Molecular and isotopic indicators of alteration in CR chondrites

Abstract

Molecular and isotopic indicators of alteration in CR chondritesRenazzo, Al Rais, and Y-790112 release qualitatively similar pyrolysis products, although there are some variations. Al Rais' macromolecular structure contains substantially higher relative abundances of alkylated and oxidized species and relatively lighter δ 15 N, suggesting that it has endured more extensive aqueous processing than the other CR chondrites. Renazzo appears relatively unprocessed, with a low degree of alkylation, a lack of detectable nitrogen-bearing components, and low methylnaphthalene ratio. EET 87770's low abundance of alkylated species suggests its macromolecular structure may be relatively condensed, with condensation potentially assisted by a period of mild thermal alteration.

Effects of secondary alteration on the composition of free and IOM-derived monocarboxylic acids in carbonaceous chondrites

“…Murchison (CM2) has experienced more advanced aqueous alteration than EET 87770, but at similar temperatures (Clayton and Mayeda, 1984;Pearson et al, 2006). Type IIA chondrules in this meteorite contain glassy mesostasis that has undergone only partial alteration on the periphery of the chondrules, with the development of an alteration rim that is about 50 l in thickness where the glass is in contact with the fine-grained matrix.…”

Organic Geochemistry of Meteorites

“…The table data were compiled from the literature (Alexander et al, 1998;Anders, 1988;Grady et al, 1988;Kerridge, 1985;Pearson et al, 2006;Robert and Epstein, 1982;Russell et al, 1996;Smith and Kaplan, 1970;Smith and Rigby, 1981;Swart et al, 1982;Yang and Epstein, 1983;Virag et al, 1989).…”

“…Chlorinated benzoic acids were found within Orgueil (CI1), Cold Bokkeveld (CM2), Murray (CM2), and Murchison (CM2), and data suggested that they may be present both free and bound to the macromolecular material (Schö ler et al, 2005). Polychlorinated (C 1 -C 4 ) biphenyls were detected in the pyrolysis products of Al Rais (CR2) and Yamato-790112 (CR2) (Pearson et al, 2006). A persistent concern in organohalogen studies of meteorites is the influence of halogenated solvents.…”

Aqueous alteration in CR chondrites: Meteorite parent body processes as analogue for long-term corrosion processes relevant for nuclear waste disposal

“…For detailed overviews of mineralogy, petrology, and composition of CR chondrites see Weisberg et al (1993), Kallemeyn et al (1994), Krot et al (2002), Pearson et al (2006), Abreu (2007), Weisberg and Huber (2007) and Schrader et al (2008). For the purpose of this study, we used a subset of CR chondrites, namely the CR2 chondrites: Renazzo and Al Rais and the GRO 95577 CR1 (see samples description below).…”