Element in meteorite

Clayton RN, Hinton RW, Davis AM (1988) Isotopic variations in the rock-forming elements in meteorites. Phil Trans R Soc Lond A 325 483-501... 

Solution databases now exist for a niunber of the major metallic alloy systems such as steels, Ni- based superalloys and other alloy systems, and highly accurate calculation have been made which even a few years ago would have been considered impossible. The number of substance databases are increasing and the numbers of substances they include is reaching well into the thousands. Substance and solution databases are increasingly being combined to predict complex reactions such as in gas evolution in cast-irons and for oxidation reactions, and it is already possible to consider calculations of extreme complexity such as the reactions which may occur in the burning of coal in a industrial power generator or the distribution of elements in meteorites. 

The term cosmochemistry apparently derives from the work of Victor Goldschmidt (Fig. 1.6), who is often described as the father of geochemistry. This is yet another crossover and, in truth, Goldschmidt also established cosmochemistry as a discipline. In 1937 he published a cosmic abundance table based on the proportions of elements in meteorites. He used the term cosmic because, like his contemporaries, he believed that meteorites were interstellar matter. Chemist William Harkins (1873-1951) had formulated an earlier (1917) table of elemental abundances - arguably the first cosmochemistry paper, although he did not use that term. As explained in Chapter 3, the term solar system abundance is now preferred over cosmic abundance, although the terms are often used interchangeably. 

Clayton, R. N., Hinton, R. W. and Davis, A. M. (1988) Isotopic variations in the rockforming elements in meteorites. Philosophical Transactions of the Royal Society of London, A325, 483-501. 

Their abundances are in most cases below solar, i.e., they have lower element/silicon ratios than the Sun or Cl chondrites, they are depleted (see below). In Figure 2, abundances of moderately volatile elements in CVS meteorites relative to those in Cl meteorites are plotted. Increasing depletions correlate with decreasing condensation temperatures but are independent of the geochemical properties of the elements. Depletions of moderately volatile elements in meteorites are produced by incomplete condensation. The amount and the relative abundances of these elements in meteorites are probably the result of removal of volatiles during condensation (Palme et al., 1988). 

In Figure 3, aluminum is representative of refractory elements in general and the Al/Si ratios indicate the size of the refractory component relative to the major fraction of the meteorite. It is clear from this figure that the Al/Si ratio of Cl meteorites agrees best with the solar ratio, although the ratios in CM (Type 2 carbonaceous chondrites) and even OC (ordinary chondrites) are almost within the error bar of the solar ratio. The errors of the meteorite ratios are below 10%, in many cases below 5%. A very similar pattern as for aluminum would be obtained for other refractory elements (calcium, titanium, scandium, REEs, etc.), as ratios among refractory elements in meteorites are constant in all classes of chondritic meteorites, at least within —5-10%. The average Sun/CI meteorite ratio of 19 refractory lithophile elements (Al, Ca, Ti, V, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Lu, see Table 2) is... 

Palme H., Larimer J. W., and Lipschutz M. E. (1988) Moderately volatile elements. In Meteorites and the Early Solar System (eds. J. F. Kerridge and M. S. Matthews). University of Arizona Press, Tucson, pp. 436-461. 

Reed, G. W., Kigoshi, K., Turkevich, A. Determinations of concentrations of heavy elements in meteorites by activation analysis. Geochim. Cosmochim. Acta 20, 122—140 (1960). 

Anders, E., Larimer, J.W. Extinct superheavy element in meteorites attempted characterization. Science 175, 981-983 (1972)... 

The one-time presence of superheavy elements in meteorites has been inferred from the anomalous xenon effect. The ratios of xenon isotopes measured in some meteorites are very different from those found in terrestrial xenon. This was thought to be due to the former presence of Pu which had produced fission-product xenon as it decayed out. This theory was confirmed in part recently when xenon isotope ratios from Pu were measured and were found to be identical with ratios from one group of meteorites, the achondrites. On the other hand, the chondrite meteorites still do not fit. It had been shown that an element heavier than Cf was needed to give the required ratio, ° and Anders and Heymann and Dakowski suggested independently that extinct superheavy elements could be the cause. Rao indicated that excess Kr could be explained similarly. Schramm has calculated that if fission of a superheavy element is the cause, its half-life would lie in the surprisingly narrow range of 1.6 x lO" —6.8 x 10 yr. 

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