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Classification and Facies Wikipedia. Today Updates: Not today Lecture outline: - Rock classification - Facies.

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Presentation on theme: "Classification and Facies Wikipedia. Today Updates: Not today Lecture outline: - Rock classification - Facies."— Presentation transcript:

1 Classification and Facies Wikipedia

2 Today Updates: Not today Lecture outline: - Rock classification - Facies

3 Prograde Metamorphism Normally progress through series of mineral assemblages, for example:Normally progress through series of mineral assemblages, for example: 1.epidote, chlorite, andalusite, muscovite, quartz, k-spar, and albite 2.sillimanite, plagioclase, cordierite, muscovite, quartz and k-spar 3.sillimanite, plagioclase, cordierite, quartz, and k-spar

4 Prograde Retrograde Prograde Metamorphism

5 Retrograde Metamorphism Prograde Retrograde 320petrology/opticalmin/chlorite.htm

6 Common Prograde Sequence Index minerals make zones: s s Chlorite zone. Pelitic rocks are slates or phyllites and typically contain chlorite, muscovite, quartz and albite s s Biotite zone. Slates give way to phyllites and schists, with biotite, chlorite, muscovite, quartz, and albite s s Garnet zone. Schists with conspicuous red almandine garnet, usually with biotite, chlorite, muscovite, quartz, and albite or oligoclase s s Staurolite zone. Schists with staurolite, biotite, muscovite, quartz, garnet, and plagioclase. Some chlorite may persist s s Kyanite zone. Schists with kyanite, biotite, muscovite, quartz, plagioclase, and usually garnet and staurolite s s Sillimanite zone. Schists and gneisses with sillimanite, biotite, muscovite, quartz, plagioclase, garnet, and perhaps staurolite. Some kyanite may also be present (although kyanite and sillimanite are both polymorphs of Al 2 SiO 5 )

7 Sequence of indicator mineralsChlorite Biotite Garnet Staurolite Kyanite Sillimanite

8 Types of Protolith Six chemically based-groups to start with 1. Ultramafic - very high Mg, Fe, Ni, Cr 2. Mafic - high Fe, Mg, and Ca 3. Shales (pelitic) - high Al, K, Si 4. Carbonates- high Ca, Mg, CO 2 5. Quartz - nearly pure SiO Quartzo-feldspathic - high Si, Na, K, Al

9 A Classification of Metamorphic Rocks

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11 Compositional Classification ParentMetamorphic rock Clay-rich sedimentpelite Sand-rich sedimentpsammite Clay-sand mixsemi-pelite Quartz sandquartzite Marl (limy mud)metamarls-silicate/calcareous Limestonemarble Basaltmetabasite

12 a b Pelite protolith: Foliated Metamorphic Rocks -- low grade

13 Pelite protolith: Foliated Metamorphic Rocks --middle grade

14 Pelite protolith: Foliated Metamorphic Rocks -- high grade

15 Non-Foliated Rocks

16 Specific Rock Types

17 Skarn: carbonate + contact metamorphism + Si added (metasomatism). Minerals: grossular, epidote, tremolite, wollastonite, diopside Granulite: high-grade rock from pelitic, mafic, or quartzo-feldspathic protolith, few OH-bearing minerals. few OH-bearing minerals. Specific Rock Types

18 rocky/BigornMtS/1K_DSC_1687.jpg

19 Protolith = mafic rock or graywacke (dirty sst): Greenschist: low-grade, contains chlorite, actinolite, epidote (all green), and albite. Amphibolite: mid-grade, dominated by hornblende + plagioclase. Specific Rock Types

20 Serpentinite: ultramafic rock, low-grade metamorphosed. Blueschist: high-P, blue by glaucophane--amphibole (mafic rock) or blue by kyanite (pelite). Eclogite: green + red due to clinopyroxene and garnet (omphacite + pyrope). (basalt) Specific Rock Types

21 Metamorphic Facies Wikipedia

22 Prograde Sequence and Facies Index minerals make zones, but COMPOSITION DEPENDENT Change in composition, means change in minerals occurring s Chlorite zone. s Biotite zone. s Garnet zone. s Staurolite zone. s Kyanite zone. s s Sillimanite zone. => Facies is better to compare different metamorphic rocks F Chlorite F Biotite F Cordierite F Andalusite F Sillimanite

23 Prefix and mineral texture

24 High Strain Rocks

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26 Why do we care about metamorphic rocks?


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