Exam 2

Question 1

Felsic Minerals & Granitoids

Answer 1

Granite: K-spar, qtz, plag
Mica: Biotite, muscovite
Granitoids: Granite, granodiorite, tonalite, trondhjemite
White micas: pyrophyllite, phengite, celadonite

Question 2

Anatexis

Answer 2

Partial melting
Shale → Granite
Basalt → tonalite/trondhjemite

Question 3

Classifications of Granites

Answer 3

I-type: Igneous (basalt)
S-type: Sedimentary (shale)
A-type: Anorogenic, dry heat flow

Question 4

Oxidation States

Answer 4

Magnetite (I-type): Oxidized
Ilmenite (S-type): Reduced

Question 5

Melt Reactions

Answer 5

Muscovite dehydration: ~650–700°C
Biotite dehydration: ~750°C

Question 6

Migmatites

Answer 6

Metamorphic rocks that have undergone partial melting
Birthplace of many granites (high-grade)

Question 7

Granite Textures by Water Pressure

Answer 7

Low H2O: One feldspar (hypersolvus)
High H2O: Two feldspars (subsolvus)
Rapakivi: K-spar mantled by plag

Question 8

Magma Processes

Answer 8

1. Fractional Crystallization
2. Assimilation
3. Magma mixing

Question 9

Textures

Answer 9

Obsidian: glassy, hydrous
Aplite: Intrusive, dry

Question 10

Isograd

Answer 10

Line drawn on a map indicating the appearance of a new metamorphic mineral

Question 11

Temperature Effects

Answer 11

1. Recrystallization: Large xtal at expense of small ones
2. Reactions: Kyanite → sillimanite or albite → jadeite + Qtz
3. Devolatilization: Hbl + plag + qtz → Cpx + Grt + H2O + melt

Question 12

Metamorphism

Answer 12

Change in mineralogy/texture due to temperature and pressure (T/P)

Question 13

Metamorphism Types

Answer 13

Prograde: Increase T/P
Retrograde: Decrease T/P (requires H2O)

Question 14

Deviatoric Stress

Answer 14

Causes deformation:
- Tension: Extension
- Compression: Perpendicular mineral growth
- Shear: Stress at an angle

Question 15

Metamorphic Fluids

Answer 15

Primary fluid inclusions trapped during mineral formation
Common in amphiboles, feldspars, quartz

Question 16

Facies (Metamorphic)

Answer 16

Ranges of P/T that result in a characteristic mineralogy

Question 17

Facies: Zeolite

Answer 17

Very low grade
Calcium, albite minerals

Question 18

Facies: Prehnite-Pumpellyite

Answer 18

Very low grade

Question 19

Facies: Blueschist

Answer 19

High P / Low T
Glaucophene, blue amphibole, garnet, epidote

Question 20

Facies: Greenschist

Answer 20

Excess silica
Epidote, chlorite, actinolite (green color)

Question 21

Facies: Albite-Epidote Hornfels

Answer 21

Low P / High T

Question 22

Facies: Hornblende Hornfels

Answer 22

Intermediate grade

Question 23

Facies: Amphibolite

Answer 23

High grade
Hbl, grt, plag, aug

Question 24

Facies: Granulite

Answer 24

Very high T, low H2O
Opx, cpx, garnet

Question 25

Facies: Pyroxene Hornfels

Answer 25

High temperature, intermediate depth

Question 26

Facies: Eclogite

Answer 26

High P, deep crust Kyanite, omphacite, garnet

Question 27

Facies: High P/T Metamorphism

Answer 27

Talc, phengite, celadonite, pyrophyllite, garnet, kyanite, white micas

Question 28

Facies: Ultrahigh Pressure

Answer 28

Coesite and diamond

Question 29

ACF Diagram

Answer 29

Predicts minerals in a rock Unary: Qtz, corundum, calcite Binary: Al2SiO3, wollastonite Ternary: Grossular, anorthite

Question 30

Polymorphs of Al2SiO3

Answer 30

Kyanite: High pressure Andalusite: Low pressure Sillimanite: High temperature

Question 31

Why does X solution occur in minerals?

Answer 31

Due to slow cooling or size in cations Elements can swap without altering overall structure

Question 32

Where does metamorphism start?

Answer 32

Around 200°C at low pressure, where new minerals start to grow

Question 33

Biotite Types

Answer 33

Annite and phlogopite

Question 34

Garnet Types

Answer 34

Almandine, pyrope, grossular, serpentine

Question 35

Olivine Types

Answer 35

Fayalite and forsterite

Question 36

Hypersolvus vs Subsolvus Granites

Answer 36

Hypersolvus: Low H2O, single feldspar Subsolvus: High H2O, two feldspars

Question 37

Medium P/T facies:

Answer 37

-Orogenic greenschist, amphibolite and granulite facies

Question 38

Low P/T facies:

Answer 38

-contact metamorphism albite–epidote hornfels, hornblende hornfels, pyroxene hornfels, and sanidinite facies

Question 39

High P/T facies:

Answer 39

-subduction zones blueschist and eclogite facies

Question 40

paired metamorphic belt

Answer 40

two distinct metamorphic belts that form along convergent plate boundaries, often associated with subduction zones

Question 41

Contact metamorphism

Answer 41

a type of metamorphism where rocks are transformed by the heat from nearby magma or lava intrusions

Question 42

Regional metamorphism

Answer 42

a type of metamorphism that occurs over large areas, typically associated with tectonic processes like mountain building or burial in basins

Question 43

Hydrothermal metamorphism

Answer 43

typically occurs along mid-ocean ridge spreading centers where heated seawater percolates through hot, fractured basalt

Question 44

Lineation

Answer 44

is any linear structure, such as the axis of the fold, grooves on a fault plane, or the direction

Question 45

Foliation

Answer 45

Metamorphic foliations, including cleavage, schistosity, and gneissose structure

Question 46

What are primitive magmas?

Answer 46

Magmas with very high liquidus temperatures and high MgO contents, such as picrite basalt.

Question 47

What is equilibrium crystallization

Answer 47

A process where crystals remain in contact with the melt during solidification.

Question 48

3 arrow trajectories:

Answer 48

1. medium p/t: metamorphism barrovian sequence 2. low p/t: Buchan 3. high p/t: subduction