A brief introduction to A brief introduction to minerals, rocks and the rock minerals, rocks and the rock cyclecycle

rockrock

collection ofone or moreminerals

mineral

A collectionof one or moretypes of atoms

minerals

Minerals and RocksMinerals and RocksMinerals

-> To be considered a mineral, it must:

1. Occur naturally

Minerals blocks of rocksMinerals: the building

2. Be inorganic3. Be a solid

5. Have a definite chemical composition

4. Possess an orderly internal structure

Definition of a mineral Definition of a rock

-> different from that of a mineral. A rock:

1) is solid

Minerals blocks of rocksMinerals: the building

4) occurs naturally as part of our planet

2) contains a mixture of one or more minerals

3) May contain a non-mineral

Rocks and minerals

Some rocks composed entirely of one minerallimestone (calcite)

Minerals blocks of rocksMinerals: the building

Most rocks have more than one kind of mineralgranite

Some rocks contain non-mineral mattercoal (has organic debris)obsidian (volcanic glassy rock -> not crystalline)

Granite & constituent minerals

The composition of mineralsThe composition of mineralsMinerals

Minerals

Over 4000 minerals: only few dozen are abundant, making up most rocks of Earth’s crust

=> rock-forming minerals

Only 8 elements make up most of crust’s minerals & represent over 98% of the continental crust

The two most abundant elements:

Silicon (Si)Oxygen (O)

Average composition of the continental crustAverage composition of the continental crust

Percent of elements by WEIGHT

Minerals

112 known elements

Only 92 occur naturally

The composition of mineralsThe composition of mineralsMinerals

Atomic structure The silicates

Every silicate mineral contains the elements

silicon (Si)oxygen (O)

Nearly every silicate mineral combines with one or more additional elements to achieve electrical neutrality

Mineral groups

Silicon and Oxygen combine to form the most common mineral group, the silicates.

The silicates

The fundamental building block of all silicates is the

silicon-oxygen tetrahedron

Two different views of this arrangement:Two different views of this arrangement:

silicon atom

oxygen atoms

1) Mineral groups

Light colored (crust, esp. continental crust)Non-ferromagnesian (felsic) silicates

Feldspar (Si, O, Al, K, Na, Ca) - mostly white or pink50% of earth’s crust !

Quartz (SiO2 =silica) - commonly transparentsilicate that consists only of silicon and oxygensecond most abundant in crust!

Muscovite (Si, O, Al, K, H) – most common micacleavage in sheets, glass in Middle agessparkle in rocks, mica flakes in sand

1) Mineral groups

The silicates

Remember:Silicates are the most abundant mineral group with the silicate ion as basic building block.

Dark colored (mantle, basalt, continental crust)Ferromagnesian (mafic) are dark silicates, contain ions of iron

and/or magnesium)

Olivine – black to olive green, in basaltPyroxene – important component of earth’s mantleHornblende – important component of continental rockBiotite – iron rich mica, component of continental rock

Mineral groups

The silicates

Remember:Silicates are the most abundant mineral group with the silicate ion as basic building block.

Important Nonsilicate Minerals

Carbonates (CO3 2- ) = carbonate ion

Calcite (CaCO3)Dolomite (CaMg(CO3)2

found together in sedimentary rock limestone, Main ingredient to cement, roads & building stones

Mineral groups

Calcium/magnesiumCarbonate, forms dolostone

Forms limestone

HalidesHalite (NaCl)-> common table salt

SulfatesGypsum (CaSO4-H2O)-> calcium sulfate + water, main ingredient of

plaster & other building materialsOxides

Hematite (Fe2O3)-> mined for iron, steel

Mineral groups

Important Nonsilicate Minerals

Ice (H2O)-> solid form of water

RocksRocks Three major types of Three major types of rockrock

Rock cycle and the three basic rock groups.

From Tarbuck, Lutgens: EarthFrom Press, Siever: Understanding Earth, 4th edition

The rock cycle is an interaction between Climate and Plate Tectonic System

RocksRocksIgneous rocks

Extrusive rocks are formed at the surface from lava, rapidly cooling, small crystals, fine-grained texture.

Intrusiverocks are formed from magma in Earth’s crust, slow cooling, large crystals, coarse texture.

Extrusive-Intrusive Sedimentary rocks

DiagenesisAny physical and chemical change that happens to the sediments or the sedimentary rock

How to make a How to make a sedimentary rock.sedimentary rock.

“metamorphism” Lit. “change form”

Transform:

Igneous

Sedimentary

Metamorphic

Metamorphicinto:

“process”

occurs deep

Recall: 3 fundamental rock typesHow to make a metamorphic rock.How to make a metamorphic rock.

Metamorphic rocks

RocksRocks Metamorphic rocks form under 4 main conditions:

Contact Ultra high P Regional high P High P, Low T

• Intro: Chemical and physical structure of Earth

1) The plate tectonic system2) A theory is born3) Early evidence for continental drift

TODAY: Plate Tectonics (Part I)

Read Chapter 3!

EarthEarth’’s layering by chemical s layering by chemical propertiesproperties

Crust

Mantle

Core

Earth’s layer by chemical properties

Lithosphere andLithosphere andasthenosphereasthenosphere

Lithosphere:Crust and uppermost mantle.Broken into 12 plates.Brittle, rigid. 1-100km

Asthenosphere:Lower portion of upper mantle, down to 660kmSoft, deformable, small amount of melting.

3-18

Earth’s layer by physical properties

1) The plate tectonic system1) The plate tectonic system

1. The lithosphere is the outer rigid shell of earth, about 100km thick. It is broken into a dozen large plates that move on the plastic asthenosphere (lower part of the upper mantle)

2. The lithosphere is created at mid-ocean spreading centers and subducts when converging with another plate.

3. The driving force of this movement are convection currents in the asthenosphere.

Fig. 3.10

1) The plate tectonic system1) The plate tectonic system

Convection

PLATEPLATETECTONICSTECTONICS 1) Overview1) Overview1) The plate tectonic system1) The plate tectonic system

Compare with Fig. 3-14