Geologic Resources. Geologic Resources and Society. Geologic Resources and Society

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Jennifer Shepherd
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1 Geologic Resources Our entire society rests upon - and is dependent upon - our water, our land, our forests, and our minerals. How we use these resources influences our health, security, economy, and well-being. John F. Kennedy, 1961 Geologic Resources and Society Bottom-line, our entire civilization is based upon mineral resources. For example, Most manufactured goods are made of metals. Most of the energy we use comes from fossil fuels or fissionable metals. Food production depends on fertilizes. Buildings and roads are made from mineral/rock materials. Geologic Resources and Society Historically, Mankind has mined and quarried mineral since ancient times. First mineral known to be mined was flint (Ohio s State mineral). Early peoples also mined ochre for pigment. Egyptians mined native metals from stream beds as early as 3000 to 3700 BC, and began quarrying stone for building around 2600 BC. 1

2 Geologic Resources and Society Today, World crude mineral production exceeds $14 trillion annually. U. S. raw materials production exceeds $40 billion annually, and in processed form exceeds $400 billion annually. Total world commodity exports exceed $2 trillion annually. Raw and processed mineral exports are $ billion annually. Geologic Resources in Ohio In Ohio in 1999, value of non-fuel minerals was $780 million. value of coal was $643 million. value of oil & gas was $346 million. Total value was nearly $1.8 billion. Details can be found at: oh_geol/01_no1/1999mi.htm Resource Consumption Yearly per capita consumption of Americans requires: 18,000 kg (40,000 lbs) of nonfuel resources, and 8,000 kg of energy resources. 2

3 Types of Resources I. Energy (fuels) II. Metals III. Nonmetals (industrial minerals) IV. Water Definitions Mineral deposit - local enrichment (concentration) of one or more minerals. Enrichment or Concentration factor - ratio of concentration of particular metal in mineral deposit to that in average continental crust. Ore deposit - a rock body containing one or more minerals which can be mined at a profit with current technology and under current economic conditions. Resource vs Reserve Resources - total quantity of a given material in all deposits, discovered and undiscovered. Reserves - quantity of a given material that has been found and could be exploited with existing technology. See fig

4 Resources Renewable resources - can be replenished on a human time-scale (ie, wood) or can be used without actual depletion of supply (ie, solar energy). Nonrenewable resources - are not produced at present or are being produced at rates much slower than current consumption (ie, fossil fuels). Energy Resources A. Fossil Fuels 1. Oil and Natural Gas 2. Oil Sands and Oil Shale 3. Coal B. Abiogenic Methane Methane formed by inorganic process, major amounts may be trapped in Earth s mantle. Energy Resources C. Nuclear 1. Nuclear Fission Uranium ores 2. Nuclear Fusion D. Renewable Energy Sources 1. Solar energy 2. Geothermal energy 3. Hydropower 4. Wind energy 4

5 Hydrocarbons in Rocks Occurrence requires: 1. Source rock geologic formation in which hydrocarbon originates. 2. Reservoir rock porous, permeable rock in which hydrocarbons accumulate. 3. Hydrocarbon trap any rock barrier that accumulates hydrocarbons by preventing upward migration. Cap rock- impermeable rock that prevents upward migration of hydrocarbons. 4. Thermal maturity need sufficient time / temperature to cook the oil. Hydrocarbon traps Anticlines/Domes Faults Sandstone lenses / pinchouts Unconformities Reefs Salt domes See fig. 21.3, Box 21.1 Oil Fields Regions underlain by one or more oil pools. Locations of major North American oil fields is shown in fig

6 Oil Sands & Oil Shales Oil Sands or Tar Sands sedimentary rocks containing a very thick, semisolid, tar-like petroleum (asphalt-cemented sands). Oil Shales rock, often but not always shale, containing kerogen, a waxy solid formed from remains of plants, algae and bacteria. See fig for locations of major North American deposits. Coal Organic sedimentary rock formed by compaction of plant material. Varieties of Coal (Table 21.1): Peat - first combustible form, ~15% carbon. Lignite - ~30% carbon Bituminous % carbon Anthracite - 90% carbon Occurrence of Coal Depositional Environment Remains of land plants were deposited in swampy areas in which plant growth was abundant and burial was rapid in standing water in order to protect debris from decay. Coal fields in United States (fig ). 6

7 Geologic Ore-forming Processes A. Magmatic Processes 1. Crystal settling in layered igneous plutons (chromium, platinum, see fig ). 2. Pegmatites (Be, Li in beryl). 3. Kimberlite pipes (diamonds). 4. Volcanic vents (native sulfur). Geologic Ore-forming Processes B. Hydrothermal (hot-water) Processes Hot-fluids are the most important source of metallic ore deposits. 1. Magmatic waters (porphyry copper, gold). 2. Seawater (massive sulfides, Cu, Ni, Pb). 3. Basinal brines (Miss. Valley type Pb-Zn). 4. Metamorphic waters (tunsten, Cu). 5. Groundwaters (uranium, sulfur). See figs and Geologic Ore-forming Processes C. Sedimentary Processes 1. Physical sedimentation i) Flowing water - (Placer Au, Pt, diamonds). ii) Glacial deposits (sand and gravel). iii) Wind (sand). 2. Chemical sedimentation i) Precipitation from water a. evaporites (rocksalt, gypsum, limestone, borax). b. chemical deposits (banded iron). 3. Organic sedimentation i) Hydrocarbons (oil, gas, coal). ii) Other organic activity (phosphates, sulfur). 7

8 Geologic Ore-forming Processes D. Weathering Processes 1. Laterite deposits (bauxite, clays iron) 2. Supergene enrichment (see fig ) E. Metamorphic Processes 1. Graphite 2. Precious gems (garnet, sapphire, ruby, emeralds). Resources and Plate Tectonics Metal Ores Divergent boundaries Hydrothermal seawater circulation in submarine rift valleys (fig ). Convergent boundaries Hydrothermal fluids on flanks of island arcs (fig ). Mantle plumes (Hot-spots) Intracontinental igneous intrusions and groundwater hydrothermal circulation. Fossil Fuels Formation of oil by accumulation of organic-rich sediments, and the structural traps to contain the oil pools are naturally associated with active plate boundaries (see fig for example). 8

Natural Resources. Geology of the Hawaiian Islands. Please finish assignments. Any Questions? Class April 2004

Natural Resources. Geology of the Hawaiian Islands. Please finish assignments. Any Questions? Class April 2004 Geology of the Hawaiian Islands Class 27 20 April 2004 Please finish assignments HW #7 You may turn it in Thursday in class. I will not accept it after that. All Virtual Field Trip quizzes. I will accept