Volcanic emissions and the early Earth atmosphere

Martin, R. S. and Mather, T. A. and Pyle, D. M. (2007) Volcanic emissions and the early Earth atmosphere. Geochimica et Cosmochimica Acta, 71 (15). pp. 3673-3685. ISSN 0016-7037 DOI 10.1016/j.gca.2007.04.035

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Abstract

Despite uncertainties in our understanding of early Earth volcanism and atmospheric composition, thermodynamic modelling is able to offer estimates of the global production of reactive trace species (NO, OH, SO3, Cl, Br and I) from early Earth volcanism, and thereby to shed light on processes which may have been different in Earth’s early atmosphere. Model results show that thermal decomposition of magmatic H2O, CO2 and SO2 in high-T mixtures of magmatic and atmospheric gases (at T > 1400 °C) generate high levels of reactive trace gas species. Production of these reactive trace species is insensitive to atmospheric CO2 in mixtures where the atmospheric gas is the minor component and will hence continue during periods of low atmospheric CO2. Fluxes of NO, OH, Cl, Br and I from early Earth volcanism are predicted to exceed those from modern Earth volcanism as the higher temperature of early Earth emissions compensates for lower levels of O2 in the atmosphere, compared to the modern Earth. Under certain conditions, the volcanic NO flux from early Earth volcanism is found to be comparable to other sources of reactive N such as lightning NO and photochemical HCN. This is one possible source of fixed nitrogen which may alleviate any postulated Archean nitrogen crisis. Our thermodynamic model reveals that production of SO3 (a potential precursor for near-source volcanic sulphate and hence ‘primary’ volcanic aerosol) is likely to be significantly lower from early Earth volcanism. Uncertainty in the pathway to near-source sulphate in modern volcanism (i.e., the reaction of SO3 with water or direct emission) introduces a large uncertainty into the production rate of near-source volcanic sulphate on the early Eart

Item Type:	Article
Uncontrolled Keywords:	08AREP 2007 P IA54
Subjects:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions:	05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title:	Geochimica et Cosmochimica Acta
Volume:	71
Page Range:	pp. 3673-3685
Identification Number:	10.1016/j.gca.2007.04.035
Depositing User:	Sarah Humbert
Date Deposited:	16 Feb 2009 13:03
Last Modified:	23 Jul 2013 10:07
URI:	http://eprints.esc.cam.ac.uk/id/eprint/511

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