Part 1- Intro Flashcards Preview

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Flashcards in Part 1- Intro Deck (35):
0

What are trace element abundances usually quoted in?

Ppm or ppb

1

What do ppm and ppb mean in terms of trace elements?

• Ppm = 1 micro g in 1g of rock
• Ppb = 1ng in 1g of rock

2

What do major elements govern in rocks?

The mineralogy

3

What do trace elements do in a rock?

Substitute into mineral phases

4

What is a lithophile element?

•"rock-loving"
• partition into silicate phases

5

What is a siderophile element?

•"metal-loving"
• Partition into metallic liquids

6

What is a chalcophile element?

•"Sulphur-loving"
• Partition into sulphide liquids

7

What is an atmosphile elements?

• Highly-volatile
• Form gases or liquids at Earth's surface

8

Which two groups of elements bond together with which type of bonding to form oxide silicate minerals?
Therefore what classification do they belong to?

• Low and high electronegativity elements forming iconic bonds
• lithophile

9

What electronegativities do siderophile and chalcophile elements have? What bonding do they prefer?

• Intermediate
• Covalent and metallic

10

What type of sulphide liquids does the term chalcophile include?

Magmatic NOT AQUEOUS

11

What does HSE stand for?

Highly Siderophile Elements

12

Give an example of an element that exhibits more than one type of Goldschmidt's behaviour...

Nickel- is siderophile therefore concentrates in the core.
Behaves as lithophile in the mantle and substitutes for Mg in olivine

13

How does ionic radius vary across a period?

Decreases

14

How does ionic radius vary down a group?

Increases

15

How much can the ionic radii of ions vary for them to be able to substitute?

Up to 15%

16

How much can an ions charge vary by before it isn't substituted?

One unit

17

Are elements with a higher or lower ionic potential preferred for substitution?

Higher because they form stronger bonds

18

When size and charge of the substituting ions are similar what else can stop substitution occurring? (2)

• Different electronegativities
• Form bonds of different ionic character

19

What is the camouflage principle?
Give an example.

When two ions have virtually the same charge, ionic radii and electronegativity.

E.g.
Zr and Hf in Zircon

20

What is the capture principle?

When a trace is used in a mineral over a major because the trace has a higher ionic potential

21

What is the admission principle?

When ions are incorporated that have a lower ionic potential than the major

22

What essential does a partition/distribution (KD) coefficient mean?

How well a trace element partitions in a mineral from a melt

23

What KD value do compatible elements have?
Do they prefer solid or melt

KD > 1
Prefer solid phase

24

What KD value do incompatible elements have?
What phase do they prefer?

KD < 1
Prefer Liquid

25

What is the bulk partition coefficient (D)?

The sum of the individual partition coefficients weighed according to the relative proportions (mass fraction) of the mineral phases present

26

How can elements be deemed compatible in the mantle?

If they can substitute for the major cations that exist there

27

What does PGE stand for?
Are they compatible in the mantle?

Platinum Group Elements

Yes- partition strongly into mantle sulphides

28

What elements do the HSE include?

PGE and Re

29

Give an example of 2 elements that are incompatible in the mantle and thus where are they enriched?
Which of the 2 is more incompatible.

Rubidium (Rb) and Strontium (Sr)
Enriched in melt phases.
Rb is more incompatible.

30

What does LILE stand for

Large Ion Lithophile Elements

E.g. Rb, Sr, Cs, Ba

31

What is the only type of mineral in which Sr is compatible?
Where are the most dramatic Rb/Sr fractionations due to this?

• Feldspars
• Continental crust

32

What does REE stand for?

Rare Earth Elements (lanthanides)

33

Which of the REEs are most compatible?

The "heavy" REEs

34

Which is the most important mantle phase for REE fractionation?

Garnet
- heavy REEs are significantly more compatible (KD = 5) than LREE (KD = 0.02)