Microbial mediation of textures and minerals – terrestrial or parent body processes?

Evolution of chondritic parent body is influenced by thermal, impact metamorphism and aqueous alteration, studied in Mező-Madaras, Knyahinya, Mócs and Nyírábrány in aspect of high resolution in situ textural, mineralogical and organic geochemical characteristics, using optical microscopy, FTIR-ATR and Raman spectroscopy. Our observations focused on Fe-containing opaque grains, glass, olivines and pyroxenes, which were well populated by micrometer-sized microbial filamentous elements in their boundary region within matrix and inside the minerals resembling mineralized microbially produced textures (MMPT), affecting 70-80 vol% of samples. In MMPT iron oxides (ferrihydrite, goethite), olivine, montmorillonite, kandite minerals and various hydrocarbon compounds were identified. (1) Data confirmed dense and invasive terrestrial microbially mediated contamination in the chondrites, supported by microtexture, micromineralogy and embedded organic compounds. As the classical transformation processes are supposed nowadays to have been happened on the parent bodies, a contradiction arose: how could it be that these classical products are manifested in microbially mediated texture? (2) Based on terrestrial analogies, microbial mediation is a sudden process comparing to geological times, very ancient, widespread and occur in various environments under determined conditions. It can consume previous and also produce new minerals. After formation, MMPT can survive billions of years proposing occurrence on parent bodies.