T65 Common Approaches to Investigating Patterns and Processes of Bioerosion across Substrates

Sunday, 31 October 2010
1:30 PM - 5:30 PM
Room 302

GEOCHEMICAL CHARACTERIZATION OF BIOSIGNATURES IN SUBSEAFLOOR VOLCANIC GLASSES USING SYNCHROTRON-BASED TECHNIQUES

Paper number: T65-9
Program: Technical Sessions
Time: 3:35 PM – 3:50 PM

Authors

Abstract

In the past few decades the oceanic subsurface has come to the attention of scientists as an intriguing unexplored biosphere. Through international collaborations such as the Integrated Ocean Drilling Program (IODP), we have seen clues that subseafloor basalts may currently host a huge quantity of active microbial cells and contain biosignatures of ancient life in the form of physical and chemical basalt glass alteration. The possibility that these subseafloor granular and tubular alteration features are indeed biosignatures has exciting implications for increasing our understanding of global geochemical cycling and the evolution of life on Earth, as well as for exploring other planets for signs of life. However, despite numerous efforts to strengthen the arguments for the biogenicity of these features, for the most part the evidence for biological activity is still lacking. The ability to clearly differentiate the geochemical changes that take place during both biotic and abiotic alteration processes in basalt glass, and an understanding of how these features change over time would help tremendously in settling the debate.

Using a number of synchrotron-based X-ray microprobe and microspectroscopy techniques we have been able to geochemically characterize both abiotic features and those of potential biotic origin at the sub-micron scale. We have mapped both major and trace element distributions in numerous tubular and granular alteration features, which shows intriguing patterns of mineral dissolution and authigenic precipitation. In addition, we have collected micro-diffraction patterns and analyzed the oxidation and coordination states of major and trace elements in potential biominerals, which may have formed as a result of microbial metabolic processes. By comparing the geochemical environment and the mineral dissolution and precipitation patterns between regions of putative biotic alteration, specifically tubular and granular features, with regions of abiotic alteration, or palagonization, we are working to characterize geochemical fingerprints of biological alteration that can be classified as biosignatures.