Dating of a lunar rock sample (77215) Carlson RW, Phil. Trans. R. Soc., 2014, 372 Lena Bastian / Pascal Becker 22.05.2019

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: https://2.bp.blogspot.com/-6WdYcjamll4/V57tT7x21fI/AAAAAAAABtQ/9xTiEOE1FS8YYaSJANILzX2YVHa3h30KQCLcB/s1600/dinosaur-extinction.jpg (12.11.18) Picture reference: https://www.planet-wissen.de/geschichte/archaeologie/mumien/mumien-oetzi-100~_v-gseagaleriexl.jpg (12.11.18) Picture reference: https://upload.wikimedia.org/wikipedia/commons/8/8a/Stromatolithe_Pal%C3%A9oarch%C3%A9en_-_MNHT.PAL.2009.10.1.jpg (12.11.18) Picture reference: http://learnodo-newtonic.com/wp-content/uploads/2013/07/Earth-Theia-collision.jpg (12.11.18) Picture reference: http://eatrio.net/wp-content/uploads/2013/01/7.-Pangea_continents_and_oceans.jpg (12.11.18) Lena Bastian / Pascal Becker 22.05.2019

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 https://www.britannica.com/science/dating-geochronology/Rubidium-strontium-method#ref69774 (12.11.18) Ulmer, P. Vulkane und Magmatismus Course FS 2016, ETH Zurich. Lena Bastian / Pascal Becker 22.05.2019

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 22.05.2019

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 22.05.2019

Isochron Weighted regression: Goodness of fit: Vance, D. Isotopengeochemie und Isotopengeologie HS 2017, ETH Zurich Lena Bastian / Pascal Becker 22.05.2019

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 Lena Bastian / Pascal Becker 22.05.2019

Other important decay systems U – Th – Pb Sm – Nd Lu – Hf K – Ar 14C dating Lena Bastian / Pascal Becker 22.05.2019

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 22.05.2019

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/c2/Illustration_of_isotope_dilution_analysis_with_fish_counting_in_lakes.jpg (12.11.18) Lena Bastian / Pascal Becker 22.05.2019

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 22.05.2019

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 22.05.2019

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 22.05.2019

Moldovan, M. , J. Anal. At. Spectrom., 2004, 19, 815–822 Lena Bastian / Pascal Becker 22.05.2019 Moldovan, M. , J. Anal. At. Spectrom., 2004, 19, 815–822

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 22.05.2019

Cavity Ring Down Spectroscopy Lena Bastian / Pascal Becker 22.05.2019 (Taken from Master Course: Experimental Techniques at vrije universiteit amsterdam)

Cavity Ring Down Spectroscopy Lena Bastian / Pascal Becker 22.05.2019 Rok Zaplotnik et al, 2015, Plasma Sources Sci. Technol.,24

Laser Ablation Molecular Isotope Spectrometry Lena Bastian / Pascal Becker 22.05.2019 Russo, R., Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 66, Issue 2, 2011, Pages 99-104

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 22.05.2019

Data evaluation Lena Bastian / Pascal Becker 22.05.2019

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 22.05.2019

Isotope Maps Making use of δ 13 𝐶, δ 15 𝑁, δ 18 𝑂, 87 𝑆𝑟 86 𝑆𝑟 , 206 𝑃𝑏 204 𝑃𝑏 , 207 𝑃𝑏 206 𝑃𝑏 δ 13 𝐶= 13 𝐶 12 𝐶 𝑆𝑎𝑚𝑝𝑙𝑒 13 𝐶 12 𝐶 𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 −1 ∗1000 ‰ Lena Bastian / Pascal Becker 22.05.2019

Isotope Maps Bowen, G., Annu. Rev. Earth Planet. Sci. 2010. 38:161–87 Lena Bastian / Pascal Becker 22.05.2019 Bowen, G., Annu. Rev. Earth Planet. Sci. 2010. 38:161–87

Lena Bastian / Pascal Becker 22.05.2019

Analytical Procedure: Samples Hair Finger/Toe nails Teeth (Tooth enamel) Bones (Femur shaft/bio-apatite, Rib bone/collagen) Lena Bastian / Pascal Becker 22.05.2019

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 22.05.2019

Analytical Procedure: Measurement Use of TIMS for Sr and Pb Use of IRMS for C,N and O Lena Bastian / Pascal Becker 22.05.2019

Analytical Procedure: Data Evaluation Lena Bastian / Pascal Becker 22.05.2019

Lena Bastian / Pascal Becker 22.05.2019

Lena Bastian / Pascal Becker 22.05.2019

The Result Lena Bastian / Pascal Becker 22.05.2019

Thank you for your attention! Lena Bastian / Pascal Becker 22.05.2019