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-nickel- precious metal mineral resource?

_______________ THE MIDCONTINENT RIFT _______________ An attempt at continental rifting 1.1 billion years ago

1,109-1,086 Ma 1, Ma 1, Ma Tectonic and Magmatic Evolution of the Midcontinent Rift

Midcontinent Rift Exposure in the Lake Superior Region Duluth Complex

Partridge River Intrusion South Kawishiwi Intrusion

Sequential Emplacement of Duluth Complex Intrusions

Sulfur Contamination creating the Cu-Ni-PGE Sulfide Deposits of the Duluth Complex S Cu Ni Co Pd + Pt + Au S

$/ton Cu Prices Cu-Ni Regional Study PGE discovered LTV shuts down Cu-Ni sulfide discovered at Spruce Rd INCO drills Maturi Bear Creek drills Babbitt State land opens for mineral leasing Active exploration drilling Polymet, Teck, Franconia, Wallbridge (Duluth Metals) State land closed to new mineral leasing Current $ - 7,060

Current Exploration Activity Polymet – Northmet Teck American – Mesaba Twin Metals MN – Nokomis, Maturi, Dunka Pit, Birch Lake, Spruce Rd Encampment– South Filson Cr. The Current Situation

Mineralogy of Magmatic Cu-Ni Sulfide Deposits Sulfide Minerals Pyrrohotite – FeS 1-x Chalcopyrite - CuFeS 2 Pentlandite - (Fe,Ni) 9 S 8 Bornite - Cu 5 FeS 4 Chalcocite - Cu 2 S Cobaltite – CoAsS Pt Group Minerals – Pt, Pd, Au, Bi, Te, As,... Silicate/Oxide Minerals Olivine - (Mg,Fe) 2 SiO 4 Plagioclase – (Ca,Na)(Al,Si) 4 O 8 Augite – Ca(Mg,Fe)Si 2 O 6 Titano-magnetite – (Fe,Ti) 3 O 4

The Environmental Challenge Preventing Acid Rock Drainage (ARD) 2FeS 2 (s) + 7O 2 (g) + 2H 2 O(l) → 2Fe 2+ (aq) + 4SO 4 2- (aq) + 4H + (aq)

Why Sulfide Mining? Most of the world’s metals comes from sulfide minerals Chalcopyrite CuFeS 2 Bornite Cu 5 FeS 4 Cobaltite CoAsS Sphalerite ZnS Galena PbS Chalcocite Cu 2 S Molybdenite MoS 2 Pentlandite (Fe,Ni) 9 S 8 Cinnabar HgS

THEN NOW Sudbury, Ont. Hydrometallurgy Roasting/Smelting Monchegorsk, Russia Separating Metal from Sulfur

United States – The #1 consumer of mineral resources, that produces little for itself % Mined by US % Imported for Metal vs. Total Mining US consumption Copper 6.9% 30% (Chile (41%), Canada (33%)) Nickel 0% 43% (Canada (44%), Russia, Australia, Norway) Cobalt 0% 81% (Norway, Russia, China, Canada) Palladium 5.9% 58% (Russia (44%), South Africa (37%))

Data from USGS Mineral Commodity Summaries 35% from Recycled Cu

Cu in a Standard Car with Combustion Engine lbs Cu in a Prius 80 lbsCOPPER An Important Metal in a Green Economy NW Mining Association, 2009

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, Eastern Bushveld ComplexMerensky Reef, Amplats Mine, Rustenburg, SA

Palladium: “The Environmental Metal” Pd Uses

Stillwater Mine (Montana) Only Precious Metals Mine in the U.S. (owned by Noril’sk Nickel)

Sulfide Smelters in Russia In 1998, responsible for ~half of SO 2 in the northern hemisphere Noril’sk, Russia Cu-Ni-PGE Deposits Supplies 45-60% of the World’s Palladium

World Class Ores of the Duluth Complex # 1 or 2 in contained Copper # 4 in contained PGE # 3 in contained Nickel Compared to other Magmatic Sulfide Deposits, the Duluth Complex is: Only the Bushveld, Great Dyke, and Noril’sk contain more PGE From Peterson, 2010

World Scale of the Maturi Deposit Nokomis From Peterson, 2010 and DM press release 12/2012 Maturi

The Largest UNDEVELOPED Cu-Ni Deposit on Earth From Peterson, 2010 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.

Stewardship question - If not now, when? CONCLUSION: The base and precious metal deposits of the Duluth Complex are a World Class Resource that will be mined …. SOMEDAY