Investigating Abiotic Organic Synthesis in Archean Rocks from the Canadian Shield

Observing abiotic organic synthesis in contexts representative of the early Earth is essential for understanding how inorganic matter can transform into organic matter of potential prebiotic interest. Subsurface environments can generate abiotic organic compounds through water-rock reactions; they are, however, difficult to detect on Earth due to the ubiquity of life in the first few kilometers of the crust.

Located in the Canadian Precambrian craton, within a 2.7 Gy old paleohydrothermal system, the Kidd Creek subsurface observatory is a unique accessible window into upper lithosphere abiotic organic chemistry, where biological activity is low, and both serpentinization and water radiolysis have occurred and still occur. At 2.4 km depth, exceptionally high concentrations of abiotic formate and acetate are detected in the groundwaters, revealing a likely radiolytic pathway. Indeed, radiolysis near solid carbonates can lead to the formation of short chain carboxylates, from interactions between oxidizing radiolytic products of water and dissolved carbonate ions. However, key questions remain on how radiolysis may alter mineral matrices, in particular carbonates, and to what extent minerals contribute to the synthesis, preservation, and evolution of abiotic organic compounds.

Using material characterization techniques, cutting-edge mass spectrometry and numerical simulations, this research aims to assess the presence of abiotic organic compounds in the Archean crustal rocks of Kidd Creek, as well as to reveal their formation pathways and possible evolutions with respect to their interactions with minerals, in the general context of the origins of life.