Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 2017 | Supplemental Material
Journal Article Open

Methane Clumped Isotopes: Progress and Potential for a New Isotopic Tracer

Abstract

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.

Additional Information

© 2017 Elsevier Ltd. Received 26 June 2017, Revised 11 July 2017, Accepted 22 July 2017, Available online 16 August 2017. 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.

Attached Files

Supplemental Material - 1-s2.0-S0146638017303479-mmc1.pdf

Files

1-s2.0-S0146638017303479-mmc1.pdf
Files (169.1 kB)
Name Size Download all
md5:b7622f914aa62f6444f8a1c1e1487332
169.1 kB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 17, 2023