Carbon, Hydrogen, and Nitrogen Isotopic Composition of the Renazzo and Orgueil Organic Components

Abstract

The concentration and isotopic composition were determined for carbon, nitrogen, and hydrogen extracted from bulk samples and acid (HF-HCl) residues of Orgueil and Renazzo meteorites. The samples were heated step-wise and the measured quantities of gasses given off at each step were analyzed mass spectrometically. The whole rock δD and δ^(15)N values are +930‰ and + 190‰ for Renazzo and + 170‰ and + 40‰ for Orgueil respectively. Hydrogen concentrations from the acid residues, shows a bimodal release pattern at temperatures between 400 and 1300 ºC and the average δD of hydrogen from the acid residues from Renazzo is + 2500‰ and from Orgueil is + 1100‰. The δD of the hydrogen released at the high temperature release mode is on the average of + 1500‰ for Orgueil and + 3100‰ for Renazzo. The low temperature-release-hydrogen has a δD value of+ 1000‰ for Orgueil and +2000‰ for Renazzo. These results imply that the hydrogen isotopic composition is not homogeneously distributed among the various compounds of the acid residues. The δ^(13)C of the carbon in the acid residues measured -20‰ for Renazzo and -5‰ for Orgueil. With our previous results on δD's acid residues of Murray and Murchison ( +600‰ and +800‰ respectively) we are able to calculate by mass balance an approximate isotopic composition of phyllosilicates in these four meteorites. The δD's of inorganic hydrogen are calculated to be~ -250‰ for Murray, Murchison, and Orgueil.