Isotope fractionation crystal structure

Young SE (2003) Crystal chemical control on intra-structural Cu isotope fractionation in natural Cu-(Ee)-S minerals. PhD Mem. Univ. Arizona... 

Isotope fractionations in solids depend on the nature of the bonds between atoms of an element and the nearest atoms in the crystal structure (O Neil 1986). The correlation between bond strength and oxygen isotope fractionation was investigated by Schiitze (1980), who developed an increment method for predicting oxygen isotope fractionations in silicate minerals. Richter and Hoemes (1988) applied this method to the calculation of oxygen isotope fractionations between silicate minerals and... 

This order of decreasing 0-contents has been explained in terms of the bond-type and strength in the crystal structure. Semi-empirical bond-type calculations have been developed by Garlick (1966) and Savin and Lee (1988) by assuming that oxygen in a chemical bond has similar isotopic behavior regardless of the mineral in which the bond is located. This approach is useful for estimating fractionation... 

Zheng YF (1993a) Oxygen isotope fractionation in Si02 and Al2Si05 polymorphs effect of crystal structure. Eur J Miner 5 651-658... 

Large instrumental mass fractionations have been observed during measurements of oxygen isotope ratios on Fe-Mg-Ca garnets in SIMS.83 Part of this fractionation depends on crystal structure and mineral composition. 

Heavy isotopes are concentrated in more closely packed crystal structures. The fractionation of carbon isotopes between diamond and graphite is well known and there are smaller changes between calcite and aragonite. There is a also a smalt change in 0 between a- and p-quartz. 

Matsuhisa Y., Goldsmith J.R. and Clayton R.N., 1979, Oxygen isotope fractionation in the systems quartz-albite-anorthite-water. Geochim. Cotmor/iini. Acta 43, 1131-1140. Matsui A., Onuma N., Nagasawa H, Hlguchi H. and Banno S., 1977, Crystal structure control in trace element partition between crystal and magma. BulL Sac. Fr. Mineral. 

The theory developed for perfect gases could be extended to solids, if the partition functions of crystals could be expressed in terms of a set of vibrational frequencies that correspond to its various fundamental modes of vibration (O Neil 1986). By estimating thermodynamic properties from elastic, structural, and spectroscopic data, Kieffer (1982) and subsequently Clayton and Kieffer (1991) calculated oxygen isotope partition function ratios and from these calculations derived a set of fractionation factors for silicate minerals. The calculations have no inherent temperature limitations and can be applied to any phase for which adequate spectroscopic and mechanical data are available. They are, however, limited in accuracy as a consequence of the approximations needed to carry out the calculations and the limited accuracy of the spectroscopic data. 

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