Chapter 8 · Low-Temperature Minerals, Exclusive of Carbonates

Problem set · Sharp, Principles of Stable Isotope Geochemistry, 1st ed. (2007) · Answers →

Problem 1

  1. From the kaolinite fractionation line in Figure 8.12, calculate the αkaolinite–water value for both oxygen and hydrogen.
  2. On the basis of elementary fractionation relations, do mixed kaolinite–montmorillonite samples form at lower or higher temperatures than pure kaolinite and montmorillonite?

Problem 2

The box model for describing the δ18O value of an animal’s body water (Fig. 8.4) provides an explanation for the correlation between local meteoric water and drinking water having a slope less than unity. Construct a similar model for hydrogen isotopes. What slope would you predict?

Problem 3

When Kolodny et al. (1983) measured fish bones in Lake Baikal, they found that the δ18O values of the bones varied from 6.3‰ near the surface to 9.2‰ in the deepest levels. Assuming that the δ18O value of the lake is constant, what temperature change is there between the highest and lowest sampling levels in their study?

Problem 4

A kangaroo rat can derive all of its water by metabolizing food, so-called metabolic water. If the kangaroo rat oxidizes carbohydrates (general formula (CH2O)n), how will the δ18O of its body water change as a function of the δ18O of local meteoric water? Assume that the ingested carbohydrates have a δ18O value similar to that of the local meteoric water. [The carbohydrate formula is lost in the extraction; (CH2O)n reconstructed.]

Problem 5

In the Southern Arizona desert, kangaroo rats have δ13C values in one range, whereas other granivorous rodents have values spanning a different range (VPDB) (Smith et al., 2002). What would you conclude about the diet of the kangaroo rats vs. those of other rodents? check vs print [The two printed value ranges are lost in the extraction.]

Problem 6

Why would the D/H ratio of pore waters decrease with depth, while the 18O/16O ratio for the same waters increases with depth?

Transcribed from Z. Sharp, Principles of Stable Isotope Geochemistry, 1st ed. (Pearson Prentice Hall, 2007), end-of-chapter problem set (published source). Reference-scale names are written VSMOW, VPDB and VCDT where the original used SMOW, PDB and CDT, with the original numerical constants unchanged; historical usages (e.g. Craig's definition of SMOW) are kept as printed.

The source PDF's text layer scrambles mathematics, so equations and some values were reconstructed during transcription. Bracketed notes and anything tagged reconstructed or check vs print are editorial (constructed), not part of the original, and the warn-tagged items should be verified against the print copy.