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PowerPoint PresentationPowerPoint PresentationStan Hatfield . Stan Hatfield . Southwestern Southwestern

Illinois CollegeIllinois College

Ken Pinzke . Ken Pinzke . Southwestern Illinois Southwestern Illinois CollegeCollege

Charles Henderson . Charles Henderson . University of University of CalgaryCalgary

Tark Hamilton. Tark Hamilton. Camosun CollegeCamosun College

Chapter 7Chapter 7

Metamorphism Metamorphism and Metamorphic and Metamorphic

RocksRocks

Metamorphosed Olympic Metamorphosed Olympic Spirit HaircutSpirit Haircut

Folded Proterozoic GneissesFolded Proterozoic Gneisses: : (~1.1 Ga) (~1.1 Ga) Barrie, OntarioBarrie, Ontario

MetamorphismMetamorphism The The solid state recrystallizationsolid state recrystallization of one of one

rock into another by a change in rock into another by a change in conditions unlike those in which it conditions unlike those in which it originally formed.originally formed.

Changing conditions include: Changing conditions include: TemperatureTemperature, , PressurePressure, , StressStress and and Chemical CompositionChemical Composition including fluids including fluids like H20 & CO2like H20 & CO2

Metamorphic rocks are produced fromMetamorphic rocks are produced from Igneous rocksIgneous rocks Sedimentary rocksSedimentary rocks Other metamorphic rocksOther metamorphic rocks

ParagneissParagneissS. GreenlandS. Greenland

Gneisses are Gneisses are coarsely crystallinecoarsely crystalline

They have They have separate bands of separate bands of maficmafic and and felsicfelsic mineralsminerals

They are formed They are formed by by regional regional “dynamo-thermal”“dynamo-thermal” metamorphism metamorphism under collisional under collisional orogensorogens

Agents ofAgents of MetamorphiMetamorphi

sm:sm:

Hydrostatic Hydrostatic PressurePressure

Differential Differential StressStress

Agents of MetamorphismAgents of Metamorphism

Confining versus directed pressure. Development of preferred orientations.

Shear flatteningor rotation

Stretched Pebble Stretched Pebble ConglomerateConglomerate

Grade of Metamorphism & T°C Grade of Metamorphism & T°C GradientGradient

Minerals Formed in Minerals Formed in MetamorphismMetamorphism

Micas: Chlorite, Chloritoid, TalcMicas: Chlorite, Chloritoid, Talc Amphiboles: Tremolite, Actinolite, Amphiboles: Tremolite, Actinolite,

Glaucophane, RiebeckiteGlaucophane, Riebeckite Pyroxenes: Jadeite, RhodonitePyroxenes: Jadeite, Rhodonite Garnet: Almandine, Grossular, SpessartiteGarnet: Almandine, Grossular, Spessartite Aluminosilicates: Andalusite, Kyanite, Aluminosilicates: Andalusite, Kyanite,

SillimaniteSillimanite Others: Analcite, Cordierite, Corundum, Others: Analcite, Cordierite, Corundum,

Staurolite, ZeolitesStaurolite, Zeolites

Al-Geobarometers, Fe-Mg GeothermometersAl-Geobarometers, Fe-Mg Geothermometers

Index Minerals & Grade for Index Minerals & Grade for Pelitic RocksPelitic Rocks

Types of Metamorphism vs T°C Types of Metamorphism vs T°C GradientGradient

BurialMetamorphismAlters Volcanics

Zeolite Facies:

Zeolites, Chlorite,Albite, Calcite

ContactMetamorphism

BakesSediments

Cut by intrusionOr overlying

Skarn Deposits:Cu/Fe, W

Contact MetamorphismContact Metamorphism Clay + heat = Clay + heat = hornfelshornfels (nonfoliated rock (nonfoliated rock with mica and amphibole)with mica and amphibole)

Sometimes large metamorphic minerals Sometimes large metamorphic minerals impart a spotted appearance = impart a spotted appearance = porphyroblasticporphyroblastic

Quartzite and Marble often (not always) Quartzite and Marble often (not always) form by contact metamorphism from form by contact metamorphism from sandstone and limestone respectivelysandstone and limestone respectively

Hornfels is named for the highest Hornfels is named for the highest Temperature metamorphic mineral it Temperature metamorphic mineral it contains : Chlorite, Cordierite, contains : Chlorite, Cordierite, Pyroxene…Pyroxene…

Metamorphic Environments Metamorphic Environments & Rocks& Rocks

ContactMetamorphism

CordieritePorphyroblasts

In Shale

Baked to Hornfels

Contact (Thermal) Contact (Thermal) Metamorphism:Metamorphism:

Shallow in Crust, dT>dP, Baking near Shallow in Crust, dT>dP, Baking near IntrusionsIntrusions

High Grade RegionalMetamorphism

Convergent Margins

Orogenic Belts:Himalayas, Grenville,

Appalachians

Progressive Regional Metamorphism Progressive Regional Metamorphism of Pelitesof Pelites

Development of Foliation Development of Foliation through Shearthrough Shear

DynamicMetamorphism

Slaty CleavageDevelopedBy shear

Leads to newFoliation

Directions

Prograde Metamorphism of Prograde Metamorphism of BasaltBasalt

With Normal Geothermal With Normal Geothermal GradientsGradients

Low Medium High

Upper Limit of Regional Upper Limit of Regional MetamorphismMetamorphism

Migmatites:

Partial MeltingOf Low T°C

Felsic MineralsProduces

Granitic Melt&

ResidualRefractory

Mafic Minerals

Special Low dt/dP Special Low dt/dP Subduction ZoneSubduction Zone

Metamorphism of Basalt & Metamorphism of Basalt & GabbroGabbro

Glaucophane Na-Fe Amphibole Omphacite & Jadeite > 100 km

Facies for Pelitic & Basaltic Facies for Pelitic & Basaltic RocksRocks

Metamorphic Facies & Metamorphic Facies & Tectonic SettingsTectonic Settings

Dynamic Metamorphism: Dynamic Metamorphism: Strain >>T,PStrain >>T,P

Shear ~1 Earthquake/Shallow Faults Many Quakes/Deep Faults

Breccia Mylonite

Geographic Locations of Geographic Locations of MetamorphicsMetamorphics

Ancient Continental Shields

ConvergentMargins

AncientContinental

Shields:

Acasta Gneiss4.03 Ga

Canadian Shield

Slave Province

NWT

Impact Metamorphism 49,000 Years Ago 1.186 Km across

Sudbury Impact Basin 1.85 Ga, Deformed in Grenville

Ni, Cu, PGEDiscovered

1883

ConstructionOf CPR

Proterozoic Sudbury Impact Basin (1.85 Ga)Cuts Archean Gneisses (2.65 Ga)