High resolution mass spectrometric investigations of the organic constituents of the Murray and Holbrook chondrites

Abstract

Two methods intended for the rapid preliminary analysis of organic geochemical samples are described. In illustration of the first, samples from a cross sectional core of a fragment of the Murray C2 chondrite were heated in the ion source of a high resolution mass spectrometer and the mass spectra of the vaporising organic material were recorded. The spectra obtained indicate that the organic material held in the cored sample was uniformly distributed and that it is a complex mixture of hydrocarbons ranging from alkanes to aromatic systems more highly condensed than phenanthrene or anthracene. Oxygen, nitrogen, sulfur and chlorine containing compounds are all found, the last being by far the least abundant. The second method takes advantage of the capabilities of the gas chromatograph-high resolution mass spectrometer combination. Studies of another Murray sample lead to the specific indication of a large number of compounds and give a good indication of the normal alkane distribution, in which pentadecane is found to be the most abundant compound. Mass spectra obtained from cross-sectional core samples taken from the Holbrook L6 chondrite indicate that this stone is also homogeneous and that its organic contents, present at a level of about 50 ppm, must be largely polymeric, the most abundant compounds being evolved at 300–500°. The pyrolysis products are predominantly alkylbenzenes, but various aromatic C H O, C H N, and C H S compounds are also observed along with a few more highly condensed aromatic hydrocarbons.