Isotopic correlations

Yoshida, N. and Miyazaki, N. 1991 Oxygen isotope correlation of cetacean bone phosphate with environmental water. Journal of Geophysical Research 96 815-820. 

Figure 6. Three-isotope correlation diagram for Mg using S-notation fsee text) for unnormalized data from terrestrial samples and Mg-rich Allende minerals.

Sarda, P., Moreira, M., Staudacher, Th. (1999) Argon-lead isotope correlation in mid-Atlantic Ridge basalts. Science, 283, 666-9. 

Figure 12 Chemical and isotopic correlations among shergottites, arising from assimilation of a crustal component. Decreasing values of 5 " Nd indicate increasing assimilation. This parameter correlates with magma redox state, indicated by size of the Eu anomaly in pyroxenes (Wadhwa, 2001), and ratio of light-to-heavy rare-earth elements (after McSween, 2002).

Figure 13 Isotopic composition of C (lull etai, 1997) and O (Valley etal., 1997 Leshin etal., 1998) in carbonates of the ALH84001 martian meteorite. Heavy isotopes correlate with the Mg content of the carbonate.

Figure 3 Crust-mantle differentiation patterns for the decay systems Rb-Sr, Sm-Nd, Lu-Hf, and Re-Os. The diagram illustrates the depletion-enrichment relationships of the parent-daughter pairs, which lead to the isotopic differences between continental crust and the residual mantle. For example, the Sm/Nd ratio is increased, whereas the Rb/Sr ratio is decreased in the residual mantle. This leads to the isotopic correlation in mantle-derived rocks plotted in Figure 4(a). The construction is similar to that used in Figure 2, but D values have been adjusted slightly for greater clarity.

Burnard P. (1999) Origin of argon-lead isotopic correlations in basalts. Science 286, 871. 

Sarda P., Moreira M., and Staudacher T. (1999) Argon—lead isotopic correlation in Mid-Atlantic ridge basalts. Science 283, 666-668. 

Allegre C. J., Othman D. B., Polve M., and Richard P. (1979) The Nd-Sr isotopic correlation in mantle materials and geodynamic consequences. Phys. Earth Planet. Inter. 19, 293-306. 

Weaver B. L. and Tarney J. (1980) Continental crust composition and nature of the lower crust constraints from mantle Nd-Sr isotope correlation. Nature 286, 342-346. 

An outstanding question is how much of the mantle still maintains high volatile concentrations. This involves resolution of the nature of the high He/" He OIB-source region. Most models equate this with undepleted, undegassed mantle, although some models invoke depletion mechanisms. However, none of these has matched the end-member components seen in OIB lithophile isotope correlations. It remains to be demonstrated that a primitive component is present and so can dominate the helium and neon isotope signatures in OIB. The heavy-noble-gas characteristics in OIB must still be documented. It is not known to what extent major volatiles are stored in the deep Earth and associated with these noble gas components. 

Chauvel, C., Dupre, B. Arndt, N. T. 1993. Pb and Nd isotopic correlation in Belingwe komatiites and basalts. In Bickle, M. J. Nisbet, E. G. (eds) The Geology of the Belingwe Greenstone Belt, Zimbabwe - a Study of the Evolution of Archaean Continental Crust. Geological Society of Zimbabwe Special Publication, 2, 167-174. 

Mass Spectrometric Determination of Intermolecular and Intramolecular Isotopic Correlations... 

The intrinsic or intermolecular standardisation (evaluation of isotopic correlations in between molecules of the same origin) demands the separation, purification and isotopic analysis of at least two components of the same source, which is, in practice of routine analysis of flavourings, normally only realisable by GC-C-IRMS or by multi-dimensional (MD)GC-C-IRMS. Instmmentation and practical performance have already been outlined in 6.2.2.2.2. 

As already pointed out in chapter 6.2.2.1, isotope abundances, especially of primary products, are primarily fixed by those of their original elemental source. Within a closed system , e.g. a plant, all secondary compounds must be isotopically correlated to the primary assimilation products (carbohydrates), and their isotope abundances or patterns can be characterised by moderate shifts from here in the course of their biosynthesis by isotope effects of the reactions involved. These will only become manifest in the case of metabolic branching and would, depending on material fluxes in different directions, lead to isotopically depleted compounds in one... 

Intermolecular isotopic correlations are thus indicative for the authenticity of natural flavour mixtures. The method for their assessment is GC-C/P-IRMS (combustion/ reductive pyrolysis). As an early example for intermolecular isotope correlations, the result of a GC-C-IRMS analysis of the essential oil from Coriandrum sativum is given in Fig. 6.19 [327]. Further examples are corresponding analyses of oils from Artemisia vulgaris [327], Coriandrum sativum [337] and various lemon oils (Table 6.8) ]325, 338, 339]. In any of these cases typical correlations are found between the compounds of the same origin, even when their average 8-values may differ between... 

Fig, 6,19 Scheme of isotopic correlations between monoterpenes from Coriandrum sativum L. All identified compounds are characterised by their relative amounts, as determined by GC, and by their S C-values, obtained by GC-C-IRMS. The probable common precursors and intermediates are displayed in square brackets, and the calculated turnover rates in a given direction in % at the arrows. Modified with kind permission from [327]... 

A first step towards the analysis of isotopic patterns is the isotopic analysis of molecule parts, which must also have, in case of natural origin, intramolecular isotope correlations in this case, pure compounds in sufficient amounts must be available. The performance of the molecule degradation depends on its stmcture, but in many cases a simple hydrolysis will be of practical value. Examples are compiled in Tables 6.9 and 6.10. They represent typical groups of compounds, as esters and glycosides, which can easily be hydrolysed, or a few other compounds which can be split in two parts by a suitable other method, and which can subsequently be converted into CO2. 

Without any doubt the most valuable development in mass spectrometry has been multi-compound/multi-isotope analysis. This implies the application of GC-C/P-IRMS to the on-line analysis, not only of carbon but also of other isotopes, preferably of hydrogen and oxygen, in the individual components of a mixture, and the use of the metabolic and isotopic correlations obtained from such an analysis. In the course of this chapter, the potential of (positional) oxygen isotope analysis has been emphasised several times and this will still be a challenge of the future. The advantage of GC-C/ P-IRMS is its speed in performance and the very moderate demand on sample size and purity, and also its implication for automation. The information available can easily be correlated to that of other (classic) analyses. However, a disadvantage will be always that the data concern a global mean value for the whole molecule in question. 

H.-L. Schmidt, M. Butzenlechner, A. RoBmann, S. Schwarz, H. Kexel, K. Kempe (1993) Inter-and intramolecular isotope correlations in organic compounds as a criterion for authenticity identification and origin assignment. Z. Lebensm. Unters. Forsch. 196. 105-110... 

M. Butzenlechner, S. Thimet, K. Kempe, H. Kexel, H.-L. Schmidt (1996) Inter- and intramolecular isotopic correlations in some cyanogenic glycosides and glucosinolates and their practical importance. Phytochem. 42, 585-592... 

H.-L. Schmidt, D. Weber, A. Rossmann, R.A. Werner (1999) The potential of intermolecular and intramolecular isotopic correlations for authenticity control, in R. Teranishi, E.L.Wick, 1. Horn-stein (edts). Flavor Chemistry, Thirty Years of Progress, Kluver Academic/Plenum Press, New York 1999, pp. 55-61... 

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