geology introduction to earth

An occurrence of minerals or metals in sufficiently high concentration to be profitable to mine and process using current What is an ore deposit?... What is ore grade?· Weight percentage

• 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

Note for comparison: Silicon 28% Oxygen 46%

Metal

Concentration (% by weight)

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

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.

Typical Grade (% by weight)

Typical Grades of Ore

Deposits

Copper Nickel Zinc Uranium

As magma cools, more abundant

metals (silicon, aluminum) deposit

first

Solidification of magma releases water

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

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

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 AcresSome 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