Lesson 6:Metamorphic Rocks Flashcards
This happen due to the rock being in a condition different from
when it was formed – in most cases, this means higher temperatures
and pressures.
Metamorphism
This rock has the same over-all chemical composition as its parent rock* but may have different minerals and texture.
Metamorphic Rock
The rock before metamorphism happens.
Parent Rock
Metamorphic rocks are not normally considered as parent rock even though they can be metamorphosed. Only _________ rocks are considered as parent rocks
Igneous and Sedimentary
the parent rock of slate and schist
Mudstone
Controls what kind of metamorphism may take place.
Temperature
It is a function of temperature
Mineral stability
What factors causes a temperature change?
Pressure change and water availability
these are minerals that have the same composition as the mineral it crystallized from but different in crystal structure.
Polymorphs
Affects the texture of the resulting metamorphic rock.
It may also cause metamorphic rock’s foliation
Pressure
Facilitates ion transfer and may make metamorphic process go faster.
Water
Same pressure from all directions (pressure is also
applied in directions perpendicular to the page)
Equal confining pressure
Pressure from sides is higher than pressure at top and
bottom (pressure is also applied in directions perpendicular to the page)
Directed pressure
Pressure pushes one side in one direction and the other side in the opposite direction (like when your hands rub each other and the particle is
in between your palms)
Shear stress
A lot of _____ is needed for metamorphic process to happen
time
estimates of new mineral growths are around ____every million years.
1 mm
DIRECTED PRESSURE or SHEAR STRESS is needed in
the environment to form this kind of rock.
Foliated Metamorphic Rock
No directed pressure environment or
environment with little pressure (such as near surface)
Non-Foliated Metamorphic Rock
“layering” or “banding” in metamorphic rocks causing
“sheet-like” structure. Not necessarily seen as physical layers or bands always by the naked eye but show up as weakness planes of the rocks.
Foliation
These rocks do not show foliation even if they are formed in an environment with directed pressure
Quartzite and marble
If a rock is squeezed (directed pressure), it may deform and texture will change such that the minerals seem _______ along an axis _______ to the bigger stress/squeeze.
elongated, perpendicular
It can cause new minerals
to form and their growth will be along the axis perpendicular to the
direction of stress/squeeze.
Heat
Factors contributing to foliation
- Pressure (may include temperature change)
* Pressure, heat, and formation of new minerals
biggest contributor of foliation.
Minerals growing and aligning to a certain direction(perpendicular to the biggest stress)
Foliated metamorphic rocks can be classified on
type of foliated texture it has ,
grade of metamorphism
texture of slate rock
Slaty
texture of phyllite rock
Phyllitic
texture of Schist rock
Schistose
texture of Gneiss rock
Gneissic
From low-grade metamorphism of shale
slate rock
Property of slate rocks that causes it to break into flat sheets
Slaty cleavage
Slate rock’s Microscopic clay and mica crystals have grown and aligned perpendicular to the
largest stress.
Similar to slate but heated to a higher temperature
Phyllite
Phyllite has larger mica crystals than in slate rocks but still barely visible to the eye as ________
sheen on the surface
Phyllite rocks form in ______layers
wavy / silky / crenulated
Created in high enough temperatures forming mica big enough to be seen by the naked eye, possibly with quartz, feldspar, etc. visible.
Schist
The temperature of schist is in between ____ and ____
Phyllite and Gneiss
its Minerals have been separated into distinct bands.
Little to no mica (temperature is too high for mica to remain)
Gneiss
Example of rocks that gneiss metamorphosised from
mudstone, sandstone, granite
Form in areas where pressure is just confining pressure (same
pressure from all sides) or low-pressure conditions.
Non-foliatic metamorphic rocks
Non-foliatic metamorphic rocks are not _________ and the heat is coming from _________
buried deep enough, a nearby body of magma.
metamorphosed limestone
Marble
metamorphosed sandstone
Quartzite
metamorphosed fine grained rocks or volcanic rock
Hornfels
basalt at 150 degree celcius metamorphosis into
chlorite schist
• A rock that was partially melted and is metamorphosed – that is
containing both igneous and metamorphic rock.
Migmatite
