WHAT ARE IGNEOUS, METAMORPHIC AND SEDIMENTARY ROCKS?

What is magma? (again)

A hot mix of molten rock, gases and minerals Common Earth elements like O, Si, Al, Fe, Mg,

Ca, K and Na are found in magma SILICA (SiO2) is the most abundant material in

magma. Silica is often found in sand and quartz

Silica content affects the melting temperature of magma. (which influences viscosity)

What is magma? (again)

Magma experiences partial melting because of its heterogeneous composition. (what does this

mean?)

What is magma? (again)

Fractional Crystallization: Different minerals within magma cool and crystallize under different conditions

Crystallization and partial melting have a reverse relationship. The first minerals to crystallize are the last

minerals to melt

1. Igneous rocks

Igneous rocks form from the crystallization (deposition) of magma

Extrusive igneous rock is typically of a fine grain and is formed during quick cooling

Intrusive igneous rock is typically of a coarse grain and is formed during slow cooling periods

Bowen’s Reaction Series

N. L. Bowen, a Canadian geologist modelled a pattern of mineral crystallization

As temperatures begin to cool, some calcium-rich minerals undergo a continuous change over a long temperature interval and become sodium-rich

Some iron-rich minerals undergo discontinuous change. These minerals undergo abrupt changes in crystallization.

Bowen’s reaction series: (p. 114)

Samples: 35, 33, 34, 30, 32, 22 or 23Samples: 35, 33, 34, 30, 32, 22 or 23

Bowen’s reaction series: (p. 114)

Bowen’s reaction series

As more and more materials crystallize out of cooling magma, the remaining rock becomes concentrated with silica.

Quartz is the last mineral to crystallize out (mainly silica)

IF ROCKS CHANGE THEIR CRYSTALLINE STRUCTURE AND CHEMICAL COMPOSITION AS THEY COOL, WHY DOES OLIVINE EXIST FOR US TO SEE?The simple answer is crystal separation

Bowen’s reaction series: Figure 5-6 (p. 104)

Classifying Igneous Rocks

Mafic rock has low silica content and are rich in iron. They contain plagioclase, biotite, amphibole, pyroxene, and olivine; EX. Gabbro

Felsic rock have high silica content and contain quartz and feldspars

Ultramafic rock contains super-low silica and super high iron.

Sample: 38Sample: 38

Classifying Igneous Rocks

Differences between similar samples such as size, shape, grain size and texture may be described by cooling rates of magma

Mineral grains, rather than rock shape, are used for identification. (why?)

Porphyritic texture describes well-formed crystals surrounded by fine grained crystals of the same or differing material

Igneous Rock for Industry

Interlocking grains give strength Some mineral crystals are naturally

resistant to weathering Granite composition may be

aesthetically pleasing

Igneous ‘Veins’

Some metallic elements like gold, silver, lead and copper are not a part of common minerals and behave in a similar way to silica.

They are the last substances to precipitate out of magma during cooling

Minerals Veins

Large-grain minerals containing rare elements like lithium and beryllium

Type of ultramafic rock (low silica, high elemental metal)

Diamonds form in kimberlite

MIR MINE

Pegmatites Kimberlites

Read section 5.1 on pages 112-117

and answer questions: 1-6

Read section 5.2 on pages 118 – 123

and answer questions 1-4

Read section 5.1 on pages 112-117

and answer questions: 1-6

Read section 5.2 on pages 118 – 123

and answer questions 1-4

2. Sedimentary Rocks

Sediment refers to material that is broken down through weathering and transported by erosion, ice and gravity

These fragments of material stick together to form sedimentary rock

Materials within sedimentary rock vary in their resistance to weathering which produces clastic rock (‘broken’ rock)

Sediments Size

Very small particles

Very large particles

Clay Silt Sand Gravel

Pebble

Cobble

Boulder

Deposition and Lithification

Larger materials deposit first in fluids

Transport by ice does not discriminate between particle sizes

Lithification

Pressure from overlying material force sedimentary rock to compact.

Clay and silt do not allow much space for water, but sand and larger particles do.

Water and materials travel through sedimentary rock into the Earth where temperatures increase by 30˚C every kilometer below the surface

At around 4 kilometers below the Earth’s surface cementation may begin to occur

Lithification occurs through Cementation

1. Unique minerals like Calcite or iron oxide grow in-between sediment grains

2. Existing mineral grains grow larger as more of the same mineral becomes available

Bedding

Bedding refers to the horizontal layering of sedimentary rock through erosion and grain size

Graded-bedding refers to bedding that contains coarse and heavy layers near the bottom layers

Cross-bedding refers to layers of sediment that are inclined and represent sedimentary layers that move horizontally along a surface through the action of wind or water

Clastics: Coarse grain

Particles travelling as bed load become rounded and eventually become conglomerate (rounded and coarse grained clastic)

Angular coarse grained clastic is called breccia

Sample: 54Sample: 54

Clastics: Medium Grain

These rock forms usually come from rivers and streams and form sandstone

Stratification tells scientists the direction of fluid movement

High porosity allows water to move through sandstone and can allow oil, natural gas and groundwater reservoirs to form

Sample: 55Sample: 55

Clastics: Fine Grain

Very low porosity that does not allow for movement of fluids

Forms shaleSample: 56Sample: 56

Sedimentary Rock created through Chemical Process

Chemical Minerals that precipitate out of solution during evaporation are called evaporites

Examples; Halite (salt), calcite (calcium carbonate aka old chalk) and gypsum (calcium sulfate)

Samples: 63, 64Samples: 63, 64

Sedimentary Rock created through Biological Process

Organic Rock formed from the remains of living things

Examples; limestone from organic sea shells and bone

Coal from thick layers of plant material

Read section 6.1 on pages

134 - 140 and answer

questions: 3-6

Read section 6.2 on pages 141 – 144 and answer

questions 1-7

Read section 6.1 on pages

134 - 140 and answer

questions: 3-6

Read section 6.2 on pages 141 – 144 and answer

questions 1-7