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Indian Institute of Science Education and Research Bhopal

EES 601: Isotope Geochemistry (4)

Learning Objectives:

Isotope geochemistry is a powerful tool to explore a number of earth surface processes in both modern and ancient earth and environmental systems. Recycling of various elements in the Earth’s upper crust, hydrosphere and atmosphere through various biogeochemical processes alters their physical states; however their isotope compositions still retain clues on their source signatures and quantitative information on these cycling processes. Under closed system conditions, radiogenic isotopes additionally act as time clocks. This course enables students to understand the evolutionary trajectories of various physical, chemical, biological processes in Earth systems.

Course Contents:

Isotopes and Radioactivity:
Basics of atomic and nuclear physics; Synthesis, relative abundances and stability of various nuclides; Radioactivity, radioactive decay modes; Radiation detection and environmental protection.

Instrumentation:
Alpha, beta, gamma counters; Mass spectrometers; Methods of internal spike addition, isotope dilution and standard sample bracketing; Isotope fractionation correction by single/double normalization and double/triple isotope spiking.

Isotope Dating:
Growth and decay of radiogenic daughters; Basic assumptions of dating; Isochron dating, and related analytical uncertainties and geological errors; Dating using radioactive parent only (¹⁰Be, ¹⁴C and ³⁶Cl), parent–daughter couple (⁴⁰K–⁴⁰Ar, ⁸⁷Rb–⁸⁷Sr, ¹⁴⁷Sm–¹⁴³Nd, ¹⁷⁶Lu–¹⁷⁶Hf, ¹⁸⁷Re–¹⁸⁷Os, ²³⁸U–²⁰⁶Pb), decay series disequilibria (²³⁸U–²³⁴U–²³⁰Th–²³⁶Ra), radiogenic daughter only (Pb–Pb and Ar–Ar) and extinct parent (²⁶Al, ⁴¹Ca, ⁵³Mn, ⁶⁰Fe, ¹⁰⁷Pd, ¹²⁹I, ¹⁴⁶Sm, ¹⁸²Hf); Ages of crystallization and last metamorphism; Sediment depositional ages; Model ages; Exposure ages; Archaeological ages.

Radiogenic Isotope Geochemistry:
Compatibility; Crust–mantle differentiation; Crustal evolution; Crust recycling in subduction zones; Pb-paradox; Chemical weathering versus physical erosion; Mixing theory; Sediment provenance; Zircon effect; Ocean circulation; Strantium isotope chronostratigraphy.

Stable Isotope Geochemistry:
Mass dependent and independent isotope fractionations; Use of traditional and non-traditional stable isotopes in exploration of Earth’s climate, hydrology, oceanography, and other biogeochemical processes, Evolution of atmospheric gases.

Noble Gas Geochemistry:
Production and abundance; Isotope composition and behavior of noble gases; Noble gas–water interactions; Cycling in continental and oceanic crusts; Applications in oceanography and terrestrial rocks.

Suggested Readings :

1. Allègre, C. J., 2005, Isotope Geology, Cambridge University Press.
2. Faure, G., and Mensing, T. M., 2004, Isotopes – Principles and Applications, Wiley.
3. White, W. M., 2015, Isotope Geochemistry, Wiley-Blackwell.
4. Holland, H. D., and Turekian, K. K., 2011, Tretise or Geochemistry (2^nd Edition), Elsevier Science.
5. Zeebe, R. E., and Wolf-Gladrow, D., 2001, CO₂ in Seawater: Equilibrium, Kinetics and Isotopes (1^st Edition), Elsevier Science.
6. Hoefs, J., 2015, Stable Isotope Geochemistry (7^th Edition), Springer.

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