An Overview of Cu-Ni Deposits in An Overview of Cu-Ni Deposits in Minnesota: A Geological PerspectiveMinnesota: A Geological Perspective

Jim MillerDepartment of Geological Sciences

Precambrian Research CenterUniversity of Minnesota Duluth

LAKE SUPERIOR BINATIONAL FORUMMarch 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 A Looming Stewardship Stewardship Question for Question for

Minnesotans:Minnesotans:

When should we develop

this immense copper-nickel-precious metal

mineral resource?

_______________

THE THE MIDCONTINENMIDCONTINENT RIFTT RIFT_______________An attempt at continental rifting 1.1 billion years ago

A. Rift Magmatism

Gabbro

MantlePlume

BasaltFlows

CrustMantle

B. Sediment Infilling Sandstone

C. Compression

1,109-1,086 Ma

1,090-900 Ma

1,000-900 Ma

Tectonic and Magmatic Tectonic and Magmatic Evolution of the Evolution of the

Midcontinent RiftMidcontinent Rift

Midcontinent Rift Midcontinent Rift Exposure in the Exposure in the

Lake Superior Lake Superior RegionRegion

Duluth Complex

Partridge River Intrusion

South Kawishiwi Intrusion

Sequential Sequential Emplacement Emplacement of Duluth of Duluth Complex Complex IntrusionsIntrusions

Sulfur Contamination creating the Cu-Ni-PGE Sulfur Contamination creating the Cu-Ni-PGE Sulfide Deposits of the Duluth ComplexSulfide Deposits of the Duluth Complex

SSCu Ni Co Pd + Pt + Au

SS

$/t

on

Cu Prices 1948-2006

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 ActivityPolymet – NorthmetTeck American – MesabaTwin Metals MN – Nokomis, Maturi, Dunka Pit, Birch Lake, Spruce Rd Encampment– South Filson Cr.

The Current SituationThe Current Situation

Mineralogy of Magmatic Mineralogy of Magmatic Cu-Ni Sulfide DepositsCu-Ni Sulfide Deposits

Sulfide MineralsPyrrohotite – FeS1-x

Chalcopyrite - CuFeS2

Pentlandite - (Fe,Ni)9S8

Bornite - Cu5FeS4

Chalcocite - Cu2SCobaltite – CoAsSPt Group Minerals – Pt, Pd, Au, Bi, Te, As, ...

Silicate/Oxide MineralsOlivine - (Mg,Fe)2SiO4

Plagioclase – (Ca,Na)(Al,Si)4O8

Augite – Ca(Mg,Fe)Si2O6

Titano-magnetite – (Fe,Ti)3O4

The Environmental ChallengePreventing 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

ChalcopyriteCuFeS2 Bornite

Cu5FeS4

CobaltiteCoAsS

SphaleriteZnS

GalenaPbS

ChalcociteCu2S

MolybdeniteMoS2

Pentlandite(Fe,Ni)9S8

CinnabarHgS

THEN

NOW

Sudbury, Ont.

Hydrometallurgy

Roasting/Smelting Monchegorsk, Russia

Separating Metal Separating Metal from Sulfurfrom 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 Summaries35% from Recycled Cu

Cu in a Standard Car with Combustion Engine

43-55 lbs

Cu in a Prius80 lbs

COPPERCOPPER An Important Metal in a Green Economy

NW Mining Association, 2009

PGE – Platinum Group ElementsPGE – Platinum Group ElementsPt – Platinum, Pd – Palladium, Os – Osmium, Ru – Ruthenium, Rh – Rhodium, Ir - Iridium

Bushveld ComplexBushveld ComplexSouth AfricaSouth Africa

Supplying the 70% of the World’s Platinum

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

Palladium: Palladium: ““The Environmental Metal”The Environmental Metal”Pd

Uses

Stillwater Mine (Montana)Stillwater Mine (Montana)Only Precious Metals Mine in the U.S.

(owned by Noril’sk Nickel)

Sulfide Smelters in RussiaIn 1998, responsible for ~half of SO2

in the northern hemisphere

Noril’sk, RussiaCu-Ni-PGE Deposits

Supplies 45-60% of the World’s Palladium

World Class Ores of the Duluth ComplexWorld 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 World Scale of the Maturi DepositDeposit

Nokomis

From Peterson, 2010 and DM press release 12/2012

Maturi

Maturi

Maturi

The Largest UNDEVELOPED Cu-Ni Deposit on The Largest UNDEVELOPED Cu-Ni Deposit on EarthEarth

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?Stewardship question - If not now, when?

CONCLUSION: CONCLUSION: The base and precious metal deposits of the Duluth Complex are a World Class Resource that will be mined …. SOMEDAY