Copper, Nickel, and Precious-Metal
Deposits in Northeastern Minnesota:
A Geological Perspective
Jim Miller
Department of Earth and Environmental Sciences
Precambrian Research Center
University of Minnesota Duluth
Headliners
March 5, 2015
University of Minnesota
Terminology and Definitions
Natural Resources – materials, and energy that occur
naturally within the Earth’s spheres. Many are essential for
our survival, while others are used for satisfying our wants.
Biological Resources
• renewable
• recycleable
• reuseable
Wind and Solar
• unlimited
Stuff
Water Resources
• unlimited
• recycleable
• reuseable
Mineral Resources
• non-renewable
• recycleable
• reuseable
“Sustainable Development is development that meets the needs of the
present without compromising the ability of future generations to meet
their own needs” (1984, United Nations Commission)
Stewardship - “administration, management, control, including
responsible use of resources” (Oxford English Dictionary Online)
A Looming
Stewardship
Question for
Minnesotans:
How should
we administer
manage,
control, and
responsibly
use this
immense
copper-nickelprecious metal
mineral
resource?
Outline
Why are these deposits here?
History of exploration
Why “sulfide” mining?
What are the uses of Cu, Ni, and Pd
Where else in the world are these ore
deposit types mined?
• How do the Duluth Complex ores
compare?
•
•
•
•
•
Minnesota Two Billion Years Ago
Deposition of Iron Formation
St. Cloud
Babbitt
Duluth
FeS2
Babbitt
_______________
THE
MIDCONTINENT
RIFT
_______________
An attempt at
continental rifting
1.1 billion years ago
A. Rift Magmatism
Basalt
Flows
Gabbro
Crust
Mantle
Tectonic and Magmatic
Evolution of the
Midcontinent Rift
1,109-1,086 Ma
Mantle
Plume
B. Sediment Infilling
Sandstone
1,090-900 Ma
C. Compression
1,000-900 Ma
Midcontinent Rift
Exposure in the
Lake Superior
Region
Duluth
Complex
South
Kawishiwi
Intrusion
Partridge
River
Intrusion
Sulfur Contamination creating the Cu-Ni-PGE
Sulfide Deposits of the Duluth Complex
S
Cu
S
Ni
Co
Pd + Pt + Au
From MN Minerals Coordinating Committee, 2014
Drill Footage
History of Exploration of
Duluth Complex Cu-Ni Deposits
From M. Severson, 2007
1967
1969
INCO
sinks shaft US Steel drills
Dunka Pit
at Maturi
TMM/DM 2011-13
420 DDH ~1,300,000’
1998-present
1966
1974-78 Cu-Ni Regional Study Current surge in
State land opens
exploration drilling
1974-82
for mineral leasing
Fleck/Polymet,
State land closed to
Cominco/Teck,
new mineral leasing
Wallbridge/Duluth
1948
1976
1978
Metals/Twin Metals
Cu-Ni sulfide
Amax sinks BWCAW
discovered at
shaft at
Established
2006
Spruce Rd
Babbitt
Cu tops
1958
1988
1999
$3/lb
Bear Creek
Lehmann drills
LTV
drills Babbitt
Birch Lake
shuts down
1954
1985
INCO drills
PGE discovered
Maturi
by U of MN
1940’s
1950’s
1960’s
1970’s
1980’s
1990’s
2000’s
The Current Situation
Current Exploration Activity
Polymet – Northmet
Teck American – Mesaba
Twin Metals MN –Maturi, Dunka
Pit, Birch Lake, Spruce Rd
Encampment– South Filson Cr.,
Serpentine
Mineralogy of Magmatic
Cu-Ni Sulfide Deposits
Sulfide Minerals
Pyrrhotite – FeS1-x
Chalcopyrite - CuFeS2
Pentlandite - (Fe,Ni)9S8
Talnakhite - Cu9(Fe,Ni)8S16
Bornite - Cu5FeS4
Cubanite - CuFe2S3
Chalcocite - Cu2S
Cobaltite – CoAsS
Pt Group Minerals – Pt, Pd, Au, Bi, Te, As, ...
Silicate/Oxide Minerals
Olivine - (Mg,Fe)2SiO4
Plagioclase – (Ca,Na)(Al,Si)4O8
Augite – Ca(Mg,Fe)Si2O6
Titano-magnetite – (Fe,Ti)3O4
The Environmental Challenge
Preventing Acid Rock Drainage (ARD) and
Metals Release
2FeS2(s) + 7O2(g) + 2H2O(l) → 2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)
The GARD
Guide
___________
International
Network for Acid
Prevention
746 pages
Why Sulfide Mining?
Most of the world’s metals comes from sulfide minerals
Chalcopyrite
CuFeS2
Bornite
Cu5FeS4
Chalcocite
Cu2S
Pentlandite
(Fe,Ni)9S8
Cinnabar
HgS
Sphalerite
ZnS
Molybdenite
MoS2
Galena
PbS
Cobaltite
CoAsS
Sulfide Ore
Processing
Separating Metal
from Sulfur
Traditional
Roasting/Smelting
New Tech
Hydrometallurgy
Sudbury, Ontario
Monchegorsk, Russia
Voisey’s Bay Ni-Cu-PGE Deposit, Labrador
Voisey’s Bay Mine and Mill
Long Harbour Hydromet Plant
1996 - Discovery
2005 - Open-pit mining
begun
2014 –ore processing
begun at Long
Harbour (NFLD)
hydromet plant
2019 – Underground
mining to begin
2035 – Mine to close
United States –
The #1 consumer of
most of the world’s
mineral resources
Metal
% Mined by US
vs. Total Mining
% Imported for
US consumption
Copper
7%
(Chile (41%), Canada (33%))
30%
Nickel
0%
43%
(Canada (44%), Russia, Australia, Norway)
Cobalt
0%
81%
(Norway, Russia, China, Canada)
Palladium 5.9%
58%
(Russia (44%), South Africa (37%))
Global Cu
Mining
2014 Rest of the
United States AZ,
World
13%
7%
Canada
4%
Zambia & Congo
10%
Australia &
Indonesia
7%
China
9%
Russia & Poland
9%
Data from USGS Mineral Commodity Summaries
UT,NM,NV,MT
Mexico
3%
Transportatio
n
19%
(10% in 2002)
Industrial
Machinery
7%
Building
Construction
43%
Chile
31%
Global Production
= 18.7 million tons
Peru
7%
Cu Markets
2014
Consumer
Products
12%
32% from Recycled Cu
Electrical/
Electronics
19%
COPPER
An Important Metal in a Green Economy
NW Mining Association, 2009
Cu in a Standard Car with
Combustion Engine
43-55 lbs
Cu in a Prius - 80 lbs
Cu in a Volt - 150 lbs
PGE – Platinum Group Elements
Pt – Platinum, Pd – Palladium, Os – Osmium, Ru – Ruthenium, Rh – Rhodium, Ir - Iridium
Bushveld Complex
South Africa
Supplying the 70% of the World’s Platinum
Merensky Reef, Amplats Mine, Rustenburg, SA
Merensky Reef, Eastern Bushveld Complex
Palladium:
Pd
Uses
“The Environmental Metal”
Stillwater Mine (Montana)
Only Precious Metals Mine in the U.S.
(2005-2013, owned by Noril’sk Nickel)
Noril’sk, Russia
Cu-Ni-PGE Deposits
Supplies 45-60% of the World’s Palladium
Sulfide Smelters in Russia
In 1998, responsible for ~half of SO2
in the northern hemisphere
World Class Ores of the Duluth Complex
Compared to other Magmatic Sulfide Deposits, the Duluth Complex is:
#1
or 2 in contained Copper
#4 in contained PGE
#3 in contained Nickel
Only the Bushveld, Great
Dyke, and Noril’sk contain
more PGE
From Peterson, 2010
World Scale of the Maturi
Deposit
Nokomis
Maturi
Maturi
Maturi
From Peterson, 2010 and
DM press release 12/2012
The Largest UNDEVELOPED Cu-Ni Deposit on Earth
Duluth deposits are perceived as low grade. But
compared to the source of most of the world’s copper Porphyry Copper Deposits...
…the Duluth Complex
ores are HIGHER
GRADE with MORE
CONTAINED
METAL than nearly
all porphyry systems.
The largest copper
ore deposits in the
USA are on this
diagram, and the
Duluth Complex ores
are much larger then
all of them.
From Peterson, 2010
CONCLUSION:
The base and
precious metal
deposits of the
Duluth Complex
are a World
Class Mineral
Resource
How should it
be stewarded?
If Not Now, When?
Mesaba
Northmet
All Mining Ends