ELEMENTAL ABUNDANCE PATTERNS

Variations occur within the individual elemental abundance patterns as observed in different samples (see discussion in text). Values listed here  

Where no specific errors are given in the original literature, a 10% error in elemental abundances was assumed and propagated. 

All patterns are fractionated, relative to the solar abundance pattern (cf Figs. 1 and 

Given the evidence for variations in elemental composition within various components, isotopic compositions generally are more characteristic for the presence of a 

Strictly speaking, only very low upper limits on the abundance of Ne and Ne in the R and G components are known (Table 3). But it is generally accepted that Ne-R [=Ne-E(L)] is pure Ne, the decay product of Na (Ty = 2.6 a), which in turn was trapped when the grains condensed. This apparently radiogenic origin led Amari et al. 

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Abstract. The Milky Way harbours two disks that appear distinct concerning scale-heights, kinematics, and elemental abundance patterns. Recent years have seen a surge of studies of the elemental abundance trends in the disks using high resolution spectroscopy. Here I will review and discuss the currently available data. Special focus will also be put on how we define stars to be members of either disk, and how current models of galaxy formation favour that thick disks are formed from several accreted bodies. The ability for the stellar abundance trends to test such predictions are discussed. 

Nowadays it is widely accepted that the 13C(a, n)160 reaction is the main source or neutrons of the s-process in AGB stars. Comparison between the s-element abundance patterns found in AGB stars of different classes and metallicity with theoretical predictions show a nice agreement (see e.g. Busso et al. 2001 and references therein). This comparison would indicate also that, at a given stellar metallicity, a dispersion in the quantity of 13C burnt may exists as one would expect, on the other hand. In fact, s-element patterns for individual stars can be fitted assuming that the amount of 13C burnt ranges from 10 7 to almost 10-5 Mq. However, the large error bar in the abundances precludes to put more... 

Noble gas abundances in lunar soils and chondrites, (a) Elemental abundance patterns for trapped solar wind in lunar soils, normalized to solar system abundances, (b) Elemental abundance patterns for planetary trapped noble gases, normalized to solar system abundances. This diagram is intended to illustrate patterns only vertical positions are arbitrary. Modified from Ozima and Podosek (2002). 

The applications of activation analysis are almost innumerable. In the physical sciences, activation analysis is used in trace-element analysis of semiconductor materials, metals, meteorites, lunar samples, and terrestrial rocks. In most cases, the multielemental analysis feature of activation analysis is used to measure the concentrations of several trace-elements simultaneously. From these detailed studies of trace-element abundance patterns, one has been able to deduce information about the thermal and chemical history of the Earth, moon, Mars, and meteorites, as well as the source or age of an object. 

We summarize noble gas amounts in deep-sea and subaerial sediments in Figure 5.1. From the data displayed here, we calculated median values which are shown in Table 5.1. Both Figure 5.1 and Table 5.1 show that even though there is little difference in the lighter noble gas concentration between subaerial and deep-sea sediments (He, Ne, and Ar), heavier noble gases are much more abundant in subaerial sediments than in deep-sea sediments. As in volcanic rocks (cf. Section 6.6), most sediments, either deep-sea or subaerial, show fractionation toward the heavier ones relative to air noble gas, although the mechanism for the fractionation may be different. Figure 5.2 shows noble a gas elemental abundance pattern relative to the air abundance subaerial sediments show much more severe fractionation. 

Figure 6.4 Elemental abundance patterns for noble gases in mantle-derived samples (cf. Figure 6.3 and Table 6.1). The ordinate is (G/36Ar)s/(G/36Ar)a, where subscripts s and a designate sample and atmosphere, respectively, and G represents any noble gas isotope.

Rehkamper, M., Halliday, A. N., Barfod, D., Fitton, J.G., and Dawson, J.B. (1997a) Platinum group element abundance patterns in different mantle environments. Science 278, 1595-1598. 

Figure 8 The heavy-element abundance patterns for the three stars CS 22892-052, HD 155444, and BD+17°3248 are compared with the scaled solar system r-process abundance distribution (solid line) (Sneden et aL, 2003 Westin et aL, 2000 Cowan et al., 2002). Upper limits are indicated by inverted triangles (source Truran et aL, 2003).

Elemental abundance patterns for ordinary, Rumuruti-like (R), and Kakangari-like (K) chondrites are fairly flat and enriched relative to Cl for lithophile and refractory lithophile elements. Enstatite chondrites have the lowest abundance of refractory lithophile elements. 

The bulk trace element abundance patterns in CAIs are generally agreed to reflect element volatility, with the most refractory elements enriched relative to solar (Cl chondrite) abundances, and volatile elements depleted. 

Siderophile element abundance patterns are variable, but brachinites are depleted in them— Ir/Mg ratios are 0.12-0.15 X Cl for ALH 84025, Brachina, and Eagles Nest, and 0.038 X Cl for EET 99402-EET 99407. All are enriched in cobalt relative to other siderophile elements, with Co/Ni ratios of 1.6-2.1 X Cl for ALH 84025, Brachina and Eagles Nest, but 6.2 X Cl for EET 99402-EET 99407. The high Co/Ni and Co/Mg ratios are plausibly due to substantial lithophile character for cobalt compared to other siderophile elements in these relatively oxidized meteorites (Mittlefehldt et al., 2003 Figure 1). 

Some elemental abundance patterns for solar gases in lunar soils (and one gas-rich meteorite, Pesyanoe, that was likely exposed to solar wind on the surface of an asteroid see Marti, 1969) are illustrated in Figure 6 (left panel). Gases in true solar proportions would define a horizontal straight line in this diagram, and it is evident... 

In the classical picture, i.e., before appreciation that presolar components were an important part of the total inventory of trapped gases in meteorites, neither the isotopic effects nor the generation of the elemental abundance pattern were ever explained satisfactorily in terms of quantitative models that gained consensus acceptance. Some aspects of this problem have become moot, however, since it is now recognized that planetary gas is composite planetary gas includes the contributions of the exotic noble-gas components (Table 2) imported into the solar system by presolar grains. These contributions, especially of the HE component, can be substantial (Huss and Lewis, 1995 also see Figure 7). 

Figure 6 Elemental abundance patterns for trapped noble gases in various planetary materials. For each gas identified on the abscissa, the ordinate shows the depletion factor in a given sample, i.e., the gas concentration in the sample divided by what the concentration would be if the gas were present in undepleted cosmic proportion (normalized for a nominal rock with 17% Si). The relative elemental abundances in the left panel illustrate the solar pattern, those in the right panel the planetary pattern. The vertical broken lines for each gas illustrate typical in situ gas concentrations (the radiogenic component for " He, spallation for the others), below which it becomes progressively more difficult to characterize or even identify trapped components (source Ozima and Podosek, 2002).

Trace-element abundance patterns, often called spidergrams, of MORE are shown in Figure 11 ( spidergram is a somewhat inappropriate but a convenient term coined by R. N. Thompson (Thompson et al., 1984), presumably because of a perceived resemblance of these patterns to spider webs, although the resemblance is tenuous at best). The data chosen for this plot are taken from le Roux et al. (2002) for MORE glasses from the MAR (40-55° S), which encompasses... 

Figure 18 Primitive mantle normalized trace-element abundance patterns for whole-rock MARID xenoliths from kimberlites. Primitive mantle values used for normalisation in this plot and subsequent plots are those of McDonough and Sun (1995) (sources Pearson and Nowell, 2002 Gregoire et al, 2002).

Mantle-derived materials have a range of elemental-abundance patterns due to various fractionation processes, although the mantle pattern has been inferred from measured isotopic variations and radiogenic isotope-production ratios (see PorceUi and Ballentine, 2002). From the " He/ Ne production ratio and the average coexisting shifts in " He/ He and Ne/ Ne in the mantle relative to the primordial compositions, a ratio of He/ Ne = 11 is obtained. This is greater than the more recent estimate of 1.9 for the solar nebula (see discussion in Porcelli and Pepin (2000)). Similarly, using the mantle " °Ar/2 Ar... 

Chondrites. Chondrites are stony meteorites and are the most abundant meteorite type (87% of all meteorites). Their radiometric ages are around 4.56 Ga and these ages are thought to define the time when the solar system formed. Chemically their element abundance patterns, apart from the very light and/or volatile elements, are the same as that of the sun and other stars, and for this reason they are thought to represent undifferentiated cosmic matter. Chondrites therefore are thought to represent the most primitive material in the solar system. They are the "stuff" from which all other rocky materials were built. 

Constraints on the origin of the Earth s volatiles from volatile element abundance patterns... 

Kramers (2003) calculated major and minor (noble gas) volatile element abundance patterns in the Outer Earth Reservoir (the atmosphere, hydrosphere, oceanic and continental crust, and recycled components in MORB-source mantle). These are presented, normalized to solar abundances, together with data for chondrites in Fig. 5.6. The following observations can be made ... 

Kramers, J.D., 2003. Volatile element abundance patterns and an early liquid water ocean on Earth. Precambrian Res., 126, 379-94. 

Fig. 18. Heavy-element abundance patterns for three heavy-element-rich metal-poor stars, the [Eu/Fe] ratios of which are included in Fig. 16. The solid lines represent a scaled SoS r-nuclide distribution. Inverted triangles indicate upper limits...

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