Chemolithotrophic life in ultramafic rocks: carbon substrates and pathways enabled by water-rock reactions using field and experimental hydrothermal investigations

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Methane and other hydrocarbons have been detected in Earth's oldest rocks, meteorites, and the atmospheres of other planets. On Earth, these hydrocarbons are often thought to be products of biological activities, and thus can indicate the presence of life today or billions of years ago. Therefore the investigation of hydrocarbons has implications for the study of the origin and evolution of life on early Earth, and the search for life in extreme environments and on other planets. Hydrocarbons, however, can also be produced by non-biological (abiogenic) reactions, yet the conditions under which these hydrocarbons are synthesized are not well understood. To differentiate between the biogenic and abiogenic hydrocarbons, the geologic conditions for creating abiogenic hydrocarbons and reaction inhibitors must be determined. Subsequently, unique geochemical indicators must be identified for abiogenic hydrocarbons. In natural settings, there is added difficulty identifying abiogenic hydrocarbons. Reactions between groundwater and the rock it flows through, such as serpentinization (the hydration of ultramafic rock), produce conditions amendable for abiogenic hydrocarbon production as well as chemolithotrophic life. Biological reactions can modify or overprint abiogenic signatures. Therefore, studying carbon cycling in locations favourable for abiogenic hydrocarbon production and chemolithotrophic life must be examined to determine these modifications, to identify life that can survive in extreme pH conditions that are created during serpentinization, and to determine the dependence of life in these systems on products of serpentinization. The research into early life and water-rock reactions in ultramafic rocks will benefit Canadians through the advancement of knowledge of life's evolution on Earth and the production of abiogenic hydrocarbons.