Rock cycle Flashcards
Definition of the rock cycle
cycle of processes that occur in the Earth’s crust to
create and destroy rocks.
Definition of a rock
a naturally occurring solid mass or aggregate of minerals or
mineraloid matter
Definition of a mineral
‘naturally occurring, inorganic crystalline solids that have a
definite chemical composition. Minerals have characteristic physical
properties’
How are sediment generated
Sediments are generated through weathering
and erosion
How does the lithification of sedimentary rocks occur
- Compaction and cementation
- Sedimentary rock formation
Define a igneous rock
An igneous rock is a rock that has formed
by the cooling and crystallization
(solidification) of molten rock.
________ originates deep
within the Earth’s
lithosphere / upper
mantle due to the melting
of rock and associated
minerals.
________ is the name given to
molten rock when it
reaches the Earth’s
surface from volcanic
activity.
magma
lava
igneous rocks are typically classified by
- rock texture - size of crystals or grains in
the rock, called grain size - composition - type of minerals present
- colour- type of minerals present
Rock texture - mineral crystal size can be affected by
A) the rate of cooling,
B) the original temperature of the
magma, and
C) the crystallization temperature of
the mineral the crystal is composed
of.
Intrusive igneous rocks:
If a large volume of magma cools slowly within the
lithosphere, the crystallized rock is known as a _________
igneous rock or an intrusive igneous rock
Magma cools _______ within the lithosphere, permitting the
growth of mineral crystals to form intrusive igneous rocks
Plutonic
slowly
What does phaneritic texture mean
Visible grains
1 to 5mm
interlocking crystalline texture
Plutonic rocks posses a ________ _________
Phaneritic texture
Extrusive igneous rocks:
Igneous rocks that reach the
Earth’s surface cool, solidify, and
crystallize relatively _______ (e.g.,
at a rate of minutes to months)
and are called extrusive igneous
rocks
quickly
Aphanitic meaning
fine grained texture. crystals are too small to see with the naked eye
extrusive rocks have a ________ texture
aphanitic
What is vesicular texture
If the solidifying
igneous rock contains
gas (e.g., sulfur and
carbon dioxide),
bubbles of entrapped
gas may form holes as
the rock solidifies.
How does volcanic glass occur
rapid cooling, or chilling, prevents the
crystallization of minerals
very rapid cooling forms a natural glass
known as
obsidian
frothed natural glass as a result of
excessive gas in the magma creates
_______ when it cool
pumice
Define equigranular
If all mineral crystals are approximately the same size,
use the term
Define porphyritic rock texture
If the rock has large mineral grains surrounded by a
finer-grained groundmass (i.e., the majority of finer
mineral grains forming the bulk of the rock)
Felsic rocks contain what minerals
Potassium feldspar
Quartz
Plagioclase feldspar(Na-rich)
Biotite
Amphibole
Intermediate rocks contain what minerals
Mainly: Plagioclase feldspar, pyroxene
Smaller amounts of potassium feldspar, quartz, biotite, and amphibole
Mafic rocks contain which minerals
Plagioclase feldspar, pyroxene and a small bit of olivine
the colour of felsic minerals are
light
the colour of mafic minerals are
dark
Which two broad categories do we separate igneous rocks
felsic and mafic
Does Ferromagnesian make mafic minerals dark or not
yes, Ferromagnesian makes mafic dark
Does Ferromagnesian make felsic minerals light
no, non-Ferromagnesian minerals are in felsic rocks
Is granite felsic, intermediate or mafic
Felsic
Is rhyolite felsic, intermediate or mafic
felsic
Is granite or rhyolite an intrusive igneous rock
Granite is intrusive
Rhyolite is extrusive
Where do we find felsic rocks
Continental crust
continental hot spots
Is gabbro phaneritic, or equigranular, aphanitic
Phaneritic
What minerals is gabbro composed of
pyroxene, plagioclase feldspar, and olivine
Which two elements are mafic rocks rich in
Iron and magnesium
Which minerals are not in mafic rocks
Quartz, potassium feldspar, biotite, and amphibole
Where do you find mafic rocks
upper mantle
mid-ocean ridges, ocean hotspots, continental rift zones
What are ultra-mafic rocks composed of
Mainly olivine, pyroxene and small amounts of plagioclase feldspar
Where do we find intermediate rocks
Subduction zone arc volcanoes and plutons beneath them
Mt St Helens, the Andes mountains
What are two types of intermediate igneous rocks
Diorite and andesite
What are two types of mafic rocks
Gabbro and basalt
Do mafic minerals or felsic minerals crystalize first
Mafic minerals crystalize first, then felsic minerals
Give examples of geomorphic processes
This is how sediments are transported
Wind - aeolian, gravity, mass wasting, river currents - fluvial, waves - coastal, ice - glacial
What are the 6 steps for sediments to turn into sedimentary rocks
- exposure(uplift of tectonic plates coming together to form mountains)
- Weathering
- Erosion (transportation)
- processes acting on the sediments as they are moving them (can change the minerology and sorting occurs)
- Deposition (Sediments settle in a basin and layers form
- Compaction and lithification
What is one thing that can cause a mafic rock to not be dark
If it is rich in olivine it will be green
Today, do volcanoes erupt ultra-mafic rocks
nope
What is Bowens reaction series
order of mineral crystallization as the magma cools
Give the Bowens reaction series from first to last
First: olivine, pyroxene, amphibole, biotite, Quartz, Muscovite, K-feldspar :last
Which mineral can crystalize at any temperature
Plagioclase, its crystallization depends on if it is Ca-rich(High temps) or Na-rich(low temps)
Define Phenocrysts
Phenocrysts – form in the magma and are brought up in the magma
Define Xenocrysts/xenoliths
Xenocrysts/xenoliths – didn’t form in the magma, brought along by
the magma
Define bedrock
Rock that is attached to the earths crust
Define outcrop
is an exposure of bedrock to the surface
Describe weathering
- Breakdown of rock due
to physical, biological,
and chemical processes - modifies rocks and the
minerals within them - produces sediment,
small particles of rock
and/or minerals - Sediment can be
transported (moved) to
another location by
water, wind, or ice
this is called erosion
What are sedimentary rocks composed of
sediments or salt that have dried out of a solution - like in salt lakes
What are sediments
particles of rock, minerals, shells, fossilized organic material
is sand a rock or sediment
sediment
grains are loose and unconsolidated
is sandstone a rock or a sediment
rock
grains are bound together by natural cement
At what temperature does the lithification of sediments into sedimentary rock occur
150 - 200 Celsius
Sediments lithify as flat lying beds, what are these called
Strata
This is through the principal of original horizontality
Sedimentary rocks are formed by the consolidation
and lithification of __________ and/or ________ in
solution.
sediments
ions
What can we subdivide sedimentary rocks into
Clastic, biochemical/organic, chemical
silt vs clay
silt feels like finely ground flour, clay is sticky and
you can’t feel any particles.
if you put a tiny bit of the
material on your teeth and rub it gently with your tongue,
silt will feel granular and clay will feel smooth.
What is the rock name of gravel (rounded particles)
Conglomerate
What is the rock name of gravel (angular particles)
Breccia
what is the sediment name of siltsone
silt
What is the sediment name of shale
clay
Order these sedimentary rocks from most coarse to least coarse
Diamictite
siltstone
shale
conglomerate
sandstone
Breccia
Conglomerate
Breccia
Diamictite
Sandstone
Siltstone
Shale
What are the 4 types of sorting to classify clastic rocks
Angular, subangular, subrounded, rounded
What will cause a clastic sedimentary rock to become more sorted(rounded)
The more process it undergoes during its transportation will cause it to be more sorted
What are some examples of biochemical/organic sedimentary rocks
coal, carbonate rocks such as fossiliferous limestone, dolostone, chalk, and coquina
What are the two ways that biochemical/organic sedimentary rocks form
organisms generating mineral matter (Coral)
Fossilized organic matter such as coal
How are biogenic (ie biochemical/organic) sedimentary rocks derived
from hard parts of organisms
-tiny diatoms made of silica
-tiny coccolithophores made of calcite
-sea shells
-coral
-coprolites (fossilized animal poop)
How do chemical sedimentary rocks form
These rocks form through a chemical
process of precipitation of ions out of
solution
How/when do evaporite deposits form
Evaporite deposits form when ions precipitate (form solids) out of
solution in an alkali lake or sea to form rocks composed of minerals
such as gypsum (Ca sulfate) and sylvite (K carbonate KCl)
What are examples of chemical sedimentary rocks
Inorganic limestone, chert, rock gypsum, rock salt
Describe chemical sedimentary rocks that form from hot water
Ions dissolve in hot water of hot
springs, as it cools the ions
precipitate out of solution
* form different rocks depending on
the water chemistry
Sedimentary rocks have specific features and structures that make what possible for geologists to do now
Geologists are able to reconstruct the environment of
deposition and the environmental conditions prevalent at that
time based on this evidence
What are the economic importance of sedimentary rocks
*Reservoirs for oil and gas, and water
*Economic minerals: potash (sylvite), limestone for
cement
*Quarried aggregate or building stone
What is the geological environment of formation for conglomerate
high energy environments such as a stream
What is the geological environment of formation for Sandstone
beaches, rivers, deserts
What is the geological environment of formation for shale
low energy environments
like lakes
What is the geological environment of formation for dolostone
Shallow marine, tropical
What is the geological environment of formation for limestone
shallow marine, tropical
What is the geological environment of formation for potash
hot, dry climate and a restricted marine basin
In what layer of the earths crust does metamorphism occur
lithosphere
What type of process causes metamorphism
plate tectonics
This creates increased pressure and temperature acted on the rocks
Metamorphism can cause the original texture and/or minerology to become ________ and the rock changes
unstable
Which types of rocks can become metamorphic rocks
Igneous
Sedimentary
metamorphic
(all of them)
Which 3 agents drive metamorphism
High temperature
High pressure
Chemically active hot fluids(sometimes)
At what temperature causes metamorphic rocks to change
> 200C drives chemical reactions
How do we see metamorphic rocks on the surface today
- rocks are brought to the surface (or closer to the surface) by plate
tectonic processes - the overlying rocks have been eroded away
Why does chemically active hot fluids cause metamorphism
Reactive hot fluids (e.g., H
enhance the metamorphic process.
Such fluids become more reactive with increasing
temperature and assist in modifying a rock’s mineralogy.
The composition of the original ______ rock determines the characteristics of a given metamorphic rock
parent
What is the range that most metamorphic rocks form
250C to 850C
At what depth does metamorphism start
> 8km
list the increase of metamorphic rocks from beginning at shale
Shale, slate, phyllite, schist, gneiss
Metamorphic rocks are divided into two textural groups…
foliated and non-foliated
The minerals within foliated rocks are flattened or aligned (oriented), forming a new
texture with a layered appearance. ______ and _______ minerals are in separate layers
mafic
felsic
Ways to tell between a sedimentary rock and a foliated metamorphic rock
minerals observed can be different
metamorphic rocks have fold structures (augen)
Don’t see grains
crystals in metamorphic rocks interlock
We can’t see sedimentary structures in foliated rocks and the foliation
planes are often not as flat as in sedimentary beds
How does foliation develop
pressure from plate tectonics causes
-rotation of minerals
-change in mineral shape
-recrystallization -
Foliation forms parallel or perpendicular to the force of pressure?
perpendicular
What happens if we continue to heat up gneiss
The rock begins to melts and you eventually
get a magma! There is an intermediate between metamorphic and igneous rock called a
migmatite
When do non-foliated rocks occur
- the pressure is low or equal from all directions
(contact metamorphism), or - the composition of the rock does not include platy
minerals such as mica
For a non-foliated rock, what does limestone become
marble
For a non-foliated rock, sandstone becomes
quartzite
What kind of minerals do non-foliated metamorphic rocks not contain?
no platy minerals in non-foliated rocks
List the grades of metamorphic rocks from least temp and pressure to most
sedimentary
low-grade metamorphic rock
intermediate-grade metamorphic rock
high-grade metamorphic rock
magma region
Describe low grade for metamorphism
May appear similar
to the protolith, but will have
some difference in texture and
(depending on the protolith)
mineralogy
Describe medium grade for metamorphism
Often very
different appearance from the
protolith, with different
texture and (depending on the
protolith) mineralogy e.g.,
schist
Describe high grade for metamorphism
Generally appears
very different from the
protolith, with different
texture and mineralogy e.g.,
gneiss
What does it mean to be an index mineral
- Certain minerals only form through metamorphism, at specific P and
T (pressure and temperature) conditions
What type of metamorphic rock form from hot water flowing through the rock
Greenschist
When increasing the metamorphism of a foliated rock, what mineral becomes more abundant
mica
Higher the grade of metamorphism the greater the size of the ______ crystals
mica
is quartz an index mineral
Can form under metamorphic, igneous, sedimentary conditions. Therefore it is not an index mineral
is feldspar an index mineral
no
is sillimanite an index mineral
yes
is kyanite an index mineral
yes
is garnet a index mineral
yes
is biotite an index mineral
yes
is muscovite an index mineral
yes
is chlorite an index mineral
yes
What are the grades of the following index minerals:
chlorite, muscovite, biotite, garnet, kyanite, sillimanite
chlorite - low to medium to high grade,
muscovite - low to medium grade,
biotite - medium to high grade,
garnet - medium to high grade,
kyanite - high grade ,
sillimanite - high grade
Describe diagenesis
chemical alterations of sedimentary rock occurring at shallow crustal depth (<8km, 150-200C)
oil and gas are generated
When do oil and gas break down
*Oil and gas break down into CO
occur (temperature >200°C)
2
if buried to depths where metamorphism can
What is the geothermal gradient on continents
25C per km
What are the types of metamorphism
- Contact metamorphism
- Seafloor metamorphism
- Burial metamorphism
- Regional metamorphism
What are the two main sources of heat for metamorphism
Igneous intrusions
Increase in depth of burial
Describe contact metamorphism
Hot magma chambers bake the host rock(country rock) where they come in contact this causes a change in mineral composition and texture and heats up surrounding groundwater which transports heat and dissolved ions(form vein deposits). This is localized within a few 100 meters.
High temperature, low pressure
Does contact metamorphism cause foliation
no
What kind of grades does contact metamorphism cause
low, medium, high
what are two examples of contact metamorphism
Quartzite and marble
What kind of rocks do we see for seafloor metamorphism
mafic rocks
What is regional metamorphism
A pattern of metamorphism associated with mountain building
and plate tectonics occurs over a large area, regional.
Regional metamorphism includes what temperatures, pressures and grades?
a range from low to high temperatures and low to high
pressures and may involve fluids.
- Grades from low to high grade based on P and T conditions
If i begin with the igneous rock basalt, what does the photolith become after continuous metamorphism
Basalt - Greenschist, amphibolite, Granulite
Ignore this card
Describe burial metamorphism
temperature increases with depth
and the geothermal gradient
* No directed pressure acting on the rocks, just weight of overlying
rocks. The pressure increases steadily with depth and rocks do not
have foliation associated with the metamorphism.
What is confining pressure
Feeling pressure from all sides. Force applied equally in all directions
What is the geological environment for gneiss
high grade
regional
What is the geological environment for schist
medium grade
regional
What is the geological environment for Slate
low grade
regional
What is the geological environment for quartzite
contact and regional
What is the geological environment for marble
Contact and regional
Which of the following are foliated:
Gneiss, Schist, slate, Quartzite, marble
Gneiss, Schist, slate,
Which of the following are non-foliated: Gneiss, Schist, slate, Quartzite, marble
Quartzite and marble
Reactive hot fluids such as ____ and ____ containing ions enhance the metamorphic process
H2O and CO2
Protolith composition will not change unless there are ______ moving through the rock
fluids
Crystal size always gets ________ and _______ interlocked as you move from low to high grade
bigger
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