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Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation

Brounce, Maryjo and Stolper, Edward and Eiler, John (2017) Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation. Proceedings of the National Academy of Sciences of the United States of America . ISSN 0027-8424. (In Press) http://resolver.caltech.edu/CaltechAUTHORS:20170810-123533647

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Abstract

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO_2). Volcanic degassing is a source of these elements to Earth’s surface; therefore, variations in mantle fO_2 may influence the fO2 at Earth’s surface. However, degassing can impact magmatic fO_2 before or during eruption, potentially obscuring relationships between the fO_2 of the solid Earth and of emitted gases and their impact on surface fO_2. We show that low-pressure degassing resulted in reduction of the fO_2 of Mauna Kea magmas by more than an order of magnitude. The least degassed magmas from Mauna Kea are more oxidized than midocean ridge basalt (MORB) magmas, suggesting that the upper mantle sources of Hawaiian magmas have higher fO_2 than MORB sources. One explanation for this difference is recycling of material from the oxidized surface to the deep mantle, which is then returned to the surface as a component of buoyant plumes. It has been proposed that a decreasing pressure of volcanic eruptions led to the oxygenation of the atmosphere. Extension of our findings via modeling of degassing trends suggests that a decrease in eruption pressure would not produce this effect. If degassing of basalts were responsible for the rise in oxygen, it requires that Archean magmas had at least two orders of magnitude lower fO_2 than modern magmas. Estimates of fO_2 of Archean magmas are not this low, arguing for alternative explanations for the oxygenation of the atmosphere.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1073/pnas.1619527114DOIArticle
http://www.pnas.org/content/early/2017/08/01/1619527114PublisherArticle
http://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1619527114/-/DCSupplementalPublisherSupporting Information
ORCID:
AuthorORCID
Stolper, Edward0000-0001-8008-8804
Additional Information:© 2017 National Academy of Sciences. Edited by Donald J. DePaolo, Lawrence Berkeley National Laboratory, Berkeley, CA, and approved July 7, 2017 (received for review November 28, 2016). Published online before print August 7, 2017. We thank A. Lanzirotti and M. Newville for assistance in beamline operations at Advanced Photon Source Argonne National Laboratory (APS ANL). We thank Woody Fisher and Oliver Shorttle for commenting on early versions of this manuscript. This research used resources of APS, a US Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by ANL under Contract DE-AC02-06CH11357. We thank the Department of Mineral Sciences, Smithsonian Institute, for access to sample NMNH 117393. Author contributions: M.B., E.S., and J.E. designed research; M.B. performed research; M.B. contributed new reagents/analytic tools; M.B., E.S., and J.E. analyzed data; and M.B., E.S., and J.E. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1619527114/-/DCSupplemental.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-06CH11357
Subject Keywords:ocean island basalts; oxygen fugacity; Hawaii volcanism; volcanic degassing; Great Oxidation Event
Record Number:CaltechAUTHORS:20170810-123533647
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170810-123533647
Official Citation:Maryjo Brounce, Edward Stolper, and John Eiler Redox variations in Mauna Kea lavas, the oxygen fugacity of the Hawaiian plume, and the role of volcanic gases in Earth’s oxygenation PNAS 2017 ; published ahead of print August 7, 2017, doi:10.1073/pnas.1619527114
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80139
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Aug 2017 20:02
Last Modified:10 Aug 2017 20:02

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