Midterm 1

Question 1

The incompatible elements

Answer 1

Concentrated on last stage differentiations of magmas such as pegmatites and hydrothermal veins

Question 2

Pragmatite

Answer 2

A course grained igneous rock usually of granite composition

Question 3

How are minor elements within minerals (4 ways)

Answer 3

1) interstitial lattice positions
2) fluid inclusions
3) exsolved mineral phases
4) ionic substitution

Question 4

What is the first rule of Goldschmidts substitution

Answer 4

The ions of one element can extensively replace those of another in an ionic crystal if their radii differ by less than 15%

Question 5

What is the second rule of Goldschmidts substitution

Answer 5

Ions who’s charged differ by one unit substitute readily for one another. If charges differ by more than one unit substitution is slight

Question 6

What is the third rule of Goldschmidts substitution

Answer 6

When two ions can occupy a particular position in a crystal lattice, the ion with the higher ionic potential forms a stronger bond with the surrounding anions.

Question 7

What is the forth rule of Goldschmidts substitution

Answer 7

Substitution may be limited even when size and charge criteria are satisfied.

Question 8

Couples substitution is…

Answer 8

Key to feldspars

Question 9

Electronegativities

Answer 9

A measure of ionic character in covalent bonds

Question 10

The distribution of minor elements in minerals depends on… (3 things)

Answer 10

The concentration of ions
The coordination number
The temperature

Question 11

The coordination number

Answer 11

The number of anions that surrounds a particular cation in an ionic crystal. Can be predicted by radius ratio

Question 12

Radius ratio

Answer 12

The ratio of radius of cation to that of the anion

Question 13

Minor elements partitioned between the solid & liquid… (3 ways)

Answer 13

1) camouflage (D=1): occurs when the minor element has the same charge and a similar ionic radius as the major element it is replacing

2) capture (D>1): takes place when a minor element enters a crystal preferentially because it has a higher ionic potential than the ions of the major element

3) admission (D<1): involves the entry of a foreign ion that has a lower ionic potential than the major ion because it has either a lower charge or a larger radius.

Question 14

Lithophile?

Answer 14

Associated with silicates and concentrated in crust

Question 15

Chalcophile?

Answer 15

Associated with sufides

Question 16

Siderophile?

Answer 16

Occurs at the native metal and concentrated in corr

Question 17

Atmophile?

Answer 17

Occurs as gasses in atmosphere

Question 18

Internal structure of earth?

Answer 18

Core, mantel, crust

Question 19

What and where is the crust mantle boundary?

Answer 19

40km under continents
Called Mohorovičić discontinuity “Moho”

Question 20

What and where is the mantle core boundary?

Answer 20

2883km under continents
Called the wiechert-Gutenberg discontinuity

Question 21

Pyrolite?

Answer 21

A model of earths mantle composed of peridotite and basalt in 3:1

Made by ringwood (1966)

Question 22

Undepleted mantle

Answer 22

Estimated using garnet-lherzolite and spinel-lherzolite occurred as demolish and kimberlite

Question 23

Spinel or garnet lherzolites

Answer 23

Composed of olivine, clinopyroxene, orthopyroxene, garnet, spinel and phlogopite

Question 24

Depleted mantle rocks

Answer 24

Dunite and harzburgite in ophiolite

Question 25

Craton

Answer 25

The stable continental interior

Question 26

Shield

Answer 26

A large stable continental region consisting of exposed Precambrian igneous and metamorphic rocks

Question 27

Platform

Answer 27

The relatively underformed Phanerozoic strata surrounding the shield

Question 28

The enrichment factor

Answer 28

The ratio of the average concentration of an element in igneous rock divided by its average concentration in crust