Mineralogy, Petrology and Geochemistry Flashcards
What are Cataclasites? And how are they formed?
Cataclasites are a cohesive, granular rocks that can be formed from any rock/ consist of any mineral assemblage. They are formed during dynamic metamorphism (at faults or when there is fracturing of the upper crust).
What facies are formed under contact metamorphism?
Albite-Epidote Hornfels
Hornblende Hornfels
Pyroxene Hornfels
Sanadinite
What facies are formed under regional metamorphism?
Zeolite
Prehnite-Pumpellyite
Blueschist
Greenschist
Amphibolite
Granulite
Eclogite
What grade (low, medium or high) of rock does burial metamorphism produce and why?
Low grade because the increased temperature and immense downward pressure causes the rock to recrystalize but not become foliated.
What are common products of impact metamorphism?
• High Pressure minerals (such as coesite or stishovite, both polymorphs of quartz)
• Highly granulated, deformed and shattered rocks
• Shatter cones
What is Bowen’s Reaction Series? What does it describe?
Based on a number of controlled laboratory experiments, it provides a generalized progression of mineral precipitation from a cooling magma, predicting mineral weathering which indicates the stability of minerals at the earths surface.
Minerals at the bottom are the most stable, and the ones at the top, being the quickest to weather- this is because minerals are the most stable at the conditions closest to which they formed under.
What are the 4 types of sedimentary rocks? Give examples of each.
- Clastic/ detrital (consist of clasts or grains)
- Conglomerate
- Sandstone
- Siltstone
- Shale - Biochemical (made from once living creatures- carbonates)
- Fossiliferous
- Oolithic
- Coquina
- Micrite - Organic (altered plant material/ containing Carbon)
- Peat
- Coal - Chemical (evaporates)
- Halite
- Gypsum
How are igneous rocks classified? What are the 7 textures of igneous rocks? And give examples of each texture with the corresponding felsic - mafic composition.
Classified by their cooling history, which dictates their texture.
1. Phaneritic (coarse grained)
- Felsic (Granite)
- Intermediate (Diorite)
- Mafic (Gabbro)
2. Aphaneritic (fine grained matrix)
- Felsic (Rhyolite)
- Intermediate (Andesite)
- Mafic (Basalt)
3. Porphyr
- intermediate (Porphyritic Diorite)
4. Glassy
- Obsidian
5. Vesicular
- Felsic (Pumice)
- Mafic (Scoria, vesicular basalt)
6. Pegmatic
-Felsic (pegmatic granite)
7. Pyroclast
- Felsic (Tuff)
Define diagenesis. What are the types of diagenesis processes?
Any change occurring within sediment during or after its deposition, and after its lithification, NOT INCLUDING weathering (because it is not representative of “normal surface conditions”).
• Compaction/ Cementation (becoming lithified or consolidated)
• Replacement (change in composition of a mineral)
• Crystallization (under normal surface conditions)
What are the different classifications of limestone and how are they linked to the deposition?
Clastic
Made up of calcium carbonate fragments that were deposited in place or were transported elsewhere within the basin in which they formed (predominantly in marine environments)
Non- clastic
Chemically or biologically precipitated calcite or aragonite that have NOT been transported since deposition
Ex. reef limestone (stromatolite)
And name and define/ give examples of the 3 types of facies for sedimentary rocks?
•Lithoclastic (differing texture, mineralogy, grain size, and depositional environment)
•Bioclastic (differing fossil content)
•Cyclothems (repeating sediments that represent the emerg/submergence of land)
And name and define/ give examples of the 7 types of facies for metamorphic rocks?
• Zeolite (Low P, Low T; ex. pyrite)
• Prehnite-pumpellyite (burial below water, shale, mafic rocks, Low P, Low T; ex. calcite and quartz)
• Green-schist (Low - Med P, Med T; chlorite, serpentine, epidote and Muscovite)
• Amphibolite (Med-High P, Med-High T; ex. amphibole and grossular garnet)
• Granulite (deep regional, Low - High P, High T; ex. biotite and olivine)
• Blue-schist (subduction zones, High P, Low T; ex. glaucophane)
• Eclogite (High P, High T; ex. garnet and pyroxene)
What does large grained igneous rocks tell us about their cooling history?
- Intrusive/ Plutonic
- Formed deep within the earth
- Cooled slowly
What do fine grained igneous rocks tell us about their cooling history?
- Extrusive
- Formed near the surface of the earth
- Cooled quickly
What can you infer from the clast sizes within sedimentary rocks - referring to their depositional environment?
(For example, large clast sizes come from (high or low?) energy environments, such as (a lake or river?)).
Large clast sizes usually mean that they were deposited from a high energy environment, such as it takes more energy to move larger particles. An example of a high energy environment is a fast-moving river.
Small clast sizes usually mean that they were deposited from a low energy environment, such as it does not take much energy to move smaller particles. An example of a low energy environment would be a lake or flood plain.
What is a mineral?
1.) naturally occurring
2.) characteristic chemical composition
3.) regular crystalline structure
4.) inorganic (cannot be made of living things)
What is “twinning”? Name a mineral that exhibits twinning.
It is the symmetrical intergrowth of 2 or more crystals of the same mineral with no chemical difference. Plagioclase has albite twinning.
What are striations and what do they represent? Give an example of a mineral that has striations.
They are fine lines on the surface of a mineral that represent the intersection of twinning planes. Plagioclase will exhibit striations as it has albite twinning.
What is exsolution and what causes it?
It is the physical un-mixing of ions in a mineral resulting in 2 minerals of distinct composition in a single crystal. It is caused by the inability of different cations to be accommodated in the same region of a slowly cooling mineral.
In what cooling environment will exsolution form?
High temperatures - complete solid solution between plagioclase and potassium feldspar (random mixing of Na and K)
In what cooling environment will twinning form?
Low temperatures - slower cooling gives ions time to migrate resulting in the intergrowth of plagioclase and alkali feldspar.
What are the main 2 distinguishing elements that make up plagioclase feldspar?
Calcium (Ca) and Sodium (Na)
What are the main 2 distinguishing elements that make up potassium feldspar?
Potassium (K) and Sodium (Na)
What are the main 2 distinguishing elements that make up olivine?
Iron (Fe) and Magnesium (Mg)
What is the main distinguishing element that makes up quartz?
Silicon (Si)
What charge do cations have?
Positive
What charge of anions have?
Negative
Name the order of minerals (see Bowens reaction series) from high (early crystallization) to low (late crystallization) temperature forming.
Old - Olivine
People - Pyroxene
Are - Amphibole
Boring - Biotite
as
Fuck - Feldspar (Potassium)
unless they are
Majorly - Muscovite
Queer - Quartz
What is a Redox reaction?
Gaining an electron
What is an Oxidation reaction?
Loss of an electron
What is the chemical formula for quartz?
SiO2
When do covalent bonds form?
When the electronegativities are high and similar
When do metallic bonds form?
When the electronegativities are low and similar
When do ionic bonds form?
When the electronegativities are greatly different
Where can regional metamorphism occur?
Convergent plate boundaries; related to mountain building
Where can contact metamorphism occur?
Where magma intrudes into cooler host rock
Where can dynamic metamorphism occur?
At fault zones (where there is high shear stress)
Where can burial metamorphism occur?
Beneath layered sediments
Where can impact metamorphism occur?
When a meteorite impacts earth
Where can hydrothermal metamorphism occur?
Divergent plate boundaries/ mid ocean ridges
