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^2H/^1H ratio of hopanes, tricyclic and tetracyclic terpanes in oils and source rocks from the Potiguar Basin, Brazil

Ferreira, Alexandre A. and Santos Neto, Eugenio V. and Sessions, Alex L. and Schimmelmann, Arndt and Aquino Neto, Francisco R. (2012) ^2H/^1H ratio of hopanes, tricyclic and tetracyclic terpanes in oils and source rocks from the Potiguar Basin, Brazil. Organic Geochemistry, 51 . pp. 13-16. ISSN 0146-6380. doi:10.1016/j.orggeochem.2012.07.007. https://resolver.caltech.edu/CaltechAUTHORS:20121116-131754394

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Abstract

We report the hydrogen isotope ratio ^2H/^1H (expressed as δ^2H values) of 8 selected hopanes, tricyclic and tetracyclic terpanes from oils and source rocks in the Potiguar Basin, and of associated formation water. Hopanes ranged in δ^2H value from −79‰ to −142‰, whereas tri- and tetracyclic terpanes (TTTs) ranged from −137‰ to −225‰. Formation water δ^2H values ranged from −23‰ to −32‰. The most significant pattern in the data is the systematic ^2H enrichment of hopanes relative to TTTs, by an average of 45‰ in oils and 78‰ in source rock extracts. The hopanes appear close to hydrogen isotopic equilibrium with coeval formation water, whereas TTTs are significantly more ^2H depleted. Given the similarities in structure between the two compound classes, it is unlikely that hopanes would be exchanged completely while the others would not. More likely, both classes have undergone a limited extent of exchange, but with the hopanes being biosynthesized with δ^2H values closer to equilibrium. Our data suggest that at least some primary environmental and/or biotic information can be retained in the δ^2H values of biomarkers in oils and extracts, and is not completely obscured by hydrogen exchange.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.orggeochem.2012.07.007DOIArticle
http://www.sciencedirect.com/science/article/pii/S0146638012001519PublisherArticle
ORCID:
AuthorORCID
Sessions, Alex L.0000-0001-6120-2763
Schimmelmann, Arndt0000-0003-4648-5253
Additional Information:© 2012 Elsevier Ltd. Received 16 February 2012. Received in revised form 21 July 2012. Accepted 22 July 2012. Available online 1 August 2012. Associate Editor—K. Grice. We thank L. Zhang for assistance with compound-specific ^2H measurements, P. Velloso and R. Marins for generation and improvements of the images, and PETROBRAS for permission to publish the results of this investigation. The manuscript greatly benefited from constructive reviews by C. Eiserbeck and D. Dawson. A.L.S. was supported by NSF Grant EAR-0645502 and A.S. was funded by U.S. Department of Energy, Basic Energy Research Grant DEFG02-00ER15032.
Funders:
Funding AgencyGrant Number
NSFEAR-0645502
Department of Energy (DOE)DE-FG02-00ER15032
DOI:10.1016/j.orggeochem.2012.07.007
Record Number:CaltechAUTHORS:20121116-131754394
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121116-131754394
Official Citation:Alexandre A. Ferreira, Eugenio V. Santos Neto, Alex L. Sessions, Arndt Schimmelmann, Francisco R. Aquino Neto, 2H/1H ratio of hopanes, tricyclic and tetracyclic terpanes in oils and source rocks from the Potiguar Basin, Brazil, Organic Geochemistry, Volume 51, October 2012, Pages 13-16, ISSN 0146-6380, 10.1016/j.orggeochem.2012.07.007. (http://www.sciencedirect.com/science/article/pii/S0146638012001519)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35518
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 Nov 2012 22:43
Last Modified:09 Nov 2021 23:15

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