geology introduction to earth

MMPE 290 Introduction to Mining & Mineral Process Engineering Mining Geology and Exploration Mining Geology and Exploration • • • • • • How much metal is available? What is a mineral? What is ore? How ore deposits form? Mining exploration methods Role of exploration in mining Case histories Economically Important Metal Concentrations in Earth’s Crust Concentration Metal Aluminum Iron Copper Nickel Zinc Uranium Lead Silver Gold (% by weight) 8.0 5.8 0.0058 0.0072 0.0082 0.00016 0.001 0.000008 0.0000002 Note for comparison: Silicon 28% Oxygen 46% What is a mineral? A solid naturally-occurring compound having a definite chemical composition Examples: quartz - SiO (an oxide) hematite - Fe O (another oxide) covelite - CuS (a sulphide) What is an ore deposit? 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 ore grade? Ore grade is the concentration of economic mineral or metal in an ore deposit · Weight percentage (base metals) · Grams/tonne or oz/ton (precious metals) Economically Important Metals Typical Grades of Ore Deposits Typical Grade Metal Aluminum Iron Copper Nickel Zinc Uranium Lead Silver Gold (% by weight) 30 53 0.5-4 0.3 0.01 0.0001-0.001 What does it take to be an ore deposit? 10 Iron Aluminum Typical Orebody Concentration 10 Lead Zinc Copper Nickel 10 Uranium y=x -1 10 Silver -2 10 -3 10 Gold -4 10 -7 10 -5 10 -3 10 -1 10 Crustal Concentration 10 10 Hydrothermal Ore Deposits 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 Metamorphic Ore Deposits Concentration of minerals caused by high temperatures and pressures near intrusions Examples: Lead-zinc deposits in southeast B.C Diamonds Garnets 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 taxdeductible 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 easily transported by erosion and An eroded kimberlite pipe Direction of glacier flow Indicator minerals 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 Nevada Gold 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 South American Ore Deposits 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