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Iron Deposits
©2009, Dr. B. C. Paul
Acknowledgement is given to the USGS,
The Rise of Life
• By 4,300,000,000 years ago the water vapor from volcanic activity had condensed into oceans
• By 3,800,000,000 years ago carbon isotope ratios were showing carbon sorting associated with life forms and photosynthesis– By 3,500,000,000 years ago we can see the fossils of
our early Photosynthesis friends
• Photosynthesis means a new kid in town– Oxygen
The New Chemistry of Oxygen
The Result
Banded Iron Formations
Time-Line of BIF
0 1,000,000,000 3,000,000,000
500,000,000 2,000,000,000 4,000,000,000
First Banded Iron Formations at about 3.8 Billion Years Ago
Last around 1.8 Billion Years Ago
Banded Iron formations captured 20 times the oxygen contentOf the earths total atmosphere today.
The Disappearance of the Banded Iron Formations
• Photosynthesis eventually overwhelmed the dissolved iron load in the seas– Oxygen began to build noticeably in the
atmosphere
• Iron began to oxidize on land leading to red bed rock formations
The Last Gasps of the Banded Iron Formations
Ice Ages
Last Gasps of theBIF
The Second Side Effect of Oxygen
• Early sun only produced 80% of today’s output– Earths Heat was decaying– Greenhouse gases important to the temperature
• Especially a powerful greenhouse gas – Methane
• Free oxygen in the atmosphere would oxidize and destroy methane– Great oxygen event (getting to about 0.1% to 1% O2 in
atmosphere)– Ice age triggers– Snowball earth
• Ice sheets perhaps into the tropics with kilometer thick ice packs
• Both snowball episodes were associated with Banded Iron formation precipitation in reducing areas of the sea
Banded Iron Formations Are Large usually in precambrian shields
Sizes around 200,000,000Metric tonnes are common
Big ones can be 2.4Billion tons.
Iron Grades are High
Around lower 50% range
Magnetite
Fe3O4 S.G. 5.1 - 5.2, Average = 5.15 Hardness 5.5-6 Color Grayish black, Iron black. Fluorescence NoneMagnetic StrongIron 72.36%
Hematite
Fe2O3 Iron 69.94% S.G. 5.3 Hardness 6.5Color Reddish gray, Black, Blackish red. Fluorescence NoneMagnetic becomes magnetic after heating
Siderite
FeCO3 S.G. 3.96 Hardness 3.5Color Yellowish brown, Brown, Gray, Yellowish gray, Greenish gray. Fluorescence NoneMagnetic NoIron 48.20 %
Goethite
FeO(OH) S.G. 3.3 - 4.3, Average = 3.8 Hardness 5-5.5 Color Brown, Reddish brown, Yellowish brown, Brownish yellow, Ocher yellow.Fluorescence NoneMagnetic NoIron 62.85 %
What New Kinds of Iron Deposits Are Available?
• Volcanic intrusives into continental crust have formed iron– Some are in the 1.8 to 1.3 billion year range– Many are fairly new
• Can produced stockworks like porphyry (different texture)
• Can replace beds like in some of the Lead-Zinc deposits
Smaller than the BIF Deposits
Typical 40,000,000 metricTonnes with big ones upTo 450,000,000 tonnes.
Deposits Tend to be Rich – In the Upper 50s
Arnold Hill USNYBenson USNY
Cerro de Mercado MXCOChador-Malu IRANChahehgaz IRANChoghart IRAN
Ekstromberg SWDNEl Algarrobo CILEEl Dorado CILEEl Encino MXCOEL Romeral CILE
Grangesberg SWDNGruvberget SWDN
Guadalupe & Solis MXCOHercules MXCO
Idkerberget SWDNInfiernillo CILEJoinville BRZL
Kiirunavaara SWDNLa Grulla MXCO
La Perla-La Negra MXCOLeveaniemi SWDNLos Vasitos MXCO
Luossauaara SWDNMalmberget SWDN
Minarets USCA
Mineville-Port Henry USNYModarelli USNVNakerivaara SWDNNorthern Anomaly IRANPainirova SWDNPea Ridge USMORingwood USNJSaghand IRANSavage River AUTSSe Chakhum IRANSterling Lake USNYTjarrojakka SWDN
The GreatSwedish IronOre DepositsAre thisvintage
Last Type is the Iron Skarn
Carbonate or reactive rocksAre mineralized at theContacts with intrusives
Median size is only 7.2Million metric tonnes butBig ones can be 160,000,000tonnes
Grade is about normal for Iron
About 50% or so.Iron mineral of interest ismagnetite
What is not ore
• Many volcanic ore formations have tons of pyrrohtite, marcasite, and pyrite.– Iron sulfides tend not to be ore because they
require an extra process steps.
Processing Iron Ore Crushing and Grinding
Gravity Separation
Blast Furnace
Blast Furnace Operation
Blast furnace diagram1. Hot blast from Cowper stoves2. Melting zone (bosh)3. Reduction zone of ferrous oxide (barrel)4. Reduction zone of ferric oxide (stack)5. Pre-heating zone (throat)6. Feed of ore, limestone, and coke7. Exhaust gases8. Column of ore, coke and limestone9. Removal of slag10. Tapping of molten pig iron11. Collection of waste gases
Steel Converters
Casting Steel
What is Iron Used For
Iron and Steel Uses
20
18
114
47
Buildings
Construction
Cars/Transport
Containers
Other
What are the Reserves and Production for Iron?
Iron Ore Production and Reserves
0
500
1000
1500
2000
2500
3000
3500
Production Reserves/50
Mill
ion
s o
f to
ns
Other
Venezuela
Ukraine
Sweden
South Africa
Russia
Mexico
Mauritania
Kazakhstan
Iran
India
China
Canada
Brazil
Australia
United States
What is Iron Worth
Scrap Iron Prices
0.00
0.05
0.10
0.15
0.20
0.25
1934
1943
1952
1961
1970
1979
1988
1997
2006
2009$ per Lb
Around 8 to 10 cents a pound
