Mimořádná přednáška pořádaná Geologickou sekcí, ÚGMNZ a European Association of Geochemistry

Čas	03.11.2011 od 13:00 do 14:30
Přiložený soubor:	Benzerarai
Přidat událost do kalendáře	Google vKalendář (Windows, Linux) iCal (Mac OS X)

Geomicrobiology studies interactions between microorganisms and minerals. Working at the nanoscale on such systems is not just a methodological challenge and the use of new fancy tools. Here, I will show how we can combine Scanning Transmission X-ray Microscopy (STXM) and Transmission Electron Microscopy (TEM) to perform high spatial and energy resolution near-edge x-ray absorption fine structure (NEXAFS) and high resolution imaging on diverse samples of geomicrobiological interest. I will consider diverse samples including naturally and experimentally biomineralized bacteria, and bioweathered silicates. Spectroscopy was performed at the C K-edge, Al K-edge, Ca L2,3-edge, Fe L3-edge, and N K-edge offering the possibility to characterize diverse biochemical compounds, unique bacterial spectroscopic signatures, and iron oxidation state at microorganism-mineral interfaces. Combination of TEM and STXM provides remarkably clear chemical state-specific images of fossilized microorganisms and microorganism-mineral interfaces at the nanometer scale. This allows finding yet unreported chemical and mineralogical heterogeneities at the submicrometer-scale in ancient and recent rocks, and also reveals in experimental samples a more complex picture of a given process than that observed at a rougher scale. By reviewing studies performed on Archean stromatolites, modern Fe-oxidizing bacteria, fossils preserved in metamorphic rocks or pathological calcifications, I will show how the methodology presented here should be helpful in assessing the importance of microorganisms in the evolution of Earth’s surface chemistry and in identifying them in early Earth and planetary materials.

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