Representative elements abundance

Abstract. We present preliminary iron abundances and a element (Ca, Mg) abundance ratios for a sample of 22 Red Giant Branch (RGB) Stars in the Sagittarius galaxy (Sgr), selected near the RGB-Tip. The sample is representative of the Sgr dominant population. The mean iron abundance is [Fe/H]=-0.49. The a element abundance ratios are slightly subsolar, in agreement with the results recently presented by [2]. 

Iron meteorites offer the unique opportunity to examine metallic cores from deep within differentiated bodies. Most of these samples were exposed and dislodged when asteroids collided and fragmented. Although irons constitute only about 6% of meteorite falls, they are well represented in museum collections. Most iron meteorites show wide variations in siderophile-element abundances, which can be explained by processes like fractional crystallization in cores that mimic those in achondrites. However, some show perplexing chemical trends that may be inconsistent with their formation as asteroid cores. 

Since we know that A = eAN where A is the measured radioactivity, A is the decay constant, N is the number of radioactive nuclei present, and e is a constant representing the detection efficiency, we know that just a few radioactive nuclei need to be present to give measurable activities. Use of activation analysis can lead to measurement of elemental abundances of the order of 10-6-10-12 g. The actual detection... 

Generally accepted data for elemental abundances and isotopic compositions are given in Tables 1.2 and 1.3, respectively. The air concentrations in the rightmost column of Table 1.3 are often used as a normalization for observed concentrations in samples. If the atmosphere actually does account for nearly the total terrestrial inventory, then indeed these values are near the average concentration of noble gases in the materials that accreted to from the Earth. Use of these data for normalization does not constitute endorsement of this proposition, however, and whether or not they represent the terrestrial inventory, they are a convenient data set with elemental ratios of air and absolute abundances of the same order of magnitude as many samples. 

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.

The values derived from these correlations for the elemental abundance ratios should be representative for the whole Moon. On this basis it is not possible to distinguish between depletion of the more volatile elements (K, Rb, and Cs) or enrichment of the refractories. As we will see later, both processes have occurred. 

Based on the bulk chemistry, IDPs are divided into two groups (i) micrometer-sized chondritic particles and (ii) micrometer-sized nonchondritic particles. A particle is defined as chondritic when magnesium, aluminum, silicon, sulfur, calcium, titanium, chromium, manganese, iron, and nickel occur in relative proportions similar (within a factor of 2) to their solar element abundances, as represented by the Cl carbonaceous chondrite composition (Brownlee et al., 1976). Chondritic IDPs differ significantly in form and texture from the components of known carbonaceous chondrite groups and are highly enriched in carbon relative to the most carbon-rich Cl carbonaceous chondrites (Rietmeijer, 1992 Thomas et al., 1996 Rietmeijer, 1998, 2002). 

Laboratory analyses of SNCs provide a wealth of trace element and isotopic data that is otherwise unobtainable from remote sensing measurements. Compilations of element abundances in these meteorites by Treiman et al. (1987), Warren and Kallemeyn (1997), and Lodders (1998) have been augmented by analyses of newly discovered meteorites (Folco et al., 2000 Rubin et al., 2000 Barrat et al., 2001). Elemental abundances in a representative set of SNC meteorites are given... 

Figure 11 Trace element abundances of 250 MORE between 40° S and 55° S along the Mid-Atlantic Ridge. Each sample is represented by one Une. The data are normalized to primitive-mantle abundances of (McDonough and Sun, 1995) and shown in the order of mantle compatibility. This t)fpe of diagram is popularly known as spidergram. The data have been filtered to remove the most highly fractionated samples containing less than 5% MgO (source...

There are two major issues of concern with the approach of using C02/ He and N2/ Ar (or N2rHe) ratios in combination with and values to constrain the sources of volatiles at arcs. The first issue is the selection of representative end-member isotopic and relative elemental abundances—this factor has a profound effect on the deduced provenance of the volatile of interest. The second is the assumption that various elemental (and isotopic) ratios observed in the volcanic products are representative of the magma source. Both have the potential to compromise the accuracy of the output flux estimates. 

Ionov et al. (1993a, 1996) found carbonate in spinel Iherzolite xenoliths as interstitial crystals and as aggregates with calcium-rich olivine and aluminum- and titanium-rich clinopyroxene. They interpreted the former to be primary and the latter as evidence for metasomatism by a carbonate-rich melt. Subsequently, Ionov (1998) measured trace-element abundances in the carbonates and coexisting phases, and proposed the aggregate carbonates were formed by crystal fractionation from a carbonate melt. That these carbonates represent crystallized cumulates,... 

---