Posted: April 14th, 2022

Rock Cycle and Mineral Resources

Lecture 10

The Earth Is a Dynamic Planet

´ Geology ´ Study of dynamic processes taking place on the earth’s surface

and in its interior

´ Three major concentric zones of the earth ´ Core (Inner and Outer)

´ Mantle, including the asthenosphere

´ Crust ´ Continental crust

´ Oceanic crust: 71% of crust

What Are Rocks?

´ Mineral ´ Naturally occurring chemical element or compound that exists

as a crystalline solid

´ Mineral resource ´ Concentration that we can extract and process into raw

materials

´ Nonrenewable

´ Rock ´ Solid combination of one or more minerals

Igneous Rocks

´ Igneous rocks ´ Igneous—“fiery inception”

´ Magma—molten rock beneath Earth’s surface

´ Lava—molten rock when it flows onto Earth’s surface

Slow Cooling – bigger minerals with distinct crystal structure

Fast cooling – very fine grained, not crystalline

Intrusive vs Extrusive Rocks

Examples of Intrusive Igneous Rocks

´ Diorite is a coarse-grained, intrusive igneous rock.

Granite is a coarse-grained, light colored, intrusive igneous rock.

Examples of Extrusive Igneous Rocks

Basalt is a fine-grained, dark-colored extrusive igneous rock.

Obsidian is a dark- colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.

Pumice is a light-colored vesicular igneous rock. It forms through very rapid solidification of a melt. The vesicular texture is a result of gas trapped in the melt at the time of solidification.

Oceanic and Continental Crust

´ Oceanic Crust made up of Basalt (extrusive igneous rock)

´ Continental Crust made up of Granite (intrusive igneous rock)

´ Basalt is denser than granite

Sedimentary Rocks  Composed of cemented mineral

grains/rock fragments

´ Created by: ´ Weathering: breaking rocks into smaller

pieces

´ Erosion: removing grains from parent rock

´ Transportation: dispersed by gravity, wind, water, and ice

´ Deposition: settling out of the transporting fluid

´ Lithification: transforming into solid rock

Sedimentary Rocks

 Geologists define four classes of sedimentary rock. ´ Clastic: rock fragments (clasts) cemented together

´ Biochemical: cemented shells of organisms

´ Organic: carbon-rich remains of plants or other organisms

´ Chemical: minerals that crystallize from water

ChemicalClastic OrganicBiochemical

Clastic Sedimentary Rocks

 Clast size/grain size  Diameter of

fragments/grains  Range from very coarse to

very fine  Boulder, cobble, pebble,

sand, silt, and clay ´ Gravel: coarse-grained sediment

(cobble, pebble). ´ Mud: fine-grained (silt and clay) ´ As transport distance increases,

grain size decreases.

Examples of Clastic Sedimentary Rocks

Conglomerate – clasts are gravel sized or larger.

Sandstone – clasts are sand grain sized.

Shale -clasts are the size of clay grains.

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Biochemical Sedimentary Rocks

 Biochemical limestone ´ Principle compound is CaCO3

´ Forms in warm, tropical, shallow, clear, O2-rich, marine water

´ Composed of shell debris from diverse community (corals, clams, oysters, snails, brachiopods, plankton, forams, cocolithophores)

Organic Sedimentary Rocks

 Made of organic carbon— the soft tissues of living things  Coal—altered remains of

fossil vegetation ´ Accumulates in lush,

tropical wetland settings

´ Requires deposition in the absence of oxygen

 Oil shale—shale with heat altered organic matter (Kerogen)

Chemical Sedimentary Rocks  Evaporites—from evaporated seawater

´ Evaporation causes minerals to precipitate. ´ Thick deposits are the result of large volumes of water evaporating. ´ Minerals include halite and gypsum.

 Travertine—precipitated from groundwater ´ Occurs when groundwater reaches the surface ´ CO2 expelled into the air; reduced ability to hold carbonate.

´ Evaporation can also cause CaCO3 to precipitate. ´ Example: thermal (hot) or cold water springs and cave settings

´ In cave settings, Travertine builds up complex growth forms speleothems

Metamorphic Rocks

 Metamorphic rock—solid-state alteration of a protolith ´ Meta = change

´ Morphe = form

 Rocks which were originally igneous or sedimentary and have been changed by heat and pressure

 Rearrange the crystal structure of the original rock

 Limestone becomes marble; sandstone becomes quartzite, shale becomes slate

Metamorphic Rocks  Protoliths undergo slow solid-state changes in:

´ Mineralogy

´ Texture

 Metamorphic changes are due to variations in: ´ Temperature

´ Pressure

´ Tectonic stresses (compression and shear)

´ Amount of reactive water (hydrothermal fluid)

Types of Metamorphic Rocks

 Two major subdivisions—foliated and nonfoliated

´ Foliated—have a throughgoing planar fabric ´ Subjected to differential stress ´ Have a significant component of platy minerals

´ Classified by composition, grain size, and foliation type

Foliation

 Foliation—Latin folium, for leaf ´ Parallel planar surfaces or

layers in metamorphic rock

´ Gives the rock a streaked or striped appearance

´ Foliated rocks often break along foliation planes

 Due to ´ Preferred inequant mineral

orientation, or

´ Compositional banding (dark and light layers)

Foliated Metamorphic Rock

Types of Metamorphic Rocks

 Nonfoliated—no planar fabric evident ´Minerals recrystallized without

compression or shear.

´Comprised of equant minerals only

´Classified by mineral composition

NonFoliated Metamorphic Rock

The Earth’s Rocks Are Recycled Slowly

 Rock cycle ´Rocks are recycled over millions of years ´Erosion, melting, and metamorphism ´Slowest of the earth’s cycle processes

The Earth Is a Dynamic Planet

Minerals

´ Naturally occurring ´ Solid ´ Formed geologically ´ Crystalline structure ´ Definite chemical ´ composition ´ Mostly inorganic

28 © 2011 Pearson Education, Inc.

Mineral Classes

 Oxides (O2-) ´ Metal cations (Fe2+, Fe3+,

Ti2+) bonded to oxygen. ´ Examples

´ Magnetite (Fe3O4)

´ Hematite (Fe2O3) ´ Rutile (TiO2)

 Halides (Cl- or F-) ´ Examples

´ Fluorite (CaF2)

´ Halite (NaCl)

29 © 2011 Pearson Education, Inc.

Mineral classes

 Carbonates (CO32-)

´ Examples

´ Calcite (CaCO3)

´ Dolomite (Ca, Mg[CO3]2)

 Native metals

´ Pure masses of a single metal

´ Examples

´ Copper (Cu)

´ Gold (Au)

Mineral Classes

 Sulfides (S–)

´ Metal cations bonded to a sulfide anion.

´ Examples

´ Pyrite (FeS2)

´ Galena (PbS)

 Sulfates (SO42-)

´ Metal cation bonded to a sulfate anionic group.

´ Many sulfates form by evaporation of seawater.

´ Examples

´ Gypsum (CaSO42H2O)

´ Anhydrite (CaSO4)

Mineral Classes

´ Oxygen and Silicon are the two most abundant elements in the crust.

 Silicates – Silica- 4 oxygen atoms surround a single silicon atom, forming (SiO4)4- Each oxygen atom covalently shares 1 electron with the silicon atom, jointly filling its outermost shell.

Mineral Resources

 Naturally occurring mineral deposit

´ Concentrated

´ Can be extracted and used

´ Some are a single element

´ – Cu, Au, diamonds

´ Most are compounds

´ – NaCl, CaSO4

´ Metallic or nonmetallic

´ High and low-grade ores

We Depend on a Variety of Nonrenewable Mineral Resources

 Ore ´Contains profitable concentration of

a mineral ´May be high-grade or low-grade

 Metallic mineral resources ´Aluminum ´Steel: a mixture of iron and other

elements ´Copper ´Gold ´Molybdenum

We Depend on a Variety of Nonrenewable Mineral Resources

´ Nonmetallic mineral resources ´Sand ´Gravel ´Limestone ´Phosphate

Life Cycle of a Mineral Resource

 Mineral resources go through life cycle ´ Mining

– Locate and extract ´ Conversion to products

– Purify useful mineral – Manufacture product

´ Disposal or recycling – Some minerals corrode away – Metals wear through friction – Some are pollutants – Metals commonly are recycled

Supplies of Nonrenewable Mineral Resources Can Be Economically Depleted

´ Reserves ´Identified deposits from which we can extract the

mineral profitably at current prices ´ Economic depletion

´Occurs when extraction costs more than remaining deposits are worth

´ Depletion time ´Time to use a certain portion (usually 80%) of reserves

at a given rate of use

Supplies of Nonrenewable Mineral Resources Can Be Economically Depleted

´ Options when a resource becomes economically depleted ´Recycle or reuse existing supplies ´Waste less ´Use less ´Find a substitute ´Do without

What Are The Environmental Effects of Using Nonrenewable Mineral Resources?

´ Extracting minerals from the earth’s crust and converting them into useful products: ´ Disturbs the land

´ Erodes soils

´ Produces large amounts of solid waste

´ Pollutes the air, water, and soil

Rock Cycle and Mineral Resources�
The Earth Is a Dynamic Planet
Slide Number 3
What Are Rocks?
Igneous Rocks
Slow Cooling – bigger minerals with distinct�crystal structure
Fast cooling – very fine grained, not crystalline
Intrusive vs Extrusive Rocks
Examples of Intrusive Igneous Rocks
Examples of Extrusive Igneous Rocks
Oceanic and Continental Crust
Sedimentary Rocks
Sedimentary Rocks
Clastic Sedimentary Rocks
Examples of Clastic Sedimentary Rocks
Biochemical Sedimentary Rocks
Organic Sedimentary Rocks
Chemical Sedimentary Rocks
Metamorphic Rocks
Metamorphic Rocks
Types of Metamorphic Rocks
Foliation
Foliated Metamorphic Rock
Types of Metamorphic Rocks
NonFoliated Metamorphic Rock
The Earth’s Rocks Are Recycled Slowly
The Earth Is a Dynamic Planet
Minerals
Mineral Classes
Mineral classes
Mineral Classes
Mineral Classes
Mineral Resources
We Depend on a Variety of Nonrenewable Mineral Resources
We Depend on a Variety of Nonrenewable Mineral Resources
Life Cycle of a Mineral Resource
Supplies of Nonrenewable Mineral Resources Can Be Economically Depleted
Supplies of Nonrenewable Mineral Resources Can Be Economically Depleted
What Are The Environmental Effects of Using Nonrenewable Mineral Resources?

———

Mineral Resources and the Rock Cycle

tenth lecture

The Earth Is a Changing Planet

‘Geology’ is the study of dynamic processes occurring on the earth’s surface.

as well as its interior

‘The earth’s three major concentric zones ‘ (Inner and Outer)

The asthenosphere is part of the mantle.

‘Crust’ refers to the continental crust.

‘Oceanic crust: 71% of the crust

What Exactly Are Rocks?

´ Mineral ´ Naturally occurring chemical element or compound that exists

as a crystalline solid

´ Mineral resource ´ Concentration that we can extract and process into raw

materials

´ Nonrenewable

´ Rock ´ Solid combination of one or more minerals

Igneous Rocks

´ Igneous rocks ´ Igneous—“fiery inception”

´ Magma—molten rock beneath Earth’s surface

´ Lava—molten rock when it flows onto Earth’s surface

Slow Cooling – bigger minerals with distinct crystal structure

Fast cooling – very fine grained, not crystalline

Intrusive vs Extrusive

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