FT-IR spectroscopic studies of major organic matter in carbonaceous chondrites using microscopic technique and comparison with terrestrial kerogen

Infrared (IR) absorption spectra of major types of carbonaceous matter in four Antarctic carbonaceous chondrites (Y-74662,Y-791198,ALH-77307,Y-791717) and two non-Antarctic carbonaceous chondrites (Murchison, Allende) were taken using a microscopic FT-IR technique. Without any treatment for concentration of carbon, powdered samples of carbon-rich C2 chondrites such as Y-74662,Y-791198,and Murchison gave spectra of the carbonaceous matter with enough intensity by focusing the beam on carbonaceous aggregates. Carbon-poor C3 chondrites (ALH-77307,Y-791717,and Allende) necessitated carbon enrichment by acid treatment to give IR spectra of carbonaceous matter of adequate intensity. The IR spectra indicated the presence of similar functional groups in the major types of carbonaceous matter of all of the investigated chondrites. Some natural coals (typical terrestrial kerogen) show very similar IR spectra to the carbonaceous matter of carbonaceous chondrites

Spectroscopic studies of acid-resistant residues of carbonaceous chondrites

Mass and IR spectra have been obtained of the acid-resistant residues resulting from HCl and HF treatments of ALH-77307 (C3). ^C NMR spectra of the residues obtained by partial mineral dissolution with acid treatments of Yamato-791717 (C3) and Allende (C3) have been recorded under CP-MAS conditions. These spectral data were compatible with the polycyclic aromatic structure proposed for the major carbonaceous matter in carbonaceous chondrites by the authors

Pyrolytic nature of carbonaceous matter in carbonaceous chondrites and secondary metamorphsm

Major carbonaceous matter in five C2 carbonaceous chondrites (Y-791198,Y-74662,Murchison, B-7904,and Y-793321) and six C3 carbonaceous chondrites (Allende, Y-790992,Y-791717,Y-81020,ALH-77003,and ALH-77307) was investigated by pyrolysis-gas chromatography. The amount of naphthalene produced on the pyrolysis varied largely from chondrite to chondrite, and the carbonaceous matter in these chondrites could be divided into five groups by the efficiency of formation of pyrolysis products. The groups did not accord with any conventional subdivisions of carbonaceous chondrites. The grouping based on the pyrolytic nature of the major carbonaceous matter may give additional information about secondary metamorphism in carbonaceous chondrites

Pyrolytic studies of carbonaceous matter in Antarctic carbonaceous chondrites

Pyrolysis products of the major carbonaceous matter in six Antarctic carbonaceous chondrites, Y-74662 (C2), Y-791198 (C2), Y-793321 (C2), B-7904 (C2), Y-791717 (C3), and ALH-77307 (C3), have been examined by GC-FID and GC-MS. There is apparently a similarity in the structure of all samples. Many sulfur-containing compounds have been detected as major products in pyrolysis of the residues which were obtained by partial mineral dissolution of Y-791717 and ALH-77307 with concentrated hydrochloric acid

Pyrolytic studies of organic components in Antarctic carbonaceous chondrites Y-74662 and ALH-77307

The organic components of two Antarctic carbonaceous chondrites, Y-74662 (C2) and ALH-77307 (C3), have been investigated by pyrolysis using a Curie point pyrolyzer equipped with GC or GC-MS. Although a number of aromatic compounds have been detected as the pyrolysis products of Y-74662 along with a small amount of n-alkanes, only a few aromatic compounds in small quantities and no n-alkane have been detected in the components produced on the pyrolysis of ALH-77307