Final

Question 1

batch melting (equilibrium partial melting)

Answer 1

• melt is in EQ w/ the rock and the melt does not leave the system as melting progresses (much more common)
  (melt continually reacts in equilibrium with solid residue at site of melting, until escape as a single batch of magma)

Question 2

fractional melting

Answer 2

melt leaves the system as soon as it is produced by partial melting

Question 3

partial melting

Answer 3

the magma is enriched in SiO2, Na2O, K2O.

• a low degree of partial melting can produce granitic magma
• residual rock is enriched in MgO and FeO

Question 4

fractional crystallization

Answer 4

residual magma is enriched in SiO2, Na2, K2O

Question 5

Equilibrium Crystallization

Answer 5

equilibrium between all solids & melt during crystallization

Question 6

compatible elements

Answer 6

preferred to be in the minerals

• 1st to crystallize into a rock from magma
• D > 1
• HREE

Question 7

incompatible elements

Answer 7

preferred to be in the magma

- D

Question 8

REE Patterns (2)

Answer 8

1) total REE will increase with magmatic evolution (if REE were not all equally compatible)
2) REE pattern will be flat (if all REE were equally compatible)

Question 9

Lanthanide Contraction (3) - REE from La->Lu

Answer 9

1) decrease radius La to Lu
2) Increase Ionic Potential
3) Increasing compatibility

Question 10

Since REE are not all equally incompatible (3)

Answer 10

1) total REE will increase with magmatic evolution
2) REE pattern generally inclined to the right
3) there are some anomalies

Question 11

What is the difference between REE & spider diagrams

Answer 11

• REE diagrams only have REE elements

- Spider diagrams include REE + other elements

Question 12

Spider Diagrams (3)

Answer 12

• similar to REE diagram but plus other incompatible elements
• in order of increasing compatibility
• Normalized to a candidate reservoir (ex: condrites)

Question 13

What are the 3 sources of magma?

Answer 13

1) primitive deep mantle (OIB)
2) depleted upper mantle (MORB)
3) continental crust (CFB) - have more incompatible elements (melt 1st, lighter)

Question 14

is the crust composed of incompatible or compatible elements?

Answer 14

incompatible

Question 15

is the mantle composed of incompatible or compatible elements?

Answer 15

compatible

Question 16

2 areas of fluid rock interactions

Answer 16

• surface

- burial

Question 17

Fluid rock interactions - Surface

Answer 17

• weathering of granites/feldspars

- karstification

Question 18

Fluid Rock Interactions - Burial

Answer 18

• Dolomitization

- Albitization

Question 19

Dolomitization

Answer 19

• most dolomite is from replacement of limestone during diagenesis rather than precipitating from seawater
• 2CaCO3 + Mg2+ -> CaMg(CO3)2 = Ca2+

Question 20

Albitization

Answer 20

Plagioclase + Na+ -> Albite + Ca+

Question 21

Karstification

Answer 21

stalagmites, stalactities, CO2 enriched in soil

- when H2O filters into cave its P drops causing CO2 to escape => precipitates of stalagmites/stalactites

Question 22

What are isotopes?

Answer 22

• atoms of the same atomic number but different atomic mass
  -Ex: 12C: 6 protons, 6 neutrons, 6 electrons
  13C: 6 protons, 7 neutrons, 6 electrons

Question 23

Radioactive Decay

Answer 23

process in which a radioactive element undergoes constant change in the number of protons and neutrons through emission of alpha, beta, and gamma particles

Question 24

beta decay

Answer 24

• parent -> daughter
• mass unchanged
• proton # changed (becomes a different element)

Question 25

alpha decay

Answer 25

- parent -> daughter - mass reduced by 4 - proton number reduced by 2

Question 26

What is a stable isotope?

Answer 26

those that do not result from decay of other elements but do not decay to other elements

Question 27

What is the use of Stable Isotopes in geology? (3)

Answer 27

1) isotopes of any elements are not equally distributed in different material (rock, fluid, etc.) 2) can be used to trace the source(s) of geologic material (water, CO2) 3) can be used to estimate T b/c their distribution is related to T

Question 28

Isotope Fractionation

Answer 28

when 2 substances that contain an element co-exist in equilibrium, the isotopes of the elements is not equally distributed in them, but rather are fractionated

Question 29

General Rule of Isotope Fractionation

Answer 29

the heavy isotope goes preferentially to the chemical compound which the element is bound most strongly - O18 -> water; O16 -> clouds; (some O18 will go to cloud and some O16 will go to water)

Question 30

EQ crystallization

Answer 30

minerals being crystallized are in EQ with the melt & do not leave the system

Question 31

fractional crystallization

Answer 31

minerals leave the system as soon as crysalized

Question 32

How can granites be formed? (2)

Answer 32

- partial or complete melting of rocks in the crust - partial melting of rocks in the mantle - can be distinguished by different Sr/Sr initial values

Question 33

What conditions are favorable for carbonate rock formation?

Answer 33

- warm temperatures (Ksp decreases with increase in T) - Shallow water is favorable (Ksp decreases w/ decreased P; CO2 is consumed by photosynthesis; CO2 dissolution is low due to low P)

Question 34

What conditions are unfavorable for carbonate rock formation?

Answer 34

Deep water is unfavorable - Ksp up with T down - CO2 is produced by organism decay and CO2 dissolution is high due to High P

Question 35

Precipitation Order of Evaporites

Answer 35

Minor Carbonates (50% H2O) Gypsum (20% H2O) Halite (10% H2O) Potash (

Question 36

What is the meaning of metamorphic phase diagrams?

Answer 36

each line is a chemical reaction

Question 37

how do we know the P-T-X conditions of metamorphism?

Answer 37

geothermometer/geobarameter (ie: garnet/biotite & fluid inclusion)

Question 38

how do we know if an element was gained or lost during metamorphism?

Answer 38

construct an isocon and; you can see

Question 39

What is an ore deposit?

Answer 39

useful elements are enriched relative to the background to the extent that a profit can be made from extracting them

Question 40

Concentration Factor of an ore deposit

Answer 40

minimum expoitable grade/crustal abundance

Question 41

how can ore elements be enriched?

Answer 41

mechanical (placer deposits | chemical (most ore deposits)

Question 42

primary halo

Answer 42

- enrichment of elements association with mineralization surrounding a mineral deposit relative to the background - concentrations higher than background but lower than the ore bodies

Question 43

primary dispersion

Answer 43

the process that forms the primary halo

Question 44

pathfinder elements

Answer 44

elements that are associated with ore deposits and that are more mobile than the ore elements on the surface. Thus forming large secondary dispersion that can help to find the primary source