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GLE 2024 (Day 2) > MINERALOGY BASIC CONCEPTS (ISOTOPES) > Flashcards

MINERALOGY BASIC CONCEPTS (ISOTOPES) Flashcards

1
Q

Technique used to determine Isotope Ratios

A

Mass Spectrometry

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2
Q

Application of Isotope Studies

A

1) Source of Rock Studies
2) Origin of Water
3) Source Rocks for PetGeol
4) Changes in Ocean water Temp, Biological productivity and circulation
5) History of ice age glacial expansions and Contractions
6) Timing of Orogenies involving intrusions and metamorphisms

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3
Q

Contain nuclei that do not tend to change spontaneously and their nuclear configurations remain constant over time

A

Stable Isotopes

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4
Q

What are the stable isotopes of Oxygen?

A

Oxygen-18, Oxygen-17, Oxygen-16

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5
Q

What is the atomic number of Oxygen?

A

8

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6
Q

Relative proportion of Oxygen Isotopes on Earth

A

O16 99.7%
O18 0.2%
O17 Rare

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7
Q

What oxygen isotope ratio gives info on earth’s history

A

O18/O16

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8
Q

What is the isotopic signature of the atmosphere during evaporation

A

enriched with O16 (low O18/O16 ratio)

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9
Q

What is the isotopic signature of seawater during evaporation

A

enriched with O18 (High O18/O16 ratio)

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10
Q

Why?

A

MAS PREFERENTIALLY NAGEEVAPORATE SI O16 since it is lighter

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11
Q

What is the implication of GLACIAL EXPANSION in O18 and O16?

A

O16 which has more affinity to the atmosphere will be trapped in Glacial Ice and thus making Sea water saturated with O18

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12
Q

Whats the working principle on Glaciation and Oxygen Isotope?

A

MAXIMUM GLACIAL PERIOD = PEAKS of O18 in Marine Sediments

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13
Q

Unit of O18/O16 ratio

A

part per thousands (mils)

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14
Q

A period where there was an unusually warm period and unusually high evaporation leading to high O18/O16 ratio on marine seds

A

Cretaceous

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15
Q

The standard in for Carbon Isotope study

A

Cretaceous Pee Dee Belemnite

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16
Q

Naturally Occuring Isotopes of Carbon

A

Carbon-12, Carbon-13, Carbon-14 (Radioactive)

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17
Q

Atomic Number of Carbon

A

6

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18
Q

Relative abundance of Carbon Isotopes on Earth

A

Carbon-12 98.9%
Carbon-13 1.1%

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19
Q

What carbon isotoped is preferentially utilized by orgamism to synthesize organic molecules?

A

C12 (low C13/C12)

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20
Q

What carbon isotope is preferentially concentrated in the water column

A

C13 (High C13/C12)

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21
Q

When sediments have enriched with C13/C12 is implies that the water column is enriched with C13

A

Stagnant Circulation in the Oceans

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22
Q

Information or application of C13/C12

A

Global Ocean Circulation
Eveolution of New Group and Extinction of Old Groups

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23
Q

A period of warming that exist in the boundary of Paleocene and Eocene

A

Paleocene-Eocene Thermal Maximum

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24
Q

What happens during PETM

A

emergence and rapid radiation of mamals
extinciton of deep sea benthic forams

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25
Q

What may have caused PETM

A

Melting of clathrates - Frozen water which contain methane, methano and another trapped organic carbon molecule

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26
Q

Isotopes with unstable nuclei whose nuclear configuration tends to be spontaneously transformed

A

Radioactive Isotopes

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27
Q

Spontaneous transformation of Nuclear Configuration of an isotope

A

Radioactive Decay

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28
Q

The Isotope with unstable nucleus

A

Parent Isotope

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29
Q

Product of spontaneous transformation

A

Daugther Isotope

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30
Q

Ejection of alpha particle plus gamma rays from the nucleus

A

Alpha Decay

31
Q

Equivalent Proton and neutron of Alpha Particle

A

2 neutron 2 proton

32
Q

What will be the resulting daughter nuclear configuration?

A

Daughter isotope AN -2 AM -4 (2N+2P)

33
Q

Example of Alpha decay

A

U238 to Th234

34
Q

Ejection of Beta Particles plus heat from the nucleus

A

Beta Decay

35
Q

A high speed electron

A

Beta Particle

36
Q

What happens when a beta particle is emitted

A

A neutron is converted to proton (n - e = p)

37
Q

Resulting daughter isotope will have a nuclear configuration of?

A

AN +1
AM is conserved since loss of neutron is compensated by addition of proton

38
Q

Example of Beta Decay

A

Rb87 St87

39
Q

Addition of a high speed electron to the nucleus w/ release of heat in the form of gamma rays

A

Electron Capture

40
Q

Resulting nuclear configuration of the daughter isotope?

A

AN - 1
Am conserved loss of proton is compensated by addition of Neutron (p+e=n)

41
Q

Example of Electron Capture

A

KAr40

42
Q

The time required for one half of the radioactive isotope to be converted to the daugther isotope

A

Half life

43
Q

The stable isotope of U238

A

Lead 206

44
Q

How many steps will it take for U238 to be converted to Lead 206?

A

14 steps

45
Q

What is the primary use of U238 Pb206 Isotope?

A

the ratio of it Determines crystallization ages for minerals especially those formed in precambrian

46
Q

Process which convert Radioactive isotopes to Nuclear Enegry?

A

Nuclear Fission (I for energy)

47
Q

Uranium isotope which causes lung cancer

A

radon 222

48
Q

If radon is diluted in water, it will form

A

Radium

49
Q

The proportion of radioactive atoms that will decay per unit of time

A

Decay Constant (Lambda) unit is /year

50
Q

Relation formula of half life and decay constant

A

Half Life = ln2/ decay constant (Lambda)

51
Q

Formula for remaining Radioactive Isotope

A

Nremaining = Noriginal x e^-lambda*lapse time since formation
Nremaining = Noriginal x (1/2)^lapse time since formation / half life

52
Q

Formula for age of sample

A

Age = (1/lambda) ln (D/P +1)

53
Q

2 radioactive isotopes of Uranium

A

238 and 235

54
Q

Dating of Zircon, Titanite and Monazite

A

238U 206Pb

55
Q

Pb pair of U235

A

207 Pb

56
Q

Pair of Pb 208

A

232Th

57
Q

Half life of U238 to Pb 206

A

4.47 Ga

58
Q

Half life of R87 Sr 87

A

48.8 Ga

59
Q

Rb: K substitute = Sr:

A

Ca Substitute

60
Q

Line of constant age

A

Isochron

61
Q

Use of Initial 87Sr/86Sr

A

Identification of source regions from which magmas are derived

62
Q

The temperature below which a crystal lattice traps radioactive daughter products

A

Blocking or Closing temp

63
Q

Most reliable technique for rocks with ages exceeding 10Ma

A

U-Pb (4.47 Ga)

64
Q

Minerals which can be analyzed for U-PB

A

Zircon, Titane and Monazite

65
Q

What rocks are analyzed for Monazite and Sphene

A

Met Rocks

66
Q

ZrO2 minerals

A

Baddeleyite or Zirconia

67
Q

Upper curve of concordia represents

A

Age of orig magma or Inherted zrcons

68
Q

Lowe curve represents

A

Met age

69
Q

If points do not plot close to the statistically dertemined line

A

Mixing line/Scatterchron line

70
Q

87Sr/86Sr ratio of Middle to upper continental crust

A

> 0.706

71
Q

Useful in detremining source of magmas for plutons ad volcanic rocks and to reconstruct ancient continental margins

A

Rb-Sr (48.8 Ga)

72
Q

Usefuk for determination of uplift of a rock mass and determination of age of fine grained met rocks

A

K-Ar (1.2 Ga)

73
Q

Best used to dertermine ages of basaltic rocks and is most commonly employed to provide a model age for the time of separation of a magma from parent mantle and sea water contamination

A

Sm-Nd (106 Ga))

GLE 2024 (Day 2) (41 decks)

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