(MODULE 5) METAMORPHIC ROCK Flashcards
Rocks that are deeply buried melt (or partially melt) to form magma when temperatures are high enough. What happens to rocks that are deeply buried but are not hot enough to melt?
they undergo metamorphism
___ refers to changes to rocks that take place in Earth’s interior. The changes may be new textures, new mineral assemblages, or both.
metamorphism
transformations in metamorphism occur in the ___ state.
solid
metamorphism can be interpreted as toasting a slice of bread. how so?
when the bread is toasted, it turns into toast. same material, different texture and composition.
the same goes with parent rock being exposed to heat and pressure to turn into metamorphic rock; same material, different texture and composition.
The minerals present in a rock indicate its ___.
___ rocks formed under relatively cool temperatures and ___ rocks at high temperatures, whereas ___ rocks recrystallized at around the middle of the range of metamorphic temperatures.
- metamorphic grade
- low-grade
- high-grade
- medium-grade
Factors controlling the characteristics of metamorphic rocks
1.
2.
3.
4.
- composition of parent rock
- temperature and pressure
- tectonic forces
- fluids
heat, necessary for metamorphic reactions, comes primarily from __.
geothermal energy
Usually, the deeper a rock is beneath the surface, the hotter it will be. The particular temperature for rock at a given depth depends on the ___.
geothermal gradient
a mineral is said to be ___ if, given enough time, it doesn’t react with another substance or convert to a new mineral or substance.
stable
minerals stable at higher temperatures are ___ because it allows greater vibration of atoms
less dense
the rate at which temperature increases with increasing depth beneath the surface
geothermal gradient
the pressure gradient (increase in lithostatic pressure with depth) is approximately ___.
1 kilobar per each 3.3 kilometers of burial in crustal rock.
pressure applied equally on all surfaces
confining pressure or lithostatic pressure
minerals formed under high-pressure conditions tend to occupy ___ than its polymorphs.
less space
if both temperature and pressure increase, then whichever is ___ will have its effects shown on the rock.
greater than the other (e.g. more pressure than temperature)
force applied on a rock that is strong in some directions and weak in others is called ___
differential stress
the type of metamorphism which occurs from shearing
dynamic metamorphism
differential stress that squeezes a rock as shown here is termed ___.
compressive stress
where is water for metamorphosis found?
it can be found in fractures, hydrated minerals such as clay and mica, and pore spaces.
When a rock has a planar texture, it is said to be ___.
foliated
the process in which a platy material like clay or mica undergoes differential stress and grows parallel to the direction of sheering
foliation
variations of foliation
1.
2.
3.
- slaty
- schistose
- gneissic
If the rock splits easily along nearly flat and parallel planes, we say the rock is ___
slaty or possesses slaty cleavage
Rocks that split into thin slabs when hit with a hammer exhibit rock cleavage.
rock cleavage is best displayed in slates that exhibit an excellent splitting property called ___.
slaty cleavage
If visible materials have grown parallel to a plane from differential stress, the rock is ___.
schistose
if the rock has distinct bands and layers, the rock is ___.
gneissic
___ rocks develop in environments where deformation is minimal.
non-foliated
these non-foliated rock sometimes contain large grains called ___ which are surrounded by a fine-grained matrix of other minerals.
porphyroblasts
Foliated metamorphic rock (listed from low-grade to high-grade)
- slate
- phyllite
- schist
- gneiss
Fine-grained foliated rock composed of minute chlorite and mica flakes
slate
___ represents a degree of metamorphism between slate and schist. it is distinguished from slate by its glossy sheen and wavy surface
phyllite
Medium- to coarse-grained metamorphic rocks in which platy minerals are dominant
schists
nonfoliaited metamorphic rock (list them down)
- marble
- quartzite
- hornfels
nonfoliated rock formed through the metamorphism of limestone or dolostone
marble
very hard nonfoliated rock formed from quartz sandstone. it can be taxing on construction equipment
quartzite
a fine-grained nonfoliated rock with varying mineral composition unlike marble and quartzite.
hornfels
When a rock becomes buried to increasingly greater depths, it is subjected to increasingly greater temperatures and pressures and will undergo ___ wherein it recrystallizes into a higher-grade rock.
prograde metamorphism
also known as thermal metamorphism, this type of metamorphism is one in which high temperature is the dominant factor.
the parent rock is baked into a metamorphic rock.
contact metamorphism
zone of contact metamorphism
aureole
the type of metamorphism typically associated with mountain building, where large segments of Earth’s crust are intensely deformed by the collision of two continental crust blocks.
regional metamorphism
When hot, ion-rich water circulates through pore spaces or fractures in rock, a chemical alteration called ___ may occur.
hydrothermal metamorphism
explain the hydrothermal processes and water’s role in them.
- during metamorphism…
- during metasomatism…
- when hydrothermal rock…
during metamorphism, water transports ions between grains in a rock and/or incorporated into crystal structures.
during metasomatism, water brings ions from outside the rock and are added to the rock during metamorphism.
when hydrothermal rock crystallize in a fracture to form a vein, water passes through the cracks in rock and precipitates minerals on the walls of cracks and pore spaces.
mineral formed when oxygen in the atmosphere bonds with iron to form iron oxide
hematite
