Transcript Chapter 8: Major Elements

Mineral Resources


Society and standard of living critically dependent
upon availability of mineral and energy resources
Mineral resources here, energy in the next chapter
A few of the many
mineral products
in the typical
American home
Mineral Resources
Use of minerals in the US > than 18,000 lbs per person each year
Mineral Resources


Infrastructure of manufacturing, transportation
equipment, etc.
 Capital, material, energy for manufacture and
transportation
Much of history (including wars) can be explained
in terms of haves and have-nots with respect to
mineral and energy wealth
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
Mineral Resources
Resources are all around us, but too dispersed to
be of any value
 Economic implications!
 Never completely run out of anything
 Simply become too expensive to produce
 Mineral deposits when concentrated by various
geologic processes since Earth created ~ 4.5 Ga

Igneous Processes
1) Very valuable minerals- dispersed, but
worth scavanging
Example: Kimberlite pipes and diamonds
Igneous Processes
2) Igneous Concentration Mechanisms:
a) Crystal settling
Igneous Processes
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
Igneous Processes
2) Igneous Concentration Mechanisms:
b) Concentrating in residual liquids
Examples:
 Pegmatites: Water-rich melts with concentrations of
otherwise rare elements: gems, Li (batteries), Be,
REE (semiconductors)
 Hydrothermal Cu, Au, Ag, Hg, Pb, Zn....
 Porphry Cu at subduction zones late fluids 
veins and cracks or more permeating
 Massive sulfide Cu: at mid-ocean ridges (now
found where subducted, uplifted, and eroded)
8 cm tourmaline crystals
from pegmatite
Contact
metamorphic
deposits
A typical cupola area at the roof of a pluton
5 mm gold from a
hydrothermal deposit
“Black smoker” on the East Pacific
Rise: Fe-Cu-Zn sulfide precipitates
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
slivers of
oceanic crust

Exploration techniques use models


Plate tectonics is a very useful model

Subduction zones locate porphry Cu

Massive sulfides may be found where
oceanic crust slivers onto continents
Also use geophysics and geochemistry
to locate ores
Porphry Cu
deposits in the
Americas
Metamorphic Processes
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…)
Fluorite (CaF2)
Calcite (CaCO3)
Sphalerite (ZnS)
Scheelite (CaWO4)
Replacement ore of the
Tem-Piute Mine, Nevada.
Mined for tungsten.
Metamorphic Processes
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.
Sedimentary Processes
4) Sedimentary Concentration Mechanisms:
Clastic processes involve transport and deposition:
Sand and gravel (big $$) from old river channels,
glacial deposits, deltas
 Placer deposits of weathering-resistant and heavy
minerals (Au, Ag, diamond, garnet)

Gold nugget, California (2 cm)
Placer diamonds, Namibia (3 cm across)
California’s gold rush of
the 1848-1880:
Numbers are thousands of
ft2 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 ft2 in a
month
Miners at the Volcano
camp sometimes found
$370 worth of gold in a
single panful
Sedimentary Processes
4) Sedimentary Concentration Mechanisms:
Precipitates:
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
 Fresh-water precipitates are rarely economic

Figure 14-8: Marine evaporite deposits of the USA
Sedimentary Processes
4) Sedimentary Concentration Mechanisms:
Biological deposits:
Phosphate = fish bones and teeth, guano
 fertilizers
 Diatomaceous earth & many limestones

Weathering:
Bauxite = Al in zone of leaching in laterites (highly
leached tropical soils)
 Supergene enrichment of Cu

Mineral Resources
The time-frame of resources is important

Non-renewable resources are created on our time-scale
(won’t add much in next 10 Ma)

No sustained yield like crops, timber…
“Resources” = useful materials that can be extracted and
made into a useful commodity at a profit (either now or
in the reasonable future)
 “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

Figure 14.2: USGS
classification of
mineral resources
Identified
Economic
Reserves
Marginally
Economic
Marginal
Reserves
Undiscovered
In known
districts
Hypothetical
Resources
In undiscovered
districts or forms
Speculative
Resources
Subeconomic
Subeconomic Resources
Increasing degree of geological assurance
Mineral Resources
Consumption, Resources, and Availability
The typical evolution curve for a non-renewable resource
production rate
Consumption, Resources, and Availability
(1)
(2)
time
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
Consumption, Resources, and Availability
When do we do when we run out??
17
Average Crustal Rocks
16
15
High-U Granites
14
Black Shales
13
Log Rock Tonnage
12
Phosphoria Formation
11
10
Original Rich U finds
9
8
7
6
5
4
Grade vs. Quantity of Uranium
in the upper km of crust in the USA
3
Probable
Richest
Ore
2
1
0
0.1
1
10
0.01
100
0.1
1,000
1
10
100 %
10,000
ppm
Uranium Concentration
Availability and Demand of 32 “Critical” Non-fuel Mineral Commodities (1978)
Foreign sources
In USA
Reserves/Cumulative
Commodity
(% Imported)
Demand 1978-2000
% Produced Demand (tons)
Chromium
Manganese
Cobalt
Titanium
Columbium
Tin
Platinum Group
Antimony
Nickel
Aluminum
Asbestos
Fluorine
Zinc
Silver
Gold
Tungsten
Potash
Cadmium
US
World
< 0.1
9.5
USSR 41, South Africa 15
0
500,000
0
1,300,000
0
4.6
Gabon 29, Brazil 18
0
8,600
0
1.2
Zaire 62
0
750
0
1.2
Malaysia, Thailand, Canada
0
2,600
0
> 10
Brazil 57, Canada 14
0
50,000
0.1
1.5
Malaysia 50, Bolivia 18
0
3
South Africa 74, USSR 8
0.2
65
6
6
16,000
170,000
0.1
< 0.1
1.8
2.2
South Africa 38, Bolivia 16
Canada 56, New Caledonia 9
8
5,300,000
< 0.1
5.8
Jamaica 28, Austalia 23
16
580,000
0.2
0.5
Canada 94, South Africa 4
18
550,000
0.1
0.4
Mexico 59, South Africa 17
31
1,000,000
0.6
0.8
Canada 42, Mexico 6
33
3,500
0.4
0.5
Canada 46, Mexico 24
0.6
1.1
Canada 14, USSR 33
38
8,700
0.4
1.4
Canada 25, Bolivia 19
39
5,900,000
0.9
> 10
Canada 95, Israel 3
39
5,100
1.0
1.1
Mexico 59, South Africa 17
Availability and Demand of 32 “Critical” Non-fuel Mineral Commodities (1978)
Foreign sources
In USA
Reserves/Cumulative
Commodity
(% Imported)
Demand 1978-2000
% Produced Demand (tons)
Selenium
Berylluim
Mercury
Titanium
Iron
Barite
Lead
Vanadium
Copper
Sulfur
Rare Earths
Lithium
Phosphate
Molybdenum
US
World
42
43
500
63
1.9
3.1
3.5
> 10
Canada 46, Mexico 24
Brazil 56, Argentina 21
43
48
2,000
460,000
0.3
1.4
0.9
4.1
Algeria 31, Spain 31
Australia 48, Canada 22
58
87,000,000
1.5
5.1
Canada 39, Japan 17
60
2,500,000
1.3
1.3
Peru 28, Ireland 22
76
700,000
1.0
1.1
Canada 27, Mexico 26
76
6,300
0.2
7.8
South Africa 54, Chile 26
77
1,700,000
1.5
1.6
Canada 24, Chile 24
90
13,000,000
0.5
0.9
Canada 59, Mexico 39
90
18,000
9.3
8.0
Australia 43, Malaysia 32
144
3,900
2.8
-
180
34,000,000
3.6
6.5
200
30,000
2.9
2.1
• Only 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)
• Reserves of > ½ used up by 2020
Consumption, Resources, and Availability
When do we do when we run out??
Search harder, dig deeper, find more (and pay more)
 Import (foreign debt and dependence)
 Find a substitute (synthetics replace metals, cotton…)
 Conserve (use less or be more efficient)
 Recycle (OK for metals, glass, but has limits)
 Steal somebody else’s (war)
 Do without

Environmental Impacts of
Mineral Consumption, Mining,
and Processing

Processing of a typical
metal sulfide ore (copper,
lead, zinc, molybdenum...)
Environmental Impacts of Mineral
Consumption, Mining, and Processing

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
Environmental Impacts of Mineral
Consumption, Mining, and Processing

Surface mining
Mining ruptures the weathered
barrier and exposes the interior
to the environment
Environmental Impacts of Mineral
Consumption, Mining, and Processing

Sub-surface
mining  less
impact on site,
but still exposes
ore to water
Environmental Impacts of Mineral
Consumption, Mining, and Processing

Materials are relatively toxic
when exposed at the surface



Water  weathering, solution
 toxic metals + sulfuric acid
into surface & groundwater
environment
Est. 550,000 abandoned mines
in USA contaminate 19,000
rivers and streams
Collapse of old excavations
poses a serious threat as well
Acidic and Fe-rich water from an abandoned subsurface tunnel pours into Beartrap Creek, which
flows into the prime trout waters of the Blackfoot
River, Montana
Mine tailings, Bingham Canyon open pit Cu mine, Utah
White streaks of zinc
leached from a tailings
pile and redeposited
downslope. Colorado.
Mining Pollution
Smelting releases SO2 to the
atmosphere creating acid rain
Ducktown TN
Sudbury, Ontario
Mining Pollution
Strip Miningremove shallow
surface cover and
deposit such as coal,
Fe, Mn, or phosphate
that extends over a
broad area
Mining Pollution
Adverse effects include:

Removal of soil

Exposing ore

Polluting water

Disrupting drainages

Asthetics
Strip phosphate mine. Florida
Contaminated water from a strip coal mine, Illinois
Dredging- excavation, sifting, and redepositing
of sediment as remove placer minerals
Dredging rarely exposes fresh toxic ore, but
severely disrupts a river valley or bed
Pad must be
lined
Note dam
Keeping cyanide from entering the groundwater
system is of critical importance
Heap-leach pad extracting gold, Winnemucca, Nevada
Minimizing the impact of mineral development

Environmental regulation
Most degradation is due to past mining practices
that are now illegal in 1st world
 US smelters have stringent air quality standards
 Water pollution containment and land reclamation
plans

Mining Reclamation
1977 Surface Mining Control and Reclamation Act
(SMCRA)
 Created the Office of Surface Mining and several
branches in mining states
 Establishes standards and funds federal and state
agencies
 Coordinated federal and state efforts to regulate
pollution, subsidence, and restoration of affected
lands for coal mining


Non-coal still left to individual states
Once states set up SMCRA standards they may apply
them to non-coal and use SMCRA funds as they see fit
Mining Reclamation




Clean Air Act and Clean Water Act too, because
these are public commons (note Tragedy of…)
NEPA applies to activities on federal lands only
USFS administers mining reclamation on National
Forests
Some abandoned mines are bad enough to qualify
as Superfund sites
Mining Reclamation
Steps in Surface Mine Reclamation

If possible: Before begin, peel back and store soil
Mining Reclamation
Steps in Surface Mine Reclamation

Drainage control and diversion at disturbed area
Steps in Surface Mine Reclamation

Add or replace topsoil and immediate seeding with
rapidly growing species, such as rye grass
Steps in Surface Mine Reclamation

After initial grass dies back, permanent species
take over. Can use as habitat, grazing, etc.
Dredge Area Reclamation
Ducktown Tennessee: Superfund Site
Ducktown Tennessee: Superfund Site
Ducktown Tennessee: Superfund Site
Ducktown Tennessee: Superfund Site
Minimizing the impact of mineral development

Biotechnology
Use microbes (some genetically engineered) to
oxidize, absorb, or leach pollutants
 Bioassisted leaching uses critters to liberate metals
for chemical leaching
 Also use microbes to neutralize acid mine drainage

Recycling of Mineral Resources
Recycling of Mineral Resources
Scrap metal
Recycling of Mineral Resources
Urban Ore
 Landfills may contain useful materials
 Palo Alto: ash from incineration of sewage sludge
contained 30ppm Au, 660 ppm Ag, 8000 ppm Cu,
and 6.6% P
 Not all cities are like this, of course, but we may find
inexpensive ways to process low grade ores, since
processing the sewage anyway