esas0404temp_Uranium-stu

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Unformatted text preview: Rocks,
water,
metal:

Uranium
in
the
Southwest EARTH
SCIENCE
in ARIZONA
and
the SOUTHWEST The
Triassic‐ Jurassic
Southwest 1 The
metal
Uranium A
heavy
metal;
the
heaviest
natural
element Abundance
about
2-3 ppm (0.0002-0.0003%)
in
the
continental
crust (1000x
more
than
gold) A
mixture
of
three
different
weights
of
atoms:
three
isotopes: 99.2% U-238 0.7% U-235 0.006% U-234 U
is
radioactive:
its
atoms
spontaneously
decay,
releasing
energy. Enriched
uranium
(high
U-235)
is
used
in
nuclear
power
and
weapons. Rocks,
water,
metal: Uranium 2 How
uranium
occurs
in
nature USGS Uranium
ions
in
solution
 


or
 (primarily
U4+
or
U6+) 



Ore
minerals
in
rocks
 


 


(U
+
other
metals
+
O) The
form
depends
on
the
chemistry
of
the
surrounding
environment. U
is
not
found
as
a
pure
metal. Rocks,
water,
metal: Uranium 3 More
oxidizing environment U
ions U
ions soluble in
water Acidic Yellow
or yellow‐green ore
minerals U
ions soluble in
water Basic Greyish‐black (more
reduced) ore
minerals More
reducing environment 7 Neutral From Drever (1997) Geologic
origin
of
different
types
of
U
ore
deposits (Kesler) Rocks,
water,
metal: Uranium 5 Late
Triassic
arc
volcanism
sends
ash
into
depositional
basins Arc volcanism upwind Paleogeographic
map
by
R.
Blakey,
NAU The
Triassic‐ Jurassic
Southwest 6 Continued
into
Jurassic Map
by
Professor
Ron
Blakey,
NAU
Geology Map
by
Professor
Ron
Blakey,
NAU
Geology Groundwater
gradient
in
Late
Jurassic Basin gh Hi lan ds Map
by
Professor
Ron
Blakey,
NAU
Geology Groundwater
leached
and
carried
U
down
into basin,
forming
Four
Corners
uranium
deposits Yellow
or yellow‐green ore
minerals U
ions soluble
in water Acidic U
ions soluble
in water Basic Greyish‐black (more
reduced) ore
minerals 7 Neutral Rocks,
water,
metal: Uranium 9 (Ingebritsen
&
Sanford,
1998) Origin
of
U
ore
deposits Volcanic
ash
contains small
amounts
of
U Ash
mixes with
sediments being
deposited U
ore deposits Magma Sediments accumulate and
become rock Groundwater leaches
U out
of ash‐bearing 
rock
layers U
minerals are
concentrated in
rock
where organic
matter is
present 10 Rocks,
water,
metal: Uranium U
deposits
exposed
by
Cenozoic
uplift,
folding,
erosion (Stone
et
al.,1983) U
mining Much
of
it
small
scale
in
the
Four
Corners (especially
on
Navajo
Nation) Poor
ventilation:
exposure
to
Rn,
U,
dust Drainage
problems Laborious Navajo
uranium
miners,
1960s (D.
Brugge) Note
lack
of
personal
protective
equipment:
direct
contact
with
U
ore
dusts and
solutions
(in
wet
conditions) Rocks,
water,
metal: Uranium 13 Uranium
mill,
Shiprock,
Navajo
Nation,
New
Mexico
in
the
Cold
War
period Rocks,
water,
metal: Uranium 14 Ore Leaching ore with acid Leaching Extracting U Product: U3O8 Tailings Sign
near
former Shiprock
mill
site Rocks,
water,
metal: Uranium 16 Uranium
Mill
Tailings
Remedial
Action
(UMTRA)
Program: US
Department
of
Energy Rocks,
water,
metal: Uranium 17 Uranium
Mill
Tailings
Remedial
Action
(UMTRA) Early
repository
design:
Shiprock Gravel Gravel Sand Clay Tailings Contaminant plume U, SO42-, NO3-, metals Later
repository
design:
Monticello,
Utah Rocks,
water,
metal: Uranium 19 Some
UMTRA
sites
today Mexican
Hat,
UT
 

Shiprock,
NM (both
on
Navajo
Nation
land) Rocks,
water,
metal: Uranium 20 Proposal
to
revive
U
mining
via
in‐situ
leaching From
Kirkham
(1979),
after
Wyoming
Mineral
Corporation From
Kirkham
(1979),
after
Wyoming
Mineral
Corporation Rocks,
Water,
Metal
:
Uranium Geologic
processes
that
created
the
Mesozoic
sedimentary
rocks
of
the
Colorado
Plateau (involving
interactions
of
rock
and
groundwater)
have
also
formed
deposits
of uranium
minerals
in
some
layers. Uranium
is
a
naturally‐occurring
radioactive
metal
mined
for
use
as
a
source
of
energy. Careless
mining
and
processing
of
uranium
have
released
radioactivity
and
toxic
metals into
soil,
water,
and
air,
and
seriously
impacted
public
health
in
the
Four
Corners region. Rocks,
water,
metal: Uranium 22 ...
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