Part 11- Stable Isotope Geochemistry Flashcards
What elements are most commonly studied in SIG?
Light elements (amu < 40)
What is stable isotope geochemistry based on?
The fact that isotopes of the same element display small differences in their behaviour durning phys, chem, and bio processing.
What amounts are stable isotope variations generally quoted in?
Parts per thousand but tend to be quoted as deviations from a given isotope standard IN DELTA NOTATION.
What is SMOW? What is it used for?
Standard Mean Ocean Water.
Used as a standard for O isotope variations.
What is the symbol for fractionation factor?
Alpha (a).
What equation defines the fractionation factor?
a = RA/RB
RA = isotope ratio of reservoir A RB = isotope ratio of reservoir B
What are the two principal pathways to stable isotope variation? Describe them.
Equilibrium- effects arise from reversible isotope exchange reactions.
Kinetic- effects associated with irreversible, incomplete reactions. E.g. Diffusion
What is the primary reason for the occurrence of of equilibrium isotope fractionation?
Vibrational energy of molecules and the discrete vibrational energy levels.
If the ground state of a given bond is a lower energy level is the bond more or less stable?
More stable.
Why do kinetic isotope effects often occur in nature?
Many reactions in nature never achieve equilibrium because-
Too slow OR
Products removed
How is the kinetic isotope fractionation factor calculated?
The ratio of the isotopic velocities.
