title: Large veins of organic matter in meteorites.

authors: Zan Peeters, Bernd Liebig, Typhoon Lee

abstract: Organic matter (OM) in meteorites has traditionally been studied in extracted form. In those experiments, the insoluble organic matter (IOM) was obtained by dissolving away the surrounding material in strong acids. Spectroscopic and microscopic measurements of the extracted IOM has yielded a wealth of information on elemental composition, chemical structure, isotopic enrichment, and degree of alteration of the IOM, albeit only in bulk average. By extracting the IOM, all spatial information and any sign of heterogeneity within the meteorite is lost. In our experiments, we focus on measuring the composition of meteoritic OM in situ, without destroying the surrounding matrix. We have used the new nanoSIMS (nanometer-scale secondary-ion mass spectrometer), installed last year at Academia Sinica in Taipei, to map the carbon and nitrogen content of the Murchison meteorite. We found that OM, besides as a sub-micrometer fine-grained material dispersed within the matrix, can also occur as larger (up to 10 ?Em) inclusions and veins of pure organic matter. We then use a range of analytical tools to investigate the morphology, elemental, chemical, and isotopic compositions of the different inclusions. The results show that there is a lot of heterogeneity amongst the various inclusions within one meteorite, and sometimes even within one inclusion.