NEEP602 Course Notes (Fall 1996)
Resources from Space
Resource Limitations on Earth
Geologic Processes and the Formation of Mineral Deposits
- On the Earth:
- Surface of the Earth 172K GIF
- Interior of the Earth 144K GIF
- What is a Mineral Deposit?
- Ore Forming Processes 24K GIF
- Plate Tectonics and Ores 136K GIF
- Ore Forming Processes and Cycles
- Geologic Time and Ores
What is an Ore Deposit?
- Concentration of minerals
- Recoverable at a profit
- Dynamic function of economic, engineering, political, and environmental factors
US Bureau of Mines Box
- identified geologically and are economic at present
- Reserve Base
- reserves plus identified lower quality material
- reserve base plus any other concentration to be found in the future
Ore Minerals and Ore Forming Processes
- Ore mineral
- Gangue minerals
- Cut-off Grade
- Size of Deposit
- Surface Processes
- Weathering, Sedimentation (clastic and chemical)
- Subsurface Processes
- Actions of Fluids
- Magmas, Brines, Groundwater
- Chemical & Physical Processes
Ex: Surface Processes
- Chemical & Physical Weathering
- Regolith and Soils
- Removal of Soluble Constituents
- Redistribution of Material
Ex: Clastic Sedimentary Processes
- Beach Sands
- Gold, Titanium, Magnetite, Uraninite
- Ex: Witwatersrand, South Africa
Ex: Chemical Sedimentary Processes
- Precipitation from water
- Isolated Basins
- Marine: Gypsum, Halite, Sylvite
- Lacustrine: Trona (sodium salts)
- Banded Iron Formations
- Sedimentary Exhalative Deposits
Reserve and Resource Estimation
- Earth's mineral endowment = Resource
- Fraction which has been identified and can be extracted at a profit = Reserve
- Estimates of these rely on Geology and Statistics
- Based on actual observation
- Individual deposit data is collected and compiled
- Such estimates only give us measured and perhaps indicated reserves
- How can we know resources?
- Categorize favorable geological environments
- Particular commodities occur in only certain geological settings
- Searches can be focused after or during routine mapping
- Can identify probabilities of finding specific settings
- This may work with known deposit types but fails for those resources in deposit types not yet known or recognized
- Usually hinge on the assumption that the mineral reserve can be treated as a single homogenous population
- This allows estimates of the whole to be made from partial information
- NO information on the where; only the how much
- Several empirical observations have been made
Crustal Abundance Relation
- Reserves for some elements exhibit a constant ratio to their average crustal abundance
- Reserves for less explored commodities can be estimated from well explored ones
- See Fig 13-1 A. for such a plot 9K GIF
- Logarithmic increase in volume with an arithmetic decrease in grade
- Exact ratio varies with deposit type
- See Fig 13-1 B for example of Cu 7K GIF
Watch out for Extrapolation!
- Infinite resource with infinitely low grade
- Nonsense of course
- Neglects energy costs
- Assumes that the element/deposit remains the same in different rock
- Forms own mineral at "high" concentrations
- Substitutes in crystal structure at "low" concs.
Combined Estimates are BEST
- Ex: Oil and Gas in the U.S.
- Similar data hard to acquire for most metals
- Where present, a single country's data is often masked by world wide production
- Strategic minerals; definition changes
- Abnormal factor in nominally "free market"
- Most perfect form of mineral use
- Not possible with many things however
- (Will be KEY in space)
World Reserves and the Future
- Divide reserve figures by present consumption
- 1992 data shown in Figure 13-5 36K GIF
- Some things are in very short supply
Use Reserve Base Instead of Reserves?
- Provides a longer term perspective
- 1 to 5 times more material available than in reserve calculation
- However what is the fallacy with this logic?
Population and Standard of Living will Increase Significantly
- Therefore present consumption is a minimum for the future
- 2 to 3 times greater consumption as an average for the next 10-50 years is likely
- Maybe twice the time shown in the Table before we run out of certain materials
Additional Problems with this Summary
- Source of the numbers: compare early 1980's
- RB/P does not tell us the rate at which a commodity can be produced
- Doesn't tell us what price is needed to make the reserve base available
Price vs Consumption
- Availability can be markedly influenced by price
- Fig. 6.1 shows U.S. consumption vs Price 15K GIF
- Cut the price by factor of 10 = consumption will increase 20-50 times
How to Forecast Future Production?
- Look at past 20-30 years for guidance
16K GIF 9K GIF
- Examine and anticipate technological change
- How can we anticipate events like the oil embargo?
The Real Significance of these Numbers:
- How long to find reserves and put them into production?
- Reserves are of no use if left in the ground
- Exploration takes a long time
- Development can take a long time
- Time is Money
How does this apply to Space?
- Some rules the same, some different
- "crustal abundances"
- economies of scale
- substitution possible?
- role of recycling
- Technological constraints
References and a more complete treatment of mineral resources issues on the Earth can be found in my course Minerals as a Public Problem.
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