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Mantle cooling causes more reducing volcanic gases and gradual reduction of the atmosphere

S. Kadoya1,

1Department of Earth and Space Sciences / cross-campus Astrobiology Program, University of Washington, Box 351310, Seattle, WA 98195-1310, USA

D.C. Catling1,

1Department of Earth and Space Sciences / cross-campus Astrobiology Program, University of Washington, Box 351310, Seattle, WA 98195-1310, USA

R.W. Nicklas3,

3Geoscience Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093, USA

I.S. Puchtel2,

2Department of Geology, University of Maryland, College Park, MD 20742, USA

A.D. Anbar4

4School of Earth and Space Exploration and School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA

Affiliations  |  Corresponding Author  |  Cite as  |  Funding information

Kadoya, S., Catling, D.C., Nicklas, R.W., Puchtel, I.S., Anbar, A.D. (2020) Mantle cooling causes more reducing volcanic gases and gradual reduction of the atmosphere. Geochem. Persp. Let. 13, 25–29.

NSF Frontiers in Earth System Dynamics

Geochemical Perspectives Letters v13  |  doi: 10.7185/geochemlet.2009
Received 11 October 2019  |  Accepted 12 February 2020  |  Published 16 March 2020
Copyright © The Authors

Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0




Figure 1 (a) Oxidation state (ΔQFM) buffering volcanic gas composition, and (b) oxygenation parameter (Koxy), as a function of temperature. Here, we assume a system where gases are redox buffered by the surrounding melt and rocks. ΔQFM2000 represents the oxidation state at 2000 K. By definition, ΔQFM is independent of temperature and equal to ΔQFM2000 in (a) whereas cooling tends to decrease Koxy in (b).
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Figure 2 (a) Oxidation state (ΔQFM), and (b) oxygenation parameter (Koxy), as a function of temperature. Here, we assume a closed system of gases, and the ΔQFM of the gases at 2000 K is denoted as ΔQFM2000. Cooling changes ΔQFM unlike the melt buffered case (Fig. 1a) and changes Koxy. However, an initial Koxy that exceeds unity remains >1 with cooling, and an initial Koxy that is less than unity remains <1.
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