ABIOTIC METHANE ON EARTH

Over the last 30 years, geochemical research has demonstrated that abiotic methane (CH 4 ), formed by chemical reactions which do not directly involve organic matter, occurs on Earth in several specific geologic environments. It can be produced by either high‐temperature magmatic processes in volcanic and geothermal areas, or via low‐temperature (<100°C) gas‐water‐rock reactions in continental settings, even at shallow depths. The isotopic composition of C and H is a first step in distinguishing abiotic from biotic (including either microbial or thermogenic) CH 4 . Herein we demonstrate that integrated geochemical diagnostic techniques, based on molecular composition of associated gases, noble gas isotopes,…