When i was young
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When I was young!!!. Metamorphic rocks are formed from other rocks Which are changed by heat and pressure. Metamorphic Rocks generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following: Pressure Temperature Mineral Rich Fluids

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When I was young!!!

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When i was young

When I was young!!!


When i was young

Metamorphic rocks are formed from other rocks

Which are changed by heat and pressure


When i was young

  • Metamorphic Rocks

  • generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following:

  • Pressure

  • Temperature

  • Mineral Rich Fluids

  • The type of metamorphic rock is determined by the parent rock, and the P/T conditions.

Metamorphism causes:

Growth of new minerals

Deformation and rotation of mineral grains

Recrystallization of minerals as larger grains


Metamorphic minerals

Metamorphic Minerals

  • Chlorite

  • Talc

  • Graphite

  • Asbestos

  • Kyanite

  • Staurolite

  • Siliminite

  • Corundum


When i was young

Contact Metamorphic Rocks

generated mainly by temperature at the margins of igneous intrusions..


Index minerals

Index Minerals

  • Minerals associated with the grade of metamorphism.


Limestone into marble

Limestone into Marble

  • Texture - granular.

  • Grain size - medium grained; can see interlocking calcite

  • crystals with the naked eye.Hardness - hard, although component mineral is soft (calcite is 3 on Moh's scale of hardness).

  • Colour - variable - pure marble is white but marble exists in a wide variety of colours all the way through to black

  • Mineralogy - calcite.

  • Other features - generally gritty to touch.


Sandstone to limestone

Sandstone to Limestone

Texture - granular.

Grain size - medium grained; can see interlocking quartz crystals with the naked eye.

Hardness - hard.

Colour - variable - pure quartzite is white but quartzite exists in a wide variety of colours.

Mineralogy - quartz.

Other features - generally gritty to touch.

  • Quartzite


Mudstone hornfels

Mudstone - hornfels

  • Texture - granular.

  • Grain size - medium grained; can see interlocking crystals with the naked eye.

  • Hardness - hard.

  • Colour – greys - blacks

  • Mineralogy – no specific composition.

  • Other features - generally gritty to touch.


Regional metamorphism

Regional Metamorphism


Foliation

Foliation

  • Foliation is formed by the orientation in the rocks.

  • Foliation is seen as banding in the rocks.


Metamorphic grades

Metamorphic Grades


Slaty

Slaty

  • Texture - foliated, foliation on a mm scale.

  • Grain size - very fine-grained; crystals not visible to the naked eye.

  • Hardness - hard and brittle.Colour - variable - black, shades of blue, green, red, brown and buff.

  • Mineralogy - contains mica minerals (biotote, chlorite, muscovite) which typically impart a sheen on foliation surfaces; can contain cubic pyrite porphyroblasts.


Schistose texture

Schistose texture

  • Texture - foliated, foliation on mm to cm scale.Grain size - fine to medium grained; can often see crystals with the naked eye.Hardness - generally hard.Colour - variable - often alternating lighter and darker bands, often shiny.Mineralogy - mica minerals (biotite, chlorite, muscovite), quartz and plagioclase often present as monomineralic bands, garnetporphyroblasts common.


Gneiss texture

Gneiss texture

  • Texture - foliated, foliation on a scale of cm or more.

  • Grain size -medium to coarse grained; can see crystals with the naked eye.

  • Hardness - hard.

  • Colour - variable - generally alternating lighter and darker sub-parallel discontinuous bands.

  • Mineralogy - felsic minerals such as feldspar (orthoclase, plagioclase) and quartz generally form the light coloured bands; mafic minerals such as biotite, pyroxene (augite) and amphibole (hornblende) generally form the dark coloured bands; garnet porphyroblasts common.

  • Large banding.

  • Distinct dark and light bending.


Amphibolite

Amphibolite

  • Made mainly of Amphibole.

  • Other minerals hornblende, Plagioclase and Garnet

  • Formed when Basalt undergoes high pressure and temperature.

  • Foliations present


Greenschist

Greenschist

  • Low grade

  • Chlorite, epidote, actinolite.

  • Green in colour.

  • Changes from the original mafic minerals as water reacts with the minerals


Dynamic metamorphism

Dynamic Metamorphism


Mylonite

Mylonite

  • Fine grained rock

  • Thin laminations

  • Large porphyrblasts of garnet and k feldspar during metamorphism.

  • Recrystalised quartz and Mica

  • Banding is called a ribbon texture


Fault breccia

Fault Breccia

  • Cataclastic rock

  • Formed by fault movement

  • Cemented by minerals.


When i was young

a-sedimentary rocksb-contact metamorphic c-burial metamorphic

d-regional metamorphice-igneous rock


What does metamorphis do

What does metamorphis do?

  • High Temperatures – Re-crystallisation of the rocks

  • High Pressure – minerals re-align causing a change in texture


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