In-Situ Heating Decrease Kinetics of Aliphatic Hydrocarbons in Tagish Lake Meteorite by Micro-Ftir

摘要

Carbonaceous chondrites are known to contain up to 3wt.% C, the major part of which corresponds to a macromolecular organic fraction. Chondritic organic matter is based on small aromatic units, cross-linked by short aliphatic chains rather than large clusters of polyaromatic structures. Two main characteristic features of those organics measured by FTIR are (1) an equivalent intensity of the asymmetric stretching mode absorptions for CH(sub 3) (2960cm(sup -1)) and CH(sub 2) (2920cm(sup -1)) and (2) a lack of aromatic CH-stretching mode (3040cm-1). Tagish Lake is a new type of water- and carbon-rich type 2 carbonaceous chondrite (4, 5). Its total carbon content is approx 5 wt%, of which the organic carbon content reaches approx 1.3 wt%. Tagish Lake may have never experienced temperatures higher than 120 deg C after formation of organics based on the disappearance of infrared (IR) organic peaks in step heating experiments. Here we report in-situ kinetic heating experiments of organics in Tagish Lake by micro-FTIR to characterize the nature of aliphatic hydrocarbons and their thermal stabilities.