![Page 1: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/1.jpg)
Metamorphic Rocks
![Page 2: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/2.jpg)
What is metamorphic?
• These rocks were at one time either sedimentary or igneous. (The parent rocks)
• A change must occur to be classified as metamorphic.
• Changes can be in texture, minerals, or chemical composition
![Page 3: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/3.jpg)
How do rocks metamorphose?
• From the partial or complete recrystallization of minerals in the rocks over long periods of time
• Rocks remain essentially solid during metamorphism
• Factors causing it can be temperature, pressure, chemistry
![Page 4: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/4.jpg)
1) Temperature
• Low end 100 – 200 degrees C (before?)
• High end 700 – 800 degrees C (after?)
• Where does the heat come from?
• Geo-thermal gradient– as you go deeper into earth’s crust the temperature increases.
• Plutonism – rocks close to an igneous pluton can be raised to near melting.
![Page 5: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/5.jpg)
![Page 6: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/6.jpg)
Effects of temperature
• Causes minerals to react or breakdown into more stable “high temperature minerals”
• Example: Amphibole = pyroxene + quartz + water. Note with bowen’s reaction series that pyroxene is more stable at high temp.
![Page 7: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/7.jpg)
2) Pressure• Where does increased pressure come
from?
• Confining pressure – equal in all directions and all rocks subject to this. Obviously increases with depth.
• Directed Stress – not equal in all directions. (often associated with mountain building forces)
![Page 8: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/8.jpg)
Effects of pressure
• Increased confining pressure favors denser minerals. A common one being Garnet.
![Page 9: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/9.jpg)
• Also evident in metamorphosed sedimentary rocks such as sandstone is the tendency for the rocks texture to become more compact. (fig. 7.3 p.106)
![Page 10: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/10.jpg)
Directed Stress Textures
• A) Slaty Cleavage – platy minerals such as clays or micas will tend to align parallel to each other. Results is “rock cleavage”. Example is slate (metamorphosed shale)
• “low grade metamorphism”
![Page 11: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/11.jpg)
Slate road cut in BC
![Page 12: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/12.jpg)
Directed Stress Textures
• B) Schistosity – Temperatures increase even more, crystals grow coarser (larger) and elongated.
• Example mica schist
• “intermediate grade metamorphism”
![Page 13: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/13.jpg)
![Page 14: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/14.jpg)
Foliation
• Both A and B are examples of foliation. Do not confuse this with bedding!
• Both are textural
• Can sometimes be termed lineation especially for needle shaped minerals like amphiboles.
![Page 15: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/15.jpg)
![Page 16: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/16.jpg)
Gneiss (pronounced “nice”)
• “High grade metamorphism” – highest temperature and pressure.
• Re-crystallized minerals separate into bands of differing composition.
• Usually light (quartz) and dark (ferromagnesian)
![Page 17: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/17.jpg)
• A type of foliation but clearly a compositional difference in the layers.
![Page 18: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/18.jpg)
3) Chemistry
• Gases or liquids passing through rock can react with existing minerals.
• =Metasomatism
![Page 19: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/19.jpg)
Fig. 9.3
![Page 20: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/20.jpg)
Types of Metamorphism
• RegionalRegional
• ContactContact
• SeafloorSeafloor
• BurialBurial
• Shock (impact)Shock (impact)
![Page 21: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/21.jpg)
Types of Regional Metamorphism
Widespread changes in temperature and pressure bring about changes in rocks due to tectonic forces.
![Page 22: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/22.jpg)
Types of Contact Metamorphism
Intrusion of magma against colder rocks. Affected area is proportional to the size and temperature of the intrusion, but is always only a local phenomenon.
![Page 23: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/23.jpg)
Types of Seafloor Metamorphism
Changes in rocks at the Mid-ocean ridge associated with chemical reactions promoted by the infiltration of heated seawater
![Page 24: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/24.jpg)
Types of Impact Metamorphism
Changes due to rapid increase in pressure (localized only )
![Page 25: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/25.jpg)
![Page 26: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/26.jpg)
![Page 27: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/27.jpg)
Slate (parent rock = shale)
• Individual mica crystals too small to be seen
• Slatey cleavage
• More dense and more cleavage than shale.
![Page 28: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/28.jpg)
Phyllite
• Mica crystals become visible, but still fine grained texture overall.
• Continues with slatey cleavage
![Page 29: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/29.jpg)
Schist
• Growth of elongated larger crystals leads to schistosity.
![Page 30: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/30.jpg)
Gneiss
• Compositionally layered rock may form from continued metamorphism of a schist.
• Or this gneissic texture may be formed from strong metamorphism of granite.
![Page 31: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/31.jpg)
• Naming of the foliated rocks is purely based on degree of metamorphism and not composition.
• You can use mineral names to be more specific such as
• “garnet-biotite schist”
• “granitic gneiss” if the composition is that of granite (quartz, feldspar, amphibole)
![Page 32: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/32.jpg)
Non-Foliated
• Quartzite (Parent = Sandstone)
![Page 33: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/33.jpg)
Marble (parent = limestone)
• Will fizz with acid
• If linear features are present then they would have been there with the parent, and not as a result of metamorphism.
![Page 34: Metamorphic Rocks. What is metamorphic? These rocks were at one time either sedimentary or igneous. (The parent rocks) A change must occur to be classified](https://reader036.vdocuments.mx/reader036/viewer/2022062712/56649cb75503460f9497c607/html5/thumbnails/34.jpg)
Begin Lab
• Identify the rocks in your lab ID table
• Answer questions from the lab manual on the back of the ID table.