EXAMINATION OF ORGANIC-COMPOUNDS FROM INSOLUBLE ORGANIC-MATTER ISOLATED FROM SOME ANTARCTIC CARBONACEOUS CHONDRITES BY HEATING EXPERIMENTS

Insoluble organic matter isolated from five Antarctic CM2 chondrites was heated in a thermal analyzer from room temperature to 800-degrees-C under helium atmosphere. Organic compounds from the thermal decomposition of the Yamato-791198 sample were studied by a gas chromatograph-mass spectrometer (GC-MS). The number of compounds identified was over 120, belonging mainly to the two following groups: (1) benzene and naphthalene, and their alkyl derivatives; and (2) sulfur-containing heterocycles and their alkyl derivatives. Small amounts of aliphatic hydrocarbons and nitriles were also detected. Relative amounts of compounds released from the five chondrite samples were monitored by the MS with increasing temperature. Yamato-74662 and Yamato-791198 showed organic compounds mainly over the temperature range of 300-600-degrees-C, while the other three (Yamato-793321, Yamato-86720, and Belgica-7904) did not show any, except small amounts of benzene. These results indicate that the insoluble organics in Yamato-74662 and Yamato-791198 possess a thermally labile organic fraction; whereas those in Yamato-79332 1, Yamato-86720, and Belgica-7904 do not and are graphitic. The difference between the insoluble organic fractions may be related to aqueous alteration and thermal metamorphism on the parent bodies.