Constraining the Volume of Earth's Early Oceans With a Temperature‐Dependent Mantle Water Storage Capacity Model

Abstract

Water was delivered to the Earth during accretion or soon afterward (Morbidelli et al., 2000). This was followed by vigorous outgassing of possibly oxidized volcanogenic gases, including H 2 O (Hirschmann, 2012), from the early Earth's mantle, which may have led to the formation of primordial oceans (Elkins-Tanton, 2011). Sometime after the onset of plate tectonics, mantle rehydration by subduction (Iwamori, 2007; Rüpke et al., 2004; van Keken et al., 2011) began to change the relative water contents of the surface and internal reservoirs. Extensively preserved eustatic sea-level records indicate that the continental freeboard has been approximately constant throughout the Phanerozoic (541 Ma to the present) (Miller et al., 2005). However, the subaqueous and subaerial proportions of the Earth's surface may have been quite different before the Phanerozoic, especially in the early Archean, approximately from the Eoarchean to the Paleoarchean (4-3.2 Ga). Though they are sparse, isotopic records from the early Archean may be used to indirectly constrain the size of the early

Hydrous silicate melts and the deep mantle H2O cycle

“…Fig. 7d shows a case where the initial mantle H 2 O content is set to zero, mimicking efficient degassing of an Hadean magma ocean and low solubility of H 2 O in crystallizing phases at very high temperatures as the magma ocean solidifies (Dong et al, 2021). In this model the H 2 O content of all reservoirs increases rapidly once subduction begins.…”

Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres

“…However, we always keep in mind that there are several alternative (though less popular) hypotheses on where and how life could have originated on Earth. For example, recent work suggests that the early Earth (3-4 Gyr ago) was likely completely covered by a global water ocean [98]. If correct, it becomes difficult to conceive how the classical view of the wet-dry cycles could operate in a global-ocean environment, without dry land.…”

An evolutionary system of mineralogy, Part VI: Earth’s earliest Hadean crust (>4370 Ma)

“…We conclude that by 4.37 Ga, lakes and oceans may have covered a significant fraction of Earth's surface (Wilde et al 2001;Elkins-Tanton 2011;Dong et al 2021), while the shallow subsurface experienced significant hydrothermal circulation (Heinrich and Henley 1989;Pirajno 2009). In the following sections we consider more than 150 plausible minerals that may have formed through fluid-rock interactions prior to 4.37 Ga. chemistry and consequent mineralization may have differed significantly from today.…”

“…The volume and aerial extent of Earth's early oceans are also uncertain. Some researchers point to globe-spanning oceans with perhaps twice today's volume of water, owing to a relatively dry, hot peridotitic mantle prior to subduction-driven cycling of water; with subsequent extensive mantle hydration reduced the amount of surface waters (Jarrard 2003;Korenaga 2008;Korenaga et al 2017;Kurokawa et al 2018;Dong et al 2021;Rosas and Korenaga 2021). If so, then the more voluminous early Hadean oceans would have covered almost all of Earth's surface because of less extreme topography prior to the development of felsic continents and associated orogenesis.…”