Selenium chondrites

The bulk chemical composition of the dust, obtained by averaging the compositions of particles in numerous tracks (Fig. 12.11a) and impact crater residues (Fig. 12.11b), is chondritic for iron, silicon, titanium, chromium, manganese, nickel, germanium, and selenium, within the 2o confidence level (Flynn el al., 2006). Copper, zinc, and gallium are... 

Many of the micron-sized interplanetary dust particles (IDPs) have approximately chondritic bulk composition (see Chapter 1.26 for details). Porous IDPs match the Cl composition better than nonporous (smooth) IDPs. On an average, IDPs show some enhancement of moderately volatile and volatile elements (see Palme, 2000). Arndt et al. (1996) found similar enrichments in their suite of 44 chondritic particles (average size 17.2 1.2 p.m). The elements chlorine, copper, zinc, gallium, selenium, and rubidium were enriched by factors of 2.2-2.7. In addition, these... 

Dreibus G., Palme H., Spettel B., Zipfel J., and Wanke H. (1995) Sulfur and selenium in chondritic meteorites. 

The bulk compositions of chondrites closely match the compositions of the solar photosphere, with the exception of a few highly volatile elements (hydrogen, carbon, nitrogen, helium) and lithium (see Chapter 1.03). The chondrite groups also show different levels of depletions in moderately volatile elements (e.g., manganese, sodium, potassium, gallium, antimony, selenium. 

The concentrations of four typical moderately volatile elements—manganese, sodium, selenium, and zinc—in the various classes of chondritic meteorites are shown in Figure 12, where elements are normalized to magnesium and CI-chondrites. Again there is excellent agreement between solar abundances and Cl-meteorites. A characteristic feature of the chemistry of carbonaceous chondrites is the simultaneous depletion of sodium and manganese in all types of carbonaceous chondrites, except Cl. Ordinary and enstatite chondrites are not or only slightly... 

The small amount of the late veneer (<1% chondritic material) would not have had a measurable effect on the abundances of other elements besides HSEs, except for some chalco-phile elements, most importantly sulfur, selenium and tellurium (Figure 15(c)). The amount of sulfur presently in the Earth s mantle (200 ppm. Table 4) corresponds to only 0.37% of a nominal CI-component, while the iridium content suggests a CTcomponent of 0.67%. O Neill (1991) has, therefore, suggested that the late veneer was compositionally similar to H-chondrites which contain only 2% S (Wasson and Kallemeyn, 1988). Because H-chondrites have higher iridium (780 ppb) than Cl-chondrites, the required... 

Fan TW-M, Teh SJ, Hinton DE, Higashi RM (2002) Selenium biotransformations into proteinaceous forms by foodweb organisms of selenium-laden drainage waters in California. Aquatic Toxicology 57 65-84 Flynn GJ, Sutton SR (1992) Trace Elements in Chondritic Stratospheric Particles Zinc Depletion as a Possible Indicator of Atmospheric Entry Heating. Proc. Of Lunar and Planetary Science 22, Lunar and Planetary Institute, Houston, 171-184... 

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