AGU Virtual Poster Session Fall 2017 - Tsvetomila Mateeva

Geochemical Analysis of organic matter in IODP core samples from Iberia – Newfoundland margin
Serpentinization and concomitant reduction of CO2 to methane at modern hydrothermal vents could support methanotrophic biosystems. However, serpentinization is pervasive across ocean floors, so it is possible that methanotrophy is not restricted only to hydrothermal vent systems.

The ocean-continent transition (OCT) of magma-poor rifted continental margins provides an opportunity to investigate this. Serpentinite, intrusive magmatic rocks and the overlying sediments (mainly breccia) collected as part of the International Ocean Discovery Program (IODP) from the Iberia-Newfoundland margin, were analysed to find evidence of methanotrophic bacteria related to the serpentinization process. Samples from Newfoundland contain n-alkanes, PAHs and isoprenoids (pristane, phytane) while those from Iberia also contained detectable steranes and hopanes. However, these compounds appear not to be indigenous to the rock. The only clear evidence of Archaean bacteria was provided from GDGTs and crenarchaeol from a sediment sample (897C) at the Iberian Margin and these were likely derived from overlying oceanic waters. There were no detectable GDGTs in any of the igneous and metamorphic rocks and hydrocarbon fingerprinting using polar plots suggests that any organic compounds in these samples were probably introduced from the drilling mud.

So far we have not found evidence of extensive methanotrophy, therefore we suggest that it is not a pervasive nor major biosystem at the Newfoundland or Iberian OCTs.