ERTH 2001: Resources 2

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ERTH 2001 Resources 2
Examples 1. Base Metals (copper) 2. Evaporite
Deposits (salt, gypsim)
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ERTH 2001 Resources
Geochemically Scarce Metals (CVS Ch. 8)   -
present in trace amounts (lt 0.1 by weight)  -
form relatively few mineral species these tend
to be rare e.g., galena (PbS) - more common as
trace components substituting for more abundant
elements in other minerals e.g.,
Pb substitutes for K in K-feldspar (KAlSi3O8) at
ppm level - because they are relatively scarce,
they are also quite valuable     Classification
by use   ferro-alloy metals (Cr, V, Ni, Mo,
Co, W) base metals (Cu, Pb, Zn, Sn, Hg,
Cd) precious metals (Au, Ag, Pt/PGE) special
metals (Nb, Ta, As, Sb, Bi, Ge, Ga, In, Be, REE)
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ERTH 2001 Resources
Base Metals (CVS p. 297-312) Cu, Pb, Zn, Sn, Hg,
Cd   - relatively common, relatively low value -
inferior with respect to some properties
(e.g., corrosion, strength, hardness) -
numerous other extremely important and versatile
uses - first metals to be mined, smelted by
people (Cu gt 6000 BP)     Cu-Pb-Zn - most
common of the base metals - typically
occur together in volcanogenic massive sulphide
deposits (VMS deposits)   minerals -
chalcopyrite (CuFeS2), galena (PbS), sphalerite
((Zn,Fe)S) - among the most common
sulphide minerals - commonly occur
together along with pyrite (FeS2)
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ERTH 2001 Resources
Copper - Cu (CVS Ch. 8, p. 298-307) - one
of the most important metals to our society
- used mainly in the electrical industry (and
related uses in transportation and construction)
- conductive, ductile, malleable, but
corrodes - relatively abundant in both
continental and oceanic crust (gt .005) -
economic deposits of Cu minerals are relatively
common ore minerals native copper (Cu),
chalcopyrite (CuFeS2), digenite (Cu9S5),
chalcocite (Cu2S), bornite (Cu5FeS4), enargite
(Cu3AsS4), covellite (CuS), tetrahedrite
(Cu12Sb4S13), cuprite (Cu2O), malachite
(Cu2CO3(OH)2), azurite (Cu(CO3)2(OH)2)
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ERTH 2001 Resources
Copper - Cu (CVS Ch. 8, p. 298-307) - one
of the most important metals to our society
- used mainly in the electrical industry (and
related uses in transportation and construction)
- conductive, ductile, malleable, but
corrodes - relatively abundant in both
continental and oceanic crust (gt .005) -
economic deposits of Cu minerals are relatively
common
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ERTH 2001 Resources
Copper deposits - magmatic segregation -
large mafic / ultramafic plutons typically
associated with Ni (e.g., at Sudbury) -
hydrothermal deposits - solution,
transport, re-precipitation of Cu by hot aqueous
fluids - original source of Cu generally
mafic to granitoid igneous rocks - Cu
deposited in veins or stockworks, or
disseminated - sediment-hosted stratiform
deposits Types of hydrothermal Cu deposits -
veins - porphyry copper deposits - skarns -
volcanogenic massive sulphide deposits
Copper - Cu (CVS Ch. 8, p. 298-307)
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ERTH 2001 Resources
Porphyry copper deposits - account for over
half world production - huge volume, low
grade - associated with calc-alkaline
granitoid plutons in magmatic arc settings -
high level plutons (porphyries) set up
near-surface hydrothermal circulation
systems that concentrate Cu, Mo, and some other
metals - supergene enrichment may further
concentrate Cu - most important deposits in
Cordillera and Andes
world porphyry copper deposits
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ERTH 2001 Resources
Porphyry copper deposits - account for over
half world production - huge volume, low
grade - associated with calc-alkaline
granitoid plutons in magmatic arc settings -
high level plutons (porphyries) set up
near-surface hydrothermal circulation
systems that concentrate Cu, Mo, and some other
metals - supergene enrichment may further
concentrate Cu - most important deposits in
Cordillera and Andes
world porphyry copper deposits
Chile - largest producer Chuquicamata -
largest deposit (Gt)
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ERTH 2001 Resources
Porphyry copper deposits - account for over
half world production - huge volume, low
grade - associated with calc-alkaline
granitoid plutons in magmatic arc settings -
high level plutons (porphyries) set up
near-surface hydrothermal circulation
systems that concentrate Cu, Mo, and some other
metals - supergene enrichment may further
concentrate Cu - most important deposits in
Cordillera and Andes
schematic cross-section
map view
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ERTH 2001 Resources
Porphyry copper deposits - account for over
half world production - huge volume, low
grade - associated with calc-alkaline
granitoid plutons in magmatic arc settings -
high level plutons (porphyries) set up
near-surface hydrothermal circulation
systems that concentrate Cu, Mo, and some other
metals - supergene enrichment may further
concentrate Cu - most important deposits in
Cordillera and Andes
map view
open pit mine, Arizona
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ERTH 2001 Resources
Porphyry copper deposits - account for over
half world production - huge volume, low
grade - associated with calc-alkaline
granitoid plutons in magmatic arc settings -
high level plutons (porphyries) set up
near-surface hydrothermal circulation
systems that concentrate Cu, Mo, and some other
metals - supergene enrichment may further
concentrate Cu - most important deposits in
Cordillera and Andes
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ERTH 2001 Resources
Bisbee, Arizona underground and open pit mining
Cu-Ag skarn and associated porphyry copper
deposit (mining stopped in 1975)
skarn
porphyry Cu
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ERTH 2001 Resources
Bisbee, Arizona Cu mined from skarn and porphyry
gossan
pyrite quartz
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ERTH 2001 Resources
Bisbee, Arizona Cu mined from skarn and porphyry
OM-23
native Cu
cuprite Cu2O
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ERTH 2001 Resources
 Volcanogenic massive sulphide (VMS) deposits
- most widespread type of deposit Cu-Pb-Zn
sulphides pyrite - small volume, high
grade (relative to porphyry coppers) -
host rocks are submarine volcanic rocks and
volcanogenic sediments - hydrothermal
circulation at submarine volcanic centres
(mid-ocean ridges, island
arcs) black smokers
hydrothermal circulation at mid-ocean ridges
black smoker
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ERTH 2001 Resources
Copper prices (/tonne)
2005-06 rapid rise from normally low
prices driven by increased demand from China,
India
this year (2007)
this month
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ERTH 2001 Resources
Evaporite Deposits (CVS ch. 9, p. 350-352)
sedimentary deposits formed by chemical
precipitation of minerals from saline water -
require shallow sea water (hot) arid climate -
progressive evaporation of sea water (ca. 3.4
dissolved salts) precipitation of
various salts (sequence and volume related
to concentration in brine and Ksp)
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ERTH 2001 Resources
Evaporite Deposits (CVS ch. 9, p. 350-352)
sedimentary deposits formed by chemical
precipitation of minerals from saline water -
progressive evaporation of sea water (ca. 3.4
dissolved salts) precipitation of
various salts (sequence and volume related
to concentration in brine and Ksp) - for
normal seawater, predicted sequence is calcite
gypsum halite polyhalite K-Mg
salts - relative volume of dissolved species
(NaCl equiv. 78) means that halite should
form the thickest layers in evaporite deposits
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ERTH 2001 Resources
Evaporite Deposits
predicted sequence of preciptation CaCO3
CaMg(CO3)2 -gt CaSO4.2H20 CaSO4 -gt NaCl -gt
sylvite (KCl) polyhalite (K-Mg salts)
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ERTH 2001 Resources
Evaporite Deposits (CVS ch. 9, p. 350-352)
sedimentary deposits formed by chemical
precipitation of minerals from saline water -
for normal seawater, predicted sequence
is calcite gypsum halite
polyhalite K-Mg salts - relative volume of
dissolved species (NaCl equiv. 78) means
that halite should form the thickest layers in
evaporite deposits However, observations of
natural evaporites show gypsum halite gtgt
than K-Mg salts gypsum halite gtgt than
predicted from simple closed-system
evaporation   - suggests evaporation of partially
isolated basins that received periodic influxes
of sea water 
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ERTH 2001 Resources
Evaporite Deposits
observations of natural evaporites show gypsum
halite gtgt than predicted from simple
closed-system evaporation   - suggests
evaporation of partially isolated basins that
received periodic influxes of sea water  (A,
C) - can also form in continental settings by
evaporation of groundwater seeps (B)
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ERTH 2001 Resources
Evaporite Deposits
Great Salt Lake, USA
Death Valley, USA
Persian Gulf - modern marine evaporites
nitrate, Atacama desert, Chile
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ERTH 2001 Resources
Dead Sea, Jordan
Evaporite Deposits
salt pans - modern salt
salt cliffs - ancient salt
effect of salinity on buoyancy
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ERTH 2001 Resources
main sources of some important resources e.g.
K (fertilizer) S, NaCl
(industry) gypsum (construction)
Evaporite Deposits
Portugual
production by underground mining
Pugwash NS
production by surface evaporation
Ontario
Great Salt Lake
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ERTH 2001 Resources
Evaporite Deposits POTASSIUM (CVS p. 345-348)
- 8th most abundant element essential
constituent of many common minerals - original
potash was produced from wood ashes name still
used for K-rich deposits and for K2O - K in
fertilizer comes from evaporite deposits sylvite
(KCl) carnellite (KCl.MgCl2.6H2O) langbeinite
(2MgSO4.K2SO4), kainite (KCl.MgSO4.3H2O) - these
minerals are all relatively soluble so that
special conditions are required for large
concentrations to be preserved - major potash
deposits in Canada (Williston Basin of
Saskatchewan), US, Russia associated with
extensive shallow inland seas and marine basins
that underwent periodic evaporation -
relatively small deposit in Carboniferous
evaporites near Sussex, NB mined until
1997 mine closed due to flooding problems, will
reopen
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ERTH 2001 Resources
Evaporite Deposits POTASSIUM (CVS p. 345-348)
Potash Corp world's largest producer
Williston Basin world's largest deposits
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ERTH 2001 Resources
Evaporite Deposits SALT (halite, NaCl) (CVS p.
349-355)
- familiar household material - major use is
industrial -- Na, Cl, caustic soda (NaOH),
hydrochloric acid (HCl), etc.   OCCURRENCE -
seawater - salt lakes - formation brines
- evaporite deposits - salt domes 
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ERTH 2001 Resources
Evaporite Deposits
salt domes - dome-shaped concentrations of salt
formed by upward migration of buried salt
through overlying strata (diapirs)
salt domes, northern Germany
salt dome, Louisiana
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ERTH 2001 Resources
Evaporite Deposits
salt domes - dome-shaped concentrations of salt
formed by upward migration of buried salt
through overlying strata (diapirs)
emergent salt dome
salt domes and folds, Zagros Mountains, Iran
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ERTH 2001 Resources
Evaporite Deposits
Formation of Salt Domes two important
factors a) density of halite - 2.16 density of
most sedimentary rocks ca. 2.5 (?NaCl 2.16
?quartz 2.65 ?feldspar 2.5-2.6)   b) halite
is also very weak and flows easily at low T and
P flows easily under differential pressure
(e.g., sediment loading)   buried salt is
unstable owing to the combination of low density
and low viscosity and will flow laterally and
vertically in response to pressure gradients
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ERTH 2001 Resources
Evaporite Deposits
Formation of Salt Domes two important
factors   buried salt is unstable owing
to the combination of low density and low
viscosity and will flow laterally and vertically
in response to pressure gradients
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ERTH 2001 Resources
Evaporite Deposits
Formation of Salt Domes two important
factors   buried salt is unstable owing
to the combination of low density and low
viscosity and will flow laterally and vertically
in response to pressure gradients
pressure gradient caused by extension
compression
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ERTH 2001 Resources
Evaporite Deposits
- salt domes range from 100 - gt2000 m diameter
rise up to 12 km from source layer
through overlying sediments - much of the world's
mined salt comes from salt domes (e.g.,
Pugwash, Nappan, in NS)  - also form excellent
traps for petroleum (e.g., Gulf Coast, USA
Scotian slope - deepwater "salt province")  -
also exploited for S in cap rock (Gulf Coast,
USA) biogenic reduction of SO4 in gypsum
associated with salt
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ERTH 2001 Resources
Evaporite Deposits
Gypsum (CaSO42H2O) Anhydrite (CaSO4) (CVS,
Ch.10, p. 374-376 also Ch. 9, p. 348-350)  -
widely used in construction industry
(plaster, wallboard) - gypsum can be processed
easily (calcining ? plaster of Paris) -
anhydrite requires more processing
(hydration) - Nova Scotia is a major producer
(Windsor Group) http//www.gov.ns.ca/natr/meb
/ic/ic16.htm - NS gypsum processed entirely in US
gypsum crystals in Naica deposit, Mexico
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ERTH 2001 Resources
Evaporite Deposits
gypsum is weak and deforms easily
gypsum is soluble and contributes to karst
topography
gypsum cliffs, Bras d'Or, Cape Breton
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ERTH 2001 Resources
Evaporite Deposits
mastodon model, Hwy 102 Stewiacke
mastodon teeth, East Milford quarry
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ERTH 2001 Resources
Evaporite Deposits
gypsum mining in NS -
...and now...
then.....
early gypsum mining in Hants Co. (ca. 1895)
East Milford - largest gypsum mine in world
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ERTH 2001 Resources
Evaporite Deposits
production of gypsum and other evaporite
materials from Windsor Group in NS
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ERTH 2001 Resources
Evaporite Deposits
economy of scale.... NS gypsum is shipped to USA
for processing
gypsum ready for shipping, Hantsport, NS
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ERTH 2001 Resources
Evaporite Deposits
Nova Scotia is single largest producer of gypsum
in North America gt 80 Canadian production
anhydrite less important - requires more
processing
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ERTH 2001 Resources
Evaporite Deposits
NS production mainly from Hants Co and Victoria
Co (Cape Breton)
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ERTH 2001 Resources
Evaporite Deposits
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ERTH 2001 Resources
Evaporite Deposits