Unravelling abiogenic and biogenic sources of methane in the Earth's deep subsurface

At four underground sites in Precambrian Shield rocks in Canada and South Africa, hydrocarbon and hydrogen gases exsolving from saline fracture waters are analyzed for compositional and isotopic signatures. Dominated by reduced gases such as CH4, H2 and higher hydrocarbons (ethane, propane, butane), the most 13C-enriched methane end-members at all four sites show a pattern of carbon and hydrogen isotopic values similar to abiogenic gases …