chaotic melange formed by subduction of oceanic crust fig. 17.11

Chaotic melange formed by subduction of oceanic crust

Fig. 17.11

Gabbro Basalt

Eclogite

Increasing metamorphic grade

Hvilke endringer skjer i en bergart under metamorfose ?

• Teksturelle endringer

• Mineralogiske endringer

• Strukturelle endringer

• Kjemiske endringer

Fig. 7.7

Progressive Metamorphism

Fig. 7.8

Controlling factors during metamorphism

• Temperature

• Pressure / stress

• Fluids

How do pressure and temperture vary in the lithosphere ?

Fig. 7.14Metamorphic Facies

Chaotic melange formed by subduction of oceanic crust

Fig. 17.11

Fig. B7.2

Marble

Limestones

Metam

orphism

Quartzite

Sandstone

Fig. 7.3A

Granite

Fig. 7.3B

Gneiss

Uniform and Differential Stress

Fig. 7.3

Fig. 7.4

Flattened conglomerate

Fig. 7.3

Granite Gneiss

Fig. 7.5

Foliation through a microscope

Fig. 7.6C

Slaty metamorphic cleavage

Fig. 7.6C

Regional stresses

Fig. 7.6

Formation of Slaty Cleavage

Undeformed Granite

Fig. 7.11A

Xenolith

Foliated Gneiss

Fig. 7.11B

The role of fluids

• Fluids fill all pores in a metamorphic rock• Reduces effective stresses on the grain-grain

contacts - thus favouring brittle deformation• Speeds up reactions through

– Increasing transport rates

– Reduce activation energy for mineral reactions(ie. Acts as a catalyst)

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• Prograde metamorphism produces fluidsA= B+H2O

• Retrograde metamorphism consumes fluidsB+H2O=A

Thus dry rocks need external fluid supply to undergo retrogressive metamorphism

•

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Prograde metamorphism I

Contact metamorphic mudstone in Karoo, South Africa

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Types of metamorphism

• Regional metamorphism

• Contact metamorphism

• Burial metamorphism

• Hydrothermal metamorphism

• Shock metamorphism

Plate Setting and Metamorphism

Fig. 7.16

Subduction and

Copper-rich Mineral Deposits

Fig. 7.17

Regional Metamorphism

and Metamorphic Zones in the

Scottish Highlands

Fig. 7.13b

Copyright 2000, John Wiley and Sons, Inc, all rights reserved

Fig. 7.13A

Copyright 2000, J, Wiley and Sons, Inc, all rights reserved

Regional Metamorphic

Zones, Michigan

Contact Metamorphism adjacentto a Granite Intrusion

Fig. 7.12

Fig. 7.151 centimeter

Metasomatically altered Marble

Fig. B7.5 Submarine hot springs