Minerals and Rock Resources

1. Minerals and Rock Resources Chapter 12

2. Ore Deposits Ore � rock in which a valuable or useful metal occurs at a high concentration where it is economically viable to mine eg iron ore Concentration Factor (CF): CF = Cm Cmc Cm = Concentration factor of the metal in the ore Cmc = Concentration of the metal in average continental crust NOTE: The higher the CF - the richer the ore

3. Fig 12.2: Large crystals of beryl in pegmatite rock

4. Examples of Metals obtained from Ores Aluminum (in bauxite rock) � vehicles Iron (in iron ore) - appliances & vehicles Metals for conductors or semi-conductors Gems, gold, and silver � jewelry Lead from galena (PbS) Copper (Cu) from malachite and azurite Zinc from sphalerite (ZnS) Many other metals found in rocks

5. Cost Factors Concentration Factor (CF) 4 to 25,000 times x CF - highly variable amounts World demand and many market factors Energy cost Human/labor cost Distance to processing or market Environmental cost (including remediation)

6. Distribution of Economic Minerals Globally, very un-even distribution Some countries have plenty � �export nations� Some countries have none � �import nations� Un-even distribution of raw materials & mineral resources wars are fought

7. Fig 12.6 a: Copper & molybdenum deposits in Americas

8. Fig 12.6 b: Precious metal distribution in U.S.

9. Types of Mineral Deposits Igneous Rocks and Magmatic Deposits Pegmatite Kimberlite (bringing diamonds to surface) Hydrothermal Ores hydrothermal Relationship to Plate Margins - subduction zone Sedimentary Deposits Banded iron formation Evaporite Other low-temperature ore-forming processes Placers

13. Fig 12.3

15. Figs 12.4 a, b & c

18. Figs 12.7 a & b

20. Fig 12.8: Layers of banded iron formation, BIF

22. Fig 12.9

24. Figs 12.10 a & b: Placer deposits

25. Mineral and Rock ResourcesExamples of Economic Uses Metals � iron, aluminum, copper, lead, zinc, nickel, cobalt, gold, silver, or platinum Nonmetallic Minerals � sulfides, lime (calcium carbonate), sulfur, halite, clay, gypsum, or potash Rock resources � most abundant quantity of earth resources we use (particularly on Puerto Rico) Sand, gravel, limestone, quartz-rich sand, marble, granite & sandstone

26. Fig 12.12

27. Mineral Supply and Demand Global demand is always growing About 2% pre-World War II About 10 % World War II to mid-1970�s Demand is fluctuating now U.S. Mineral Production and Consumption U.S. population is only 4.5% of the world but consumes many times its share of the world supply

28. Fig 12.13

29. World Mineral Supply: FACTS World demand is always fluctuating Commodities do not follow fluctuating trends Mineral reserves eventual will be depleted Import/export relationships will fluctuate Technology often allows more access to difficult or low grade ore deposits Future mineral-resource shortages will occur and cause international tension

30. Table 12.2

31. Future Mineral Use: Some Options Considered Consider controlling consumption rates Reduce the consumption rates Hold these rates steady Carefully consider the facts: Globally the less developed nations are striving to achieve comparable standards of living as the technologically advanced countries enjoy Countries with fastest-growing populations do not have the largest mineral deposits and are the less-developed countries of the world!

32. Table 12.3

34. Fig 12.15

35. New Methods in Mineral Exploration Fact: the economically easy and profitable deposits are being depleted Geophysics is a useful aid to locating new deposits Gravity survey Magnetic survey Electrical property survey Geochemical surveying and prospecting is an increasingly popular exploration tool Remote sensing is expanding into exploration strategies

36. Fig 12.16: Geochemical prospecting

37. Remote Sensing Sophisticated but valuable exploration tools Useful to detect, record & analyze energy emitted off the earth Aerial photography Satellites Space shuttle & other manned missions Remote sensing is backed up with �ground truthing� old fashioned geologic mapping at surface Advances in geological sciences are directed toward integration of remote sensing & geochemistry & geophysics

38. Figs 12.17 a and b

39. Fig 12.18

40. Marine Mineral Resources Oceans � our new mineral frontier Sea water contains abundant dissolved minerals and many useful elements Most extraction techniques currently used are energy intensive & expensive Hydrothermal ore deposits along seafloor spreading ridges are a possible source of many materials Currently, they are too deep - of limited benefit Manganese nodules are widely distributed on the ocean floors; a promising solution. Many political, environmental, and legal obstacles must be overcome before they can be mined

41. Fig 12.20b: Manganese nodules on ocean floor

42. Fig 12.20 a

43. Conservation of Mineral Resources Overall need for resources is growing � MUST reduce this expansion Some mineral resources may be substituted by other, more abundant resources eg. Plastics replacing automobile parts Recycling � many metals are successfully recycled More recycling MUST be done Not all commodities are easy to recycle Measures to reduce demand is the key �

44. Table 12.4

45. Impacts of Mining Activities Very stressful to the environment Must be carefully planned Must be safe to miners and their neighbors Must be contained: water & air pollution is a major problem

46. Underground Mines Often hard to see where they are located area of disturbance is local Miners place the tunnels close to ore body to cut down on waste Once mines are closed they can be sealed with the non-ore rock (waste rock) Surface collapse general limited and controllable with modern mine reclamation practices Old & abandoned mines are still a problem

47. Fig 12.23 a: Collapse of land in old copper mine, Arizona

48. Fig 12.23 b: Subsidence pits over abandoned underground coal mines in Wyoming

49. Surface Mines Open-pit Mining Mine a large ore body located near the surface Permanent changes to local topography will occur Strip mining Most ores occur in a layer that generally is parallel to the surface The ore zone is overlain by vegetation, soil, non-ore rock that must be removed Spoil banks are designed to collect the waste rock Current reclamation law requires must be returned to the pit & original soil replaced (expensive but vital)

50. Fig 12.24 a

51. Fig 12.24 b: Bingham Canyon copper mine

52. Fig 12.25 a

53. Fig 12.25 d: Successful mine reclamation

54. Mineral Processing Mineral extraction is environmentally hazardous Ore rock is ground or crushed for extraction The fine waste material is placed in tailings The tailings are exposed to wind and weather Harmful elements such as mercury, arsenic, cadmium, or uranium can be leached out The surface and subsurface water systems are often contaminated Chemicals used in ore extraction must be controlled and not just dumped Smelting ores to extract metals, often produce metallic exhaust gas & ash, sulfur oxide and acid rain pollution

55. Fig 12.26 b