Welcome to GLG101C Introduction to Geology Fall 2004 Professor James Tyburczy
Department of Geological Sciences
	Chapter 22 Energy and Mineral Resources

Chapter 22 Energy and Mineral Resources from the Earth

Check out the USGS Energy Resources Site

Our civilization currently depends on energy and mineral resources that are extracted from the Earth.

• Reserves are known deposits that can be economically and legally extracted today
• Resources are an estimate of entire amount of material that ever will be available, including known reserves, uneconomic (unprofitable) deposits and deposits to be discovered in the future (very uncertain)
• U.S. Energy Use 2000: Petroleum + natural gas + coal = Fossil fuels = 85 % of energy use;
• Nuclear energy = 8%; Hydroelectric = 3%; Solar+wind+wood+geothermal <1 %

Energy Resources - Fossil fuels (petroleum, natural gas, coal), fuels for nuclear energy, geothermal energy

Petroleum and Natural Gas

• These are fossil fuels - Millions of years ago the energy from the sun plus CO2 plus H2O were converted to oil and gas. They are non-renewable - when we use them up today they are gone forever
• Petroleum is a liquid made of hydrocarbons (compounds made up primarily of carbon and hydrogen). It is less dense than water (it floats on water).
• Natural Gas is primarily methane gas (CH₄)
• Both are formed from marine animals and plants (phytoplankton) (note importance of photosynthesis) deposited in shallow seas (marine sediments), protected from exposure to air, heated to about 50 - 100°C (not hotter or cooler)
• After formation, oil and/or gas must migrate to a place where they can be trapped - need a good permeable source rock overlain by an impermeable cap rock (oil trap)
• Good oil traps are found in subsurface anticlines, fault traps, salt domes - subsurface geologic structures
• Geological exploration for oil and gas concentrates on locating likely-looking subsurface structural traps, then they must drill ($$) to find out whether there actually is oil there or not
• Global distribution of oil and natural gas
• The Middle East and the Caribbean-Gulf of Mexico regions together contain about 2/3 of the world's reserves of oil
• Global Reserves of oil are about 45 years worth - at present rate of consumption
• Global Resources of oil are about 85 years worth at present rate of consumption
• We have about 35 years of reserves of natural gas in the U.S.
• In the past, natural gas was most often pumped where it was found in association with oil, but more recently it has become profitable to mine deposits that consist of natural gas only
• Globally - the U.S. and republics formerly in the Soviet Union have large reserves of natural gas

Sources of oil and natural gas sources of the future

• 1) Further global exploration - much oil has been found, but perhaps a few major finds are left to be discovered in China, the former USSR, and offshore on the continental shelves
• 2) Enhanced recovery - better methods of more completely extracting oil from the subsurface
• 3) Oil shale, Tar Sands - very thick tars and oil in very impermeable shales and sandstones
  • Cannot be pumped out by normal methods
  • Possible large resource - perhaps as much as 100-150 years worth
  • But difficult to extract - new technologies needed and major environmental costs with extraction need to be dealt with (problems of surface strip mining and huge amounts of water needed to extract)
• 4) Improved efficiency and conservation
  • Auto use - 60 % of oil use in U.S. Fuel efficiency of cars could be improved greatly
• 5) Gas Hydrates (also known as Methane Hydrates or Clathrates) on the sea floor?
  • Gas Hydrates are made of cages of H2O molecules that surround and contain methane (CH4) molecules. Recently they have been found in a number of places on the ocean floor (on the continental shelves). Globally, they could represent a big source of methane. Can they be extracted economically, safely, profitably? It remains to be seen. Be alert for future developments in this field. Check here for more on Gas Hydrates. Here is a good introductory site on Clathrates.

Environmental problems oil extraction

• Oil spills from offshore drilling and during transportation
• Land subsidence
• Strip mining for oil shale and tar sand extraction
• Huge water supply needs for oil shale and tar sand extraction

Environmental aspects of oil and natural gas usage

• CO2 and global warming (see next chapter)
• Sulfur and nitrogen into the air make acid rain (bigger problem with oil than for natural gas)
• Sulfur and nitrogen into the air make smog (bigger problem with oil than for natural gas)

Coal

• Origin of Coal - swamps, bogs - land environments
• Peat (50 % carbon), lignite, bituminous coal, anthracite coal (low grade metamorphic rock - 95% carbon)
• U.S. reserves 300 - 400 year supply (shorter if usage increases)
• Environmental effects of coal mining -
  • Strip mining - land must be restored, acid drainage can occur if not treated carefully,
  • Underground mining (health hazards)
  • Water usage
• Environmental effects of coal usage
  • CO2 global warming
  • Sulfur in to air (acid rain and smog)
  • Solid residue ('fly ash') contains heavy metals

Nuclear energy: neutron + 235U = smaller nuclei + energy (lots) + more neutrons (chain reaction)

• In US nuclear energy provides about 20 % of electric power (about 8% of total energy needs). In France, nuclear energy provides about 75 % of electrical power
• 235U is 0.7% of natural abundance
• Uranium ores - Pitchblende, carnotite
  • Found in hydrothermal igneous environments and in sedimentary rocks (Colorado Plateau of Arizona, Utah, New Mexico, and Arizona)
  • Reserves in U.S. - enough to supply about 30 % of present day usage (4 times present day). Global resources - a hundred years or more
• Nuclear Waste
  • Plutonium-239 long lived (half life = 24,000 years) and dangerous
• Short lived nuclei: Iodine-131 half life 8 days, Iron-59 half life 45 days, Strontium-90 half life 29 years
• Plutonium-239 needs to be isolated from human contact for at least 10,000 years
• Today wastes are stored 'temporarily' at each nuclear plant at which they were created - leakage problems (for example Hanford, Washington)
• Recommended method - Deep geological storage
• Stable geologic formation, no current volcanic or tectonic activity, no faulting, above water table
• Proposed site - Yucca Mountain, Nevada - rhyolitic tuffs - currently under study (since 1987)
• For military waste - WIPP (Waste Isolation Pilot Plant), Carlsbad, NM - in thick salt beds

Geothermal energy

• Hot fluids from surface percolate down to magma body
• Generally non-renewable
• Ground subsidence, waters may be very salty and contain heavy metals
• Potential use - limited, but may be very valuable in specific locations

Other possible future energy sources

• Solar energy
• Hydroelectric (today 3% of US energy use, 30 % of Canadian energy use)
• Wind energy
• Biomass
• Tidal energy
• Nuclear fusion
• Gas hydrates/clathrates?
• Conservation conservation conservation

Energy Future - Is there an energy crisis in the future? - Maybe

• At PRESENT levels of consumption, there exists enough oil, gas, coal and nuclear energy to last for several hundred years (costs will go up, environmental issue will be important). The US has 6 % of the world's population and consumes 30 % of the world's energy.
• So, will consumption levels remain flat? NO! Developing nations want to become developed.
• Global energy use will increase dramatically in the future, our reserves will last much less time than several hundred years.
• Technologies for hard to get fossil fuels (oil shale, tar sands) are developing slowly
• CO2 pollution and global warming are problems telling us we need to be careful about use of fossil fuels
• Oil production will likely peak at some point in the future and then start to decline
• Solutions? Conservation & efficiency will be increasingly important
• Nuclear plant and waste storage safety must improve
• Alternative energy sources - solar (and nuclear fusion, gas hydrates, oil shales?) must be developed more rapidly
• We will continue to be vulnerable to politically-caused shortages

Mineral Resources from the Earth

USGS Minerals Research Program web site

• In US about 20,000 pounds per person of materials are consumed each year
• Ore - means profitably mine-able material - some kind of natural process has acted to concentrate the material of interest in a single place where we can mine it
• Extraction of mineral and metal materials and ores will continue to be an important source of materials, but increasingly recycling is becoming an important source of metals - perhaps 50% of iron is recycled

Formation of a mineral deposit requires:

• A source of the material with access to a natural transport mechanism
• A natural transport mechanism
• A deposition mechanism and deposition site. The near-surface of the earth is a good place for mineral deposition - it is fractured (lots of little pathways) and it is cool

Hydrothermal deposits

• Hydrothermal vein deposits- typically form sulfide minerals (such as FeS2 pyrite). Copper, lead, zinc, gold, silver, tin, molybdenum, tungsten, cobalt ores are formed this way
• Disseminated hydrothermal deposits - copper (esp. in AZ), lead, zinc

Ore bodies associated with igneous intrusions

• Crystal settling and segregation in magma chamber - chromium, platinum, magnetite
• Pegmatites - Lithium, beryllium, gemstones (emeralds, sapphires)
• Kimberlites - Ultramafic volcanic rocks, very rapid eruption from great depths - diamonds, other gemstones

Sedimentary Ore deposits - bodies formed by surficial processes and weathering

• Sedimentary rocks themselves (formed by normal sedimentary processes) - limestone, quartz sand, sand and gravel, high purity clays, salt and other evaporite deposits
• Chemical precipitation in layers - iron (effects of oxygen in atmosphere), manganese, copper
• Placer deposits - stream action concentrates heavy minerals; gold, platinum, diamonds, tin

Substitutes, Recycling (today we have about 50% recycling of metals), Conservation

Ore Deposits and Plate Tectonics

• Igneous processes bring chemical elements from Earth's interior to the surface
• Relation between ore deposits and sites of current and ancient igneous activity
• Deep ocean floor, non-plate boundary - manganese nodules, other untapped resources?

Finding New Mineral Deposits - not sufficient mineral resources for everyone in the world to live at US standard of living

• New exploration on ocean floor (national economic zone limits)

Sustainable Development