Outer Earth volatile reservoir

Kramers (2003) calculated major and minor (noble gas) volatile element abundance patterns in the Outer Earth Reservoir (the atmosphere, hydrosphere, oceanic and continental crust, and recycled components in MORB-source mantle). These are presented, normalized to solar abundances, together with data for chondrites in Fig. 5.6. The following observations can be made ... 

FIGURE 5.6 Major volatile element and noble gas abundances in the outer Earth reservoir of Kramers (2003) and in carbonaceous chondrites relative to Al and solar abundances. The data show that apart from xenon the Earth and chondritic meteorites have similar element distribution patterns and that both are strongly depleted in the noble gases and in H, C, and N relative to solar abundances. 

After the accretionary event in which the Earth acquired its volatiles, other processes took place which caused it to lose them. There are two lines of evidence which tell us about the early Earth s loss of volatiles. The first comes from a comparison between the volatile concentrations in the outer Earth and those of carbonaceous chondrite meteorites (the most primitive and most volatile-rich of all the meteorite groups). It is clear from Fig. 5.6 that the Outer Earth Reservoir has two to three orders of magnitude less volatiles than carbonaceous chondrites. In addition it is evident that the lighter major elements are more depleted than the heavy ones. 

FIGURE 5.8 The Al-normalized concentrations of the major volatile elements (H, C, N, Cl, Br and I) and the noble gases (Ne, Ar, Kr, Xe) in the outer Earth reservoirs relative to Al-normalized concentrations in carbonaceous chondrites (after Kramers, 2003). 

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