CaltechAUTHORS
  A Caltech Library Service

Combined ^(13)C–D and D–D clumping in methane: Methods and preliminary results

Stolper, D. A. and Sessions, A. L. and Ferreira, A. A. and Santos Neto, E. V. and Schimmelmann, A. and Shusta, S. S. and Valentine, D. L. and Eiler, J. M. (2014) Combined ^(13)C–D and D–D clumping in methane: Methods and preliminary results. Geochimica et Cosmochimica Acta, 126 . pp. 169-191. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20140211-095212681

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20140211-095212681

Abstract

The stable isotopic composition of methane (e.g., δD and δ^(13)C values) is often used as a tracer for its sources and sinks. Conventional δD and δ^(13)C measurements represent the average isotope ratios of all ten isotopologues of methane, though they are effectively controlled by the relative abundances of the three most abundant species: (^12)CH_4, (^13)CH_4, and (^12)CH_3D. The precise relative abundances of the other seven isotopologues remains largely unexplored because these species contain multiple rare isotopes and are thus rare themselves. These multiply substituted (or ‘clumped’) isotopologues each have their own distinctive chemical and physical properties, which could provide additional constraints on the geochemistry of methane. This work focuses on quantifying the abundances of two rare isotopologues, (^13)CH_3D and (^12)CH_2D_2, of methane in order to assess their utility as a window into methane’s geochemistry. Specifically, we seek to assess whether clumped isotope distributions might be useful to quantify the temperature at which methane formed and/or equilibrated. To this end, we report the first highly precise combined measurements of the relative abundances of (^13)CH_3D and (^12)CH_2D_2 at natural abundances (i.e., unlabeled) via the high-resolution magnetic-sector mass spectrometry of intact methane. We calibrate the use of these measurements as a geothermometer using both theory and experiment, and apply this geothermometer to representative natural samples. The method yields accurate average (i.e., bulk) isotopic ratios based on comparison with conventional techniques. We demonstrate the accuracy and precision of measurements of (^13)CH_3D and (^12)CH_2D_2 through analyses of methane driven to high temperature (> 200 °C) equilibrium in the laboratory. Application of this thermometer to natural samples yields apparent temperatures consistent with their known formation environments and appears to distinguish between biogenic and thermogenic methane.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.gca.2013.10.045DOIArticle
http://www.sciencedirect.com/science/article/pii/S0016703713006170PublisherArticle
ORCID:
AuthorORCID
Stolper, D. A.0000-0003-3299-3177
Sessions, A. L.0000-0001-6120-2763
Other Contributors:
ContributionOther Contributors NameIdentifierPersonID (may be blank)
EditorFarquhar, JamesFarquhar-JUNSPECIFIED
Additional Information:© 2013 Elsevier Ltd. Received 28 June 2013; accepted in revised form 29 October 2013; available online 15 November 2013. DAS was funded by an NSF graduate research fellowship. JME and ALS were funded by Petrobras, the NSF-EAR Instruments and Facilities program, and the California Institute of Technology. AS was funded by the U.S. Department of Energy, Basic Energy Sciences, Grant No. DE-FG02-11ER16246. DLV and SSS received support from the NSF (OCE-1155855 and EAR-0950600). We would like to thank Y. Tang (PEERI) for allowing us to make measurements in his lab. We would additionally like to thank John Hayes and one anonymous reviewer for helpful comments on the manuscript.
Funders:
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
CaltechUNSPECIFIED
Department of Energy (DOE)DE-FG02-11ER16246
NSFOCE-1155855
NSFEAR-0950600
PetrobrasUNSPECIFIED
Record Number:CaltechAUTHORS:20140211-095212681
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140211-095212681
Official Citation:Stolper, D. A., Sessions, A. L., Ferreira, A. A., Santos Neto, E. V., Schimmelmann, A., Shusta, S. S., . . . Eiler, J. M. (2014). Combined 13C–D and D–D clumping in methane: Methods and preliminary results. Geochimica et Cosmochimica Acta, 126(0), 169-191. doi: http://dx.doi.org/10.1016/j.gca.2013.10.045
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43771
Collection:CaltechAUTHORS
Deposited By: Aucoeur Ngo
Deposited On:11 Feb 2014 18:19
Last Modified:13 Dec 2016 23:22

Repository Staff Only: item control page