known as skarm 6

7 Open Pit Mines and Underground Mines Open Pit extraction from open pit mines occurs on the Earth s surface the potential exists for considerable destruction to both surface soil and vegetation, and the release of significant amounts of mine dust open pit mines are usually accessed by surface terracing, thereby allowing technological equipment to follow the shape of the deposit open pit mines are safer and less costly Underground extraction beneath the Earth s surface takes place in underground mines underground mines result in less damage to surface soil and vegetation mine dust levels in the atmosphere are less underground mines are usually accessed through shafts and/or elevators and are more costly and less safe underground mines are usually chosen if the deposit is located at a significant depth beneath Earth s surface but also depends on the shape of the deposit exploration techniques include: seismic records remote sensing prospecting observing drill cores cross sections geological mapping magnetic survey gravity survey geochemistry We will be going into more detail with some of these 7

8 1) Which type of mine would suit the following deposits? a) Kimerlite pipes are carrot shaped ultramafic igneous intrusions that is associated with diamond deposits. b) A coal seam is a vein like deposit located deep in the ground. 2) The San Jose Copper Gold mine was developed as an underground mine. a) Why might this mine have been developed in this way? b) What are one positive and one negative point to argue the development of this mine as an open pit mine? 8

9 9

10 Processing Ore techniques for processing ore deposits include: floatation gravity separation heap leaching pyromet hydromet Floatation involves mixing grounded ore with water, oil, and chemicals grounded ore becomes suspended in the water and is subjected to bubbles of air due to the presence of chemicals this causes the minerals and/or elements of value to float to the top where they can be scraped off Gravity separation involves feeding grounded ore into a pulsating body of water this serves to settle out the heavy material while floating away the light material if the heavy material is what one wishes to retain, then it is taken from the bottom if the light material is what one wishes to retain, then it is taken from the top Heap leaching grounded ore placed as a layer onto impermeable material "heap of material is irrigated with a liquid, which percolates down through this dissolves away the valuable minerals and/or elements to be collected below Pyromet heat is used to separate the minerals and/or elements of value from the ore the materials the separated by density and the desired minerals and/or elements can be removed Hydromet a chemical method that involves oxidation and acid leaching to separate out the desired minerals and/or elements. 10

11 petroleum naturally occurring flammable liquid found in geologic formations below Earth s surface consists of a mixture of hydrocarbons can also be referred to as crude oil; however, both crude oil and natural gas are generally accepted under the term petroleum crude oil a mixture of hydrocarbons that exist in a liquid state in underground reservoirs and remain in a liquid state once subjected to atmospheric conditions hydrocarbons chemical compounds that involve hydrogen and carbon atoms examples include: butane propane ethane methane Petroleum Formation if predominantly methane exists, then it is referred to as dry gas a mixture of gases is referred to as wet gas 11

12 microscopic marine animals (zooplankton) and plants (phytoplankton) are the main sources of organic matter in the production of petroleum preservation potential means the conditions that favour the preservation of organic matter the two most important conditions are: 1. anaerobic conditions (low oxygen content) 2. rapid sedimentation by fine grained material anaerobic conditions can exist in swamp and lagoon environments examples of fine grained material include mud size, silt size, and sand size particles there are other conditions that must be met: 1) Organic matter must be produced in great abundance 2) Oil and gas must be compacted and forced into porous and permeable rock (sandstone or limestone) called reservoir rock the abundance of organic matter is determined by the amount of light water depth latitude water temperature water turbidity nutrients preferred by plants phosphates nitrates 12

13 1) Diagenesis: Stages of formation shallow burial of organic matter near normal temperature and pressure some amount of decay methane, carbon dioxide, and water are released kerogen, a complex hydrocarbon, is left behind 2) Catagenesis: deeper burial increased temperature and pressure petroleum is released from the kerogen oil released first gas released second 3) Metagenesis: even higher temperature and pressure (close to metamorphism conditions) methane released at this point the petroleum has matured enough to migrate to traps 13

14 Formation of Petroleum Traps Source rock: must contain an abundance of organic matter petroleum is often created and released from the source rock while lithification is occurring examples of source rocks are shale and limestone Reservoir rock: it is the rock which petroleum moves through and is stored in requires high porosity and high permeability porosity volume of pore spaces or holes between sediment grains influenced by particle shape, size, and sorting large, rounded, well sorted particles offer higher porosity, particularly if the amount of cement between them is limited permeability interconnectiveness of the pores allows the movement of the petroleum usually, the higher the porosity and the larger the pore spaces, the higher the permeability examples of reservoir rocks are sandstone, dolomite, and conglomerate petroleum exists within reservoir rock between sediment as opposed to being confined as a whole volume of liquid petroleum there are no ponds of petroleum in the ground Cap rock: impermeable rock serves to trap petroleum from either escaping to surface spreading throughout the rock 14

15 Types of Traps Anticline Trap: permeable rock like sandstone or limestone located between impermeable rock layers like shale rocks are folded into an anticline oil and gas can move upward in the reservoir rock and accumulate in the upper region of the anticline Fault Trap: faulting can shift permeable and impermeable rocks if the permeable rocks always have impermeable rocks above them, then an oil trap can form normal and reverse faults can form fault traps surface exploration can reveal faults to explore further 15

16 Salt Dome Trap: caused when "plastic" salt is forced upward salt dome pierces through layers and compresses the rocks above this upward motion can cause a dome of impermeable rock to form with the oil and gas trapped along the edges of the dome Stratigraphic Trap: erosion can cause unconformities to form sections of permeable rock can become sandwiched between impermeable rock layers if oil is within the permeable rock, it will be unable to escape 16

17 Extracting petroleum drilling can take place on land, ice, or water a proportion of petroleum in a trap is under natural pressure and therefore, will be released naturally when tapped by a drill there will be another proportion of petroleum that will remain in the trap due to loss of pressure to overcome the loss of pressure, water is often pumped into wells to maintain the upward flow of oil the Alberta oil sands, also called tar sands, are an example of petroleum being extracted directly from the surface (open pit mining) because the petroleum migrates towards the surface and volatiles (e.g. water) are lost to the atmosphere, the petroleum experiences increased viscosity (i.e. thickness), thereby preventing it from spreading out and/or dissipating the reservoir consists of loose (unconsolidated) sediment that therefore, exhibits high porosity and permeability in some instances, steam is injected directly into the tar sands to mobilize the hydrocarbons, which are then recovered from pumps much like conventional crude oil 17

18 Petroleum is refined by: 1) distillation 2) cracking 3) reforming Refining Petroleum once petroleum is extracted from the sub surface and is de salted and de watered, it enters a distillation column heat is added to the column to separate the petroleum into fractions based on boiling points (cracking). the bottom fraction is removed to another column for further separation reforming involves heat, pressure, and the use of catalysts (speed up reaction rates) to reform different hydrocarbon compounds 18

19 19