Chapter 10: Metamorphism: New Rocks from Old La Pietra by Michelangelo, carved from Carrera marble © 2012 John Wiley & Sons, Inc. All rights reserved

Chapter 10: Metamorphism: New Rocks from Old

La Pietra by Michelangelo, carved from Carrera marble

© 2012 John Wiley & Sons, Inc. All rights reserved.

Learning ObjectivesWhat is metamorphism?• Describe the conditions necessary for

metamorphism.

Metamorphic rock• Identify the metamorphic products of shale

and basalt.

Metamorphic processes• Describe different types of metamorphism

and their tectonic settings.

Metamorphic facies• Describe metamorphic zones and the types

of facies they produce.© 2012 John Wiley & Sons, Inc. All rights reserved.

What Is Metamorphism?

Metamorphism•The mineralogical, textural, chemical, and structural changes that occur in rocks •A result of exposure to elevated temperatures and/or pressure


What Is Metamorphism?The Limits of Metamorphism

Low-grade•Rocks metamorphosed under temperature and pressure conditions up to 400°C and 400 MPaHigh-grade•Rocks metamorphosed under temperature and pressure conditions higher than about 400°C and 400 MPa

Figure 10.2 Temperature and pressure conditions for metamorphism


Temperature and pressure

Figure 10.3 From shale to gneiss


What Is Metamorphism?Factors Influencing Metamorphism

What a Geologist Sees—At the roadside



Pore fluid•Pore fluids influence metamorphism.•Pores are open spaces.

Figure 10.4 Quartz vein


Figure 10.5 Effects of uniform and differential stress


Stress•Foliation• A planar arrangement of textural features in

a metamorphic rock• Gives rock a layered or banded appearance


Foliation•Slaty cleavage

• Foliation in low-grade metamorphic rocks that causes such rock to break into flat, plate like fragments

•Schistosity• Foliation in coarse-

grained metamorphic rocks

Figure 10.6 Foliation under the microscope




Figure 10.7 Slaty cleavage


Metamorphism and Billiards


• Duration• Rate of metamorphism



Metamorphic RockRock with Foliation

Slate•A very fine-grained metamorphic rock with slaty cleavage; the metamorphic product of shalePhyllite•A fine-grained metamorphic rock with pronounced foliation, produced by further metamorphism of slate


Metamorphic Rock


Figure 10.8 Schistosity versus slaty cleavage

Metamorphic Rock

Figure 10.9 Metamorphism of basalt


Metamorphic Rock

Figure 10.9 Metamorphism of basalt


Quartzite•The product formed by recrystallization of sandstone

Metamorphic RockRock Without Foliation

Figure 10.10 Nonfoliated metamorphic rocks: Quartzite



Marble•The product formed by recrystallization of limestone

Figure 10.10 Nonfoliated metamorphic rocks: Marble

Metamorphic RockRock Without Foliation

Metamorphic ProcessesProcesses that cause changes in texture and mineral assemblages in metamorphic rock•Mechanical deformation•Grinding, crushing, bending and fracturing

Figure 10.11 Mechanical deformation


Metamorphic ProcessesProcesses that cause changes in texture and mineral assemblages in metamorphic rock•Chemical recrystallization

• Changes in mineral composition, growth of new minerals, recrystallization of old minerals, and changes in amount of pore fluid

• Typically caused by heating and squeezing of rock

Figure 10.12 Contact metamorphic


Metamorphic ProcessesTypes of Metamorphism

Regional metamorphism•Metamorphism of an extensive area of the crust•Associated with plate convergence, collision, and subduction

Other types of metamorphism occasionally occur in geologic settings where high temperature and/or elevated pressure or stress exists.

Figure 10.13 Tectonics and metamorphism


• Contact metamorphism• Rocks are heated and

chemically changed adjacent to an intruded body of hot magma.

• Burial metamorphism• Occurs after

diagenesis; is a result of the burial of sediments in deep sedimentary basins.

Figure 10.14 Quick pressure, slow heat



Figure 10.15 Instantaneous metamorphism



Metasomatism•The process whereby the chemical composition of a rock is altered by the addition or removal of material by solution in fluids:• Frequently water or

carbon dioxide

Figure 10.16 Metasomatism


Metamorphic ProcessesMetasomatism

Metamorphic Facies

Metamorphic facies•The set of metamorphic mineral assemblages •Form in rocks of different compositions •Form under similar temperature and stress conditions

Figure 10.17 Regional metamorphism in Scotland


Metamorphic Facies

Figure 10.18 Metamorphic facies


Critical Thinking

• Compare the concept of metamorphic facies to that of sedimentary facies. In what ways are they similar? In what ways are they different?

• Museum curators obviously can’t shave off pieces from valuable art. How do you think they manage to identify the rocks and minerals?

• Briefly explain how pressure and temperature might change over time in rocks being subjected to contact, burial, and subduction-related regional metamorphism.


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Chapter 10: Metamorphism: New Rocks from Old La Pietra by Michelangelo, carved from Carrera marble © 2012 John Wiley & Sons, Inc. All rights reserved