Class Notes: Metamorphic Rocks, Geology of Saskatchewan, and Meteorites Flashcards
What is the difference between metamorphism and deformation?
Metamorphism is a chemical process
Deformation is a physical process
Where does metamorphism and deformation primarily occur?
In orogens
Where does metamorphism take place?
At depths >5km, where there is high pressure (lithostatic pressure) and high temperature (especially where >300 degrees C).
What is recrystallization with metamorphism?
This involves ion by ion disaggregation of mineral grains and the reassembly of these ions into new unit cels which grow into new crystal grains
What does limestone recrystallize into? Olivine?
Limestone – marble
Olivine – serpentine
Which metamorphic minerals(s) will form depends on the ___ ___ ___.
original chemical composition
What is included under mineral stability (3 things)?
- temperature
- pressure
- fluids present
What is the protolith?
original rock
What are the three types of protoliths?
any igneous, sedimentary, or pre-existing metamorphic rock
What are the steps in metamorphism?
- protolith
- deeply buried
- temperature increase (250-300 degrees C)
- thermally induced chemical alterations
- ions change places
- recrystallization
- metamorphic rock
How much of the Earth’s Continental Crust is composed volumetrically, of metamorphic rocks?
90%
What percent of near-surface rocks are metamorphic?
60%
What percent of the rocks below 10 km depth are metamorphic?
100%
Metamorphic rocks occur everywhere that rock temp. exceeds___(10 km depth).
250-300 degrees C
Where do metamorphic rocks occur on Earth’s surface?
Wherever uplift has occurred with erosion to bring them to the present surface – primarily in orogens (thrust faulting and orogenic isostatic uplift)
What are all precambrian shields made out of?
metamorphosed rock
What are are all young and old tectonic mountain belts composed of?
metamorphosed rock
What are the 4 common names for metamorphic rock?
- protolith
- slate
- shist
- gneiss
What is slate (grains and grade)?
slaty cleavage fine grained (low grade)
What is shist (grains and grade)?
visible grains (med grade)
What is gneiss (grains and grade?
course grained (med-high grade)
What are the two types of metamorphism?
- contact
2. regions
Where does contact meta. occur?
Occurs in ‘haloes’ or aureoles adjacent to intrusive bodies, especially batholiths (may or may not be in an orogen).
What does the intrusive body provide in contact meta.?
The intrusive body provides some of the heat and some of the pressure necessary and perhaps some of the fluids.
Where does regional meta. occur?
- occurs in orogens and misrelated to deformation
- occurs over large volumes (surface areas)
What is the ‘common’ type of metamorphism?
regional
What are metamorphic facies?
grade, zones
What are metamorphic facies based on?
Mineral stability under conditions of various temperatures and pressures (fluids not a concern here)
What is the most important part of meta. facies?
temperature
What is the cordilleran orogen?
An enormous mountain belt that extends down through the andes to the tip of south america
What is the youngest tectonically action region of north america?
the cordilleran orogen
What is the cordilleran orogen composed of?
It consists of folds an defaulted sedimentary rocks, metamorphic rocks and igneous rocks including large granite batholiths. It is tectonically and volcanically active.
What are the “platform” rocks almost entirely composed of? What are their strata like? What do they blanket?
sedimentary rocks that have undergone very little folding and faulting and have experienced no metamorphism. Their strata are flat-lying or gently dipping and they blanket the buried part of the precambrian shields.
Is the cordilleran mtn. belt younger or older than the appalachian mtn. belt?
younger
How can we tell the age of an orogenic mountain belt?
We can tell the age of an orogenic belt if we can find the youngest deformed rocks overlain unconformably by undeformed sedimentary rocks – such a a relationship usually shows up as an angular unconformity.
What is the oldest part of the NA continent?
the precambrian shield
How far does the precambrian shields extend?
Extends southwards under the younger sedimentary platform forces.
What does the precambrian shield consist of?
igneous and metamorphic rocks along with various types of sedimentary rock
Where does the appalachian mountains extend?
From the souther states to Newfoundland and is geologically continuous with the caledonian orogen of scotland and norway
What forms the grand banks of newfoundland?
the continental shelf
What does the full coastal plain pass into?
into the atlantic coastal plain in the North eAstern states and farther North the geological extension of the coastal plain is the continental shelf
Which canadian provinces and what part of the US would form one continuous orogenic belt with the mountains of ireland, wales, england, scotland, and scandanavia in the past before the opening of the atlantic ocean?
The mountains of the Eastern US, Quebec, The Maritime and Newfoundland
Where is uranium found in SK?
athabasca basic
What is the athabasca basin composed of?
sandstone, proterozoic
What age of rock is gold found in SK?
precambrian shield
What age of rocks is limestone and shale (salt) found in SK?
paleozoic
What period is coal from?
tertiary
What age of rock is oil and potash?
mesozoic and potash is also found in in the paleozoic disconformity DEVONIAN
Where is petroleum found (time period)?
cretaceous
Do meteorites have high or low densities?
high
The crust of a meteorite is called a___crust, meaning that it may___with time.
- fusion
- rust
What is the shape of a meteorite?
Mixture of smooth, rounded surfaces and angular forms
Which meteorites aren’t magnetic (all the others are)?
Achrondites and carbonaceous chrondites
Is a meteorite poros and does it contain bubbles?
no
Is a meteorite radioactive?
no
Is a meteorite concentrically banded?
no
Are meteorites spherical?
almost none are
What are the 3 broad categories of meteorites?
1) stony meteorites
2) iron meteorites
3) stony-iron meteorites
What is he concentration of iron in stony meteorites?
<25%
What is the concentration of iron in iron meteorites?
> 75%
What is the concentration of iron in stony-iron meteorites?
~50-50% iron and stone
What two categories are stony meteorites divided into?
1) chrondites
2) achrondites
What are the two types of stony-iron meteorites?
1) pallasites
2) mesosiderites
How many km is the atmosphere to earth?
80-100 km
At what speed does light flight become dark flight with a meteorite?
~300 m/s
How far is dark flight?
5-18 km
The strewn field is___km long.
several
What is the strewn field?
region where they fell
How many meteorite fragments may there be?
May be up to several to thousands of fragments
What happens as light flight becomes dark flight?
- They glow as they come into atmosphere
- Eventually they cool, stop exciting atmosphere, and fall – no longer melting. Lost 90% or more of their velocity.
What is the temp. of low grade meta. rx?
250 degrees C
What is the temp of high grade meta. rx?
650 degrees C (some rocks melt)
What is the temp where all meta rx will melt?
1050 degrees C (all rocks melt)
What does recrystallization result from?
“solid state ion diffusionWhat is differentiation? “ which increases with temperature (pressure a bit)
Wha tis differentiation?
The mineral component of an accreted body heats (melts?) and undergoes gravitational separation into two broad groups resulting in a dense core (iron/nickel) and less dense mantle (silicates)
Every rocky body in our solar system undergoes differentiation if greater than___km diameter.
200 km diameter
What are undifferentiated meteorites?
The asteroids, and thus the meteorites derived from them are just like they were shortly after they accretion at 4.55 Ga, except for modification within the asteroid by metamorphism or water alteration.
What is the one type of undifferentiated meteorites?
chrondites
What percent of falls is chrondites?
86%
Do chrondites contain chrondules?
yes
What are differentiated meteorites?
These come from asteroids that were large enough to have undergone differentiation into iron/nickle cores and silicate mantles, some have even undergone volcanism, which would have produced a crust as well.
What are the three types of differentiated meteorites?
1) iron meteorites (cores)
2) achrondite meteorites (mantle and crust)
3) stony iron meteorites (outer core with mantle grains)
What percent of falls are iron meteorites?
4.7%
What percent of falls are achrondite meteorites?
8%
What percent of falls are stony iron meteorites?
1.3%
What are chrondules composed of?
olivine or pyroxene chrondites
What are the 3 things we see when we cut open a chrondite meteorites?
1) iron grain
2) chrondule
3) small grains (same composition of chrondules
What is the ‘ordinary’ type of meteorite?
chrondite
What are the oldest things in meteorites?
CAI (Calcium aluminum inclusions)
