metamorphism and end of sed rocks with notes

May underlie several adjacent states Igneous Rocks Contact Metamorphic Rocks Re gio nal M etamorp hic rocks... occur without the rock melting rocks that melt are igneous... Factors influ

Metamorphism and Metamorphic Rocks

Daily Question

Correctly place the following

statements in the Venn Diagram.

1 Occurs at divergent boundaries

2 Occurs at convergent boundaries

3 Forms as a result of melting (magma)

4 Temperature is an agent

5 Pressure is an agent

6 Generates foliated rocks

7 Forms as a result of being near an intrusion of magma

8 Found in mountain belts

9 May have been originally been a metamorphic rock

10 Form at temperatures above 200 o C

11 May underlie several adjacent states

Igneous Rocks

Contact Metamorphic Rocks

Re gio nal

M etamorp hic rocks

and physical changes that occur in solid

rocks.

Occurs at depths greater than that of

lithification (Diagenesis).

occur without the rock melting (rocks that melt are igneous).

Factors influencing

Metamorphism

Temperature

• below about 150 o C, most minerals are stable (little or no metamorphism)

• above 150 o C, reaction rate increases as temperature increases, new minerals begin to form

• above 600 o C, some minerals begin to melt (transition to igneous rocks)

• Temperature a function of depth within the Earth and the presence of a magma

Factors influencing

Metamorphism

Pressure

• as pressure increases, pore spaces reduced and density increases,

pore fluids are expelled

• Minerals recrystallize and begin to realign

Differential stress

• pressure is greater in one direction than in another

Temperature, Pressure and

Rock Type

Factors influencing Metamorphism

Pore fluids (water and carbon dioxide)

• as pressure increases, pore fluids are

expelled

• Pore fluids increase the rate of metamorphic

reactions by:

• storing ions involved in reactions

• moving ions from one place to another

Chemical Fluids from Magmas

• Carry ions from the melt

• Fluids increase the temperature in the rock

Solutions are deposited in fractures and joints

Factors influencing

Metamorphism

Time

• solid state recrystallization is a slow process

• in general, size of minerals increases with

time

Types of Metamorphism

1 Burial Metamorphism

2 Contact Metamorphism

3 Regional Metamorphism

Metamorphism & Plate Tectonics

Types of Metamorphism

Burial Metamorphism

• most common type, occurs where crust is greater

than 5 km thick

Relatively low temperature and pressure

(low grade metamorphism)

Maximum stress vertical, foliation parallel to ground surface

Types of Metamorphism

Contact metamorphism

• Occurs in rocks around a magma body

• High temperature (heat from magma) “bakes” the rock around the magma creating an

alternation

• High temperature & fluid primary agents, little

to no pressure (occurs at shallow depths in the crust)

Contact Metamorphism

Contact Metamorphism

Types of Metamorphism

Regional metamorphism

• Large scale – large volume of rock is affected

• Associated with convergent plate margins and

• Fluids are also present

• Low grade to high grade metamorphism

• Will have zones of contact metamorphism

Regional Metamorphism

Metamorphic Grade

Low Grade Metamorphism

Example: Slate

• Rocks become more dense and compact

• forms at low temperature and pressure

• microscopic crystals

• dull luster

• clay and mica minerals

• foliated

Low Grade - Slate

Metamorphic Grade

Intermediate Grade –

Phyllite

Metamorphic Grade

High Grade Metamorphism

High Grade - Schist

Metamorphic Grade

High Grade Metamorphism

High Grade - Gneiss

Rock Cycle

Regional Revisited

Slate Phyllite Schist, Gneiss Magma