Dating of a lunar rock sample 77215 Carlson
- Slides: 32
Dating of a lunar rock sample (77215) Carlson RW, Phil. Trans. R. Soc. , 2014, 372 Lena Bastian / Pascal Becker | 20. 02. 2021 | 1
Geochronology „Field of scientific investigation concerned with determining the age and history of Earth’s rocks and rock assemblages” (https: //www. britannica. com/science/geochronology (last checked: 12. 11. 18)) 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 Picture reference: http: //learnodo-newtonic. com/wp-content/uploads/2013/07/Earth-Theia-collision. jpg Picture reference: https: //www. planet-wissen. de/geschichte/archaeologie/mumien-oetzi-100~_v. Picture reference: http: //eatrio. net/wp-content/uploads/2013/01/7. -Pangea_continents_and_oceans. jpg Picture reference: https: //2. bp. blogspot. com/gseagaleriexl. jpg (12. 11. 18) https: //upload. wikimedia. org/wikipedia/commons/8/8 a/Stromatolithe_Pal%C 3%A 9 oarch%C 3%A 9 en_6 Wd. Ycjamll 4/V 57 t. T 7 x 21 f. I/AAAABt. Q/9 x. Ti. EOE 1 FS 8 YYa. SJANILz. X 2 YVHa 3 h 30 KQCLc. B/s 1600/dino _MNHT. PAL. 2009. 10. 1. jpg (12. 11. 18) saur-extinction. jpg (12. 11. 18) Lena Bastian / Pascal Becker | 20. 02. 2021 | 2
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 Sr. SO 4 and Strontianite Sr. CO 3 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 https: //www. britannica. com/science/dating-geochronology/Rubidium-strontium-method#ref 69774 (12. 11. 18) Ulmer, P. Vulkane und Magmatismus Course FS 2016, ETH Zurich. Lena Bastian / Pascal Becker | 20. 02. 2021 | 3
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 | 20. 02. 2021 | 4
Isochron y = b + x m Assumptions: • • • Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich Isotopically homogeneous melt Closed system Cogenetic samples Lena Bastian / Pascal Becker | 20. 02. 2021 | 5
Isochron Weighted regression: Goodness of fit: Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich Lena Bastian / Pascal Becker | 20. 02. 2021 | 6
Rb – Sr system: Advantages and Disadvantages Advantages 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 Lena Bastian / Pascal Becker | 20. 02. 2021 | 7
Other important decay systems § § § U – Th – Pb Sm – Nd Lu – Hf K – Ar 14 C dating Lena Bastian / Pascal Becker | 20. 02. 2021 | 8
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 Lena Bastian / Pascal Becker | 20. 02. 2021 | 9
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 Picture reference: https: //upload. wikimedia. org/wikipedia/commons/c/c 2/Illustration_of_isotope_dilution_analysis_with_fish_counting_in_lakes. jpg (12. 11. 18) Lena Bastian / Pascal Becker | 20. 02. 2021 | 10
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 | 20. 02. 2021 | 11
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 | 20. 02. 2021 | 12
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 | 20. 02. 2021 | 13
Moldovan, M. , J. Anal. At. Spectrom. , 2004, 19, 815– 822 Lena Bastian / Pascal Becker | 20. 02. 2021 | 14
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 | 20. 02. 2021 | 15
Cavity Ring Down Spectroscopy (Taken from Master Course: Experimental Techniques at vrije universiteit amsterdam) Lena Bastian / Pascal Becker | 20. 02. 2021 | 16
Cavity Ring Down Spectroscopy Rok Zaplotnik et al, 2015, Plasma Sources Sci. Technol. , 24 Lena Bastian / Pascal Becker | 20. 02. 2021 | 17
Laser Ablation Molecular Isotope Spectrometry Russo, R. , Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 66, Issue 2, 2011, Pages 99 -104 Lena Bastian / Pascal Becker | 20. 02. 2021 | 18
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 Lena Bastian / Pascal Becker | 20. 02. 2021 | 19
Data evaluation Lena Bastian / Pascal Becker | 20. 02. 2021 | 20
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 | 20. 02. 2021 | 21
Isotope Maps Lena Bastian / Pascal Becker | 20. 02. 2021 | 22
Isotope Maps Bowen, G. , Annu. Rev. Earth Planet. Sci. 2010. 38: 161– 87 Lena Bastian / Pascal Becker | 20. 02. 2021 | 23
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Analytical Procedure: Samples § § Hair Finger/Toe nails Teeth (Tooth enamel) Bones (Femur shaft/bio-apatite, Rib bone/collagen) Lena Bastian / Pascal Becker | 20. 02. 2021 | 25
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 Lena Bastian / Pascal Becker | 20. 02. 2021 | 26
Analytical Procedure: Measurement § Use of TIMS for Sr and Pb § Use of IRMS for C, N and O Lena Bastian / Pascal Becker | 20. 02. 2021 | 27
Analytical Procedure: Data Evaluation Lena Bastian / Pascal Becker | 20. 02. 2021 | 28
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The Result Lena Bastian / Pascal Becker | 20. 02. 2021 | 31
Thank you for your attention! Lena Bastian / Pascal Becker | 20. 02. 2021 | 32
