Petrology Exam 2 Flashcards
(28 cards)
What minerals are common in granite?
K-feldspar (orthoclase), quartz, plagioclase.
What are granitoids?
Granite, granodiorite, tonalite, trondhjemite.
What is anatexis?
Partial melting of crustal rocks like shale and basalt to form felsic magmas.
What is a hypersolvus granite?
A granite with one feldspar due to low water pressure during crystallization.
What is Rapakivi texture?
K-feldspar mantled by plagioclase, found between hypersolvus and subsolvus granites.
What are the three processes that modify magma?
Fractional crystallization, assimilation, and magma mixing.
What is the difference between Ilmenite and Magnetite types?
Ilmenite-type has 100% Fe2+, Magnetite-type has ~30% Fe2+.
Define prograde metamorphism.
A process involving increasing temperature and pressure.
What is recrystallization?
Formation of a large crystal from many smaller ones due to temperature increase.
What are the types of deviatoric stress?
- Tension(extension),
- compression(perpendicular mineral growth),
- shear(stress at an angle).
What are primary fluid inclusions?
Fluids trapped during mineral growth.
What minerals are found in greenschist facies?
Chlorite, epidote, actinolite, albite.
What defines blueschist facies?
Presence of glaucophane, lawsonite, jadeite under high pressure, low temperature.
What is characteristic of granulite facies?
Very high temperature; minerals like orthopyroxene, clinopyroxene, garnet.
What are the dehydration melting temperatures of muscovite and biotite?
Muscovite: 650–700°C, Biotite: ~750°C.
What are migmatites?
High-grade metamorphic rocks that have partially melted.
What is the difference between hypersolvus and subsolvus granites?
Hypersolvus has one feldspar (low H2O), subsolvus has two feldspars (high H2O).
What are the three granite classifications and their protoliths?
I-type (igneous), S-type (sedimentary), A-type (anorogenic).
Which oxidation state minerals indicate I-type and S-type granites?
I-type: Magnetite (Fe3O4), S-type: Ilmenite (FeTiO3).
What is aplite and how does it differ from obsidian?
Aplite is an intrusive, light-colored rock; obsidian is a glassy, hydrous volcanic rock.
What is the difference between prograde and retrograde metamorphism?
Prograde occurs with increasing T/P, retrograde with decreasing T/P and fluid presence.
What causes devolatilization reactions?
Temperature increase; minerals break down and release H2O and CO2.
What structures form due to shear stress?
Mylonites, protomylonites, ultramylonites, and porphyroclasts.
What happens to minerals during compression?
New minerals grow perpendicular to stress.
