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Mineral Resources l Society and standard of living critically dependent upon availability of mineral and energy resources l Mineral resources here, energy.

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Presentation on theme: "Mineral Resources l Society and standard of living critically dependent upon availability of mineral and energy resources l Mineral resources here, energy."— Presentation transcript:

1 Mineral Resources l Society and standard of living critically dependent upon availability of mineral and energy resources l Mineral resources here, energy in the next chapter

2 A few of the many mineral products in the typical American home

3 Mineral Resources Use of minerals in the US > than 18,000 lbs per person each year

4 Mineral Resources l Infrastructure of manufacturing, transportation equipment, etc. F Capital, material, energy for manufacture and transportation l Much of history (including wars) can be explained in terms of haves and have-nots with respect to mineral and energy wealth

5 Flow diagram of non-fuel mineral resources & their role in US economy Value of processed materials = $351 Billion (310 domestic + 41 imported) = ~ 5% of GDP, but GDP would be much lower without it

6 Mineral Resources l Resources are all around us, but too dispersed to be of any value l Economic implications! F Never completely run out of anything F Simply become too expensive to produce  Mineral deposits when concentrated by various geologic processes since Earth created ~ 4.5 Ga

7 Igneous Processes 1) Very valuable minerals- dispersed, but worth scavanging Example: Kimberlite pipes and diamonds

8 Igneous Processes 2) Igneous : 2) Igneous Concentration Mechanisms: a) Crystal settling

9 Igneous Processes 2) Igneous : 2) Igneous Concentration Mechanisms: b) Concentrating in residual liquids as magma crystallizes Water and many rare elements don’t incorporate in common minerals Remain and concentrate in late melts at the top of a pluton Often the water pressure in the late melts builds to the point that it fractures the overlying rock and material escapes as hydrothermal fluids

10 Igneous Processes 2) Igneous : 2) Igneous Concentration Mechanisms: b) Concentrating in residual liquids Examples: Examples: F Pegmatites: Water-rich melts with concentrations of otherwise rare elements: gems, Li (batteries), Be, REE (semiconductors) F Hydrothermal Cu, Au, Ag, Hg, Pb, Zn.... s Porphry Cu at subduction zones late fluids  veins and cracks or more permeating s Massive sulfide Cu: at mid-ocean ridges (now found where subducted, uplifted, and eroded)

11 A typical cupola area at the roof of a pluton 8 cm tourmaline crystals from pegmatite 5 mm gold from a hydrothermal deposit Contact metamorphic deposits

12 Massive sulfides occur at mid-ocean ridges where recirculating seawater helps withdraw ore and concentrates it as it cools again when it reaches the seabed “Black smoker” on the East Pacific Rise: Fe-Cu-Zn sulfide precipitates

13 l Exploration techniques use models F Plate tectonics is a very useful model s Subduction zones locate porphry Cu s Massive sulfides may be found where oceanic crust slivers onto continents l Also use geophysics and geochemistry to locate ores Porphry Cu deposits in the Americas slivers of oceanic crust

14 Metamorphic Processes 3) Metamorphic : 3) Metamorphic Concentration Mechanisms: Contact metamorphism occurs at the contact between hot magma and cool country rocks  replacement ores (include Cu, W, Sn, Pb, Zn…) Calcite (CaCO 3 ) Sphalerite (ZnS) Scheelite (CaWO 4 ) Fluorite (CaF 2 ) Replacement ore of the Tem-Piute Mine, Nevada. Mined for tungsten.

15 Metamorphic Processes 3) Metamorphic : 3) Metamorphic Concentration Mechanisms: Regional metamorphism occurs over broad areas due to mountain-building processes  local concentrations of talc, graphite, asbestos, garnet & corundum (abrasives) Fist-sized garnets created by regional metamorphism, Gore Mt, New York. Mined for sandpaper.

16 Sedimentary Processes 4) Sedimentary : 4) Sedimentary Concentration Mechanisms: Clastic processes involve transport and deposition: F Sand and gravel (big $$) from old river channels, glacial deposits, deltas F Placer deposits of weathering-resistant and heavy minerals (Au, Ag, diamond, garnet) Gold nugget, California (2 cm) Placer diamonds, Namibia (3 cm across)

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18 California’s gold rush of the : Numbers are thousands of ft 2 of rock debris washed down from the hills or accumulated in the bay Record nugget was 162 lbs of pure gold One miner recovered 30 lbs of gold from 4 ft 2 in a month Miners at the Volcano camp sometimes found $370 worth of gold in a single panful

19 Sedimentary Processes 4) Sedimentary : 4) Sedimentary Concentration Mechanisms: Precipitates: F Marine: limestone, phosphate, Precambrian Fe ores (over 700,000,000 yrs ago when more oxidizing atmosphere), Mn nodules, evaporites (salt, gypsum) plus K, B, some metal-rich brines F Fresh-water precipitates are rarely economic

20 Figure 14-8: Marine evaporite deposits of the USA

21 Sedimentary Processes 4) Sedimentary : 4) Sedimentary Concentration Mechanisms: Biological deposits: F Phosphate = fish bones and teeth, guano  fertilizers F Diatomaceous earth & many limestones Weathering: F Bauxite = Al in zone of leaching in laterites (highly leached tropical soils) F Supergene enrichment of Cu

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24 Mineral Resources The time-frame of resources is important l Non-renewable resources are created on our time-scale (won’t add much in next 10 Ma) F No sustained yield like crops, timber… l “Resources” = useful materials that can be extracted and made into a useful commodity at a profit (either now or in the reasonable future) l “Reserves” = that portion of a resource that is identified and currently available (legally and economically extractable at the time of evaluation) Resources thus = reserves + sub-economic + speculative estimates

25 Marginally Economic Subeconomic Economic Identified Undiscovered In known districts In undiscovered districts or forms Reserves Marginal Reserves Subeconomic Resources Hypothetical Resources Speculative Resources Figure 14.2: USGS classification of mineral resources Increasing degree of geological assurance

26 Mineral Resources Consumption, Resources, and Availability The typical evolution curve for a non-renewable resource

27 Consumption, Resources, and Availability Growth stages: 1) Demand increases exponentially For non-renewable resources: 2) Deplete the easy to find, highly concentrated and shallow resources Much depends on our ability to keep these resources in production time production rate (1)(2)

28 Consumption, Resources, and Availability When do we do when we run out?? ,00010, Average Crustal Rocks High-U Granites Black Shales Phosphoria Formation Original Rich U finds Log Rock Tonnage Uranium Concentration Grade vs. Quantity of Uranium in the upper km of crust in the USA Probable Richest Ore ppm %

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30 Only 12 have cumulative demand < domestic supplies by 2000Only 12 have cumulative demand < domestic supplies by 2000 Only last 3 does US produce as much as we consume in US each year (Li, P, Mo)Only last 3 does US produce as much as we consume in US each year (Li, P, Mo) Reserves of > ½ used up by 2020Reserves of > ½ used up by 2020 Commodity In USA % Produced Demand (tons) Reserves/Cumulative Demand Foreign sources (% Imported) USWorld 43 Brazil 56, Argentina Berylluim 63 > Algeria 31, Spain Mercury 2, Australia 48, Canada Titanium 460, Canada 39, Japan Iron 87,000, Peru 28, Ireland Barite 2,500, Canada 27, Mexico Lead 700, South Africa 54, Chile Vanadium 6, Canada 24, Chile Copper 1,700, Canada 59, Mexico Sulfur 13,000, Australia 43, Malaysia Rare Earths 18, Lithium 3, Phosphate 34,000, Molybdenum 30, Canada 46, Mexico Selenium Availability and Demand of 32 “Critical” Non-fuel Mineral Commodities (1978)

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32 Consumption, Resources, and Availability When do we do when we run out?? F Search harder, dig deeper, find more (and pay more) F Import (foreign debt and dependence) F Find a substitute (synthetics replace metals, cotton…) F Conserve (use less or be more efficient) F Recycle (OK for metals, glass, but has limits) F Steal somebody else’s (war) F Do without

33 l Processing of a typical metal sulfide ore (copper, lead, zinc, molybdenum...) Environmental Impacts of Mineral Consumption, Mining, and Processing

34 l Surface mining  open pits like Bingham Canyon near Salt Lake (or Helena, MT) Bingham Canyon open pit Cu sulfide mine, Utah The World’s largest hole in the ground

35 Environmental Impacts of Mineral Consumption, Mining, and Processing l Surface mining Mining ruptures the weathered barrier and exposes the interior to the environment

36 Environmental Impacts of Mineral Consumption, Mining, and Processing l Sub-surface mining  less impact on site, but still exposes ore to water

37 l Materials are relatively toxic when exposed at the surface F Water  weathering, solution  toxic metals + sulfuric acid into surface & groundwater environment F Est. 550,000 abandoned mines in USA contaminate 19,000 rivers and streams F Collapse of old excavations poses a serious threat as well Environmental Impacts of Mineral Consumption, Mining, and Processing Acidic and Fe-rich water from an abandoned sub- surface tunnel pours into Beartrap Creek, which flows into the prime trout waters of the Blackfoot River, Montana

38 Mine tailings, Bingham Canyon open pit Cu mine, Utah

39 White streaks of zinc leached from a tailings pile and redeposited downslope. Colorado.

40 Smelting releases SO 2 to the atmosphere creating acid rain Mining Pollution Ducktown TN Sudbury, Ontario

41 Strip Mining- remove shallow surface cover and deposit such as coal, Fe, Mn, or phosphate that extends over a broad area Mining Pollution

42 Adverse effects include: F Removal of soil F Exposing ore F Polluting water F Disrupting drainages F Asthetics Mining Pollution Strip phosphate mine. Florida Contaminated water from a strip coal mine, Illinois

43 Dredging- excavation, sifting, and redepositing of sediment as remove placer minerals

44 Dredging rarely exposes fresh toxic ore, but severely disrupts a river valley or bed

45 Pad must be lined Note dam

46 Heap-leach pad extracting gold, Winnemucca, Nevada Keeping cyanide from entering the groundwater system is of critical importance

47 Minimizing the impact of mineral development l Environmental regulation F Most degradation is due to past mining practices that are now illegal in 1 st world F US smelters have stringent air quality standards F Water pollution containment and land reclamation plans

48 Mining Reclamation 1977 Surface Mining Control and Reclamation Act (SMCRA) l Created the Office of Surface Mining and several branches in mining states l Establishes standards and funds federal and state agencies l Coordinated federal and state efforts to regulate pollution, subsidence, and restoration of affected lands for coal mining F Non-coal still left to individual states F Once states set up SMCRA standards they may apply them to non-coal and use SMCRA funds as they see fit

49 Mining Reclamation l Clean Air Act and Clean Water Act too, because these are public commons (note Tragedy of…) l NEPA applies to activities on federal lands only l USFS administers mining reclamation on National Forests l Some abandoned mines are bad enough to qualify as Superfund sites

50 Mining Reclamation Steps in Surface Mine Reclamation l If possible: Before begin, peel back and store soil

51 Mining Reclamation Steps in Surface Mine Reclamation l Drainage control and diversion at disturbed area

52 Steps in Surface Mine Reclamation l Add or replace topsoil and immediate seeding with rapidly growing species, such as rye grass

53 Steps in Surface Mine Reclamation l After initial grass dies back, permanent species take over. Can use as habitat, grazing, etc.

54 Dredge Area Reclamation

55 Ducktown Tennessee: Superfund Site

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59 Minimizing the impact of mineral development l Biotechnology F Use microbes (some genetically engineered) to oxidize, absorb, or leach pollutants F Bioassisted leaching uses critters to liberate metals for chemical leaching F Also use microbes to neutralize acid mine drainage

60 Recycling of Mineral Resources

61 Scrap metal

62 Recycling of Mineral Resources Urban Ore F Landfills may contain useful materials F Palo Alto: ash from incineration of sewage sludge contained 30ppm Au, 660 ppm Ag, 8000 ppm Cu, and 6.6% P F Not all cities are like this, of course, but we may find inexpensive ways to process low grade ores, since processing the sewage anyway


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