Research Collection Habilitation Thesis Radium isotope systematics in nature: applications in geochronology and hydrogeochemistry Author(s): Eikenberg, Jost Publication Date: 2002 Permanent Link: https://doi.org/10.3929/ethz-a-004444917 Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library Radium Isotope Systematics in Nature: Applications in Geochronology and Hydrogeochemistry by JOST EIKENBERG Division for Radiation Protection and Safety Paul Scherrer Institute CH-5232 Villigen (PSI), Switzerland Habilitation Thesis, Earth Science Department Swiss Federal Institute of Technology (ETH) Zürich Villigen, November 2002 ii The author acknowledges very much the kind help, support and all the discussions with the supervisor of this habilitation thesis, Professor Dr. A. Halliday, Director of the Radiogenic Isotope Geochemistry at the Swiss Federal Institute of Technology (ETH) Zürich. iii TABLE OF CONTENTS Summary ..................................................................................................................vii 1. HISTORICAL BACKGROUND......................................................................1 2. INTRODUCTION..............................................................................................1 3. U/Th decay series Relationships .......................................................................4 3.1 The U/Th Decay Series Sequences................................................ 4 3.1.1 Uranium-Series..................................................................................................... 5 3.1.2 Thorium-Series..................................................................................................... 8 3.2 Natural Terrestrial Occurrences of U, Th and Ra........ 9 3.2.1 Rock Samples........................................................................................................ 9 3.2.2 Aqueous Samples.............................................................................................. 10 3.3 Geochemical Behaviour of the U- and Th-Series Members in the Aquatic Environment................................... 10 3.3.1 Uranium ................................................................................................................. 10 3.2.2 Thorium.................................................................................................................. 11 3.2.3 Radium.................................................................................................................... 12 3.2.4 Radon ...................................................................................................................... 14 3.2.5 Lead.......................................................................................................................... 14 3.2.6 Polonium................................................................................................................ 14 4. Radioactive transformations.............................................................15 4.1 Modes of Radioactive Decay............................................................ 15 4.1.1 -Particle Radiation......................................................................................... 15 4.1.2 -Particle Radiation ......................................................................................... 20 4.1.3 - and X-Ray Radiation.................................................................................. 21 4.2 Decay Laws: Radionuclide Disequilibrium........................ 23 4.2.1 Nuclear Decay and Specific Activity...................................................... 23 4.2.2 Radionuclide Disequilibrium ...................................................................... 24 5. COUNTING Measurement techniques.......................................31 5.1 Introduction.................................................................................................... 31 5.2 Semiconductive Detectors .................................................................. 32 5.2.1 Principle ................................................................................................................. 32 5.2.2 -Spectrometry................................................................................................... 33 5.2.3 -Spectrometry.................................................................................................... 35 5.3 Scintillation Detectors ........................................................................... 37 5.3.1 -Liquid Scintillation Spectrometry ................................................... 37 iv 5.3.2 NaI(Tl)-Detectors.............................................................................................. 40 5.4 Ionisation Detectors: -Proportional Counting........ 42 5.5 Activity and Detection Limit Calculations ......................... 42 5.5.1 Activity Calculations....................................................................................... 42 5.5.2 Detection Limit Calculations....................................................................... 43 5.6 Improvement of Counting Sensitivity ..................................... 45 6. Radiochemical Separation Methods ................................................48 6.1 Isotope Spiking............................................................................................. 48 6.1.1 U and Th-Series Tracers for -Spectrometry: Overview.............. 48 232 228 224 6.1.2 The U/ Th/ Ra Secular Equilibrium Spike for 234 230 226 U/ Th/ Ra -Dating ................................................................................ 51 6.2 Determination of U, Th, Ra and Pb/Po in Rocks .......... 52 6.2.1 Overview ............................................................................................................... 52 6.2.2 Sample Dissolution .......................................................................................... 53 6.2.3 Separation Procedure for Uranium and Thorium.............................. 54 6.2.4 Separation Procedure for Radium............................................................. 55 6.2.5 Separation Procedure for Lead/Polonium............................................. 56 6.3 Determination of U, Pb and Po in Aqueous Samples 58 6.3.1 Introduction.......................................................................................................... 58 6.3.2 Separation Procedure for Uranium........................................................... 58 6.3.3 Separation Procedure for Lead and Polonium.................................... 60 6.4 Development of a Procedure for Determination of Ra- Isotopes in Aqueous Samples .......................................................... 61 6.4.1 Summary................................................................................................................ 61 6.4.2 Introduction.......................................................................................................... 61 6.4.3 Experimental........................................................................................................ 63 6.4.4 Results and Discussion................................................................................... 65 6.4.5 Conclusions and Recommendations........................................................ 78 7. U/Th/Ra-disequilibrium for dAting Pleistocene events .....79 7.1 The U-Th-Series Dating Methods ............................................... 79 7.1.1 Introduction.......................................................................................................... 79 230 234 238 7.1.2 The Th/ U/ U Chronometer............................................................. 81 226 234 226 226 7.1.3 The Ra/ U or Raex/ Ra(0) Chronometer ............................... 83 7.2 U-Series Isochron Dating.................................................................... 84 7.2.1 Principle ................................................................................................................. 84 7.2.2 Isochron Dating in Sedimentology........................................................... 85 7.2.3 Isochrone Dating in Volcanology............................................................. 87 v 8. U/Th/Ra-Dating of Sedimentary Systems: Speleothem and Corals .............................................................................................................90 230 234 226 226 8.1 Th/ U and Ra/ Ra(0) Dating of a Freshwater Limestone Cave in Central Switzerland ............................... 90 8.1.1 Summary................................................................................................................ 90 8.1.2 Introduction.......................................................................................................... 90 8.1.3 Geological Setting ............................................................................................ 91 8.1.4 Chemical Formation of the Flowstone Complex............................... 92 8.1.5 Sampling Strategy and Sample Preparation......................................... 93 8.1.6 Analytical Techniques .................................................................................... 95 8.1.7 Dating Principles ............................................................................................... 97 8.1.8 Results and Discussion..................................................................................