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Neoproterozoic to early Phanerozoic rise in island arc redox state due to deep ocean oxygenation and increased marine sulfate levels

Stolper, Daniel A. and Bucholz, Claire E. (2019) Neoproterozoic to early Phanerozoic rise in island arc redox state due to deep ocean oxygenation and increased marine sulfate levels. Proceedings of the National Academy of Sciences of the United States of America, 116 (18). pp. 8746-8755. ISSN 0027-8424. https://resolver.caltech.edu/CaltechAUTHORS:20190412-084938417

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Abstract

A rise in atmospheric O_2 levels between 800 and 400 Ma is thought to have oxygenated the deep oceans, ushered in modern biogeochemical cycles, and led to the diversification of animals. Over the same time interval, marine sulfate concentrations are also thought to have increased to near-modern levels. We present compiled data that indicate Phanerozoic island arc igneous rocks are more oxidized (Fe^(3+)/ΣFe ratios are elevated by 0.12) vs. Precambrian equivalents. We propose this elevation is due to increases in deep-ocean O_2 and marine sulfate concentrations between 800 and 400 Ma, which oxidized oceanic crust on the seafloor. Once subducted, this material oxidized the subarc mantle, increasing the redox state of island arc parental melts, and thus igneous island arc rocks. We test this using independently compiled V/Sc ratios, which are also an igneous oxybarometer. Average V/Sc ratios of Phanerozoic island arc rocks are elevated (by +1.1) compared with Precambrian equivalents, consistent with our proposal for an increase in the redox state of the subarc mantle between 800 and 400 Ma based on Fe^(3+)/ΣFe ratios. This work provides evidence that the more oxidized nature of island arc vs. midocean-ridge basalts is related to the subduction of material oxidized at the Earth’s surface to the subarc mantle. It also indicates that the rise of atmospheric O_2 and marine sulfate to near-modern levels by the late Paleozoic influenced not only surface biogeochemical cycles and animal diversification but also influenced the redox state of island arc rocks, which are building blocks of continental crust.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1073/pnas.1821847116DOIArticle
https://www.pnas.org/content/suppl/2019/04/11/1821847116.DCSupplementalPublisherSupporting Information
ORCID:
AuthorORCID
Stolper, Daniel A.0000-0003-3299-3177
Bucholz, Claire E.0000-0001-5332-8278
Additional Information:© 2019 National Academy of Sciences. Published under the PNAS license. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved March 13, 2019 (received for review December 21, 2018). PNAS first published April 11, 2019. We thank E. Cottrell, M. Hirshmann, and E. Stolper for helpful discussions; Z. Brook for help compiling the data; J. Blundy and C. Langmuir for feedback on an earlier draft; and M. Brounce and L. Kump for constructive reviews. Author contributions: D.A.S. and C.E.B. designed research, performed research, analyzed data, and 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.1821847116/-/DCSupplemental.
Subject Keywords:Earth history; island arcs; ocean oxygenation; oxygen fugacity; subduction
Issue or Number:18
Record Number:CaltechAUTHORS:20190412-084938417
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190412-084938417
Official Citation:Neoproterozoic to early Phanerozoic rise in island arc redox state due to deep ocean oxygenation and increased marine sulfate levels. Daniel A. Stolper, Claire E. Bucholz. Proceedings of the National Academy of Sciences Apr 2019, 116 (18) 8746-8755; DOI: 10.1073/pnas.1821847116
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94682
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Apr 2019 15:59
Last Modified:03 Oct 2019 21:06

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