Effects of minerals on metamorphism of organic matter during thermal processes in meteorite parent bodies

Molecular structures and chemical compositions of organic matter in primitive meteorites reflect the conditions of the parent bodies, as well as the preaccretional history. During the parent body processing, co-existing minerals could have effects on structural changes of organics, in addition to temperature and redox state. Here, we performed heating experiments of a primordial organic matter analog with and without minerals to understand the effects of minerals on organic matter in conditions simulating metamorphism in thermally metamorphosed type 3 chondrites. The primordial analog materials were heated up to 400 degrees C, and the experimental products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS). Montmorillonite and olivine, particularly montmorillonite, enhanced decomposition of oxygen containing species due to decarboxylation and/or cracking, while olivine enhanced esterification at lower temperature. Our results further imply that the variations of insoluble organic matter in CV, CO, and type 3 ordinary chondrites could be partially due to different mineral compositions. We also tested the effects of pressure on the degradation of the organic matter at 400 degrees C up to 268 atm, however no significant pressure effects were observed by FTIR and GC/MS.

Automated summary

The molecular structures and compositions of organic matter in primitive meteorites are influenced by the parent bodies and preaccretional history. Experimental heating of primordial organic matter analog with and without minerals shows that minerals can affect the decomposition and chemical reactions of organics, providing insights into the variations of organic matter in different types of chondrites.