MMPE 290 Introduction to Mining & Mineral Process EngineeringMining Geology and Exploration

How much metal is available? What is a mineral? What is

ore? How do ore deposits form? Mining exploration methods Role of exploration in mining Case histories

Mining Geology and Exploration

Note for comparison:Silicon 28%Oxygen 46%

MetalConcentration(% by weight)

Aluminum 8.0Iron 5.8Copper 0.0058Nickel 0.0072Zinc 0.0082Uranium 0.00016Lead 0.001Silver 0.000008Gold 0.0000002

Economically Important Metal Concentrations in Earth’s Crust

A solid naturally-occurring compound having a definite chemical composition

Examples:

quartz - SiO2 (an oxide)

hematite - Fe2O3 (another oxide)

covelite - CuS (a sulphide)

What is a mineral?

An occurrence of minerals or metals in sufficiently high concentration to be profitable to mine and process using current technology and under current economic conditions.

What is an ore deposit?

What is ore grade?

· Weight percentage (base metals)

· Grams/tonne or oz/ton (precious metals)

Ore grade is the concentration of economic mineral or metal in an ore deposit.

MetalTypical Grade(% by weight)

Aluminum 30Iron 53Copper 0.5-4Nickel 1Zinc 4Uranium 0.3Lead 5Silver 0.01Gold 0.0001-0.001

Economically Important Metals Typical Grades of Ore Deposits

10-7

10-5

10-3

10-1

101

103

10-4

10-3

10-2

10-1

100

101

102

AluminumIron

CopperNickel

Zinc

Uranium

Lead

Silver

Gold

y = x

Typ

ical

Ore

body

Con

cent

ratio

n

Crustal Concentration

What does it take to be an ore deposit?

As magma cools, more abundant metals (silicon, aluminum) deposit first

Solidification of magma releases water - a hydrothermal solution

Minerals precipitate from hydrothermal solution and deposit in cracks or veins in rock

Hydrothermal Ore Deposits

Concentration of minerals caused by high temperatures and pressures near intrusions

Examples:

Lead-zinc deposits in southeast B.C.

Diamonds

Garnets

Metamorphic Ore Deposits

Hydrothermal and Metamorphic Ore Deposits

Intrusion

Hydrothermal solutions

entering veins in rocks

Geyser or hot spring

Ore deposit

Alteration of rocks by heat and pressure

zoning

Deposition of dense, resistant minerals in streams, lakes etc (Alluvial Deposits), e.g. Placer gold

Precipitation of minerals from ancient oceans (Evaporite Deposits), e.g. Potash and salt deposits

Accumulation, burial and petrification of vegetation, e.g. Coal Deposits.

Sedimentary Ore Deposits

Exploration Methods

· Remote sensing · Geological mapping· Geophysical surveys· Geochemical surveys· Bulk sampling · Drilling (core or destructive)

Airborne Geophysics

Helicopter

Bush

Cable

“Bird”

GEOPHYSICAL

METHODS

Geochemical Anomalies

DIAMOND DRILL

DIAMOND DRILL

HOLE SIZES

SURFACE SET DIAMOND DRILL CORE BIT AND REAMING SHELL

Senior Mining Company Exploration Expenditures - 1997

Total: $817.7M

Junior Mining Company Exploration Expenditures - 1997

Total: $262.2M

Role of Exploration

Each ton of ore mined must be replaced with another ton to continue business.

The alternative to exploration is acquisition of mining properties.

Exploration has a high failure rate, but this should not affect a diversified mining company.

Exploration costs are tax-deductible.

Diamonds in Canada?

Diamonds are formed at high pressure deep in the earth and transported to surface in kimberlite pipes

Other minerals also formed if pressures high enough - indicator minerals

Indicator minerals are mobile and easily transported by erosion.

Direction of glacier flow

Indicator minerals

Kimberlite pipe

An eroded kimberlite pipe

Lac de Gras

The Ekati Mine

Recommended Reading

Fire into Ice

Charles Fipke and the Great Diamond Hunt

by Vernon Frolick

Raincoast Press

Formed 30-50 million years ago by hydrothermal activity in sedimentary rocks

Part of a large mineralized zone extending into Mexico and Central America

Carlin, Bootstrap, Cortez, Gold Acres

Some deposits low grade but can now be processed using heap leach technology

Nevada Gold

Volcanic and igneous activity in Andes produces a variety of rich mineral deposits

Minerals are exposed at or very near the surface - leads to oxidation requiring different kinds of mineral processing

Transport of mineral products, power and water supply a concern in high Andes

South American Ore Deposits