Robert W. Nicklas, Igor S. Puchtel, Richard D. Ash, Philip M. Piccoli, Eero Hanski, Euan G. Nisbet, Pedro Waterton, D. Graham Pearson, Ariel D. Anbar, Secular mantle oxidation across the Archean-Proterozoic boundary: Evidence from V partitioning in komatiites and picrites, Geochimica et Cosmochimica Acta, Volume 250, 2019, Pages 49-75, ISSN 0016-7037, https://doi.org/10.1016/j.gca.2019.01.037
Secular mantle oxidation across the Archean-Proterozoic boundary : evidence from V partitioning in komatiites and picrites
|Author:||Nicklas, Robert W.1; Puchtel, Igor S.1; Ash, Richard D.1;|
1Department of Geology, University of Maryland, College Park, MD 20742, USA
2Oulu Mining School, University of Oulu, P.O. Box 3000, FI-90014, Finland
3Dept. Earth Sciences, Royal Holloway, Univ. of London, Egham TW20 0EX, United Kingdom
4Earth and Atmospheric Sciences Department, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
5School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
|Online Access:||PDF Full Text (PDF, 1.3 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe201903067340
|Publish Date:|| 2021-02-01
The oxygen fugacities of nine mantle-derived komatiitic and picritic systems ranging in age from 3.55 Ga to modern day were determined using the redox-sensitive partitioning of V between liquidus olivine and komatiitic/picritic melt. The combined set of the oxygen fugacity data for seven systems from this study and the six komatiite systems studied by Nicklas et al. (2018), all of which likely represent large regions of the mantle, defines a well-constrained trend indicating an increase in oxygen fugacity of the lavas of ∼1.3 ΔFMQ log units from 3.48 to 1.87 Ga, and a nearly constant oxygen fugacity from 1.87 Ga to the present. The oxygen fugacity data for the 3.55 Ga Schapenburg komatiite system, the mantle source region of which was previously argued to have been isolated from mantle convection within the first 30 Ma of the Solar System history, plot well above the trend and were not included in the regression. These komatiite’s anomalously high oxygen fugacity data likely reflect preservation of early-formed magma ocean redox heterogeneities until at least the Paleoarchean.
The observed increase in the oxygen fugacity of the studied komatiite and picrite systems of ∼1.3 ΔFMQ log units is shown to be a feature of their mantle source regions and is interpreted to indicate secular oxidation of the mantle between 3.48 and 1.87 Ga. Three mechanisms are considered to account for the observed change in the redox state of the mantle: (1) recycling of altered oceanic crust, (2) venting of oxygen from the core due to inner core crystallization, and (3) convection-driven homogenization of an initially redox-heterogeneous primordial mantle. It is demonstrated that none of the three mechanisms alone can fully explain the observed trend, although mechanism (3) is best supported by the available geochemical data. These new data provide further evidence for mantle involvement in the dramatic increase in the oxygen concentration of the atmosphere leading up to the Great Oxidation Event at ∼2.4 Ga.
Geochimica et cosmochimica acta
|Pages:||49 - 75|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
This study was supported by NSF FESD Type I Grant #1338810 “The Dynamics of Earth System Oxygenation” (lead PI is A.D. Anbar, I.S. Puchtel is a co-PI). This source of support is gratefully acknowledged. Eero Hanski acknowledges support from Academy of Finland Grant #281859.
|Academy of Finland Grant Number:||
281859 (Academy of Finland Funding decision)
© 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/