Part 11- Stable Isotope Geochemistry Flashcards Preview

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Flashcards in Part 11- Stable Isotope Geochemistry Deck (11):
0

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.

1

What elements are most commonly studied in SIG?

Light elements (amu < 40)

2

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.

3

What is SMOW? What is it used for?

Standard Mean Ocean Water.

Used as a standard for O isotope variations.

4

What is the symbol for fractionation factor?

Alpha (a).

5

What equation defines the fractionation factor?

a = RA/RB

RA = isotope ratio of reservoir A
RB = isotope ratio of reservoir B

6

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

7

What is the primary reason for the occurrence of of equilibrium isotope fractionation?

Vibrational energy of molecules and the discrete vibrational energy levels.

8

If the ground state of a given bond is a lower energy level is the bond more or less stable?

More stable.

9

Why do kinetic isotope effects often occur in nature?

Many reactions in nature never achieve equilibrium because-
Too slow OR
Products removed

10

How is the kinetic isotope fractionation factor calculated?

The ratio of the isotopic velocities.