Mineral Resources & Mining

Eight chemical elements make up 98.3% of Earth’s crust.

OxygenSiliconAluminumIronCalciumSodiumMagnesiumPotassium

Other elements comprise 1.7% of Earth’s CrustMany of these are important to industryDistribution of these elements is not

uniform across the Earth.

Examples:Ni, Ti, Cr, Cu, Pb, Zn, U, Pt, Au, Ag, etc.

Ore If one or more chemical elements occur in

sufficient abundance that they may be mined for a profit, then the rock is termed an ORE.

Classification of Mineral Resources• Metallic Mineral Resources• Abundant (Iron, Aluminum, Magnesium, Manganese,

Titanium)• Scarce (Copper, Lead, Zinc, Chromium, Nickel, Gold,

Silver)• Non-Metallic Mineral Resources• Construction (Sand, Gravel, Clay, Limestone,

Gypsum)• Agriculture/Industry (Phosphates, Nitrates, Sodium

Chloride, Sulfur)• Ceramics/Abrasives (Feldspar, Clay, Quartz,

Diamond, Pumice, Garnet, Corundum)

Processes of ore concentration are related to rock formation. Rocks are grouped into three major families,

based upon their processes of formation.Igneous RocksSedimentary RocksMetamorphic Rocks

Ore formation by igneous processes Crystal Settling

Dense minerals crystallizing in magma, settle to the bottom of the magma chamber– Ex. – Chromium, Platinum, Nickel, Copper, Lead

Ore formation by igneous processes

Hydrothermal enrichment

water, superheated by magma, dissolves minerals and deposits them in “veins”– Ex. – Copper, Gold,

Silver

Ore Formation by Igneous Processes Lode – many thick mineral veins in a small region

– Ex. – The “Mother Lode” during the California gold rush

Hydrothermal Enrichment Pegmatites – “veins” in rocks

Common form of gold enrichment

Exhalites – Submarine vents of hot, mineral-rich water

“Black Smoker Chimneys” – hydrothermal ventsAssociated with mid-ocean ridges

“Black Smokers”

Sulfide Mine in an Exhalite Deposit

Ore Formation by Sedimentary Processes Placer deposits

Moving water erodes rocks releasing heavy minerals which settle on the bottom of stream beds (ex. – gold)– Ex. - gold

Ore Formation by Sedimentary Processes Evaporite deposits

Precipitation of salt in shallow marine basins or saline lakes (in arid climates)– Ex. – halite, gypsum, borax

Ore Formation by Metamorphic Processes During contact metamorphism, pre-existing

rock is altered forming oresEx. – Lead, Copper, Zinc

Prospecting and Exploration

Methods of Discovery:Satellite and Aerial Photography Remote Sensing Geological MappingMagnetic Mapping Gravity Mapping Radioactivity MappingGeochemical Sampling Electrical Sounding Ground-Penetrating RadarSeismic Methods – Reflection - Detailed but Expensive – Refraction - Cheap but Not Detailed

Core Sampling and Well Logging

Economic Factors in Mining Richness of Ore Quantity of Ore Cost of Initial Development Equipment, Excavation, Purchase of Rights Operating Costs: Wages, Taxes, Maintenance,

Utilities, Regulation Price of the Product Will Price Go up or down?

Issues in Mineral Exploitation

Who Owns (Or Should Own) Minerals?Landowner Discoverer Government

Unclaimed Areas: Sea Floor Antarctica

Who Controls Access for Exploration?Remote Sensing vs. Privacy

Types of Mines Surface

Open pit (Au, Cu)Quarries (stone, gravel, sand)Strip mines (coal)

Subsurface (underground) Placer – dredging (Au) Seafloor– nodules (Mn, Ni, Fe)

Problems with MiningSafety

Mine Wastes/PollutionHazardous working conditionsNoise

Economic Impact"Boom and Bust" Cycles

Environmental ProblemsExplorationConstruction & OperationWaste Disposal

Reclamation Returning the land to

a more natural state after mining operations have ended

Mine Albert, Quebec, before and after reclamation. Government of Quebec

Economic Implications Ores are not found everywhere Some ores are richer than others Ore distribution is a function of geology Ore distribution is not equal across the world Some nations are rich in mineral resources Other nations have few mineral resources No nation is self sufficient in mineral resources

Environmental Considerations Mining leaves holes in the ground Mining adds unusual quantities of sediment

to rivers and streams Mining exposes minerals to interaction with

surface and groundwater, which may contaminate them

Mine waste may be unstable - landslides Smelting may pollute air and water

Why do we need mines?

We all make choices. Industrialized societies depend on mineral

resources Environmental problems must be considered in

extracting wealth from the Earth Its not Good (environment) vs. Evil (industry) It’s a compromise, of which, we must make the

best!