Transcript Chapter 15
15 Mineral Resources Overview of Chapter 15 Introduction to Minerals Environmental Impact Associated with Minerals An International Perspective Increasing the Supply of Minerals Using Substitution and Conservation to Expand Mineral Supplies © 2012 John Wiley & Sons, Inc. All rights reserved. Introduction to Minerals Mineral An inorganic solid, occurring naturally in or on the earth’s crust with a precise chemical composition. Earth’s mineral are elements or compounds of elements that have precise chemical composition. Ex: sulfides-certain chemicals combined with sulfur and oxides are compounds in which elements are combined chemically with oxygen. Rock Naturally formed aggregate of minerals Igneous, Sedimentary, Metamorphic Ore Rock that contains enough of a mineral to be profitably mined and extracted. High grade ores contain relatively large amounts of particular minerals v.s lowgrade ores. © 2012 John Wiley & Sons, Inc. All rights reserved. Rock Cycle © 2012 John Wiley & Sons, Inc. All rights reserved. Important Minerals and Their Uses © 2012 John Wiley & Sons, Inc. All rights reserved. Mineral Distribution and Formation Abundant minerals in crust Aluminum Scarce minerals in crust Copper, and iron chromium, and molybdenum Distributed unevenly across globe If found in low abundance, mining is not profitable © 2012 John Wiley & Sons, Inc. All rights reserved. Formation of Mineral Deposits Result of natural processes Magmatic concentration As magma cools heavier elements (Fe and Mg) settle Responsible for deposits of Fe, Cu, Ni, Cr Hydrothermal processes Minerals are carried and deposited by water heated deep in earth’s crust Sedimentation Weathered particles are transported by water and deposited as sediment on sea floor or shore Evaporation Salts are left behind after water body dries up © 2012 John Wiley & Sons, Inc. All rights reserved. Discovering Mineral Deposits Scientists (geologists) use a variety of instruments and measurements Aerial or satellite photography Seismographs Combine this with knowledge of how minerals are formed © 2012 John Wiley & Sons, Inc. All rights reserved. Surface Mining Overburden must be removed to reach ore. Overburden is often discarded as spoil. Types of surface mining: open pit, dredging, area strip mining, contour strip mining, mountain top removal US legislation: Surface mining Control and Reformation Act of 1977 – requires mining companies to restore land so it can be used for the same purpose as before it was mined. Mining Law of 1872: encourages mining on public lands (excluding parks/wilderness). Must promise to pay $500 to improve the land. Can buy the land for $2.50-$5.00 an acre and do nearly anything with it! Surface Mining: Extracting Minerals Surface Mining Mineral and energy resources are extracted near Earth’s surface Remove soil, subsoil and over-lying rock strata (overburden) More common and less expensive. More common because less expensive Two kinds Open pit - large hole is dug Strip Mine - trench is dug. Then a new trench is dug parallel to the old one; the overburden from the new trench is put into the old trench, creating a hill of loose rock called a spoil bank. © 2012 John Wiley & Sons, Inc. All rights reserved. Open Pit Mine Big hole in the ground. Iron, copper, sand, gravel, etc Dredging Scrape underwater mineral deposits Area Strip Mining Strips a trench, filling the trench behind. Can leave wavy hills called spoil banks. See page 344 in your text Contour Strip Mining Cuts terraces around the sides of a hill. Leaves a bank of soil called “highwall” Surface Mining - Open Pit © 2012 John Wiley & Sons, Inc. All rights reserved. Surface Mining - Strip Mine © 2012 John Wiley & Sons, Inc. All rights reserved. Extracting Minerals Subsurface Mining Mineral and energy resources are extracted from deep underground deposits. Disturbs the land less than surface mining, but it is more expensive and more hazardous. Two kinds Shaft mine - direct vertical shaft into the vein of ore, which is hoisted up using buckets Slope mine - slanting passage where ore is lifted our using carts. Sump pumps keep the subsurface mine dry, and a second shaft is usually installed for ventilation. © 2012 John Wiley & Sons, Inc. All rights reserved. Subsurface Mining - Slant Mine © 2012 John Wiley & Sons, Inc. All rights reserved. Sub-surface mining Used frequently with coal and deeper metal ore deposits. Disrupt less land, but has health hazards such as black lung disease. Possible risk of cave ins. Subsurface Mining - Shaft Mine © 2012 John Wiley & Sons, Inc. All rights reserved. Smelting Separation of ore from gangue Melting metal Metal ore Conversion to product Recycling Discarding of product Surface mining Scattered in environment Steps Mining exploration, extraction Processing transportation, purification, manufacturing Use transportation or transmission to individual user, eventual use, and discarding Environmental Effects Disturbed land; mining accidents; health hazards; mine waste dumping; oil spills and blowouts; noise; ugliness; heat Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat Environmental Effects of Mining Processing Minerals Smelting- process in metallic minerals involves ore being melted at high temps to separate impurities from the molten metal. Done in a blast furnace. © 2012 John Wiley & Sons, Inc. All rights reserved. Mining and the Environment Disturbs large area Destroys existing vegetation, this land is particularly prone to erosion with wind erosion causing air pollution and water erosion polluting nearby waterways and damaging aquatic habitats. US- current and abandoned mines cover 9 million hectares Prone to erosion Uses large quantities of water Must pump water out of mine to keep it dry. © 2012 John Wiley & Sons, Inc. All rights reserved. Acid Mine Drainage Acid Mine Drainage (AMD) Pollution caused when sulfuric acid and dissolved lead, arsenic or cadmium wash out of mines into nearby waterways. Two examples in the North American of acid mine drainage is Berkeley Pit Superfund site near Montana and Britannia Beach in Canada. © 2012 John Wiley & Sons, Inc. All rights reserved. Cost Benefit Analysis of Mine Development Environmental economists suggest that before a decision is made to develop a mine, a cost-benefit analysis should be performed including the benefits of the mine in dollars terms v.s. the benefits in dollar terms of preserving that land intact for wildlife habitat, ranchers, farmers, indigenous people, watershed protection and recreation. © 2012 John Wiley & Sons, Inc. All rights reserved. Environmental Impacts of Refining Minerals © 2012 John Wiley & Sons, Inc. All rights reserved. Environmental Impacts of Refining Minerals 80% or more of mined ore consists of impurities - called tailings. Contain toxic materials and usually left in giant piles on the ground or in near the processing site. Smelting plants emit large amounts of air pollutants (sulfur) Requires a lot of energy (fossil fuels combustion) © 2012 John Wiley & Sons, Inc. All rights reserved. Restoration of Mining Lands When a mine is no longer profitable, the land can be reclaimed, or restored to a semi-natural condition. Restoring land degraded by mining is called derelict lands Goals: prevent further degradation and erosion of land, eliminate local sources of toxins and make land productive for another purpose. Involves filling in and grading the land to its natural contours, then planting to hold soil in place. Needs funding. Reclaimed Coal-Mined Land Surface Mining Control and Reclamation Act of 1977. © 2012 John Wiley & Sons, Inc. All rights reserved. Restoration of Mining Land Creative Approaches - Use Created Wetlands Trap and filter pollutants before they get into streams Initially expensive, but cost effective compared to using lime to decrease acidity - Use Phytoremediation Use of specific plants to absorb and accumulate toxic materials in soil © 2012 John Wiley & Sons, Inc. All rights reserved. Minerals: An International Perspective Highly developed countries Rely on mineral deposits in developing countries They have exhausted their own supplies Developing countries Governments lack financial resources to handle pollution Acid mine drainage, air and water pollution © 2012 John Wiley & Sons, Inc. All rights reserved. North American Consumption of Selected Metals © 2012 John Wiley & Sons, Inc. All rights reserved. Will We Run Out of Important Metals? Mineral Reserves Mineral deposits that have been identified and are currently profitable to extract Mineral Resources Any undiscovered mineral deposits or known deposits of low-grade ore that are currently unprofitable to extract Estimates of reserves and resources fluctuate with economy Difficult to forecast future mineral supplies © 2012 John Wiley & Sons, Inc. All rights reserved. Increasing Supply of Minerals – Locating and Mining New Deposits Many known mineral deposits have not yet been exploited Difficult to access Insufficient technology Located too deep Ex: 10km or deeper © 2012 John Wiley & Sons, Inc. All rights reserved. Minerals in Antarctica No substantial mineral deposits identified to date Antarctic Treaty (1961) Limits activity to peaceful uses (i.e. scientific studies) Madrid Protocol (1990) Moratorium on mineral exploration and development for minimum of 50 years © 2012 John Wiley & Sons, Inc. All rights reserved. Minerals from the Ocean May provide us with future supplies Extracting minerals from seawater Mining seafloor - Manganese nodules © 2012 John Wiley & Sons, Inc. All rights reserved. Advance Mining and Processing Technologies Special techniques to make use of large, lowgrade mineral deposits world-wide Biomining Using microorganisms to extract minerals from low-grade ores © 2012 John Wiley & Sons, Inc. All rights reserved. Finding Mineral Substitutes Important goal in manufacturing Substitute expensive/scarce mineral resources for inexpensive/abundant ones Examples: Using plastic, glass or aluminum in place of tin Using glass fibers instead of copper wiring in telephone cables © 2012 John Wiley & Sons, Inc. All rights reserved. Mineral Conservation Includes reuse and recycling of existing mineral supplies Reuse - using items over and over again Reduces both mineral consumption and pollution Recycling- converting item into new product Reduces land destruction from mining Reduces solid waste © 2012 John Wiley & Sons, Inc. All rights reserved. Changing Our Mineral Requirements Must change our “throw away” mentality © 2012 John Wiley & Sons, Inc. All rights reserved. Traditional Flow of Minerals Waste produced in all steps in the production of minerals © 2012 John Wiley & Sons, Inc. All rights reserved. Sustainable Manufacturing © 2012 John Wiley & Sons, Inc. All rights reserved.