Isotope fractionation factor

Wong, W.W., Cochran, W.J., Klish, W.J., Smith, E.O.B., Lee, L.S. and Klein, P.D. 1988 In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide. American Journal of Clinical Nutrition 47 1-6. 

Oxygen isotopic fractionation factors used for the calculation were taken from Taylor (1997). Initial 8 0 value of hydrothermal solution (0%o) was estimated from 8 0 values of K-feldspar and quartz in the veins and homogenization temperatures (Shikazono and Nagayama, 1993), and that of groundwater (—7%c) was estimated from meteoric water value of the south Kyushu district (—7%c) (Matsubaya et al., 1975). 

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

The isotope fractionation factor and mass-dependency of fractionation... 

Figure 5. Examples of predicted and measured isotopic fractionations for O, Cr, Fe, and Cl, as cast in the traditional lO lna. g - lO / P diagram. The quantity lO lna. g places the isotope fractionation factor in units of per mil (%o).

The products of Rayleigh fractionation are effectively isolated from isotopic exchange with the rest of the system immediately upon formation. If the process occurs slowly, such that each increment of product B forms in isotopic equilibrium with the reactant A prior to isolation of B from the system, then would be an equilibrium isotope fractionation factor. However, if the process of formation of B is rapid, incremental formation of B may be out of isotopic equilibrium withH. In this case, would be a kinetic isotope fractionation factor, which may be a function of reaction rates or other system-specihc conditions. 

In addition to providing the means for calculating the isotopic compositions of ancient fluids based on analysis of minerals, mineral-fluid isotope fractionation factors provide an opportunity to combine fractionation factors when there is a common substance such as water. A fundamental strategy for compiling databases for isotopic fractionation factors is to reference such factors to a common substance (e.g., Friedman and O Neil 1977). For example, the quartz-water fractionation factor may be combined with the calcite-water fractionation factor to obtain the quartz-calcite fractionation factor at some temperature. It is now recognized, however, that the isotopic activity ratio of water in a number of experimental determinations of mineral-fluid fractionation factors has been variable, in part due to dissolution of... 

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... 

The isotope fractionation factor for isotopes (light) and (heavy) between two substances X4 sm XB is usually expressed in terms of a ... 

Density functional theory has been extensively used to calculate vibrational properties of minerals and other crystalline phases in addition to molecules and molecule-like substances. This method has recently begun to be used to calculate isotope fractionation factors (Schauble et al. in press Anbar et al. in press), and shows great potential for future research. Programs such as ABINIT (Gonze et al. 2002), pwSCF (Baroni et al. 2001)—both freely available—and the commercial package CASTEP (Accelrys, Inc.) can be used to calculate vibrational properties of crystals. 

The previous equations do not require that the isotopic ratio used for normalization (x-axis) and the ratio to be measured (y-axis) have to be for the same element. It is therefore possible to normalize the isotopic composition of Cu to that of a standard Zn solution without any assumption made on the particular mass-fractionation law. The original formulation of this property by Longerich et al. (1987) calls for identical isotopic fractionation factors for the two elements, but this is not at all a necessary constraint and Albarede et al. (2004) show that, in fact, this very assumption may lead to significant errors. For a Cu sample mixed with a Zn standard, in which the Zn/ Zn ratio of the standard solution is used for normalization, we obtain the expression ... 

Kinetic isotope fractionation obeys a different fractionation law. Young et al. (2002b) showed recently that kinetic processes, again written here in terms of the two Mg isotope fractionation factors, obey the relation... 

In the earliest work, Krouse and Thode (1962) found the Se isotope fractionation factor Sse(iv)-se(o) to bc 10%o ( l%o) with hydroxylamine (NH2OH) as the reductant. Rees and Thode (1966) obtained a larger value, 12.8%o, for reduction by ascorbic acid. Webster (1972) later obtained 10%o for NHjOH reduction. Rashid and Krouse (1985) completed a more detailed study, and found that the fractionation factor varied with time over the course of the experiments. They explained the variations observed among the experiments in all four studies using a model in which reduction consists of two steps. With the rate constant of the second step two orders of magnitude smaller than the first, and kinetic isotope effects of 4.8%o and 13.2%o for the hrst and second steps, respectively, all the data (Table 3) were fit. Thus, kinetic isotope effects of apparently simple abiotic reactions can depend on reaction conditions. 

Figure 13. Plot of lO lnaA-B values versus lOVT (T in K) for inter-mineral fractionation between magnetite-olivine, orthopyroxene-olivine, and clinopyroxene-olivine, and Fe metal-olivine as calculated from spectroscopic data by Polyakov and Mineev (2000), and as measured from natural samples by Zhu et al. (2002), Beard and Johnson (2004). Also shown is the Fe isotope fractionation factor between magnetite and Fe-silicates measured by Berger and von Blanckenburg (2001).

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