Publikationsdatum:
2023-02-21
Beschreibung:
Continental ultramafic rock systems, through the process of serpentinization, provide chemical and biochemical
pathways that lead to the production of methane. The extent to which rock-water-gas reactions and organisms
supply methane in these systems is a matter of considerable discussion and debate. Deciphering the interplay of
abiotic and microbial methane observed at the surface requires several lines of reasoning as well as a variety of
analyses. Despite using multiple models and interpretative tools, conclusions for the origin of methane at a
particular site may vary or diverge from regional or global observations. Here, we critically address how possible
conclusions of microbial versus abiotic methane in continental serpentinization systems may be interpreted and
reinterpreted. We review fundamental concepts, advantages and limits, for three major methane origin models:
(a) abiotic CO2 hydrogenation supplying gas reservoirs, (b) derivation from fluid inclusions in olivine-rich rocks,
and (c) microbialgenesis in aquifers. We use the case of methane in the Samail ophiolite of Oman as an
emblematic example of multiple interpretations; we identify ambiguous information offered by methane clumped
isotopes and molecular gas compositions (e.g., the meaning of gaseous hydrocarbons heavier than methane),
and suggest key tools, such as radiocarbon (14C) in methane, which may solve interpretative issues. The major
constraint in any model of methane origin is the capability to sustain continuous gas flows, in terms of methane
emission intensity, longevity and spatial extension, such as in natural gas sedimentary systems. Overall, this
review suggests that any site interpretation can benefit from a holistic approach, integrating geochemical,
geological and biological data with gas flow dynamics, as well as including regional and global contextualization.
Beschreibung:
Published
Beschreibung:
105373
Beschreibung:
6A. Geochimica per l'ambiente e geologia medica
Beschreibung:
JCR Journal
Repository-Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Materialart:
article
