Frontiers in Earth Science (Jun 2019)

Organic Matter Preservation and Incipient Mineralization of Microtubules in 120 Ma Basaltic Glass

  • Matthew R. M. Izawa,
  • Matthew R. M. Izawa,
  • James J. Dynes,
  • Neil R. Banerjee,
  • Roberta L. Flemming,
  • Lachlan C. W. MacLean,
  • Callum J. Hetherington,
  • Sergei Matveev,
  • Gordon Southam

DOI
https://doi.org/10.3389/feart.2019.00149
Journal volume & issue
Vol. 7

Abstract

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Hollow tubular structures in subaqueously-emplaced basaltic glass may represent trace fossils caused by microbially-mediated glass dissolution. Mineralized structures of similar morphology and spatial distribution in ancient, metamorphosed basaltic rocks have widely been interpreted as ichnofossils, possibly dating to ∼3.5 Ga or greater. Doubts have been raised, however, regarding the biogenicity of the original hollow tubules and granules in basaltic glass. In particular, although elevated levels of biologically-important elements such as C, S, N, and P as well as organic compounds have been detected in association with these structures, a direct detection of unambiguously biogenic organic molecules has not been accomplished. In this study, we describe the direct detection of proteins associated with tubular textures in basaltic glass using synchrotron X-ray spectromicroscopy. Protein-rich organic matter is shown to be associated with the margins of hollow and partly-mineralized tubules. Furthermore, a variety of tubule-infilling secondary minerals, including Ti-rich oxide phases, were observed filling and preserving the microtextures, demonstrating a mechanism whereby cellular materials may be preserved through geologic time.

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