141-1 Diagenetic Controls on the Preservation and Transformation of Microbial Biosignatures in Silica Sinters

Session: New Advances in Geobiology

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Abstract:

Silica sinters represent optimal archives for investigating the interplay between geological and biological processes in hydrothermal environments. They not only hold the geochemical records of hydrothermal activities but also preserve diverse biosignatures of microbial communities that once thrived in these systems. Some Archean and Jurassic sinters demonstrate exceptional textural and compositional biosignature retention, respectively. Modern silica sinters also host a wide variety of microbial features, including laminated mats, filaments, and preserved organic matter. However, structures such as palisade fabrics, once considered uniquely biogenic, have been shown to form through abiotic processes under strong evaporation conditions. Likewise, preserved organic matter within sinters may be formed by geological processes and introduced to the silica matrix later. These recent findings highlight the need to re-evaluate how biosignatures are identified in ancient sinters and silica-rich deposits on other planetary bodies. Therefore, it is essential to investigate the geobiological interactions in silica sinters in order to better understand how biosignatures are preserved within them. Previous experimental studies have explored the interactions between silica and organic matter in synthetic systems, which neglect a key factor: porosity. Porosity governs the movement of fluids, heat, and substances, all of which can critically influence the preservation or destruction of biosignatures during sinter diagenesis. Some experimental studies involving silica sinters were performed under high-temperature conditions similar to burial diagenesis. In this study, we conducted hydrothermal experiments on natural silica sinters at moderate temperatures to simulate early diagenetic processes. We characterized textural, mineralogical, and porosity evolution, as well as the distribution and alteration of organic matter, before and after the hydrothermal experiments. Our results illustrate the silica maturation in natural sinters during early diagenesis and reveal how these processes influence the preservation of various types of biosignatures. These findings provide essential context for interpreting ancient terrestrial sinters and assessing biosignature potential in planetary analogs such as Mars.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6660

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