Exam 2 Flashcards
(40 cards)
What is the depth range for hypabyssal and plutonic rocks?
Hypabyssal: ~0-5 km; Plutonic: ~5+ km below the surface.
What mineral phases are part of mantle transition zones?
Wadsleyite and Ringwoodite
What is equilibrium crystallization
A process where crystals remain in contact with the melt during solidification.
What is fractional crystallization?
Crystals are removed from the melt as they form, preventing further reaction with it.
What are primitive magmas?
Magmas with very high liquidus temperatures and high MgO contents, such as picrite
basalt.
What are common types of mantle xenoliths?
Gabbroic, Dunite, Wehrlite, Lherzolite, Harzburgite, and Garnet-bearing peridotites.
What is the difference between aplite and obsidian?
Aplite is chemically similar to granite (dry), while obsidian is glassy and very hydrous.
What are the three main magma differentiation processes?
- Fractional crystallization
- Magma mixing
- Assimilation
What minerals indicate I-type vs. S-type granites?
I-type: Magnetite, hornblende;
S-type: Ilmenite, muscovite.
What causes deformation in metamorphic rocks?
Deviatoric stress-differential pressure causing stretching, compression, or shear.
What are primary metamorphic fluids
Fluid inclusions trapped during mineral formation, often in amphiboles, feldspar, or quartz.
What is an isograd?
A line on a geologic map indicating the first appearance of a particular metamorphic
mineral.
What minerals appear around 400-700°C in regional metamorphism?
400°C - Pyrophyllite;
420°C - Kyanite;
520°C - Chloritoid;
570°C - Staurolite;
630-690°C - Sillimanite.
What indicates high-grade metamorphism?
Presence of minerals like sillimanite, orthopyroxene, and spinel.
What are the three Al2SiO5 polymorphs and when do they form?
Kyanite (high pressure), Andalusite (low pressure), Sillimanite (high temperature).
What is the metamorphic significance of muscovite dehydration
Marks transition into high-grade conditions (e.g., amphibolite to granulite facies).
What is the solidus of water-saturated granite?
670*c
What texture develops in high-grade metamorphic rocks?
Gneissic banding and schistosity due to mineral alignment under directed pressure
Why does hornblende occupy a large area in the ACF diagram?
Due to its wide solid solution range.
What minerals are common in greenschist facies?
Epidote, chlorite, and actinolite (noted for their green color).
What happens to actinolite during the transition to blueschist facies?
It disappears, and blue amphiboles (e.g., glaucophane) appear.
What is the purpose of the isothermal-isobaric graph?
It shows stable mineral assemblages under constant temperature and pressure conditions.
What is metamorphic facies?
Ranges of pressure and temperature where characteristic mineral assemblages form.
What minerals are typical in greenschist vs. eclogite facies?
Greenschist: chlorite, epidote, actinolite;
Eclogite: kyanite, garnet-rich, omphacite (pyroxene).
