An Overview of Cu-Ni Deposits in
Minnesota: A Geological Perspective
Jim Miller
Department of Geological Sciences
Precambrian Research Center
University of Minnesota Duluth
LAKE SUPERIOR BINATIONAL FORUM
March 25, 2013
Virginia, MN
Outline
• Why are these deposits here?
• History of exploration
• Why “sulfide” mining?
• What are the uses of Cu, Ni, and
Pd and where else can they be
found
• Why these ores will be mined,
someday
A Looming
Stewardship
Question for
Minnesotans:
When should
we develop
this immense
copper-nickelprecious metal
mineral
resource?
_______________
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
Sequential
Emplacement
of Duluth
Complex
Intrusions
Sulfur Contamination creating the Cu-Ni-PGE
Sulfide Deposits of the Duluth Complex
S
Cu
S
Ni
Co
Pd + Pt + Au
State land opens
for mineral leasing
Active exploration drilling
Polymet, Teck, Franconia,
Wallbridge (Duluth Metals)
Cu-Ni sulfide
discovered at
Spruce Rd
Cu-Ni Regional Study
State land closed to
new mineral leasing
Bear Creek
drills Babbitt
INCO drills
Maturi
LTV shuts down
PGE discovered
8,000
Current $ - 7,060
Cu Prices 1948-2006
7,000
$/ton
6,000
5,000
4,000
3,000
2,000
1,000
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
1966
1964
1962
1960
1958
1956
1954
1952
1950
1948
0
The Current Situation
Current Exploration Activity
Polymet – Northmet
Teck American – Mesaba
Twin Metals MN – Nokomis,
Maturi, Dunka Pit, Birch
Lake, Spruce Rd
Encampment– South Filson Cr.
Mineralogy of Magmatic
Cu-Ni Sulfide Deposits
Sulfide Minerals
Pyrrohotite – FeS1-x
Chalcopyrite - CuFeS2
Pentlandite - (Fe,Ni)9S8
Bornite - Cu5FeS4
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)
2FeS2(s) + 7O2(g) + 2H2O(l) →
2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)
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
Separating Metal
from Sulfur
THEN
Roasting/Smelting
NOW
Hydrometallurgy
Sudbury, Ont.
Monchegorsk, Russia
United States –
The #1 consumer of
mineral resources, that
produces little for itself
Metal
% Mined by US
vs. Total Mining
% Imported for
US consumption
Copper
6.9%
(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%))
2010 Domestic Cu Use
2010 Sources of Mined Cu
Chile
Peru
Building Construction
10%
12%
9%
Electrical/Electronics
49%
3%
5%
3%
16%
34%
Consumer Products
Industrial Machinery
35% from Recycled Cu
US (AZ,UT,NV,NM,MT)
Russia and Kazakhstan
Transportation
20%
China
Australia
5%
7%
7%
7%
8%
6%
Data from USGS Mineral Commodity Summaries
Indonesia
Zambia
Canada
Poland
Rest of World
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
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.
(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 Resource
that will be
mined ….
SOMEDAY
Stewardship question - If not now, when?