Mining

1. Mining

2. Mining for Ores An ore is an economically exploitable deposit

3. What is an orebody? An occurrence of minerals or metals in sufficiently high concentration to be profitable to mine and process using current technology and under current economic conditions.

4. Economically Important Metal Concentrations in Earth’s Crust Note for comparison: Silicon 28% Oxygen 46%

5. What is ore grade? • Weight percentage (base metals) • Grams/tonne or oz/ton (preciousmetals) Ore grade is the concentration of economic mineral or metal in an ore deposit.

6. Hydrothermal Ore Deposits As magma cools, more abundant metals (silicon, aluminum) deposit first Solidification of magma releases water - a hydrothermal solution Minerals precipitate from hydrothermal solution and deposit in cracks or veins in rock

7. Metamorphic Ore Deposits • Concentration of minerals caused by high temperatures and pressures • Examples: • Lead-zinc deposits in southeast B.C. • Diamonds • Garnets

8. Geyser or hot spring Hydrothermal solutions entering veins in rocks Ore deposit Alteration of rocks by heat and pressure Intrusion Hydrothermal and Metamorphic Ore Deposits zoning

9. Sedimentary Ore Deposits Deposition of dense, resistant minerals in streams, lakes etc, e.g. Placer gold Precipitation of minerals from lakes-oceans (Evaporite Deposits), e.g. Potash and Salt Deposits Accumulation, burial and petrification of vegetation, e.g. Coal Deposits.

10. Economic Geology • What is an economic geological resource? • A mineral that is heavily used in some human endeavor (e.g., metal ores) and therefore is an important part of domestic/international commerce. • What are some mineral resources that are economically important? • metals. examples? • non-metal resources. examples?

11. Economic Geology • What makes something into an economic resource? • Are we running out of mineral resources? How would you find this out? What do you need to know?? • Total discovered stocks • likely (but undiscovered) resources • speculative resources

12. Mineral Resources

13. Non-renewable Mineral Resource Depletion Curves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.

14. US Non-renewable Resource Reserves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.

15. Steps in Obtaining Mineral Commodities 1. Prospecting: finding places where ores occur 2. Mine exploration and development: learn whether ore can be extracted economically 3. Mining: extract ore from ground 4. Beneficiation: separate ore minerals from other mined rock 5. Smelting and refining: extract pure commodity from the ore mineral 6. Transporation: carry commodity to market 7. Marketing and Sales: Find buyers and sell the commodity

16. Mining is an Economic Activity • The decision to mine (or not to mine) a particular ore deposit depends upon: • an analysis of costs, benefits and risks • tangible (i.e. dollar profit) • intangible (i.e. hopes of stimulating the economy, fears of environmental damage)

17. Life Cycle of a Metal Resource

18. Prospecting: Finding Ores • Applying knowledge of association of ores with specific geological settings. • Using remote sensing techniques such as satellite imagery • Developing detailed maps of rock types and geological structures (faults, folds, intrusions). • Developing 3-d picture of geological structures containing ore. • Obtaining samples of ore for chemical analysis.

19. Mine Exploration and Development: Can an Ore be Extracted Economically? • Define size, shape and grade of ore body. • Grade, G: mass of commodity per mass of ore • Drill cores, though expensive, can be used to determine underground extent of ore • Estimate the mass of the commodity

20. Mine Exploration and Development: Can an Ore be Extracted Economically? • Design a profitable plan for mining. • Selecting appropriate mining techniques are just a small part of it! • Analysis of requirements to startup mine: capital, transportation, labor, etc. • Complying with governmental regulations. • Mitigating environmental damage. • Strategies for making profitability in a changing marketplace.

21. Mining: Extract Ore from Ground • Surface Mining: Scoop ore off surface or earth. • cheap. • safe for miners. • large environmental destruction.

22. Surface Mining • open pit mining: • circular hole in ground, with ramp circling down along sides, allows deeper ore to be reached.

23. Open-pit Mining

24. Strip Mining • strip-mining: scoop off rock overburden, and then scoop off ore material. • Economics of strip mining depend on stripping ratio • Large land area can be involved, especially for coal and bauxite.

25. Strip Mining

26. Contour Strip Mining

27. Mountaintop Mining

28. Underground or Subsurface Mining: • Use of shafts to reach deeply buried ores. • expensive. • hazardous for miners. • less environmental damage.

29. Underground Mining • A technology originating in antiquity. • A variety of configurations, depending upon conditions

30. Gradual shift toward surface mining Surface mining

31. Mining Issues Mine Safety: In U.S., stringent mining regulations have lead to a reduction in fatalities, both in terms of total deaths per year, deaths per person-hour worked, and deaths per ton mined. surface

32. Health Problems • collapse of mine. • fire (methane, coal dust, etc.). • asphyxiation (methane, carbon monoxide, etc.). • pneumoconiosis (from inhaling coal dust). • asbestosis (from inhaling asbestos fibers). • silicosis (from inhaling silicate dust). • heavy metal poisoning (e.g. mercury). • radiation exposure (in uranium mining).

33. Environmental Damage • Gaping holes in ground (old open pit mines). • Piles of mine tailings (non-ore removed from mines). • Accidental draining of rivers and lakes. • Disruption of ground water flow patterns. • Loss of topsoil in strip-mined regions (350 to 2,700 km2 in US alone). • Contamination from sulfuric acid (H2SO4) produced through weathering of iron sulfide (FeS2, pyrite) in tailings. • 4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4 • Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings.

34. Minerals and Rocks • What is a mineral? • naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure • What is rock? • solid, cohesive, aggregate of one or more minerals • Each rock type has a characteristic mixture of minerals

35. Beneficiation: Separate Ore Minerals from other Mined Rock • Ore rarely contains enough ore minerals to be refined as is. • Milling required to separate pure ore minerals from useless "gangue" minerals. • Milling techniques. • Grinding ore to fine powder. • Separation using flotation techniques: • powdered ores mixed with water and organic "collector" and "frother" compounds • collector are heteropolar molecule with one end that adheres to ore minerals • the other that adheres to frother coated air bubbles • Air forced through water then produces a foamy layer of concentrated ore mineral. • Environmental problems associated with mill tailings are similar to mine tailings.

36. Smelting and Refining: Extract Pure Commodity from Ore Mineral • Iron, from an iron oxide (Fe2O3, hematite) rich ore (such as a banded-iron formation, which also contains quartz). • coke (carbon from coal), ore, air, and limestone mixed in blast furnace.

37. Smelting and Refining: Environmental Problems • Production of huge piles of slag. • Emission of CO2, a greenhouse gas, into the atmosphere. • Pollution associated with the generation of electricity needed in anode furnaces (especially aluminum). • Sulfur dioxide emissions from the refining of sulfide ores are a major source of air pollution. The sulfur dioxide combines with water to produce sulfuric acid. • Release of heavy metals (As, Cd, Hg), present in trace quantities in sulfide ores, into the atmosphere.

38. Environmental Effects of Using Mineral and Energy Resources

39. Harmful Environmental Effects of Mining • Disruption of land surface • Subsidence • Toxic-laced mining wastes • Acid mine drainage • Air pollution

40. Cost of Production • Costs that scale with grade of ore. The lower the grade, • The more ore must be mined. • The more ore must be shipped to the mill. • The more ore must be milled. • The more tailings must be disposed of.. • Fixed costs. • Building a transportation infrastructure. • Refining ore minerals, once it has been milled. • Cost formula. • cost of producing a kg of commodity = • cost of producing a pound of ore / grade of ore • + fixed costs per kg of commodity

41. Cost Trends • Amount of commodities mined per year has generally increased. • Commodity prices can take big swings, but average prices during the last century often declined or remained constant. Cents per pound copper Ore grades have all decreased as milling technology has improved

42. How Long Will Mineral Resources Last? • An increase in the price of a scarce mineral resource can lead to increased supplies and more efficient use of the mineral, but there are limits to this effect.

43. Uneven Distribution of Mineral Resources • Abundant minerals • Scarce minerals • Exporters and importers • Strategic metal resources • Economic and military strength • U.S. dependency – four critical minerals • Sources?

44. Supplies of Mineral Resources • Available supply and use • Economic depletion • Six choices after depletion • Recycle, reuse, waste less, use less, find a substitute, do without • Depletion time

45. Effect of Market Prices on Supplies of Nonrenewable Resources • Role of economics in mining • Standard economic theory • Limited free market in developed countries • Subsides, taxes, regulations, import tariffs • Economic problems of developing new mines

46. Mining Lower-grade Ores • Improved equipment and technologies • Limiting factors • Cost • Supplies of freshwater • Environmental impacts

47. Ocean Mining (1) • Minerals from seawater • Minerals for ocean sediments • Hydrothermal deposits • Manganese-rich nodules

48. Ocean Mining (2) • Mining issues in international waters • Environmental issues