Unit 5 - Earth Resources

Real-Life Applications

Minerals that are of economic value. Types of mineral deposits. Factors that allow minerals in the

different types of deposits to be profitable.

Open pit versus underground mining. Various exploration and processing

techniques.

Unit Overview

Energy resources (e.g. petroleum) Origin of petroleum, process of

formation, migration of petroleum, accumulation of petroleum, extraction and refining techniques.

Sustainable development in relation to petroleum.

Unit Overview

Economic Minerals – Minerals that can be extracted, processed, and marketed at a profit.

Factors (Economic Or Not):- interest in the mineral,- size of the deposit,- mineral concentration,- mineral depth below the surface,

and - market value.

An ore is a natural material with a high concentration of economically valuable minerals that can be mined for a profit. Show Voisey’s Bay Ore.

Houses Cars Toothpaste Plumbing Supplies Wiring Planes Electronics Jewelry Glass ETC………….

Why Do We Need Mines?

If we can’t grow it, THEN it has to be mined!

Type 1) Magmatic Deposits (Metallic Deposits)

- Accumulations of metals associated with magma that forms igneous rocks.

- Certain metals are enriched in certain magmas and further concentrated during cooling of the magma.

Economic Mineral Deposits

Magmatic Deposits: A) Layered Gravitational Settling

- Heavy minerals that crystallize early, settle and concentrate (high concentrations) on the bottom of the magma chamber. This results in a layered deposit.

High-density minerals sink to the bottom of the magma chamber and cummulate.

E.g. Chromite

ExamplesChrome in chromiteIron in magnetitePlatinum

Magmatic Deposits: B) Disseminated- Deposits in which the metal is evenly

distributed in generally low concentrations throughout large masses of igneous rock. E.g. Porphyry copper deposit

- (e.g., Sudbury, Ontario and Voisey’s Bay, Newfoundland and Labrador)

A sample of nickel-bearing rock from Sudbury, Ontario.

Nickel is found in the mineral pentlandite.

Economic Mineral DepositsNon-metallic Deposits

- Diamonds: - Most diamonds are found in unique

ultramafic igneous rocks called kimberlites.

- Magmas are generated by partial melting of asthenosphere (below 150 kilometres), which rises quickly to the surface. During their ascent, the magmas pick up diamonds from solid lithospheric mantle. Typically under cratons and along subduction zones. Remember that temperature and pressure conditions need to be JUST RIGHT!

Copyright (c) 2005 Pearson Education Canada Inc.21-10

Diamonds and Kimberlite Pipes!

Type 2) Hydrothermal Deposits- Any concentration of metallic minerals

formed by the precipitation of solids from hot mineral-laden water (i.e. hydrothermal solution).

- Hot water dissolves and transport minerals. Interconnected openings in the rock allows the solutions to move, and chemical reactions result in deposition.

- Deposition can be caused by boiling, by a drop in temperature, by mixing with a cooler solution, or by chemical reactions between the solution and a reactive rock. - PRODUCES VEIN DEPOSITS!

Hydrothermal Deposits- NOTE: can occur as disseminated

deposits, which are distributed throughout the rock body, rather than concentrated in veins.

- These are called porphyry deposits (i.e. low grade and large volume).

- Minerals to get: pyrite; galena, sphalerite, chalcopyrite, gold, and silver.

Hydrothermal Deposits at Black Smokers

Interconnected openings!

Pegmatite and Hydrothermal Disseminated Deposits

Type 3) Sedimentation Secondary Enrichment A class of residual deposits formed by both

the removal of valueless material in solution (water or air) and the solution and redeposition of valuable ore minerals.

Because solution and redeposition occurs the process is known as a secondary enrichment.

Weathering - Secondary Enrichment- Bauxite:

- Principal ore of aluminum.- Forms in rainy tropical climates from

chemical weathering and the removal of undesirable elements by leaching.

- Potassium, sodium, and calcium are removed by infiltrating groundwater from the upper soil and a residue of less soluble iron and aluminum oxides and hydroxides are left behind.

- Stratiform Deposits- Copper-bearing brines moving through

coarse-grained sedimentary rock are forced upward through oxygen-poor, sulphide-rich mud, which promotes precipitation of minerals.

Sedimentary Deposits- Banded Iron Formations

- Conditions during the early Precambrian resulted in large quantities of ferrous iron in solution.

- At some point, photosynthesizing bacteria generated sufficient oxygen to precipitate iron oxide minerals. The iron in solution went into compound with the oxygen that was created by the bacteria.E.g. Bell Island Deposit

Dark bands since the oxygen was released in “pulses”.

Type 4) Placer Deposits- Formed when heavy metals (e.g. gold) are mechanically concentrated by currents (e.g. loss of current velocity).

- Stream and beach environments. - E.g., Gold, Platinum, Diamonds.

Type 5) Metamorphic Deposits- Many of the most important metamorphic ore deposits are produced by contact metamorphism (NOT REGIONAL METAMORPHISM).

- Examples include:- Sphalerite (zinc)- Galena (lead) - Chalcopyrite (copper)

The host rock is recrystallized and chemically altered by heat, pressure, and hydrothermal fluids (chemically-active fluids) that come from the hot magma chamber.

Skarns are Associated with Contact

MetamorphismLimestone (host rock in diagram) gets altered. As hot, iron-rich fluids move through limestone, chemical reactions take place. The reactions release carbon dioxide gas and helps with the movement of metals (e.g. iron). The metal-rich deposits that form are called skarns.

Sometimes the metals are disseminated and sometimes they are concentrated.

1) Open Pit 2) Underground

TYPES of MINES

Open-pit Mining - surface mining in which huge portions of Earth are dug from the surface to extract the desired mineral(s) within it.

Open-pit mines are used when deposits of commercially useful minerals or rock are found near the surface.

As a result, the potential exists for considerable destruction to both surface soil and vegetation. The release of significant amounts of mine dust also becomes an issue.

Open pit mines are usually accessed by surface terracing (e.g. cork screw roads), thereby allowing technological equipment to follow the shape of the deposit. These mines are safer and are less costly!

Clearing:First the bulldozing and preparation kills all existing floral (plants) and fauna (animal) species on the site.

Mining:Famous for its large amount of dust production, which is not good for flora and fauna. Noise pollution is also a negative impact.

Chemical and Toxic Pollution:The chemicals and toxins that are used seep into the nearby water supplies and pollute them.

Impacts of Open-pit Mining

Soil Degradation:Strong acids or bases begin to seep into the surrounding soil making them useless in terms of growth.

Exposure:The exposure to weathering erodes the soil much quicker (all due to lack of vegetation). Some soils endure mass compaction, which also prevents growth.

Scree or Talus (think landslide):Mining operations cause mountain sides to start to cut into Earth creating a scree drop effect.

Impacts of Open-pit Mining

Pros/Cons Open-pit mining (in relation to underground

mining) allows for lower costs, greater safety, and mechanically easier operations.

Surface mining is more efficient than underground mining in terms of recovery, grade control, economy, and flexibility of operation.

However, many deposits are too small or irregular, and or too deeply buried to be extracted efficiently by surface mining methods. As a result, the mines end up being converted to underground mining or abandoned all together.

Underground mining is done when the rocks, minerals, or gemstones are too far underground to get out with surface mining (or if the shape of the ore body dictates it). Some techniques used include: borehole mining, shaft Mining, and shaft mining.

This type of mining is also dependent on the shape of the deposit.

Underground Mining

Accessing underground ore can be achieved via a decline (ramp), inclined vertical shaft, or adit.

Levels are excavated horizontally off the decline or shaft to access the ore body. They then excavate perpendicular (or near perpendicular) to the level into the ore.

The deepest mines in the world are the TauTona (Western Deep Levels) and Savuka gold mines in the Witwatersrand region of South Africa, which are currently working at depths exceeding 3,900 m (12,800 ft).

Less damage to surface and soil and vegetation.

Mine dust levels in the atmosphere are less. Due to having to install shafts and/or

elevators, these mines are more costly and less safe.

Pros/Cons

Exploration Techniques (For Economic Mineral Deposits)

· Seismic records (Core Lab)· Remote sensing · Prospecting· Observing drill cores· Cross-sections· Geological mapping (Core Lab)· Magnetic surveys· Gravity surveys· Geochemistry

SeismicRecords

3-D

2-D

On Water

On Land

Airborne Geophysics – Remote Sensing

Helicopter

Bush

Cable

“Bird”

Acquiring information without “touching” the phenomenon or object. Aircraft or satellites!

Aerial sensor technologies are used to detect and classify objects on Earth (or under the surface) by means of emitted signals (e.g. electromagnetic radiation).

Geochemical Anomalies - Geochemistry

Prospecting

Prospecting is physical labour. It involves traversing (traditionally on foot or on horseback), panning, sifting and outcrop investigation. Essentially, one is looking for signs of minerals, fossils, or precious metals.

Observing Drill CoresA cylinder of rock is removed from the subsurface using a drill. It is then studied in detail. Things that can be determined include: rock types; structural features; fossils; petroleum staining; mineral percentages, etc.

Cross-sections – A slice through Earth!

Geological Mapping

Magnetic Surveys

Iron-bearing orebody?

Thanks to a ground magnetic survey!

Gravity SurveyGravity surveys provide considerable information about shallow crustal structure as well as assisting directly with mineral exploration. The sources of gravity anomalies are variations in density of different rocks. Gravity measurements are used to estimate the depths and geometry of sedimentary basins, to map major structures, to detect buried intrusions (some may have generated hydrothermal mineral deposits) and to investigate massive deposits (e.g. of iron ore).

(i) floatation (ii) gravity separation (iii) heap leaching (iv) pyromet (v) hydromet

Ore Processing Techniques

Floatation involves mixing grounded ore with water, oil, and chemicals. The grounded ore becomes suspended in the water and is subjected to bubbles of air due to the presence of chemicals. This causes the minerals and/or elements of value to float to the top of the container where it (they) can be scraped off.

I) Floatation

Scrape this off the top!

Gravity separation involves feeding grounded ore into a pulsating body of water, which serves to settle out the heavy material while

floating away the light material. If the heavy material is what one wishes to retain, then it is taken from the bottom. If the light material is what one wishes to retain, then it is taken from the top.

II) Gravity Separation

Heap leaching commences by placing the grounded ore as a layer (or layers) onto impermeable material. The “heap” of material is irrigated with a liquid (e.g. acid solution), which percolates down through dissolving away the valuable minerals and/or elements.

III) Heap Leaching

Pyromet involves using heat to separate the minerals and/or elements of value from the ore. Heating separates the materials by density and

the desired minerals and/or elements can be removed.

IV) Pyromet

Hydromet is a chemical method that involves oxidation and acid leaching to separate out the desired minerals and/or elements.

V) Hydromet (e.g. Long Harbour, Newfoundland. Voisey’s Bay, Labrador Ore

Petroleum is a naturally occurring flammable liquid that is found in geologic

formations below Earth’s surface and consists of a mixture of hydrocarbons (i.e. compounds comprising of carbon and hydrogen atoms).

Also referred to as crude oil; however, both crude oil and natural gas are accepted under the term petroleum.

Crude oil is a mixture of hydrocarbons that exist in a liquid state in underground

reservoirs and remain in a liquid state once subjected to atmospheric conditions.

Hydrocarbons are chemical compounds that involve hydrogen and carbon atoms. Examples include: butane (C4H10), propane (C3H8), ethane (C2H6), and methane (CH4). (i.e. wet gases).

Note: If predominantly methane exists, then it is referred to as dry gas.

Processes in the Formation of Petroleum:

1) Organic Matter:Microscopic marine animals (i.e. zooplankton) and plants (i.e. phytoplankton) are the main sources of organic matter in the production of petroleum. Such microscopic species are diatoms, foraminifera, radiolarian, and benthic algae.

Origin and the Process of Formation of Petroleum.

The abundance of organic matter is determined by:

i) the amount of light; ii) water depth; iii) latitude; iv) water temperature; v) water turbidity; and vi) the abundance of nutrients

preferred by plants (e.g. phosphates and

nitrates).THINK ABOUT WHERE ON EARTH SPECIES LIKE TO LIVE!THINK ABOUT WHAT IS REQUIRED FOR LIFE TO EXIST AND TO THRIVE!

(2) Preservation Potential: Preservation potential means the conditions that

favour the preservation of organic matter.

The two most important conditions are: 1. Anaerobic conditions

- Low oxygen content. Cannot have any decay!

- Environments: Swamps and lagoons.

2. Rapid Sedimentation By Fine-grained material.

- Examples of fine-grained material include mud-size, silt-size, and sand-size particles.

Cannot have any decay!

Formation of Petroleum:

An example of the interconnectedness of the Earth’s spheres. SYSTEMS APPROACH!

Discuss!

Kerogen is a mixture of organic matter in sediments from which petroleum is

released.

Processes and Techniques Involved in Extracting and Refining Hydrocarbons

There are three phases in the evolution of organic matter into petroleum.

(i) diagenesis(ii) catagenesis(iii) metagenesis DCM!

During diagenesis there is shallow burial of organic matter at near normal temperature and pressure as well as some decay.

Methane, carbon dioxide, and water are released leaving behind the complex hydrocarbon called kerogen.

1) Diagenesis:

First gas!

Deeper burial results in increased temperature and pressure.

Petroleum is released from the kerogen.

2) Catagenesis:

First oil and second gas is released!

The metagenesis phase involves even higher temperature and pressure conditions (verging on metamorphism).

The only hydrocarbon that is released during this phase is methane.

At this point the petroleum has matured enough to migrate to traps.

3) Metagenesis:

The oil and gas needs to be trapped! Drill into the traps!

(i) source rock (ii) reservoir rock (iii) cap rock

Components Involved in the Formation of Petroleum Traps.

Must contain an abundance of organic matter.

Petroleum is often created and released from the source rock while lithification is occurring.

Examples are shale and limestone.

Source Rock

Reservoir rock requires high porosity and high permeability since it is the rock which petroleum moves through and is stored in.

Note: Porosity is the volume of pore spaces or

holes between sediment grains. (STORAGE AREAS)

Permeability is the interconnectiveness of the pores, thereby allowing the movement of the petroleum. (ALLOWS FOR FLOW)

Reservoir Rock

Porosity of a material is influenced by:

i) particle shapeii) particle sizeiii) the degree of sediment sorting.

BEST POROSITY Large, rounded, and well-sorted

particles offer higher porosity (particularly if the amount of cement between the particles is limited). Usually, the higher the porosity and the larger the pore spaces, the higher the permeability.

Examples of reservoir rocks are sandstone, dolomite, and conglomerate since all have both high porosity and permeability.

Cap rock is an impermeable rock that serves to trap petroleum from either escaping to the surface or spreading throughout the rock as opposed to being confined.

Note: Petroleum exists within reservoir rock between

sediment as opposed to being confined as a whole volume of liquid petroleum. “There are no ponds of petroleum in the ground”.

Cap Rock – e.g. Shale

(i) anticline trap (ii) fault trap (iii) salt dome trap (iv) stratigraphic trap (THREE SUB-

TYPES)

Types of Petroleum Traps

If the petroleum does not get trapped, then there will not be a concentration or build-up of oil (i.e. a deposit).

Anticline Trap:If a porous and permeable rock layer(s) (e.g., sandstone, dolomite, conglomerate) is located between impermeable rock layers (e.g. shale) and the rock layers are folded into an anticline, petroleum (crude oil and natural gas) can move upward in the porous and permeable reservoir rocks, and accumulate in the upper region of the anticline.

Impermeable Cap Rock

Porous and Permeable Reservoir Rock

Gas

Oil

WaterWater

Well

Sandstone?Dolomite?Conglomerate?

Shale?

Source rock NOT evident in diagram!

Fault Trap: If faulting can shift permeable and

impermeable rocks so that the permeable rocks always have impermeable rocks above them, then a petroleum trap could form.

Note that both normal faults and reverse faults can form this type of oil trap

Impermeable Cap Rock

Porous and Permeable Reservoir Rock

Impermeable Cap Rock

Gas

Water

Well

Oil

Well

Oil

Water

Salt has moved up through the Earth, punching through and bending rock along the way.

Petroleum can come to rest right up against the impermeable salt, which makes salt an effective trap rock.

Salt Dome Trap:

Limestone reef trap is a type of stratigraphic trap (Textbook - Page 604).

Coral reefs thrive for quite some time, comprising of mostly limestone rocks (possibly dolomite).

If coral reefs become buried by other impermeable sediments (which eventually get lithified), they can form excellent

petroleum reservoirs and traps.

Stratigraphic Trap:Limestone Reef Trap

Note: the physical property DENSITY is what distributes petroleum in a reservoir.

Water is denser than oil and oil is denser than gas.

Therefore, when drilling into a petroleum trap, gas is encountered first followed by oil and lastly water.

Some reservoirs may have all three components, whereas some reservoirs may only have two components, one component, or no components (i.e. dry well).

Depends on organic matter amount, organic matter type, preservation, and maturation!

The two main means of extracting petroleum from Earth include:

(i) drilling (i.e. production wells) (ii) surface extraction (i.e. open pit mining)

Drilling Drilling can take place on land (e.g. Alberta),

ice (e.g. Arctic), or water (e.g. Offshore Newfoundland).

A proportion of petroleum in a trap is under natural pressure and therefore, will be released naturally when tapped by a drill. Watch for blowouts!

There will be another proportion of petroleum that will remain in the trap due to loss of pressure.

High gas content that is under pressure due to shaking.If the can was opened, some soda will be released naturally from the can. The remaining soda will not be under pressure.

Other techniques for getting petroleum out of traps include:- pumping in water;

and- pumping in gas.

Filling the reservoir will be required to get the remaining petroleum from the trap.

Surface Extraction (i.e. open pit mining)

Alberta oil sands (i.e. the tar sands). The petroleum is extracted directly from the surface (open-pit mining).

The petroleum migrated towards the surface and volatiles (e.g. water) were lost to the atmosphere.

Therefore, the petroleum experienced increased viscosity (i.e. thickness), thereby preventing the petroleum from spreading out and/or dissipating.

The reservoir consisted of loose (unconsolidated) sediment that exhibited high porosity and permeability, but no cap rock.

In some instances, steam is injected directly into the tar sands to mobilize the hydrocarbons, which are then recovered from pumps much like conventional crude oil. Simply trying to decrease the viscosity!

Fort McMurray’s Athabasca oil sands is an example of steam injection.

Includes distillation; cracking; and reforming. (i) Distillation Petroleum is first de-salted and dewatered. It then enters a distillation chamber. Petroleum contains hundreds of different types

of hydrocarbons that are all mixed together. Different hydrocarbon chain lengths (greater

lengths) all have progressively higher boiling points. Therefore, they can all be separated by distillation (i.e. heating).

Methods of Refining Petroleum

(ii) Cracking Heat is added to the chamber to separate

the petroleum into fractions based on boiling points. The bottom fraction is removed to another column for further separation.

Note the fractions such as asphalt; paraffin wax; lubricants; jet fuel; diesel; kerosene; and gasoline.

(iii) Reforming Involves heat, pressure, and the use of

catalysts (speeds up chemical reaction rates) to reform different hydrocarbon compounds.

What is meant by sustainable development? DISCUSS!

How does it relates to extracting and processing Earth Resources?

Students should consider economics, the environment, any political/social/cultural aspects that relate to extraction of resources.

Examples to talk about are: Hibernia; Hebron; Terra Nova; Whiterose; Avalon Ben Nevis (offshore NL petroleum deposits); Fort McMurray’s Tar Sands (Alberta); and Voisey’s Bay (Labrador) as well as Long Harbour’s hydromet facility (Newfoundland).

Sustainable Development

You must realize that the decisions that you make today will impact our future.

Think sustainable factors!