TY - JOUR
T1 - Methane clumped isotopes
T2 - Progress and potential for a new isotopic tracer
AU - Douglas, Peter M.J.
AU - Stolper, Daniel A.
AU - Eiler, John M.
AU - Sessions, Alex L.
AU - Lawson, Michael
AU - Shuai, Yanhua
AU - Bishop, Andrew
AU - Podlaha, Olaf G.
AU - Ferreira, Alexandre A.
AU - Santos Neto, Eugenio V.
AU - Niemann, Martin
AU - Steen, Arne S.
AU - Huang, Ling
AU - Chimiak, Laura
AU - Valentine, David L.
AU - Fiebig, Jens
AU - Luhmann, Andrew J.
AU - Seyfried, William E.
AU - Etiope, Giuseppe
AU - Schoell, Martin
AU - Inskeep, William P.
AU - Moran, James J.
AU - Kitchen, Nami
N1 - Funding Information:
The development of the Ultra was funded by NSF-EAR. PMJD was supported in part by Royal Dutch Shell . Research on the Santa Barbara Basin was supported by NSF OCE-1046144 . The manuscript benefitted from constructive reviews from Andrew Murray, Kenneth Peters, and Xinyu Xia.
Publisher Copyright:
© 2017 Elsevier Ltd
PY - 2017/11
Y1 - 2017/11
N2 - The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding petroleum systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. In general, clumped isotope measurements indicate plausible formation temperatures for abiotic, thermogenic, and microbial methane in many geological environments, which is encouraging for the further development of this measurement as a geothermometer, and as a tracer for the source of natural gas reservoirs and emissions. We also highlight, however, instances where clumped isotope derived temperatures are higher than expected, and discuss possible factors that could distort equilibrium formation temperature signals. In microbial methane from freshwater ecosystems, in particular, clumped isotope values appear to be controlled by kinetic effects, and may ultimately be useful to study methanogen metabolism.
AB - The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding petroleum systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. In general, clumped isotope measurements indicate plausible formation temperatures for abiotic, thermogenic, and microbial methane in many geological environments, which is encouraging for the further development of this measurement as a geothermometer, and as a tracer for the source of natural gas reservoirs and emissions. We also highlight, however, instances where clumped isotope derived temperatures are higher than expected, and discuss possible factors that could distort equilibrium formation temperature signals. In microbial methane from freshwater ecosystems, in particular, clumped isotope values appear to be controlled by kinetic effects, and may ultimately be useful to study methanogen metabolism.
KW - Biogeochemistry
KW - Clumped isotopes
KW - Geothermometry
KW - Methane
KW - Petroleum systems
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U2 - 10.1016/j.orggeochem.2017.07.016
DO - 10.1016/j.orggeochem.2017.07.016
M3 - Review article
AN - SCOPUS:85034039806
SN - 0146-6380
VL - 113
SP - 262
EP - 282
JO - Organic Geochemistry
JF - Organic Geochemistry
ER -