1. Dating of a lunar rock sample (77215)
Carlson RW, Phil. Trans. R. Soc., 2014, 372
Lena Bastian / Pascal Becker

2. Geochronology
„Field of scientific investigation concerned with determining the age and history of Earth’s rocks and rock assemblages” ( (last checked: ))
Some applications:
Formation of the Solar System, the Earth and the Moon
Plate tectonics
Evolution of life and evolution of the human species
Mass extinction events
Archeology
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Lena Bastian / Pascal Becker

3. Rb – Sr decay system Rb Sr Monovalent Divalent
Relatively abundant trace element
More abundant than Rb
Substitutes for K
Substitutes for Ca
No own mineral phase
Own rare mineral phases: Celestine SrSO4 and Strontianite SrCO3
Ionic radius: 1.48 Å
Ionic radius: 1.13 Å
Mobile and incompatible
Less mobile and less incompatible
Concentrated in melt during crystal fractionation
Extracted earlier from melt during crystal fractionation
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Ulmer, P. Vulkane und Magmatismus Course FS 2016, ETH Zurich.
Lena Bastian / Pascal Becker

4. Radioactive Decay
Radioactive decay of parent: Radiogenic daughter isotope: Total concentration of daughter: For Rb – Sr System:
Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich
Lena Bastian / Pascal Becker

5. Isochron y = b + x m Assumptions: Isotopically homogeneous melt
Closed system
Cogenetic samples
Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich
Lena Bastian / Pascal Becker

6. Isochron Weighted regression: Goodness of fit:
Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich
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7. Rb – Sr system: Advantages and Disadvantages
High and very variable ratios
Relatively easily reseted
Common datable minerals
Not as precise as the U – Pb method
Relatively easy preparation, separation and measurement
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8. Other important decay systems
U – Th – Pb
Sm – Nd
Lu – Hf
K – Ar
14C dating
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9. Sample Preparation Crushing sample in mortar Sieving to sort by size
Separation via density, magnetism and hand picking
Separate Sr and Rb by use of ion-exchange resin or chromatography
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10. Isotope Dilution
Precise amount of isotope reference solution („spike“) added to sample
Spike either enriched in minor isotopes or containing artificial isotopes
Determination of the isotopic composition relative to the added spike
Correction for mass fractionation using a double spike
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Lena Bastian / Pascal Becker

11. Instrumentation TIMS (Thermal Ionization Mass Spectrometry)
MC-ICP-MS (Multi-collector Inductively-Coupled-Plasma Mass-spectrometry)
IRMS (Isotope Ratio Mass Spectrometry)
CRDS (Cavity Ring Down Spectroscopy)
LAMIS (Laser Ablation Molecular Isotope Spectrometry)
Lena Bastian / Pascal Becker

12. TIMS Ionization of sample through intense heating in vacuum
+ Stable measurement
+ no isobaric interferences
+ more precision
- Limitation through ionization potential of certain elements
- Low degree of ionization
- Requires very clean sample
Lena Bastian / Pascal Becker

13. MC-ICP-MS Use of inductively coupled plasma to ionize sample
+ Requires less sample preparation
+ Less affected by matrix effects
+ measurement of multiple elements possible
- More fractionation effects
- Isobaric interferences
- Less accurate
Lena Bastian / Pascal Becker

14. Moldovan, M. , J. Anal. At. Spectrom., 2004, 19, 815–822
Lena Bastian / Pascal Becker
Moldovan, M. , J. Anal. At. Spectrom., 2004, 19, 815–822

15. IRMS Combustion of sample followed by electron impact ionization
+ Great for organic samples
+ HR Mass Analyzer can be used
- For volatile species only
- Only for light elements
Lena Bastian / Pascal Becker

16. Cavity Ring Down Spectroscopy
Lena Bastian / Pascal Becker
(Taken from Master Course: Experimental Techniques at vrije universiteit amsterdam)

17. Cavity Ring Down Spectroscopy
Lena Bastian / Pascal Becker
Rok Zaplotnik et al, 2015, Plasma Sources Sci. Technol.,24

18. Laser Ablation Molecular Isotope Spectrometry
Lena Bastian / Pascal Becker
Russo, R., Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 66, Issue 2, 2011, Pages

19. Measurement Sr, Nd and Sm were measured using TIMS
Rb, Hf and Lu were measured using MC-ICP-MS
Use of external standards for quantification
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20. Data evaluation
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21. Isotope Determination in Forensics
Finding the geographical place of origin of an unidentified individual found in the Netherlands in 1999.
Cold case for 14 years
«Reference Material» thanks to exhumations
Lena Bastian / Pascal Becker

22. Isotope Maps
Making use of δ 13 𝐶, δ 15 𝑁, δ 18 𝑂, 87 𝑆𝑟 𝑆𝑟 , 𝑃𝑏 𝑃𝑏 , 𝑃𝑏 𝑃𝑏
δ 13 𝐶= 𝐶 𝐶 𝑆𝑎𝑚𝑝𝑙𝑒 𝐶 𝐶 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 −1 ∗1000 ‰
Lena Bastian / Pascal Becker

23. Isotope Maps Bowen, G., Annu. Rev. Earth Planet. Sci. 2010. 38:161–87
Lena Bastian / Pascal Becker
Bowen, G., Annu. Rev. Earth Planet. Sci :161–87

24. Lena Bastian / Pascal Becker

25. Analytical Procedure: Samples
Hair
Finger/Toe nails
Teeth (Tooth enamel)
Bones (Femur shaft/bio-apatite, Rib bone/collagen)
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26. Analytical Procedure: Sample treatment
Removing outer layers of tooth enamel and bones
Digestion of the sample (Hydrogen Peroxide to remove organics, nitric acid to dissolve metals)
Separation of Sr and Pb by means of chromatography
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27. Analytical Procedure: Measurement
Use of TIMS for Sr and Pb
Use of IRMS for C,N and O
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28. Analytical Procedure: Data Evaluation
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31. The Result
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32. Thank you for your attention!
Lena Bastian / Pascal Becker