Fractionation of stable isotopes

Why can one assume that the isotopic compositions of elements on the Earth are representative of the bulk solar system This was not obvious in the beginning. Isotope-ratio measurements of meteorites made in the late 1950s appeared to show significant variations. However, within a few years, it was shown that those variations were due almost entirely to problems with the measurements, not to real variations in the samples. By the early 1960s enough measurements had been made to convince most scientists that in the material to which they had access, terrestrial rocks and meteorites, each element always had the same isotopic composition (except for small fractionations of stable isotopes and shifts... 

The fractionation of stable isotopes between two substances A and B can be expressed by use of the isotope fractionation factor alpha (a),... 

Stable isotope effect studies carried out during 1972-1992 concerning correlation of IEs with molecular forces and molecular structures, correlation of zero-point energy and its IEs with molecular forces and molecular structure, vapour pressure isotope effects and fractionation of stable isotopes have been reviewed466. 

Over the last 30 years the study of the stable isotope composition of carbonates has been one of the more active areas of research in carbonate geochemistry. These studies have particular application to later discussion of carbonate diagenesis and historical geochemistry of carbonate rocks. Many of the same considerations involved in understanding elemental distribution coefficients apply to the fractionation of stable isotopes. Consequently, we have included a discussion of the chemical principals associated with isotope behavior in this chapter. Only a relatively brief summary of these basic chemical considerations will be presented here, because recent books and extensive reviews are available on this topic (e.g., Arthur et al., 1983 Hoefs, 1987). Also, our discussion will be restricted to carbon and oxygen isotopes, because these isotopes are by far the most important for the study of carbonate geochemistry. The principles, however, apply to other stable isotopes (e.g., sulfur). 

The distribution of chemical species in waters and sediments is strongly influenced by an interaction of mixing cycles and biological cycles (Buffle and DeVitre, 1994). Radioisotope measurements may often be used to establish the time scale of some of these processes. Similarly, evaluation of the fractionation of stable isotopes aids in the quantitative interpretation of biogeochemical and environmental processes and cycles. 

Chebotarev, E.N., Matrosov, A.G., Kudryavtseva, A.I., Zyakun, A.M. and Ivanov, M.V., 1975. Fractionation of stable isotopes during microbiological processes in Slavonic lakes. Microbiology, 44 268—271. 

Kaplan, I.R. and Rafter, T.A., 1958. Fractionation of stable isotopes of sulfur by Thio-bacilli. Science, 127 517. 

Mekhtieva, V.L. and Kondrat eva, E.N., 1966. Fractionation of stable isotopes of sulfur by photosynthesizing purple bacteria Rhodopseudomonas sp. Dokl. Akad. Nauk SSSR, 166 465—468. 

Guy, R. D., M.L. Fogel and J.A. Berry (1993) Photos5nithetic fractionation of stable isotopes of oxygen and carbon. Plant Physiol. 101, 37-47. 

Fractionation factor (a) In any process involving the fractionation of stable isotopes x and y (where y is the heavier isotope), such as the transformation of substance A to substance B, a defines the relative abundance of the isotopes in A and B ... 

Macko, S.A., Estep, M.L.E., Engel, M.H. and Hare, RE. 1986 Kinetic fractionation of stable nitrogen isotopes during amino acid transamination. Geochimica et Cosmochimica Acta 50 2143-2146. 

Farquhar, G.D., Hubick, K.T., Condon, A.G. Richards, R.A. (1988). Carbon isotope fractionation and plant water-use efficiency. In Applications of Stable Isotope Ratios to Ecological Research, ed. P.W. Rundel, J.R. Ehleringer K.A. Nagy, pp.21 0. New York Springer-Verlag. 

Elements such as C, N, O, S, and Cl that are components of many organic compounds exist naturally as mixtures of stable isotopes. The ratios of these in a compound reflect the different rates of reaction at isotopically labeled positions, and therefore reflect the fractionation—biotic or abiotic—by which it was synthesized or to which the compound has been subjected. Techniques have been developed whereby the ratios C/ C (5 C), (5 N), (5 0),... 

Friedman I, O Neil JR (1977) Compilation of stable isotope fractionation factors of geochemical interest. U S Geol Surv Prof Paper 440-KK... 

Calcium carbonate is also the main constituent of the shells of sea animals, which make their shells from elements acquired from the surrounding waters. Now, the degree of fractionation of the oxygen isotopes as well as the formation of mineral carbonates and of animal shells in sea waters are determined on the basis of the temperature-dependent fractionation of the isotopes of oxygen the oxygen isotope composition of these materials reflects, therefore, the temperature at the time of their formation. Thus determining the isotope ratio between the stable isotopes of oxygen... 

Bell, L.S., Cox, G. and Sealy, J. (2001). Determining isotopic life history trajectories using bone density fractionation and stable isotope measurements a new approach. American Journal of Physical Anthropology 116 66-79. 

Hayes, J.M. 2001. Fractionation of the isotopes of carbon and hydrogen in biosynthetic processes. Pp. 225-278, in Stable Isotope Geochemistry Reviews in Mineralogy and Geochemistry, J.W. Valley and D.R. Cole, eds., Washington, D.C. Mineralogical Society of America. 

Fortier SM, Cole DR, Wesolowski DJ, Riciputi LR, Paterson BA, Valley JW, Horita J (1995) Determination of the magnetite-water equilibrium oxygen isotope fractionation factor at 350°C a comparison of ion microprobe and laser fluorination techniques. Geochim Cosmochim Acta 59 3871-3875 Friedman I, O Neil JR (1977) Compilation of Stable Isotope Fractionation Factors of Geochemical Interest. US Geol Surv Prof Paper 440-KK... 

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